MCAT Biology : Lymphatic System
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Example Questions
Example Question #3 : Other Lymphatic Physiology
Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is called negative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.
As the figure below shows, immune cells typically originate in the bone marrow. Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.
B-cells are primarily activated in lymph nodes, similar in some respects to T-cell activation in the thymus. Which of the following is true of the lymphatic system?
I. It drains excess fluid from interstitial spaces
II. It has one-way valves similar to those in veins
III. It is actively pumped by skeletal muscle contraction
II, only
I and III
I, II, and III
II and III
I and II
I, II, and III
All of these statements are true of the lymphatic system. Without a dedicated pump of its own, it relies on skeletal muscle contraction in adjacent muscles and the presence of one-way valves to remove excess interstitial fluid and bring it to lymph nodes, where the immune system can be activated.
Example Question #1 : Other Lymphatic Physiology
Which of the following is NOT a function of the lymphatic system?
Transport of digested fats to the blood stream
Returning interstitial fluid back to the blood stream
Secretion of aminopeptidase into the small intestine
Storage of memory B-cells
Secretion of aminopeptidase into the small intestine
The lymphatic system is important for the return of interstitial fluid back into the blood stream. Fluids that escape vessels and capillaries that would otherwise remain between tissue are returned to the bloodstream by the lymphatic system. Also, lymph nodes play a key role in the immune system, as they are storage centers for memory cells that have been produced as a result of an antigen binding to a B-cell during a primary response. Finally, the lymphatic system is also involved in the transport of insoluble formations of fats called chylomicrons to the blood stream. The lymphatic system plays no role in the secretion of aminopeptidase; therefore, that is the correct answer.
Example Question #1 : Other Lymphatic Physiology
All of the following are functions of the lymphatic system except for which answer choice?
Delivers fat soluble nutrients in the form of chylomicrons from the gut to systemic circulation
Delivers extracellular fluid back to systemic circulation
Delivers antigens and microbes to lymph nodes, where they can be detected by immune cells
Delivers water soluble nutrients from the gut to systemic circulation
Delivers water soluble nutrients from the gut to systemic circulation
Water-soluble nutrients are generally absorbed directly into the blood stream via various mechanisms, including but not limited to facilitated diffusion and active transport. Long-chain fatty acids, cholesterol, triglycerides, and large-fat soluble drugs are packaged into chylomicrons and taken up by the lymphatics in the gut before they are delivered to systemic circulation.
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