Lymphatic System

Question 1

Describe the first , second, and third line of immunological defenses in the body.

Answer 1

First line: innate immune repsonse; mechanical/chemical
Second line: innate IR; cellular and secretory proteins
Third Line: adaptive immune response; chronic inflammation and systemic response

Question 2

What are examples of the first line of immunological defense?

Answer 2

Mechanical/physical
- cutaneous membrane (skin)
- mucous membranes (mucosa)
Chemical (bodily fluids, pH, microbiome)
- saliva
- tears
- sweat
- sebum
- stomach acids (HCl)

Question 3

What are examples of the second line of immunological defense?

Answer 3

Cellular process - function in phagocytosis and cytotoxic killing and mediating acute inflammatory response
Secreted protein products

Question 4

What is the cellular process in the second line of defense?

Answer 4

Neutrophils are 1st to arrive and macrophages are 2nd to clear antigens via phagocytosis.
Eosinophils clear parasites via lysis and recruited by plasma proteins in blood.
Natural killer cells no longer express MHC or complement proteins.
Mast cells/basophils promote vasodilation to permit WBC entry into CT to mediate inflammation.
Dendritic cells and macrophages phagocytose and act as antigen presenting cells (APC display AG + MHC II) by migrating to lymph nodes to stimulate B/T cells.

Question 5

What are secreted protein products in the second line of defense?

Answer 5

Chemokines, cytokines interleukins - impact cell movement, mitotic division, differentiation
Antimicrobial - w/i most bodily fluids
Interferon - secreted by most cells to prevent viral replication
Complement proteins - inactive plasma proteins/enzymes synthesized by liver recruited to areas to amplify chemical signal to aid in antigen removal through innate and adaptive mechanisms

Question 6

What are innate mechanisms of complement proteins?

Answer 6

Alternative pathway: direct pathogen lysis via CPs assembling into membrane attack complex (MAC)
Opsonization: CPs coat pathogens to aid in phagocytosis
Chemotaxins: CPs recruit neutrophils and eosinophils to injury
Anaphylatoxins: CPs cause basophil and mast cell degranulation to induce inflammation

Question 7

What is an adaptive mechanism of complement proteins?

Answer 7

Classical: antigen recognized by specific Ab that are then recognized and tagged by CPs. Complement binding triggers binding of additional CPs to form membrane attack complex (MAC) that leads to lysis

Question 8

T or F: Innate and adaptive responses are independent and adaptive responses cannot result from innate immune responses.

Answer 8

False; Innate IR can lead to adaptive response

Question 9

What are the differences between innate and adaptive IRs?

Answer 9

Innate: first line of defense that results in acute inflammation and occurs at the local site of infection. Occurs within minutes to hours; no memory of encounter.
Adaptive: occurs after innate response but not resolved that involves chronic inflammation and systemic response. Occurs slower (weeks to days); primary response (slow/weak) and secondary (fast/strong - involves memory).
Long-term immunological memory (memory B and T cells)

Question 10

What are the cellular components of an adaptive response?

Answer 10

• T and B lymphocytes/plasma
• Antigen presenting cells

Question 11

What is the function of T and B lymphocytes?

Answer 11

Each lymphocyte expresses unique antigen specific receptors that recognize a specific antigen (Ag)

Question 12

What is the function of antigen presenting cells (APC)?

Answer 12

They are required for T cells to recognize Ag to initiate a specific adaptive response. APC presents Ag bound to MHC protein to specific naive lymphocyte.

Question 13

What are the secreted proteins of an adaptive immune response?

Answer 13

Antibodies produced by plasma cells
Cytokines produced by T cells

Question 14

What are the key requirements for Ag recognition by T cell?

Answer 14

• Requires APC to present Ag bound to MHC to a T cell
• Ag must be displayed on cell surface by MHC protein receptor

Question 15

What is the function of MHC I?

Answer 15

MHC I is on all nucleated cells so all cells can display Ag.

Question 16

What is the function of MHC II?

Answer 16

MHC II is only on APCs. (Ag displayed indicates presence of phagocytosed extracellular pathogen has entered the body)

Question 17

What is the difference between humoral immunity and cellular immunity?

