An Outline of Histology

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  1. Components of epithelium

  2. Characteristics of epithelium

    1. Many cells with little intercellular substances

    2. Shows polarity-nucleus position and shape, and special locations of organelles and inclusions

    3. Rest on a basement membrane

    4. Avascular

  3. Classification:

Covering epithelium

Gland epithelium

  1. Functions

    1. Form a selective barrier

    2. Protection

    3. Absorption

    4. Excretion

    5. Digestion

    6. Secretion

    7. Sensation

  2. Classification of covering epithelium

A. Cell shape

B. Number of layers

Simple --- cells in a single layer

Stratified --- cells in two or more layers

  1. Simple squamous

Very flattened cells presenting a minimal barrier to the passage of material, e.g. oxygen, through them.

Cytoplasm is very hard to see with LM.

The very similar endothelium and mesothelium, line blood and lymph vessels, and serous cavities, respectively.

  1. Simple cuboidal

Cell height and width are equal

  1. Simple columnar

Cell height exceeds width

Cells have three surfaces and sealed at the top of their sides by encircling junctional complexes.

Cells have three surfaces: free/luminal, lateral and basal; each may have membrane specializations, e.g. cilia at free, desmosomes at lateral, and infoldings at basal surfaces.

  1. Pseudostratified columnar --- ciliated; non ciliated

Nuclei lie at different levels suggesting stratified, but all cells are in contact with the basement membrane.

Two or more cell types are present: short basal, tall columnar

  1. Stratified squamous

Many cells, thick.

Basal most cells are cuboidal or columnar and divide.

Cells above the base become polyhedral and are held on this protective epithelium

Underside of the epithelium is indented by vascular papillae of connective tissue, except in the cornea.

  1. Keratinized stratified squamous

Similar in its basal and middle layers to (5), but the uppermost epithelium has granular cells concerned with forming special, dead cells solidly packed together as a surface keratin layer for greater protection.

  1. Stratified cuboidal

  2. Stratified columnar

Surface cells are cuboidal or columnar in shape, basal most cells are low columnar, and between them are polyhedral cells.

  1. Transitional epithelium

Several cells, thick, the surface cells vary from cuboidal in the relaxed condition to squamous in the distended condition.

Basal layer are cuboidal or low columnar, intermediate layers are polyhedral. Cells of the superficial layer are often binucleate.

  1. Cell adhesion in the epithelial cells membrane

    1. Tight or occluding junction - outer parts of two cells’ membranes are fused together thereby occluding the intercellular cleft.

    2. Adhering junctions - zonula adherens: macula adherens

Filaments of the terminal web in each cells apical cytoplasm fasten to the complex.

Desmosomes are disc-like structure scattered on cells’ surfaces; each is contributed to by membranes of two cells; cytoplasmic tonofilaments converge on and insert into thickened cell membranes.

    1. Hemidesmosome - for better adhesion of the cell membrane to the basal lamina.

    2. Gap junction - where two cells’ membranes come closely together with only a 2-nm gap, and the permeability to ions increases for electrical conductivity (electronic coupling).

    3. Terminal bar (LM) = Junctional complex (EM).

  1. Surface specialization in epithelium

    1. Microvilli - on apical cell surface formed by tube-like evaginations of apical plasma membrane with a core of cytoplasm containing microfilaments of actin.

    2. Stereocilia - as long slender processes of the apical surface that are nonmotile.

    3. Cilia - as fine, hair-like processes of the free apical surface, which are motile.

  2. Basal specializations in epithelium

    1. Basement membrane

    2. Basal membrane infoldings --- formed by infoldings of the basal plasma membrane

  3. Gland epithelium

Unicellular gland --- goblet cell

Multicellular gland

  1. Types of glands

exocrine gland

endocrine gland

11. Classification of the exocrine glands

  1. Shape of the secretory unit - tubular, acinar, tubuloalveolar

  2. Duct system --- Simple --- nonbranching duct

Compound --- duct branched (intercalated, intralobular, interlobular, and lobar duct).

  1. Duct epithelium --- low cuboidal, columnar, pseudostratified columnar, and stratified.

  2. Manner of secretion --- holocrine, apocrine, merocrine.

12. Endocrine gland

  1. Cell arrangement - cords, clumps type, follicles.

  2. Rich of capillaries.

Connective Tissue (CT)


1. Origin: derived from mesenchyme

2. Components: cells + extracellular matrix (intercellular substances)

3. Characteristics:

(1) relative few cells with more extracellular matrix

(2) cells arranged loosely

(3) cells without polarity

(4) rich in blood vessels.

4. Classification:

Loose CT

Regular Dense CT

Dense CT

Irregular Dense CT

CT Proper

Elastic Tissue

Adipose CT

White (Yellow) adipose CT

Brown adipose CT

Mature CT

Reticular CT

Hyaline Cartilage


Elastic Cartilage

Specialized CT



Blood & lymph


Embryonic CT mucous CT

5. Functions: connecting, supporting, defense, nutrition, and repair.

Loose Connective Tissue (areolar tissue)

1. Extracellular matrix

(1) Ground substance:

1) Compositions:

multiadhesive glycoproteins

glycosaminoglycans (GAGs)


a. Multiadhesive glycoproteins: fibronectin, laminin, chondronectin.

b. Glycosaminoglycans (GAGs)

 type of GAGs: hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate, etc.

 characteristics of GAGs: linear polymers of repeating disaccharide units composed of a hexosamine and an uronic acid, intensely hydrophilic.

c. Proteoglycans:

glycosaminoglycans (GAG) + core protein → proteoglycan molecular + link proteins + hyaluronic acid → proteoglycan aggregates

2) Functions: Molecular sieve:

a. Exchange medium b. Reservoir of hormones

c. Resistance to compression d. Gel - like barrier

(2) Tissue fluid:

Equilibrium between formation and absorption


(3) Fibers:

Formed by collagen or elastin

1) Types of collagen: type I、II、III、IV、V etc.

2) Formation of collagen fibril:

Amino acid (e.g. glycine, proline, hydroxyproline, hydroxylysine) → a polypeptide chain × 3→ procollagen molecule → → tropocollagen molecule → fibril

64-nm periodicity transverse striation

3) Classification:

a. Collagen fibers: “white” fibers

 Components: type I collagen

collagen fibrils → collagen fibers → collagen bundles

 Characteristics: having great tensile strength and resistance to stretching

b. Reticular fibers: argyrophilic fibers

 Components: type III collagen

 Characteristics: stained black by silver salts impregnation; PAS-positive

c. Elastic fibers: “yellow fibers”

 Components: elastin core + microfibrils sheath

 Characteristics: high elasticity

2. Cells

Resident cell population (permanent residents)

Wandering or transient cell population

(1) Fibroblasts:

1) Morphology:



Fibroblasts ↔ Fibrocytes

2) Function: synthesis of fibers and ground substances

(2) Macrophages:

1) Origin:

2) Morphology:



3) Functions:

a. Phagocytosis:

 Amoeboid mobility: chemotactic factors

 Recognition and binding antigens

 Ingestion: forming phagosome

 Digestion: proteolytic enzymes

b. Secretion:

c. Participating and regulating immunological reaction:

Antigen-presenting cell

4) Mononuclear phagocyte system:

a. Monocytes in the blood

b. Macrophages in the CT

c. Kupffer's cells in the liver

d. Osteoclasts in the bone

e. Microglia in the CNS

f. Langhans cells in the skin

g. Dendritic cell in the LN

h. Alveolar macrophages in the lung

i. Epithelioid cells & Multinuclear giant cells

(3) Plasma cells:

1) Origin:

2) Morphology:

LM: cartwheel or clock-face nucleus


3) Function: synthesis of antibody (Ab)

(4) Mast cells:

1) Morphology:

LM: metachromasia granules


2) Function:

Storage of chemical mediators of the inflammatory response, including: heparin, histamine, eosinophil chemotactic factor of anaphylaxis (ECF-A).


Mediating the allergic reactions.

(5) Adipose cells (adipocytes, fat cells):

1) Origin:

2) Morphology:

a. Unilocular adipocytes: one large fat vacuole, “signet ring cells”

b. Multilocular adipocytes: many small fat vacuoles and mitochondria

3) Function:

a. Unilocular adipocytes: energy storage, insulation and cushioning of vital organs.

b. Multilocular adipocytes: a source of heat.

(6) Leukocytes:

(7) Undifferentiated mesenchymal cells

Dense Connective Tissue

1. Regular Dense CT

2. Irregular Dense CT

3. Elastic Tissue

Adipose Connective Tissue

1. White adipose CT

2. Brown adipose CT

Reticular Tissue

Reticular cells + reticular fibers + ground substance

Constituting the architectural framework of the lymphatic and hemopoietic organs

Embryonic Connective Tissue

1. Mesenchyme

2. Mucous Connective Tissue

Umbilical cord

Cartilage and Bone

I. Cartilage

1. Structure of cartilage

1) Perichondrium dense C.T.

outer fibrous layer

inner cellular layer

2) Cartilage tissue

(1) Chondrocyte

young ~ : elliptic, singly mature ~ : round isogenous group





cartilage capsule

(2) Cartilage matrix

fibers: type II collagen fibrils / elastic fibers / type I collagen fibers

ground substance: (GAG rich)

proteoglycans aggregates: chondroitin sulfate, keratan sulfate

glycoprotein: chondronectin

rich in water

3) Properties

avascular, no lymphatic vessels or nerves

nourished by diffusion

2. Types of Cartilage

1) Hyaline cartilage

(1) Location

(2) Structure

perichondrium (except articular cartilage)


cartilage matrix: type II collagen fibrils

2) Elastic cartilage

(1) Location: external ear, auditory tube, epiglottis et al.

(2) Structure



cartilage matrix : elastic fiber + type II collagen fibrils

3) Fibrocartilage transitional type

(1) Location: intervertebral disks, symphysis pubis, et al.

