The appendicular skeleton is the part of the human skeleton that includes the arms and hands, legs and feet, the shoulder girdle and the pelvic girdle. The bones of the appendicular skeleton make up the rest of the skeleton, and are so-called because they are appendages of the axial skeleton.
The pectoral or shoulder girdle consists of the scapulae and clavicles. The shoulder girdle connects the bones of the upper limbs to the axial skeleton. These bones also provide attachment for muscles that move the shoulders and upper limbs. It consist
- Clavicle (2)
- Scapula (2)
- The clavicle or collarbone is located superior to first rib and runs horizontally from the manubrium of the sternum to the acromion of the scapula.
- The clavicle functions like lever arm to help support the humerus and scapula and maintain their position relative to the rib cage.
- The scapula or shoulder-blade is a flat, triangular-shaped bone that lies adjacent to the posterior surface of ribs 2-7.
- It has three borders (superior, lateral, medial), three angles (superior, lateral, medial) and two surfaces (costal, dorsal). A prominent ridge or spine divides the dorsal surface into two, unequal parts called the supraspinous fossa and infraspinous fossa.
- A shallow depression at the lateral angle called the glenoid cavity accepts the head of the humerus to form the shoulder or gleno-humeral joint.
- The scapula also articulates with the clavicle to form the shoulder girdle or pectoral girdle, which supports movements of the humerus.
The upper limbs include the bones of the arm (humerus), forearm (radius and ulna), wrist, and hand. The only bone of the arm is the humerus, which articulates with the forearm bones–the radius and ulna–at the elbow joint. The ulna is the larger of the two forearm bones.
- Humerus (2)
- Radius (2)
- Ulna (2)
- Carpals (16)
- Metacarpals (10)
- Phalanges (28)
The humerus is the long bone in the upper arm. It is located between the elbow joint and the shoulder. At the elbow, it connects primarily to the ulna, as the forearm’s radial bone connects to the wrist. At the shoulder, the humerus connects to the frame of the body via the glenoid fossa of the scapula.
Radius and Ulna
- The lower arm consists of two bones extending from the elbow to the wrist, running parallel to each other.
- The radius is on the outside, or lateral side of the elbow. It connects to the thumb side of the wrist. The radius is bigger and longer than the ulna which is on the inside, or medial side of the forearm closest to the body.
- The bony point of the elbow is actually the tip the ulna bone.The radius and ulna connect to the humerus bone of the upper arm at the elbow joint.
- Carpus is the region between metacarpals and distal ends of radius and ulna. It corresponds to the region of wrist.
- The main role of the carpus is to facilitate effective positioning of the hand and powerful use of the extensors and flexors of the forearm, but the mobility of individual carpal bones increase the freedom of movements at the wrist.
- The carpus is made up of 8 carpal bones.
Metacarpal & Phalanges
- The metacarpal bones are five long cylindrical bones in the body of the hand. The bones run from the carpal bones of the wrist to the base of each digit of the hand.
- On the palm of the hand a thick layer of fibrous, connective tissue pads the bones. The heads of the metacarpal bones form the knuckles.
- Pelvic girdle, also called bony pelvis, basin-shaped complex of bones that connects the trunk and the legs, supports and balances the trunk, and contains and supports the intestines, the urinary bladder, and the internal sex organs.
- The pelvic girdle consists of paired hipbones, connected in front at the pubic symphysis and behind by the sacrum; each is made up of three bones—the blade-shaped ilium, above and to either side, which accounts for the width of the hips; the ischium, behind and below, on which the weight falls in sitting; and the pubis, in front.
- All three unite in early adulthood at a triangular suture in the acetabulum, the cup-shaped socket that forms the hip joint with the head of the femur (thighbone).
- The ring made by the pelvic girdle functions as the birth canal in females. The pelvis provides attachment for muscles that balance and support the trunk and move the legs, the hips, and the trunk.
- In the human infant the pelvis is narrow and non-supportive. As the child begins walking, the pelvis broadens and tilts, the sacrum descends deeper into its articulation with the ilia, and the lumbar curve of the lower back develops.
- Coxal, innominate, or hip bones (2)
The lower extremity refers to the part of the body from the hip to the toes. The lower extremity includes the hip, knee, and ankle joints, and the bones of the thigh, leg, and foot.
- Femur (2)
- Tibia (2)
- Fibula (2)
- Patella (2)
- Tarsals (14)
- Metatarsals (10)
- The femur is the only bone located within the human thigh. It is both the longest and the strongest bone in the human body, extending from the hip to the knee.
- Important features of this bone include the head, medial and lateral condyles, patellar surface, medial and lateral epicondyles, and greater and lesser trochanters.
- The head is where the bone forms the hip joint with the innominate bone. The condyles are the points of articulation (connection) with the tibia, which is a lower leg bone.
- The patellar surface is the groove where the bone adjoins with the patella, or kneecap. The epicondyles and trochanters are all important attachment sites for various muscles.
Tibia & Fibula
- The tibia and fibula are the bones that support the leg. The larger tibia or shinebone is located medial to the fibula and bears most of the weight.
- At the superior (proximal) end of the tibia, a pair of flattened condyles articulate with the rounded condyles at the distal end of the femur to form the knee joint or tibiofemoral joint.
The patella is a triangular shaped bone that covers and protects the distal surface of the anterior femur.The patella is embedded in the quadriceps tendon, which makes it the largest sesamoid (tendon embedded) bone in the body.
Tarsals, Metatarsals & Phalanges
- The foot contains 26 bones that are divided into three regions: the tarsals (or ankle and heel), the metatarsals (forming the sole of the foot), and the phalanges (forming the digits).
- The calcaneus is the thickest tarsal and forms the heel of the foot. Posteriorly the calcaneal tuberosity is the attachment point for the Achilles tendon.
- The navicular bone plays a key role in maintaining the medial longitudinal arch of the foot.
- The foot contains five metatarsals that are numbered I–V, moving medial to lateral, big toe to little toe. Each metatarsal consists of a head, shaft, and base.
- The digits are named in a similar fashion to the metatarsals, medial to lateral from the big toe. With the exception of the big toe, each digit contains a proximal, intermediate, and distal phalange; the big toe lacks an intermediate phalange.