Human Anatomy Class Notes Skeletal System



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Human Anatomy – Class Notes Skeletal System


Skeletal System

  • There are 206 bones in the human body

  • The Skeletal system performs five major functions



  1. Support and Structure

  • The skeletal system is the body’s framework

  • It supports the body and provides structure much like a building under construction has a frame to support the walls and ceilings

  • Exoskeletons are outside – crabs and roaches have Exoskeletons, - they have NO backbone

  • Internal or ENDOSKELETON – this skeleton is inside the body – birds, monkeys, snakes, and humans have endoskeletons



  1. Movement

  • To provide movement, you must have muscles

  • Bones attached to other bones via ligaments (bones are held together by ligaments)

  • Muscles attached to bone via tendons

  • Muscles and bones work together to move the body



  1. Protection

-the skeletal system protects vital tissues and organs

- For example: the skull protects the brain, the ribcage protects the lungs, and the backbone protects the spinal cord



  1. Storage area for blood clotting

  • Stores products that help body function

  • For example: bleeding – the body forms a blood clotting agent that comes from the bones



  1. Blood Manufacturing

  • New blood cells

  • Red blood cells are produced

  • There are 27 trillion red blood cells in the body

  • Marrow is where new red blood cells form

  • Blood travels through veins

Bones and Cartilage

  • Bones are the strongest material in the body – bones represent only 14% of body weight

  • When a person is born, the majority of their bones are made of cartilage

  • Cartilage is more flexible

  • From 7 months to age 25 cartilage gradually is replaced by bones

  • Babies have a “soft spot” on their head because the skull starts out as cartilage to fit through the birth canal - eventually the bones of the skull fuse together to create bone

  • Bones continue to reform through life

  • Cartilage provides a smooth surface for bones to glide across and bend and is more slippery than ice

  • You will find cartilage in your knee, nose, and elbow - and is located between bones

  • Breakdown in cartilage causes bone to rub against bone, this can be painful and can also lead towards arthritis

  • Your knee absorbs the most pressure from the body - Cartilage provides a cushion

Joints

  • Joints keep bones far enough apart so they don’t rub together and they hold bones in place

  • The skeleton is moveable because of the joints it contains

  • The FOUR types of joints are

  1. Hinge Joint – only moves in one direction

Example: elbow and knee are the two main areas with hinge joints

  1. Ball and Socket – this joint is in the shoulder and allows for movement in many directions

  2. Pivot Joint – this joint is found in the neck – you can move and twist the neck back and forth, up and down

  3. Fixed Joints – These joints do not move – the bones come together but there is no movement

Example: the skull is a fixed joint

Injury

There are two types of fractures



  1. Simple fracture – a bone breaks but it doesn’t come through the skin

  2. Compound fracture – a bone breaks and pushes through the muscle and skin

Ligaments

  • Connect the bone to bone

  • Sprain – this occurs when a ligament is torn or over stretched

  • Muscle – a muscle can be strained if it is over stretched

  • Cramp – a sudden strong contraction of a muscle – ex: charley horse or a knot


THE SPINE

  • There are curvature abnormalities in the spine, they include

1) Scoliosis: an abnormal curvature that usually occurs in the thoracic region of the spine.



  • The spine is normally “S” shaped but scoliosis is more of a curve

  • It is more common in girls

  • It can be treated surgically or with a brace

  • A person with scoliosis may have one leg longer than the other

2) Kyphosis: an extreme thoracic curvature that creates a condition called a hunchback

- it is caused by rickets (a bacterial infection) and/or tuberculosis of the spine
3) Lordosis: This is an extreme lumbar curvature

- it affects people with potbellies or pregnant women

- it is also referred to as swayback
THE BONY THORAX


  • This is also referred to as the thoracic ribcage

  • It is the point of attachment for the neck, head, back, chest, and shoulder muscles

  • It is made up of 3 parts

  1. 12 thoracic vertebrae

-divides the ribcage in the back


  1. Sternum or breastbone

-forms the anterior midline of the ribcage


  1. Ribs

-there are 12 paired flat bones = 24 total ribs

-forms a lateral or side bar of the cage

-ribs are directly attached to the thoracic vertebrae in the back
-TRUE Ribs are the 1st 7 pair of ribs (totaling 14) – they are attached anteriorly to the sternum by hyaline cartilage
-FALSE Ribs – these are the bottom 5, indirectly attached to the sternum by cartilage above them
-FLOATING Ribs- the last two ribs are false ribs called floating ribs because they have no attachment; they are only attached via muscles hence floating.
rib-cage.jpg
The skeletal system is broken down into 2 divisions


  1. Axial

  2. Appendicular

AXIAL

  • An axis is an imaginary line – for the skeletal system it goes straight down the body

  • There are 80 bones in the Axial division

  • These bones form a long axis of the body and skeletal system

There are 3 regions

A) skull


B) vertebral column (or backbone)

C) bony thorax (or rib cage)

The three regions have a job – to protect the head, neck and torso which is the brain, spinal cord, and lungs & heart

The Skull is the most complex part of the axial system



TWO KEY TERMS for axial system

PAIRED- 2 identical bones for example: in your skull the temporal bone

ARTICULATE – connects with – Ex. Your radius and ulna are connected to the humorous

