The appendicular skeleton of human body

  • Appendicular skeleton is composed of bones which lie on the lateral sides of the mid axial line (Axial skeleton) of our body and consists of the hanging bones.
  • It can be divided into two groups;
  1. The upper extremities (Pectoral girdle and the bones of upper limbs)
  2. The lower extremities (Pelvic girdle and the bones of lower limbs)

*Girdle is the bony or cartilaginous arch that supports the limbs of the vertebrates.

The upper extremities (64 bones):

  • The upper extremity is connected to and supported by the axial skeleton by only one joint (pectoral girdle or the shoulder joint) and many muscles.
  • The joint is the sternoclavicular joint between the manubrium of the sternum and the clavicle.
  • The upper extremities consist of 64 bones which include;
  1. Clavicle (2 bones):
  • It is a collar bone, double curved long bone with rounded medial end and flattened lateral end.
  • It holds the shoulder joint and arm away from thorax so upper limb can swing freely.

     2. Scapula (2 bones):

  • It is a shoulder blade which is flat and triangular with horizontal spine separating fossae.
  • It is the site of attachment of muscles of arm and chest.
  • The glenoid fossa receives the head of humerus.
                                                                                                  Pectoral girdle (shoulder joint)
  1. Humerus (2 bones):
  • It is the longest and the largest bone of the upper limb.
  • It forms ball and socket joint with the glenoid fossa of scapula.
  • Muscles of the shoulder and arm attach to the humerus permitting arm to flex and extend at elbow.
  1. Radius and ulna (4 bones):
  • There are 1 radius and 1 ulna in each forearm respectively.
  • Radius is the shorter of two bones present in forearm.
  • It allows forearm to rotate in radial motion.
  • Ulna is the larger of the two bones in forearm.
  • Larger proximal end consists of olecranon process (prominence of elbow).
  • It forms hinge joint at the elbow.
  1. Carpals (16 bones):
  • There are 8 carpals in each wrist.
  • They are small and short bones.
  • 8 carpals are arranged in 2 transverse rows of 4.
  • They help in slight gliding movement because of attached ligaments.
  1. Metacarpals (10 bones):
  • They are five miniature long bones in each hand in fan like arrangement.
  • They articulate with the fingers at metacarpo-phallangeal joint (the knuckles).
  • They aid in opposition movement of thumb and enable cupping of hand.
  1. Phalanges (28 bones):
  • There are 14 phalanges in each hand.
  • They are miniature long bones; 2 in each thumb and 3 in each finger.
  • They articulate with each other at inter-phalangeal joint and allow fingers to participate in stable grips.
     Bones of upper limb

The lower extremities (62 bones):

  • It can be divided into two parts; the pelvic girdle or the hip joint and the bones of lower limbs.
  • The lower extremities consist of 62 bones which include:
  1. Pelvic girdle (2 bones):
  • The bone is called pelvis or hip bone or coxa.
  • It is an irregular bone formed by the fusion of ilium, ishium and pubis (which are separate in children).
  • The hip bone is fused with the sacrum and coccyx to form a pelvis.
  • The head of femur fits into the acetabulum in the pubis of hip bone to form a ball and socket joint.
  • Pelvis girdle is also the site of attachment of trunk and lower limb muscles.
  • It also transmits body weight to femur.
                                                                                          Pelvic girdle (hip bones)
  1. Femur (2 bones):
  • It is a typical long bone in the thigh (also called a thigh bone).
  • It is the longest, strongest and heaviest bone.
  • It forms a ball and socket joint with the pelvic bones.
  • Femur provides articular surfaces for knee and supports the body.
  1. Patella (2 bones):
  • This is the bone present in each knee.
  • It is roughly triangular or circular flat sesamoid bone (developed from the tendon quadriceps femoris).
  • It increases the leverage for quadriceps muscle by keeping tendon away from the axis of rotation.
  • It protects the knee joint.
  1. Tibia and fibula (4 bones):
  • There are 1 tibia and 1 fibia in each leg respectively.
  • Tibia is the larger long bone of the lower leg (calf region) which articulates with the femur, fibula and tarsals.
  • It supports the body weight transmitting it from femur to the tarsals.
  • Fibula is the smaller long bone of the lower leg.
  • It articulates proximally with tibia and distally with tarsals.
  • It bears little body weight but gives strength to the ankle joint.
  1. Tarsals (14 bones):
  • They are short bones in the ankle region (also called the heelbones).
  • They are 7 in each ankle and with the metatarsals form the arches of foot.
  • They also bear body weight, raise the body and transmit thrust during running and walking.
  1. Metatarsals (10 bones):
  • They are miniature long bones, 5 in each foot and form the sole.
  • With tarsals, they form arches of feet and also improve stability while standing.
  • Metatarsals also absorb shocks, bear weight and aid in locomotion.
  1. Phalanges (28 bones):
  • There are 14 phalanges in each foot.
  • They are the miniature long bones in the toes.
  • They are arranged as in hand (2 in each big toe and 3 in each other toe).
  • They provide stability during locomotion.


                                 Bones of lower limb

The appendicular skeleton of human body