Immune system (704-719)

Question 1

What are macrophages?;

Answer 1

Type of white blood cell of the innate immune system that engulf and digest pathogens by phagocytoses. Examples- monocytes, kupffer cells (liver), aveolar macrophage.

Question 2

What are giant cells?;

Answer 2

Giant cells are multi-nucleated cells, made by the fusion of multiple macrophages. Form as a result of frustrated phagocytosis (when a phagocyte fails to engult its target. Examples include- Langhans (Giant cell in TB), Touton (Giant cell in fat necrosis).

Question 3

What is a granuloma?;

Answer 3

Collection of macrophages that may form in chronic inflammation. May also have associatd lymphocytes or an area of central necrosis. The immune system is unable to eliminate the substance and, subsequently, attempts to ‘wall it off’ from the surrounding tissues. Some examples of diseases that feature granulomatous inflammation include tuberculosis, leprosy and Crohn’s disease.

Question 4

Define pus;

Answer 4

Thick yellowish or greenish opaque liquid produced in infected tissue, often consisting of dead neutrophils, bacteria and tissue debris and serum.

Question 5

What is an abscess?;

Answer 5

An enclosed collection of pus surrounded by granulotmous tissue.

Question 6

Define necrosis;

Answer 6

A form of cell injury which results in the premature death of cells in living tissue by autolysis.

Question 7

What are the types of necrosis and what are the salient features of each type?;

Answer 7

The type of tissue determines the necrosis pattern. 1. Coagulative necrosis- most common, ischemia occurs, Tissue firm and then becomes soft as it is digested by macrophages. 2. Colliquative necrosis- occurs in tissue with no supporting stroma e.g. CNS. 3. Caseous necrosis- eosinophillic tissue. Seen in TB. 4. Gangrene- nercrosis with putefaction (decay) of tissue - large ischemia. 5. Fibrinoid necrosis- seen in arterioles. Necrosis of smooth muscle wall. 6. Fat necrosis- direct trauma to adipocytes. Lipids incide local inflammatory reaction.

Question 8

Define apoptosis and state some instances of apoptosis;

Answer 8

Cell programmed cells. Phogocytosis doesn’t occur, instead the cell degenerates into apoptotic bodies. Examples- separation of digits in hand & fet as fetus & mentrasal cycle,

Question 9

What is amyloidosis?;

Answer 9

Rare disease that occurs when a protein called amyloid builds up in tissues and organs. (Diagnosis - red congo stain gives bifringent apple green colour)

Question 10

What are the types of amyloidosis and where are they commonly found?;

Answer 10

AL (primary) amyoidosis- immunoglobin light chain proteins, wide range of symptoms affecting most organs. AA (secondary) amyloidosis- caused by chronic infection or inflammatory disease.

Question 11

Name the lymphoid cells;

Answer 11

B cells (adaptive and humoral immunity)- when activated matures into plasma cells which secrete antibodies and memory B cells. T cells (adaptive and cell-mediated immunity)- cytotoxic T cells can directly attack infected cells, helper T cell activate B cells and form memory T cells which respond to re-infection. Nautural killer cells- non specific immunity against forgein proteins.

Question 12

Describe the histology of lymph node; https://step1.medbullets.com/immunology/105045/secondary-lymphoid-tissue

Answer 12

Encapsulated, bean shaped structures. Capsule of connective tissue. Outer Cortex (B cell layer) which contains follicles of B cells, each with a germinal center where B cells diffeentiate into plasma cells. Inner cortex ( T cell layer) consists of T cells. Medulla (innermost layer) contains blood vessels and medullary cords (transport)

Question 13

What lymphoid cells are produced by the different parts of the lymph node?;

Answer 13

Outer cortex - B cells. Inner cortex (paracortex) - T cells

Question 14

What are the compomnents of the lymphatic system?; https://teachmeanatomy.info/the-basics/ultrastructure/lymphatic-system/

Answer 14

Lymph vessels, lymph nodes and lymph organs. Forms vital part of body’s immune defence - if lymph node or organs detects presence of a pathogen they can mount an immune response.

Question 15

What are primary and secondary lymphoid organs?;

Answer 15

Primary organs- spleen (remove old RBC and role in immune response for encapsulated bacteria), thymus (development and maturation of T lymphocyte cells), red bone marrow (matures immature lymhocytes [same as thymus]. Secondary organs- tonsils (Walyders ring), appendix, walls of gastrointestinal treact

Question 16

Desccribe the circulation of lymph; https://teachmeanatomy.info/the-basics/ultrastructure/lymphatic-system/

Answer 16

Lymph channels (drain through several lymph nodes) -> lympahtic trunks -> right thoracic duct (drains right upper quadrant of body) or thoracic duct (rest of body [Both lower quadrants via cisternia chyli and left upper quadrant] -> both drain into subclavian veins at same point internal jugular vein does.