The axial is divided into planes

TRANSVERSE – Horizontal


  • Superior and inferior

FRONTAL – Vertical, head to foot or up and down

-anterior (front) and posterior (back)

SAGITAL – vertically right to left


  • Medial (toward the midline) and lateral (away from the midline)

  • Proximal – near the trunk

  • Distal – away from the trunk

Appendicular Skeleton– it helps us move

-Made up of upper and lower limbs (arms and legs)

-girdles attach the limbs to the axial skeleton

- all the bones help us move and manipulate our environment



UPPER LIMBS OF THE APPENDICULAR SYSTEM

  • One of the most important bones is the pectoral girdle or the shoulder girdle (there are two in our body)

  • Attaches upper limb to trunk of body and anchors muscles

Each girdle is made up of two bones

  1. Clavicle – also called the collarbone. It is the anterior bone

  2. Scapula – or the shoulder blade is the posterior bone

BONES IN THE UPPER LIMBS

  • You have 30 bones in the upper limb

  • 27 bones in a hand

Humerus – IN THE UPPER ARM, AND IS THE ONLY BONE IN THE UPPER ARM, IT IS THE LARGEST AND LONGEST BONE IN UPPER LIMBS

ALSO CALLED THE FUNNY BONE



Radius – CONTAINED IN THE FOREARM – ENDS CLOSER (PROXIMAL ENDS) TO THE TRUNK CONNECT WITH THE HUMERUS TO FORM ELBOW

Ulna – DISTAL ENDS CONNECT WITH HAND TO FORM THE WRIST AND IS IN THE FOREARM

Bones in the hand

8 carpals – bones that form the wrist

5 metacarpals –(form the palm)

12 phalanges (fingers and the thumb)

**the thumb is also called the pollex

THE SKULL


  • There are 22 bones in the skull not including the 3 bones in each of our ears

  • The skull is broken into two sets, the cranial and facial




  1. CRANIAL or CRANIUM– Helmet or top part of the skull

  • The cranium has 8 bones – 2 paired and 4 unpaired

  • Paired bones include the parietal and Temporal

  • Unpaired bones include the frontal, occipital, ethmoid, and sphenoid


PAIRED BONES

FRONTAL – forms the front of the head (forehead) and the eye sockets also called the superior orbits

Also includes he paranasal sinuses which are the mucus lined cavities that filter air
OCCIPITAL – forms the base and back of the head
ETHMOID - forms the nasal cavity and the septum, is at the base of the cranium
SPENOID – articulates or connects with all cranial bones, it is also called the keystone of the cranium and is located at the base of the cranium
UNPAIRED BONES

PARIETAL – forms the roof of the cranium


TEMPORAL – forms the lower outer side of the cranium
The –oids
ethmoid and sphenoid are found in the inside, they are the internal bones in the cranium
The –als
Frontal, Parietal, Occipital, and Temporal are the external bones of the cranium



  1. FACIAL – Jaw, eye sockets, provide cavities for the eyes and nose

  • There are 14 facial bones, 6 paired and 2 unpaired






PAIRED BONES

UNPAIRED

NASAL – Bridge of nose

LACRIMAL – anterior medial orbits, tear sacs

ZYGOMATIC- cheek

INFERIOR NASAL CONCHA- side walls of nasal cavity

MAXILLAE – eye socket, nasal cavity

PALATINE –floors of orbits, walls of nasal cavities, and portion of the hard palate



MANDIBLE – jaw bone

VOMER – poster and inferior parts of nasal septum


Hyboid Bone – not officially part of a bone. It does not articulate or connect with any other bone. It’s the little bone bit below the jaw; it’s the point of attachment for the tongue, throat, and neck muscles


THE VERTEBRAL COLUMN


  • Also called the backbone

  • There are 26 bones in the vertebral column

  • And it is broken down into 5 pieces

Cervical division – has 7 vertebrae and is located in the neck


Thoracic division – has 12 vertebrae and is located in the chest area, the rib cage connects with it.
Lumbar division – there are 5 vertebrae and is located in the lower back (small of the back)
Sacrum division – there are 5 vertebrae and it articulates with the pelvis; it is fused or melted together
Coccyx – it had 3 fused vertebrae and is also called the tailbone
skeleton

Answers


skeleton labeled
Appendicular Skeleton: the Upper Limbs

From the Standard deviants video


  • The appendicular skeleton helps us move

  • It is made up of upper and lower limbs which are the arms and legs

  • It is made up of girdles which attach the limbs to the axial skeleton



  • The Pectoral Girdle is also called the Shoulder girdle – there are two in your body which means it is a paired bone

- it attaches the upper limb to trunk of the body and it anchors muscles that move the limb

- there are two bones in the pectoral girdle

1) the clavicle (collarbone): this is the anterior bone

2.) the scapula (shoulder blade): this is the posterior bone



  • There are 30 bones in upper limb

  • There are 27 bones in the hand



  • The Upper arm contains one bone – the humerus - it is the longest and largest bone in the upper limb and it is the only bone in the humerus.



  • The forearm contains two bones, the ulna and radius



  • the proximal ends of the ulna and radius connect with humerus to form elbow



  • The distal ends of the radius and ulna connect with the hand to form the wrist



  • The hand:

8 carpals – bones of the wrist

5 metacarpals – bones of the palm



14 phalanges – fingers and thumbs

***Pollex is fancy word for thumb


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