midterm

histology

the study of cells and tissues, microanatomy

cellular shape

affects and determines function

intracellular fluid

fluid inside the cells, mostly comprised of cytoplasm, made up of 70% water

cytosol

fluid surrounding the organelles

extracellular fluid

fluid outside the cells

plasma membrane

a phospholipid bilayer that acts as a selective barrier for the cell

the structure of the plasma membrane is described as the…

fluid-mosaic model

a “mosaic” of membrane proteins are free to move in a sea of lipid

lipids

molecules composed predominantly (but not exclusively) of hydrogen and carbon atoms

extracellular matrix

complex structure of different proteins

primarily collagen, some polysaccharides (situated like a tree: collagen is trunk, polysaccharides are branches - called a glycoprotein)

area immediately surrounding the plasma membrane of a cell

lipids are (polar/nonpolar) and contain (covalent/ionic) bonds

nonpolar

covalent

lipids (polarity/nonpolarity) makes them (soluble/insoluble) in water

nonpolarity

insoluble

4 subclasses of lipids

fatty acids

triglycerides

phospholipids

steroids

3 main lipids in order of complexity from least to greatest:

fatty acid chain → triglyceride → phospholipid

triglyceride =

1 glycerol + 3 fatty acid chains

phospholipid =

1 glycerol + 2 fatty acid chains + a phosphate group

which part of a phospholipid is nonpolar? why?

the side with the fatty acid chains

C-H bonds are stable & don’t have any charges, lipids are insoluble in water

which part of a phospholipid is polar? why?

the side with the phosphate group

the phosphate group has unequal distributions of electrons, making it charged (polarized)

amphipathic

having both hydrophilic & hydrophobic parts

phospholipids are amphipathic

water is (polar/nonpolar). why?

polar

H molecules have a slight positive charge, whereas O molecules are slightly negative

when coming in contact with water, how do phospholipids organize themselves?

phosphate groups are attracted to the polar water molecules, and fatty acid chains are attracted to each other in an effort to get away from the polarity of water

cell membrane itself (does/does not) let water through

does not

how does water enter the cell?

carried through by proteins in plasma membrane

transmembrane proteins

extend to both sides of plasma membrane (has polar ends & a nonpolar middle)

integral proteins

half in, half out of membrane (has a nonpolar end & a polar end)

peripheral protein

only on one side of the membrane, either intracellular or extracellular (polar)

role of cholesterol in the cell membrane

stabilization, structure, fluidity

see slide 15 for epithelial cells controlling molecule transport

specialized junctions (part of ECM) allow cells to (form layers/separate themselves)

form layers

specialized junctions determine…

…permeability

desmosome

a specialized junction that is composed of cadherins (doesn’t seal up opening, just a protein maze, loose connective tissue)

cadherins

proteins that extend from the cell into the extracellular space, where they link up and bind with cadherins from an adjacent cell)

tight junction

a specialized junction that involves physical binding of 2 cells (no opening, nutrients have to pass through cells to enter/exit structures on either side)

gap junction

a specialized junction that creates an bridge-like opening between 2 cells (molecule flow based on concentration gradient, primarily in cardiac muscle)

cytology

study of the structure & function of a cell

cytoskeleton

a network of filaments & tubules that maintains cell shape, helps locate organelles within cytoplasm, & guides or directs cytoplasmic transport

mitochondria

ATP production

powerhouse of the cell

uses O2 & produces CO2

has its own DNA & ability to replicate itself

present in all cell types EXCEPT RBCs (more numerous in cells that utilize large amounts of energy ex: striated muscle cells)

smooth endoplasmic reticulum (SER)

a series of tubules that have no ribosomes on their walls (so they appear smooth)

involved in lipid synthesis & metabolism

involved in synthesis & secretion of steroid hormones

involved in MEMBRANE FORMATION & RECYCLING

hepatic (liver) form: detoxifies, processes some drugs

sarcoplasmic reticulum

specialized SER found in skeletal & cardiac muscle cells (regulate Ca+2)

rough endoplasmic reticulum (RER)

series of interconnected chambers with walls covered in ribosomes (so they appear rough)

essential for PROTEIN SYNTHESIS

HIGHLY DEVELOPED IN PROTEIN SYNTHETIC CELLS LIKE FIBROBLASTS

ribosomes

protein factories of a cell

take in amino acids & synthesize proteins

golgi complex

looks like a stack of pancakes

well developed in secretory cells

intermediary between ER & the cell (processes newly formed proteins; concentrates, packages & marks proteins for intra- or extra-cellular use)

PROTEIN PACKAGING PLANT

what functions can the golgi complex give to different proteins?

some become lysosomes

some strengthen the cell membrane

some get secreted

how are samples of human tissue collected?

biopsy

biopsy

cutting away a small piece of tissue or blood for analysis

biopsy techniques

mostly involves a needle, sometimes a scalpel (if patient is already in surgery)

organ may require “going in blind” (there are some visualization tools that can be used as guides)

2 types of tissue sample preservation

freezing & chemical (fixative)

why would you choose to freeze samples instead of fixating them with chemicals?

when thawed, proteins (enzymes) can continue activity

what does freezing preservation entail?

use of liquid nitrogen (-170 C)

sometimes another bottle of liquid is placed into the liquid nitrogen to contain the sample (“snap freezing”)

