The fibula, or calf bone, parallels and articulates with the tibia. It is not weight-bearing, but acts as a site for muscle attachment while forming the lateral part of the ankle joint. The tarsals are the seven bones of the ankle, which transmits the weight of the body from the tibia and the fibula to the foot. The metatarsals are the five bones of the foot, while the phalanges are the 14 bones of the toes.
Learning Objectives Describe the bones and functions of the human appendicular skeleton. Key Points The human appendicular skeleton is composed of the bones of the upper limbs, the lower limbs, the pectoral girdle, and the pelvic girdle.
The pectoral girdle acts as the point of attachment of the upper limbs to the body. The upper limb consists of the arm, the forearm, and the wrist and hand. The pelvic girdle is responsible for bearing the weight of the body and is responsible for locomotion; it is also responsible for attaching the lower limbs to the body. The lower limbs, including the thighs, legs, and feet, support the entire weight of the body and absorb the resulting forces from locomotion. Key Terms axial skeleton : the bones of the head and trunk of an organism appendicular : of or pertaining to a limb or appendage clavicle : the collar bone; the prominent bone at the top of the chest between the shoulder and the neck scapula : either of the two large, flat, bones forming the back of the shoulder articulate : to form a joint or connect by joints.
Human Appendicular Skeleton The human appendicular skeleton is composed of the bones of the upper limbs which function to grasp and manipulate objects and the lower limbs which permit locomotion.
The Pectoral Girdle The pectoral girdle bones, providing the points of attachment of the upper limbs to the axial skeleton, consists of the clavicle or collarbone in the anterior, as well as the scapula or shoulder blades in the posterior. The Upper Limbs The upper limbs contain 30 bones in three regions: the arm shoulder to elbow , the forearm ulna and radius , and the wrist and hand.
The appendicular skeleton is composed of the bones of the upper limbs which function to grasp and manipulate objects and the lower limbs which permit locomotion. It also includes the pectoral girdle, or shoulder girdle, that attaches the upper limbs to the body, and the pelvic girdle that attaches the lower limbs to the body Figure 1.
Figure 1. The appendicular skeleton is composed of the bones of the pectoral limbs arm, forearm, hand , the pelvic limbs thigh, leg, foot , the pectoral girdle, and the pelvic girdle. The pectoral girdle bones provide the points of attachment of the upper limbs to the axial skeleton. The human pectoral girdle consists of the clavicle or collarbone in the anterior, and the scapula or shoulder blades in the posterior Figure 2.
Figure 2. The clavicles are S-shaped bones that position the arms on the body. The clavicles lie horizontally across the front of the thorax chest just above the first rib. These bones are fairly fragile and are susceptible to fractures.
For example, a fall with the arms outstretched causes the force to be transmitted to the clavicles, which can break if the force is excessive. The clavicle articulates with the sternum and the scapula. The scapulae are flat, triangular bones that are located at the back of the pectoral girdle. They support the muscles crossing the shoulder joint.
A ridge, called the spine, runs across the back of the scapula and can easily be felt through the skin Figure 2. The spine of the scapula is a good example of a bony protrusion that facilitates a broad area of attachment for muscles to bone.
Figure 3. The upper limb consists of the humerus of the upper arm, the radius and ulna of the forearm, eight bones of the carpus, five bones of the metacarpus, and 14 bones of the phalanges. The upper limb contains 30 bones in three regions: the arm shoulder to elbow , the forearm ulna and radius , and the wrist and hand Figure 3. An articulation is any place at which two bones are joined. The humerus is the largest and longest bone of the upper limb and the only bone of the arm.
It articulates with the scapula at the shoulder and with the forearm at the elbow. The forearm extends from the elbow to the wrist and consists of two bones: the ulna and the radius. The clavicle has several important functions. First, anchored by muscles from above, it serves as a strut that extends laterally to support the scapula. This in turn holds the shoulder joint superiorly and laterally from the body trunk, allowing for maximal freedom of motion for the upper limb. The clavicle also transmits forces acting on the upper limb to the sternum and axial skeleton.
Finally, it serves to protect the underlying nerves and blood vessels as they pass between the trunk of the body and the upper limb. The clavicle has three regions: the medial end, the lateral end, and the shaft. The medial end, known as the sternal end of the clavicle , has a triangular shape and articulates with the manubrium portion of the sternum. This forms the sternoclavicular joint , which is the only bony articulation between the pectoral girdle of the upper limb and the axial skeleton.
The lateral or acromial end of the clavicle articulates with the acromion of the scapula, the portion of the scapula that forms the bony tip of the shoulder. There are some sex differences in the morphology of the clavicle. In women, the clavicle tends to be shorter, thinner, and less curved. In men, the clavicle is heavier and longer, and has a greater curvature and rougher surfaces where muscles attach, features that are more pronounced in manual workers.
The clavicle is the most commonly fractured bone in the body. Such breaks often occur because of the force exerted on the clavicle when a person falls onto his or her outstretched arms, or when the lateral shoulder receives a strong blow. Because the sternoclavicular joint is strong and rarely dislocated, excessive force results in the breaking of the clavicle, usually between the middle and lateral portions of the bone. If the fracture is complete, the shoulder and lateral clavicle fragment will drop due to the weight of the upper limb, causing the person to support the sagging limb with their other hand.
Muscles acting across the shoulder will also pull the shoulder and lateral clavicle anteriorly and medially, causing the clavicle fragments to override. The clavicle overlies many important blood vessels and nerves for the upper limb, but fortunately, due to the anterior displacement of a broken clavicle, these structures are rarely affected when the clavicle is fractured. The pelvic girdle is a ring of bones attached to the vertebral column that connects the bones of the lower limbs to the axial skeleton.
The pelvic girdle consists of the right and left hip bones. Each hip bone is a large, flattened, and irregularly shaped fusion of three bones: the ilium, ischium, and pubis. Female and Male Pelvis. The female and male pelvises differ in several ways due to childbearing adaptations in the female. The lower limbs include the bones of the thigh, leg, and foot. The femur is the only bone of the thigh.
It articulates with the two bones of the leg—the larger tibia commonly known as the shin and smaller fibula. The thigh and leg bones articulate at the knee joint that is protected and enhanced by the patella bone that supports the quadriceps tendon. The bones of the foot include the tarsus, metatarsus, and phalanges. Foot Bones. The bones of the foot consist of the tarsal bones of the ankle, the phalanges that form the toes, and the metatarsals that give the foot its arch.
Ankle Bones.
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