Lymphatic System and Immunity Flashcards

Flashcards covering the anatomy and physiology of the lymphatic system, fluid pathways, lymphoid organs, and innate vs. adaptive immune responses.

What are the three major functions of the Lymphatic System?

Fluid balance, immune protection, and absorption of fats.

What is lymph most chemically related to, and why must it return to the blood?

Lymph is most similar to interstitial fluid, which comes from blood plasma. It has less protein than plasma. Returning lymph to the blood prevents fluid buildup (edema) and helps maintain blood volume.

What is lymphedema, and what causes it?

Lymphedema is swelling caused by a buildup of fluid in the interstitial space when the lymphatic system cannot properly drain excess fluid.

What is the complete pathway of lymphatic fluid from the interstitial space back into the blood?

Interstitial space → Lymph Capillaries → Afferent Lymph Vessels → Lymph Nodes → Efferent Lymph Vessels → Lymphatic Trunks → Lymphatic Ducts (Thoracic Duct or Right Lymphatic Duct) → Subclavian Veins → Superior Vena Cava.

What are the two major lymphatic ducts, and what body regions does each drain?

Right lymphatic duct: drains the right side of the head and neck, right chest, and right arm.

Thoracic duct: drains the rest of the body.

How is a lymphatic capillary similar to and different from a blood capillary, and how does lymph enter it?

Both have thin walls made of a single layer of endothelial cells. Lymphatic capillaries are blind-ended and more permeable. Gaps between their cells form flap-like openings that allow interstitial fluid to enter and become lymph.

What are lacteals, and why do fats enter them instead of blood capillaries?

Lacteals are lymphatic capillaries in the villi of the small intestine. Fats are packaged into chylomicrons, which are too large to enter blood capillaries, so they enter lacteals instead.

What are the three locations of tonsils in the pharynx?

The Palatine tonsils (located on each side of the soft palate), the single Pharyngeal tonsil or Adenoid (located behind the nose), and the Lingual tonsils (located on the posterior portion of the tongue).

What is the function of the thymus in the lymphatic system, and what happens to it with age?

The thymus is where T cells mature. It is most active during childhood and shrinks and becomes less active after puberty.

Where is the spleen located, and what are the functions of its red pulp and white pulp?

The spleen is located in the upper left abdomen near the stomach. Red pulp removes old or damaged red blood cells, while white pulp contains lymphocytes that help fight pathogens in the blood.

What is MALT, and where is it found in the body?

MALT (Mucosa-Associated Lymphoid Tissue) is lymphatic tissue found in mucous membranes, especially in the digestive, respiratory, and urogenital tracts. It contains lymphocytes that help protect against pathogens.

Where are Axillary, Cervical, and Mesenteric lymph nodes located?

Axillary nodes are around the armpits; Cervical nodes are around the neck; Mesenteric (intestinal) nodes are located between the two layers of peritoneum forming the mesentery around the small intestines.

What is the difference between innate and adaptive immunity?

Innate immunity is present at birth, non-specific, responds quickly, and has no memory. Adaptive immunity is specific, responds more slowly at first, and has memory, allowing a faster response after future exposure.

What are the major surface barriers of the body, and how do they prevent infection?

Physical barriers like skin and mucous membranes block pathogens. Chemical barriers like stomach acid, lactic acid, and lysozyme in tears and sweat help kill pathogens. Not all barriers are physical tissues.

What cells and proteins are important in the innate immune response?

Important cells include neutrophils, macrophages, dendritic cells, NK cells, mast cells, basophils, and eosinophils. Important proteins include complement proteins.

What role do Neutrophils play in innate immunity?

They are the most abundant White Blood Cell and the first to arrive at damaged tissue, ingesting pathogens and debris through phagocytosis while releasing chemicals that increase tissue damage and inflammation.

What is the difference between a monocyte and a macrophage?

A monocyte circulates in the blood. After it enters body tissues, it can develop into a macrophage. Macrophages engulf pathogens and debris by phagocytosis and can present antigens to other immune cells.

What do basophils and mast cells release, and what are their functions?

They release histamine, which causes vasodilation and increased capillary permeability during inflammation. They also release heparin, which helps prevent blood clotting.

What are the functions of eosinophils?

Eosinophils mainly fight parasitic infections and are involved in allergic and inflammatory responses.

Why are dendritic cells considered the bridge between innate and adaptive immunity?

Dendritic cells capture antigens from pathogens and present them to T cells, helping activate the adaptive immune response.

What is the role of Natural Killer (NK) cells in innate immunity?

NK cells kill virus-infected cells and abnormal cells by causing them to undergo cell death (apoptosis).

What is the functional distinction between Afferent and Efferent lymph vessels in a Lymph Node?

Afferent lymph vessels carry lymph fluid into the node to be filtered, while Efferent lymph vessels carry filtered lymph fluid out of the node.

What is general lymphatic tissue made of?

Lymphatic tissue is made of reticular connective tissue (reticular fibers) containing immune cells such as lymphocytes, macrophages, and dendritic cells.

Where are Peyer’s patches located, and what is their function?

Peyer’s patches are lymphatic tissue in the small intestine, especially the ileum. They monitor intestinal pathogens and help start immune responses.

What is the function of lymph nodes, and what does an inflamed or swollen lymph node usually mean?

Lymph nodes filter lymph and contain immune cells that attack pathogens. Swollen lymph nodes usually mean immune cells are responding to an infection.

Why is it called an “immune response” instead of one single “immune system,” and how is the lymphatic system involved?

It is called an immune response because many cells, tissues, organs, and proteins work together to defend the body. The lymphatic system supports this response by transporting lymph and housing immune cells.

What are the three lines of defense against infection?

1st line: surface barriers like skin and mucous membranes.

2nd line: innate defenses like inflammation, phagocytes, NK cells, complement, and fever.

3rd line: adaptive immunity using B cells, T cells, antibodies, and memory.

What are complement proteins, and what do they do?

Complement proteins are blood proteins that help innate immunity by marking pathogens for destruction, increasing inflammation, and helping destroy pathogens.

What are the cardinal signs of inflammation, and what causes them?

Redness and heat come from increased blood flow; swelling comes from fluid entering the tissue; pain comes from inflammatory chemicals and pressure from swelling.

What are the basic steps of inflammation, and what is an inflammatory mediator?

Injury or infection causes cells such as mast cells to release inflammatory mediators like histamine → blood vessels dilate and become more permeable → WBCs and proteins enter the tissue → pathogens and debris are removed → tissue begins to heal. An inflammatory mediator is a chemical that promotes inflammation.

What is a fever, how does the hypothalamus control it, and why do you feel cold when a fever rises but hot when it falls?

A fever is a controlled rise in body temperature. Pyrogens cause IL-1, IL-6, and TNF to increase prostaglandin E2 (PGE2), which raises the hypothalamus’s temperature set point. When the set point rises, you feel cold and may shiver. When it returns to normal, you feel hot and may sweat.