The Lymphatic System

Question 1

What is the function of the lymphatic system

Answer 1

Carries excess ecf back to venous system
Fluid is a result of filtration from capillaries and include large particles such as pathogens, cells of lymphatic system, cell products and cell debris

Question 2

Color of lymph

Answer 2

Colorless

Opaque and milky in intestine due to presence of chylomicrons (called chyle)

Question 3

Places where lymphatic vessels dont exist

Answer 3

Brain
Bone marrow
Avascular tissues such as (epithelia and cartilage)

Question 4

What does the lymphatic system consist of

Answer 4

Lymph nodes
Lymphatic vessels
Lymphatic ducts
Spleen

Question 5

What are the lymphatic vessels

Answer 5

Form extensive and complex interconnected network of channels which begin as porous blind ended lymphatic capillaries

Question 6

What are the 2 lymphatic ducts

Answer 6

Thoracic and right lymphatic duct

Question 7

Where does the thoracic duct begin and end

What does it drain

Answer 7

Begins: in cisterna chili in abdomen
Ascends through posterior abdominal and thoracic walls deviating to the left
Terminates: at junction of left subclavian vein and left internal jugular vein

Drains lymph from all body except upper right quadrant

Question 8

Where does the right lymphatic duct end and what does it drain

Answer 8

Upper right quadrant

Terminates at the junction of right subclavian and right internal jugular vein

Question 9

What are the 2 parts forming the lymphoid organs

Answer 9

Stroma: CT supportive framework of organ
2 parts: covering dense CT capsule and CT trabeculae that extend from capsule for structural organization of organ
Fine stroma: fine reticular fibers forming a supportive network for the cells of the organ

Parenchyma: functional cellular part
Divided in to outer cortex and inner medulla

Question 10

Describe the thymus

Answer 10

Primary lymphoid organ
Site of maturation of t lymphocytes
Originates early in embryo and continues to grow until puberty
35-40g
Involute and turns to adipose cells in old age

Question 11

Describe the histological structure of the thymus

Answer 11

Capsule of thymus is composed of dense irregular collagenous CT
Sends septa in to the lobes subdividing them in to lobules
Lobule is composed of a cortex and medulla

Question 12

What is the function of the thymus

Answer 12

Immunological competency of t cells
Elimination of self intolerant t cells
MHC recognition occur in the thymic cortex

Question 13

What are the cells in the cortex on thymus

Answer 13

T lymphocytes
Macrophages
Epithelial reticular cells

Question 14

Function of epithelial reticular cells

Answer 14

Interconnected branches forming a cellular network that supports developing t cells
Type1 shares in formation of blood thymic barrier

Question 15

What is the function of the blood thymic barrier and what are its components

Answer 15

Components:
▪️Cont endothelium of blood cap and their basal lamina
▪️Epithelial reticular fibers that are attached to each other by tight junctions and their basal lamina

Prevents developing t cells from having contact with any foreign ag in blood
Cells attached by tight junctions and allows only contact of t cells with self ag to educate t cells to tolerate self ag
If not they will undergo apoptosis

Question 16

What happens to the educated t cells

Answer 16

Enter the medulla of the thymus as naïve t lymphocytes and then distributed to secondary lymphoid organs via the vascular system

Question 17

Describe the medulla

Answer 17

Characterized by hasall’s corpuscles

All t cells in medulla are immunocompetent

Question 18

How are hasall’s corpuscle’s formed

Answer 18

Epithelial reticular cells:
Whorl shaped thymic corpuscles whose numbers inc with a person’s age
Type 4 cells mat become highly cornfield and even calcified

Question 19

What are the lymph nodes

Answer 19

▪️Small oval encapsulated structures along the course of the lymphatic vessels
▪️Convex outer surface and concave one which contain hilum
▪️divided in to outer and inner cortex

Question 20

Describe the stroma of the lymph nodes

Answer 20

▪️Dense CT capsule that is thickened at the hilum(portal of exit or entry of blood vessels)
▪️incomplete trabeculae arise from the capsule of the cortex and medulla subdividing them in to small compartments

Question 21

Describe the cortex of the lymph node

Answer 21

Subdivided in to compartments that house b cell rich primary and secondary lymphoid
2 types: primary and secondary
Secondary have germinal centers

Question 22

Describe whats in the primary and secondary lymphoid nodes

Answer 22

Primary: small b cells
Secondary: small germinal center formed of large lymphocytes that represent proliferating b cells in response to exposure of ag
Lymphoblasts differentiate in to plasma cells and memory b cells

Question 23

Describe the paracortex

Answer 23

▪️Houses mostly t cells(thymus dependent zone of lymph node)

▪️High endothelial venules

Question 24

Describe the medulla

Answer 24

▪️Composed of large tortuous lymph sinuses surrounded by lymphoid cells that are organized in clusters known as medullary cords
▪️cells: lymphocytes plasma cells and macrophages (emeshed in network of reticular fibers and reticular cells)

Question 25

What are the functions of the lymph node

Answer 25

▪️act as sites for ag recognition
▪️flow rate is reduced as lymph enters lymph node which gives macrophages time to phagocytose matter
▪️b memory and plasma cells leave cortex and form medullary cords

Question 26

Where do remaining of plasma cells go

Answer 26

Sinuses and go to bone marrow where they continue to manufacture ab until they die

Question 27

Describe lymphangitis and lymphadenitis

Answer 27

Secondary inflammations of lymphatic vessels and lymph nodes
May occur when lymphatic system is involved in chemical or bacterial transport after severe injury or infection

May become apparent as red streaks in skin and nodes become enlarged
May lead to septicemia

Question 28

Describe lymphedema

Answer 28

Localized edema

Occurs when lymph doesn’t drain from an area in body

Question 29

How does lymphogenous spread occur

Answer 29

Solid cell growths may permeate lymphatic vessels and form minute cellular emboli which may break free and pass to regional lymph nodes

Question 30

How do lymphocytes leave the vascular supply

Answer 30

Lymphocytes leave the vascular supply by migrating between cuboidal cells of unusual epithelium and enter substance of lymph node
B cells migrate to outer cortex while t cells remain in paracortex