Answer:

The correct answer is option 'B', the synovial membrane.

The synovial membrane is a specialized connective tissue membrane that lines the inner surface of joint cavities. It is responsible for secreting synovial fluid, a watery fluid that lubricates and cushions the joint.

Function of the synovial membrane:
The synovial membrane has several important functions in the joint:

1. Synovial fluid production: The synovial membrane secretes synovial fluid, which is a viscous, lubricating fluid. This fluid helps to reduce friction between the articular surfaces of the joint during movement.

2. Lubrication: The synovial fluid acts as a lubricant, allowing for smooth movement of the joint. It reduces friction and wear between the articulating surfaces of the bones.

3. Cushioning: The synovial fluid also acts as a shock absorber, providing cushioning and protecting the joint from excessive forces and impact during movement.

4. Nutrient supply: The synovial fluid carries nutrients to the articular cartilage, which does not have a direct blood supply. This helps to maintain the health and function of the cartilage.

5. Waste removal: The synovial fluid also helps to remove metabolic waste products from the joint, contributing to the overall health and function of the joint.

Composition of synovial fluid:
Synovial fluid is a clear, viscous fluid composed of several components, including:

1. Water: Water makes up the majority of synovial fluid, providing the fluidity and lubrication required for joint movement.

2. Hydrated hyaluronic acid: Hyaluronic acid is a high-molecular-weight glycosaminoglycan that helps to maintain the viscosity and lubricating properties of the synovial fluid.

3. Proteins: Synovial fluid contains various proteins, including albumin and globulins, which help to maintain the osmotic balance and provide nourishment to the articular cartilage.

4. Cells: The synovial fluid may contain a small number of white blood cells, which are responsible for the immune response and inflammation regulation within the joint.

In conclusion, the synovial membrane secretes synovial fluid, which plays a crucial role in lubricating and cushioning the joint. This fluid helps to reduce friction, protect the joint from excessive forces, provide nutrients to the cartilage, and remove waste products. The synovial membrane and synovial fluid are essential for maintaining the health and proper function of the joint.