(2) Structure

perichondrium: no

chondrocytes: small, often arrange in long row

cartilage matrix: type I collagen fibers, less ground substance
3. Histogenesis and growth of cartilage

1) Histogenesis

mesenchymal cells  chondroblasts + perichondrium

2) Growth

(1) Interstitial (endogenous) growth from inside

(2) appositional (perichondrium) growth from outside

II. Bone


Preparations: ground bone, decalcified bone

1. Structure of bone tissue

1) Bone matrix

(1) Organic matrix: (35%)

fibers: type I collagen fibers

proteoglycan aggregates

structural glycoproteins: osteocalcin, osteonectin, et al.

(2) Inorganic salts: (65%) hydroxyapatite crystals

osteoid → calcified → bone matrix

2) Bone cell

  1. Osteoprogenitor cell: stem cell


  1. Osteoblast: bone- forming cell

LM: single layer, polygonal shape, basophilic cytoplasm

EM: rER, Golgi complex, matrix vesicle

(3) Osteocytes

lacunae canaliculi

LM: slender processes


Function: maintain the bone matrix; maintain the homeostasis of blood Ca2+

(4) Osteoclast: bone reabsorbing cell

Howship’s lacunae

LM: multinucleated large cell, acidophilic cytoplasm

EM: ruffled border, clear zone, lysosome, mitochondria, endocytic vesicles
2. Architecture of Long Bone

1) Compact bone

(1) Outer and inner circumferential lamellae

(2) Haversian systems (osteon): cylindrical unit, supporting

Haversian canal + concentric lamellae + osteocytes

cementing substance

(3) Interstitial lamellae

(4) Volkmann’s canal (perforating canal)

2) Spongy (cancellous) bone

trabeculae: parallel lamellae + osteocytes

3) Periosteum & endosteum

(1) Periosteum

outer fibrous layer inner osteogenic layer

Sharpey’s fibers (perforating fiber)

(2) Endosteum

osteogenic cells

3. Histogenesis of bone

1) Intramembranous ossification

  • mesenchymal cell → osteoprogenitor cell → osteoblast→ osteocyte

  • mesenchymal sheet → primary ossification center → primary spongy bone → primary compact bone

  • mesenchymal sheet → periosteum, endosteum, bone marrow

2) Endochondral ossification

  1. Cartilage model formation

mesenchymal cell → chondrocyte & perichondrium

cartilage growth

  1. Bone collar formation and Cartilage degeneration

perichondrium → vascularization → periosteum

osteoprogenitor cell → osteoblast → osteocyte

bone collar

chondrocyte hypertrophied, calcified, degenerated

(3) Primary ossification center formation

periosteal bud (blood vessels, osteoprogenitor cells, osteoclasts)

primary ossification center

marrow cavity

(4) Secondary ossification center formation

Epiphyseal plate zone of epiphyseal cartilage

A. zone of reserve cartilage

B. zone of proliferation

C. zone of hypertrophy and calcification

D. zone of ossification

(5) Remodeling

primary bone tissue (woven bone)

secondary bone tissue (lamellar bone)

Blood and Hemopoiesis


male: 4.1-6 × 1012 /L


female: 3.9-5.5× 1012 /L

Neutrophils 60-70%

Granular ~ Eosinophils 2-4%

Formed element

~ 45%


6-10× 109 /L

Basophils <1%

Lymphocytes 20-30%

Agranular ~

Monocytes 3-8%


(100-300)×109 /L

Plasma ~ 55%

Hematocrit: 40-50% in man & 35-45% in woman
I. Plasma: yellowish & translucent

1. Compositions:

Plasma proteins: albumin, ,,-globulin, clotting protein (prothrombin, fibrinogen, etc.), complement protein (C1-C9), lipoproteins (chylomicrons, VLDL, LDL, HDL).

2. Functions: transportation, regulation & defense.

3. Serum:
II. Formed element:

Smear and sectioned slide

Wright & Giemsa stain (azures)

1. Erythrocytes (Red Blood Cell, RBC)

(1) Structure: “Histologic ruler”

Biconcave disc, d » 7-8m, anucleate, no organelles, acidophilic, rich in hemoglobin & deformable membrane.

Erythrocyte rouleaux (stacked coins)

1) Hemoglobin (Hb): globin + iron-containing heme

male: 120-150g/L & female: 105-135g/L, HbA & HbF

Oxyhemoglobin ↔ carbaminohemoglobin


2) Cell membrane: flexible & deformable

a. Peripheral membrane proteins: spectrin, actin, and ankyrin etc. serving as a membrane skeleton.

b. Integral membrane proteins: Na+-K+ pump, Ca++ pump, and glucose transport protein, band 3 protein, and glycophorins etc.

  • Blood group, transfusion and hemolytic transfusion reaction

ABO group & Rh group:

(2) Function: Transporting O2 and CO2

(3) Change of RBC

1) Physical adaptation:

2) Pathological changes:

d > 9m, macrocytes; d < 6m, microcytes; anisocytosis:

Anemia: RBC < 3 × 1012 /L, Hb < 100g/L

Iron-deficiency ~, Sickle cell ~, Mediterranean ~ etc

(4) Osmotic equilibrium between RBC and plasma

Hemolysis: blood shadow or blood ghost

Isoosmotic solution:

Hyperosmotic solution:

Hypoosmotic solution:

(5) Reticulocyte: 0.5~1.5% of RBC

Anucleate, contain some organelles, e.g.: ribosomal RNA (rRNA), and demonstrated by brilliant cresyl blue methods

(6) Life span: about 120days

2. Leukocytes (White Blood Cell, WBC)

Inactive WBC in circulating blood → Active WBC in connective tissue


(1) Introduction:

1) Granular leukocytes

a. Azurophilic granules: staining purple, lysosomes, containing acid phosphatase, myeloperoxidase, etc.

b. Specific granules:

c. Types: Neutrophils, Eosinophils & Basophils

2) Agranular leukocytes (mononuclear leukocytes)

a. Azurophilic granules

b. Types: Lymphocytes & Monocytes

3) Life span: variable

(2) Classification:

1) Neutrophils: 12-15m

a. Structure:

 Nucleus: band-form nucleus or lobulated, 2-5 lobes

Sex chromosome: drumstick-like appendage of nucleus in 3% of neutrophils in female in LM

 Specific granules: neutrophilic granules:

Small, barely visible in LM, containing alkaline phosphatase, collagenase and lysozyme etc.

b. Functions:

 Chemotaxis:

 Phagocytosis and destruction of microorganisms, especially bacteria.

Pus & pyocyte

2) Eosinophils: 12-15m

a. Structure:

 Nucleus: bilobed

 Specific granules: eosinophilic granules

Large, staining orange-pink, elongated, crystalline core, refractile, and containing major basic protein, histaminase, myeloperoxidase, etc.

b. Functions:

 Chemotaxis:

 Phagocytosis of Ag-Ab-complexes and destruction of parasites.

3) Basophils: 12-15m

a. Structure:

 Nucleus: lobed, S-shaped, or irregular, often masked by the overlying specific granules

 Specific granules: basophilic granules:

metachromasia, staining blue purple and containing heparin, histamine, and eosinophil chemotactic factor of anaphylaxis (ECF-A).


b. Functions: mediating the allergic reactions.

Anaphylatic shock

4) Lymphocytes:

a. Structure:

 Small lymphocytes: 6-8m, nucleus: cytoplasm ≈ 9:1

Deeply-stained spherical nucleus, sometimes with an indentation, located eccentrically; cytoplasm is basophilic, sky-blue, contains fine azurophilic granules.

 Medium-sized lymphocytes: 9-12m

 Large lymphocytes: 13-18m

b. Classification and functions:

 B-Lymphocytes: 20-30%, responsible for antibody - mediated

(humoral) immunity.

 T-Lymphocytes: 70-80%, responsible for cell - mediated immunity.

 Natural killer cells:

5) Monocytes: 12-20m

a. Structure: oval, kidney- or horseshoe - shaped nucleus, eccentric position; cytoplasm is basophilic, bluish-gray, and contains fine azurophilic granules.

b. Functions: precursor cells of the mononuclear phagocyte system

3. Platelets: (Thrombocytes) 2-4m

(1) Structure: often in clumps

1) non-nucleate, biconvex round or ovoid discs.

2) Hyalomere: peripheral clear zone

Dense tubular system, open canalicular system & microtubules

3) Granulomere: central darker zone

, ,  granules

(2) Functions: promote blood clotting & controlling hemorrhage

(3) Origin:

Protoplasmic discs derived from bone marrow megakarocytes.

(4) Life span: ~ 10 days.

Thrombocytopenic purpura
Hemopoiesis (Blood Cell Formation)

I. Hemopoietic Organ:

  1. Mesoblastic phase: yolk sac 3w

  2. Hepatic phase: 6w - end of gestation

  3. Splenic phase: 4m - end of gestation

  4. Myeloid phase: bone marrow > 6m

Red Bone Marrow ↔ Yellow Bone Marrow

Structure of Red Bone Marrow

(1) Stroma: reticular tissue

(2) Hemopoietic cord: hemopoietic cells & macrophages

  • Pluripotential hemopoietic stem cells  progenitor cells (committed stem cells) [Colony-forming cells (CFC) or colony-forming units (CFU)]  precursor cells (blasts)

  • Growth Factors, colony-stimulating factors (CSF) or hematopoietins, e.g.: Erythropoietin (EPO), G-CSF, GM-CSF etc.

