Question

Name the part of a synovial joint with each of the following functions: (pp. 129, 132) a. Fluid within the joint cavity that prevents friction b. Encloses the joint in a strong sheath c. Provides a smooth surface on bone surfaces d. Lines the joint capsule and secretes synovial fluid

Short answer

a. Preventing friction within the joint cavity b. Enclosing the joint in a strong sheath c. Providing a smooth surface on bone surfaces d. Lining the joint capsule and secreting synovial fluid Answer: a. Synovial fluid b. Joint capsule c. Articular cartilage d. Synovial membrane (synovium)

Step-by-step solution

a. Fluid within the joint cavity that prevents friction

The fluid within the joint cavity that prevents friction is called "synovial fluid". Synovial fluid is a thick, viscous substance that fills the joint cavity and helps lubricate and cushion the joint, reducing friction between the bones.

b. Encloses the joint in a strong sheath

The part responsible for enclosing the synovial joint in a strong sheath is called the "joint capsule". The joint capsule is a fibrous and strong connective tissue that surrounds the joint, providing support and stability.

c. Provides a smooth surface on bone surfaces

The part that provides a smooth surface on bone surfaces is known as "articular cartilage". Articular cartilage is a specialized type of connective tissue that covers the ends of the bones in synovial joints, allowing the bones to move smoothly against each other and absorb shock during motion.

d. Lines the joint capsule and secretes synovial fluid

The part that lines the joint capsule and secretes synovial fluid is called the "synovial membrane" or "synovium". The synovial membrane is a thin layer of connective tissue that lines the inner surface of the joint capsule. Its main function is to produce and maintain the synovial fluid present in the joint cavity.

Key concepts

Synovial Fluid

Synovial fluid is a vital component of synovial joints, serving the essential role of reducing friction between articulating bone surfaces. It is a thick and viscous fluid, sometimes described as having the consistency of egg whites. This unique texture is due to the presence of hyaluronic acid, which is responsible for its lubricating properties. Synovial fluid not only helps lubricate the joints but also nourishes the articular cartilage. It supplies oxygen and nutrients while removing metabolic waste from the cartilage.
The fluid is constantly recycled and maintained by the synovial membrane to ensure efficient joint function. Without ample synovial fluid, joints would suffer from increased wear and tear, leading to painful movement conditions like arthritis.

Joint Capsule

A joint capsule is a key component that encloses a synovial joint in a strong sheath. It is composed of an outer fibrous layer and an inner synovial membrane. The fibrous layer is made of dense connective tissue, giving it strength and flexibility to protect the joint. This capsule helps keep the joint in alignment and prevents dislocation during movement.

• The outer layer: tough and resilient, maintaining joint stability.
• The inner layer (synovial membrane): delicate and rich in blood vessels, responsible for producing synovial fluid.

The joint capsule's unique combination of toughness and flexibility allows for a wide range of motion while securely holding the joint components in place.

Articular Cartilage

Articular cartilage is specialized connective tissue that covers the ends of bones within synovial joints, providing a smooth, white, and glistening surface. Its primary function is to reduce friction and absorb shock during movement. This cartilage is avascular, meaning it lacks blood vessels and relies on synovial fluid for nutrients and waste removal.

• Smooth surface: ensures bones can move without grinding against each other.
• Shock absorption: mitigates impact during physical activities like walking or jumping.

Healthy articular cartilage is essential for pain-free and efficient joint movement. Damage to this cartilage can lead to joint disorders such as osteoarthritis.

Synovial Membrane

The synovial membrane, also known as the synovium, is a delicate tissue lining the inner surface of the joint capsule. Its primary role is to produce synovial fluid, which ensures the smooth functioning of the joint. This membrane is rich in blood vessels and nerves, allowing it to efficiently maintain and repair the joint environment.
The synovial membrane actively filters blood plasma to create synovial fluid, carefully balancing production to avoid excess fluid that could lead to swelling. By maintaining the synovial fluid's viscosity and composition, the synovial membrane plays a crucial part in joint health and mobility. Its integrity is vital for preventing inflammatory conditions that can impair joint function.