Lymphatic and Immune Systems Flashcards
Antibodies, antigens, macrophages, monocytes, neutrophils…the immune system is complicated, but understanding its components is essential for many MCAT questions and passages. This deck covers all of these topics, as well complex concepts like clonal selection and blood transfusions. Use these cards to master the lymphatic and immune systems as tested on the MCAT.
Describe the general structure of the lymphatic system.
The lymphatic system is a network of vessels that transport a fluid called lymph. Lymph nodes, or small clusters of lymphatic tissue, are positioned along these vessels.
Other organs, such as the thymus and the spleen, also contain lymphoid tissue.
What are the characteristics of a lymph vessel?
Like veins, lymph vessels contain valves and have thin walls composed of smooth muscle and connective tissue. However, lymph vessels are more flexible to accommodate excess fluid.
Lymph vessels vary in size, like those of the circulatory system. Smaller lymph capillaries give rise to larger vessels.
What are the characteristics of a lymph node?
Lymph nodes are small structures, oval in shape, and positioned along lymph vessels. They contain immune cells, namely lymphocytes and macrophages.
Lymph nodes function to filter the fluid that is being transported through the lymphatic system.
Where does lymph originate from, and what are its main components?
Lymph is composed of excess fluid that has diffused into the tissues from capillaries. As a result, its composition is similar to plasma.
More specifically, lymph mainly contains water, lymphocytes, and proteins. It also transports fats that have been absorbed in the form of chylomicrons.
The lymphatic system serves what main function apart from its immune role?
The lymphatic system drains excess interstitial fluid from the tissues. After filtration through lymph nodes, this fluid is eventually returned to the bloodstream.
This activity minimizes edema, or swelling due to fluid accumulation.
Define:
lacteal
A lacteal is a small lymphatic vessel found in a villus of the small intestinal epithelium.
Lacteals play a major role in the absorption of fats, which are first taken up by the lymphatic system in the form of chylomicrons.
Through which vessel does lymph return to venous circulation?
Lymph enters venous circulation through the thoracic duct.
The thoracic duct, a large lymphatic vessel, is found in the upper region of the chest. It drains into the left subclavian vein.
What is the difference between a closed and open circulatory system, and which type does the lymphatic system exemplify?
A closed circulatory system is comprised of a complete loop of vessels, while an open system is open-ended and drains fluid from one location into another.
The human lymphatic system is open, while the main circulatory system is closed.
What is the difference between innate and specific immunity?
Innate immunity provides a broad line of defense against foreign material. Its response to pathogens is general, not specific to the identity of the pathogen.
Specific immunity is highly specialized, using immunological memory of previous infections to respond to certain pathogens.
Macrophages, neutrophils, mast cells, natural killer cells, and dendritic cells are involved in innate immunity. T and B lymphocytes are involved in specific immunity.
Give another name for innate immunity.
Innate immunity is also known as nonspecific immunity.
Which of the following is not directly involved in the innate immune response?
- Macrophages
- Skin
- B lymphocytes
- Mucus in the respiratory tract
B lymphocytes do not play a major role in innate immunity. The other choices all provide a first line of defense against a wide variety of pathogens.
B lymphocytes, on the other hand, produce antibodies. These products are highly specialized to recognize certain antigens, and form a large part of specific immunity.
What is phagocytosis?
Phagocytosis is the engulfment of a foreign particle by an immune cell, or phagocyte. The particle is taken up in a vesicle and can then be degraded.
This process can often involve chemotaxis, a form of movement in which a cell is drawn toward or away from specific chemical substances.
Which of the following cells can not perform phagocytosis?
- Monocytes
- Erythrocytes
- Macrophages
- Neutrophils
Erythrocytes cannot perform phagocytosis. Erythrocytes are red blood cells, which do not serve a major function in the immune system.
Neutrophils, monocytes, and macrophages all perform phagocytosis as an important part of innate immunity.
Diphenhydramine, an allergy medication, functions as an antihistamine. Which immune response is likely to be inhibited by the administration of diphenhydramine?
Diphenhydramine will inhibit the inflammatory response.
Histamine is a chemical that functions as part of the inflammatory response. Specifically, it increases capillary permeability and can lead to many common allergy symptoms.
Describe three main effects of the inflammatory response.
- Capillary permeability increases, allowing immune cells to access the infected site. This results in redness and swelling.
- The infected area becomes warm.
- The infected area is often painful due to swelling and the presence of certain chemicals.
What name is given to an adverse inflammatory response to non-pathogenic material such as animal hair or pollen?
Allergies, or immune responses to typically harmless compounds, commonly occur when the inflammatory response is overactive.
Allergies are often treated with antihistamines, which counteract a main inflammatory chemical agent.
What enzyme is found in tears and catalyzes the breakdown of bacterial cell walls?
Lysozyme
Specifically, lysozyme catalyzes the breaking of glycosidic linkages within peptidoglycan molecules. This role is part of the innate immune system.
Give another name for specific immunity.
Specific immunity is also known as adaptive or acquired immunity.
Which of the following is not directly involved in the specific immune response?
- T lymphocytes
- Macrophages
- B lymphocytes
- Antibodies
Macrophages do not play a direct role in specific, or acquired, immunity.
Specific immunity involves cells that specialize to recognize and attack a limited class of antigens. In contrast, macrophages phagocytose a wide variety of pathogens and foreign particles.
Define:
leukocyte
A leukocyte, also known as a white blood cell, is a cell involved in immune function.
Leukocytes are a broad category of cells, including neutrophils, monocytes, and lymphocytes, among others.
A deficiency in monocytes will likely lead to a lower-than-average number of what other type of cell?
Macrophages
Monocytes differentiate into macrophages, which are phagocytic cells that act as a part of the innate immune response.
Name the most abundant leukocyte found in the blood.
The most abundant leukocytes are neutrophils, which constitute 50-70% of all white blood cells by number.
As one of the first cell types to reach the site of an infection, neutrophils are the main component of pus. Like macrophages, they can perform phagocytosis.