Epithelial cells 1/11/2021
Use of a microscope: light microscope = 0.2 micrometer. Electron microscope = 0.2 nanometer.
Preparing microscope slides:
1. Fixation = stabilization of structure. Use of formalin
2. Imbedding in paraffin oxygen cant access
3. Cutting of slices 50 nm- 7 micrometer
4. Cytological staining overview staining, cytochemical = identifies parts of cell.
4 basic types of tissues
All the types of cells can be divided in one of the tissue types, the share same embryology:
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
In the 3 germ layers: ectoderm (will form nervous tissue and skin), endoderm (digestive tissue and
lung), mesoderm (muscle and connective tissue).
Epithelial tissue (chapter 4 page 161-172)
4 essential functions: physical protection, control of permeability, provide sensation and produce
secretions.
Cells tightly connected to each other. Derived from one of three primary germ layers (ecto- endo- or
meso-derm):
Covering epithelia cover all surfaces, inside and outside (skin etc.)
Glands secrete products, attached to or derived from epithelia.
Epithelium classified based on embryonic origin, shape of cell or number of layers. Shapes can be:
Squamous = flat
Cuboidal = square shaped
Columnar = elongated
Cell layers:
Simple epithelium = one layer,
for example in kidney. (for exchange)
Stratified (exposed to more stress, can be keratinized)
o Stratified = multiple layers
o Pseudo stratified = looks stratified but is not, because cells all bind to connective
tissue
Combination:
Simple squamous = delicate, absorption and secretion, lungs, blood vessels etc.
Stratified squamous = physical protection, skin surface etc.
Simple cuboidal = limited protection, secretion and absorption, glands an kindey
Stratified cuboidal = rare, along ducts of sweat glands
Simple columnar = absorption and secretion, stomach
Stratified columnar = rare, protection from two or more layers.
Pseudo stratified columnar = respiratory tract, have cilia
Transitional epithelium can change from cuboidal to squamous, for example in kidneys.
,Characteristics of epithelia 1. avascular (no blood vessels through the epithelium). 2.Polarity, the
apical site is the top, basal site the bottom. 3. Cellularity, cells closely together by cell junctions. 4.
Attachment to basal lamina. 5. Regeneration, higher than in other tissue. Specialized epithelial cells
have apical surface and baso-lateral surface.
Apical domain microvilli which increase surface area (extension of cytoskeleton from actin) . Cilia
are for movement and sensory function 5x larger than microvilli (microtubules and no actin).
Epithelium has many intracellular connections tight junction, adhesion belt, terminal web, button
desmosome. 3 types of cell junctions: gap junctions, tight junctions
Tight junction
and desmosomes.
Tight junction = zonula occludens around the whole cell and
Adhesion
functions like a zipper. Prevents transport between cells, belt
membrane proteins of both cells compartmentalized to keep T erminal
them separated. Proteins on apical site stay there. Only above web
Button
terminal web. desmosome
Adhesion belt = zonula adhearens around the whole cell,
adhesion between cells. Made by cadherins. Intercellular
widened, intracellular connected with actin. Bound to
terminal web.
Gap Junction = nexus, intercellular transport, 1.5 nm.
Transport ions, aminoacides etc. Made of connexins.
Button Desmosomes = not around the whole cell, makes Hemidesmosome
(a)
strongest connection between cells. Intracellular connected Gap junctions
with intermediate filaments (thicker and stronger than actin).
o Hemidesmosome = half of it. Integrins connect the cells with connective tissue
underneath. Connect with basal lamina.
basal domain hemidesmosomes, basal lamina and invagination of plasma membrane, to increase
surface area. (to take up oxygen and glucose)
Gland tissue
Often invagination of gland tissue. Parenchyma and stroma (connective tissue) often presence of
secretion vesicles.
Secretion:
Exocrine glands = release via duct to epithelial surface.
, Endocrine glands = release hormones directly to lumen, blood of lymph. (no duct)
Glands can be classified by: structure gland, way of secretion and products.
Unicellular glands consist of goblet cells. = secrete mucin, which form mucus (called mucous cells
when not in columnar in darmen). Multicellular glands form secretory sheet.
3 methods of secretion:
Merocrine = saliva, product secreted via vesicles.
Apocrine = mammary gland, top of cell detached and released.
Holocrine = sebum around hair, whole cell is secreted by bursting open.
Primary components in secretion: ribosomes, RER and Golgi. Rough ER because of ribosomes.
Golgi-apparatus glycosylation of proteins and sorting of proteins (secretion vesicles, cell
membrane of lysosomes).
Exocytosis = release of product on cellular surface.
Steroids-producing gland extensive smooth ER or specialized mitochondria. There is no storage of
steroid in the cell. If lipid droplet touches membrane it will dissolve.
