Lecture 1 epithelium
Microscope
types
Light microscope:
- resolution: 0.2 micrometer
Electron microscope:
- Transmission EM: 0.2 nanometer
slide preparation
1) Fixation: stabilization of structure
o Formalin
2) Imbedding in paraffin: to prevent breakdown by liquids or oxygen
3) Cutting of slices: 50 nm-7 μm
4) Cytological staining
o Overview staining
o Cytochemical: identify specifics in cell (e.g. proteins, DNA, sugars, etc)
Embryonic origin
- Cell types that are part of the same basic tissue type can look much different!
- What these cells share is the same embryonic origin.
o Embryology & germ layers
▪ Ectoderm: nervous tissue, skin
▪ Endoderm: digestive tissue, lung
▪ Mesoderm: muscle, connective tissue (from mesenchyme)
4 basic types of tissue
- There are ± 200 different cell types, these are organized in tissues.
- These tissues can be classified in 4 basic types of tissue:
1) Epithelial Tissue: first layer on top of organ
2) Connective Tissue: provides connection between layers
3) Muscle Tissue: produce movement
4) Nervous Tissue: activate muscle tissue
- These basic tissue types are functionally organized in organs (e.g. liver, heart)
Epithelial Tissue
- Epithelium: tissue existing of cells that are tightly connected to each other.
- There are two types:
o Covering epithelia (e.g. skin)
o Glands (invaginaton of epithelial layers)
,Classification epithelia
- epithelium is classified based on
o embryonic origin: ecto-, endo-, or mesodermal
o morphology: shape of the cells
o cell organization: number of cell layers (strata)
cell shapes
Transitional: changes between Squamous and Cuboidal done by stretching
Epithelia: cell layers
SIMPLE: one layer of cells STRATIFIED: multi-layered or looks multi-layered
Characteristics
- No blood circulation, not in between the cells, but going underneath
- Polarized (apical:top and baso:bottom-lateral:between cells)
- Surface specializations
- Presence of a basal membrane
Apical domain
- Microvilli:
o Small fingers: increase surface area
to increase absorption
o Cytoskeleton of actin
(microfilaments)
o Also called brush barrier
- Cilia:
o movement of liquid
▪ sensory function
o Cytoskeleton of microtubuli (tubulin):
vary in length
o Larger than microvilli
, intracellular connections
Tight junction
Adhesion
belt
Terminal
web
Button
desmosome
Hemidesmosome
(a)
Gap junctions
Tight Junctions (Zonula Occludens)
- Round the whole cell
- TJ proteins function like a zipper
- Functions:
o Prevent transport of small molecules between cells
o Membrane proteins of both cells are compartmentalized (apical and basolateral) to
keep them separated
Adhesion Belt (Zonula adhaerens)
- Round the whole cell
- Adhesion between cells
- made by transmembrane-linker proteins: cadherins
- Intercellular: widened
- Intracellular: connected with actin
Gap junctions (nexus)
- Pores in cells for information transfer
- Intercellular transport: 1.5 nm
- Transmembrane proteins: connexins:
- tubule: connection from one connexion to another connexon
- Transport of ions, amino acids, molecules < 1kDa, certain hormones
Button desmosome
- Not round the whole cell
- Makes the strongest connection between cells
- Intracellular: connected with intermediate filaments (keratin, vimentin,
desmin, etc)
- Thicker than actin: stronger
Microscope
types
Light microscope:
- resolution: 0.2 micrometer
Electron microscope:
- Transmission EM: 0.2 nanometer
slide preparation
1) Fixation: stabilization of structure
o Formalin
2) Imbedding in paraffin: to prevent breakdown by liquids or oxygen
3) Cutting of slices: 50 nm-7 μm
4) Cytological staining
o Overview staining
o Cytochemical: identify specifics in cell (e.g. proteins, DNA, sugars, etc)
Embryonic origin
- Cell types that are part of the same basic tissue type can look much different!
- What these cells share is the same embryonic origin.
o Embryology & germ layers
▪ Ectoderm: nervous tissue, skin
▪ Endoderm: digestive tissue, lung
▪ Mesoderm: muscle, connective tissue (from mesenchyme)
4 basic types of tissue
- There are ± 200 different cell types, these are organized in tissues.
- These tissues can be classified in 4 basic types of tissue:
1) Epithelial Tissue: first layer on top of organ
2) Connective Tissue: provides connection between layers
3) Muscle Tissue: produce movement
4) Nervous Tissue: activate muscle tissue
- These basic tissue types are functionally organized in organs (e.g. liver, heart)
Epithelial Tissue
- Epithelium: tissue existing of cells that are tightly connected to each other.
- There are two types:
o Covering epithelia (e.g. skin)
o Glands (invaginaton of epithelial layers)
,Classification epithelia
- epithelium is classified based on
o embryonic origin: ecto-, endo-, or mesodermal
o morphology: shape of the cells
o cell organization: number of cell layers (strata)
cell shapes
Transitional: changes between Squamous and Cuboidal done by stretching
Epithelia: cell layers
SIMPLE: one layer of cells STRATIFIED: multi-layered or looks multi-layered
Characteristics
- No blood circulation, not in between the cells, but going underneath
- Polarized (apical:top and baso:bottom-lateral:between cells)
- Surface specializations
- Presence of a basal membrane
Apical domain
- Microvilli:
o Small fingers: increase surface area
to increase absorption
o Cytoskeleton of actin
(microfilaments)
o Also called brush barrier
- Cilia:
o movement of liquid
▪ sensory function
o Cytoskeleton of microtubuli (tubulin):
vary in length
o Larger than microvilli
, intracellular connections
Tight junction
Adhesion
belt
Terminal
web
Button
desmosome
Hemidesmosome
(a)
Gap junctions
Tight Junctions (Zonula Occludens)
- Round the whole cell
- TJ proteins function like a zipper
- Functions:
o Prevent transport of small molecules between cells
o Membrane proteins of both cells are compartmentalized (apical and basolateral) to
keep them separated
Adhesion Belt (Zonula adhaerens)
- Round the whole cell
- Adhesion between cells
- made by transmembrane-linker proteins: cadherins
- Intercellular: widened
- Intracellular: connected with actin
Gap junctions (nexus)
- Pores in cells for information transfer
- Intercellular transport: 1.5 nm
- Transmembrane proteins: connexins:
- tubule: connection from one connexion to another connexon
- Transport of ions, amino acids, molecules < 1kDa, certain hormones
Button desmosome
- Not round the whole cell
- Makes the strongest connection between cells
- Intracellular: connected with intermediate filaments (keratin, vimentin,
desmin, etc)
- Thicker than actin: stronger
