30. Central (primary) lymphoid organs. Differentiation of lymphocytes in central lymphoid organs.

Question 1

Central prmary lymphoid organs

Answer 1

-> bone marrow: 2 types - red (main blood forming organ) and yellow (made up of fat)

-> thymus: located near sternum
- immature T lymphocytes called thymocytes undergo proliferation, differentiation and apoptosis

Question 2

Structure of bone marrow

Answer 2

• in spongy bone
• consists of blood cells in dif stages of development

Question 3

Histological structure of thymus

Answer 3

parechymal organ divided into lobules separated by septae (connective tissue)
- cortex has procursors of T lymphocytes
- medull contains few lymphocytes

Question 4

Differentiation of B+T lymphocytes in central lymphoid organs

Answer 4

1. hematopoietic stem cell in the red bone marrow give rise to lymphoid stem cells
2. lymphoid stem cells become pro-B cells. they differentaite
3. some become T cells
4. as each lymphocyte develops in a central lymphoid organ, it reacts with a particular antigen

• How do we genetrate dif antigen receptors? COMBINATIONS

Question 5

Immune system self tolerence

Answer 5

• molecules are destroyed by apoptosis, leaving only those lymphocytes that react to foreign molecules