Epithelial tissue is arranged in single and multiple layers of cells. Epithelial tissues are lining and cover throughout the body. Epithelial tissue forms the outer covering of the skin and it also form the inner lining of blood vessels, body cavity, ducts, respiratory, digestive, urinary and reproductive systems. Some epithelial tissues have glandular like structure that makes up thee secretion portion of glands such as sweat gland, adrenal gland and thyroid gland.
Classification of Epithelial Cells
Mainly epithelial tissue divided into two parts :-
- Simple epithelial tissue
- Stratified epithelial tissue
Simple Epithelial Tissue
- Simple squamous epithelium tissue
- Simple cuboidal epithelium tissue
- Simple columnar epithelium tissue (nonciliated and ciliated)
- Ciliated simple columnar epithelium tissue
- Pseudostratified epithelial tissue
- Pseudostratified nonciliated columnar epithelium tissue
- Pseudostratified ciliated columnar epithelium tissue
Stratified Epithelial Tissue
In stratified epithelial tissue, cells arranged in two or more layers. Cells arranged on basement membrane. Structurally and functionally stratified epithelial tissue further classified into following types :
- Stratified squamous epithelium tissue
- Nonkeratinized stratified squamo`us epithelium tissue
- Stratified cuboidal epithelium tissue
- Stratified columnar epithelium tissue
- Transitional epithelium tissue
- Glandular epithelium tissue
- Exocrine glands
Simple squamous epithelium tissue
Simple squamous epithelium tissue composed with multiple flat cells and make Single layer. Viewed from apical surface of Stratified epithelial tissue resembles like a tiled floor. Nucleus present in central that is oval shaped.
Location of simple squamous epithelial tissue
- Lining on the heart
- Blood vessels
- Lymphatic vessels
Functions
- Present at the site of filtration in kidney.
- Present at diffusion site such as lungs and blood vessels.
- Present in serous membrane.
Simple cuboidal epithelium tissue
Simple cuboidal epithelium tissue is composed with single layer of cube shaped cells. Nucleus is centrally located.
Location of simple cuboidal epithelium tissue
- Surface Lining on ovary and kidney tubules
- Make up secretion of some glands, such as thyroid gland
Function
- Secretion and absorption
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| Simple Cuboidal Epithelial tissue |
Nonciliated simple columnar epithelium tissue
Nonciliated simple columnar epithelium tissue is composed with column shape, single layer and nonciliated cells.
Location of nonciliated simple columnar epithelium tissue
- Lining on gastrointestinal tract and gallbladder.
Functions of nonciliated simple columnar epithelium tissue
- Secretionand absorption
- Secreted mucus lubricating lining of respiratory, digestive and reproductive system.
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| Nonciliated simple columnar epithelium tissue |
Ciliated simple columnar epithelium tissue
Ciliated simple columnar epithelium tissue is composed with column shape, single layer and ciliated cells. Oval shape nuclei present near base of cells.
Location of ciliated simple columnar epithelium tissue
- Lining of fallopian tube (uterine), uterus, bronchioles of respiratory tract.
Functions
- Cilia help moving mucus and foreign particles toward throat.
- Sneezingand coughing speed up movement of cilia and mucus.
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| Ciliated simple columnar epithelium tissue |
Pseudostratified columnar epithelium tissue
Several layers of column cells shaped are composed pseudostratified columnar epithelium tissue. Multiple nuclei are present at various levels. All cells are attached to basement membrane.
Pseudostratified ciliated columnar epithelium tissue
Pseudostratified ciliated columnar epithelium tissue contains goblet cell which secrets mucus. These cells are bear cilia.
Location of pseudostratified ciliated columnar epithelium tissue
- Pseudostratified ciliated columnar epithelium tissue lines of upper respiratory tract.
Function of pseudostratified ciliated columnar epithelium tissue
- Pseudostratified ciliated columnar epithelium tissue secretes mucus that traps foreign particles and sweep away mucus for elimination from body.
Pseudostratified ciliated columnar epithelium tissue
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| Pseudostratified ciliated columnar epithelium tissue |
Pseudostratified nonciliated columnar epithelium tissue
Pseudostratified nonciliated columnar epithelium tissue contains cells without cilia and lacks of secrets mucus.
Location of pseudostratified nonciliated columnar epithelium tissue
- Pseudostratified nonciliated columnar epithelium tissue lines of larger ducts of glands.
Function of pseudostratified nonciliated columnar epithelium tissue
- Pseudostratified nonciliated columnar epithelium tissue functions in protection and absorption.
Stratified squamous epithelium
Two or more layer of cells. Few cells in apical layer and several layers are deep to squamous.
Stratified squamous epithelial tissues are two types
- Keratinized stratified squamous epithelium
- Nonkeratinized stratified squamous epithelium
Keratinized stratified squamous epithelium tissue
Keratinized stratified squamous epithelium tissue develops tough layer of keratin protein in both apical and deep layer. Keratin protein is helps protect skin from heat, chemicals and microbes.
Location of Keratinized stratified squamous epithelium tissue
- Keratinized stratified squamous epithelium tissue are forms superficial layer of skin.
Function of Keratinized stratified squamous epithelium tissue
- Protect against water loss, ultraviolet radiation, abrasion and foreign invasion
Nonkeratinized stratified squamous epithelium tissue
Nonkeratinized stratified squamous epithelium tissue does not contain huge amount of keratin protein in apical and deep layers.
Location of nonkeratinized stratified squamous epithelium tissue
- Nonkeratinized stratified squamous epithelium tissue are lining of mouth, esophagus, epiglottis and vagina.
Function of nonkeratinized stratified squamous epithelium tissue
- Protect against water loss, ultraviolet radiation, abrasion and foreign invasion
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| Nonkeratinized stratified squamous epithelium tissue |
Stratified cuboidal epithelium tissue
Cells are arranged in two or more layer on basement membrane. Cellsin apical layer are cube shaped.
Location of stratified cuboidal epithelium tissue
- Sweat gland
- Esophagus
- Male urethra
Function of stratified cuboidal epithelium tissue
- Protection
- Secretion
- Absorption
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| Stratified cuboidal epithelium tissue |
Stratified columnar epithelium tissue
Basal layer consist irregularly shaped cells.
Apical layer has column shaped cells.
Location of
- Urethra
- Esophageal glands
- Conjunctiva of eyes
Function of stratified columnar epithelium tissue
- Protection
- Secretion
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| Stratified columnar epithelium tissue |
Transitional epithelium tissue
Looks similar as stratified cuboidal epithelium tissue
Apical layer cells are large and rounded.
Tissueis stretched, cells become flatter.
Location of transitional epithelium tissue
- Urinary bladder
- Urethra
- Ureters
Function of transitional epithelium
- Allow urinary organ to stretch.
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| Relaxed transitional epithelium |
Glandular epithelium tissue
Endocrine glands
Secretions (hormones) directly enter into bloodstream, without though any duct likestructure.
Location of endocrine gland
- Pituitary gland
- Pineal gland
- Adrenal gland
- Thymus gland
Function of endocrine gland
- Hormonesmaintain various physiological activities.
- Hormonesregulate many metabolic activities.
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| Endocrine gland |
Exocrine gland
Secretary products released into ducts.
Location of exocrine gland
- Earwax gland
- Sweat gland
- Oil gland
Function of exocrine gland
- Produce sweat to regulate body temperature.
- Produce oil, earwax, saliva and digestive enzymes.
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| Exocrine gland |
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