Quiz 3 - histology Flashcards
what is histology?
Microscopic study of the tissues of the body and how these tissues are arranged to constitute organs
Tissues contain:
cells
extracellular matrix (ECM)
what are integrins?
Principal receptors used by cells to bind to the extracellular matrix
histological processing: paraffin sectioning
fixation
dehydration
clearing
infiltration
embedding
trimming
sectioning
mounting
staining
fixation
Smallpiecesoftissueareplacedinsolutionsofchemicals thatcrosslinkproteinsandinactivatedegradativeenzymes,whichpreserve cellandtissuestructure. E.g. paraformaldehyde
dehydration
Thetissueistransferredthroughaseriesofincreasinglyconcentratedalcoholsolutions,endingin100%,whichremoveswater
clearing
Alcoholisremovedinorganicsolventsinwhichbothalcoholandparaffinaremiscible. E.g. Xylene or cedarwood oil
infiltration
Thetissueisthenplacedinmeltedparaffinuntilitbecomescompletelyinfiltratedwiththissubstance.
embedding
Theparaffin-infiltratedtissueisplacedinasmallmoldwithmeltedparaffinandallowedtoharden.
trimming
Theresultingparaffinblockistrimmedtoexposethetissueforsectioning(slicing)onamicrotome.
sectioning
block of paraffin sliced into thin, transparent sections (1 – 50 um) with a microtome
mounting
sections attached to glass slide with mounting medium e.g. permount
staining
sections placed in dyes to visualize components
freezing creates a hard tissue that can be what?
cut easily without parafin
for biopsies & histochemical studies using enzymes freezing does what?
faster
freezing does NOT inactivate enzymes
studies of lipids in tissue
small piece of tissue is frozen in _________ then sectioned in a _________________
liquid nitrogen
cryostat microtome
basic dyes bind to what ?
bind to basophilic cell components with a negative charge e.g. nucleic acids (DNA in nucleus)
acidic dyes bind to what?
bind to acidophilic cell components with a positive charge e.g. proteins such as collagen in ECM
what is the most common staining combination?
hematoxylin & eosin
hematoxylin
basic dye
blue/purple
nuclei
eosin
acidic dye
pink
ECM
Histological processing may distort tissue causing abnormalities not present in living tissue called what?
artifacts
what causes shrinkage of tissue? which can create what?
fixative or heat
artificial space between cells of ECM
2-D appearance varies depending on . . .
plane of section
4 general types of tissues in the body
- connective
- epithelial
- nervous
- muscular
which tissue is most abundant & widely distributed of the primary tissues?
connective tissue
5 main types of connective tissue
fibrous connective tissues
adipose tissue
cartilage
bone
blood
what is fibrous connective tissue specialized to do?
physically support & connect other tissues & maintain the water required for metabolite diffusion to & from cells
what does fibrous connective tissue primarily consist of?
extracellular material
cells of fibrous connective tissue
fibroblasts
macrophages
mast cells
plasma cells
adipocytes
what are fibroblasts?
the major cells of connective tissue proper, are elongated, irregularly shaped cells with oval nuclei that synthesize and secrete most components of the ECM
what are macrophages?
short lived cells that differentiate in connective tissue from precursor cells,
what do macrophages function in?
ECM turnover, phagocytosis of dead cells and debris, and antigen presentation to lymphocytes.
where do mast cells originate?
from blood cell precursors
what are mast cells filled with . . .for the release of . . .?
granules for the release of various vasoactive agents and other substances during inflammatory and allergic reactions.
what are plasma cells?
short-lived cells that differentiate from B lymphocytes
what are plasma cells specialized for?
the abundant secretion of specific antibodies (immunoglobulins)
what are adipocytes? and where are they found?
fat cells
in the connective tissue of many organs
what are fibers?
elongated structures formed from proteins that polymerize after secretion from fibroblasts
The three main types of fibers:
collagen
reticular
elastic
Collagen and reticular fibers are formed by
proteins of the collagen family
Elastic fibers made mostly of what?
the protein elastin
These fibers are distributed _____________ among the different types of connective tissue
unequally
what is The most important and abundant fibers of connective tissue?
collagen
Synthesis of collagen by fibroblasts involves what?
posttranslational modifications in the RER, and formation of helical trimeric subunits of procollagen
what is required for proper synthesis?
vitamin C
what is the Most numerous type of collagen?
collagen type I
where is collagenI found?
tendons, bones, skin, muscles
Adjacent rodlike subunits of the fibrils are staggered with small gaps (lacunar regions) between their ends
transverse striations
what does collagen type II occur as?
occurs as fibrils but does not form fibers or bundles
what is collagen type II?
