Lymphatic System

Question 1

What are the functions of the Lymphatic System?

Answer 1

• to protect the body against pathogenic organisms and their products
• to help in the removal and disposal of cells undergoing natural or induced degenerations

Question 2

What is the function of the primary lymphatic organs?

List the organs

Answer 2

generate lymphocytes from progenitor cells

• bone marrow
• cloacal bursa/bursa of fabricius
• thymus

Question 3

What is the function of the secondary lymphatic organs?

List the organs

Answer 3

sites of lymphocyte activation/differentiation in context of immune response

• lymph nodes
• spleen
• mucosal associated lymphoid tissue

Question 4

Describe the Bone Marrow

Answer 4

• source of pluripotent cells
• B cells mature
• contains a background of stromal cells that release factors aiding cell differentiation, and macrophages

Question 5

What is the Cloacal Bursa?

Answer 5

• Bursa of Fabricius
• bird equivalent of bone marrow
• contain nodules full of lymphoid cells with B cell rich cortex
• background of stromal cells and macrophages

Question 6

Describe the Thymic Cortex

Answer 6

• stains darker due to increased number of lymphocytes

- area of positive selection

Question 7

What are the functions of the stromal cells?

Answer 7

• clear up debris

- release factors that help environment for differentiation

Question 8

Describe the Thymic Medulla

Answer 8

• contains more prominent reticular cells
• area of negative selection
• tingible body macrophages eliminate dead T cells
• presence of Hassall’s corpuscles

Question 9

What are Hassall’s Corpuscles?

Answer 9

large central calcified or degenerated cells surrounded by concentric circles of keratinized cells

Question 10

What is the function of lymph nodes?

Answer 10

• to filter antigens from lymph before returning it to bloodstream

Question 11

What is the Hilus?

Answer 11

a slight indentation in the lymph node where arteries enter, and veins and efferent vessels leave

Question 12

What is the pathway of the lymph through the lymph node?

Answer 12

afferent vessel
subcapsular sinus
cortical sinus
medullary sinus
efferent vessel

Question 13

What is the function of the spleen?

Answer 13

• filters blood
• removes antigens from blood
• mounts immune response
• stores RBCs and platelets (not cats)
• iron recycling

Question 14

What does the red pulp in the spleen contain?

Answer 14

• sinusoids

- macrophages and blood cells

Question 15

What does the white pulp in the spleen contain?

Answer 15

• B cells in follicles
• T cells around central arterioles
• periarteriolar lymphoid sheaths

Question 16

Explain the blood flow through the spleen

Answer 16

central artery > branches to penicillary arteries > end in sheathed capillaries > parenchymal space > sinuses > splenic vein > hepatic portal vein

Question 17

List the Mucosal Associated Lymphoid Tissues

Answer 17

• gut-associated lymphoid tissue (GALT)
• bronchial-associated lymphoid tissue (BALT)
• tonsil
• ocular
• urogenital
• mammary

Question 18

Describe Peyer’s Patches

Answer 18

• aggregation of lymphatic nodules in submucosa of small intestine
• B cells migrate here, some level of maturation
• may involute with age
• have lacteals or lymphatic vessels

Question 19

What is the function of Peyer’s Patches?

Answer 19

to take nutrients in the form of chylomicrons to various parts of the body

Question 20

What are lacteals?

Answer 20

blind-ended lymphatic capillaries within intestinal villi of the chyle to lymphatic vessels

Question 21

What are M cells and what is their function?

Answer 21

• specialized epithelial cells that sit above Peyer’s patches
• pinocytose GI contents and secrete contents on lymphocytes and macrophages of the patches

Question 22

What are some features of the tonsils?

Answer 22

• no afferent lymphatic vessels

- presence of crypts