Introduction to histology Flashcards
what is histology
study of microscopic structure of normal tissues
understand how tissues are built to carry out their functions
knowledge of normal histology is essential in histopathological diagnosis of disease, guides treatment
light microscopy
most common way to study cells
tissues are mounted on glass slides as thin preparations, stained with appropriate dyes, illuminated by light and viewed using glass lenses
electron microscopy
uses parallel beam of electrons instead of light waves, increases resolution
the beams of electrons have shorter wavelengths so have greater magnification than light microscopes
use transmission and scanning
label the light microscope
image in the eye
ocular lens
objective lens
specimen
condenser lens
mirror
lamp
tissue preparation for light microscope
fixation- preserve a tissue using formalin (LM) or glutaraldehyde (EM)
dehydration- remove water using alcohol
clearing- remove the alcohol
embed in a suitable medium- paraffin
section into thin slices
mount onto the glass slides (easy handling)
stain with various dyes to see the structures
apply coverslip over section
stains for electron microscopes
salts of heavy metals
lead citrate or uranyl acetate
areas that bind to the metals are electron dense
areas where the metals don’t bind are electron Lucent
which parts of chromatin are heavy and light staining
heterochromatin is dense and euchromatin is light
what is the most commonly used stain
H&E
hematoxylin and eosin
hematoxylin
is a base
binds to acidic components of the cell, DNA
stains blue
these components are referred to as basophilic
eosin
is an acid
binds to cytoplasmic constituents of the cell that have a basic pH
stains pink
these components are referred to as acidophilic
Masson’s trichrome
stains nuclei dark blue
stains muscle and cytoplasm red
combination of 3 dyes and reveals the presence of collagen
third stain is normally nuclear counterstain like hematoxylin
Verhoeff’s van Gieson
elastic stain
stains black or brown
what do the 4 tissue types develop from
3 embryonic layers of tissue
ectoderm
endoderm
mesoderm
what are the 4 tissue types
epithelial
muscular
nervous
connective
epithelial tissue overview
derived from ectoderm
covers surfaces, lines body cavities and forms solid glands such as salivary glands
muscular tissue overview
derived from mesoderm
possess contractile properties
nervous tissue overview
derived from ectoderm
connective tissue overview
derived from mesoderm
cartilage, bone
ectoderm
related to skin
endoderm
associated with the gut/lungs
mesoderm
vascular
urinary
functions of epithelial tissue
protection- of underlying tissues of the body from abrasion and injury
transcellular transport- of molecules across epithelial sheets
secretion- of mucus, hormones, enzymes from various glands
absorption- of material from a lumen (epithelia which cover and line surfaces)
selective permeability- control of movement of materials between body compartments
detection of sensations
functions of epithelial tissue
protection- of underlying tissues of the body from abrasion and injury
transcellular transport- of molecules across epithelial sheets
secretion- of mucus, hormones, enzymes from various glands
absorption- of material from a lumen (epithelia which cover and line surfaces)
selective permeability- control of movement of materials between body compartments
detection of sensations
sensory epithelium
neuroepithelium
contractile epithelium
myoepithelial cells
epithelium being avascular
adjacent supporting connective tissue through its capillary beds supplied nourishment and oxygen via diffusion through the basement membrane
two classifications of epithelia
simple: single layer of cells
stratified: composed of two or more layers
how are epithelia separated from underlying connective tissue
by a thin acellular layer called the basement membrane
provides support and attachment for epithelial cells and acts as a selective diffusion barrier
composed of basal lamina and reticular lamina
basal lamina is secreted by the epithelial cells and consists of the lamina lucid and lamina densa
types of simple epithelia
squamous (flat)
cuboidal
columnar (with or without cilia)
what type of epithelia is this
stratified cuboidal
usually confined to the lining of the larger excretory ducts of exocrine glands such as the salivary glands
what type of epithelia is this
stratified squamous non keratinised
cuboidal basal layer to flattened surface layer, basal cells adherent to the underlying basement membrane include continuously dividing stem cells, offspring shed as enucleate squames
what type of epithelia is this
transitional epithelium/urothelium
multilayered with cuboidal/polyhedral basal and middle layers and has a unique surface layer
domed and almost columnar when the bladder is undistended
squamous and more flattened when the bladder is distended
found in the urinary tract and bladder
what type of epithelia is this
pseudo stratified columnar ciliated epithelium
has cilia on the apical surface of the cells that reach the epithelial surface
found in the lining of most of the trachea and primary bronchi, auditory tube, part of the tympanic cavity, the nasal cavity
what’s the difference between the two epithelia
left is nonkeratinised and right is keratinised
both stratified squamous epithelia
both separated from the connective tissue by the basement membrane
kerinised provides added protection from frictional forces
example and function of simple squamous
peritoneum
vascular endothelium
facilitates the movement of the viscera (mesothelium), active transport by pinocytosis (mesothelium and endothelium), secretion of biologically active molecules
example and function of simple cuboidal
collecting tube of the kidney
covering, secretion
example of simple cuboidal with microvilli
proximal convoluted tubule of the kidney
example and function of simple columnar
gallbladder
protection, lubrication, absorption and secretion
example of simple columnar with microvilli
small intestine
example of simple columnar with surface cilia
Fallopian tube
example of simple columnar with pseudo stratification
respiratory tract
protection, secretion: cilia-mediated transport of particles trapped in mucus out of the air passages
example of simple columnar with goblet cells
small and large bowel
example of simple columnar with stereo cilia
vas deferens
example of stratified squamous
oral cavity
protection, secretion, prevents water loss
example of keratinised stratified squamous
epidermis of the skin
protection, prevents water loss
example of stratified cuboidal
exocrine gland ducts
protection, secretion
example of stratified transitional
bladder
protection, distensibility
junctional complexes are composed of three types, what are they?
zonula occludens
zonula adherent
desmosomes (macula adherens)
zonula occludens
control paracellular diffusion and prevent exchange of intrinsic proteins
impermeable barrier
tight junction
zonula adherens and desmosomes
junction
deep to tight junctions
links cellist form cohesive epithelium/cell to cell adherence
gap junctions
present on lateral cell membrane allow intercellular signalling and exchange of ions
provide metabolic and electrical continuity via pores between cells
hemidesmosomes
anchor the basal layer of cells to basal lamina
label the cell
microvilli
tight junction
adherens junction
desmosome
intermediate filament
gap junction
hemidesmosome
basal lamina
