Histo lymph

Question 1

List the functions of the lymphatic system

Answer 1

(a) to return fluid and plasma proteins to blood
(b) to return lymphocytes of the recirculating pool
(c) to add antibodies formed in lymph nodes

Question 2

Define lymph

Answer 2

• lymph is an ultrafiltrate of blood plasma

- formed by seepage of blood fluid across capillary walls

Question 3

Lymph Flow

Answer 3

lymph capillaries –> lymphatic vessels–> Lymph nodes Via Afferent vessels –> Thoracic duct or Subclavian via Efferent vessels

Question 4

Lymphedema

Answer 4

Swelling caused by damage or malformation of the lymphatic system

Question 5

Lymphatic Filariasis

Answer 5

infectious, caused by nematode worms

Ex: elephantiasis

Question 6

Lymph Capillaries

Answer 6

• endothelium very thin
• clefts between endothelial cells (No Valves, LEAKY)
• Discontinuous basal lamina
• Lack tight junctions
• No RBC in lumen
• incomplete basement membrane

Question 7

Do all capillaries not have valves?

Answer 7

No, larger capillaries, like the ones in the leg have valves to prevent back flow down.

Question 8

What prevents the lumen in capillaries from collapsing?

Answer 8

Anchoring Filaments.

They surround the connective endothelial tissue

Question 9

Lymphatic Vessels

Answer 9

• larger lumen than blood vessels
• thicker wall than lymph capillaries
• Have valves
• flow depends on pressure from neighbouring structures

Question 10

Lymphatic Ducts (trunks)

Answer 10

• right lymphatic and thoracic duct
• similar to veins - possess valves, more smooth muscle in media than veins
• empty into great veins at base of neck

Question 11

Lymph Tissue

Answer 11

consists of reticular tissue (reticular cells and fibers), free cells (chiefly lymphocytes)

• underlies the epithelial lining of the digestive and respiratory systems
• also in lymph nodes, spleen, tonsils

Question 12

Lymphoid nodules

Answer 12

-dense aggregations of lymphoid tissue
(COLLECTION OF LYMPHOCYTES)

• Found in the cortex of lymph nodes and in white pulp in the spleen
• found in tonsils, appendix, under epithelium of digestive and respiratory tracts

Question 13

Primary nodule

Answer 13

Tightly packed small lymphocytes

Question 14

Secondary nodule

Answer 14

Germinal center surrounded by cap of small lymphocytes

Question 15

Lymph Nodes Function

Answer 15

• Filter lymph
• Removed undesirable cells, invading microorganisms
• Lymphocyte production

Question 16

Lymph Node locations

Answer 16

In certain areas such as the mesentery, axilla, groin

Question 17

Do lymph nodes have capsules?

Answer 17

Yes; Connective tissue covering. Extends into node as trabeculae.

Question 18

What are spaces of lymph nodes filled with?

Answer 18

Lymphocytes, Macrophages, plasma cells

Question 19

How does filtrate enter the lymph node and how does it exit?

Answer 19

Enters via the afferent vessels over the surface, and exits via the efferent vessels through the hilus

Question 20

Types of Lymphatic sinuses

Answer 20

Subscapular sinus

Cortical sinus

Question 21

Subcapsular sinus

Answer 21

Enters corticol (peritrabecular sinus) which follow the trabeculae

-Filled with reticularcytes and macrophages

Question 22

Cortical sinus (peritrabeculae)

Answer 22

Enters the medullary sinus which are located between the medullary cords

Question 23

Where is the pericordical area and what is found there?

Answer 23

Between the Medulla and cortex T cells

Question 24

What is trabeculae made up of?

Answer 24

reticular cells and macrophages

Question 25

Where can I find B cells?

Answer 25

In the germinal centers of secondary nodules

Question 26

What is trabeculae?

Answer 26

Continuation of capsule

Question 27

What are reticular Cells

Answer 27

Reticular cells are fibroblasts that are specialized in the production of type III collagen

Question 28

Lymphatic Sinuses

Answer 28

lymph courses from the afferent lymphatic to subcapsular sinuses to cortical sinuses - reticular fibers but no basement membrane underlie the lining cells

Question 29

Cortex of nodule

Answer 29

the outer cortex contains primary and secondary nodules - the deep cortex consists of diffuse lymphoid tissue -the lymphocytes in this zone are chiefly T-lymphocytes seeded from the thymus

Question 30

Medulla

Answer 30

lymphoid tissue arranged in the form of irregular, anastomosing medullary cords

Question 31

medullary cords

Answer 31

aggregations of diffuse lymphoid tissue

Question 32

medullary sinuses

Answer 32

- large, tortuous, irregular channels that branch and anastomose - medullary sinuses are interposed between trabeculae and cords

Question 33

Blood Vessels

Answer 33

b.v.'s enter and leave at the hilus and run in the trabeculae

Question 34

postcapillary venules (high endothelial venules)

Answer 34

- Course radially in the deep cortex (Cuboidal cells) - they represent the portal of entry from blood into the lymphatic circulation - HEVs enable lymphocytes circulating in the blood to directly enter a lymph node (by crossing through the HEV) through aquaporins - located in perchordical region between cortex and medulla - where majority of lymphocytes leave vascular and gain access into lymph nodes

Question 35

Medullary Cords and what is found in them

Answer 35

extension of the cortex running into the medulla. B-lymphocytes, macrophages, dendritic and plasma cells

Question 36

What are sinuses lined by

Answer 36

stellate endothelial cells and macrophages

Question 37

What do HEV's contain?

Answer 37

Aquaporin channels on HEV columnar epithelium create solvent drag (pulls in lymph via afferent vessels)

Question 38

What do T Helper Cells induce?

Answer 38

immature B cells in the germinal center of the nodule to form larger lymphoblasts

Question 39

What do Lymphoblasts give rise to?

Answer 39

memory cells and then plasma cells, which secrete antibodies (IgG)

Question 40

Function of the spleen

Answer 40

- Blood filtration, destruction of old blood cells and platelets, hemoglobin degradation - Immune defense against blood-borne antigens, production of antibodies - contains large amounts of lymphoid tissue

Question 41

Hemopoiesis

Answer 41

production of lymphocytes

Question 42

Spleen Capsule

Answer 42

dense connective tissue, elastic fibres, smooth muscle - contraction changes volume - covered by mesothelium

Question 43

Splenic Pulp

Answer 43

reticular framework provides support - supports "pulp" - divided into white and red based on their colour in the fresh state:

Question 44

White pulp

Answer 44

lymphoid tissue: lymphocytes, plasma cells, macrophages in reticular c.t. - central arteries pass into the pulp from the trabeculae - Surrounded by red pulp Cylindrical mass of lymphocytes arranged around a central artery. Constitutes the periarterial lymphatic sheath (PALS).

Question 45

Red pulp

Answer 45

rich in blood - red pulp fills all the remaining space outside the white pulp and trabeculae vascular sinuses with branching cords of cells - the cords are called splenic cords or Billroth cords splenic sinuses surrounded by splenic cords

Question 46

Flow of blood through spleen

Answer 46

Artery enters spleen through hilus. Gives rise to trabecular artery that gives rise to central arteris. Each central artery leaves white pulp to enter in the red pulp.