Histology Flashcards
Identify and discuss relevant characteristics
Name the structure; Identify PP, AP, P, H, V, O
Sagittal section through the pituitary. Anterior is to the right.
PP-neurohypophysis; AP-adenohypophysis; P-neurohypophysial tract; H-hypothalamus; V-third ventricle; O-probably optic chiasm
Identify and discuss relevant characteristics
Identify the structure, the names of the different sections and the tissue type
This shows the pituitary, including the pars distalis of the adenohypophysis (superior on image), which is glandular tissue, and the pars nervosa of the neurohypophysis (inferior), which is neural tissue. The reddish area in between is most likely the pars intermedia
Identify and discuss relevant characteristics
Identify tissue and relevant structures
This is a section of neurohypophysis. Fenestrated capillaries can be seen near axon terminals. Nucleated cells are pituicytes, similar in function to glial cells of the CNS
Identify and discuss relevant characteristics
Name the tissue, name the red-stained “things” (and what they actually are)
Neurohypophysis. Red stained structures are Herring bodies, unmyelinated dilations of neurohypophysial axons near the terminal end. They contain either AVP or OT(plusNP). Note fenestrated capillaries in close proximity. Nucleated cells are pituocytes, roughly equivalent to glial cells.
Identify and discuss relevant characteristics
Name the tissue. Identify three classes of cells based on their staining properties and give their relative abundance in this tissue. Where are do they tend to cluster?
Pars distalis of the adenohypophysis. First, note the capillaries and don’t confuse them with cells (light colored, no nuclei). Acidophils stain bright/reddish and compose 40% of the total cells (these will be somatotrophs and lactotrophs). They cluster at the periphery - most susceptible to trauma, most often give rise to tumors. Basophils stain dark and compose 10% of the tissue (gonadotrophs, thyrotrophs (most anterior), corticotrophs). Chromophobes play a supportive paracrine role for the other cells. They are the pale nucleated cells and make up 50% of the tissue
Identify and discuss relevant characteristics
Identify the tissue. Name the layers and the main product of each layer.
Adrenal gland. Capsule surrounds, in blue at top of image. Progressing in: Zona glomerulosa (aldosterone - not a component of HPA axis), Zona fasciculata (cortisol), Zona reticularis (DHEA). Medulla may be considered a second gland. Chromaffin cells derived from neural crest (rest of adrenal is from mesoderm) - only tissue in the body containing phenylethanolamine-N-methyltransferase, which converts norepi to epi. Produce both epi and norepi but epi is more significant
Adrenal medulla
Cords of polyhedral epitheliod chromaffin cells. Derived from neural crest; directly innervated by preganglionic sympathetic n.’s (splanchnic).
Granules in cytoplasm contain catecholamines
Gross specimen cross section - Adrenal Medulla
Chromaffin (“chromium affinity”) cells stain brown due to the oxidation of catecholamines to melanin when exposed chromium salts.
Chromaffin cells are also called pheochromocytes
Resting mammary gland - observe small lobules, lots of connective tissue relative to the rest of the tissue
Mammary gland - active. Observe hypertrophied, active lobules
Identify and discuss relevant characteristics
(slide shows pathology)
Thyroid in Graves disease - note significantly decreased colloid due to hyperactivity of T4/T3 synthesis and secretion
Parathyroid
Chief cells synthesize PTH
Oxyphil cells - no known function
Pancreas. Observe small islets of Langerhans amid exocrine pancreas tissue
Pancreas under high magnification - this specifically shows several clustered islets of Langerhans
Identify and discuss relevant characteristics
stromal cells (bone marrow)
part of central lymphoid tissue
stromal cells provide signals that direct development of progenitor cells into immature B cells
(recall immature → mature B happens in the periphery)
Identify and discuss relevant characteristics
thymic cortex
outermost part of the thymus, where immature T lymphocytes mature
Identify and discuss relevant characteristics
thymic corticomedullary junction
T cell progenitors (HSCs) enter; mature T cells leave
Identify and discuss relevant characteristics
thymic medulla
contains more mature, single-positive thymocytes, dendritic cells, and macrophages
Identify and discuss relevant characteristics
thymic cortical stroma
network of thymic epithelial cells where T cell precursors reside
provides unique microenvironment for T cell selection
has epithelial cells with long branching processes that express MHC-I and MHC-II - site of negative selection
Identify and discuss relevant characteristics
high endothelial venules (HEV)
(lymph nodes)
route of entry into lymph node for naive lymphocytes.
located in paracortical areas
Identify and discuss relevant characteristics
follicle (lymph node)
where B cells congregate
Identify and discuss relevant characteristics
cortex (lymph node)
outer area. contains follicles
Identify and discuss relevant characteristics
paracortical area (lymph node)
aka “deep cortex”
T cells diffusely scattered through this area
where free antigen is “trapped” on resident DC’s/macrophages
where migrating DC’s bring their antigens
thymus
Hassall’s corpuscles are a distinct histological feature
Observe dark cortex - lots of immature T cells.
Medulla much less densely populated - most developing TC’s will undergo apoptosis. Medulla contains more mature, single-positive TC’s; TEC’s force negative selection
Lymph node showing germinal centers
spleen - red pulp showing cords (lighter) and sinusoids (darker)
young thymus - well developed
old thymus
T cell production slows but already produced cells continue to be maintained by survival signals from peripheral lymphoid tissue
(tissue replaced by fat)
high endothelial venule - lymphocytes “squeezing” out of circulation to get into lymphoid tissue
Lymph node, high mag
In upper left corner, see a great, well-defined example of the medullary cords - where the (shorter-lived) plasmablasts develop, secreting antibody while other B’s are undergoing somatic mutation/isotype switch in the germinal centers.
Lighter areas are the sinuses, where efferent lymphatics are draining
spleen.
note in spleen trabeculae track blood vessels rather than lymphatics
abundant stromal cells support parenchyma
(spleen lacks cortex/medulla but still divided into B/T areas)
spleen: vascular sinusoids
spleen:
macrophages in red pulp phagocytizing old RBC’s
Peyer’s patch
small intestine
Identify and discuss relevant characteristics
Name the stain and what it is useful for
Identify background; negative; positive
Gram stain; bacterial peptidoglycan cell wall
Background - yellow
Negative - pink/red (LPS allows diffusion of crystal violet dye from membrane)
Positive - purple (retains crystal violet stain)
Identify and discuss relevant characteristics
Name the stain and what it is useful for
Identify background; negative; positive
Periodic acid-Schiff (PAS); polysaccharides and mucous membranes. Useful for fungi, basement membrane
Negative: light pink
Positive (organisms): bright pink
Identify and discuss relevant characteristics
Name the stain and what it is useful for
Identify background; negative; positive
Grocott methenamine silver (GMS) - useful for fungi; mucopolysaccharides in their cell walls react with silver nitrate
Background green
Positive black
Identify and discuss relevant characteristics
Name the stain and what it is useful for
Identify background; negative; positive
Acid-fast stain; useful for bacteria with mycolic acid in cell wall (mycobacteria)
Background: blue
Positive: retains stain, colored red
suppurative inflammation in pneumococcal pna
Thickened interstitum, profusion of PMN’s
example of noncaseating granuloma
