Histology- Lymphatics
Terms
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- Where is the Marginal Zone of the Spleen?
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Between the white pulp and the red pulp.
The site of immune response initiation (BORDER PATROL)
- What are the CD surface markers on the T-cell?
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1) Helper T cells (CD4+)
2) Cytotoxic T cells (CD8+)
3) Suppressor T cells (both) - How is the RED pulp organized?
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It is organized into Splenic cords of BILLROTH separated by splenic sinuses.
You will find: Macrophages, Plasma Cells, Lymphocytes, and RBC's. - What in the heck are thymic epitheliocytes?
- 1) Form a cellular meshwork INTO which immature T-Cells are tightly packed
- What are the major types of lymphoid tissue?
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1) Diffuse
2) Lymph nodule
3) Lymph node - What is in the Thymic medulla?
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1) Mature T-cells
2) Thymic epitheliocytes
3) Hassall's corpuscles
- What is diffuse lymphoid tissue?
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It is a loose collection of lymphocytes scattered though the other tissues
Particularly in the CT underlying epithelia that are involved in transport of materials from the outside world (GUT, LUNGS) - As T-cells mature, they express:
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1) T-cell receptors that are antigen specific
- What do you find in the inner cortex of the thymus?
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1) T-Cells
2) Dendritic cells (APC fxn)
3) Macrophages
4) Fibroblasts-reticular cells-reticular fibers-meshwork - Epitheliocytes of the thymic cortex secrete:
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Thymosin, serum thymic factor, and thymopoetin
These transform immature t-cells into mature T-Cells - What do you find in the medulla of a lymph node?
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1) lymphocytes
2) plasma cells
3) Macrophages very numerous with lots of phagocytosis
4) Fibroblasts-meshwork
- What attracts progenitor t-cells from bone marrow to the thymus?
- Thymotaxin (epitheliocyte)
- Describe the circulation of lymph through system
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Fluid moves out of capillaries into the tissue and some is picked up by lymphatics.
Thence up a chain of lymph nodes through multiple Afferents, Subcapsular (marginal sinus), Cortical sinus, Medullary sinus, and finally through Efferent lyphatics. (ASCME) (If you don't know, ask me)
Finally into the thoracic duct and into venoud blood circulation - Where are hassalls corpuscles and what do they look like?
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They are found in the nedulla of the thymus
They are WHORL like structures composed of keratinized thymic epitheliocytes - What can you find in the Spleen?
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1) White pulp
2) Marginal Zone
3) Red Pulp - What happens to the thymus as we age?
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1) at birth, thymus is fully developed
2) Childhood, involution begins
3) Puberty, Involution greatly increases
4) Adult: transformed into mainly adipose tissue with isolated areas of lymphatic tissue that remains the source of T cells though out life. - What is a germinal center?
- A region of lymphocytes where B-cell clones are growing
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Blood thymus barrier:
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1) Only in the THYMIC CORTEX
2) Assures T-cell maturation in antigen free environment
3) Consists of Tight JXNs with nonfenestrated endo cells, basal lamina and thymic epitheliocytes - What happens in the marginal zone?
- Foreign antigens are greeted by the APC's and arrested and brought to their favorite cell, the macrophage
- Thymic Cortex consists of:
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1) Immature T-cells (thymocytes)
2) Thymic epitheliocytes - What does PALS mean?
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Periarterial Lamphatic Sheath
The sheath of T-cells around the central artery of the white pulp - Lymph Node has three layers
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1) Outer cortex
2) Inner cortex
3) Medulla - The outer cortex of the Lymph node consists of:
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1) B-cells organized into a lymphatic follicle (germinal center if immune response) -> plasma cells
2) Helper T-cells
3) Follicular dendritic cells
4) Macrophages
5) Fibroblasts (AGYROPHILIC reticular cells which secrete reticular fibers that form the reticular meshwork) - What is a lymph nodule?
- It is a collection of lymphocytes organized into a germinal center
- What is in the splenic white pulp?
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1) B cells (lymphatic follicles that surround a central artery)
2) T cells (organized into a sheath around the central artery (PALS) which is a thymic dependent zone similar to the inner cortex ot eh lymph node - Lymph Node defined:
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1) A true organ with capsule, arteries and veins, afferent and efferent lymphatic vessels
2) Contains lymph nodules
3) Contains channels for allowing filtering of the lymph(subcapsular sinus and sinusoids) - What happens in the Red Pulp?
- It is the site of RBC removal
- How does the blood flow through the spleen?
- Blood flows through the splenic artery, trabecular arteries, central arteries, penicillar (straight) arteries, splenic sinus, trabecular veins, and the splenic vein.