Answer 17

Both adaptive defenses where humoral immunity involves B cells than antibodies. Cellular immunity involves T cells.

Question 18

What is the difference between acquired immunity and innate immunity?

Answer 18

Acquired (adaptive) immunity is produced by prior exposure or antibody production. Innate Immunity is genetically determined – no prior exposure or antibody production is involved.

Question 19

What is the difference between active immunity and passive immunity?

Answer 19

Active immunity is produced by antibodies that develop in response to antigens (immune response). Passive immunity is produced by transfer of antibodies from another person.

Question 20

What is the difference between naturally acquired immunity and induced active immunity?

Answer 20

Naturally acquired immunity develops after exposure to antigens in environment. Induced active immunity develops after administration of antigen to prevent disease (artificial).

Question 21

What is the difference between induced passive immunity and natural passive immunity?

Answer 21

Induced passive immunity is conferred by administration of antibodies to combat infection. Natural passive immunity is conferred by transfer of maternal antibodies across placenta or in breast milk.

Question 22

How is lymphatic fluid created?

Answer 22

It is the filtrate of plasma that contains waste, pathogens, WBC (lymphocytes). It contains no RBCs and is low in protein. This happens when fluid leaves the capillary at the arterial end and enters the CT due to higher pressure inside the vessel than in CT (filtration). 90% of the fluid re-enters at the venous end of the capillary due to high osmotic blood pressure and low hydrostatic pressure inside the vessel (reabsorption). The remaining 10% of fluid forms lymph fluid.

Question 23

What is the function of the lymphatic circulatory system?

Answer 23

• Absorbs fats (chylomicrons) and fat-soluble vitamins from small intestine via lymphatic capillaries (lacteals)
• Collect and removes excess fluid and waste from interstitial space
• maintains blood pressure and volume and control build of fluid in the interstitial space
• aids the immune system in removing waste, dead cells, and pathogens through immune surveillance

Question 24

What is the interstitial space?

Answer 24

Area in CT and surrounding cells

Question 25

What is interstitial fluid?

Answer 25

excess ISF that is then returned to venous circulation via small lymphatic capillaries

Question 26

What is edema?

Answer 26

excess ISF in the interstitial compartment

Question 27

What is hydrostatic capillary pressure?

Answer 27

Pressure execrted by the volume of blood in the capillary

Question 28

How does an increase in pressure lead to an increase in lymph production?

Answer 28

An increase in hydrostatic pressure will stimulate filtration (out) at the arterial end which will then become lymph fluid.

Question 29

How does arteriole vasodilation or decreased venous return affect hydrostatic capillary pressure?

Answer 29

Arteriole vasodilation and decreased venous return would increase hydrostatic capillary pressure and could cause edema if too much fluid enters the interstitial space.

Question 30

What is osmotic (colloid) pressure?

Answer 30

pressure created on capillary by plasma proteins

Question 31

How does a decrease in albumin cause edema?

Answer 31

Albumin is responsible in maintaining osmotic pressure of the blood, so if there's a decrease, a lack of this pressure maintenance can cause an increase in hydrostatic pressure which will cause fluid to enter the interstitial space which then causes edema.

Question 32

What is the path of lymph flow from the interstitial CT space to where it joins the circulatory system?

Answer 32

Lymphatic capillary -> afferent lymphatic vessel -> local lymph nodes -> efferent lymphatic vessels -> lymphatic trunk -> two main collecting ducts (right lymphatic collecting duct or thoracic duct) -> venous angle (junction of internal jugular and subclavian v.)

Question 33

What is the physiological impact of obstruction to lymph flow and what might cause an obstruction?

Question 34

What is the path of lymph flow from the oral cavity?

Answer 34

site of infection -> primary lymph node (submandibular nodes drain oral cavity) -> collecting nodes -> jugular trunks -> collecting duct -> venous system

Question 35

What are the similarities and differences in histological features of lymph vessels to veins?

Answer 35

dilatd lumen, thin layer of smooth muscle in wall, valves prevent backflow and direct unidirectional flow. extremely thin walls compared to venule whose wall is thicker. Does not contain red blood cells in vessels.