Week 2 Cells, Epithelial Cells

cellular level

basis of pathophysiology

cytoplasm

surrounded by the plasma membrane, intracellular fluid

plasma membrane

surrounds the cytoplasm, separates the cell and its organelles from the internal environment of the body

nucleus

organelle surrounded by nuclear membrane contains DNA

nuclear membrane/envelope

separates the nuclear fluid and nucleic acids from the cytoplasm

Smooth ER

Organelle that synthesizes cholesterol and phospholipid, important in steroid production. Also important in detoxification and calcium storage

75 percent

percentage of the cell that is water

Fluid mosaic model

idea that proteins within the membrane can move around within it (fluid), and that there are many different kind of structures within the membrane (proteins, carbohydrates, cholesterol, etc)

cholesterol

provides stability, both mechanical and for temperature, to the membrane, found within the membrane

Hydrophilic, hydrophobic

The phosphate head is what, and the lipid is what, causing the creation of the lipid bilayer of the cell

membrane proteins

embedded within the membrane, can be

• integral

• peripheral

integral membrane proteins

extend through both sides of the membrane, may serve as channels for entry of substances into and out of the cell

peripheral membrane proteins

attached to only the surface of the membrane, often on the inner surface, and serve as enzymes or cell control mechanisms

membrane carbohydrates

maintain a negative charge, serve as receptors for ligands and often function in immunity

diffusion

movement across the cell membrane slowly due to concentration gradients, without the use of channels, small molecules

channels

membrane proteins that aren’t generally “active”, don’t burn cellular energy to transport molecules

pumps

membrane protein that burn cellular energy to transport molecules across the cell

vesicles

allow for bulk membrane movement/transport

function of the cell membrane

allows for control and intra- and extra- cellular environments, allows violation of equilibrium, storage, and protection

saturated fats

fats that are completely saturated with H, single bonds, solidify at room temperature

unsaturated fats

fats that are not completely saturated with H, contain double bonds, may be liquid at room temperate— membrane are made of this

lipid rafts

control the location of embedded elements in the fluid mosaic model, allows for organization of the fluid mosaic model, random alignment wouldn’t be productive

membrane curvature

the composition of the membrane is different on the outside and inside, causes a curve in the membrane

endocytosis

occasionally requires specialized receptors, this process includes invagination, formation of a pouch, and formation of the vesicle (inside of the cell)

exocytosis

may require specialized receptors, process includes a vesicle joining with the cell membrane, then the secretion of the cellular product out of the cell

ectosome

cell pinches off a piece of the membrane, may be useful when there is damage to the cell membrane

exosome

when multiple vesicles from exocytosis merge together they form this. aka multivesicular body

cytoskeleton

provides structural support, organization and mobility for the organelles and various enzymes

microfilaments

actin and myosin are examples, involved in contraction, cell division, and structural support

intermediate filaments

desmin, vimentin, keratin, and laminin are examples, involved in structural support, “anchor” for contraction, directed growth (eg axons)

microtubules

tubulin family, involved in structural support (compression) cell division (chromosomes), and movement and transport (believed transport of O2 and metabolic intermediates), promotes communication among organelles

lysosomes

contain digestive enzymes for “food”, threats, autophagy

autophagy

digestion of worn-out organelles so that they can be continuously replaced, may decrease with age and be mitigated by exercise

apoptosis

planned cell death

lysosome

disruption of this organelle releases its digestive enzymes into the cytoplasm, killing the cell

peroxisome

organelle responsible for the control of free radicals, which would otherwise be harmful to the cell since they are reactive chemical compounds, also involved in fatty acid breakdown (especially VLCFAs)

liver

where the peroxisomes are particularly abundant and large

mitochondria

number and size of this organelle varies depending on the function of the cell, very permeable outer membrane, principal energy compound production sites (ATP formation)

cristae

folds in the inner membrane of the mitochondria that function to increase surface area

electron transport chain

mechanism by which ATP is generated in the mitochondria but also a major course of formation of O2 free radicals

self-replicating

the mitochondria has this type of replication due to its separate, secondary (maternal) genome

