BIO201 – Topic 4: The Skeletal System
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
4.1 Introduction to the Skeletal System
The skeletal system is the framework of bones and connective tissues that provide structure,
protection, and movement to the human body. It supports the body’s shape, safeguards internal
organs, and works with the muscular system to produce motion.
4.2 Functions of the Human Skeleton
1. **Support:** Provides shape and structural support to the body. 2. **Protection:** Shields vital
organs such as the brain (skull), heart, and lungs (rib cage). 3. **Movement:** Serves as an
attachment point for muscles, facilitating motion. 4. **Mineral Storage:** Stores essential minerals
like calcium and phosphorus. 5. **Blood Cell Production:** Bone marrow produces red and white
blood cells. 6. **Fat Storage:** Yellow marrow stores fats for energy.
4.3 Classification of Bones
Bones are classified based on their shapes and functions as follows: 1. **Long Bones** – e.g.,
femur, humerus; for movement and support. 2. **Short Bones** – e.g., carpals, tarsals; provide
stability and strength. 3. **Flat Bones** – e.g., skull, ribs; protect internal organs. 4. **Irregular
Bones** – e.g., vertebrae; complex shapes for support and protection. 5. **Sesamoid Bones** –
e.g., patella; reduce friction at joints.
4.4 Structure of a Typical Bone
A typical long bone consists of: - **Diaphysis (shaft):** The central tubular region made of compact
bone. - **Epiphysis:** The enlarged ends containing spongy bone and red marrow. -
**Periosteum:** A tough membrane covering the bone’s outer surface. - **Medullary Cavity:** The
inner hollow space containing yellow marrow. - **Articular Cartilage:** Smooth covering at joint
surfaces reducing friction.
4.5 Types of Joints and Their Functions
Joints are points where two or more bones meet. They are classified as: 1. **Fixed (immovable):**
Found in the skull. 2. **Slightly movable:** Found in the vertebral column. 3. **Freely movable
(synovial):** Found in limbs, enabling various movements such as hinge (elbow), ball-and-socket
(shoulder), and pivot (neck).
4.6 The Human Axial Skeleton
The axial skeleton forms the central axis of the body and includes: - Skull (protects the brain) -
Vertebral column (supports the trunk and protects the spinal cord) - Rib cage and sternum (protect
vital organs and assist in breathing).
4.7 The Human Appendicular Skeleton
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
4.1 Introduction to the Skeletal System
The skeletal system is the framework of bones and connective tissues that provide structure,
protection, and movement to the human body. It supports the body’s shape, safeguards internal
organs, and works with the muscular system to produce motion.
4.2 Functions of the Human Skeleton
1. **Support:** Provides shape and structural support to the body. 2. **Protection:** Shields vital
organs such as the brain (skull), heart, and lungs (rib cage). 3. **Movement:** Serves as an
attachment point for muscles, facilitating motion. 4. **Mineral Storage:** Stores essential minerals
like calcium and phosphorus. 5. **Blood Cell Production:** Bone marrow produces red and white
blood cells. 6. **Fat Storage:** Yellow marrow stores fats for energy.
4.3 Classification of Bones
Bones are classified based on their shapes and functions as follows: 1. **Long Bones** – e.g.,
femur, humerus; for movement and support. 2. **Short Bones** – e.g., carpals, tarsals; provide
stability and strength. 3. **Flat Bones** – e.g., skull, ribs; protect internal organs. 4. **Irregular
Bones** – e.g., vertebrae; complex shapes for support and protection. 5. **Sesamoid Bones** –
e.g., patella; reduce friction at joints.
4.4 Structure of a Typical Bone
A typical long bone consists of: - **Diaphysis (shaft):** The central tubular region made of compact
bone. - **Epiphysis:** The enlarged ends containing spongy bone and red marrow. -
**Periosteum:** A tough membrane covering the bone’s outer surface. - **Medullary Cavity:** The
inner hollow space containing yellow marrow. - **Articular Cartilage:** Smooth covering at joint
surfaces reducing friction.
4.5 Types of Joints and Their Functions
Joints are points where two or more bones meet. They are classified as: 1. **Fixed (immovable):**
Found in the skull. 2. **Slightly movable:** Found in the vertebral column. 3. **Freely movable
(synovial):** Found in limbs, enabling various movements such as hinge (elbow), ball-and-socket
(shoulder), and pivot (neck).
4.6 The Human Axial Skeleton
The axial skeleton forms the central axis of the body and includes: - Skull (protects the brain) -
Vertebral column (supports the trunk and protects the spinal cord) - Rib cage and sternum (protect
vital organs and assist in breathing).
4.7 The Human Appendicular Skeleton
