Lymph System Histo

Question 1

fnctns of lymphatic system

Answer 1

1. drain excess interstitial fluid
2. provide alt transport routes for hormones, nutrients, and waste
3. immune respone

Question 2

components of lymphatic system

Answer 2

1. lymphatic vessels
2. lymphocytes and variety of supporting cells
3. diffuse lymphatic tissue
4. lymphatic nodules
5. lymph nodes
6. spleen
7. bone marrow
8. thymus

Question 3

lymphatic vessels

Answer 3

• begin as networks of blind ended capillaries in microcap beds
• lymphatic caps form network with loose CT

Question 4

lymphatic capillaries

Answer 4

• endothelial tubes lack continuous basal lamina, is highly permeable
• collect excess protein rich ECF from EC spaces->lymph once it enters lymphatic vessels

Question 5

do lymphatic vessels have valves?

Answer 5

yes

Question 6

lymphatic vessels un

ite to form two main channels

Answer 6

1. thoracic duct: largest lymph vessel, drains majority of body
2. R lymphatic duct: drains UR limb, R thorax, R neck, R head

*both drain to venous angle

Question 7

cells of the lymphatic system

Answer 7

lymphocytes

-effector cells, 3 types

Question 8

3 types of lymphocytes

Answer 8

1. B lymphocytes
2. T lymphocytes
3. NK cells

Question 9

B lymphocytes

Answer 9

• 20-30% of circulating lymphocytes
• membrane bound B cell receptor: immunoglobulin
• activated B cells (plasma cells) secrete non membrane bound form of Ig= antibodies
• involved in humoral immunity

Question 10

T lymphocytes

Answer 10

• mature in thymus
• 60-80% of circulating lymphocytes
• cell mediated immunity: release cytokines against intracellular pathogens

Question 11

NK cells

Answer 11

• 5-10% of circulating lymphocytes
• potent killers of certain types of cells: virally infected and malignant cells
• innate immunity

Question 12

supporting cells

Answer 12

• interact with lymphocytes, antigen presentation and regulation of immune responses
• monocytes, neutrophils, basophils, eosinophils, dendritic cells, follicular dendritic cells, langerhans cells, reticular cells, epithelioreticular cells

Question 13

where is diffuse lymphatic tissue found

Answer 13

1. alimentary canal
2. respiratory assages
3. genitourinary tract

Question 14

diffuse lymphatic tissue

Answer 14

• not surrounded by a CT capsule
• lymphocytes, plasma cells,fibroblasts, and eosinophils found in lamina propria at these sites
• lymphocytes most abundant

Question 15

lymphatic nodules/follicules

Answer 15

• discrete concentrations of lymphocytes contained in meshwork of reticular cells
• sharply defined but not surrounded by CT capsule
• primary and secondary nodules

Question 16

primary vs secondary nodules

Answer 16

• primary: resting lymphocytes, small
• secondary: 1. germinal center: response to antigen, develops when lymphocyte binds to antigen, returns to primary nodule and proliferates, light staining bc euchromatin, contain follicular dendritic cells
  2. mantle zone: encircle germinal center

Question 17

where are aggregations of lymphatic nodules specifically found

Answer 17

1. tonsils: form ring of lymph tissue at entrance of oropharynx and nasopharynx -> waldeyers ring
2. peyers aptches: in ileum of SI, numerous aggregations of lymphatic nodules and T and B lymphocytes
3. veriform appendix: from cecum of LI

Question 18

lymph nodes

Answer 18

• small, bean shaped encapsulated lymphatic organs
• along pathway of lymphatic vessels
• filter lymph priot to its return to blood circ

Question 19

afferent lymphatic vessels

Answer 19

convey lymph toward the node, enter at the convex surface

Question 20

efferent lymphatic vessels

Answer 20

convey lymph away from node, leave at hilum

Question 21

lymph node stroma

Answer 21

• capsule: DCT
• trabeculae: DCT extending from capsule
• reticular tissue: reticular cells and fibers form fine supporting network

Question 22

cells of reticular meshwork

Answer 22

1. reticular cells: synth and secrete reticular fibers and ground substance (supporting role and produce substances that attract T and B cells and dendritic cells
2. dendritic cells: bone marrow derived APCs (presentantigen to T cells)
3. macrophages: act as phagocytes and APCs
4. FDCs: thin. hairlike branching of cytoplasmic processes

Question 23

parenchyma of lymph node is divided into

Answer 23

1. cortex: outer portion, (superficial cortex: outer part, just deep to capsule, contains germ centrs, deep cortex: btwn sup and medulla, contains majority of T cells in lymph nodes
2. medulla: medulla cords (contain B cells, macros, dendritic cells, plasma cells) separated by medullary sinuses (conerge near hilum and drain into efferent lymph vessels

Question 24

lymph node filtration

Answer 24

occurs through interconnected channels

1. subcapsular (cortical) sinus
2. trabecular sinuses
3. medullary sinuses
   * high endothelial vessels (lymphocytes civered in blood enter node via HVE in deep cortex

Question 25

flow from blood thru node

Answer 25

HVE-deep cortex-superficial cortex-medulla-eff lymph vess

Question 26

flow from lymph thru node

Answer 26

aff lymph vess-subcapsular sinus-trabecular sinuses-medullary sinus-eff lymph vess

Question 27

thymus

Answer 27

• in sup mediastinum, ant to heart

- at puberty: T cell differentiation and proliferation reduced, organ mainly replaced with adipose tissue

Question 28

structure of thymus

Answer 28

1. capsule: thin CT
2. trabeculae: extends from cap into parenchyma, forms thymic lobules
3. thymid lobules: 1. cortex: basophilic, contain thymocytes and macrophages, 2. medulla: inner portion, lighter staining, type VI epithelioreticular cells (form hassals corpuscles

Question 29

thymic hassalls cells

Answer 29

have keratohyalin granules so eosinophilic, center is fully keratinized cells

Question 30

spleen

Answer 30

• largest lymphatic organ
• rich blood supply-filters blood (lymphnode for blood)
• enclosed in DCT capsule which trabeculae extend from into parnchyma
• contains 1. red pulp (blood filtration and splenic sinuses separated by splenic cords) 2. white pulp (lymphatic tissue, mostly lymphocytes, basophilic w/ H&E, central a (br of splenic a) surrounded by PALS