Week 1: Immune and Haematological Tissues

Question 1

Where is the site of hematopoiesis before and after birth?

Answer 1

Yolk Sac from 4 week of development
liver until shortly before birth
spleen until cartilaginous bones vascularised

bone marrow in adult

Question 2

What are primary lymphoid tissues?

Answer 2

Primary lymphoid tissues are the sites where lymphocytes differentiate to express antigen receptors
Thymus (T lymphocytes)
Bone Marrow (B lymphocytes)

Question 3

What are 2 common features of lymphoid tissues?

Answer 3

They have capsules (made out of collage and other extracellular matrix proteins) and compartmentalization(important for effect immune function).

Question 4

What are the 2 main compartments in the thymus?

Answer 4

Cortex and Medulla

Question 5

What are secondary lymphoid tissue?

Answer 5

Specialised sites for turning on the acquired immune response
- Lymph nodes
- Spleen
- Mucosal Associated Lymphoid Tissue (MALT)
Gut-associated lymphoid tissue (GALT)
Nasal associated lymphoid tissue (NALT)
etc

Question 6

What is the lymphatic system?

Answer 6

A drainage system involved in fluid balance, returning to the blood

• excess interstitial fluid (approx. 3 litres/24h)
• plasma proteins

Question 7

What are lymph capillaries?

Answer 7

Originate as “closed tubes” in almost all tissues (except CNS, epidermis and cartilage)

Capillary wall constructed of overlapping endothelial cells that respond to fluid pressure

Question 8

What are lymphatics?

Answer 8

Form from joining lymph capillaries

superficial lymphatics follow superficial veins
flow into lymph nodes in axillary (armpit), inguinal (groin) or cervical (neck) areas where they drain into deep lymphatics

deep lymphatics follow main vessels
lymph nodes either side of the aorta (para-aortic) drain the paired organs, nodes lying anterior (pre-aortic) the gut etc

Question 9

What are the superficial lymph nodes?

Answer 9

Question 10

What are the deep lymph nodes?

Answer 10

Question 11

Where does drainage from the 3/4 of the body apart from the Upper Right Quadrant drain into?

Answer 11

They drain into the left brachiocephalic vein in the thoracic duct.

Question 12

Where does drainage from the upper right quadrant drain into?

Answer 12

The right brachiocephalic vein check what it travels via i think its via right lymphatic duct though

Question 13

What does the immune system function rely on?

Answer 13

A dual circulatory system

Question 14

What are lymph nodes?

Answer 14

An important component of host defense

Filter lymphatics

LN represent the anatomical meeting place for cells of immune system and their exposure to antigen

Question 15

Lymph nodes of the MALT

Answer 15

Lymph nodules of the MALT

• Aggregates of lymphocytes in a reticular mesh
• No incoming lymphatic vessels
• May be isolated or form clusters (Peyer’s Patches in ileum; tonsil)

Question 16

What is the structure of a lymph node?

Answer 16

Question 17

Where does lymph fluid run along in the lymph node when it enters the lymph node?

Answer 17

The marginal sinus and trabeculae

Question 18

What is the lymphoid follicle?

Answer 18

They are aggregates of lymphocytes surrounding germinal centres within the lymph node. They mostly contain b lymphocytes.

Question 19

What are germinal centres?

Answer 19

They contain predominantly B cells but also contain t cells. found within the lymphcyte

Question 20

What is the para-cortex?

Answer 20

The T cell area in lymph nodes

Question 21

How do lymphocytes exit the lymph nodes?

Answer 21

Via the Efferent lymph vessels.

Question 22

Function of the spleen?

Answer 22

Directs immune responses to antigens in the blood

Important for clearance of effete red blood cells

Question 23

How does the spleen receive foreign antigens and lymphocytes?

Answer 23

Both through the bloodstream unlike the lymph node

Question 24

What are howell jolly bodies?

Answer 24

Erythrocytes with nuclear fragments

Question 25

Where is the spleen located?

Answer 25

Left Hypochondriac in abdominal wall between ribs 9, 10 and 11.

Question 26

What is the microanatomy of the spleen?

Answer 26

There is a white pulp and a red pulp. The red pulp carries out normal function and the white pulp carries out immunological function and is effectively a lymph node.

Question 27

what are the anatomical similarities between the spleen and Lymph nodes?

Answer 27

Question 28

What allows lymphocytes in secondary lymph tissue to home to their own compartments such as the paracortex or lymphocyte follicle?

Answer 28

chemokines

Question 29

Anatomy of GALT

Answer 29

Question 30

What helps organize lymphoid tissue architecture?

Answer 30

Non-hematopoietic stromal cells make chemokines that attract lymphocytes to their compartments. Think of the stromal cells and fibro blasts making train tracks in a balloon and the different railway tracks are where they are making their chemokines.