The thymus Flashcards
Where is the thymus located? When does it atrophy and what is the result of the atrophy?
Located in mediastinum
* Atrophies after puberty
* Diminishing effectiveness of immune system
How lobes does the thymus have
divided into two thymic lobes
what does the septa in the thymus do?
Septa divide lobes into smaller lobules
What does the thymic lobule contain
Contains a dense outer cortex and a pale central
medulla
Where do lymphocytes divide in
the cortex
T cells from lymphocytes migrate into the
medulla
Lymphocytes contain mature
Mature T cells leave the thymus by medullary blood vessels
Three Functions of the Spleen
- Removal of abnormal blood cells and other blood
components by phagocytosis - Storage of iron recycled from red blood cells
- Initiation of immune responses by B cells and T cells
* In response to antigens in circulating blood
4 Properties of immunity
- Specificity
- Versataity
- Memory
4.Tolerance
Specificity
Each T or B cell responds only to a specific antigen and ignores all others
Versatality
The body produces many types of lymphocytes
* Each fights a different type of antigen
* Active lymphocyte clones itself to fight specific
antigen
Memory
- Some active lymphocytes (memory cells):
- Stay in circulation
- Provide immunity against new exposure
Tolerance
- Immune system ignores “normal” antigens (self-antigens)
What are the 2 main divisions
- Cell-mediated immunity (T cells) (aka “Cellular”)
- Antibody-mediated immunity (B cells)
(aka “Humeral Immunity”)
How much of leukocytes do lymphocytes make up and are most stored or circulating?
- Make up 20–30% of circulating leukocytes
- Most are stored, not circulating
