Test: Lymphatic System - 1 - MCAT MCQ

The primary functions of the lymphatic system include transporting excess interstitial fluid, absorbing dietary fats through lacteals in the small intestine, and filtering and removing cellular waste, pathogens, and foreign substances through lymph nodes. The production of red blood cells occurs in the bone marrow, not in the lymphatic system.

The thymus is the primary organ of the lymphatic system responsible for the maturation of T cells, a type of lymphocyte involved in cell-mediated immunity. The spleen filters blood and plays a role in immune responses, while lymph nodes and tonsils are secondary lymphoid organs that house immune cells and help in the recognition and response to antigens.

Lymphatic vessels are similar to veins in their structure and function. Like veins, lymphatic vessels have thin walls, valves to prevent backflow, and rely on skeletal muscle contractions and respiratory movements to propel lymph fluid. Lymphatic vessels drain lymph fluid from tissues and return it to the bloodstream, similar to how veins return deoxygenated blood back to the heart.

Neutrophils are a type of white blood cell, but they are not lymphocytes. Neutrophils are granulocytes involved in the innate immune response and are responsible for phagocytosing bacteria and other foreign particles. B cells, T cells, and natural killer (NK) cells are all types of lymphocytes involved in adaptive immune responses.

The excess interstitial fluid collected by lymphatic vessels is called lymph. Lymph is a clear, colorless fluid that contains water, dissolved solutes, proteins, and immune cells. It is transported through lymphatic vessels and eventually returned to the bloodstream via the thoracic duct or right lymphatic duct.

The high concentration of fatty acid in the lymph fluid indicates that the meal contained fats. However, the absence of detectable amounts of free carbohydrates in the lymph fluid does not provide conclusive evidence about the presence or absence of carbohydrates in the meal. It is possible that carbohydrates were present in the meal but were already metabolized or absorbed by the time the lymph fluid was collected. Therefore, no definitive conclusion can be made regarding the carbohydrate content of the meal based on this data alone.

High-molecular weight proteins that are removed from the interstitial spaces by the lymphatic system are eventually emptied into the circulatory system. This occurs at the junction of the lymphatic system and the venous system. The lymphatic vessels merge with larger vessels called lymphatic ducts, and one of the main lymphatic ducts, the thoracic duct, drains into the circulatory system at the junction of the left subclavian vein and the left internal jugular vein. This allows the proteins to enter the bloodstream and be circulated throughout the body. Therefore, option 3 best describes the immediate fate of these proteins.

Increased cardiovascular capillary pressure can result in increased fluid filtration into the interstitial spaces. This increased fluid accumulation in the interstitial spaces creates a pressure gradient that promotes lymph flow. The lymphatic system acts as a drainage system, picking up the excess interstitial fluid and returning it to the circulatory system. Elevated cardiovascular capillary pressure can occur in conditions such as increased blood volume or increased cardiac output, which can increase lymph flow.

This option is correct because large lymph vessels and cardiovascular veins are not partly composed of individual epithelial cells. Lymph vessels, including the larger ones, are composed of endothelial cells that form a single-layered epithelium. In contrast, cardiovascular veins are composed of endothelial cells, smooth muscle, and connective tissue. The presence of individual epithelial cells is not a commonality between these two types of vessels.

The lining of lymphatic vessels is composed of simple squamous epithelium, also known as endothelium. This type of epithelium is made up of a single layer of flat cells that are tightly packed together. The endothelial cells form a smooth surface that allows for the easy passage of lymph fluid and immune cells through the vessel walls. Simple squamous epithelium is well-suited for the function of lymphatic vessels, as it provides minimal resistance to the flow of lymph and maintains the integrity of the vessel walls.