Lymphoid Tissue

Question 1

What are two different systems that provide us with immunity

Answer 1

1. Innate immune system (lacks immunological memory)

2. Adaptive immune system (high specificity and memory)

Question 2

Name the components of the innate immune system

Answer 2

1. Barriers against invasion (skin)
2. Phagocytes (macrophages and neutrophils)
3. Complement (plasma proteins)
4. Extracellular killers (lymphocytes and eosinophils)

Question 3

What is the major role of the innate immune system

Answer 3

Destruction of foreign invaders; ability to distinguish ‘self’ from ‘non-self’ is absolutely critical

Question 4

What is the adaptive immune system based on

Answer 4

Lymphocytes and a vast array of genetically determined cell surface receptors

Question 5

How are lymphoid organs connected to one another

Answer 5

Through communication between the blood vascular and lymph vascular systems

Question 6

What are primary lymphoid organs, and where are they in humans

Answer 6

Sites of lymphocyte production and maturation: bone marrow and thymus

Question 7

What are secondary lymphoid organs, and what are examples in humans

Answer 7

Sites to which lymphocytes migrate and where they aggregate in large number: spleen, lymph nodes, and lymph nodules

Question 8

What are the 3 principal forms of lymphocytes

Answer 8

1. B cells (produce antibodies)
2. T cells (participate in cellular immunity)
3. Natural killer cells (killer virus-infected cells, and some tumour cells)

Question 9

What is the term used for the process by which cells of the immune are identified

Answer 9

Done using immunohistochemistry, termed Cluster Designation (CD) molecules

Question 10

How many lobes form the thymus, and what separates them

Answer 10

It has two lobes subdivided by septa

Question 11

Describe the structure of the lobules

Answer 11

1. Outer cortex that is highly cellular

2. Less cellular inner medulla

Question 12

What part of the thymus lobule stains darker

Answer 12

The highly cellular cortex

Question 13

What cells exist within the thymus

Answer 13

1. T cells
2. Epithelioreticular cells
3. Macrophages (cortex)

Question 14

What % of immature T cells will ‘fail’ the process of maturation

Answer 14

Around 98%

Question 15

Describe the movement of mature T cells through the thymus

Answer 15

Cortex -> medulla -> blood vessels

Question 16

Name the whorls of epithelial cells with a keratin core that accumulate in the thymus’ medulla

Answer 16

Hassall’s corpuscles

Question 17

Describe 3 functions of the lymphatic system

Answer 17

1. Drainage of lymph into the vascular system
2. Surveillance of tissue for signs of antigens from foreign invaders
3. Delivery of absorbed fats from the small intestine into the vascular system

Question 18

What are lymphatic vessels lined with interiorly

Answer 18

Endothelium

Question 19

What are lymph nodes

Answer 19

Encapsulated, highly organised structures interposed along larger lymph vessels

Question 20

How do lymphocytes enter the lymph nodes

Answer 20

1. Via the incoming lymph

2. From the bloodstream

Question 21

Describe the structure of a secondary follicle within a lymph node

Answer 21

1. Germinal centre (less densely packed; dividing B cells)

2. Surrounded by a mantle zone (resting B cells)

Question 22

What region of a lymph node is populated mostly by T cells

Answer 22

The paracortical region; contains cuboidal epithelium

Question 23

What cells exist within the medulla of a lymph node

Answer 23

1. Plasma cells

2. Macrophages

Question 24

What does GALT, MALT, and BALT stand for

Answer 24

GALT = gut-associated lymphoid tissue
MALT = mucosa-associated lymphoid tissue
BALT = bronchial-associated lymphoid tissue

Question 25

Within the tonsils, what are the deep crypts lined with

Answer 25

Stratified squamous epithelium and the lymphoid follicles

Question 26

What are the functions of the spleen

Answer 26

1. Produce immune response against blood-borne antigens
2. Removal of particulate matter and aged blood cells (mostly RBCs)
3. Production of blood cells during foetal life

Question 27

Describe the structure of the spleen

Answer 27

Whitish nodules 0.5-1.0mm in diameter (white pulp) embedded in deep red tissue (red pulp)

Question 28

How does the spleen recognise old from young red blood cells

Answer 28

Blood cells have to pass through the complex vasculature (requires them to deform); old red blood cells cannot do this and will be phagocytosed by macrophages