Skeleton The bones of the upper and lower limbs along with their girdles constitute the appendicular skeleton. The appendicular skeleton is composed of bones. (a) The Pectoral girdle The upper limbs are attached to the pectoral girdles. These are very light and allow the upper limbs a degree of mobility not seen anywhere else in the body.
The girdle is formed of two halves . Each half of the pectoral girdle (Figure . ) consists of a clavicle or collar bone and a scapula . The scapula is a large, thin, triangular bone situated in the dorsal surface of the ribcage between the second and seventh ribs.
It has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion . The clavicle articulates with this process. Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint. Each clavicle is a long slender bone with two curvatures which lies horizontally and connects axial skeleton with appendicular skeleton.
The Upper Limb The upper limb consists of separate bones and is specialized for mobility. The skeleton of the arm, the region between the shoulder and elbow is the humerus . The head of humerus articulates with the glenoid cavity of the scapula and forms the shoulder joint. The distal end of humerus articulates with the two forearm bones the radius and ulna .
The forearm is the region between the elbow and the wrist. Olecranon process is situated at the upper end of the ulna which forms the pointed portion of the elbow.The hand consists of carpals, metacarpals and phalanges. Carpals, the wrist bones, in number are arranged in two rows of four each. The anterior surface of the wrist has tunnel- like appearance, due to the arrangement of carpals with the ligaments.
This tunnel is termed as carpal tunnel . XI Std Biology-Zoology Chapter- CTS-(Carpal Tunnel Syndrome ) – The narrow passage (tunnel) bounded by bones and ligaments in the wrist gets narrowed and pinches