Lecture 1: Histology Introduction & Cells Flashcards
Epithelia
Cover and line surfaces; ex intestines
Connective tissue
Packing, support, connecting; usually below epithelium
Muscle
Contractility;
Nerve
Irritability, conduction
Prep for microscopy
Fixation, dehydration, embedding, trimming/sectioning, staining (all have affects on tissue appearance)
Fixation
small pieces of tissue are placed in solutions that preserve by cross-linking proteins and inactivating degradative enzymes
Dehydration
In alcohols, removes all water
Embedding
The paraffin-infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden
Plane sections
Longitudinal (splits halfway through the longest part of the tissue)
Cross - splits horizontally to get a view of through the middle of the tissue
Oblique - splits on an angle
Staining
Because most cells and extracellular material are colorless ; most dyes behave like acids or bases and form salt linkages with molecules in tissues
(Basic dyes: toluidine blue, methylene blue, hematoxylin*
Acid dyes: eosin**, fuchsin)
Cell components with net negative charge (an ionic) / Acidic molecules
Stain more readily with basic dyes and are termed basophillic
Stain blue !!!
Ex; nucleus
Cationic components like proteins with ionized amino acids ( basic)
Stain more readily with acidic dyes; stain red/pink
Acidophilic
Ex; protein in cytoplasm
Problems with the interpretation of tissue sections
Shrinkage because of fixation, dehydration, and embedding
Artificial spaces in tissue
Loss of molecules that were not retained after fixation or removed during dehydration (glycogen and lipids)
Wrinkles in tissues
Precipitate of stains
Electron microscopy
*Transmission electron microscopy= very high resolution
400,000 times magnification
Dark areas in a TEM are called electron dense; light areas are electron lucent
Beam of electrons
*Scanning electron microscopy
Uses electron beam to scan
The cell
Surrounded by plasma membrane
Divided into cytoplasm and nucleus
Contain organelles
Nucleus
Membrane limited compartment that contains genome
site of transcription; site of chromosomes
Outer membrane has ribosomes and is continuous with RER at certain sites
Inner membrane faces nuclear material
**mature RBC + platelets don’t have
Nuclear envelope and pores
Molecules > 9nm = active transport mediated by receptors
Ions & smaller water soluble materials <9nm = simple diffusion through pores
Heterochromatin
Closed chromatin, cannot be read for replication
Highly condensed, no active transcription
Dense staining
Euchromatin
Open chromatin, ready to be replicated
Active **
Light staining
Nucleoulus
Spherical, basophilic
Site of RNA (rRNA) synthesis and initial ribosome assembly
Cytoplasm
Organelles & cytosol (intracellular fluid; dissolved nutrients, ions, soluble)
Ribosomes
Small, dark staining granules in EM
Ribosomes read mRNA and translates to amino acids
**translation = rRNA— protein
Endoplasmic reticulum
Anatomosing network of interconnecting channels and sacs/cisternae formed by continuous membrane
Rough ER = ribosomes
Smooth ER= no ribosomes
Polyribosomes
Ribosomes associated with mRNA
Occur in cytosol or on RER membranes
Rough er functions
Protein synthesis of secretory proteins (albumin, hormones, milk proteins, receptors, antibodies, collagen, enzymes, lipoproteins)
and neurotransmitters
N linked
Smooth ER
Synthesis & breakdown of glycogen
Detoxification of drugs, metabolic wastes, etc
Synthesis of lipoproteins, cholesterol, bile salts
Uptake and release of calcium in muscle cells
synthesis of lipids and steroid hormones
Golgi complex
Sack of membrane-bound disc shaped envelopes
Post translational modifications for proteins
O-linked glycosylation of proteins
Synthesis of lipoproteins
synthesis of glycolipids and sphingomyelins
different compartments serve different purposes
O linked glycosylation of proteins
Glycan is attached to an oxygen molecule on an amino acid
Added sugars used as recognition signals
N linked glycosylation of proteins
