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Histology terms & principles
1. Know the basic histology terms and their meanings. (including the common
suffixes and prefixes, used in histology)
COMMON PREFIXES:
TISSUE:
 CHONDRO – Cartilage
 HEPATO – Liver
 Myo – Muscle
 OSTEO – Bone
 PNEUMO – Lung
LOCATION:
 EPI – upon/after
 ENDO – Inner
 INTER – between
 INTRA – within
 JUXTA – beside
 KARY – nucleus
 PERI – around
COMMON SUFFIXES:
 -BLAST = Actively dividing cell
 -CLAST = Break
 -CYTE = Resting cell
 -OID = Form
 -PHAGE = Eat
 -SOME = Body
COMMON TERMS:
 ADVENTITIA – Vessel or organ covering
 AFFERENT – To
 EFFERENT - From
 CAPSULE – Organ covering
 CORTEX – Outermost layer
 HILUS/HILUM – Pit or depression where vessels and nerves enter
 MEDULLA – Middle
 MUCOSA – Mucous membrane
 SEROSA – Support tissue – lines internal cavities
 SEPTUM – Division
 STROMA – Support tissue
2. Know the types of epithelial tissues and examples of where they are located.
HISTOLOGY – The microscopic study of tissues
EPITHELIUM – The protective covering of surfaces both inside and outside the body
Characteristics common to most types of epithelium:
1. Epithelium consists almost entirely of cells with very little extracellular
material between them
2. Epithelium covers surfaces of the body and forms glands that are derived
developmentally from body surfaces. These body surfaces include the
outside surface of the body, digestive tract lining, the vessels and linings of
many body cavities
3. Most epithelial tissues have
o one FREE/APICAL surface not attached to other epithelial cells
o a LATERAL SURFACE attached to other epithelial cells
o a BASAL SURFACE. This is attached to the BASEMENT MEMBRANE
o BASEMENT MEMBRANE – A specialised type of extracellular material
that is secreted by epithelial cells and connective tissue cells. It helps
attach the epithelial cells to the underlying tissues and plays an
important role during tissue repair
4. Specialised cell contacts such as tight junctions and desmosomes, bind
adjacent epithelial cells together
5. Blood vessels do not penetrate the basement membrane to reach the
epithelium. Therefore all gases and nutrients in the blood reach the
epithelium by diffusing across the basement membrane from blood vessels
in the underlying connective tissue
6. Epithelial cells retain the ability to undergo mitosis and therefore are able to
replace damaged cells with epithelial cells. Undifferentiated cells (stem cells)
continuously divide and produce new cells. In the skin and the digestive
tract, cells that are lost or die are continuously replace with new cells
Functions of the epithelia:
 Protecting underlying structures – e.g. skin and epithelium of oral cavity
 Acting as barriers – prevents movement of many substances through the
epithelial layer. E.g skin acts as barrier to water and toxic molecules and
prevents water loss from the body
 Permitting the passage of substances – Allows movement of many
substances through the epithelial layer. E.g. O2 and CO2 are exchanged
between the air and blood through the epithelium in the lungs
 Secreting substances – E.g sweat glands, mucous glands and enzyme
secreting portion of the pancreas
 Absorbing substances – The cell membrane of certain epithelial tissues
contain carrier molecules that regulate absorption of material
Classification of Epithelium:
Epithelium is classified primarily according to the number or cell layers and the
shape of superficial cells.
Based on number of cell layers:
 SIMPLE – 1 layer of cells, each one extending from the basement membrane
to the free surface
 STRATIFIED – >1 one layer of cells, only one is attached to the basement
membrane
 PSUEDOSTRATIFIED COLUMNAR – Appears to be stratified but isn’t. Has 1
layer of cells and ALL are attached to the basement membrane. There
appears to be more than one layer of cells bc the cells are tall and reach the
free surface. This type of epithelium lines the nasal cavity, trachea and
bronchi. They secrete mucus, covering the surface and have cilia on the free
surface which moves mucus and debris that accumulates over the surface of
the respiratory passages towards the exterior of the body
3 types of epithelium based on the shape:
 SQUAMOUS – Cells are flat and scale like
 CUBOIDAL – Cells are cube shaped; as wide as they are tall
 COLUMNAR – Cells are taller than they are wide
Most epithelium are given two names e.g. simple squamous.
First one = No. Of layers
Second one = Shape of the cells
SQUAMOUS:
 Simple – Mesothelium and endothelium

Stratified – Keratinized epithelium: skin
Non-keratinized epithelium: Oral cavity, vagina, cornea,
oesophagus
Stratified squamous epithelium can be broken down according to the condition of
their outer most layer:
o MOIST – found in mouth, oesophagus, rectum and vagina. Consists of
living cells in the deepest and outermost layers. A layer of fluid covers
the outermost layer making them moist
o KERATINIZED – Found in the skin. Consists of living cells in the
deepest layers and outermost layers are composed of dead cells
containing the protein keratin. The dead keratinized cells give the
tissue a durable, moist-resistant dry character.
CUBOIDAL:
 Simple – Excretory ducts, some kidney tubules, germinal epithelium of ovary
 Stratified – Rare: Some parts of excretory ducts
 Pseudostratified – Transitional epithelium of urinary bladder
COLUMNAR:
 Simple – With kinocilia: Uterus, salpinx
Without kinocilia: GIT, gallbladder
 Stratified – Rare: Conjunctival fornix, some parts of male and female urethra
 Pseudostratified – With kinocilia: respiratory tract
Without kinocilia: Rare: some parts of the glandular ducts
With stereocilia: Epididymis and vas deferens
3. Briefly outline the key features of the three muscle types.
SKELETAL
CARDIAC
SMOOTH
LOCATION
Attached to bones
Heart
Walls of hollow
organs, blood
vessels, eyes,
glands and skin
FUNCTION
Body movement
Contracts to move Movement of food
blood through
through digestive
blood vessels
tract, emptying
bladder,
regulation of
blood vessel
diameter, change
in pupil size,
constricts many
gland ducts,
movement of hair
UNIT
Fibre
Cell
Cell
UNIT LENGTH
Can be up to
50 - 120μm
40 - 200μm. In a
several centimetres
pregnant uterus
upto 500μm
UNIT DIAMETER
20 - 100μm
10 -20μm
5 - 10μm
NUCLEUS
Multinucleated,
Single,
Single,
peripherally located centrally located
centrally located
NUCLEAR NO.
100’s to 1000’s
1 to 2
1
NUCLEAR
Sub-sarcolemmal
Central in
Central cytoplasm
LOCATION
perinuclear
cytoplasm free of
myofibrils
NUCLEAR SHAPE
Elongated flat
Plumpish,
Rod shaped or
round to ovoid
elliptical
STRIATIONS
Yes
Yes
No
CONTROL
Voluntary
Involuntary
Involuntary
SPONTANEOUS
No
Yes
Yes
CONTRACTION
SPECIAL FEATURES
Branching fibres,
Gap junctions
intercalated disks
join the cells to
each other (gap
junctions)