Histology
“study of tissues”
History of the Microscope
Robert Hooke- 1665
• Created the first
microscope
• Looked at cork tissue
• Coined the term cells
History of the Microscope
Anthony van Leeuwenhoek1673
• Created microscopes that
magnified 200X, brighter and
clearer
• First saw microscopic
organism in pond water
Microscope parts
Magnification
• 10X Ocular (eye piece)
• 4X
Scanning objective)
– Is used for initial location of the specimen
• 10X Low power objective
– May also be used for initial location of the specimen or for observing
specimens that don't need greater magnification
• 40X High-dry objective
– Is used for specimens requiring greater magnification
– Does not require the use of oil
• 100X Oil immersion objective
– Used for magnification of extremely small specimens
– Oil prevents refraction of light so images are less distorted
Calculating Magnification
Eye piece X Objective lens= Total magnification
10 X 40 = 400
10X
100X
oil
Functions
• Stage- used to set slide on
• Mechanical Stage- had adjustable
brackets that move stage around
• Condenser- between light source and
stage, concentrates light
• Diaphragm- controls amount of light
coming in and out
Functions
• Coarse adjustment knob- used first to
locate specimen
**never use in high-dry or oil immersion or you
will crack the slide
• Fine adjustment know- moves very little
used to focus in high powers
Resolution
• The resolution limit, or resolving power,
of a microscope lens is a function of its
numerical aperture, the wavelength of
light, and the design of the condenser.
• The maximum resolution of the best
microscopes is around .2µm. This
means that two small objects that are
0.2µm apart will be seen as separate
entities; objects closer than that will be
seen as a single object.
Resolution
Lens Care
• Dust, oil and other
contaminants on the lens
can reduce resolution.
• Only lint free tissues
should be used to clean
the lens
• If there is still
contaminants on the lens
you may use some mild
soap and water with lens
tissue to clean the lens
Oil Immersion
• Oil can be used to enhance the resolving
power of the microscope
• Locate the object in either low or high dry
magnification
• Rotate the oil immersion objective lens in
half-way position.
• Place a drop of immersion oil on the slide
and lower the lens
• Open the diaphragm as much as
possible, the manipulation of light is
critical
• Always clean the lens and slide before
returning the microscope to the cabinet.
Histology
• Tissue- a group of cells
that perform a similar
function
– Can be one cell thick or a
mass of millions of cells
• Matrix- non-living
intercellular material that
surrounds cells
– Some tissues are
surrounded entirely by
matrix others have very
little
• Desmosome and tight
junctions hold tissues
together
Germ Layers
• Zygote form in
hollow balls of cells
called a blastocyst
• Blastocyst
undergoes
gastrulation and the
layers begin to form
different tissues
Ectoderm
Epithelium(epidermis) of skin
Lining of mouth, anus, nostrils
Sweat glands and sebaceous
glands
Nervous system
Epithelial (sensory) parts of
eyes, nose, ear
Mesoderm
Muscles
Skelton (bones & cartilage)
Blood
Epithelial lining of blood
vessels
Dermis of skin Organs(except
lining) excretory & reproductive
Connective tissue
Endoderm
Epithelial (lining) of digestive
& respiratory systems
Secretory parts of liver &
pancreas
Urinary bladder
Epithelial lining of urethra
Thyroid, parathyroid, thymus
Types of Tissue
1.
2.
3.
4.
Epithelial
Connective
Muscle
Nervous
Functions of Epithelial Tissue
• Covers & protects
• Lines cavities
• Secretion & Glands
– Mucus
– Hormones
– Sweat
• Excretion
– Kidneys
• Absorption
– Lining of gut
– Lining or respiratory tract
General Characteristics of
Epithelial Tissue
• Limited intercellular space or matrix
• Continuous sheets packed tightly together
• Avascular, contains no blood vessels
– Nutrients move through diffusion
• Basement membrane adheres it to connective
tissue
– Integrins bind cytoskelton of cells to basement
membrane
• Because they go through so much wear and
tear they have a high mitotic rate
Classification of Epithelial Tissues
Simple Squamous Epithelial
• One layer, flat scale
like cells
• Substances can
diffuse/filter easily
– Examples
• Alveoli
• Blood vessels
• Pleural membranes
Simple Squamous Epithelial
Simple Cuboidal Epithelium
• One layer of cuboidal
cells resting on
basement membrane
– Examples
• Glands and ducts
• Ducts & tubules of
kidneys
Tubules in kidneys
Simple Columnar
Epithelium
•
•
•
Adapted for secretion
Examples
– Lines stomach
– Uterus & ovaries
– Eyes
Modifications
– Goblet cells
• Have vesicles filled with mucus
– Microvilli & Cilia
• Plasma membrane extends out
Pseudostratified
Columnar Epithelium
• All the cells touch the
basement membrane
• Irregular placement of
nuclei
• Not all reach the top
layer
• Lots of goblet cells and
cilia
• Examples
– Lining air passages
– Segment of male
urethra
Pseudostratified
Columnar Epithelium
Stratified Squamous
(Keratinized) Epithelium
• Multiple layers
• Flatted cells on
surface
• Dead keratinized
cells at surface
– Examples
• Skin, kertin provides
protection
Stratified Squamous
(Keratinized) Epithelium
Stratified Squamous
(Non-keratinized) Epithelium
•
•
•
•
Look for nuclei at superior border
Flattened cells at surface
Many layers
Surface is moist
– Examples
• Vagina
• Mouth
• esophagus
Stratified Squamous
(Non-keratinized) Epithelium
Stratified Cuboidal
Epithelium
• Two or more rows of
cuboidal cells
• Arranged randomly
– Examples
• Sweat gland ducts
• Pharynx
• epiglottis
Stratified Cuboidal
Epithelium
Stratified Columnar
Epithelium
• Only most superficial
cells are columnar in
appearance
• Protective epithelium
– Examples
• Male urethra
• Mucosa layer near
anus
Stratified Columnar
Epithelium
Stratified Transitional
Epithelium
• Found in areas
subject to stress and
tension
• Prevent tearing
• When stretched cell
change shape from
cuboidal to
squamous
– Examples
• Bladder
Glandular Epithelium
• Glandular secretions rely on
highly regulated cellular
activity that requires using
stored energy
•
Mulitcellular or unicellular(goblet
cell)
• Exocrine Glands -release
secretion into ducts
–
–
–
–
Salivary glands
Sebaceous glands
Sweat glands
lacrymal glands
• Endocrine Glands- ductless
glands that release
secretions(hormones) directly
into blood
– Pituitary gland
– Thyroid gland
– adrenal
Thyroid gland
Islet of Langerhans
Exocrine Glands
•
Apocrine glands
– Secretion collect in tip(apex) of gland
– Secretions are released when distended end
is pinched off
– Cell loses cytoplasm and is damaged
– Recovery is quick and cell continues to
release secretions
• Mammary glands
• Sweat glands
•
Holocrine glands
– Collect secretions inside the cell
– Rupture completely to release secretion
– Cell is destroyed
• Sebaceous glands
•
Merocrine glands
– Secretion is released directly through plasma
membrane
– No loss of cytoplasm or damage to cells
– Most common gland
• Salivary glands
• Sweat glands not associated with hair
Exocrine Glands
Apocrine gland
Holocrine gland
Merocrine gland