Introduction Flashcards
Histology
the study of cells
the precursor to pathology
cells
functional units of living organisms
differentiate
to perform special functions
tissue
cells with similar morphology/function
homogenous
organs
anatomically discreet collections of tissues that perform certain functions
parenchyma
cells that make up the functional elements of an organ
stroma
structural framework of an organ, background tissue
systems
tissues and organs organized
systems may be (2)
discreet entities (CNS) diffuse aggregates (immune system)
5 basic tissue types
blood connective tissue epithelium muscle nervous tissue
blood
fluid tissue, contained within vessels of circulatory system
only fluid tissue
connective tissue
surrounds and supports other tissue
underlies and supports
common in stroma
epithelium
covers body surfaces, lines cavities, and forms glands
EX. respiratory tract, GI tract
muscle
contains specialized contractile cells responsible for movement
nervous tissue
contains modified cells responsible for intercellular communication and coordination of body systems
unfixed tissues autolyze/denature because of
rotting which leads to protein denaturation
tissue denaturation can be prevented with
fixation in formalin
formalin
37% formaldehyde
formalin leads to
cross-linking of proteins, preservation of tissue
put cut tissues into
cassettes
dehydrate tissue through a
series of alcohol baths and clear with xylene
embedding
prevents the tissue from falling apart
embed the tissue in
liquid paraffin or plastic resin (MMA)
downside to resin
it is expensive and difficult to stain the sections
microtome
6-7 um
thin section of tissue
mount tissue on slides by
gluing the tissue onto the slide
then deparaffinize section
remove paraffin
rehydrate the tissue with
alcohol and xylene (reverse order of baths)
hematoxylin
dark blue
basic dye
stains acids (ie. nuclei)
basophilic
eosin
pink
acidic dye
stains bases (ie. proteins)
eosinophilic
GMS
silver stain (fungi)
gram stain
bacteria
after staining, add a coverslip for
protection
animal cells are surrounded by flexible
cell membranes called plasmalemma
plasmalemma functions as a
semi-permeable membrane (SPM)
allows the interior of the cells to communicate with its external environment
cell membrane forms a
phospholipid bilayer
amphoteric/amphipathic
hydrophilic portion contains
positively charged N groups and charged phosphate groups
hydrophobic portion contains
two long FA’s, covalently linked to glycerol
trilaminar appearance of cell membrane in EM
2 electron dense layers (hydrophilic, phospholipid heads)
separated by electron lucent layer (hydrophobic, FA tails)
fluid mosaic model
fluidity of the membrane increases with increas in temp and decrete with the saturation of FA’s
— helps regulate fluidity and stabilize membrane
cholesterol
as cholesterol increases,
the membrane stiffens and fluidity decreases
membrane proteins function (2)
cell-cell recognition
surface receptors
extrinsic/peripheral proteins
proteins on the surface of membrane
intrinsic/integral proteins
proteins incorporated within membrane
transmural/transmembrane
extend from one side of the membrane to the other
pores
openings in transmembrane proteins which are always open
channels
openings in transmembrane proteins which open and close
channels and pores are used for
active or passive transport of hydrophilic molecules
pumps
serve to transport ions across membrane
ex. Na/K pump
channels
allow passage of water soluble molecules via diffusion
receptor proteins
allow for cell recognition and binding on cell membrane
ex. immune mediated reactions
transducers
initiate enzymatic reactions following binding with ligand molecules
ex. hormones
enzymes
components of ion pumps and digestive action
structural proteins
adds mechanical stability to membrane
glycocalyx
membrane proteins/lipids which are conjugated with short polysaccharide chains containing glucose molecules
glycocalyx collectively refers to (2)
glycoproteins
glycolipids
functions of gylcocalyx (3)
protects surface of cell membrane
may be involved in cell recognition
important in mediating exchange between internal and external cell environment
simple diffusion occurs
down a concentration gradient
some agents pass directly through the plasma membrane, such as
lipids
gases (o2, co2)
some small hydrophilic molecules (water, urea, bicarbonate)
larger water-soluble molecules use
pores or channels in transmembrane proteins
facilitated diffusion requires
carrier molecules
facilitated diffusion relies on
passive diffusion and a concentration gradient
facilitated diffusion is also called
carrier-mediated diffusion
facilitated diffusion mechanism
reversible binding and unbinding to transport water-soluble, hydrophilic molecules
(ex. glucose, amino acids)
ion channels can be
gated or ungated
ungated ion channels
always open, pores
gated ion channels
can be open or closed, allows selective permeability
ion channels require the presence of
a stimulus to open
the stimulus causes
a conformational change of protein
voltage gating requires a
change in membrane potential to open
chemical gating requires
binding of a signaling molecule or neurotransmitter
both passive and facilitated diffusion are enhanced by an increase in
surface area of cell membrane via folding
aquaporins
important type of channel that uses facilitated diffusion
allows water to cross the pm faster than by simple diffusion alone
active transport is independent of
concentration (against a concentration gradient)
active transport occurs at
specialized “dynamic pore sites” (usually transmembrane proteins)
bulk (vesicular) transport requires
energy (ATP)
bulk transport
engulfment of molecules or particles by cytoplasmic extensions aka endocytosis
phagocytosis vs pinocytosis
phago: solid
pino: liquid
bulk transport resilts in the formation of membrane bound, endocytic vacuoles called
endosomes or phagosomes
receptor-mediated endocytosis
extracellular molecules (ligands) bind to receptor proteins, or clathrins, located in coated pits (caveolae) of cell membrane
clathrins
most common receptor protein
caveolar
coated pits
transcytosis
transport of material across or through a cell, via sequential endocytosis followed by exocytosis
