B.1.1.1 Axial and appendicular skeleton components and their functions Notes

The Human Skeleton: Axial and Appendicular Components

1. The human body performs a wide range of movements through the coordinated action of bones, joints, and muscles.
2. The human skeleton serves as the structural framework of the body, supporting movement, protecting vital organs, and facilitating physiological processes like blood cell production.
3. It is divided into two major components:
   1. Axial Skeleton – Forms the central core of the body.
   2. Appendicular Skeleton – Comprises the limbs and structures associated with movement.

The Axial Skeleton: The Central Framework

The axial skeleton includes 80 bones, divided into three major regions:

1. Skull (Cranium & Facial Bones)
   1. Protects the brain and supports the facial structures.
   2. Includes cranial bones (frontal, parietal, temporal, occipital) and facial bones (maxilla, mandible, zygomatic).
2. Vertebral Column (Spine)
   1. Provides structural support and flexibility.
   2. Consists of 33 vertebrae divided into five regions:
      1. Cervical (7): Supports the head and allows movement.
      2. Thoracic (12): Attaches to ribs, providing thoracic cage support.
      3. Lumbar (5): Bears most of the body's weight.
      4. Sacrum (5 fused): Connects the spine to the pelvis.
      5. Coccyx (4 fused): Forms the tailbone.
3. Thoracic Cage (Rib Cage & Sternum)
   1. 12 pairs of ribs protect the heart and lungs.
   2. Sternum (breastbone) connects to ribs via cartilage, providing flexibility.

Primary Functions of the Axial Skeleton

1. Protection: Shields vital organs like the brain, heart, and lungs.
2. Support and Posture: Provides a stable framework for the body.
3. Attachment for Muscles: Serves as a base for muscles involved in breathing and maintaining posture.

Appendicular Skeleton

The appendicular skeleton consists of 126 bones that facilitate movement and allow interaction with the environment. Major Components of the Appendicular Skeleton:

1. Pectoral (Shoulder) Girdle
   1. Composed of clavicle (collarbone) and scapula (shoulder blade).
   2. Attaches the upper limbs to the axial skeleton and provides mobility.
2. Upper Limbs
   1. Includes the humerus (upper arm), radius & ulna (forearm), carpals (wrist), metacarpals (hand), and phalanges (fingers).
   2. Designed for movement, grasping, and fine motor control.
3. Pelvic Girdle
   1. Composed of the ilium, ischium, and pubis, which fuse to form the hip bones.
   2. Connects the lower limbs to the axial skeleton and provides weight-bearing support.
4. Lower Limbs
   1. Includes the femur (thigh bone), patella (kneecap), tibia & fibula (lower leg), tarsals (ankle), metatarsals (foot), and phalanges (toes).
   2. Built for weight-bearing, balance, and propulsion during movement.

Primary Functions of the Appendicular Skeleton

1. Movement: Provides a framework for muscles to generate movement.
2. Support: Bears the weight of the body during activities like walking or running.
3. Storage and Haemopoiesis: Long bones store minerals and produce blood cells in their marrow.

Key Positional Terms

To describe the location of body parts and joint movements, we use positional terminology. These terms are based on the standard anatomical position:

1. Body upright
2. Facing forward
3. Arms at the sides
4. Palms facing forward
5. Feet flat on the ground

This universal reference point ensures clarity and consistency when discussing movements, injuries, and anatomical structures.