(3) Sinusoids:

Bone marrow aspiration

II. Erythropoiesis ~7d

Proerythroblast  basophilic erythroblast  polychromatophilic erythroblast  orthochromatophlic erythroblast (normoblast)  reticulocyte  erythrocyte

  • Major morphological changes:

(1) Cell volume: ¯

(2) Cytoplasm: basophilic ® acidophilic

(3) Nucleus: ¯ disappear; nucleoli: disappear; chromatin condensation

III. Granulopoiesis ~11d Granules

Myeloblast  promyelocyte  myelocyte  metamyelocyte  granulocyte

IV. Thrombopoiesis

Megakaryoblast  promegakaryocyte  megakaryocyte  platelet

Muscle Tissue

I. Introduction

1. Composition

  • Muscle fibers: specialized contractile cells

  • Extracellular matrix

2. Function


3. Classification

skeletal muscle



cardiac muscle



smooth muscle

II. Skeletal Muscle

1. Organization of skeletal muscle




Myotendinous junction

2. Structure of skeletal muscle fiber


muscle fiber = muscle cells, sarcolemma = plasmalemma

sarcoplasm = protoplasm, sarcoplasmic reticulum = sER

1) Morphology

long, cylindrical, multinucleated cell with cross-striation

2) Nuclei

100-1000 nuclei per cell, located peripherally, ovoid & flattened.

3) Sarcoplasm:

(1) Myofibrils: F =1-2 mm

  • long cylindrical filamentous bundles consisting of stacks of sarcomeres

  • A band, I band, Z line, H band, M line

  • sarcomere: functional unit of contraction

1/2 I band + A band + 1/2 I band

  • thin filament

actin (G-actin, F-actin), tropomyosin, troponin (TnT, TnC, TnI)

  • thick filament:

myosin: 2 heavy chains + 4 light chains

rod-like portion

globular head: actin binding sites, ATP binding sites, ATPase activity

  • cross-bridge

  • muscle contraction: sliding filament mechanism

(2) Membrane system

  • transverse (T) tubule system

  • sarcoplasmic Reticulum

  • triad = T tubule + 2 terminal cisternae

at A-I junction

(3) Other components

mitochondria, glycogen, lipid droplet, myoglobin, ribosome
3. Types of skeletal muscle fiber

red fibers (type I fibers), white fibers (type II B fibers), intermediate fibers (type II A fibers)


Red fiber

White fiber

Fiber diameter



Vascular supply






Sarcoplasmic reticulum

not extensive












slow, not easily fatigued, weaker contraction

Fast, easily fatigued, stronger contraction

4. Innervation

motor end-plate (myoneural junction)

Sensitive nerves: muscle spindles

5. Development and regeneration

1) Development: myoblast  myotubes  myocytes

2) Regeneration: satellite cell
III. Cardiac Muscle

  1. Organization of cardiac muscle

  2. Structure of the cardiac muscle fiber

1) Morphology: cross-striated, elongated, branched cell

2) Nuclei: 1 or 2 centrally

3) Sarcoplasm

(1) Myofibrils: thinner, branched

(2) Membrane system

  • T tubule: numerous, larger

  • Sarcoplasmic reticulum: less developed

  • diads: Z disk level

(3) Other components

numerous mitochondria, lipid droplets, glycogen, lipofuscin, et al.

4) Intercalated disk

transverse portion: zonula adherens, desmosomes

lateral portion: gap junction

  1. Types of cardiac muscle cell

  1. Myoendocrine cells: atrial natriuretic factor (atriopeptin)

  2. Impulse-generating & conducting system

  1. Regeneration

IV. Smooth Muscle

  1. Organization

  2. Structure of smooth muscle cell

1) Morphology: nonstriated, fusiform

2) Nucleus: single, centrally

3) Sarcoplasm

(1) Cytoskeleton

dense body and dense patch

intermediate filaments: desmin, vimentin

(2) Myofilament unit

  • thin filaments: actin, tropomyosin, calmodulin, caldesmon

  • thick filaments: myosin

  • thick filaments : thin filaments = 1:12

  • contraction

(3) Membrane system

caveolae, rudimentary SR

(4) Other components (juxtanuclear region)

rER, Golgi complex, ribosome, et al.

  1. Innervation

  • Autonomic nervous system

  • Hormone regulation

  1. Regeneration


Nervous Tissue

The Neuron

I. The structure of the neuron

  1. The Cell body

    1. Cell membrane

    2. Nucleus, Nucleolus

    3. Cytoplasm, Perikaryon

      1. Golgi Apparatus

      2. Mitochondria

      3. Microtubules, 20-26nm diameter

(LM, neurofibril)

      1. Neurofilaments, 8-10nm diameter

      2. Lysosomes

      3. Nissl body (rough ER and free ribosomes)

  1. Dendrites

    1. Nissl body

    2. Purkinje’s 250μm2~27,000μm2

    3. Mitochondria

    4. Microtubules

    5. Neurofilaments

    6. Dendritic spine

  2. Axons

    1. Axon hillock

    2. Collateral branch

    3. Terminal arborization

    4. Axolemma

    5. Axoplasm (few microtubules, mitochondria, neurofilaments)

    6. Axoplasmic flow

II. Classification of the neuron

  1. Multipolar neurons: motor neurons from the spinal cord

  2. Bipolar neurons: olfactory cells

  3. Pseudounipolar neurons: central process, peripheral process, spinal ganglia

III. Synapses Specialized Structures

  1. Types: axodendritic synapse, axosomatic synapse, axoaxonal synapse, dendrodendritic synapse

  2. Boutons terminaux

  3. Structure

    1. Presynaptic element, membrane, neurotransmitters

    2. Synaptic cleft, 15-30nm width

    3. Postsynaptic element, membrane, receptor

    4. Synaptic vesicle

  4. Chemical synapse: neurotransmitter

  5. Electrical synapse: gap junction

Neuroglia Cell


  1. Astrocyte --- fibrous, protoplasmic types

    1. Nucleus: oval, large and less dense than oligodendrocyte nucleus

    2. Stellate projections

    3. Perivascular feet

    4. Comparison



Glial filament

Fibrous Astrocyte

white matter

long, slender, smooth, a few branches


Protoplasmic Astrocyte

gray matter

short, thick, rough many branches


Glial fibrillary acidic protein (GFAP)

  1. Oligodendrocyte

    1. Nucleus: small, dark

    2. Myelin in CNS --- Each oligodendrocyte myelinates many internodes of different axons

  2. Microglia (gray matter)

    1. Nucleus: smaller, dark, elongated shape

    2. Short processes: thorny spines

    3. Engulfing function: mononuclear phagocyte system in nervous tissue

  3. Ependymal cell

    1. Line ventricular system and central canal

    2. Cuboidal, columnar

    3. Apical surface: microvilli, cilia


  1. Schwann cells

    1. Make PNS myelin

    2. One Schwann cell myelinates one internode

  2. Satellite cells

Nerve fibers

I. Myelinated fibers

    1. Myelin sheath



Schmidt - Lanterman’s clefts

Neurolemma - plasma membrane and basement membrane of Schwann cell

    1. Initial Segment

    2. Node of Ranvier

    3. Internode

    4. Schwann cells make PNS myelin

    5. Oligodendrocytes make CNS myelin

II. Unmyelinated fibers

  1. No myelin sheath, No node of Ranvier

  2. Axons are embedded in the cytoplasm of a Schwann cell

Nerve Ending

I. Sensory nerve ending

  1. Free nerve ending

  2. Tactile corpuscle (Meissner’s corpuscle)

  3. Lamellar corpuscle (Pacinian corpuscle)

  4. Muscle spindle - intrafusal muscle fiber

II. Motor nerve ending

  1. Motor end- plate, neuro-muscular junction

  2. Visceral motor nerve ending varicosity


Nerve ganglion: An aggregation of nerve cell bodies outside the central nervous system

  1. Spinal ganglia Pseudounipolar neurons, satellite cell

  2. Cranial ganglia

  3. Autonomic ganglia multipolar neurons

Peripheral Nerve

  1. Endoneurium

  2. Perineurium

  3. Epineurium

The Circulatory System

Blood vascular system + Lymphatic vascular system


heart capillary ↔ tissue fluid ↔ cell


vein lymphatic vascular system

I. Blood vascular system

heart + arteries + capillaries + veins

1. General structure of blood vessels --- 3 concentric layers

(1) Tunica intima

1) Endothelium + basal lamina

  • Weibel-Palade granules (W-P bodies):

especially in the endothelial cells of elastic arteries, rod-shaped, having dense matrix housing parallel tubular elements, containing Von Willebrand’s factor (factor VIII).

2) Subendothelial layer --- loose connective tissue

3) Internal elastic lamina --- a fenestrated sheet of elastin

Myoendothelial junctions

(2) Tunica media

1) Various numbers of smooth muscle cell layers intermingled with fibroelastic C.T.

2) External elastic lamina

(3) Tunica adventitia fibroelastic C.T.

Vasa vasorum:

Lymphatic vessel & innervation

2. Specific structure of blood vessels

(1) Capillaries

1) Composition:

a. Pericytes:

 Morphology: having long processes, basal lamina fusing with that of endothelial cells

 Functions: contractility & participating in regeneration

b. Endothelial cells + basal lamina

Morphology: LM: EM:

2) Ultrastructure and classification of the capillaries

a. Continuous Capillaries

 Morphology: continuous endothelium, tight junctions, continuous basal lamina, pinocytotic vesicles.

 Distribution: muscle, C.T., exocrine gland, lung, CNS, etc.

b. Fenestrated capillaries

 Morphology: fenestrates (pores) with or without diaphragm, continuous basal lamina.

 Distribution: stomach, intestine, endocrine gland, kidney, etc.

c. Discontinuous sinusoidal capillaries (sinusoids)

 Morphology: enlarged diameter, gaps, large fenestrates without diaphragm, discontinuous or absent basal lamina.

 Distribution: liver, spleen, bone marrow, etc.

3) Functions:

a. Permeability exchange vessels

b. Metabolic functions

 Activation angiotensin I  angiotensin II

 Inactivation bradykinin, serotonin, etc.

