B.1.2 Structure and function of connective tissues and joints Notes

Connective Tissues and Joints

Structure and Function in Movement

Imagine you're running to catch a bus. Your legs push off the ground, your arms swing for balance, and your body bends and twists to propel you forward. But have you ever wondered what makes all of this movement possible? Beneath the surface, a network of connective tissues and joints works together to stabilize your body while allowing for fluid motion. In this section, you’ll discover how these structures, connective tissues and joints, are uniquely designed to enable movement while maintaining stability.

Connective Tissues: The Building Blocks of Movement

Connective tissues are the "support team" of your musculoskeletal system. They provide structure, stability, and flexibility, enabling movement while protecting your body from injury.

Bone:

Bones form the structural foundation of your body, providing a framework that supports movement. They serve as attachment points for muscles and act as levers during motion. Additionally, bones serve to store yellow bone marrow. For example, when you bend your arm at the elbow, the bones of your forearm act as levers, moving in response to muscle contractions.

Ligaments:

Ligaments are strong, fibrous bands of connective tissue that connect bones to other bones. Their primary role is to stabilize joints by limiting excessive movement.

Cartilage:

Cartilage is a smooth, flexible tissue that reduces friction and absorbs shock at your joints. It covers the ends of bones in synovial joints, like your knee and hip, ensuring smooth movement. Without cartilage, your bones would grind against each other, causing pain and damage.

Tendons:

Tendons are tough, fibrous tissues that connect your muscles to your bones. When a muscle contracts, the tendon transmits the force to the bone, causing movement. For example, your Achilles tendon connects your calf muscles to your heel bone, enabling you to push off the ground while walking or running.

Types of Articulations: The Joints That Make Movement Possible

Joints, or articulations, are where two or more bones meet. Their structure determines the range of motion and stability they provide. There are three main types of joints: fibrous, cartilaginous, and synovial.

Fibrous Joints: Immovable Connections

Fibrous joints are held together by dense connective tissue and allow no movement. Examples include the sutures of your skull, which protect your brain by forming a rigid, immovable structure.

Cartilaginous Joints: Limited Movement

Cartilaginous joints are connected by cartilage and allow limited movement. An example is the intervertebral discs in your spine, which provide flexibility while absorbing shock.

Synovial Joints: The Movers

Synovial joints are the most common and versatile type of joint in your body. They allow a wide range of motion, from bending and twisting to rotation. These joints are characterized by:

• A synovial cavity filled with lubricating fluid.
• A joint capsule that encloses the cavity.
• Articular cartilage that reduces friction.

Classes of Synovial Joints:

Synovial joints are further classified based on their structure and the type of movement they allow. Let’s explore the six main types:

1. Ball-and-Socket Joints: Allow movement in all directions, including rotation (e.g., shoulder, hip).
2. Hinge Joints: Permit movement in one plane, like a door hinge (e.g., elbow, knee).
3. Pivot Joints: Enable rotational movement (e.g., atlas and axis in your neck).
4. Saddle Joints: Allow movement in two planes while maintaining stability (e.g., thumb joint).
5. Condyloid Joints: Allow movement in two planes but no rotation (e.g., wrist).
6. Gliding Joints: Permit sliding motions (e.g., small bones in the wrist and foot).