MCAT Biology : Other Lymphatic Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #18 : Immune And Lymphatic Systems

Which of the following is not a function of the lymphatic system?

Possible Answers:

Present antigens to B-cells

Synthesize red blood cells

Produce B-cells

Drain interstitial fluid

Correct answer:

Synthesize red blood cells

Explanation:

The lymphatic system has many purposes, including draining the 10% of interstitial fluid that is not reabsorbed by the capillaries, housing the lymph nodes that produce B-cells, and serving as a migration site for macrophages that present antigens to B-cells to initiate an immune system reaction.

The bone marrow is responsible for producing red blood cells, and for allowing B-cells to mature.

Example Question #19 : Immune And Lymphatic Systems

Which of the following is not a purpose of the lymphatic system?

Possible Answers:

Filter blood

Regulate body temperature

Remove fluid from interstitial space

Transport lymph back to the heart

Bring interstitial fluid back to systemic circulation

Correct answer:

Regulate body temperature

Explanation:

The lymphatic system carries lymph, which is a colorless fluid containing white blood cells, to help the body remove excess interstitial fluid. Fluids from the blood leak out of the gaps between capillary epithelium and must be returned to circulation to prevent accumulation. The lymphatic system collects this fluid and passes it through lymph nodes, which house lymphocytes that screen the fluids for foreign antigens. The lymphatic vessels then carry the fluids to the heart, releasing the lymph back into circulation via the right atrium.

Example Question #20 : Immune And Lymphatic Systems

Which of the following is not a function of the lymphatic system?

Possible Answers:

It filters excess interstitial fluid

It provides the maturation site for T-cells

It screens the blood for microbes

It detoxifies the blood

It helps transport fats to the veins of the neck

Correct answer:

It detoxifies the blood

Explanation:

The liver is primarily responsible for the detoxification of the blood.

All other listed options are the primary roles of the lymphatic system. Digested fats are emulsified in the small intestine, then transported via lymph (rather than blood). They enter the blood stream through the subclavian vein. The lymph also contains a large number of lymphocytes, or white blood cells, which can screen for microbes. Excess interstitial fluid is transferred to the lymph via leaky capillaries. The thymus, a primary lymphoid organ, is responsible for T-cell maturation.

Example Question #1 : 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.

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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

Possible Answers:

II, only

I, II, and III

I and III

I and II

II and III

Correct answer:

I, II, and III

Explanation:

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 #22 : Immune And Lymphatic Systems

Which of the following is NOT a function of the lymphatic system?

Possible Answers:

Returning interstitial fluid back to the blood stream

Secretion of aminopeptidase into the small intestine

Storage of memory B-cells

Transport of digested fats to the blood stream

Correct answer:

Secretion of aminopeptidase into the small intestine

Explanation:

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 #2 : Other Lymphatic Physiology

All of the following are functions of the lymphatic system except for which answer choice?

Possible Answers:

Delivers extracellular fluid back to systemic circulation

Delivers fat soluble nutrients in the form of chylomicrons from the gut 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

Correct answer:

Delivers water soluble nutrients from the gut to systemic circulation

Explanation:

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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