Anatomy of the immune system

Question 1

Primary lymphoid tissues

Answer 1

Bone marrow and thymus

Question 2

Bone marrow

Answer 2

Found on the inside of long bones

Shaft of long bone has 3 layers - periosteum compact bone and then the inner medullary cavity lined by endosteum and containing bone marrow

Where all immune cells originate

Most of these cells including B lymphocytes develop here

Question 3

Thymus

Answer 3

Organ with 2 lobes located behind the sternum (within mediastinum)

• Gland where lymphocytes develop into T-Cells

Outer area called the CORTEX — where T cells proliferate and start to develop into specialised cells

Inner area called MEDULLA — where the mature T cells are found before they enter the blood, and it also contains the waste products of defective T cells

Question 4

Lymphatic system

Answer 4

Network of lymphatic vessels similar to BVs

No pump (like in heart)

Circulation relies on muscles surrounding the vessels to pump (contains valves to direct the flow of lymph)

Eventually drains into circulation via the:
1=== Thoracic duct
2=== Right lymphatic duct

Question 5

Thoracic duct

Answer 5

Entering between left subclavian and internal jugular veins

Larger of the two ducts

Question 6

Right lymphatic duct

Answer 6

Entering at right subclavian or internal jugular veins

Drains: RIGHT upper thorax, upper limb head and neck

Question 7

Lymph

Answer 7

Fluid in the lymphatic system

Interstitial fluid that have drained from the interstitial space

High concentration of lymphocytes and dendritic cells

Low protein content

No red blood cells or other leukocytes

Question 8

Lymph nodes

Answer 8

Afferent - drains to lymph nodes
Efferent - drains away from lymph nodes

Role == Hold lots of cells of the immune system, particularly lymphocytes (act as filters for pathogens and abnormal cells)

Have 3 areas:
— CORTEX –> contains B cells and follicles

— PARACORTEX –> contains T cells and dendritic cells

— MEDULLA –> contains plasma cells, T and B cells and macrophages

— HILUM –> leading to the efferent vessel and where the blood vessels enter

Question 9

Follicles

Answer 9

Are areas where groups of B cells clump together and wait to be activated

• –Primary follicles contain unstimulated B cells and do not have germinal centres
• –Secondary follicles have germinal centres (that stain a lighter colour) and contain activated B cells that are generating plasma cells and memory B cells

Question 10

Spleen is an organ made up of:

Answer 10

1. Red pulp - where old RBCs are removed

2. White pulp - contains the immune system

Question 11

Spleen red pulp:

Answer 11

Red pulp is where old red blood cells are removed (filter through a web of reticular fibres that destroy old RBCs but young ones can squeeze through without getting destroyed).

Question 12

Spleen White pulp

Answer 12

Immune cells wrap themselves around the arterioles in the spleen forming the white pulp

Immediately around the arteriole is the ‘PALS’ === contains T cells and dendritic cells

The MARGINAL ZONE surrounds the PALS
—- Contains B cells and macrophages

At intervals along the arteriole there are follicles:

• Primary follicles contain unstimulated B cells
• Germinal centres are areas within the primary follicles where B cells have been stimulated and are differentiating into plasma cells and secreting antiboies

Question 13

Mucosa associated lymphoid tissue

Answer 13

This is lymphoid tissue associated with mucosa of the GI, Resp and Urinary tracts

It contains primary follicles and germinal centres similar to the spleen and lymph nodes

Much of it is unstructured and appears randomly along the tract

Examples of structured MALT tissues are:

• Tonsils
• Adenoids
• Appendix
• Peyer’s patches ( in the ileum of the small intestine)

Question 14

EXAMPLES of structured MALT Tissues

Answer 14

• Tonsils
• Adenoids
• Appendix
• Peyer’s patches ( in the ileum of the small intestine)