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Guided Notes for the Appendicular Skeleton 1. The clavicle, or collarbone, is a slender, doubly curved bone. It attaches to the manubrium of the sternum medially and to the scapula laterally, where it helps to form the shoulder joint. The clavicle acts as a brace to hold the arm away from the top of the thorax and prevent shoulder dislocation. 2. Each scapula, or shoulder blade, has a flattened body and two important processes. They are the acromion, which is the enlarged end of the spine of the scapula, and the beak-like coracoid process. The acromion connects with the clavicle laterally at the acromioclavicular joint. The coracoid process points over the top of the shoulder and anchors some of the muscles of the arm. Reasons Why the Arm Has Free Movement: 1. Each shoulder attaches the axial skeleton at only 1 point. 2. The loose attachment of the scapula allows it to slide as muscles act. 3. The glenoid cavity is shallow and poorly reinforced. 4. At the midpoint of the humerus is a roughened area called the deltoid tuberosity, which is where the large, fleshy deltoid muscle of the shoulder attaches. 5. The radial groove runs obliquely down the posterior aspect of the shaft of the humerus. This groove marks the course of the radial nerve. 6. Two bones form the skeleton of the forearm: the radius and the ulna. When the body is in the anatomical position, the radius is the lateral bone. The ulna is the medial bone. The two bones are connected along their length by the flexible interosseous membrane. 7. The eight carpal bones are arranged in two irregular groupings of 4 bones each. The carpals are bound together by ligaments that restrict their movement. 8. Each hand contains 14 phalanges. There are 3 in each finger, except in the thumb, which has only two. How are the phalanges named? The 3 phalanges are named (from the wrist) Proximal, Medial, and Distal based on their distance from the wrist 10. The pelvic girdle is formed by 2 coxal bones. Together with the sacrum and the coccyx, they form the bony pelvis. The most important function of the pelvic girdle is bearing weight because the total weight of the upper body rests on the pelvis. 11. Each coxal bone is formed by the fusion of 3 bones: the ilium, the ischium, and the pubis. The pubic bones of each hip fuse anteriorly to form a cartilaginous joint called the pubic symphysis. 12. The ilium, ischium, and pubis fuse at the deep socket called the acetabulum. Its function is to receive the head of the thigh bone. 13. The dimensions of the true pelvis of a woman are very important because they must be large enough to allow the infant’s head to pass during childbirth. 14. The trochanters and the gluteal tuberosity of the femur serve as sites for muscle attachment. The head of the femur articulates with the acetabulum of the hip bone in a deep, secure socket. 15. The tibia and fibula form the skeleton of the lower leg. They are connected along their length by an interosseous membrane. 16. A process of the tibia called the medial malleolus forms the inner bulge of the ankle. The anterior crest of the tibia, also called the shin, is a sharp ridge and is easily felt under the skin because it is unprotected by muscles. 17. The fibula has no part in forming the knee joint. Its distal end, called the lateral malleolus forms the outer part of the ankle. Functions of the Foot: 1) To support the body’s weight 2) To serve as a lever that allows us to propel our bodies forward 19. Body weight is carried mostly by the two largest tarsals, the calcaneus, or heelbone, and the talus. The bones of the foot are arranged to from three strong arches. Ligaments and tendons help to hold the foot in the arched position but still allow a certain amount of give or springiness.