 Lipolysis lipoproteins

 Production of vasoactive factors e.g., endothelins & NO

c. Antithrombogenic function

4) Microcirculation:

a. Composition:

precapillary sphincters

Arterioles  metarterioles  capillaries  postcapillary venules

Arteriovenous anastomosis

Metarterioles: with a discontinuous smooth muscle layer

b. Functions: blood pressure & blood flow regulation, and thermoregulation in particular areas.

(2) Arteries

1) Arterioles (Peripheral resistance vessels)

Diameter < 0.5 mm (including all 3 layers)

1-2 concentric smooth muscle layers in media, thin adventitia

2) Muscular arteries

a. Small arteries d < 1mm (Peripheral resistance vessels)

b. Medium - sized arteries (Distributing Arteries)

Prominent internal elastic lamina, 3-40 concentric smooth muscle layers in media, external elastic lamina usually visible, adventitia equal in thickness to media

3) Elastic Arteries (Conducting Arteries) yellowish color

Relatively thick intima, 40-70 elastic laminae in media, thin adventitia

4) Specialized arteries and age changes in arteries:


  • Specific receptors:

a. Carotid bodies & aortic bodies: chemoreceptors, sensing O2 and CO2 tension & pH.

b. Carotid sinuses: baroreceptors, sensing blood pressure.

(3) Veins (Capacitance vessels)

Comparing with their corresponding arteries, veins have valves and squashed, larger lumen, thinner wall, and poorly demarcated layers.

1) Venules diameter < 1mm

pericytes in postcapillary venules, discontinuous or no smooth muscle in media


2) Small to medium-sized veins diameter: 1-9mm

2-4 1ayers of smooth muscle cells in media, intermixed with fibroelastic C.T., thicker adventitia with or without some longitudinal arranged smooth muscle cells. One - way valves in veins > 2mm diameter

Venous valves: paired, semilunar folds of the intima

3) Large veins

relatively thin media, thickest adventitia with many longitudinal bundles of smooth muscles.

(4) Heart

1) Tunics:

a. Endocardium

 Endothelial cells + basal lamina

 Subendothelial layer

 Subendocardial layer Branches of Purkinje fibers in it

b. Myocardium

c. Epicardium (Visceral pericardium): CT + mesothelium

Subepicardial layer

Visceral pericardium

2) Fibrous skeleton (cardiac skeleton)

Including annuli fibrosi, the trigona fibrosa & septum membranaceum.

3) Valves Tricuspid, mitral valves & semilunar valves

A central core of dense C.T., lined on both sides by endothelial layers

4) Impulse Conducting System

a. Sinoatrial (SA) node: pacemaker, in subepicardial layer

b. Atrioventricular node (AV), in subendocardial layer

c. AV Bundle of His, in subendocardial layer

Purkinje cell: specialized cardiac muscle cells, one or two nuclei, paler cytoplasm; clear (glycogen storage) area forms “halo” around nuclei, reduced number of myofibrils.
B. Lymphatic Vascular System

1. Lymphatic capillaries

Blind ended vessels, endothelial cells have no fenestrate, no tight junction, and little or no basal lamina.

2. Lymphatic vessels

3. Main lymphatic trunks

Immune System

Lymphoid Tissue

Reticular cell, Reticular fiber

I. Diffuse lymphoid tissue
II. Lymphoid nodule (Lymphoid follicle)

1. Germinal center

2. Aggregated lymph nodule (Peyer’s Patches)

Lymphoid Organ

I. Central lymphoid Organ

  1. Thymus (thymus dependent lymphocyte)

  2. Bursa equivalent - fetal liver, bone marrow

  3. Bursa of Fabricius

II. Peripheral lymphoid organ

  1. Lymph Nodes

  2. The spleen

  3. Tonsils


I. The Structure of the thymus

    1. Capsule, interlobular septum, lobule

    2. Cortex

      1. Thymocyte, large lymphocytes, medium - sized lymphocytes, small lymphocytes

      2. Epithelial - reticular cell

      1. Morphology: large nuclei, many processes, desmosome, tonofilament

      2. Function

        1. microenvironment

        2. support

        3. secretion

    1. Medulla

Thymus corpuscle (Hassall’s corpuscle):

30-150μm in diameter, consisting of concentric layers of epithelial - reticular cells

    1. Blood circulation and blood - thymus barrier

      1. Postcapillary venule

      2. Blood - thymus barrier

        1. Endothelial cell of continuous capillary

        2. Basement membrane of the endothelial cell

        3. Pericapillary space, Macrophages

        4. Basement membrane of the epithelial - reticular cell

        5. Processes of the epithelial - reticular cell

II. Function of the thymus

  1. Cultivating T lymphocytes, P.V.

  2. Secretion of hormone, thymosin

Lymph Nodes

I. The structure of lymph nodes

A. Capsule related structures

1. Capsule

2. Trabecula

3. Afferent lymphatic vessel

4. Hilus

5. Efferent lymphatic vessel

B. Cortex

  1. Lymphoid nodule

    1. Germinal center --- cap, light zone, dark zone

    2. Dendritic cell --- Cytoplasm branches into numerous process

  2. Paracortical zone (Thymus-dependent zone)

    1. Location

    2. Postcapillary venule

      1. Exhibit an unusual endothelial lining consisting of cuboidal cells.

      2. Lymphocytes are capable of traveling into and between the endothelial cells of this vessel

C. Medulla

  1. Medullary cord: mainly consisting of B lymphocytes

  2. Medullary sinus

  1. Lymphoid sinus and lymph circulation

    1. Subcapsular sinuses

Cortical Sinuses

    1. Peritrabecular sinuses

    2. Medullary sinuses

    3. Lymph circulation

II. Recirculation of lymphocyte

  1. Postcapillary venule

  2. Lymphocyte recirculating pool

B, T lymphocyte, 18-30hrs/round
III. Function

  1. Filtering lymph

  2. Immune

The Spleen

I. The Structure of the spleen:

A. Capsule and trabecula

  1. Mesothelium

  2. Some smooth muscle cells

B. White pulp

  1. Periarterial lymphatic sheath

mainly consisting of T lymphocytes, thymus - dependent zone, interdigitating cell

  1. Lymphoid nodule

mainly consisting of B lymphocytes, cap, light zone, dark zone

C. Marginal zone

  1. Many B lymphocytes and macrophages

  2. The path of lymphocytes from blood flow entering lymphoid tissues

  3. Playing a significant role in filtering the blood and launching an immune response

D. Red pulp

  1. Splenic blood sinusoid

      1. They have a dilated, large, irregular lumen

      2. Spaces between lining endothelial cells

      3. Reticular fibers forming barrel hoop - like rings

  1. Splenic cord

Reticular cells and reticular fibers macrophages engulf old RBCs and platelets

    1. Blood circulation


Splenic artery  trabecular artery  central artery  penicillar arterioles  pulp arteriole  sheathed arteriole  arterial capillaries  sinusoid  pulp vein  trabecular vein  splenic vein

III. Function

    1. Filtration of blood: marginal zone, splenic cord, macrophages

    2. Production of blood

    3. Blood storage. 40ml, (splenic cord, splenic blood sinusoid)

    4. Immune. B lymphocyte 55%

T lymphocyte 45%



Palatine Tonsils

  1. Crypts 10-30

  2. Lymphoid nodule

  3. Infiltrated epithelium

Mononuclear Phagocyte System and Reticulo-endothelial System

Promonocytes  monocytes  macrophages

(bone marrow) (blood) (tissues and organs)

The Endocrine System

I. Introduction


endocrine cells, endocrine, paracrine, autocrine, target cells / organs, hormones: steroid hormones & inclusive nitrogen hormones

  1. Ultrastructure of endocrine cells

1) Peptide - secreting cell

EM: rER, Golgi complex, membrane - bound vesicles

2) Steroid-secreting cell

EM: lipid droplets, Mit. (tubular & vesicular cristae), sER

2. Distribution of the endocrine cells

  • dispersed endocrine cells

  • endocrine tissues

  • endocrine glands

3. Characteristics of endocrine gland

  • ductless glands

  • cells arrange in cords, clumps or follicles

  • highly vascularized by fenestrated capillaries (sinusoids)

  • delicate C.T.

II. Pituitary gland (hypophysis)

  1. Embryogenesis

adenohypophysis: oral ectoderm (Rathke’s pouch)

neurohypophysis: neural ectoderm (diencephalon)

  1. Gross structure

pars distalis anterior lobe

adenohypophysis pars tuberalis

pars intermedia

posterior lobe

pars nervosa

neurohypophysis infundibular stem


median eminence

  1. Adenohypophysis

1) Pars distalis

arranged in cords

fenestrated cap.

(1) Chromophils

Stain affinity

Cell type




somatotropic cells

growth hormone

mammotropic cells

prolactin (PRL)


thyrotropic cells

thyrotropin (TSH)


corticotropic cells

corticotropin (ACTH)

gonadotropic cells

follicle stimulating hormone (FSH)

luteinizing hormone (LH)

(2) Chromophobes 50%

degranulated chromophils

undifferentiated cells

follicular cells

2) Pars intermedia

follicles & cords

chromophobes & basophils

3) Pars tuberalis

abundant longitudinal blood vessels

cell arranged in cords

basophils: may secrete gonadotropins

  1. Neurohypophysis

1) Unmyelinated nerve fibers

2) Pituicytes: neuroglial cells

3) fenestrated capillaries

4) Herring bodies

5. Blood supply

hypophyseal portal system

superior hypophyseal A.

primary capillary plexus


portal veins

(pars tuberalis)

secondary capillary plexus

(pars distalis)

inferior hypophyseal A.


(pars nervosa)

hypophyseal veins

6. Hypothalamo - hypophyseal system

  1. the hypothalamus and adenohypophysis

neuroendocrine cells in tuberal nuclei, etc (releasing hormones, RH & releasing inhibiting hormones, RIH  the portal system  the endocrine cells in pars distalis  target cells in other organs

  1. the hypothalamus and neurohypophysis

neuroendocrine cells in supraoptic and paraventricular nuclei

secrete oxytocin & antidiuretic hormone (ADH, vasopressin)

III. Thyroid gland

  1. Gross structure

  1. Microscopic structure

capsule, lobules

fenestrated capillaries, C.T.

