Goals: Compare the structure, location and secretions of sweat and oil glands Compare and contrast the eccrine and Apocrine glands List the parts of the hair



Download 0.5 Mb.
Page1/3
Date03.12.2017
Size0.5 Mb.
  1   2   3


Integumentary System

Part 2 Appendages of the skin


Goals:


  • Compare the structure, location and secretions of sweat and oil glands

  • Compare and contrast the eccrine and Apocrine glands

  • List the parts of the hair follicle and explain their function

  • Describe the purpose of the arrector pili muscle

  • Describe the structure of nails



Vocabulary


Skin appendages

Sweat glands (sudoriferous glands)

Eccrine (merocrine) sweat glands

Apocrine sweat glands

Ceruminous glands

Mammary glands

Sebaceous (oil) glands

Sebum

Hair (pili)

Cuticle

Hair follicles

Hair bulb

Root hair plexus

Connective tissue root sheath

Epithelial root sheet

Hair matrix

Arrector pili

Vellus hair

Terminal hair

Hirsurtism

Alopecia

Nail matrix

Nail folds

Cuticle (eponychium)



A) Sweat (Sudoriferous) Glands

These are found over the entire body. There are approximately 3 million per person



There are 2 types:

  • Eccrine

  • Apocrine

Both are associated with myoepithelial cells which contract when stimulated by the nervous system leading to sweat secretion onto the surface.

1) Eccrine Sweat Glands (Merocrine)

  • Found on the palms, soles and forehead

  • Secretory portion lies in the dermis and the duct extends up through the epidermis

  • Consists of a simple, coiled tubular gland

  • Their secretions are known as sweat and consists of:




In the diagram above, note that the gland in a simple coiled tubular arrangement with the duct going through the epidermis.



2) Apocrine Sweat Glands

  • There are approximately 2000 and they are confined to the anogential and axillary regions

  • These are merocrine glands releasing products by exocytosis

  • Lie deep in the dermis and the ducts empty out onto the hair follicle

  • Composition is similar to Eccrine glands but also contain fatty compounds and proteins making it milky white to yellow in color

  • Decomposition of these secretions by bacteria leads to the creation of body order

  • They begin to function at puberty and are influenced by hormonal cycles

Note how the duct opens into the hair duct in contrast to the sweat glands. They also have a simple coiled tubular arrangement.



3) Ceruminous Glands

  • Modified Apocrine glands that are found in the external ear canal

  • Secretions consist of sebum from the sebaceous glands and a sticky substance secreted from the ceruminous glands, together the product is ear wax.


4) Mammary Glands

  • Glands which have been modified to secrete milk

B) Sebaceous (Oil) Glands

  • Oil glands are simple branched alveolar glands

  • Found over entire body except the soles and palms of feet and hands

  • More concentrated on face, neck and upper chest

  • Central cells of the alveoli accumulate oil and burst releasing cell fragments and lipids in a holocrine type of secretion.

  • Sebum is the secretory material formed from the lipids and cell fragments

  • The sebum is secreted onto the hair follicle

  • Sebum serves to lubricate the hair and skin and has a antibacterial effect

  • Its formation is influenced by sex hormones

  • Arrector pili muscles contract to secrete the sebum

Homeostatic imbalance

If the sebaceous glands become blocked by accumulated sebum and white head (zit) appears. As this material dries it becomes a blackhead. Acne is an inflammation of the sebaceous gland.





C) Hair and Hair Follicles

Hair is distributed over the entire body except the soles, palms, lips and portion of the gentitalia. In the human, it serves to protect the head against trauma and heat loss.



1) Structure of the hair

Hair consists largely of dead keratinized cells that are tougher than those found on the skin. Hair consists of several regions:

a) Shaft – a region where keratinization is complete.

b) Root- a region where keratinization is on going.



The shape of the shaft determines the type of hair.

  • If the shaft is flat and ribbon like in cross section, the hair is kinky

  • If the shaft is oval, the hair is wavy

  • If the shaft is round, the hair is straight and course



Hair is made of 3 concentric levels:

a) Medulla- central core and is filled with large cells and air spaces

b) Cortex- surrounds the medulla and is made of flatten cells

c) Cuticle- outermost layer, one cell layer thick and helps keep hair from matting as it wears out it forms the so called split ends



d) Hair color is produced by the different types of melanin, gray or white hair is brought about by decreased melanin production in the hair follicle. This is brought about by “delayed action genes”





Share with your friends:
  1   2   3


The database is protected by copyright ©dentisty.org 2019
send message

    Main page