Skeletal System Part 2: The Axial Skeleton

Study Notes

Overview of the Skeletal System

Comprises bones, cartilages, and ligaments, providing support and shape to the body.
Total adult bones count: 206, higher in children due to bone fusion during growth.

Primary Functions of the Skeleton

Provides rigid internal structure to support body weight against gravity.
Serves as a framework for muscle action, enabling movement.

Specialization of Skeleton

Lower Skeleton: Specialized for stability during walking and running.
Upper Skeleton: Allows greater mobility and range of motion for carrying and turning movements.

Additional Functions

Protection: Shields vital internal organs (brain, spinal cord, heart, lungs, pelvic organs).
Storage: Stores essential minerals like calcium and phosphate; bone marrow produces blood cells and stores fat.

Divisions of the Skeleton

Divided into two major divisions: Axial and Appendicular.

Axial Skeleton

Forms the vertical, central axis of the body.
Consists of bones of the head, neck, chest, and back.
Protects the brain, spinal cord, heart, and lungs.
Functions as an attachment site for muscles involved in head, neck, back, and limb movement.
Total bones in the axial skeleton: 80.

Components of the Axial Skeleton

Skull: 22 bones.
Vertebral Column: 24 vertebrae, sacrum, and coccyx.
Thoracic Cage: Comprises 12 pairs of ribs and the sternum.
Associated Bones: Includes hyoid bone and ear ossicles (3 in each ear).

Appendicular Skeleton

Includes all bones of the upper and lower limbs.
Contains bones that attach limbs to the axial skeleton.
Total bones in the appendicular skeleton: 126.

Overview of the Skull

Cranium: Skeletal structure of the head that supports the face and protects the brain.
Subdivisions:
- Facial Bones: Support facial structures and form the nasal cavity; enclose eyeballs and support teeth.
- Brain Case (Cranial Vault): Surrounds and protects the brain and houses ear structures.

Composition of the Skull

Total bones: 22 individual bones, with 21 being immobile.
The mandible is the only movable bone.

Anterior View of the Skull

Facial Features: Provide support for eyes and facial structures.
Orbits: Bony sockets for eyeballs and related muscles.
Supraorbital Margin: Contains the Supraorbital Foramen for sensory nerve passage to the forehead.
Infraorbital Foramen: Supplies anterior face sensory nerves below the orbit.

Nasal Cavity Structure

Divided by the nasal septum: upper portion formed by the perpendicular plate of the ethmoid bone; lower portion by vomer bone.
Nasal Conchae:
- Inferior Nasal Concha: Independent bone.
- Middle and Superior Nasal Conchae: Parts of the ethmoid bone.

Lateral View of the Skull

Brain Case: Large upper portion protecting the brain.
Jaws and Teeth: Upper and lower jaws with teeth dominate the lower portion.
Zygomatic Arch: Bony arch from cheek to ear canal, formed by the Temporal Process and Zygomatic Process.

Overview of the Brain Case

Contains and protects the brain.
Divided into:
- Cranial Cavity: Interior space for the brain.
- Calvaria (Skullcap): Rounded top of the skull.
- Base of the Skull: Complex area for cranial nerves, blood vessels, and the spinal cord.
- Cranial Fossae: Subdivided into anterior, middle, and posterior fossae.

Bones of the Brain Case

Total bones: 8 (paired and unpaired).
Paired Bones: Parietal and temporal bones.
Unpaired Bones: Frontal, occipital, sphenoid, and ethmoid bones.

Specific Bones of the Brain Case

Parietal Bone: Most of the upper lateral side, borders the frontal, temporal, and occipital bones.
Temporal Bone: Forms the lower lateral side, includes the flattened squamous portion and the zygomatic process.

Description

Explore the Axial Skeleton in this quiz, which covers key components of the skeletal system, including bones, cartilages, and ligaments. With a focus on the primary functions, this quiz will help you understand how the axial skeleton supports and shapes the human body.