1) Thyroid follicles

simple cuboidal epithelium

colloid within the lumen

(1) Follicle cells


Functions: secrete the thyroid hormone (T3 & T4)

(2) Mechanism of synthesis and secretion of T3 & T4

    1. synthesis of thyroglobulin

    2. uptake of iodide & activation

    3. iodination of thyroglobulin

    4. reuptake of colloid stimulated by TSH

    5. digestion of iodinated thyroglobulin

    6. release of T3 & T4

(3) Functions of the thyroid hormone

2) Parafollicular cells

Location: LM:

EM: Functions: secrete calcitonin

IV. Parathyroid glands

  1. Gross structure

  1. Microscopic structure

cells arrange in cords

1) Chief cell


Functions: secrete parathyroid hormone

2) Oxyphil cells

LM: acidophilic EM: many mitochondria

Function is unknown
V. Adrenal (suprarenal) glands

  1. Gross structure

dense collagenous C.T. capsule



  1. Microscopic structure of cortex

1) Cortex

(1) Zona glomerulosa 15%

small cells arranged in rounded or arched cords

secrete mineralocorticoids (aldosterone)

(2) Zona fasciculate 78%

arranged in straight cords

cells contain many lipid droplets

secrete glucocorticoids (cortisol & corticosterone)

(3) Zona reticularis 7%

arranged in anastomosing network

cells contain lipofuscin

secrete androgens, glucocorticoids

2) Medulla

(1) Medullary cells (chromaffin cells):

modified sympathetic postganglionic neurons


Functions: secrete epinephrine & norepinephrine

(2) Ganglion cells

3. Blood supply


16% body weight, total area 1.2-2.0m2

1300 nerve endings / inch2

The Structures of the skin

Average thickness 1 - 4mm, the most thick 1.5mm


          1. The structures


Nonkeratingzing cell- Melanocyte, Langerhan’s cell, Merkel cell

    1. Stratum basale (Stratum germinativum)

(1) Basal cell: intense mitosis

basophilic cytoplasm


(2) Ultrastructure

        1. tonofilament: 10nm, keratin filament

        2. extensive desmosomes on apical and lateral surface

        3. hemidesmosomes basally

        4. numerous ribosomes

    1. Stratum spinosum

(1) Several layers of polygonal to slightly flattened cells

Spinous cells: spiny projections, intercellular bridges

(2) Mitosis observed; involucrin

(3) Ultrastructure

      1. more tonofilaments

      2. desmosomes cover entire surface

      3. first appearance of membrane coating granules, 0.1-0.3μm in diameter, lamellar granules

3. Stratum granulosum

(1) Several layers of flattened cells

(2) Ultrastructure

    1. more membrane coating granules and they release content into intercellular space by exocytosis

    2. appearance of keratohyalin granules, non - membrane limited, basophilic granules

4. Stratum lucidum

(1) Most pronounced in thick skin

(2) Flattened, non - nucleated cells

keratohyalin in cytoplasm

5. Stratum corneum

(1) Terminal differentiated population

(2) Layers of flattened, non-nucleated cells which are totally keratinized (called horny cells)

Their cytoplasm is full of keratin

(3) Ultrastructure

        1. no organelles left

        2. tonofilaments

        3. plasma membrane: extensively thickened

        4. desmosomes

B. Nonkeratingzing cells

  1. Melanocytes

    1. neural crest origin and invade epidermis at 12-14 weeks embryo

    2. unicellular exocrine glands which synthesize and secrete melanin absorbs UV

    3. dopa reaction

    4. ultrastructure

      1. all organelles for synthetic function: abundant ribosomes, prominent Golgi apparatus, lots of rough ER

      2. no desmosomes

      3. no tonofilaments

      4. contain developmental gradient of melanosomes with ultimate maturation to melanin granules

  2. Langerhans cells

(1) very visible with ATPase

gold chloride impregnation

(2) ultrastructure

      1. no desmosomes

      2. no tonofilaments

      3. tennis racquet granules (Birbeck granules)


average thickness 1-2mm

    1. Papillary layer

Dermal papillae abundant capillaries

Meissner’s corpuscle

    1. Reticular layer

Contains vessels, hair follicles, sweat glands, sebaceous glands, nerves, Pacinian corpuscle

Consisting of loose connective tissue and adipose tissue


  1. Hair Shaft - Portion above epidermis

  2. Hair Root - Portion embedded in skin

  3. Hair Bulb - Basal portion of root penetrated by hair papilla rich in capillaries, hair matrix, scattered melanocytes

  4. Hair Follicle - epidermal and connective tissue sheaths around root

    1. Internal root sheath

    2. External root sheath

  5. Glassy Membrane

  6. Arrector pili muscle

Sebaceous Gland

  1. Located in dermis

  2. Acinus composed of two cell types:

    1. Undifferentiated basal cells

Proliferate and differentiate into acinar cells

    1. Acinar cells


Sweat Glands

I. Merocrine sweat glands

  1. Exocytosis

  2. Clear cells: large, acidophilic

  3. Dark cells: small, basophilic

  4. Myoepithelial cells:

Long flat nuclei lying at the base of epithelial cells of the glands just inside the basement membrane

  1. Ducts:

Contain 2-3 layers of cuboidal or low columnar cells
II. Apocrine sweat glands

  1. Secretory part

  2. Ducts

Oral Cavity and Salivary Glands

Oral Cavity

I. Organization
II. General structure of oral mucosa

Stratified squamous epithelium

Lamina propria
III. Tongue

  1. Epithelium

  2. Lamina propria

  3. Skeletal muscle

  4. Lingual papillae

Table 1. Main Features of Lingual Papillae




Taste buds

Filiform ~

elongated conical



Fungiform ~


a few


Circumvallate ~

large circular papillae,

gland of von Ebner



Foliate ~



  1. Taste bud: specialized gustatory structures

taste pore

Type II, taste cells: taste hair, pale staining

Type I, supporting cells: spindle shape, dark staining

basal cells: conical shape, mitotic pool

Salivary Glands

I. Structure: compound tubuloalveolar glands

A. General organization

    1. Stroma: CT, septa, lobules

    2. Parenchyma: secretory alveoli & intralobular ducts

B. Alveoli

Single layer of cuboidal or pyramidal cells

Myoepithelial cells

1. Serous alveoli

    1. basal RER, apical secretory granules

    2. basal junctional complexes

2. Mucous alveoli

(1) flattened basal nuclei, mucigen granules, cytoplasm looks foamy or empty, HE. pale staining

(2) Basal junctional complexes

3. Mixed alveoli: Mixed seromucous alveoli, serous demilune

C. Duct System

1. Intercalated duct:

Squamous or low cuboidal epithelium

myoepithelial cells

2. Striated (secretory) duct


simple columnar cells

the basal cytoplasm membrane infoldings with longitudinally arranged mitochondria

3. Interlobular duct

Pseudostratified columnar epithelium

4. Main duct

Scattered goblet cells, stratified squamous epithelial

II. Differentiation of the three major salivary glands

Table 2. Main Features and Functions of Major Salivary Glands



intercalated ducts

striated ducts




pure serous



amylase, a little mucus



mixed, mostly serous



mucus, a little amylase



mixed, mostly mucous with some serous demilune


a few short

mainly mucus

III. Function

  1. Moistening, lubricating

  2. Digestions

  3. Immunoglobulins - sIgA

Digestive Tract

I. General structure

  1. Mucosa

(1) Epithelium

stratified squamous ~ / simple columnar ~

(2) Lamina propria loose C.T.


gut - associated lymphatic tissue (GALT)

(3) Muscularis mucosae

smooth muscle

inner circular layer, outer longitudinal layer

  1. Submucosa dense C.T.

submucosal (Meissner’s) nerve plexus

lymphoid tissue

submucosal glands

  1. Muscularis

skeletal muscle / smooth muscle

inner circular layer, outer longitudinal layer

myenteric (Auerbach’s) nerve plexus

Enteric Nervous System

  1. Adventitia

serosa:mesothelium + C.T.

fibrosa (adventitia): C.T.

II. Esophagus

  1. Mucosa

1) Nonkeratinized stratified squamous epithelium

2) Lamina propria

esophageal cardiac glands

3) Muscularis mucosae:

single longitudinal layer

  1. Submucosa

esophageal glands: mucus-secreting glands

  1. Muscularis

skeletal muscle / smooth muscle

  1. Fibrosa / serosa

III. Stomach

Rugae, Gastric pits

  1. Mucosa

  1. Simple columnar epithelium

surface mucous cells:

LM: EM: tight junction

Function: secrete insoluble mucus

  1. Lamina propria

Gastric glands

(1) Fundic glands

isthmus, neck, base region

a. Mucous neck cells

Location: LM:

EM: Function:

b. Parietal (oxyntic) cells

Location: LM:

EM: resting phase, active phase

intracellular canaliculus, tubulovesicular system, mitochondria

Function: secret HCl, intrinsic factor

c. Chief (zymogenic) cells

Location: LM:

EM: Functions: secrete pepsinogen

d. Enteroendocrine cells

e. Stem cells

Protective mechanism:

  • mucous-HCO3- barrier

  • tight junction

  • rapid renewal

(2) Cardiac glands

shallow pits, coiled terminal portions, wide lumens

secrete mucus

(3) Pyloric glands:

deep pits, shorter coiled secretory portions

secrete mucus

3) Muscularis mucosae

  1. Submucosa

  2. Muscularis

inner oblique layer, middle circular layer, outer longitudinal layer

pyloric sphincter

4. Serosa
IV. Small Intestine

  1. Special structures

1) Plicae circulares (Kerckring’s valves)

mucosa + submucosa

2) Intestinal villi and intestinal gland (crypts, glands of Lieberkühn)

epithelium + lamina propria

3) Microvilli

cell membrane + microfilaments

2. Mucosa

1) Simple columnar epithelium

(1) Absorptive cells (enterocytes)

