MI 04a: Histology Flashcards
Thymus develops from (X) cells, derived from (Y), as well as from underlying (Z).
X = epithelial Y = endoderm Z = mesenchyme
Epithelial reticulum (cytoreticulum) forms when cells of (X) spread apart, but remain connected via (Y).
X = epithelial cords Y = desmosomes
List the basic functions of epithelioreticular cells in (X) organ.
X = thymus
- Stromal support
- Barrier
- Developmental support
- Endocrine function
- Hassall’s corpuscles
What’s unique about the stroma of the thymus?
No reticular fibers; made up of cytoreticulum (stellate cells, linked via desmosomes)
Blood-thymus barrier formed by (X) cells that envelop (Y) in (Z) part of thymus.
X = epithelioreticular Y = continuous capillaries Z = cortex
(X) cells monitor development of thymocytes in thymus and play key role in selecting the useful thymocytes.
X = thymic nurse cells
Thymic (X) cells secrete peptides that serve (paracrine/autocrine/endocrine) functions. How do these affect thymocytes?
X = hormone-secreting;
Paracrine and endocrine;
- Differentiation
- Expression of surface molecules
Hassall’s corpuscles are characteristic of (X) part of (Y) organ. They’re composed of (round/flat) (Z) cells.
X = medulla
Y = thymus
Flat;
Z = epithelioreticular
Thymocyte precursors migrate from (X) to thymus via (Y). What attracts them to thymus?
X = bone marrow Y = systemic circulation
Thymotaxic factors (secreted by epithelioreticular cells)
In thymus, precursors begin proliferation/differentiation in (X) and get progressively displaced (inward/outward) toward (Y).
X = cortex
Inward;
Y = medulla
Only developing thymocytes with which characteristics survive selection?
Bind weakly to self-MHC molecules, but NOT autoreactive
Surviving thymocytes enter (X) of thymus as (Y) cells.
X = medulla Y = mature, naive T lymphocyte
GALT found in (X). BALT found in (Y). CALT found in (Z).
X = gut Y = bronci/trachea Z = cutaneous tissue (dermis/epidermis)
(X) tissue overlying MALT is modified and contains special cells, depending on location of the MALT. Give examples.
X = epithelial
- M cells (GI tract)
- Langerhans cells (epidermis)
M cells are a type of (X) cells in (Y) location with (Z) function.
X = epithlial (modified) Y = GI tract (overlying MALT) Z = antigen-transport
Langerhans cells are a type of (X) cells in (Y) location with (Z) function.
X = Dendritic (modified epithlium) Y = epidermis (overlying MALT) Z = antigen presenting
In which type of epithelial structure would you find reticulated epithlium? What’s the purpose?
Stratified squamous (note: simple columnar epithlia don’t need this modification)
Modified with channels to allow passage of lymphocytes
T/F: MALT has well-defined capsule.
False
T/F: MALT has efferent lymphatic vessels.
True
T/F: MALT has afferent lymphatic vessels.
False
Lymphocytes leave MALT via (X).
X = efferent lymphatic vessels
T/F: HEV found in all MALT and lymph nodes.
True
HEV are special (X), whose walls are lined by (Y).
X = post-capillary venules Y = unusual endothelial cells
Function of HEV is to:
- Bind lymphocytes (slow their flow)
- Separate them from blood
- Allow their migration (through wall) into specific lymph tissue
Aside from lymphocytes, which cells/substances pass through HEV?
- Macrophages
2. Tissue fluid (draining out into circulation)
Stroma of lymph nodes is composed of:
- Reticular fibers (collagen type III)
- Reticular cells
- Endothelial cells and macrophages
Macrophages in stroma of lymph node has which functions?
- Phagocyte
- APC
- Contributes growth factors (supplements cytokine production by lymphocytes)
Abs produced by plasma cells in medulla is released into (X), from which it passes out of lymph node via (Y).
X = medullary sinus Y = efferent lymphatics
T cells in lymph node proliferate in which part of organ?
Paracortex
Blood vessels are distributed in (X) part of lymph node, after entering and exiting at the organ’s (Y).
X = cortex Y = hilus
Where might you find HEV in lymph node?
Interfollicular area and in deep paracortex
B and T cells enter lymph node via:
HEV
Most lymphocytes leaving lymph nodes are (X) cells that (have/haven’t) encountered antigen.
X = naive
Haven’t
Largest lymphoid organ in body.
Spleen
Two key functions of spleen
- Monitor blood/respond to blood-borne antigens
2. Destruction of ineffective RBC/platelets
(X) are encased by white pulp of spleen. What’s the white pulp composed of?
X = central arteries;
- PALS (T-cells)
- Splenic follicles: marginal zone (macrophages and splenic sinuses) and germinal center (B cells)
List pathway of closed circulation in spleen.
- Trabecular artery
- Central artery
- Radial artery
- Splenic sinus
- Trabecular vein
Red pulp of spleen composed of:
- Splenic sinus
2. Splenic cord (cords of BIllroth)
List pathway of open circulation in spleen.
- Trabecular artery
- Central artery
- Radial artery
- Splenic cord (cord of Billroth)
- Splenic sinus
- Trabecular vein
Most arterial blood flows through (open/closed) circulation of spleen. It’s a (shorter/longer), (slower/faster) path.
Closed;
Shorter, faster
The reason the open circulation of spleen exists is that (X) and (Y) are major sites for (Z).
X = sheathed capillaries (sheath of macrophages) Y = splenic cords Z = clearance of cell debris and old blood cells
In spleen, atypical, elongate endothelial cells, called (X) cells, line (Y) and rest on encircling bands of (Z).
X = stave Y = splenic sinus Z = reticular fibers
Blood cell monitoring in spleen: blood cells in (X) must traverse longitudinal interendothelial slits in order to reach (Y). Aged/inflexible/damaged RBCs have difficult time doing this.
X = splenic cord Y = splenic sinus lumen
