Histology and Cytology Flashcards
What is histology?
microscopic division of Anatomy
the study of the TISSUEs of the body
-now used to encompass cytology and organology as well
What is cytology?
study of the cells of the body
What are the four types of tissue studied in histology?
epithelial tissue (epithelium)
muscle tissue
connective tissue
nervous tissue
define a tissue
group of similar cells with common function, also ECM
list the levels of structural organization
chemical > cellular > tissue > organ > organ system > organismal
epithelial tissue
covers body surfaces, lines hollow organs, body cavities and ducts and glands
connective tissue
diverse, protect and support body
muscle tissue
contractile, makes force
nervous tissue
detect stimuli and generate action potentials and nerve impulses
Light Microscopy
Specimens examined via transillumination (i.e., passing light through the specimen to facilitate observation)
Steps: 1. Acquisition of Cells or Tissues 2. Fixation 3. Processing Dehydration – using a graded series of alcohol Clearing – using a miscible substance Infiltration – using a liquid embedding medium 4. Embedding 5. Sectioning 6. Staining
-pink images
takes a lot of time, can lose components
or get contaminants in slide prep, has to be incredibly thin (7-10 micrometers)
fixative: stop metabolism and bacteria/viruses/fungi, harden tissue (12 hours in fixative)
Electron Microscopy
Provides:
Greater Resolution
Higher Magnification
Two Types:
Transmission Electron Microscopy (TEM)
Scanning Electron Microscopy (SEM)
Transmission Electron Microscopy (TEM)
uses a beam of electrons that passes through the specimen
higher magnification
greater resolution
black and white on images
Scanning Electron Microscopy (SEM)
beam of electrons scans the surface of the specimen
Atomic Force Microscopy
AFM
How is resolving power (resolution) defined? How does it compare between the three microscope types and the human eye?
Defined as how far two objects must be separated from one another so that they can be distinguished as two distinct objects:
Human Eye – 0.2 mm Light Microscope – 0.2 μm SEM – 2.5 nm TEM – 0.05 nm (theoretical) / 1.0 nm (tissue section) Atomic Force Microscopy – 50.0 pm
What 5 factors is resolution dependent on?
- Optical System
- Wavelength of Light Source
- Specimen Thickness
- Quality of fixation
- Staining Intensity
What does fixative do?
stop metabolism and bacteria/viruses/fungi, harden tissue (12 hours in fixative)
for light microscopy
Processing
Dehydration
using a graded series of alcohol
Clearing
using a miscible substance
Infiltration
using a liquid embedding medium
What are the common problems with the typical histological technique used to prepare tissues to be observed with a light microscopic examination (i.e. with paraffin)?
- Time - takes awhile (days)
* Use of Cryostat (tissue into liquid N, back in few min.) - Solvent Dissolves Lipids (interested in them often, don’t want to lose)
* Double Fixation – First fixation with glutaraldehyde and a second fixation with osmium tetroxide
* great for preservation of membranes and TEM looks great - Shrinkage of Tissues
* Embedding in Resin
Acidic dyes
- carry a net negative charge; bind with cationic cell/tissue components (i.e. those that carry a net positive charge)
- ex. eosin (pink or red hue), orange G, and acid fuchsin
- stain acidophilic (or eosinophilic) tissues (i.e. those tissues with a high affinity for acid dyes; these tissues exhibit acidophilia)
- mitochondria, secretory granules, collagen fibers (as well as other extracellular fibers), general cytoplasm, basement membrane; staining with acidic dyes is less specific; more substances within cells and the extracellular matrix exhibit acidophilia than basophilia
Basic Dyes
- carry a net positive charge; bind with anionic cell/tissue components (i.e. those that carry a net negative charge)
- ex. toluidine blue, alcian, and methylene blue; hematoxylin(doesnt actually have neg charge or pos charge but acts like it does), although not a basic dye, acts like one
- stain basophilic tissue (i.e. those tissues with a high affinity for basic dyes; these tissues exhibit basophilia)
- these dyes will bind to the negative phosphate group on DNA and RNA (cell nucleus, nucleoli, RNA-rich portions of the cytoplasm); the carboxyl groups of proteins; sulfate groups of cartilage matrix (GAGs)
Hematoxylin
(+: no charge actually, but acts as if its basic): basophilic tissue, blue hue
stains: nuclei, DNA/RNA phosphate groups, protein carboxyl group, GAGs (sulfate group) in cartilage matrix
Eosin
(-): bind with cationic/ acidophilic/eosinophilic tissue, pink hue
stains: “EVERYTHING BUT THE NUCLEUS” mitochondria, secretory granules, collagen fibers, cytoplasm, basement membrane
-less specific
MORE substances in cells and ECM take to acidic dyes**
Histochemistry and Cytochemistry
“Don’t wanna use a lot of fixation with these, use cryostat so proteins are functional, enzymes working”
Steps:
1. Section immersed in solution of enzyme’s substrate
2. Enzyme acts on substrate
3. Section put in contact with a marker compound
4. Marker compound reacts w/ molecule produced by enzymatic action on substrate
5. Final product (insoluble and visible by light or electron microscopy) precipitates over site
artifact
dust, hair, particles that can be an issue when studying tissue sections
vesicular transport
exocytosis
endocytosis
The plasma membrane (plasmalemma) is composed of what? What is its function?
phospholipids, cholesterol, proteins, and chains of oligosaccharides
Site where materials are exchanged between the cell and its environment; regulates the ion concentration of the cytoplasm; also recognition, regulatory, and interaction functions.
Humans have approximately ____ different cell types
200
How thick is the plasma membrane?
7.5-10 nm in thickness, EM
Describe the structure of the plasma membrane
Trilaminar
EM: fluid mosaic model
Which process is responsible for the bulk uptake of material across plasma membrane and into the cell?
