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Histology Flashcards

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1
Q

epithelia

A

singular: epithelium; a diverse group of tissues that include both surface epithelia and solid organs

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2
Q

surface epithelia

A

cover or line all body surfaces, cavities and tubes and form the interface between different biological compartments

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3
Q

keratin intermediate filaments

A

characteristic of epithelial cells, and can be used to recognise epithelial cells using immunohistochemistry

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4
Q

polarized (cells)

A

one side faces the basement membrane and underlying supporting tissues (the basal surface) and the other faces outwards (the apical surface).

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5
Q

three morphological classifications of surface epithelia

A

number of cell layers

type of cell (profile perpendicular to basement membrane)

special features (e.g. cilia, goblet cells)

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6
Q

glands

A

invaginations of epithelial surfaces which are formed during embryonic development by the proliferation of epithelium into the underlying tissues

often found in epithelia involved in secretion

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7
Q

exocrine glands

A

solid organs (epithelia) that are connected to the surface epithelium of by a branching system of ducts

e.g. major salivary glands, liver, pancreas (acinar tissue)

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8
Q

endocrine glands

A

solid organs (epithelia) that have lost their connection to the epithelial surface from which they developed and release their secretions directly into the blood

E.g. thyroid, anterior pituitary, adrenal, pancreas (islets of Langerhans)

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9
Q

simple epithelia definition and locations

A

surface epithelia consisting of a single layer of cells

almost always found at interfaces involved in selective diffusion, absorption, and/or secretion

provide little protection against mechanical abrasion and thus are not found on surfaces subject to such stresses

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10
Q

examples of flattened simple epithelia locations

A

ideally suited to diffusion and are therefore found in:

the air sacs of the lung (alveoli)
the lining of blood vessels (endothelium)
the lining body cavities (mesothelium)

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11
Q

metric resolution limit for the unaided human eye

A

0.2 mm (200 µm)

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12
Q

metric resolution limit for the light microscope

A

200 nm

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13
Q

metric resolution limit for the electron microscope

A

0.2 nm

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14
Q

RBC size

A

7-8 µm

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15
Q

Escherichia coli size

A

~2.5 µm

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16
Q

Powers of 10

A 
mm = visible with eye (macro -> collections of cells)
µm = visible with light microscope (cells -> organelles)
nm = visible with electron microscope (proteins -> molecules)
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17
Q

structural hierarchy btw molecules and human organ systems

A

chemical -> cellular -> tissue -> organ -> system

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18
Q

fixation (light microscopy)

A

the first step of tissue sample preparation for examination under a light microscope

small pieces of fresh tissue are placed in fixative solutions which generally cross-link proteins, inactivate degradative enzymes, and preserve cell structures

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19
Q

dehydration (light microscopy)

A

the second step of tissue sample preparation for examination under a light microscope

the fixed pieces undergo “dehydration” by being transferred through a series of increasingly more concentrated alcohol solutions, ending in 100% which effectively removes all water from the tissue

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20
Q

clearing (light microscopy)

A

the third step of tissue sample preparation for examination under a light microscope

removes the alcohol from the dehydration stem within a clearing solution that is miscible in both alcohol and melted paraffin

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21
Q

infiltration (light microscopy)

A

the fourth step of tissue sample preparation for examination under a light microscope

after clearing, the tissue is then placed in melted paraffin at 58°C, becoming completely infiltrated with this substance

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22
Q

embedding (light microscopy)

A

the fifth step of tissue sample preparation for examination under a light microscope

after infiltration, the tissue is placed in a small mold containing melted paraffin, which is then allowed to harden. The resulting paraffin block is trimmed to expose the tissue for sectioning (slicing)

(electron microscopy uses epoxy resins, which become much harder than paraffin to allow very thin sectioning)

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23
Q

microtome

A

used for sectioning paraffin-embedded tissues for light microscopy

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24
Q

sectioning (light microscopy

A

the sixth step of tissue sample preparation for examination under a light microscope

the embedded tissue specimen is mounted on a trimmed block with a rotating drive wheel that moves the tissue-block holder up and down

the specimen holder is advanced at a controlled distance, generally between 1 and
10 μm

after each forward move, the tissue block passes over the steel knife edge, which cuts the sections at a thickness equal to the distance the block advanced

