Appendicular Skeleton

The appendicular skeleton facilitates movement and locomotion. It comprises the bones of the limbs and the girdles that attach them to the axial skeleton. It includes the pectoral (shoulder) girdle which anchors the upper limbs and the pelvic girdle which supports the lower limbs. The bones of the upper and lower limbs are also included in the appendicular skeleton enabling various movements.

Pectoral Girdle

The pectoral girdle is also called the shoulder girdle. It connects the forelimbs to the axial skeleton and provides mobility to the arms. It consists of four bones- two clavicles and two scapulae.

• Scapula, also known as the shoulder blade is a flat and triangular bone. It consists of the body, spine, acromion process, coracoid process and glenoid cavity. The acromion process is responsible for the formation of the shoulder with clavicle bone, the Coracoid process is responsible for the attachment of muscles and the Glenoid cavity is responsible for the articulation of the head of the humerus by the ball and socket joint
• Clavicle, also known as the collarbone is an F-shaped bone. It has two ends, namely, dorsal and ventral ends. The Dorsal end of the Clavicle is attached to the acromion process of the scapula while the ventral end is attached to the sternum.

Forelimbs

Bones of the Forelimbs allow intricate movements and dexterity.

The forelimbs are composed of –

• Humerus, also known as the funny bone, is present in the upper arm. In the humerus, the deltoid ridge is present. 
• Radius and Ulna are present in the forearm or lower arm. Radius is present on the little finger side while Ulna is present on the side of the thumb. The elbow is formed by the junction of the radius, ulna and humerus. 
• 8 Carpals are present in the wrist. They are very irregular in shape like pebbles and slide over each other. 
• 5 Metacarpals are present in the palm. 
• 14 Phalanges are present in fingers. Two are present in the thumb and three in each finger. The digit formula is 2,3,3,3,3.

Pelvic Girdle

The pelvic girdle, also known as the hip girdle, connects the lower limbs to the axial skeleton and provides support for the body’s weight. It consists of two coxal bones. These two bones are joined by a cartilaginous joint, known as Pubic Symphysis. It opens at the time of delivery resulting in a broader hip region of females after childbirth. Coxal bone is formed by the fusion of three bones during the embryonic stage. These bones are Ilium(largest), Ischium, and Pubis(smallest). In the region of Ischium, Obturator Foramen is present which is formed by the ischium and pubis. It is a hole from where blood vessels, nerves, ducts etc. go from the upper body to the lower body. Acetabulum is formed by all three bones and is responsible for the attachment of the femur. 

Lower Limbs

Bones of lower limbs enable walking, running, and various other movements

The lower limbs consist of-

• Femur is the thickest, strongest, and longest bone of the human body. It is present in the thigh. The head of the femur articulates with the acetabulum of the hip girdle. 
• Tibia and Fibula are bones present in the leg. Tibia, also known as the shin bone, is the second longest and strongest bone of the body. 
• 7 Tarsals are present in the ankle. 
• 5 Metatarsals are present in the foot. 
• 14 Phalanges are present in the toe having a digit formula similar to that of the fingers of the Forelimbs.

The Skeletal system provides structural support, protects our internal organs, and facilitates movement. The skeletal system of humans is primarily formed by bones, cartilage, ligaments, and tendons. All these work together to form the structure of the human body. The skeletal system also takes part in the hormone regulation and storage of essential minerals. It contributes to blood cell production and in maintaining mineral balance.