14.2 Musculoskeletal System of Humans
The human musculoskeletal system provides shape, support, protection, and allows body movement. It consists of the skeletal system—divided into the axial and appendicular skeletons—as well as joints, skeletal muscles, tendons, and ligaments. Working together, these structures enable coordinated locomotion and physical activity.
Learning Objectives
- Identify the components of the axial skeleton and appendicular skeleton.
- Describe the structure of different types of vertebrae (cervical, thoracic, lumbar, sacral, and caudal).
- Compare and contrast cervical, thoracic, and lumbar vertebrae.
- Categorise joints into immovable, slightly moveable, and freely moveable joints.
- Describe the structure and function of freely moveable joints (ball-and-socket and hinge joints).
- Explain the roles and characteristics of skeletal muscles, tendons, and ligaments in movement.
Comparison of Vertebrae and Joint Structures
Distinguish cervical, thoracic, and lumbar vertebrae, and understand the functional anatomy of synovial joints.
Short Explanation
Axial Skeleton
Comprises the skull, vertebral column, ribs, and sternum.
Appendicular Skeleton
Includes the pectoral girdle, pelvic girdle, upper limbs, and lower limbs.
Vertebral Column
Consists of individual vertebrae separated by cartilage discs. Each vertebra has a neural canal that houses and protects the spinal cord.
Joints
A joint is a point where two or more bones meet, or where cartilage and bones meet. Joints can be immovable, slightly moveable, or freely moveable.
Skeletal Muscles, Tendons, and Ligaments
Skeletal muscles work in antagonistic pairs. Tendons connect muscle to bone, while ligaments connect bone to bone.
Freely Moveable Joints
Synovial joints contain a fibrous capsule, cartilage, synovial membrane, and synovial fluid. Examples include ball-and-socket joints and hinge joints.
Try to Answer First
Answer in your mind, then press “Check Answer”.
Name the four main bone groups that make up the axial skeleton.
Which vertebra possesses an odontoid process, and what is its specific function?
Explain why tendons must be inelastic while ligaments must be elastic.
Common Mistakes
- Confusing the attachments of tendons and ligaments: tendons connect muscle to bone, whereas ligaments connect bone to bone.
- Thinking tendons are elastic. Tendons are inelastic (non-elastic) but flexible; ligaments are elastic.
- Assuming all vertebrae possess a centrum, forgetting that the atlas vertebra has no centrum.
- Mixing up the movement planes of ball-and-socket joints (rotational in all directions) and hinge joints (single plane movement).
Concept Misunderstandings
Tendons stretch like rubber bands to move bones.
Tendons are non-elastic so that when a muscle contracts, all tensile force is transferred directly and immediately to the bone without being absorbed by stretching.
Both atlas and axial vertebrae look like typical cervical vertebrae.
The atlas vertebra has a large neural canal and no centrum, while the axial vertebra has a prominent odontoid process.
Synovial fluid is present in all types of joints.
Synovial fluid is only present in freely moveable (synovial) joints, not in immovable joints (sutures) or slightly moveable cartilaginous joints.
Summary
- The human skeleton is divided into the axial skeleton (skull, ribs, sternum, vertebral column) and the appendicular skeleton (girdles and limbs).
- The vertebral column has distinct regions: cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), and caudal (4 fused).
- The atlas lacks a centrum; the axial has an odontoid process; cervical vertebrae have transverse foramina; thoracic have rib facets; lumbar have the largest centrum.
- Joints are classified as immovable (suture), slightly moveable (intervertebral cartilage discs), and freely moveable (ball-and-socket, hinge).
- Synovial joints contain a fibrous capsule, cartilage, synovial membrane, and synovial fluid for lubrication and shock absorption.
- Antagonistic muscles work in pairs (flexor and extensor). Tendons (inelastic) connect muscle to bone; ligaments (elastic) connect bone to bone.
Short Activity
Objective: identify vertebrae characteristics, joint structures, and the roles of muscles, tendons, and ligaments.
A. Objective Quiz
Which characteristic uniquely distinguishes a cervical vertebra from thoracic and lumbar vertebrae?
What is the function of cartilage found at the ends of bones in a synovial joint?
B. Fill in the Blanks
The tissue that connects muscle to bone and consists of strong, non-elastic fibres is called a .
The first cervical vertebra which lacks a centrum and articulates directly with the skull is the vertebra.
C. Matching / Drag and Drop
Match each musculoskeletal structure to its correct description or function. On a phone, tap a choice first, then tap the matching box. Tap the Answer Choices area to return a selected item.
C. Match the Structure to Its Function / Description
Write the correct structure next to each description.
| Function / Description | Structure |
|---|---|
| 1. Strong and elastic connective tissue bundle that connects bone to bone. | |
| 2. Joint that permits movement in one plane, such as the knee and elbow. | |
| 3. Joint that allows rotational movement in all directions, such as the hip and shoulder. | |
| 4. The largest and strongest vertebra with a massive centrum to bear lower back weight. |
Answer choices: Ligament • Hinge joint • Ball-and-socket joint • Lumbar vertebra
