Describe the composition of the human appendicular skeleton, and state the functions performed by the skeletal system as a whole.

Question

Accepted Answer

Concept understanding — Appendicular Skeleton

The first time you hear "appendicular skeleton," think of the word appendage — something attached to the main body. Your arms and legs are your appendages. So the appendicular skeleton is simply the set of bones that make up your limbs and the bony rings that connect them to your trunk.

Your body has a central axis — the skull, spine, and ribcage — called the axial skeleton. Everything else that sticks out from that axis is appendicular. If the axial skeleton is the core of the body, the appendicular skeleton is everything that lets you reach, grab, walk, and kick.

The precise statement

The appendicular skeleton consists of 126 bones in total. It is divided into two major parts:

The pectoral (shoulder) girdle — connects the upper limbs to the axial skeleton.
The pelvic (hip) girdle — connects the lower limbs to the axial skeleton.
The upper limbs — arms, forearms, wrists, and hands.
The lower limbs — thighs, legs, ankles, and feet.

Here is the exact bone count, which is exam-favourite:

Region	Bones per side	Total bones
Pectoral girdle (clavicle + scapula)	2	4
Upper limb (humerus, radius, ulna, carpals × 8, metacarpals × 5, phalanges × 14)	30	60
Pelvic girdle (hip bone)	1	2
Lower limb (femur, patella, tibia, fibula, tarsals × 7, metatarsals × 5, phalanges × 14)	30	60
Total		126

Note

The patella (kneecap) is counted in the lower limb, not in the girdle. The clavicle and scapula together form one pectoral girdle on each side.

Why the girdles matter

The pectoral girdle is not a complete ring — the scapula floats on the back, held by muscles, not a bony joint to the spine. This gives your shoulder enormous mobility (you can rotate your arm in a full circle) but less stability. That is why shoulder dislocations are common.

The pelvic girdle is a rigid, complete ring fused to the sacrum. It bears the entire weight of the upper body and transfers it to the legs. Stability is paramount here — you cannot afford your hip to pop out while standing. …

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The appendicular skeleton, totalling 126 bones, is made of the two limb girdles together with the bones of the four limbs they support. The pectoral girdle contributes 4 bones -- a clavicle and a scapula on each side -- suspending and anchoring the upper limb and providing the shallow, mobile socket of the shoulder joint. The two upper limbs together contribute 60 bones: a humerus, a radius and an ulna on each side (6 bones), 8 carpal bones of each wrist (16 bones), 5 metacarpal bones of each hand (10 bones), and 14 phalanges of each hand (28 bones). The pelvic girdle contributes 2 bones, the two coxal (hip) bones, each itself formed by the fusion of an ilium, an ischium and a pubis, which together with the sacrum and coccyx of the axial skeleton form the bony pelvis. The two lower limbs together contribute 60 bones: a femur, a tibia, a fibula and a patella on each side (8 bones), 7 tarsal bones of each ankle (14 bones), 5 metatarsal bones of each foot (10 bones), and 14 phalanges of each foot (28 bones). Adding these, 4 + 60 + 2 + 60, gives the appendicular skeleton's total of 126 bones, which together with the axial skeleton's 80 bones makes up the complete 206-bone adult skeleton. The skeletal system as a whole, of which the appendicular skeleton is one division, performs several essential functions: it gives the body its definite shape and mechanical support; it protects delicate internal organs (though this is chiefly the role of the axial skeleton); it provides t …

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Q.Describe the composition of the human appendicular skeleton, and state the functions performed by the skeletal system as a whole.

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