The Skeletal System Overview

The Skeletal System

• The human skeleton is divided into two groups: the axial skeleton and the appendicular skeleton.
• The axial skeleton forms the central axis of the body and includes the skull, bony thorax (ribs and sternum), and vertebral column.
• The appendicular skeleton is everything else, including the bones of the shoulder girdle, upper limbs, pelvic girdle, and lower limbs.

Bones of the Skeletal System

• Skull: Cranial bones (forms the top and back, encloses the brain), Facial skeleton (makes up the face).
• Cranial Bones: Frontal, parietal, occipital, temporal, sphenoid, ethmoid.
• Facial Bones: Nasal, zygomatic, maxilla, mandible.

Types of Bones

• Long Bones: Femur (thigh), tibia (larger shin), fibula (smaller shin), humerus (upper arm), radius (larger forearm), ulna (smaller forearm).
• Short Bones: Carpals (wrist) and tarsals (ankle).
• Flat Bones: Skull, sternum (breastbone), scapula (shoulder blade).
• Irregular Bones: Vertebrae (spine), pelvic bones.

Bony Thorax

• Forms a cage to protect major organs such as the heart and lungs.
• Consists of the ribs (true ribs 1-7, false ribs 8-12, and floating ribs 11-12), the sternum, and the thoracic vertebrae.

The Vertebral Column

• Composed of vertebrae separated by intervertebral discs.
• Has normal curves.
• Each vertebrae is given a name according to its location (cervical, thoracic, lumbar, sacrum, coccyx).

Bones of the Upper Limb

• Arm (humerus): The main bone in the upper arm.
• Forearm (radius and ulna): Bones that allow the forearm to rotate.
• Wrist (carpals): Small bones in the wrist.
• Palm (metacarpals): Bones in the palm of the hand.
• Fingers (phalanges): Bones of the fingers.

Bones of the Lower Limb

• Thigh (femur): The main bone in the thigh.
• Leg (tibia and fibula): Bones that form the lower leg.
• Ankle (tarsals): Small bones of the ankle.
• Foot (metatarsals): Bones in the sole of the foot.
• Toes (phalanges): Bones of the toes.
• Pelvic Girdle: Includes the hip bones (ilium, ischium, pubis) along with the sacrum and coccyx.

Joint Movements

• Joints allow movement between bones. Common movements include flexion, extension, abduction, adduction, circumduction, and rotation.

Types of Synovial Joints

• Freely movable joints include: ball-and-socket (e.g., hip and shoulder), hinge (e.g., elbow, knee), pivot (e.g., proximal & distal radio-ulnar), gliding (e.g., sternoclavicular, between carpals or tarsals), saddle (e.g., wrist), condyloid (e.g., wrist, metacarpophalangeal joint, metatarsophalangeal joint).