Appendicular skeleton

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  Diagram of the appendicular skeleton

Appendicular Skeleton

The appendicular skeleton is a major division of the human skeleton that includes the bones of the limbs and the supporting girdles. It is primarily involved in movement and locomotion, providing attachment points for muscles and facilitating a wide range of motion.

Structure

The appendicular skeleton is composed of 126 bones and is divided into two main regions: the pectoral girdle and the pelvic girdle, along with the bones of the upper and lower limbs.

Pectoral Girdle

The pectoral girdle, also known as the shoulder girdle, connects the upper limbs to the trunk. It consists of two bones on each side:

• The clavicle (collarbone) - a long bone that serves as a strut between the shoulder blade and the sternum.
• The scapula (shoulder blade) - a flat, triangular bone that provides attachment for several muscles and articulates with the humerus.

Upper Limbs

The upper limbs are specialized for a wide range of movements and consist of 30 bones in each arm:

• The humerus - the long bone of the upper arm.
• The radius and ulna - the two bones of the forearm.
• The carpals - eight small bones that make up the wrist.
• The metacarpals - five bones that form the palm of the hand.
• The phalanges - 14 bones that make up the fingers.

Pelvic Girdle

The pelvic girdle, or hip girdle, attaches the lower limbs to the axial skeleton and supports the weight of the upper body. It consists of two hip bones (coxal bones), each formed by the fusion of three bones:

• The ilium - the broad, flaring portion of the hip bone.
• The ischium - the lower, posterior part of the hip bone.
• The pubis - the anterior portion of the hip bone.

Lower Limbs

The lower limbs are adapted for weight-bearing and locomotion, consisting of 30 bones in each leg:

• The femur - the longest and strongest bone in the body, located in the thigh.
• The patella - a small, triangular bone that protects the knee joint.
• The tibia and fibula - the two bones of the lower leg.
• The tarsals - seven bones that make up the ankle.
• The metatarsals - five bones that form the arch of the foot.
• The phalanges - 14 bones that make up the toes.

Function

The appendicular skeleton serves several key functions:

• Movement: It provides the framework for muscle attachment, allowing for a wide range of movements.
• Support: It supports the weight of the body and helps maintain posture.
• Protection: It protects vital organs, such as the reproductive organs in the pelvic region.

Related Pages

• Axial skeleton
• Human anatomy
• Bone
• Joint
• Muscle