Infographic explaining epithelial tissue as the body’s first line of defence, showing core characteristics, classification by layers and cell shape, comparison of squamous and columnar epithelium, and key functions such as protection, absorption, and secretion.

Class 9, Science, Chapter-6, Lecture-4, Animal Epithelial Tissue (Notes)

Classification of Animal Tissues

Chart classifying animal tissues into epithelial, connective, muscular, and nervous tissues with their major types and subtypes

Epithelial Tissue

A thin layer of tissue that covers organs, glands, and other structures within the body and are exposed to either a body fluid or to the outside environment are called epithelial tissues.

Examples: Outer layer of skin (epidermis), lining of intestines, lining of respiratory tract, lining of abdominal cavity, sweat glands.

Types of Epithelium (Based on Layers)

Type	Location	Role
Simple Epithelium	Blood vessels, lung alveoli, oesophagus, mouth	Protection and exchange of materials through selective permeability
Stratified Epithelium	Outer lining of skin	Protection and prevention of wear and tear
Pseudostratified Epithelium	Upper respiratory tract	Movement of mucus

Types of Epithelium (Based on Shape)

Type	Location	Role
Squamous Epithelium	Blood vessels, lung alveoli, oesophagus, mouth	Protection and exchange through selective permeability
Columnar Epithelium	Inner lining of intestine	Absorption and movement
Cuboidal Epithelium	Kidney tubules, salivary ducts	Mechanical support

Characteristics of Epithelial Tissue

Cells are tightly packed and form a continuous sheet.
Very little or no intercellular space.
Small amount of cementing material present.
Separated from underlying tissue by a basement membrane.

Functions of Epithelial Tissue

Protection: Prevents loss of water and entry of microorganisms.
Absorption: Helps in absorption of nutrients in intestine.
Secretion: Produces enzymes and hormones.
Movement: Cilia help in movement of food and mucus.
Excretion: Removes wastes through kidney and sweat glands.
Filtration: Filters dust and microbes in respiratory tract.
Exchange of materials: Allows selective diffusion.
Sensory reception: Helps in taste perception.
Mechanical support: Provides structural support in ducts.

Differences between:

Squamous Epithelium	Columnar Epithelium
The cells are thin and flat.	The cells are pillar-like.
The nuclues lies in the centre which is generally bulged out.	The nucleus lies near the base.
It occurs in lung alveoli, blood capillaries, Bowman’s capsule, buccal cavity, skin, etc.	It occurs in lining layer of stomach and intestine, their glands and covering of epiglottis.
It functions as selectively permeable barrier, in ultra filtration and bear wear and tear.	It takes part in absorption, secretion and protective covering.

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