CH 7: Skeletal System

Overview of the Skeletal System

The skeletal system provides the structural framework for the human body, supporting and protecting vital organs, enabling movement, and serving as a site for hematopoiesis. It is divided into two major divisions: the axial skeleton and the appendicular skeleton.

• Axial Skeleton: Forms the longitudinal axis of the body and consists of 80 bones.

• Appendicular Skeleton: Includes the bones of the limbs and girdles, facilitating movement.

The Axial Skeleton

The axial skeleton is responsible for supporting and protecting the brain, spinal cord, and organs within the thoracic cavity. It also provides attachment sites for muscles involved in head, neck, and trunk movements.

• Main Components:

  • Skull and associated bones

  • Thoracic cage

  • Vertebral column

  • Associated cartilages

• Total Bones: Approximately 80 bones

Functions of the Axial Skeleton

• Support and Protection:

  • Protects the brain (skull)

  • Encloses the spinal cord (vertebral column)

  • Shields organs in the trunk (thoracic cage)

• Attachment Sites: Provides sites for muscle attachment, aiding in movement and posture.

Axial Skeleton: Skull

Structure of the Skull

The skull is a complex structure composed of cranial and facial bones, as well as associated bones. It protects the brain and forms the structure of the face.

Associated Bones

• Hyoid Bone: Supports the larynx and serves as an attachment for muscles involved in swallowing and speech.

• Auditory Ossicles: Three small bones (malleus, incus, stapes) in each middle ear cavity, essential for hearing by transmitting sound vibrations.

The Axial Skeleton: Thoracic Cage

Structure and Function

The thoracic cage consists of the thoracic vertebrae, ribs, and sternum. It forms the rib cage, which protects the heart, lungs, and other thoracic organs.

• Components:

  • Ribs (24)

  • Sternum (1)

  • Costal cartilages (connect ribs to sternum)

• Functions:

  • Protection of vital organs

  • Support for breathing muscles

  • Attachment for muscles involved in respiration and upper limb movement

The Axial Skeleton: Vertebral Column

Structure of the Vertebral Column

The vertebral column is a flexible, segmented structure that supports the head and trunk, protects the spinal cord, and transfers body weight to the lower limbs.

• Intervertebral Discs: Pads of fibrocartilage between vertebral bodies, providing cushioning and flexibility.

• Vertebral Canal: Formed by vertebral foramina, enclosing the spinal cord.

Functions of the Vertebral Column

• Supports the weight of the head, neck, and trunk

• Transfers weight to the lower limbs

• Protects the spinal cord

• Maintains upright posture

Summary Table: Axial Skeleton Components

Key Terms and Definitions

• Axial Skeleton: The central part of the skeleton, including the skull, vertebral column, and thoracic cage.

• Cranium: The part of the skull that encloses the brain.

• Hyoid Bone: A U-shaped bone in the neck that supports the tongue and larynx.

• Auditory Ossicles: Small bones in the middle ear that transmit sound vibrations.

• Intervertebral Discs: Fibrocartilaginous pads between vertebrae, providing cushioning.

Additional info:

• The comic in the first image is not relevant to Anatomy & Physiology study content and is excluded from academic notes.