Chapter 7: The Skeletal System – Structured Study Notes

Module 7.1 Overview of the Skeletal System

Structural Divisions of the Skeleton

The human skeleton is divided into two main structural divisions: the axial skeleton and the appendicular skeleton. Each division has distinct components and functions essential for support, movement, and protection.

• Axial Skeleton: Composed of the skull, vertebral column, and thoracic cage. Provides central support and protects vital organs.

• Appendicular Skeleton: Includes the limbs and girdles. Facilitates movement and interaction with the environment.

Cartilage Tissues in the Skeleton

Cartilage is a flexible connective tissue found in various parts of the skeleton, serving as a precursor to bone and providing cushioning at joints.

• Hyaline Cartilage: Found at articular surfaces, costal cartilages, and the nose.

• Fibrocartilage: Present in intervertebral discs and pubic symphysis.

• Elastic Cartilage: Located in the ear and epiglottis.

Additional info: Cartilage is avascular and heals slowly compared to bone.

Module 7.2 The Skull

Structure and Features of the Skull

The skull consists of cranial bones, which protect the brain, and facial bones, which form the structure of the face.

• Cranial Bones: Include the frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones.

• Facial Bones: Include the maxilla, mandible, zygomatic, nasal, lacrimal, palatine, vomer, and inferior nasal concha.

Sinuses and Sutures

Sinuses are air-filled cavities that reduce skull weight and enhance voice resonance. Sutures are immovable joints connecting skull bones.

• Major Sinuses: Frontal, maxillary, ethmoid, and sphenoid sinuses.

• Major Sutures: Coronal, sagittal, lambdoid, and squamous sutures.

Comparison of Child and Adult Skulls

Child skulls have fontanelles (soft spots) that allow for growth and flexibility during birth. Adult skulls have fully fused sutures.

• Fontanelles: Anterior, posterior, sphenoidal, and mastoid fontanelles in infants.

• Fusion: Sutures fuse with age, providing rigidity.

Module 7.3 The Vertebral Column and Thoracic Cage

Curvatures and Structure of the Vertebral Column

The vertebral column supports the body and protects the spinal cord. It consists of several regions with distinct curvatures.

• Cervical (7), Thoracic (12), Lumbar (5), Sacral (5 fused), Coccygeal (4 fused): Regions of the vertebral column.

• Curvatures: Cervical and lumbar are concave; thoracic and sacral are convex.

Thoracic Cage Structure and Function

The thoracic cage protects the heart and lungs and supports breathing.

• Components: Sternum, ribs (12 pairs), and thoracic vertebrae.

• Function: Provides attachment for muscles and supports respiratory movements.

Module 7.4 Bones of the Pectoral Girdle and Upper Limb

Pectoral Girdle

The pectoral girdle connects the upper limb to the axial skeleton and allows for a wide range of motion.

• Clavicle: Acts as a strut to stabilize the shoulder.

• Scapula: Provides attachment for muscles and articulates with the humerus.

Upper Limb Bones

• Humerus: Upper arm bone.

• Radius and Ulna: Forearm bones.

• Carpals, Metacarpals, Phalanges: Bones of the wrist, hand, and fingers.

Module 7.5 Bones of the Pelvic Girdle and Lower Limb

Pelvic Girdle

The pelvic girdle supports the weight of the upper body and protects pelvic organs.

• Hip Bones (Os Coxae): Each formed by the fusion of the ilium, ischium, and pubis.

• Sacrum: Connects the pelvic girdle to the vertebral column.

Lower Limb Bones

• Femur: Thigh bone, the longest bone in the body.

• Patella: Kneecap, protects the knee joint.

• Tibia and Fibula: Bones of the lower leg.

• Tarsals, Metatarsals, Phalanges: Bones of the ankle, foot, and toes.

Additional info: The pelvic girdle is more robust than the pectoral girdle to support body weight during standing and movement.