TCA cycle

also known as the citric acid cycle, or the Krebs, processes products from glycolysis, amino acid metabolism. and fatty acid metabolism to produce GTP and products that go on to feed the ETS

endoplasmic reticulum

system of membrane, may be rough or smooth

rough ER

is studded with ribosomes, houses the proteins created by the ribosomes to be secreted by the cell by removing specifc amino acids (keeps it from entering the cytoplasm)

ribosomes

found in cytoplasm or RER, site of translation (creating of proteins from RNA code), 2 subunits mostly made of RNA

translation

ribosomes use tRNA to build a protein from amino acids based on the mRNA code

Golgi complex

separates and packages proteins for secretion, continuous with the RER- ie protein modification. Proteins are differentiated and separated according to function and destination then shipped off

nucleus

most cells only have one (skeletal is multi- and erythrocytes have none), site of transcription, contains chromatin/DNA/RNA

transcription

copy DNA into mRNA

nuclear envelope

double membrane of the nucleus, outer membrane is continuous with the RER and inner membrane is supported by the nuclear lamina

biological principle

form follows function, cells will specialize with maturation and this is through the genome and functional demands

erythrocytes

red blood cells, carry gas and O2, CO2, nothing extraneous, no mitochondria, no nucleus

adipocyte

fat cell, stores energy

myocyte

muscle cell, generates force and movement, 60% protein content is contractile (actin and myosin), can have different types

type I muscle fibers

aka slow-oxidative, used for sustained low force activity, many mitochondria, less contractile proteins

type II muscle fibers

aka fast glycolytic, used for high force, short term activities

adaptation

cellular change that is due to long term exposures to stimuli

normal adaptation

result of change in living conditions

therapeutic adaptation

changes as a result of treatment

pathological adaptation

adaptation as a result of damaging conditions, can be acute or chronic

ectoderm, myoderm

epithelial tissue is derived from these

avascular

epithelial cells often are this way, they do not contain vessels or any circulation system

structure of epithelial cells

contiguous sheets covering surfaces (internal or external), occasionally are sensory cells (taste buds, olfactory buds), and glands

endothelium, mesothelium

other terms for epithelial

squamous cells

characterized by flat epithelial cells

cuboidal cells

cube shaped epithelial cells

columnar cells

longer, column shaped cells

simple

cellular type of epithelia that is characterized by a single layer of epithelial cells (squamous, cuboidal, or columnar) and a basement membrane

pseudostratified

cellular type of epithelia that is characterized by a singe layer of epithelial cells in which some of the cells do not reach the top of the layer, giving the impression of multiple layers of cells

stratified

cellular type of epithelia that is charaterized by more than one cell layer

transitional

a more artifactual term, is eventually a stratified cellular type but has the ability to stretch and distend (many found in the bladder/urinary tract)

keratinized

the outer layer of an epithelial membrane may develop into this hard and jagged exterior

basement membrane

different than the phospholipid bilayer, is an acellular protein with a GAG-rich structure, secreted by the epithelium and is usually at the interface with connective tissue

functions of the basement membrane

anchoring and some filtration, important in active interaction between cells

polarity

this property of epithelial cells (most pronounced in columnar cells) allows for different adaptations and functions at either end of the cell (causes apical vs basolateral domains)

epithelial functions

barrier- acts as protection, separation of compartments, regulation of interactions, as well as absorption, and secretion

features of squamous cells

typically for covering, barrier functions, have minimal cytoplasm and few organelles, some may be secretory (ie serous epithelium), may have less pronounces polarity

features of cuboidal/columnar cells

typically more involved in absorption and secretion, more extensive cytoplasm and organelles, more pronounced polarity, more variable morphology (microvilli and cilia)

absorption

function of microvilli in epithelial cells in the intestine

movement of air/O2 along surface

function of the cilia in the bronchiole epithelial section

endothelial structures that perform secretion

mesothelium, endothelium, glands

examples of mesothelium

ex: pleural and peritoneal cavities, secrete limit quantities

examples of endothelium

vasculature, prostacyclin stops platelets from sticking together, Nitric oxide

examples of glands

endocrine (have no ducts), exocrine (has ducts, pancreas is an example), unicellular (goblet cells)

cell connections

epithelial membranes are involved in creating these, some examples are tight junctions, adherent junctions, desmosomes, and gap junctions

adherent junctions

stronger, good at keeping cells connected, not as occlusive

tight junctions

provides a seal between cells, not as strong as AJs, more occlusive

zonular

meaning circumferential, goes around the zone

desmosomes

junctions that stay in certain areas, are localized

True

Can glands (epithelial in nature) be found within other types of tissue?

sweat gland

example of epithelial tissue that burrows into skeletal/subcutaneous tissue

merocrine

type of secretion that occurs through exocytosis- secretory fluid is sent out in vesicles

apocrine

type of secretion that is classified by secretory cells accumulating material at their apical ends, often forming blebs or "snouts", and this material then buds off from the cells, forming extracellular vesicles.

holocrine

type of secretion that occurs when the entire secretory cell disintegrates, releasing all of its contents at once (cell destruction)

function of gap junctions

promote RAPID communication between cells

collect information regarding the health of the matrix

Why do cell junctions exist in connections to the basement membrane?

hemidesmosomes, focal adhesions

types of junctions found in connection to basement membranes

role of cell connections in tissue function

barrier functions, don’t allow things to slip through, directing transport of cargo, regulation of compartments

transcellular

transport through the cell

paracellular

transport through to different cells