The Appendicular Skeleton

The Appendicular Skeleton

* Limb bones and their girdles are appended, or attached to the axial skeleton
* The pectoral girdle attaches the upper limbs to the trunk
* The pelvic girdle secures the lower limbs
* The upper and lower limbs differ in their functions but share the same structural plan

The Pectoral Girdle

* Consists of the clavicle and the scapula
- do not completely encircle the body
* Medial end of each clavicle articulates with the manubrium and first rib
* Laterally, the ends of the clavicles join the scapulae
- scapulae do not join each other

Pectoral Girdle Functions

* Provides attachment for many muscles that move the upper limb
* The girdle is light allows upper limbs to be mobile
* Only the clavicle articulates with the axial skeleton
* Glenoid cavity - socket of the shoulder joint is shallow
- good for flexibility but bad for stability

Clavicles (‘Little Keys’)

* Aka collarbones are slender and S-shaped
* Extend horizontally across the superior thorax
* The flattened acromial end articulates with the scapula laterally
* The cone-shaped sternal end attaches to the manubrium medially


Clavicle Functions

* Provide attachment for muscles
* Act as braces - holds the scapulae and arms out laterally from the thorax
- a fractured clavicle will cause the entire shoulder region to collapse
* Transmits compression forces from the upper limbs to the axial skeleton
- allows you to push a heavy object

Scapulae

* Are thin, triangular flat bones located on the dorsal surface of the rib cage
- between rib 2 superiorly and rib 7 inferiorly
* 3 borders: Superior – shortest and sharpest;
Medial (vertebral) – parallels the vertebral column;
Lateral (axillary) – abuts the axilla and ends superiorly in the glenoid cavity (shallow fossa)
* 3 angles: Lateral – by the glenoid cavity;
Superior – the superior and medial borders meet;
Inferior – junction of the medial and lateral borders
* Biceps muscle
* Articulates with the humerus
* Suprascapular nerve
* Subscapularis muscle

Muscles:

* Infraspinatus
* Supraspinatus

The Upper Limb

* 30 bones – arm, forearm, and hand
* Humerus – only bone of the arm
- longest and strongest bone of the upper limb
- articulates with the scapula at the shoulder
- articulates with the radius and ulna at the elbow
- provides sites for muscle attachment
- provides articulation sites for other bones

* Rotator cuff muscles
* Guides a tendon of the biceps
* Deltoid muscle
* Radial nerve
* Epicondyles muscle sites
* ‘Pulley’ articulates with ulna
* ‘Small head’ articulates with radius

Antebrachium or Forearm

* 2 parallel long bones, the radius and the ulna
- articulate with the humerus proximally and bones of the wrist distally
- articulate with each other proximally and distally at the radioulnar joints
* Interosseous membrane interconnects the radius and ulna
* In anatomical position the radius is lateral
- when the palm faces posteriorly, the 2 bones form an X distal end of the radius crosses over the ulna

Details of Arm and Forearm
a) Anterior view
Ulna (‘elbow’)

* Main bone forming the elbow joint with the humerus
- slightly longer than the radius, looks like a monkey wrench
* 2 projections at the proximal end - olecranon process and coronoid process
- separated by the trochlear notch (a deep concavity)
* Hinge joint allows forearm to bend upon the arm (flex), then straighten again (extend)
* Distally ulna shaft ends in a knoblike head that articulates with the radius
- head is separated from the carpals by fibrocartilage disc that plays little or no role in hand movement

Ulna - Proximal Part

* Extended – olecranon process locks into the olecranon fossa of the humerus
Flexed – coronoid process fits into the coronoid fossa of the humerus

Radius and Ulna
Distal Ends of the Radius and Ulna
Hand
Carpus
Bones of the Hand
Metacarpus
Phalanges
Pelvic Girdle
Bony Pelvis
Coxal Bones
Ilium
Ishium
Pubis or Pubic Bone
Lateral and Medial Views of the Os Coxae
True and False Pelves
The Pelvis
Pelvic Structures and Childbearing
The Lower Limb
Thigh
Patella
Leg
Tibia and Fibula
The Foot
Tarsus
Metatarsus
Phalanges of the Toes
Arches of the Foot
Disorders of the Appendicular Skeleton
Appendicular Skeleton Throughout Life
Changes in Body Proportions
Adult Skeleton

The Appendicular Skeleton.ppt