Endocytosis
Endocytosis
bulk uptake of material across plasma membrane into cell;
folding and fusion of membrane to form vesicles
Phagocytosis Pinocytosis (Fluid-Phase Endocytosis) Receptor-Mediated Endocytosis
Phagocytosis
“cell-eating”; phagosome; then fuses with lysosomes
Pinocytosis
Fluid-Phase Endocytosis
binding of the ligand to a receptor causes coated pits made of clathrin to form
- pinches off to form a coated vesicle
- fuses with endosomal compartment to form endosomes
Exocytosis
release of materials across plasma membrane into the EC space
-involves vesicle fusing with plasma membrane and releasing its contents
Describe the role of lysosomes as well as their structure
Function: intracellular digestion and turnover of cellular components
Size: 0.05-0.5 micrometers
Structure: membrane bound vesicles that contain about 40 different HYDROLYTIC ENZYMES
-abundant in neutrophils, macrophages
Ribosomes
Function: Protein synthesis
Size: 20nm x 30nm
Structure: Composed of two different-sized subunits; the subunits are composed of rRNA and proteins; can be found free within the cytoplasm or attached to membrane of the endoplasmic reticulum.
phosphate on rRNA makes them MORE BASOPHILIC
Rough ER
Network of intercommunicating channels and sacs of membranes which enclose a space called a cisterna.
Ribosomes on the cytosolic side of the membrane; produces proteins for secretion.
Smooth ER
Network of intercommunicating channels and sacs of membranes which enclose a space called a cisterna.
Regions of ER without ribosomes; cisternae are much more tubular; important in the production of phospholipids; abundant in cells that synthesize steroid hormones (i.e. steroid synthesis - aka in adrenal cortex
Golgi Apparatus
Golgi Complex
Function: Completes post-translational modifications, packages, and sorts proteins synthesized in the RER.
Structure: Composed of smooth membranous saccules
-has a cis (i.e., entry) face and a trans (i.e., exit) face.
Mitochondria
POWERHOUSE Function: Membrane-enclosed organelles with enzymes arrays specialized for aerobic respiration and production of adenosine triphosphate (ATP).
Size: 0.5μm-1.0μm in diameter and 5μm-10μm in length.
Structure: Two membranes (i.e., inner and outer) and two compartments (i.e., matrix and intermembrane space); inner membrane folded to form cristae which project into matrix.
EOSINOPHILIC
common in muscle, liver, kidney
stain pink with eosin
eosinophilic
Secretory Vesicles (Granules)
STORAGE
Function: Formed at the Golgi apparatus; store product until it is released via exocytosis.
Structure: Secretory product surrounded by membrane.
Proteasomes
Function: Degrade denatured and nonfunctional polypeptides.
Structure: Cytoplasmic protein (i.e. no membrane); cylindrical structure made of four stacked rings.
Peroxisomes
Function: Oxidizes various potentially toxic molecules as well as prescription drugs.
Size: 0.5μm in diameter
Structure: Spherical membrane-limited organelles.
liver, kidney
Microtubules
Fine tubular structures found in cytoplasmic matrix, centrioles, basal bodies, cilia, and flagella. Hollow lumen.
Function: Formation and maintenance of cell shape; cellular transport of organelles and vesicles; create repeated beating motion
Size: outer diameter of 24nm and a dense wall 5nm thick; hollow lumen
Length: variable; can be many μm in length
Structure: composed of α and β tubulin molecules; organize to form 13 parallel protofilaments
cilia, flagella: 9+2
microtubule pattern
In cilia and flagella, the same core structure is present – axoneme.
Assembly of microtubules in a 9+2 pattern.
Nine peripheral doublets have an outer arm of dynein which connects to next doublet; ATP-dependant interaction cause conformational changes – get repeated beating movement.
Microfilaments
Actin Filaments
Function: Allow for contractile activity within cells, including cell shape changes for endocytosis, exocytosis, and cell locomotion, moving cytoplasmic components, and cleavage during mitosis.
Size: 5-9nm
Structure: Composed of globular subunits organized into a double-stranded helix.
Intermediate Filaments
Very stable; provide mechanical strength and stability.
Size: 10-12nm in diameter
Structure: Protein subunits different in different cell types; rod-like subunit that organize into a cable-like structure.
Inclusions
Are NOT considered organelles
Cytoplasmic structures or deposits composed mainly of accumulated metabolites or other substances
- liquid droplets ( cells appear empty in staining cause of organic solvents in processing)
- glycogen granuels
- pigment deposits
Nucleus
Main Components:
1. Nuclear Envelope – two parallel unit membranes separated by a narrow space; at sites where inner and outer membranes of the nuclear envelope fuse, nuclear pore complexes form; where regulation of the transport between the nucleus and cytoplasm takes place.
- Chromatin – the chromosomal material in a largely uncoiled state.
Heterochromatin – course granules in EM and basophilic clumps in light microscopy.
Euchromatin – less coiled; fine granules in EM and lightly basophilic areas in light microscopy.
3.Nucleolus – spherical, highly basophilic structure present in nuclei of cells active in protein synthesis; lots of rRNA in this location.
euchromatin lightly basophilic sdoesnt stain well
Nucleus main components
- Nuclear Envelope
- Chromatin
Heterochromatin
Euchromatin - Nucleolus
Apoptosis
The process of cell suicide or programmed cell death; leads to the production of small membrane-enclosed apoptotic bodies which undergo phagocytosis by neighboring cells.
necrosis vs apoptosis
PROGRAMMED cell death = apoptosis
Autophagosome
lysosomes that get rid of nonfunctional cellular components
cisterna
space enclosed by ER
The basal lamina is observed in TEM by using what?
osmium tetroxide (silver)
