An Introduction to the Appendicular Skeleton

An Introduction to the Appendicular Skeleton

The Appendicular Skeleton is composed of the 126 bones of the appendages (limbs) and the pectoral and pelvic girdles, which attach to the axial skeleton. Each limb is composed of three segments connected by freely movable joints.

Identify bone markings of each bone. The markings will help you to determine whether a bone is the right or left member

The Pectoral Girdle

The pectoral girdle, also called the shoulder girdle consists of two clavicles two scapula. The pectoral girdle connects the arms to the axial skeleton Provides arm movement and shoulder movement. Copyright 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Clavicles

The Clavicles, called collarbones, are long, S-shaped bones. It s medial end attaches to the sternal manubrium (sternal end). This articulation is called the sternoclavicular joint. This is the only bony attachment between the upper extremity and the axial skeleton.

The lateral end is flattened and articulates with the scapulae (acromial end) to form part of the shoulder. This articulation is called the acromioclavicular joint.

The clavicle serves as a brace, or strut, to hold the arm away from the top of the thorax.

The Scapulae

The Scapulae or shoulder blade are broad, flat triangles. They have two important processes: the acromion and coracoid process. The acromion connects with the clavicle.

The beaklike coracoid (corac = crow, raven) process points anteriorly over the tip of the shoulder joint and anchors some of the upper limb muscles. The scapula has no direct attachment to the axial skeleton.

The scapula has 3 angles: superior, inferior, and lateral and 3 named borders: superior, medial, and lateral.

Notice the spine of the scapula, located on the posterior. There are several fossae (shallow depressions) that appear on both sides of the scapula and are named according to location.

The glenoid cavity, a shallow socket articulates the humerus head of the arm bone.

The Arm

The humerus (the brachium) consists of the only bone in the arm. It is involved in the formation of 2 major joints: the shoulder and the elbow joint.

The humerus head fits into the shallow glenoid cavity. The greater (lateral) and lesser (medial), turbercles are separated by a groove, the intertubercular sulcus that guides the tendon of the bicep muscle to the glenoid cavity.

The posterior view of the humerus has a roughened area, the deltoid tuberosity, where the shoulder deltoid muscle attaches.

The distal end of the humerus are the medial trochlea (looking rather like a spool), which articulates with the ulna. The lateral capitulum articulates with the radius of the forearm. The condyles are flanked by the medial and lateral epicondyles.

Above the trochlea is the coronoid fossa on the anterior surface. The posterior surface is the olecranon fossa. The depressions allow the ulna to flex and extend.

The Forearm

The Forearm (also called the antebrachium) consists of two long bones: the Ulna (medial) and the Radius (lateral). In the anatomical position the radius is in the lateral and the ulna is in the medial position. They are joined by an interosseous membrane.

The Radius diskshaped head articulates with the capitulum of the humerus. Just below the head is the Radial tuberosity where the tendon of the biceps muscle of the arm attaches.

The lateral aspect of its distal end is the expanded styloid process. Palpatate the syloid process (thumb side), move your fingers just medially onto the anterior wrist. Press firmly and then let up slightly on the pressure. You should feel your radial pulse.

The Ulna the medial bone of the forearm. Its proximal end bears the anterior coronoid process and the posterior olecranon process (the point of the elbow), which are separated by the trochlear notch.

The Hand

The skeleton of the hand includes 3 groups of bones: the carpals (wrist bones), metacarpals (bones of the palm), and phalanges (bones of the fingers).

The carpus (the wrist) is arranged in 2 irregular rows of four bones each. The bones are bound by ligaments. The 4 proximal bones: Scaphoid: Near styloid process, Lunate: Medial to scaphoid, Triquetrum: Medial to lunate bone, Pisiform: Anterior to triquetrum

The Four Distal Carpal Bones: Trapezium: Lateral, Trapezoid: Medial to trapezium, Capitate: Largest, Hamate: Medial, distal

The Metacarpal Bones, numbered 1 to 5 from the thumb side of the hand, radiate out from the wrist like spokes to form the palm of the hand. They articulate with proximal phalanges. Clench your fist and find the knuckles, these are your metacarpophalageal joints.

Phalanges, mini long bones of the hands, (14 total finger bones). Like the bones of the palm, the fingers are numbered from 1 to 5, beginning from the thumb side of the hand. Each finger has 3 phalanges (proximal, middle, distal), except the thumb (pollex) which has 2 (proximal & distal).