Location: LM: striated border

EM: junctional complex, glycocalyx coat

Functions: digestion, absorption, secretion

(2) Goblet cells

(3) Enteroendocrine cells (basal granular cell)

Location: LM: open type, closed type

EM: Function: secrete gut hormone

(4) Paneth’s cells

Location: LM: acidophilic granules

EM: lysozyme, defensin Functions: regulate intestinal flora

(5) Undifferentiated cells stem cell

2) Lamina propria

(1) Central lacteals (lymphatic capillary)

(2) Lymphoid tissue

  • solitary nodules: duodenum, jejunum

  • aggregated nodules (Peyer’s patches ): ileum

  • microfold (M) cells

Location: LM:

EM: Functions:

(3) Muscularis mucosae

3. Submucosa

duodenal (Brunner’s) glands

secrete alkaline mucus, EGF

4. Muscularis

5. Fibrosa / Serosa

V. Large Intestine

1. Cecum and colon

taeniae coli, haustra coli, appendices epiploicae

no villi, crypts packed closely

1) Mucosa

(1) Simple columnar epithelium

absorptive cells, numerous goblet cells, no Paneth’s cell

(2) Lamina propria

rich in lymphoid tissue

(3) Muscularis mucosae

2) Submucosa

3) Muscularis

taeniae coli

4) Fibrosa / Serosa

2. Appendix

small, narrow, and irregular lumen

1) Mucosa

simple columnar epithelium

fewer & shorter intestinal gland

numerous lymphoid nodules

muscularis mucosae incomplete

2) Submucosa

3) Muscularis

4) Serosa

3. Rectum and anal canal

1) Mucosa

simple columnar epithelium / stratified squamous epithelium

muscularis mucosae terminate at anal valves

2) Submucosa

vein plexus

3) Muscularis

internal anal sphincter: inner circular layer, smooth muscle

external anal sphincter: skeletal muscle

4) Fibrosa

Digestive Glands


I. General Structure

  1. Stroma

(1) fibroconnective tissue capsule (of Glisson) collagen fibers, elastic fibers, serosa

(2) lobules

(3) reticular fibers

  1. Parenchyma

II. The liver lobule

Essential structural units

Prismatic polygonal units, 2×1mm

Hepatic plate

Central vein


Hepatic cord

Bile Canaliculus

A. Hepatocyte

  1. General considerations

80%, 20μm in diameter, round central nuclei, eosinophilic cytoplasm, hepatic plate (single layer), 6-8 surfaces

  1. Organelles

(1) Mitochondria 1,000-2,000 / cell, 20%

(2) Lysosomes many, store iron

(3) Peroxisomes 1,000 / cell

Peroxidase catalase

Peroxides free radicals

(4) Golgi complexes 50 / cell

(5) Rough Endoplasmic Reticulum

RER Synthesizes blood albumin, fibrinogen


(6) Smooth Endoplasmic Reticulum

Bile Synthesis

Lipids metabolism

Biological transformation

Detoxification (glucuronyl transferase)

(7) Inclusion

Lipid droplets, Glycogen, Pigment

  1. Three plasma membrane regions


Bile Canaliculi

Cell junction surface: *gap junction

B. Hepatic Sinusoid

  1. Structure

    1. discontinuous endothelial cells

    2. 9-12 μm

    3. micropinocytotic vesicles, a few organelles

    4. Gaps, no diaphragm, no BM, reticular fibers

    5. Macromolecules - chylomicron, VLDL

  2. Kupffer cells

They phagocytize blood cells, iron & debris

C. Space of Disse

Perisinusoidal space


Reticular fibers

Fat-storing cells (store fat and Vitamin A)

D. Bile canaliculi (Silver stain, ATPase)

Tubular space, junction complex

III. Portal areas

Interlobular vein

Interlobular Artery Portal triad

Interlobular bile duct

IV. Biliary Passages

Central peripheral ductules interlobular

Canaliculi (Hering’s canals) bile ducts

Right & Left common common

Hepatic ducts hepatic duct bile duct

Cystic duct

V. Hepatic blood circulation


Artery IA, THA

Liver Central sublobular

Sinusoids vein vein

Portal IV, TPV


Hepatic inferior

vein vena cava

THA: Terminal Hepatic Arteriole TPV: Terminal Portal Venule

VI. Lobulation

      1. The classic lobule

      2. Portal lobule

      3. Liver acinus

VII. Functions

  1. Synthesis and store

  2. Secreting bile

  3. Detoxification

  4. Immune

  5. Hemopoiesis


I. Mucosa

Folds, Simple columnar epithelium, microvilli

II. Muscularis

III. Serosa


I. General Features

Stroma: thin CT capsule, lobules, septa

Parenchyma: exocrine and endocrine cells
II. The Exocrine Portion

A. Acini 11m2

  1. compound tubuloacinar glands

  2. a single layer of pyramidal cells

  3. size of the central lumen

  4. centroacinar cell (flattened, pale staining) cuboidal

  5. typical serous cell: Basal basophilic, apical acidophilic

  6. EM findings: Basal RER

Free ribosome

Longitudinal arranged mitochondria

Zymogen granules (0.6μm)

  1. No myoepithelial cell

  2. trypsin inhibitor, acute pancreatitis

B. Duct

  1. Intercalated duct

  2. Low cuboidal epithelium, centroacinar cell

  3. No striated duct!

  4. Intralobular duct: simple cuboidal epithelium

  5. Interlobular duct: simple columnar epithelium

  6. Main duct: simple high columnar epithelium

goblet cell

enteroendocrine cell

C. Secretion

  1. Merocrine secretion

  2. Regulation

    1. Neural control: vagus nerve 

    2. Hormonal control:

      1. Secretin: bicarbonate and water

      2. Pancreozymin (cholecystokinin)

Pancreatic enzyme

  1. Enzymes:

proteases (e.g. trypsin)




III. The Endocrine Portion

A. Islets of Langerhans: 1.5% of total volume one million islets

Rich fenestrated capillaries  loose reticular fibers


Cell type





A (alpha) ~




blood sugar


B (beta) ~




blood sugar

Diabetes Mellitus

D (delta) ~




inhibition, paracrine (A&B cells)

PP ~


a few

pancreatic polypeptide

Pancreatic juice, gastroenteric motility

The Respiratory System

External respiration & internal respiration

The respiratory system has two parts:

1. Conducting Portion:Nose → → → Terminal Bronchiole


(1) Conducting air

(2) Conditioning air: cleansing, moistening & warming air

(3) Olfaction

(4) Phonation

2. Respiratory Portion: Respiratory Bronchiole → → → Alveoli

Function: Gas exchange

I. Introduction:

Respiratory epithelium: pseudostratified ciliated columnar epithelium

Ciliated column cells

Mucous goblet cells

Basal cells

Brush cells: sensory receptors

Small granule cells: neuroendocrine cells
II. Nasal cavity:

Median nasal septum and superior, middle & inferior conchae

1. Vestibule:


Mucosa Epithelium posterior

Lamina propria:

2. Respiratory Portion:pink



Lamina propria: rich in venous plexuses & mixed glands

Countercurrent heat-exchange system

3. Olfactory Potion:yellowish brown


Epithelium*: pseudostratified columnar epithelium

Lamina propria: serous glands of Bowman

Supporting (Sustentacular) cells:

* Basal cells:

Olfactory (Sensory) cells: bipolar neurons, have olfactory vesicle & olfactory cilia

Paranasal sinuses:

III. Nasopharynx



Lamina propria

IV. Larynx



Lamina propria:

V. Trachea and Bronchi

1. Mucosa


Lamina propria:

2. Submucosa:mixed glands in C.T.


3. Adventitia:“C” shaped or irregular hyaline cartilage and smooth muscles, fibroelastic C.T.
VI. Lungs

1. Bronchial Tree & Pulmonary lobule:

d  1mm d  0.5 mm

Primary Bronchi   Bronchioles  Terminal Bronchioles  Respiratory Bronchioles  Alveolar Ducts  Alveolar Sacs  Alveoli

2. Conducting Portion:

(1) Cavity and wall: 

(2) Epithelium: 

(3) Goblet Cells: 

(4) Glands: 

(5) Cartilage: 

(6) Smooth Muscle: 

(7) Elastic fibers: 

  • Terminal Bronchioles:

Clara cells: dome-shaped apex, secretory granules

Ciliated cells:

3. Respiratory Portion:

Respiratory Bronchioles  Alveolar Ducts  Alveolar Sacs  Alveoli

  • Alveoli Epithelium:

(1) Type I Cells (Squamous Alveolar Cells)

LM: squamous and thin

EM: pinocytotic vesicle, junctional complex


(2) Type II Cells (Great Alveolar Cell)

LM: cuboidal cells, spherical nucleus & foamy cytoplasm

EM: lamellar bodies

Functions:Synthesize and secrete pulmonary surfactant.

Respiratory distress syndrome (hyaline membrane disease)

(3) Blood-Air Barrier:

Surfactant + Type I Alveolar cells + Basal Lamina

Interstitial Space

Capillary's Basal lamina + Endothelium

(4) Alveolar Septum: C.T., rich in capillary and elastic fibers.