In the rough ER
Glycan I attached to a nitrogen molecule of an amino acid
More common than o linked
Mitochondria
Energy - transform chemical energy into high energy phosphate bonds in ATP
Beta oxidation of long chain fatty acids (in matrix)
regulates cell apoptosis
outer membrane = loosely packed
inner membrane = tightly packed
**liver, skeletal muscle, cardiac = thousands of mito
Lysosomes
Membrane-bound organelles contain hydrolytic enzymes
Acidic content (pH 4.5 - 5.5)
Electron dense heterogenous contents
**Digest ingested material an aged or damaged organelles, breakdown of bone
electron dense heterogenous contents
** in staining - secondary lysosomes are fused with waste (dark stain with light stuff in middle)
Peroxisomes/microbodies
Membrane bound organelles containing oxidative enzymes
*lipid metabolism ( beta oxidation of long chain fatty acids)
degrade hydrogen peroxide
Synthesize cholesterol, plasmalogens
zellweger’s cerebrohepatorenal syndrome
Fatal disease due to absence of peroxisomal enzymes
Reduced degradation of cytotoxic hydrogen peroxide and abnormal accumulation of very long chain fatty acids
cytoskeleton
Unique to eukaryotic cells
3d structure that fills cytoplasm
Long fibers are polymers of subunits
microfilaments, microtubules, intermediate filaments
Plasma membrane
Lipid bilayer
Consists of phospholipids, cholesterol, and proteins with oligosaccharaide chains covalently linked to many of the phospholipids and proteins
**physical barrier, selective permeability, communication (receptors), electrochemical gradients
Secretory granules
Serve as storage pool for selected secretory products
Seen in mast cells, pancreatic acinar cells, etc
**much larger than lysosomes
Lipid/ fat droplets
Abundant in some cells
Serve as an energy store and source of lipids which may be used in steroid hormone production
not enclosed by membrane
Glycogen
Highly branched polymer used as storage material for glucose
Liver and striated muscle cells usually contain large amounts of
Trimming/sectioning
Paraffin block is trimmed to expose tissue for sectioning by microtome
Trichrome staining
Connective tissue also stained
H & E staining
Cells with fats or mucus don’t stain because they get washed out with alcohol prep
Sudan black staining
Lipids get stained black; good for fat & myelin
PAS staining
Good for mucus, microvilli, glycogen granulose, basement membrane
TEM
Electrons through - shows inside of cell
400,000 x magnification - only looking small portions of cell
Dark= electron dense
Light= electron lucent
SEM
Surface of cell
Perinuclear space
Space between nuclear membrane
Outer nuclear membrane
Bears ribosomes, connected to RER in certain spots
Inner nuclear membrane
Stabilizes nucleus
Where chromosomes attach
Nuclear lamina
Web of intermediate filaments that support inner membrane
Nuclear lamina
Web of intermediate filaments that support inner membrane
Nucleosome
DNA wrapped around histone proteins ; basic repeating subunit of chromatin in nucleus
pregnenolon
made in mito, sent to SER; precursor to all c18, C19, C21 steroids (progesterone, aldosterone, testosterone, etc)
uptake, storage, & release of calcium involves…
mito and ER
microfilaments
actin, 7nm
intermediate filaments
proteins, 10nm
microtubules
tubular, 25nm
COP
costumer proteins, tag vesicles to guide to the correct place in cells (COP1, COPII, clathrin)
carbohydrates in plasma membrane
attach to proteins = glycoproteins
forms the cell coat(sugar coat/ glycocalyx)
establishes extracellular microenvironment
aids in metabolism, cell recognition, celll association, receptor sites for hormones
glycoproteins
glycan (sugar trees) attach to proteins
glycolipids
glycan + lipid
glycolipids
glycan + lipid
citric acid cycle & oxidative phosphorylation happen ..
in mito
glycolysis happens ..
in cytosol ;
mannose-6-phosphate
attaches to proteins, signal to be removed from cell via lysosome
Lysosome storage diseases
Results in accumulation of substrates for lysosomal digestion