Use of a microscope: light microscope = 0.2 micrometer. Electron microscope = 0.2 nanometer.
Preparing microscope slides:
1. Fixation = stabilization of structure. Use of formalin
2. Imbedding in paraffin oxygen cant access
3. Cutting of slices 50 nm- 7 micrometer
4. Cytological staining overview staining, cytochemical = identifies parts of cell.
4 basic types of tissues
All the types of cells can be divided in one of the tissue types, the share same embryology:
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
In the 3 germ layers: ectoderm (will form nervous tissue and skin), endoderm (digestive tissue and
lung), mesoderm (muscle and connective tissue).
Epithelial tissue (chapter 4 page 161-172)
4 essential functions: physical protection, control of permeability, provide sensation and produce
secretions.
Cells tightly connected to each other. Derived from one of three primary germ layers (ecto- endo- or
meso-derm):
Covering epithelia cover all surfaces, inside and outside (skin etc.)
Glands secrete products, attached to or derived from epithelia.
Epithelium classified based on embryonic origin, shape of cell or number of layers. Shapes can be:
Squamous = flat
Cuboidal = square shaped
Columnar = elongated
Cell layers:
Simple epithelium = one layer,
for example in kidney. (for exchange)
Stratified (exposed to more stress, can be keratinized)
o Stratified = multiple layers
o Pseudo stratified = looks stratified but is not, because cells all bind to connective
tissue
Combination:
Simple squamous = delicate, absorption and secretion, lungs, blood vessels etc.
Stratified squamous = physical protection, skin surface etc.
Simple cuboidal = limited protection, secretion and absorption, glands an kindey
Stratified cuboidal = rare, along ducts of sweat glands
Simple columnar = absorption and secretion, stomach
Stratified columnar = rare, protection from two or more layers.
Pseudo stratified columnar = respiratory tract, have cilia
Transitional epithelium can change from cuboidal to squamous, for example in kidneys.
,Characteristics of epithelia 1. avascular (no blood vessels through the epithelium). 2.Polarity, the
apical site is the top, basal site the bottom. 3. Cellularity, cells closely together by cell junctions. 4.
Attachment to basal lamina. 5. Regeneration, higher than in other tissue. Specialized epithelial cells
have apical surface and baso-lateral surface.
Apical domain microvilli which increase surface area (extension of cytoskeleton from actin) . Cilia
are for movement and sensory function 5x larger than microvilli (microtubules and no actin).
Epithelium has many intracellular connections tight junction, adhesion belt, terminal web, button
desmosome. 3 types of cell junctions: gap junctions, tight junctions
Tight junction
and desmosomes.
Tight junction = zonula occludens around the whole cell and
Adhesion
functions like a zipper. Prevents transport between cells, belt
membrane proteins of both cells compartmentalized to keep T erminal
them separated. Proteins on apical site stay there. Only above web
Button
terminal web. desmosome
Adhesion belt = zonula adhearens around the whole cell,
adhesion between cells. Made by cadherins. Intercellular
widened, intracellular connected with actin. Bound to
terminal web.
Gap Junction = nexus, intercellular transport, 1.5 nm.
Transport ions, aminoacides etc. Made of connexins.
Button Desmosomes = not around the whole cell, makes Hemidesmosome
(a)
strongest connection between cells. Intracellular connected Gap junctions
with intermediate filaments (thicker and stronger than actin).
o Hemidesmosome = half of it. Integrins connect the cells with connective tissue
underneath. Connect with basal lamina.
basal domain hemidesmosomes, basal lamina and invagination of plasma membrane, to increase
surface area. (to take up oxygen and glucose)
Gland tissue
Often invagination of gland tissue. Parenchyma and stroma (connective tissue) often presence of
secretion vesicles.
Secretion:
Exocrine glands = release via duct to epithelial surface.
, Endocrine glands = release hormones directly to lumen, blood of lymph. (no duct)
Glands can be classified by: structure gland, way of secretion and products.
Unicellular glands consist of goblet cells. = secrete mucin, which form mucus (called mucous cells
when not in columnar in darmen). Multicellular glands form secretory sheet.
3 methods of secretion:
Merocrine = saliva, product secreted via vesicles.
Apocrine = mammary gland, top of cell detached and released.
Holocrine = sebum around hair, whole cell is secreted by bursting open.
Primary components in secretion: ribosomes, RER and Golgi. Rough ER because of ribosomes.
Golgi-apparatus glycosylation of proteins and sorting of proteins (secretion vesicles, cell
membrane of lysosomes).
Exocytosis = release of product on cellular surface.
Steroids-producing gland extensive smooth ER or specialized mitochondria. There is no storage of
steroid in the cell. If lipid droplet touches membrane it will dissolve.
