Post on 15-Jan-2016
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Epithelia
1.Cell: the basic structure of human cell
2.Tissue: consists of cells and intercellular substance
3.Organ: consists of different tissues which have
related function 4.System: consists of different organs which have related function
Human organization
HumanTissues
Epithelia
Connective tissue
Muscle Tissue
Nervous tissue
一、 General characteristics and classification of epithelia
(一) General characteristics of epithelia
1. cells arranged intensively;small quantity of intercellular substance. 2. cells have polarity.
3. no blood vessels.
4. Function: : Protection, secretion, and absorption,etc.
(二) Classification of Epithelia
Epithelia mainly classified into 2 sorts:
Covering epithelia : Cells arranged like membrane
Localization: covering the outer surface of the body and the inner
surface of the cavities ,Sacs or ducts within the body.
Function: Protection.
Glandular epithelia : Function- Secretion
二、 covering epithelia
Principles of the classification :
Layers of the cells : simple epithelia stratified epithelia
Shape of the cells : Squamous epithelia Cuboidal epithelia Columnar epithelia
Simple squamous epithelia Simple cuboidal epithelia Simple columnar epithelia
Stratified squamous epithelia Transitional epitheliaPseudostratified ciliated columnar epithelia
1. simple squamous epithelia
Description: Single layer of flat cells with disc- shaped central nuclei.Top view: Polygonal, central nucleiSide view: Squamous, central nuclei
Function: Allows passage of material by diffusion & filtration and reduces friction by providing a smooth surface & secreting lubricating serous fluid.
Simple
squamous epithelia
endothelium : heart, blood vessles lymphatics
mesothelium : Pericardium, pleura peritoneum
others : alveoli of the lungs, glomeruli in the kidney, etc
Localization
simple squamous epithelium
(1) endothelium
endothelium
(2) mesothelium
(3) others
2. simple cuboidal epithelium
Description: Single layer of cubelike cells with large, spherical central nuclei.
Function: Function in secretion and absorption.
Locations: (1) In the secretory portions of many glands : thyroid, mammary, and salivary. (2) In the kidney tubules
simple cuboidal epithelium
simple cuboidal epithelium
simple cuboidal epithelium
3. simple columnar epithelium
Description: Single layer of columnar cells with oval nuclei ; often have an apical border of microvilli; Many contain goblet cells (mucus-secreting unicellular glands).
Function: absorption of nutrients; secretion of mucus & enzymes.
Locations: digestive tract,etc.
simple columnar epithelium
simple columnar epithelium
simple columnar epithelium
4. pseudostratified ciliated columnar epithelium
Description: single layer of cells of differing heights, but some don't reach the free surface. Nuclei are seen at many different levels. They contain goblet cells and cilia.
Function: secretion & propulsion of mucus
Locations: l the trachea & most of the upper respiratory tract.
pseudostratified ciliated columnar epithelium
pseudostratified ciliated columnar epithelium
pseudostratified ciliated columnar epithelium
5. stratified squamous epithelium
Description: multiple layers of cells. Surface cells are flattened. Basal cells: cuboidal or columnar; active in mitosis and produce the cells of the more superficial layers.
Function: resists abrasion and acts as a barrier, Retards water loss through skin.
Locations: skin, mouth, vagina, esophagus , etc.
Stratified
Squamous
epithelium
keratinized stratified squamous epithelium: skin Surface is covered with layers of compact dead cells without nuclei (and full of keratin)
nonkeratinized stratified squamous epithelium:esophagus,oral cavity
stratified squamous epithelium
keratinized stratified squamous epithelium
nonkeratinized stratified squamous epithelium
7. transitional epithelium
Description: multiple layers of cells. Surface cells are dome-shaped. Middle layers: cells are polyhedral Basal cells: cuboidal or columnar.
Locations: renal pelvis and calyces,the ureter, the urinary bladder ,etc.
transitional epithelium
transitional epithelium
transitional epithelium
6.stratified columnar
epithelium
(一) surface of epithelia
1. microvillus 2. cilium
三、 special structure of each side
1.Microvillus function : enlarge the area of the surface
2.Cilium Function : regularly swing
1. tight junction
2. intermediate junction
3. desmosome
4. gap junction
(二) side face of epithelia
(三 ) Underside of the
epithelia
1. basement membrane
2. plasma membrane infolding
3. hemidesmosome
1.basement membrane Function:support,connect,etc.
2.plasma membrane infolding function : enlarge the area of the
underside
3.Hemidesmosome Function:fixing