Lymphoid System

Question 1

Where do B cells and where do T cells mature

Answer 1

B - Bone Marrow

T - Thymus

Question 2

Secondary Lymphoid Tissue

Answer 2

Lymph Nodes
Spleen
Mucosa associated lymphoid tissue (MALT) (e.g. tonsils or other diffuse cells throughout various systems)

Question 3

What is lymph

Answer 3

Interstitial fluid from capillary beds that is not picked up by venules - 20% of interstitial fluid

Question 4

How is lymph returned to the circulatory system

Answer 4

Via Lymphatic Vessels

Question 5

Why does the body not pick up all the interstitial fluid instead of going via lymphatic vessels

Answer 5

On the way to the venules, they go through lymph nodes

Question 6

Lymphoedema

Answer 6

Blocked lymph vessels causing swelling

Can be side effect of radiotherapy

Question 7

What kinds of surfaces have antigen presenting cells and what are they

Answer 7

Exposed surfaces - Digestive system, Respiratory System, Skin

Dendritic Cells/Macrophages

Question 8

Shape of lymph nodes and their structure

Answer 8

Bean Shaped

Composed of a cortex and medulla supported by a reticular network and surrounded by a connective tissue capsule

Question 9

How does lymph enter, travel through and leave lymph nodes

Answer 9

Via afferent lymphatics into a network of sinuses (subcapsular, corticular and medullary) which ultimately drain into efferent lymphatics

Macrophages and dendrites enter through lymphatics as well

Question 10

Where are lymphoid follicles relative to the lymph nodes

Answer 10

On the superficial cortex/outside of the lymph nodes

Question 11

Where does lymph node blood supply enter and leave

Answer 11

At the hilum along with the lymphocytes

Question 12

What happens to lymphocytes in a lymph node if they do not recognise any antigen

Answer 12

They leave within a few hours and might go to another lymph node to find antigens there

Question 13

How often does an average lymph node turn over its lymphocyte population in a day

Answer 13

About 10-48 times per day - note that lymphocytes really are not static

Question 14

Annotate

Answer 14

Question 15

Describe Antigen Presenting Cells

Answer 15

Macrophages or dendritic cells that phagocytose intruders and present ingested proteins on MHC [Major Histocompatibility Complex] on their surface

Question 16

Describe immunity in the lymph node

Answer 16

APCs travel to paracortex to present protein fragments leading to T cell activation and proliferation

B Cells pick up the antigen in the follicle, ingest it and move to B/T cell zone interface

Activated T & B cells meet at B/T cell zone interface and the specific T helper cell activates the B cell to proliferate and mature

Activated B cell moves back to cortex to proliferate and mature resulting in a germinal centre

Question 17

What happens to the size of lymph nodes with higher proliferative activity

Answer 17

They enlarge

Question 18

When do lymph nodes enlarge

Answer 18

When there is an infection in the body
When they are infected
Tumour of the lymphoid system (Lymphoma)
When tumour metastasises to nearby lymph nodes

Question 19

Which cells are generally associated with Lymphomas

Answer 19

Lymph nodes and spleen cells

Lymphocytes in bone marrow and blood are sometimes involved but more commonly so in leukemia

Question 20

What does the spleen do

Answer 20

Does to blood what lymph nodes to for lymph
Filters circulating blood through sinusoids to remove effete RBCs (approx 3 months) and platelets

Phagocytoses blood borne microorganisms and mounts an immune response to antigens in the blood

Question 21

What happens following a splenectomy

Answer 21

Infection and an increased number of deformed RBCs/Platelets

Question 22

Describe the structure of the spleen

Answer 22

Comprised of a collagenous capsule surrounding a reticulin network (which supports many sinusoids [red pulp] and lymphoid aggregates [white pulp])

White pulp equivalent to paracortex and superficial cortex of lymph node

Blood supply through hilum via splenic artery and vein

Question 23

What happens to blood entering the spleen

Answer 23

Ends up in sheathed capillaries lined with macrophages

Bad cells can’t squeeze through gaps of venous sinuses and are phagocytosed; good cells pass into sinuses which pass drain into veins

Question 24

Describe tissue of Mucosa Assosciates Lymphoid Tissue (MALT)

Answer 24

Single cells or aggregates of lymphocytes;

contains lymph follicles or nodules just underneath epithelia with no distinct connective tissue capsule

Question 25

Where is MALT frequently seen and what commonly occurs in it

Answer 25

Frequent in airways and digestive tract

It is the primary site of antigen presentation and B- and T cell activation/proliferation