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25
staining step (light microscopy)
the final step of ttissue sample preparation for examination under a light microscope after sectioning, paraffin sections are then adhered to glass slides, deparaffinized, and stained
26
most common staining methods used for | light microscopy in histology and pathology
Hematoxylin & Eosin (H&E) and Periodic acid-Schiff (PAS) staining
27
Hematoxylin & Eosin (H&E)
commonly used staining method for medical diagnosis (pathology) basophilic cell nuclei are stained purple while cytoplasm stains pink cell regions with abundant oligosaccharides on glycoproteins, such as the apical ends of the cells (glycocalyx) or the scattered mucus-secreting goblet cells, are poorly stained
28
Eosin
acidic stains cytoplasm pink/orange (eosinophilic) stains basic structures
29
Hematoxylin
basic stains acid nucleic acids (DNA, RNA) purple
30
Periodic acid-Schiff (PAS)
commonly used staining method most intense at the cell surface, where projecting microvilli have a prominent layer of glycoproteins and in the mucin-rich secretory granules of goblet cells cell surface glycoproteins and mucin are PAS-positive due to their high content of oligosaccharides and polysaccharides
31
fixation (TEM)
the first step of tissue preparation for TEM the tissue must be hardened and crosslinked, and osmium tetroxide (OsO4) is useful for crosslinking membranes and glutaraldehyde crosslinks proteins into a resistant 3D matrix (needs careful pH buffering, because it generates acid as it works. Sodium cacodylate is the most widely used buffer).
32
osmium tetroxide (OsO4)
useful for crosslinking membranes and glutaraldehyde crosslinks proteins into a resistant 3D matrix for TEM fixation requires careful pH buffering bc it generates acid as it works
33
sodium cacodylate
most commonly used buffer for TEM fixation if OsO4 is being used
34
dehydration (TEM)
the third step of tissue preparation for TEM since the specimen will be viewed in a vacuum, all water must be removed (water scatters electrons) usually accomplished with a dehydrating ethanol series from 70% to 100%
35
embedding (TEM)
the fourth step of tissue preparation for TEM (skips clearing and infiltration steps of light microscopy tissue preparation) soaks the dehydrated specimen in propylene oxide-containing epoxy or acrylic resin monomers the resin is crosslinked (cured) using heat, UV light, or chemical hardeners, depending on specific chemistry, and the specimen is now embedded in a solid block of plastic
36
sectioning (TEM)
the fifth step of tissue preparation for TEM the embedded specimen is sectioned using a microtome, which is a glass or diamond knife that can cut extremely thin sections (100 nm) such thin sections allow electrons to pass easily with moderate scattering, allowing image formation
37
staining (TEM)
the second step of tissue preparation for TEM organelles of interest must be electron dense to contrast with the background, and since electron density increases with atomic number, non-biological heavy atoms work best Sections are therefore often stained with osmium tetroxide, uranyl acetate, and/or lead citrate
38
osmium tetroxide
common staining solution for TEM
39
uranyl acetate
common staining solution for TEM
40
lead citrate
common staining solution for TEM
41
four types of tissues in the human body
connective (blood, bone) epithelium (lining all body cavities, glands) nerve (CNS, PNS) muscle (skeletal, cardiac, smooth)
42
basal lamina
lies at the interface of epithelial cells and connective tissue the basal laminae to two neighboring epithelia can fuse or appear to fuse in places where there is no intervening connective tissue nutrients for epithelial cells must diffuse across the basal lamina as small blood capillaries (being epithelial themselves) never enter an epithelium across a basal lamina, but nerve fibers normally penetrate this structure,
43
simple epithelium
a classification based on the number of layers from the basement membrane to the surface (all cells are in contact with the basement membrane)
44
stratified epithelium
a classification based on the number of layers from the basement membrane to the surface (two or more layers of cells)
45
columnar epithelium
a classification based on the shape of the individual cell (tall like a column) or, if stratified, the shape of the uppermost cell
46
cuboidal epithelium
a classification based on the shape of the individual cell (square like a cube) or, if stratified, the shape of the uppermost cell
47
squamous epithelium
a classification based on the shape of the individual cell (flat; Lat: squama = scales) or, if stratified, the shape of the uppermost cell
48
five main locations of simple squamous epithelium
the lining of heart, blood, and lymphatic vessel walls (endothelium) blood-tissue and lymph-tissue barriers serous membranes of plural and abdominal cavities (mesothelium) parietal layer of Bowman's capsule in kidneys plus thin loops of Henle pulmonary alveoli
49
basement membrane
the structure seen when components of a basal lamina are resolved with the light microscope
50
skeletal muscle
composed of large, elongated, multinucleated fibers that show strong, quick, voluntary contractions
51
cardiac muscle
composed of irregular branched cells bound together longitudinally by intercalated disks and shows strong, involuntary contractions
52
smooth muscle