__% of samples are frozen

10

__% of samples are chemically fixed

90

what does chemical fixation entail?

use of formalin, formaldehyde, glutaraldehyde

permanently cross-links amino acids & other biological molecules (creates covalent bonds that aren’t there naturally, locks in protein conformation)

sample placed in something like an alcohol solution afterwards to prevent bacteria

tissue sample preparation:

samples are left in fixative for _________

samples must be (hydrated/dehydrated) - can be stored in ________ solution at this point

then ____________ for cutting

samples will ____________ at room temp

frozen samples must be kept at ___C

at least a few hours (can be longer)

dehydrated - ethanol

embedded in wax

remain stable

\-80

what instrument is used for cutting tissue samples?

microtome

what instrument is used for cutting frozen tissue samples?

cryostat

microtome

slices 5-20um sections to be placed on slide (thinner than a piece of hair)

what has to happen to cut tissue samples before stain is added?

paraffin (wax) has to be dissolved

most common stain for tissue samples =

Hematoxylin & Eosin (H&E) - red/pink color

what other stains are there?

specific stains - stain for specific structures within the tissue

what is immunohistochemistry?

antibody (Ab) binds to an antigen

something (ex: a 2nd Ab) recognizes that Ab - creates signal amplification, makes structures more visible

fluorescence can be used to visualize structures at this point

what are the different types of microscopy used for tissue samples?

light (bright field) microscopy

fluorescent microscopy

electron microscopy

fluorescent microscopy

only structures selected by stains are visible

electron microscopy

detailed, minute, can see structures that make up whatever is stained

what must be done to diagnose/interpret results?

careful quantification & statistical analysis, since data is collected blindly

epithelial tissue:

typically (very/not) cellular & (vascular/avascular)

arranged in (layers/clumps)

lines (all/some) cavities & other openings

very

avascular

layers

all

mesothelium

lines body cavities

endothelium

lines blood vessels

epithelial gland types

endocrine & exocrine

functions of epithelial tissue

protection, absorption, secretion, selective barrier

structure of epithelial cell barriers

underlying tissue → basal lamina (blood side) → epithelial layer → apical surface (lumen side)

what 3 things determine epithelial cell naming?

# of cell layers

shape of cells in the OUTERMOST layer

cell “accessories” in the outermost layer

1 layer of epithelial cells =

simple epithelium

> 1 layer of epithelial cells =

stratified epithelium

pseudostratified columnar

columnar cells permeate bottom layer, jumbled appearance

squamous cells

flat, plate-like

cuboidal cells

cube-shaped

columnar cells

tall

cell “accessories”

cilia

goblet cells (secrete mucus, particularly in digestive organs)

microvilli (extensions of cytoplasm that increase surface area, particularly in absorbent cells)

glycocalyx (extracellular carbs or lipids in ECM bind to membrane proteins)

why are cellular junctions important for epithelial tissue?

form sheets

determine function

promote communication

tight junction:

(permeable/selectively permeable/impermeable)

holds _____ together

forms between (transmembrane/intercellular) proteins

allows each side of the epithelial tissue to have (the same/completely different) functions

prevents migration of ________ ________

impermeable

cells

transmembrane

completely different

membrane proteins

desmosome:

_________ junction

holds _____ together

(permeable/selectively permeable/impermeable)

forms between (transmembrane/intercellular) proteins

anchoring

cells

selectively permeable

transmembrane

gap junction:

_____________ junction

(permeable/selectively permeable/impermeable)

communicating

permeable (between certain cells)

simple diffusion

molecules able to cross membrane without assistance

limited based on chemistry of substance & cell membrane

exocytosis

intracellular vesicles fuse w/ cell membrane & release contents into extracellular fluid

endocytosis

extracellular molecules are consumed by cell & enter the cytosol in vesicles

protein-mediated transport types

facilitated diffusion (glucose)

primary active transport (3 Na out, 2 K in) - ATP

secondary active transport (Na in, another molecule in against concentration gradient)

what are the big parts of the integumentary system?

skin

hair

nails

sweat glands

skin:

(waterproof/water permeable)

(self-repairing/unable to repair)

(smallest/largest) organ in the body

waterproof

self-repairing

largest

what are the layers of the skin?

epidermis (outermost)

dermis (middle)

hypodermis (deep layer)

skin functions

prevent dehydration & associated electrolyte imbalance

thermal regulation

barrier to mechanical & chemical trauma

barrier to micro-organisms

barrier to UV & other types of radiation

skin:

(sensory/motor) receptor

synthesizes vitamin (C3/D3) - required for (Ca/K) absorption in the gut

sensory

D3

Ca

what substances does the skin secrete?

urea, salts, H2O

what kind of tissue is the EPIDERMIS composed of?

epithelial

epidermis: “_________” layer

cornified (hard)

what kind of tissue is the DERMIS composed of?

connective

which layer of the skin is not a true skin layer?

hypodermis

what kind of tissue is the HYPODERMIS composed of?

subcutaneous connective tissue (loose)

superficial fascia lata (adipose)

The epidermis can be described as stratified squamous keratinized epithelium.

true

false

true

the epidermis generally consists of (one/multiple) distinct layer(s) of cells

multiple

thick skin

5 layers

<5 mm

soles of feet

thin skin

4 layers

<1 mm

dorsum of head, eyelids