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๐ฌ Think about it
Your skin covers you on the outside, and a lining covers your mouth, lungs and intestine on the inside.
The same kind of tissue does both.
How can one tissue protect, absorb and sense?
Let us see.
What is epithelial tissue?
- It is the covering and lining tissue of the body.
- It forms the outer covering of the body (the skin) and also lines the internal organs.
Where is epithelial tissue found?
- Epithelial tissue forms the outer surface of the skin.
- It lines the inside of the mouth.
- It lines the lungs.
- It lines the blood vessels.
- It lines the intestine.
How are cells arranged in epithelial tissue?
- The cells are closely packed , with very little space between them.
Why are epithelial cells closely packed?
- The tight packing prevents germs from entering the body.
- It reduces the loss of water from the body.
- It helps the tissue absorb substances.
- It helps the tissue secrete substances.
- It helps in the movement of substances across the tissue.
What are the different types of epithelial tissue and where are they found?
![3.3.1 Epithelial tissues โ Struc - Tissues in Action - [Teachoo] - Concepts](https://cdn.teachoo.com/a93aebb0-aec4-435a-82e7-7a7ae3e2f033/3.3.1-epithelial-tissues-structure-and-functions-image-36.webp)
| Location in the body | Function | Structure |
|---|---|---|
| (a) Lining of blood vessels and lungs | Exchange โ allows rapid diffusion of gases and liquids | Single layer of thin, flat cells |
| (b) Skin, mouth and oesophagus | Protection โ protects underlying tissues from injury, friction and microbes | Many layers of cells; outer cells flat and tightly packed |
| (c) Salivary glands, sweat glands and stomach lining | Secretion โ makes and releases mucus, enzymes, hormones, sweat and saliva | Cuboidal or columnar cells specialised to release substances |
| (d) Nostrils, taste buds and inner ear | Sensory โ helps in smell, taste, sound and balance | Specialised receptor cells with hair-like cilia |
| (e) Lining of the small intestine | Absorption โ efficient uptake of nutrients and water | Single layer of tall, pillar-like cells, often with a hair-like border |
Important Points
- Epithelial tissue covers the body and lines the internal organs.
- Its cells are closely packed, with little space between them.
- Different shapes suit exchange, protection, secretion, sensing and absorption.
โ Test Yourself
-
Where is epithelial tissue found?
View Answer
As the outer skin and as the lining of internal organs like the mouth, lungs and intestine. -
How are epithelial cells arranged?
View Answer
They are closely packed, with very little space between them. -
Why are epithelial cells closely packed?
View Answer
To block germs, reduce water loss, and assist absorption and secretion. -
Which epithelium lines the small intestine for absorption?
View Answer
A single layer of tall, pillar-like cells.
Important Definitions
- Epithelial tissue โ the covering and lining tissue of the body.
๐ NCERT Question 3 โ Why are the epithelial
Why are the epithelial tissues that line an animal's internal organs usually only one or a few cells thick?
(i) To store food efficiently. (ii) To provide maximum strength. (iii) To allow quick exchange of materials across them. (iv) To reduce friction.
View Answer โ
(i) To store food efficiently. (ii) To provide maximum strength. (iii) To allow quick exchange of materials across them. (iv) To reduce friction.
๐ NCERT Question 6 โ In each of the
In each case (A, B, C, D), choose: (i) Both A and R true, R is correct explanation of A; (ii) Both true, R not the correct explanation; (iii) A true, R false; (iv) A false, R true.
A. Assertion: Epithelium is well-suited for gas exchange in the lungs. Reason: It consists of multiple layers of tall cells that slow down diffusion.
B. Assertion: Cardiac muscle can contract continuously without fatigue. Reason: Cardiac muscle cells have a high number of mitochondria and an abundant blood supply.
C. Assertion: Tendons connect bone to bone and allow joint movement. Reason: Tendons are made of tough connective tissue that transmits force from muscle to bone.
D. Assertion: In a hinge joint, movement occurs primarily in one plane. Reason: The bone ends are shaped to allow sliding in all directions.
View Answer โ
A. Assertion: Epithelium is well-suited for gas exchange in the lungs. Reason: It consists of multiple layers of tall cells that slow down diffusion.
B. Assertion: Cardiac muscle can contract continuously without fatigue. Reason: Cardiac muscle cells have a high number of mitochondria and an abundant blood supply.
C. Assertion: Tendons connect bone to bone and allow joint movement. Reason: Tendons are made of tough connective tissue that transmits force from muscle to bone.
D. Assertion: In a hinge joint, movement occurs primarily in one plane. Reason: The bone ends are shaped to allow sliding in all directions.