(5) Alveolar Pore:

(6) Pulmonary Macrophage: alveolar macrophage

dust cell & heart failure cell

4. Blood Vessels:

Pulmonary Circulation: functional circulation

Bronchial Circulation: nutritional circulation

5. Pleura

The Urinary System


I. Gross structure of the kidney

1. Renal capsule

2. Cortex (outer) dark brown and granular structure

Cortical labyrinths + renal columns (of Bertin)

3. Medulla (inner) pale and radially striated structure

Medullary pyramids + medullary rays

  • Renal lobe: medullary pyramid + renal column

  • Renal lobules: medullary ray + cortical labyrinths

II. Histological structure of the kidney

1. Introduction:

  • Uriniferous tubules:

Nephrons + Collecting tubules

  • Nephrons:

Renal corpuscle + Tubule system

  • Renal corpuscle

Glomerulus + Bowman’s capsule

  • Tubule system

Proximal tubule + Thin limb + Distal tubule

  • Henle’s Loop:

straight portion of the proximal tubule or thick descending limb

the thin limb

the distal straight tubule or thick ascending limb

  • Cortical nephrons

  • Juxtamedullary nephrons

juxtamedullary nephron

cortical nephron


adjacent to medulla















urine concentration


2. Nephrons structural and functional unit

1) Renal corpuscle

(1) Structure:

Glomerulus + Bowman’s capsule + Bowman's space (urinary space)

Vascular pole & Urinary pole

a. Glomerulus (glomerular capillaries; glomerular tuft)

 Fenestrated capillaries

Afferent arteriole  Fenestrated capillaries  Efferent arteriole

 Mesangium

mesangial matrix

intraglomerular mesangial cells


Function: supporting, producing mesangial matrix, phagocytosing, contracting, secreting chemical mediators

b. Bowman’s capsule: double - walled epithelial capsule

 Parietal layer

Visceral layer: modified


Location: LM:

EM: primary processes, secondary processes (pedicels),

filtration slits and slits membrane


(2) Function of renal corpuscle:

Filtration barrier (membrane):

 Structure

  • filtration slits diaphragm

  • Glomerular basement membrane (GBM):

Lamina Rare Interna: fibronectin, proteoglycans (heparin sulfate)

Lamina Densa : type IV collagen, laminin

Lamina Rare Externa : fibronectin, proteoglycans

  • endothelium

 Function : selective filter (physical barrier, charge barrier)

2) Proximal Tubule

Convoluted : in cortical labyrinths (CL)

Straight : in medullary rays (MR) or medullary pyramids (MP)

LM: small, uneven lumen, large acidophilic cuboidal cells, brush border

EM: microvilli, canaliculi, lateral processes, membrane infoldings, large amount of Mit.

Function: reabsorption, secretion

3) Thin limbs

(1) Structure: simple squamous epithelium

(2) Function:

4) Distal tubule

Straight : in MR or MP Convoluted : in CL

LM: shorter, larger lumen, smaller, lighter cells

EM: lack brush border, (Tamm-Harsfal protein)


regulated by Aldosterone & ADH

Proximal tubule

Distal tubule






smaller, irregular

larger, regular

simple cuboidal epithelium



spherical nucleus

large, located centrally

small, located near the lumen


acidophilic, densely staining

acidophilic, lighter staining

brush border



lateral boundary of the cell



basal vertical striation




apical microvilli

long, abundant

short, few

apical canaliculi and vesicle



lateral cell processes



basal cell membrane infoldings


more deeply

elongated mitochondria


more numerous


3. Collecting tubules and ducts

collecting tubules  cortical collecting ducts ® medullary collecting ducts ® papillary ducts

cuboidal.  columnar

1) Structure:

pale-staining cytoplasm, lateral boundary of adjacent cells is clearly visible

2) Function: urine concentration

Regulated by Aldosterone & ADH

4. Intrarenal collecting system

Renal papilla  minor calyx  major calyx  renal pelvis

transitional epithelium


smooth muscle

5. Juxtaglomerular apparatus (Juxtaglomerular complex)

1) Structure

(1) Macula densa

  • Structure:

in the distal convoluted tubule

tall, narrow cells, densely staining nuclei closely packed together

  • Function: sensor of [Na+]

(2) Extraglomerular mesangial cell (polar cushions)

  • Structure:

  • Function: signal transduction

(3) Juxtaglomerular cells:

  • Structure:

modified smooth muscle cells

large cuboidal cells with secretory granules

  • Function:

secretion of renin (vasoconstrictor)

renin angiotensin converting enzyme (ACE)

angiotensinogen angiotensin I angiotensin II

2) Function:

regulate blood pressure
6. The renal interstitium

Interstitium: fibroblast, collagen, proteoglycan

Interstitial cells:

synthesis of prostaglandins, prostacyclin, Erythropoietin (EPO)

7. Vascular supply

vasa recta (arteriolae rectae )

renal A. renal V.

interlobar A. interlobar V.

arcuate A. straight v. arcuate V.

interlobular A. straight a. interlobular V.

peritubular cap. network

afferent arteriole glomerulus efferent arteriole

cap. network in capsule & outer cortex stellate V.
Ureters, Bladder, Urethra

1. Mucosa

1) Epithelium:

Ureters, Bladder: transitional epithelium layers ↑

Urethra: transitional epithelium → stratified squamous epi.

2) Lamina propria

2. Muscularis


upper 2/3: inner longitudinal, outer circular

lower 1/3: inner longitudinal, middle circular and outer longitudinal

Urinary bladder:

thick, helical arrangement

3. Adventitia

The Male Reproductive System

I. Introduction:

II. Testis

Migration of primordal germ cells (PGCs) & Descent of testis


Structure of testis:

1. Testicular capsule:

(1) tunica vaginalis: surrounding the anterolateral aspect of each testis

(2) tunica albuginea mediastinum testis lobuli testis

(3) tunica vasculosa

2. Seminiferous tubule total length is nearly 0.5 km

(1) tunica propria muscle-like myoid cells

(2) basal lamina

(3) seminiferous (or germinal) epithelium stratified epithelium

1) Spermatogenic cells Spermatogenesis & meiosis

a. Spermatogonia: located in basal compartment, mitosis

Dark type A spermatogonia: heterochromatin

Pale type A spermatogonia: euchromatin

Type B spermatogonia:

b. Primary spermatocyte: the largest male germ cells, having chromosome within their nuclei.

c. Secondary spermatocytes: short-lived cells

d. Spermatid

  • Spermiogenesis: round spermatids  elongated spermatids, through shedding of much of their cytoplasm, rearrangement of their organelles, and formation of flagella

 Nucleus becomes condensed and elongated  sperm head

 Golgi apparatus  acrosome (acrosomal cap) (a specialized lysosome)

proacrosomal granules  acrosomal granule within a acrosome vesicle

 Centriole  flagellum

 Mitochondria  mitochondrial sheath

 Microtubuli  manchette (caudal tube)

 Residual bodies are shed, and phagocytosed by Sertoli cell

e. Spermatozoon morphologically mature

 Head

 Neck

 Tail: middle piece, principal piece, end piece

  • Clonal nature of the germ cells

Cytoplasmic bridges & Syncytium of germ cells

  • The cycle of seminiferous epithelium

  • The waves of seminiferous epithelium

2) Sertoli cells

a. Structure:

LM: tall columnar cell; a large, pale, oval or irregular shaped nucleus with a prominent nucleolus; invisible lateral cellular limits.

EM: lateral and apical cell membrane & nucleus with infoldings; many organelles; tight junctions & gap junctions.

  • Blood-testis barrier

  • Basal compartment

  • Adluminal compartment

b. Functions:

 Support, protection and nutrition of developing germ cells.

 Phagocytosis of residual bodies.

 Secretion. e.g.: androgen-binding protein (ABP), anti-müillerian hormone & inhibin, and a fructose - rich medium.

 Formation of blood-testis barrier.

 Regulation the release of spermatozoa

3. Interstitial tissue

(1) Interstitial cell (Leydig cell):

1) Structure:

LM: always in clusters; large, polyhedral cells, acidophilic cytoplasm, central located nucleus.

EM: typical steroid-producing cells, containing large amounts of sER, mitochondria with tubular cristae, and numerous of lipid droplets.

2) Function: secretion of testosterone.

(2) Others: including C.T., nerve, blood & lymphatic vessels.

4. intratesticular genital ducts:

(1) tubuli recti (straight tubules):

Lined by Sertoli cells in proximal half and simple cuboidal epithelium in distal half, supported by loose C.T.

(2) Rete testis:

A system of labyrinthine spaces housed within the mediastinum testis, lined by simple low cuboidal epithelium, supported by vascular C.T.

(3) Ductuli efferentes:

Undulated lumen lined by pseudostratified columnar E., supported by loose C.T., forming the head of the epididymis.

III. Extratesticular genital ducts

1. Ductus epididymidis

Forming the body and tail of the epididymis

Lined by pseudostratified columnar epithelium of uniform height, composed of basal cells and tall principal cells, the latter have many long stereocilia and are actively reabsorptive. Epithelium is supported by loose C.T. and abundant circularly arranged smooth muscles.

2. Ductus deferens (Vas deferens)

A narrow lumen and a thick-walled tube lined by pseudostratified columnar epithelium with stereocilia, and surrounded by 3 layers of smooth muscle: inner and outer longitudinal layers and middle circular layer.


  • Spermatic cord: passes through the inguinal canal, including arteries, veins and ductus deferens.

  • Pampiniform plexus

Countercurrent heat-exchange system

3. Ejaculatory duct

Lined by a simple columnar epithelium, and supported by loose C.T.

4. Urethra

(1) Prostatic urethra Transitional E.

(2) Membranous urethra Pseudostratified columnar E.

(3) Spongious part (bulbous part and pendulous part)

Pseudostratified columnar E.

Glands of Littre
IV. Accessory sex glands

1. Seminal vesicles

Highly coiled tubuli, lined by pseudostratified columnar epithelium, and supported by fibroelastic C.T. and smooth muscles, producing fructose - rich seminal fluid that is energy source for sperm motility.

