Introduction Flashcards by sophie rosen

Histology

the study of cells

the precursor to pathology

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cells

functional units of living organisms

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differentiate

to perform special functions

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tissue

cells with similar morphology/function

homogenous

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organs

anatomically discreet collections of tissues that perform certain functions

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parenchyma

cells that make up the functional elements of an organ

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stroma

structural framework of an organ, background tissue

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systems

tissues and organs organized

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systems may be (2)

discreet entities (CNS)
diffuse aggregates (immune system)

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5 basic tissue types

blood
connective tissue 
epithelium
muscle
nervous tissue

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blood

fluid tissue, contained within vessels of circulatory system
only fluid tissue

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connective tissue

surrounds and supports other tissue
underlies and supports
common in stroma

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epithelium

covers body surfaces, lines cavities, and forms glands

EX. respiratory tract, GI tract

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muscle

contains specialized contractile cells responsible for movement

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nervous tissue

contains modified cells responsible for intercellular communication and coordination of body systems

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unfixed tissues autolyze/denature because of

rotting which leads to protein denaturation

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tissue denaturation can be prevented with

fixation in formalin

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formalin

37% formaldehyde

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formalin leads to

cross-linking of proteins, preservation of tissue

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put cut tissues into

cassettes

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dehydrate tissue through a

series of alcohol baths and clear with xylene

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embedding

prevents the tissue from falling apart

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embed the tissue in

liquid paraffin or plastic resin (MMA)

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downside to resin

it is expensive and difficult to stain the sections

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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