Histology of the lymphatic system

Question 1

What are the primary lymphatic components?

Answer 1

Bone marrow
Thymus

Question 2

What is the function of primary lymphatic components?

Answer 2

Produce and mature immune cells that spread into the secondary immune components

Question 3

What is the function of secondary lymphatic components?

Answer 3

Filter body fluids to recognise antigens.
Respond by activation of cells that produce antibodies or use other methods to tackle the immune response, where immune cells do their actual job.
Area where naive lymphocytes transition to activated lymphocytes.

Question 4

What is the Function of the thymus in the immune response?

Answer 4

Mature t-lymphocytes needed for cell mediated immunity.

Question 5

What is the function of the bone marrow in the immune response?

Answer 5

Matures b-lymphocytes needed for humoural immunity.
And produces other types of white blood cells.

Question 6

What are the secondary components of the lymphatic system?

Answer 6

MALT
Tonsils
Lymph nodes
Spleen

Question 7

What is the function of MALT?

Answer 7

Lymphoid tissue found in the lamina propia of the mucosal layer in organs that open to the external environment such as GI, respiratory, urinary and reproductive system.
Filter fluid percolating through the lamin propia, with the potential to recognise antigens and trigger an immune response.

Question 8

What is the function of tonsils in the immune system?

Answer 8

Are part of the MALT system, the palatine, pharyngeal and lingual tonsils form a ring of lymphatic tissue called Waldeyer’s ring around the entrance to the oral and nasal cavity.
Filter for antigens, may trigger an immune response.

Question 9

What is the function of lymph nodes in the lymphatic system?

Answer 9

Fluid samples by MALTS or excess drained from interstitial fluid is drained here, filter lymph, contain t-lymphocytes to respond to any antigens.

Question 10

What is the function of the spleen in the immune system?

Answer 10

Filters blood for antigens.

Question 11

What is the hierarchy of lymph structures?

Answer 11

Lymphatic capillaries
Lymphatic vessels
Lymph nodes
Lymph trunks
Lymphatic ducts.

Question 12

What area of the heart does the lymphatic system drain into?

Answer 12

The right atrium

Question 13

What is the function of the lymphatic system?

Answer 13

Lymphatic vessels trasnport excess fluid away from the interstitial spaces and return it to the bloodstream
Lacteals located in the small intestine abosrbe digested fats, and add them to venous circulation
Help defend the body against disease causing agents.

Question 14

What are some features of the lymphatic capillaries?

Answer 14

Highly permeable
Epithelial lining made of single endothelial cells
Has anchoring filaments

Question 15

What is the function of anchoring filaments in the lymphatic capillaries?

Answer 15

Helps prevent odema.
When the ECF pressure is very high anchoring filaments help pull apart the endothelial cells of the lymphatic capillaries, this widens the capillaries so more fluid can drain in and become lymph.

Question 16

What causes lymph to be transported through lymphatic vessels?

Answer 16

1. Contraction of skeletal muscles and bludging of nearby arteries
2. Contraction on tunica media
3. normal movement of limbs and trunk

Question 17

What stimulates natural killer cells?

Answer 17

Interferons

Question 18

What type of cells can a t-cell differentiate into?

Answer 18

Memory cells
T helper cells
Cytotoxic cells

Question 19

What is the function of the cortex in the lymph node?

Answer 19

B cell activation and clonal expansion to produce large numbers of activated B lymphocytes, contains germinal centres within lymphatic follicles.

Question 20

What is the function of the paracortex in the lymph node?

Answer 20

T cell activation and clonal expansion.
T cells differentiate

Question 21

What is the function of the medulla in the lymph node?

Answer 21

Mature b lymphcoytes produced in the cortex germinal centre migrate through the paracortex, here plasma cells mature and start secreting antibodies.

Question 22

What is the function of high endothelial venules in the lymph node?

Answer 22

A portion of vein with a simple cuboidal epithelial lining, allows transport of lymphocytes through the endothelium of the vein into and out of the lymph node.

Question 23

What is diapedesis?

Answer 23

The passage of white blood cells through the capillary walls, typically accompanied by inflammation.