2. Prostate gland

An collection of branched tubuloalveolar glands, the epithelium ranges from simple cuboidal - columnar to pseudostratified columnar depending on the man's hormonal states, and the glands are embedded within a fibromuscular stroma. Three groups of glands concentrically arranged around the urethra:

(1) Mucosal glands (central zone)

(2) Submucosal glands (transition zone)

(3) Main glands (peripheral zone)

Prostatic concretions (corpora amylacea)

3. Bulbourethral glands

Tubuloalveolar, mucus-secreting glands, lined by a simple cuboidal or columnar epithelium.

V. Penis

1. Structure:

Each of three columns of erectile tissue, which is encircled by tunica albuginea, has large venous sinuses separated by trabeculae.

(1) Corpora cavernosa of the penis: Paired, located dorsally.

Helicine arteries & Intimal cushion

(2) Corpus cavernosum of the urethra (corpus spongiosum): ventrally located, containing penile urethra.

2. Functions:

(1) Urination

(2) Copulation organ

Penile erection: a hemodynamic event

The Female Reproductive System

I. Ovary

1. Oogenesis: miosis of oocyte

oogonia  primary oocytes ① secondary oocytes ② ovum

+ +

polar body polar body

 stopped in prophase of meiosis I, completed before ovulation

 stopped in metaphase of meiosis II, completed when fertilization taken place
2. General structures

1) Ovarian surface epithelium:

simple squamous/cuboidal epithelium

2) Tunica albuginea

dense C.T.

3) Cortex

stroma: C.T., stromal cells, smooth muscle

gamete - producing structures & derivatives

4) Medulla:

loose C.T.

5) Hilum

hilus cells: secrete androgen

3. Structures in cortex

1) Follicular growth

follicle: an oocyte + follicular cells

basement membrane surround the follicles

growing follicles

(1) Primordial follicles

primary oocyte + a single layer of flattened follicular cells

(2) Primary follicles

  • primary oocyte: growth rapidly

  • granulosa cells (follicular cells)

flattened  cuboidal, unilaminar  multilaminar

  • zona pellucida

structures: ZP1, ZP2, ZP3


(3) Secondary follicles

  • follicular cavity (antrum): follicular fluid

  • cumulus oophorus: primary oocyte + corona radiata

  • stratum granulosum

  • basement membrane

  • theca folliculi:

theca interna: theca cells, cap.

theca externa: C.T., smooth muscle cells

  • estrogen produced: theca interna – follicular cell synergism

(4) mature (Graafian) follicles

oocyte: primary  secondary

granulosa layer: proliferation decreased

2) Ovulation after LH surge



secondary oocyte + zona pellucida + corona radiata

3) Corpus luteum

(1) Formation

(2) Structure

granulosa lutein cells: centrally located, numerous, large, acidophilic

theca lutein cells: peripherally located, smaller

(3) Function

secrete progesterone, estrogen

(4) Types

4) Corpus albicans

5) Follicular atresia

oocyte ® degeneration, granulosa cells ® degeneration

happened at any stage of follicle

interstitial glands


4. Function of ovary

  • produce ovum

  • secrete female sexual hormone

II. Oviducts (Uterine Tubes)

  1. Gross structure

Infundibulum, Ampulla, Isthmus, Intramural Portion

  1. Microscopic Structure

1) Mucosa

simple columnar epithelium hormone sensitively

  • ciliated cell

  • secretory cells (peg cells)

lamina propria

2) Muscularis

inner circular layer, outer longitudinal layer

  1. Serosa

longitudinal folds

smooth muscle





intramural portion:

III. Uterus

body (corpus), fundus, cervix

1. Structure of uterine body

1) Perimetrium serosa

2) Myometrium

3 layers: inner longitudinal layer, middle circular layer, outer longitudinal layer

large blood vessels in middle layers

bundles of smooth muscle fibers + C.T.

3) Endometrium

(1) Simple columnar epithelium

ciliated cells, secretory cells

(2) Lamina propria:

stromal cell

uterine glands:

(3) Basalis

  • the closed tips of the uterine glands

  • straight arteries

  • not shed

(4) Functionalis

  • cyclic changes

  • hormone  responsive

  • spiral arteries

2. Cyclic changes in the endometrium

Menstrual cycle



proliferative phase

secretory phase

time (day)




ovary phase

follicular phase

luteal phase






spiral A.

constricted  relaxed  broken




highly coiled

uterine glands



highly coiled

epithelial cells





stroma cells








3. Uterine Cervix

1) Mucous

(1) Epithelium not desquamate

cervical canal: simple columnar epithelium

protio vaginalis: stratified squamous epithelium

(2) Cervical glands

2) Myometrium

few smooth muscle fibers , mainly C.T.

3) Adventitia

IV. Vagina fibromuscular tubular structure

1. Mucosa

1) Epithelium

stratified squamous nonkeratinized epithelium

glycogen → lactic acid

2) lamina propria

loose C.T., rich in elastic fibers, highly vascular
2. Muscularis
3. Adventitia

dense C.T., rich in elastic fibers

V. Mammary Glands

dense C.T. + adipose tissue + compound tubuloalveolar glands

1. Structures:

1) Compound tubuloalveolar glands

alveoli intralobular ducts interlobular ducts lactiferous ducts

lactiferous sinuses opening

simple cuboidal epithelium simple columnar stratified cuboidal/columnar stratified squamous epithelium

2) Alveoli

secreting cell: milk secretion

myoepithelial cells
2. Different state of mammary gland

1) Inactive (resting) mammary gland

inactive duct system

2) Active mammary gland

pregnancy: alveoli proliferate

lactation: milk secretion & accumulation

The Eye and the Ear


The Eyeball

I. The wall of eyeball

A. Tunica fibrosa (external layer)

Cornea limbus cornea sclera

1. Cornea:

    1. Epithelium: stratified squamous non - keratinizing epithelium

    2. Bowman’s membrane (anterior limiting membrane)

    3. Stroma (substantia propria)

collagen fibers, chondroitin sulfate, keratan sulfate

    1. Descemet’s membrane (posterior limiting membrane)

collagen fibrils

    1. Endothelium: simple squamous epithelium

2. Limbus cornea

trabecular meshwork, sinus venosus sclerae (canal of Schlemm)

3. Sclera

many bundles of collagen fibers

scleral spur

lamina cribrosa

B. Uveal coat (vascular layer)

iris ciliary body choroids

1. Iris:

pupil, anterior chamber, posterior chamber

      1. Anterior border layer: fibroblasts & melanocytes

      2. Iris stroma: blood vessels, melanocytes

      3. Epithelial layer

a. The anterior layer:

dilator pupillae muscle (sympathetic)

sphincter pupillae muscle (parasympathetic)

b. The posterior layer: pigmented epithelial layer cuboidal epithelial cells

2. Ciliary body

      1. Ciliary muscle:

      2. Vascular layer

      3. Ciliary epithelium

          1. The outer layer: pigmented, simple cuboidal epithelium

          2. The inner layer: nonpigmented, simple cuboidal epithelium

secreting aqueous humor forming ciliary zonule
3. Choroid

(1) The outer layer: large vessels, melanocytes

(2) The middle layer: choriocapillary layer

(3) The inner layer: glassy or Bruch’s membrane

C. Retina

Retina ora serrata double - layered epithelium

  1. Pigment epithelium

melanin, lamellar debris, vitamin A, rhodopsin

  1. Photoreceptors:

    1. Rods: 120milion

a. The outer segment: membranous discs

11-cirretinae + opsins rhodopsin

b. The inner segment: M, rER, ribosomes

    1. Cones: 700milion

a. The membranous discs are continuous

b. Visual pigments (blue, green, red)

c. enriched in fovea

  1. Bipolar cells: synapses

  2. Ganglion cells: synapses

  3. Ten layers

    1. Pigment epithelial layer *

    2. Layer of rods & cones *

    3. Outer limiting membrane

    4. Outer nuclear layer *

    5. Outer plexiform layer

    6. Inner nuclear layer *

    7. Inner plexiform layer

    8. Ganglion cell layer *

    9. Nerve fiber layer

(10) Inner limiting membrane

  1. Macula lutea: 3-4mm, fovea centralis only cones

  2. Optic disc and Optic nerve

Papilla of optic verve
II. The Refractive Media

A. Lens

  1. Lens capsule: collagen fibrils

  2. Lens epithelium: simple cuboidal epithelium

  3. Lens fibers: hexagonal prismatic

  4. Accommodation

B. Aqueous humor

1. Production

2. Drain passage

C. Vitreous body

  1. Hyaluronic acid, vitrein, collagen fibrils

  2. Hyalocyte

III. Light conducting passage
Accessory Organs of the Eye

I. Eyelids

    1. Skin: eyelash, glands of Zeis

glands of Moll

    1. Hypodermis

    2. Muscular layer: Orbicularis oculi muscle


Palpebral muscle

    1. Tarsal plates: tarsal (Meibomian) glands

    2. Conjunctiva

II. Lacrimal gland
The Ear

I. External ear

      1. Auricle

      2. External auditory meatus: ceruminous gland

      3. Tympanic membrane

II. Middle ear

A. Tympanic cavity: malleus, incus, stapes

Simple squamous or low cuboidal epithelium

B. Eustachian tube

III. Internal ear

A. Osseous labyrinth

  1. Vestibule and semicircular canals:

Oval window, Round window

  1. Cochlea

modiolus, scala vestibuli & scala tympani Helicotrema, cochlear duct

B. Membranous labyrinth

  1. Membrane semicircular canals, Utricle, Saccule

simple squamous or cuboidal epithelium

(1) Macula utriculi and macula sacculi

    1. Supporting cells

    2. Hair cells: stereocilia, kinocilium

    3. Otolithic membrane, otoliths

(2) Crista ampullaris: Cupula

  1. Cochlear duct

      1. Vestibular membrane

      2. Spiral ligament, stria vascularis (endolymph)

      3. Osseous spiral lamina

Membranous spiral lamina (Basilar membrane)

Auditory string

      1. Tectorial membrane

      2. Organ of Corti (spiral organ)

                1. Pillar cell

                2. Phalangeal cell

                3. Hair cell

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