composed of grouped, fusiform cells with weak, involuntary contractions. The density of intercellular packing seen reflects the small amount of extracellular connective tissue present
53
rouleaux
aggregates of RBC stacks which occur in small vessels
54
what germ embryonic layers form epithelial cells
all three germ embryonic layers form epithelial cells (endoderm, mesoderm, and ectoderm)
55
three main functions of epithelial cells
forming membranes (sheets of epithelial cells) covering body surfaces (e.g. skin) lining internal cavities (e.g. digestive, respiratory, cardiovascular, genitourinary) invaginates from surfaces to form secretory glands
56
epithelial cell structure
epithelial cells are separated from underlying tissue by a basement membrane, and epithelial cells in basement membranes are firmly attached to underlying connective tissue epithelial cells are avascular as nutrients and oxygen come from the underlying connective tissue (except for digestive tract epithelia, which can receive nutrients by apical absorption)
57
mesothelium
epithelial membranes lining serous body cavities
58
endothelium
epithelial membranes lining blood and lymph vessels and heart chambers
59
the three main epithelial membrane specializations
cell-cell junctions: form both mechanical and barrier (diffusive) functions projections: motile = cilia projections: non-motile = microvilli, stereocilla
60
what helps epithelial cells cope with stress and trauma of their cells
a high mitotic index, which means they are regenerative and proliferative
61
where are epithelia's stem cell population or "compartment" located
at the basal layer, next to the basement membrane
62
what two factors make epithelial cells susceptible to transformation (cancer)
1) high division rate | 2) relatively high exposure to carcinogens and pathogens, particularly viruses
63
papillomas
slow-growing tumors (benign) that arise from surface epithelia
64
adenomas
slow-growing tumors (benign) that arise from glandular epithelia
65
carcinomas
malignant neoplasms arising from surface epithelia
66
adenocarcinomas
malignant neoplasms arising from glandular epithelia
67
apical domain
the surface of the epithelium that faces the lumen or external environment
68
lateral domain
the geographic domain of epithelial cells which face neighboring epithelial cells linked to each other by cell adhesion molecules and junctional complexes
69
basolateral domain
the plasma membrane of an epithelial cell which is connected by sealing tight junctions and is distinct from the apical domain
70
stratified squamous endothelia - keratinized function
strong, sheer-resistant layer, which protects against abrasion and dehydration and prevents invasion by bacteria and viruses (this is b/c the apical keratinized cells are dead, ergo stronger but without organelles or nuclei) found on surfaces open to air (e.g. skin, hard palate)
71
stratified squamous endothelia - non-keratinized
a strong, sheer-resistant layer, which protects against abrasion and dehydration and prevents invasion by bacteria and viruses found on moist surfaces (e.g. esophagus, vagina, male and female urethra, cornea)
72
simple cuboidal epithelia structure and function
comprised of a spherical, centrally placed nucleus and has a protective function important in the formation of gland ducts (e.g., kidney collecting ducts) or as exocrine glands as an acinus (cluster) (e.g. salivary glands, pancreas)
73
acinus
a cluster of simple cuboidal epithelia that can function as exocrine glands E.g., salivary gland, pancreas
74
simple non-ciliated columnar epithelia structure
basal surface contacts the basement membrane, the apical surface contacts a lumen (and often contain microvilli), lateral surfaces contain anarray of junctional complexes has an ovoid nucleus that is centrally or basally positioned
75
simple non-ciliated columnar epithelia function
protection of wet surfaces nutrient absorption secretion (e.g., convoluted tubules of kidney, intestines, gallbladder, oviducts, uterus)
76
simple pesudo-stratified columnar epithelia structure and function
all cells attach to the basement membrane (thus ‘pseudo’, should be called simple epithelium), but only a subset of cells reach the lumenal surface lines the upper respiratory tract (respiratory epithelium) (e.g., nasopharynx, larynx, trachea, bronchi); a mucociliary escalator, if you will
77
simple ciliated columnar epithelia structure and function
some simple columnar have cilia on most cells (scattered among non-ciliated cells in the same sheet) and can have several hundred cilia cilia function to propel fluids & particles along surface, so mainly located in the female reproductive tract (oviduct)
78
stratified cuboidal epithelia structure and function
mainly protective, as it is more robust than single layer usually has two layers (e.g. sweat gland ducts, exocrine gland ducts) can contain goblet cells for mucus secretion and lubrication
79
stratified transitional epithelia function
restricted to lower parts of the urinary tract; thus often referred to as a urothelium adapts to lateral stretching forces, and impermeable – protects underlying tissues from urine
80
simple glandular epithelia locations
colon stomach eccrine sweat glands
81
compound glandular epithelia locations
sebaceous glands Brunner's glands of duodenum small salivary glands breast prostate
82
tight junctions
membrane specialization of epithelia, which seals neighboring cells together in an epithelial sheet to prevent leakage of molecules between them
83
adherens junctions
