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 contains specific bone groups with distinct functions.

• Axial Skeleton: Composed of the skull, vertebral column, and thoracic cage. Provides support and protection for the brain, spinal cord, and thoracic organs.

• Appendicular Skeleton: Includes the bones of the limbs and girdles (pectoral and pelvic). Facilitates movement and interaction with the environment.

Bone Markings and Their Functions

Bones display various markings that serve as sites for muscle attachment, passage of nerves and blood vessels, and articulation with other bones.

• Foramen: Opening for nerves and blood vessels.

• Process: Projection for muscle or ligament attachment.

• Fossa: Depression that often accommodates another bone.

Types of Cartilage Tissues in the Skeletal System

Cartilage is a flexible connective tissue found in various locations within the skeletal system, each type serving specific functions.

• Hyaline Cartilage: Provides smooth surfaces for joint movement; found in articular surfaces, costal cartilages, and nose.

• Fibrocartilage: Offers strength and shock absorption; found in intervertebral discs and pubic symphysis.

• Elastic Cartilage: Maintains shape and flexibility; found in the ear and epiglottis.

Main Functions of the Skeletal System

• Support: Framework for the body.

• Protection: Shields vital organs (e.g., brain, heart).

• Movement: Provides levers for muscles.

• Mineral Storage: Reservoir for calcium and phosphorus.

• Blood Cell Production: Occurs in red bone marrow (hematopoiesis).

Module 7.2 The Skull

Cranial Bones: Location, Structure, and Function

The skull consists of cranial bones that encase and protect the brain, connected by sutures.

• Frontal, Parietal, Temporal, Occipital, Sphenoid, Ethmoid: Main cranial bones.

• Sutures: Immovable joints between cranial bones (e.g., coronal, sagittal, lambdoid).

Facial Bones and the Hyoid Bone

Facial bones form the structure of the face and support sensory organs. The hyoid bone supports the tongue and is unique for not articulating with other bones.

• Maxilla, Mandible, Zygomatic, Nasal, Lacrimal, Palatine, Vomer, Inferior Nasal Concha: Main facial bones.

• Hyoid Bone: Located in the neck; supports tongue and aids in swallowing.

Orbital, Nasal Cavity, and Paranasal Sinuses

The skull contains cavities and sinuses that serve protective and functional roles.

• Orbit: Houses the eyes.

• Nasal Cavity: Passage for air; lined with mucous membrane.

• Paranasal Sinuses: Air-filled spaces that lighten the skull and enhance voice resonance.

Comparing Infant and Adult Skulls

• Infant Skull: Features fontanelles (soft spots) for growth and flexibility during birth.

• Adult Skull: Sutures are fused; bones are fully ossified.

Module 7.3 The Vertebral Column and Thoracic Cage

Curvatures of the Vertebral Column

The vertebral column has four main curvatures that provide balance and flexibility.

• Cervical and Lumbar Curves: Concave posteriorly.

• Thoracic and Sacral Curves: Convex posteriorly.

Vertebrae, Sacrum, and Coccyx

The vertebral column is composed of individual vertebrae, the sacrum, and the coccyx.

• Cervical (7), Thoracic (12), Lumbar (5): Regions of vertebrae.

• Sacrum: Five fused vertebrae.

• Coccyx: Four fused vertebrae (tailbone).

Intervertebral Discs and Ligaments

Intervertebral discs and ligaments provide cushioning and stability to the vertebral column.

• Intervertebral Discs: Fibrocartilaginous pads between vertebrae; absorb shock.

• Ligaments: Connect vertebrae and maintain alignment.

Thoracic Cage: Structure and Function

The thoracic cage protects vital organs and supports respiration.

• Ribs, Sternum, Thoracic Vertebrae: Main components.

• Function: Protects heart and lungs; assists in breathing.

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: Collarbone; acts as a strut for shoulder stability.

• Scapula: Shoulder blade; provides attachment for muscles.

Bones of the Upper Limb

The upper limb consists of several bones that facilitate movement and manipulation.

• 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 (Ilium, Ischium, Pubis): Fuse to form the pelvis.

Male vs. Female Pelvis

The adult male and female pelvis differ in structure to accommodate childbirth in females.

• Female Pelvis: Wider, shallower, larger pelvic inlet.

• Male Pelvis: Narrower, deeper, smaller pelvic inlet.

Bones of the Lower Limb

The lower limb bones support body weight and enable locomotion.

• Femur: Thigh bone; longest and strongest bone.

• Patella: Kneecap.

• Tibia and Fibula: Bones of the leg.

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