Appendicular Skeleton

Appendicular Skeleton• Contains 126 bones between 4 groups:

– Pectoral girdle (4)– Arms (60)– Legs (60)– Pelvic girdle (2)

Pectoral Girdle: attaches the upper appendage to the thorax

Pectoral Girdle• Includes 2 bones (on each side)- clavicle

and scapula.

• Weaker girdle than the pelvic girdle– Not designed to be weight bearing– Small point of attachment with the axial

skeleton (at the sternoclavicular joint)– Most of the girdle is supported by back

muscles.

Clavicle: the anterior bone of the pectoral girdle

• S-shaped

• Collarbone

• Articulates with the manubrium of the sternum (sternoclavicular joint). This is a diarthroses (gliding joint).

Clavicular Landmarks• Sternal end: the thickened medial end of the

clavicle that articualtes with the manubrium of the sternum.

• Acromial end: the thinner lateral end of the clavicle that articulates with the acromion of the scapula.

• Conoid tubercle: a small projection found on the inferior surface of the lateral end of the clavicle.– This can help determine if it is the left/right clavicle.

Scapula: the posterior bone of the pectoral girdle.

• Larger than the clavicle

• Triangular shaped

• Attached to the axial skeleton through the joint it forms with the clavicle (acromioclavicular joint).

• Held in place by the larger muscles of the back.

Anterior Scapular Landmarks• Superior angle: the highest point on the scapula.

• Superior border: the superior edge of the scapula.

• Inferior angle: the lowest point on the scapula.

• Medial (vertebral) border: a thin ridge of bone found close to the vertebral column.

• Lateral (axillary) border: a thick ridge of bone found close to the humerus and inferior to the Glenoid fossa.

Anterior Scapular Landmarks cont…• Scapular notch: a small “cut out” in the

superior border of the scapula, medial to the coracoid process.– Allows blood vessels to pass over the superior

border in order to feed and drain the arm. This notch protects the vessels.

• Subscapular fossa: a large shallow depression found on the anterior surface of the scapula.– In this case, “sub” means “underneath”.

Anterior Scapular Landmarks cont…

• Coracoid process: a long, tube-like projection found medial to the Glenoid fossa.– Where the pectoralis minor and biceps brachii

attach.

Posterior Scapular Landmarks• Spine: a prominent ridge of bone found on the

posterior surface of the scapula.

• Acromion: a wide flat projection found on the lateral end of the spine.– Angled 90° anterior to the spine.– Articulates with the acromial end of the clavicle at the

acromioclavicular joint.

• Supraspinous fossa: a shallow depression found superior to the spine of the scapula.– PFMA.

Posterior Scapular Landmarks• Infraspinous fossa: a large shallow depression

found inferior to the spine of the scapula.– PFMA

• Glenoid (cavity) fossa: a shallow depression found superior to the lateral (axillary) border.– Articulates with the head of the humerus to form

the shoulder joint. This helps form the socket of the “ball and socket”. This joint is not a tight fit which allows a range of motion.

The Upper Appendages• 30 bones in each arm

• Proximal Distal: Humerus Radius Ulna Carpals (8) Metacarpals (5) Phalanges (14)

• Humerus: single bone of the upper arm.–Largest bone of the arm

Proximal Humeral Landmarks• Head: the rounded proximal end of the humerus.

– Articulates with the glenoid fossa (not tightly which allows for a wide range of motion)

• Anatomical neck: a small line found just distal to the head of the humerus.– Site of the epiphyseal line (where the growth plate

has completely ossified).

• Greater tubercle: a large blunt projection found on the proximal end of the humerus, lateral to the head.

Proximal Humeral Landmarks cont..• Lesser tubercle: a small blunt projection found on the

proximal end of the humerus on the anterior surface.– This helps determine if it is the right/left humerus because

it is only on the anterior surface.

• Intertubercular (sulcus) groove: an elongated channel (groove) found between the greater and lesser tubercles.– Allows the tendon of the biceps brachii muscle to pass

over the head on its way to the scapula-without being bent.

Proximal Humeral Landmarks cont..• Surgical neck: the constricted region found

inferior to the intertubercular sulcus.– This is a term created by doctors.– Most commonly fractured region of the humerus.– Where the compact bone of the diaphysis thins to

transition to spongy bone of the epiphyses.

• Deltoid tuberosity: a large slightly rounded projection found on the lateral surface of the diaphysis.– Point for the deltoid muscle attachment.

Distal Humeral Landmarks• Capitulum: the rounded lateral condyle of the

humerus.– Articulates with the head of the radius to help

stabalize the elbow joint.

• Trochlea: the pulley-shaped medial condyle of the humerus.– Articulates with the ulna to form the “functional” part

of the elbow that allows it to be a hinge joint.

* Most condyles are specifically named but these 2 are shaped so differently!

Distal Humeral Landmarks cont..• Medial epicondyle: a large projection found

proximal to the trochlea.– PFMA– This region is called the “funny bone”. The

sensation that you feel when you hit this is actually due to the pressure put on the ulnar nerve that runs posteriorly to this.

• Lateral epicondyle: a small projection found proximal to the capitulum.– PFMA

Distal Humeral Landmarks cont..• Coronoid fossa: a small projection found proximal to

the capitulum.– It accepts the coronoid process of the ulna when the elbow

is bent.– If we didn’t have this, we wouldn’t be able to bend the joint

so far.

• Olecranon fossa: a large shallow depression found proximal to the trochlea on the distal posterior surface of the humerus.– This accepts the olecranon of the ulna and allows the

elbow to straighten.

Radius• The lateral bone of the forearm.

– On the thumb side– Helps to stabilize the elbow joint.

• Head: the flattened proximal end of the radius.– Articulates with the capitulum of the humerus.

• Radial tuberosity: a small round projection found on the anterior surface just distal to the head.– Where the biceps brachii attaches and pulls on the

radius.

Radius continued…• Styloid process: a small triangular projection

found on the distal lateral surface.– PFMA– Can be felt as a bump on the distal, lateral

surface.

Ulna• The medial bone of the forearm.

– On the pinky side

• Trochlear notch: a “C” shaped notch found on the proximal anterior surface.– Articulates with the trochlea to form the functional part of

the elbow. This is the pivot point for the hinge joint.

• Coronoid process: a small triangular process found on the anterior surface of the trochlear notch.– Fits into the coronoid fossa of the humerus when the

elbow is bent.

Ulna continued…• Olecranon (process): a large blunt projection

found on the proximal posterior surface.– PFMA– The part of the elbow that “sticks out” when it is

bent.

• Head: the smaller distal end.– The only bone that has the head at the distal end.

• Styloid process: a small triangular projection on the distal medial surface.