Question 24

What is the function of the hilum in the lymph node?

Answer 24

Where the efferent vessels leaves
Where vasculature passes in and out of the lymph node.

Question 25

What is the capsule of a lymph node?

Answer 25

The outer coat of connective tissue, folds into the cortex as trabecula separating the cortex into segments.

Question 26

How can you differentiate beween the medulla and the cortex on an histological image?

Answer 26

The cotex is towards the outside of the lymph node. Cortex contains a higher number of lymphocytes and has germinal centres, so stains a darker purple as more basophilic.

Question 27

What is the function of the subcapsular sinus in the lymph node? What does it look like on a histological image?

Answer 27

Located between the capusle and the cortex. Recieves lymph, allows lymph to diffuse across into the cortex. Like a thin white bind with some pink patches running around the inside of the capsule.

Question 28

Describe the basic structure and location of the thymus.

Answer 28

Located inferior to the neck In the superior thorax Posterior to the sternum Sits ontop of the pericardium Consits of two lobes (left and right) each with multiple lobules.

Question 29

What is the function of the thymus? How does its histology suit this function?

Answer 29

Site for the maturation of T-cells Contains type six epithelial reticular cells called ERCVI These cells ensure that self recognising t-cells do not survive. T-cells come into contacts with the ERCVI as they migrate from the thymus cortex to the medulla, these epithelial cells contains most self antigens.

Question 30

What is the function of the blood thymus barrier?

Answer 30

Seperates the immature lymphocytes in the thymus from mature lymphocytes circulating in the blood. Also prevents any self antigens in the blood from entering the thymus and reacting with the self lymphocytes that have not yet been killed causing an autoimmune response.

Question 31

What is the blood thymus barrier made of?

Answer 31

1)capillary endothelium and its basal lamina layer, 2)perivascular connective tissue occupied by macrophages 3)Type 1 epithelial reticular cells and their basal lamina

Question 32

What is Digeorge syndrome Catch22?

Answer 32

Congenital failure of the thymus to develop, patients die at an early age from infection as T-lymphcoytes do not develop Congential heart disease Abnormal face Thymic aplasia or hypoplasia Cleft palate Microdeletion of chromosome 22.

Question 33

Describe the location of the spleen.

Answer 33

Left upper quadrant Inferior to the diaphragm In the area of rib IX to rib X Posterior to the stomach.

Question 34

What are splenic sinuses and splenic cords?

Answer 34

Splenic cords are areas of fibrils and connective tissue that contain a large number of macrophages and monocytes Splenic sinuses are areas between the connective tissue, fill with blood so have a large number of erythorcytes.

Question 35

What is the proportion of red pulp to white pulp in the spleen?

Answer 35

Red pulp = 80% white pulp = 20%

Question 36

What is the main difference between the lymph nodes and the spleen in their immune function?

Answer 36

Spleen receives antigens from blood Lymph nodes receive antigens from lymph.

Question 37

What are penicillar arteries?

Answer 37

Small arteries of the spleen. Open directly into splenic cords, to exposure blood to macrophages before it enters the sinuses.

Question 38

How can the red and the white pulp of the spleen be distinguished on a histological image?

Answer 38

White pulp stains a darker purple as it contains a higher concentration of basophilic lymphocytes The red pulp is a lighter dense pink/purple.

Question 39

Describe the structure of splenic follicles/nodules?

Answer 39

Contains a central arteriole and associated PALS, this is pushed to the side into the marginal zone. The germinal centre is eosinophilic and contains mature b cells. Then is the mantle zone containing highly dense b cells and macrophages, waiting to be activated. Then is the marginal zone consisting of less dense b lymphocytes and macrophages.

Question 40

Describe the histological structure of the tonsils?

Answer 40

Startified squamous epithelium folded into crypts (white spaces) Lymphatic follicles beneath the epithelium (line line pattern - compared to the circular ring in lymph nodes)

Question 41

What histological layer are the tonsils found in?

Answer 41

The lamina propia.

Question 42

What is diffuse lymphoid tissue?

Answer 42

The only type of lymphoid tissue not surrounded by a capsule.