Skeletal System - Appendicular Skeleton

Appendicular Skeleton

Shoulder Girdles

The shoulder or pectoral girdle attaches the bone of the upper extremities to the axial skeleton.

Structurally, each of the two shoulder girdles consists of two bones, a clavicle and a scapula. The clavicle or collar bones are long slender bones with a double curvature. The two bones lie horizontally in the superior and anterior part of the thorax, superior to the first rib.

Scapulae or shoulder blades are large, triangular flat bones situated in the dorsal part of the thorax between the levels of the second and seventh rib.

The upper limbs consist of 60 bones. The skeleton of the upper limb includes a humerus in each arm, an ulna and radius in each forearm, carpals or wrist bones, meta-carpals which are the palm bones and phalanges in the fingers of each hand.

The humerus or arm bone is the longest and largest bone of the upper limb. Ulna is the medial bone of the forearm. Radius is the lateral bone of the forearm.

The carpus or wrist consists of eight small bones united to each other by ligaments. The bones are arranged in two transverse rows, with four bones in each row. The five bones of the metacarpus constitute the palm of the hand. Each metacarpal bone consists of a proximal base, a shaft and a distal head.

The phalanges or bones of the fingers number 14 in each hand. There are 2 phalanges in the thumb and 3 bones in each of the remaining 4 finger.

Pelvic Girdle : It consists of two coxal bones called pelvic or hip bones. It provides a strong and stable support for the lower extremities on which the weight of the body is carried. The coxal bones are fused together and are attached to the sacrum of the vertebral column.

The pelvic girdle serves as a basis to shelter some important organs of the abdominal cavity. The basin-shaped cavity is called as pelvis which is larger in females than in males. Each hip bone is formed of three bones firmly united with one another. They are the ilium, ischium and pubis. The ilium is the upper flat part which is connected to sacrum. The ischium is the lower most part of the hip bone. The pubis is the front part of the hip bone. The two pubis bones meet in front by a cartilage called pubis symphysis. Between the pubis and ischium is a hole in each hip bone. On each outerside of the hip bone where the three bones meet is a deep socket known as acetabulum. The head of the thigh bone (femur) fits into it and hip joint is formed.

The lower extremities are composed of 60 bones. These include the femur of each thigh, each kneecap, the fibula and tibia in each leg, the ankle bones in each ankle, the metatarsals and phalanges of each foot.

1. Illium

2. Ischium

3. Pubis

4. Symphysis pubis

5. Acetabulum

The femur or thigh bone is the longest and heaviest bone in the body. Its proximal end articulates with the coxal bone. Its distal end articulates with the tibia.

Patella or knee cap is a small, triangular bone anterior to the knee

joint.

Tibia and fibula : Tibia is the longer bone of the leg. It bears the major portion of the weight on the leg. The fibula is smaller than the tibia. The tarsus contain seven bones of the ankle. It has a broad, flat surface. The metatarsus consists of five metatarsal bones. It is thicker than others because it bears more weight. The phalanges of the foot resemble those of the hand both in number and arrangement.