Loose aggregates of thin fibrils
collagen type II is predominate in ________ and _______________.
hyaline
elastic cartilage
collagen type II is Especially abundant in what?
articular cartilage
collagen type III form a meshwork in . . .
lymphoid organs: liver, bone marrow, lymph nodes
what does collagen type III form?
an extensive network (reticulum) of thin fibers for the support of many different cells
where is collagen type VII found?
basal lamina of basement membrane
what are collagen type VII called?
anchoring fibers
what is elastic fiber made with ?
fibrillin and elastin
what do elastic fibers form?
sparse networks interspersed with collagen bundles in many organs
where are elastic fibers found?
fibrous connective tissue as well as cartilage, blood vessels, and lungs
In the wall of large blood vessels, elastin forms fenestrated sheets called . . .
elastic lamellae
what is ground substance?
fills the space between cells and fibers
ground substance is a Complex mixture of three major kinds of macromolecules:
glycosaminoglycans (GAGs)
proteoglycans
glycoproteins
characteristics of ground substance:
highly hydrated
transparent
very viscous
GAGs are what?
Large polysaccharide structures that trap water (hydrophilic)
long polymers of repeating disaccharide units
what is The largest and most ubiquitous GAG ?
hyaluronic acid
what is hyaluronic acid’s important role?
allowing molecular diffusion through connective tissue and in lubricating various organs and joints
sulfated GAGs Bound to core proteins forming repeating chains along the length of the core protein forming what?
proteoglycans
where are sulfated GAGs synthesized?
golgi complex
4 major GAGs found in proteoglycans:
dermatan sulfate
chondroitin sulfates
keratan sulfate heparan sulfate
what are proteoglycans?
core protein covalently attached to various numbers and combinations of the sulfated GAGs
proteoglycans synthesize on ______ and mature in _________________
RER
golgi apparatus
what are aggrecan?
Large core protein bound to chondroitin and keratin sulfate chains
where is aggrecan abundant in?
cartilage
what is fascia
facilitates gliding of muscles
what are glycoproteins?
multiadhesive glycoproteins found in ground substance of fibrous connective tissue
glycoproteins are synthesized largely by what?
fibroblasts
glycoproteins are binding sites for ?
integrins, collagens and certain GAGs
what are integrins?
integral membrane proteins
integrins act as what?
matrix receptors for specific sequences on laminin, fibronectin, some collagens, and other ECM proteins
main types of fibrous connective tissue:
loose
dense
loose =
more ground substance, less fibers
dense =
more fibrous proteins, less ground
loos is made up of what?
areolar
reticular
dense is made up of what?
regular
irregular
Areolar connective tissue - microscopic appearance:
Fibroblasts, collagen/elastic fibers, blood vessels, and “empty” space = ground substance
areolar connective tissue - functions:
Binds epithelia to deeper tissues, allows passage of nerve and blood vessels, provides space for immune cells
areolar connective tissue - representative locations:
Underlies all epithelia, in serous membranes surrounding organs
reticular connective tissue - microscopic appearance:
Loose network of reticular fibers (type III collagen) and cells
reticular connective tissue - functions:
Forms supportive framework for lymphatic organs and slows down movement of fluid
reticular connective tissue - representative locations:
Spleen, liver, lymph nodes
dense regular connective tissue - microscopic appearance:
Densely packed, parallel type I collagen fibers arranged in line of pull
Few blood vessels = hard to heal
Compressed fibroblast nuclei
dense regular connective tissue - functions:
provides tensile strength (resists stretching), but is pliant (bends)
resists tension exerted in the axis parallel to the direction the fibers run
Transfer forces to bone
dense regular connective tissue - representative locations:
Tendons, ligaments, fascia; heart valves
