3.3 Part 2

The Axial Skeleton

• Includes the longitudinal axis of the body, consisting of 80 bones.
• Contains the vertebrae, skull, face, ribs, and sternum.
• Functions:
  • Supports and protects internal organs.
  • Provides attachment sites for muscles.
  • Facilitates respiration.
  • Supports the appendicular skeleton.

The Skull

• Consists of 22 bones: 8 cranial bones and 14 facial bones.
• Cranial bones:
  • House and protect the brain.
  • Form the bony structure surrounding the brain.
• Facial bones:
  • Shape the face.
  • Form the "front porch" of the skull.
• Some bones contain air-filled sinuses:
  • Reduce weight.
  • Mucus membranes moisten and cleanse air.
  • Resonate for speech production.

The Vertebral Column

• Also known as the spine, it protects the spinal cord, supports the head and body, and has 4 spinal curves:
  • Cervical: develops after standing and balancing.
  • Thoracic: primary accommodates organs.
  • Lumbar: develops after standing.
  • Sacral: primary accommodates organs.

The Vertebrae

• The vertebral column comprises 26 bones:
  • 24 vertebrae, sacrum, and coccyx.
  • 7 cervical vertebrae: support the neck.
  • 12 thoracic vertebrae: support the upper back and each articulate with one or more pairs of ribs.
  • 5 lumbar vertebrae: support the lower back.
  • Sacrum: articulates with the 5th lumbar vertebra.
  • Coccyx: articulates with the sacrum.

Structure of a Vertebra

• The articular processes have facets on articular faces.
• The shape of the vertebrae changes from superior to inferior.

Vertebral Components

• Intervertebral disks:
  • Pads of fibrocartilage separating the vertebral bodies.
  • Absorb shocks.
• Vertebral canal:
  • Houses the spinal cord.
  • Encloses the spinal cord.
• Vertebral foraminae:
  • Gaps between adjacent vertebrae.
  • Allow for nerve connections.

The Thoracic Cage

• The skeleton of the chest, supporting the thoracic cavity.
• Consists of:
  • Thoracic vertebrae.
  • Ribs and costal cartilages.
  • Sternum (breastbone).
• Functions:
  • Protects organs.
  • Attaches muscles involved in respiration, pectoral girdle, upper limbs, and vertebral column.

The Ribs & Sternum

• Functions:
  • Absorb shocks.
  • Provide flexibility and mobility.
  • Support breathing by altering the width and depth of the thoracic cage.
• Sternum:
  • Flat bone in the midline of the chest wall.
  • Xiphoid process attaches to the diaphragm and rectus abdominus.

The Appendicular Skeleton

• Allows us to move and manipulate objects.
• Includes all bones besides the axial skeleton:
  • The limbs (arms and legs).
  • The supportive girdles (pectoral and pelvic).

The Pectoral Girdle

• Also called the shoulder girdle – connects the arms to the body.
• Functions:
  • Positions shoulders.
  • Provides a base for arm movement.
• Consists of:
  • 2 clavicles (collar bones).
  • 2 scapulae (shoulder blades).
• Connects with the axial skeleton only at the manubrium.

The Upper Limbs

• Composed of arms, forearms, wrists, and hands.
• Humerus: the single bone composing the arm (brachium).

The Forearm & Wrist

• Forearm (antebrachium) consists of:
  • 2 long bones: ulna (medial) and radius (lateral).
• Wrist:
  • 8 carpal bones (4 proximal and 4 distal).
  • Allows wrist to bend and twist.

The Pelvic Girdle

• Made of two hipbones (ossa coxae).
• Provides strength to bear body weight and stress of movement.
• Forms part of the pelvis.

The Lower Limbs

• Functions:
  • Weight bearing.
  • Motion.
• Major bones:
  • Femur (thigh).
  • Patella (kneecap).
  • Tibia and fibula (leg).
  • Tarsals (ankle).
  • Metatarsals (foot).
  • Phalanges (toes).

Femur, Tibia & Fibula

• Femur: the longest and heaviest bone in the body.
• Tibia and Fibula: the two bones composing the leg.

Summary

• Axial skeleton: supports the head and body, protects internal organs; Includes the vertebral column, vertebral structure and thoracic cage.
• Appendicular skeleton: for movement, includes pectoral & pelvic girdle, arms and legs.

Explore the components and functions of the axial skeleton, including its role in supporting and protecting internal organs. This quiz covers the anatomy of the skull, vertebral column, and the overall significance of these structures in the human body.