Lecture 6 1/25/24

Question 1

What are the functions of the lymphatic system?

Answer 1

-transport materials via lymphatic vessels
-filtration of lymph and blood
-production of defense cells
-production of immunoglobulins

Question 2

What is the role of primary lymphoid organs?

Answer 2

produce and train lymphocytes

Question 3

What is the role of secondary lymphoid organs?

Answer 3

surveillance of incoming antigens

Question 4

What are the different structural classifications of lymphoid organs?

Answer 4

-diffuse unencapsulated
-dense unencapsulated
-dense encapsulated

Question 5

What are the characteristics of diffuse unencapsulated lymphoid organs?

Answer 5

-loose collections of leukocytes
-individual cells not forming an aggregate or mass
-found GI, urinary, and respiratory tracts

Question 6

What are the characteristics of dense unencapsulated lymphoid organs?

Answer 6

-sub-epithelial aggregates of leukocytes
-found in GI and respiratory tracts
-tonsils, MALT, GALT, BALT
-cells form aggregate/mass-like structure

Question 7

How do different species vary in terms of tonsillar crypts?

Answer 7

-present in horses, swine, sheep, and goats
-absent in carnivores
-variable in ruminants

Question 8

What are the characteristics of dense encapsulated lymphoid organs?

Answer 8

-typical lymphoid organs
-thymus and bursa for primary organs
-lymph nodes, spleen, hemal nodes, and hemolymph nodes for secondary organs

Question 9

What are follicles?

Answer 9

spherical accumulations of lymphocytes

Question 10

How do primary and secondary follicles relate?

Answer 10

secondary follicle = primary follicle + antigenic stimulation

Question 11

What are the functions of lymph nodes?

Answer 11

-filter particulate matter and microbes
-surveillance of incoming antigens
-activation of B cells

Question 12

What structures are present within the lymph node?

Answer 12

-capsule
-sub-capsular sinus
-trabeculae
-cortex
-paracortex
-medulla/medullary cords
-medullary sinuses

Question 13

What composes the outer cortex of the lymph node?

Answer 13

lymphoid follicles

Question 14

Where are lymphocytes found within the lymph node?

Answer 14

-B cells: cortex
-T cells: paracortex

Question 15

What are the characteristics of blood flow through the lymph nodes?

Answer 15

-arteries enter at hilus
-flow follows trabeculae
-capillaries are in paracortex
-veins exit at hilus

Question 16

What is the function of high endothelial venules?

Answer 16

recruit lymphocytes in order to monitor lymph

Question 17

What are the characteristics of lymph flow through the lymph nodes?

Answer 17

-moves from capsule to hilus
-flow from afferent vessels to sub-capsular sinues, cortical sinuses, medullary sinuses, and efferent lymphatic vessels

Question 18

Why is it important that sinuses are highly fenestrated?

Answer 18

allows for “bad stuff” to mix with immune cells

Question 19

What does the fenestration of sinuses facilitate?

Answer 19

-development of an immune response
-spread of infection
-dissemination of cancer

Question 20

What is unique about pig lymph nodes?

Answer 20

they are inside out, with the cortex central and the medulla peripheral

Question 21

What are the functions of the spleen?

Answer 21

-blood filtration
-immune response
-blood storage
-blood cell formation and production

Question 22

What structures are part of the spleen capsule?

Answer 22

-trabeculae
-smooth muscle
-elastic fibers

Question 23

What are the characteristics of spleen white pulp?

Answer 23

-contains periarteriolar lymphoid sheaths (T cells surrounding arterioles)
-contains the T and B lymphocytes

Question 24

What are the characteristics of spleen red pulp?

Answer 24

-blood filled sinuses lined by phagocytic cells
-phagocytic cells remove debris, abnormal cells, and “spent” erythrocytes

Question 25

What happens to hemoglobin in “spent” erythrocytes?

Answer 25

it becomes hemosiderin in macrophages, causing the cells to have a golden brown coloration

Question 26

What are the characteristics of blood flow through the spleen?

Answer 26

-arteries enter at hilus
-divide into trabecular arteries
-capillaries empty into red pulp sinuses
-veins exit at hilus

Question 27

What are the characteristics of lymph flow through the spleen?

Answer 27

-no afferent lymphatics
-efferents arise in the white pulp
-exit out of the hilus

Question 28

What are the characteristics of defensive spleens?

Answer 28

-primarily lymphoid tissue
-few trabeculae and smooth muscle
-seen in rabbits and humans

Question 29

What are the characteristics of storage spleens?

Answer 29

-less lymphoid tissue
-prominent trabeculae and smooth muscle
-seen in horses

Question 30

In which animals are hemal nodes seen?

Answer 30

young ruminants

Question 31

What is unique about hemal nodes?

Answer 31

they do not have lymphatics, only blood-filled sinuses

Question 32

What are the characteristics of the thymus?

Answer 32

-starts out as epithelial tissue
-lymphocytes migrate to thymus to become educated
-becomes lymphoepithelial organ
-atrophies with age
-no afferent lymphatics

Question 33

What is the role of the thymus capsule?

Answer 33

extends septa into the parenchyma to divide it into lobules

Question 34

What does each lobule of the thymus contain?

Answer 34

-cortex
-medulla
–thymic interdigitating cells
–Hassall’s corpuscles

Question 35

What are Hassall’s corpuscles?

Answer 35

concentric whorls of epithelial cells within the thymus medulla

Question 36

What is the bursa of fabricius?

Answer 36

blind sac from the dorsal wall of proctodeum found in birds

Question 37

What is the function of the bursa of fabricius?

Answer 37

development of B cells in birds

Question 38

What are the characteristics of bursa of fabricius structure?

Answer 38

-lined by simple columnar epithelium
-tightly packed, polyhedral lymphoid follicles
-follicles have a cortex and medulla