membrane specialization of epithelia, which joins an actin bundle in one cell to a similar bundle in a neighboring cell
84
desmosomes
membrane specialization of epithelia, which joins the intermediate filaments in one cell to those in a neighboring cell
85
gap junctions structure and function
membrane specialization of epithelia, which forms channels that allow small water-soluble molecules, including ions, to pass from cell to cell made up of clusters of closely packed connexons, as the connexon hemichannel in one cell membrane docks with a connexon hemichannel in an adjacent cell to form the channel
86
hemidesmosomes structure and function
membrane specialization of epithelia, which anchors the basal domain of a cell to the underlying basal lamina using intermediate filaments cytoplasmic plate associates with keratin (tonofilaments) outer membrane plaque contains integrins that bind tightly to laminin filaments in basement membrane
87
zonula adherens structure and function
AKA adherens junctions/belt desmosomes lies just deep to tight junctions (relative to the apical surface), and forms a continuous "belt" of cadherin around cells; cadherin binds to β-catenins in the cytoplasm joins actin filaments (microfilaments) rather than intermediate filaments from one cell to another
88
gap junction structure
made up of clusters of closely packed connexons and the connexon hemichannel in one cell membrane docks with a connexon hemichannel in an adjacent cell
89
zonula occludens functions
AKA tight junctions functions to strongly adhere adjacent cells together in epithelial sheets, and forms a primary barrier to the diffusion of solutes through the intercellular space by creating a boundary between the apical and the basolateral plasma membrane domains in endothelial cells, tight junctions form the basis for the blood-brain, the blood-ocular, and the blood-testes barriers
90
cadherin
associated with zonula adherens/adherens junctions and desmosomes, and it comprises the belt which forms outside the plasma membrane binds to β-catenins in the cytoplasm
91
macula adherens structure and functions
AKA desmosomes performs cell-cell adhesion via cadherins to join intermediate filaments connects to cytoskeletal tonofilaments (intermediate filaments - keratin) and to proteins that interact with the cytoplasmic domain of cadherin also in cardiac muscle (intermediate filament – desmin)
92
intermediate filament joined by desmosomes in cardiac muscle
desmin
93
connexons
consist of pairs of transmembrane channels that make up GAP JUNCTIONS hexameric, i.e. they consist of arrays of 6 connexin protein subunits
94
cilia definition and location
membrane specialization of epithelia; mobile extensions of the cell surface about 10-12 mm long, which are outgrowths from basal bodies at the apical surface in the cell (similar to centrioles) found in the respiratory system, and male and female reproductive tracts
95
cilia structure
9+2 microtubule core, dynein-driven movement (similar to the structure of flagella)
96
microvilli structure and function
membrane specialization of epithelia; projections from the apical surface which function to increase the surface area of a cell for absorption relatively rigid and ~ 1 μm long a core of cross-linked actin filaments extends to a supporting ‘terminal web’ located below the plasma membrane
97
stereocilia structure and function
membrane specialization of epithelia; very long specialized microvilli that are not actually cilia rigid with an actin bundle core found in the epididymis (involved in spermiogenesis - maturation) and the inner ear (involved in sound transmission)
98
structure subclasses of exocrine gland duct systems
simple (single duct) compound (duct divided)
99
structure subclasses of the secretory units of simple ducts of exocrine gland
tubular (straight, coiled, or branched) alveolar (straight, coiled, or branched)
100
structure subclasses of the secretory units of compound ducts of exocrine gland
tubular (straight or branched) alveolar tubuloalveolar
101
secretory product subclasses of exocrine glands
serous (low viscosity) mucous (high viscosity) glycoproteins serous & mucous
102
parotid gland morphology
compound tubuloalveolar, serous
103
submandibular gland morphology
compound tubuloalveolar, serous & mucous
104
sublingual gland morphology
compound tubuloalveolar, serous & mucous
105
functional classifications of exocrine glands
merocrine holocrin apocrine
106
merocrine glands
a functional classification of exocrine glands; secrete products, usually containing proteins, by means of exocytosis at the apical end of the secretory cells most exocrine glands are merocrine [μέρος - part, portion; κρῑ́νω - to separate]
107
holocrine gland
a functional classification of exocrine glands; secretion is produced by the disintegration of the secretory cells themselves as they complete differentiation which involves becoming filled with product E.g. sebaceous glands of hair follicles [ὅλος - whole, entire; κρῑ́νω - to separate]
108
apocrine gland
a functional classification of exocrine glands; secretion involves the loss of a large membrane-enclosed portion of the apical cytoplasm, usually containing one or more lipid droplets this apical portion of the cell may subsequently break down to release its contents during passage into the duct along with merocrine secretion, it is seen in mammary glands [ἀπό - away from; κρῑ́νω - to separate]
109
occludin, claudin-1, JAM

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