Important Points to Remember & Revision Notes - Tissues

Plant Tissues

1. Meristematic Tissue (Growing Tissues)

Cells are actively dividing and found in specific regions of the plant.

Three types:

1. Apical meristem - Present at the growing tips of stems and roots (increases length).

2. Lateral meristem - Found in the cambium (increases girth of stems/roots).

3. Intercalary meristem - Present at nodes in some plants (helps in regrowth of grasses).

Meristematic cells lack vacuoles because they actively divide and do not store food.

2. Permanent Tissue

Formed when meristematic cells differentiate and lose their ability to divide.

Two types:

1. Simple Permanent Tissue (made of one type of cells)

   • Parenchyma: Thin-walled, living cells; stores food and helps in photosynthesis (chlorenchyma) or buoyancy in aquatic plants (aerenchyma).

   • Collenchyma: Provides flexibility (e.g., leaf stalks) and mechanical support.

   • Sclerenchyma: Dead cells with thick walls, provides strength (e.g., coconut husk).

2. Complex Permanent Tissue (made of different types of cells, used for transportation)

   • Xylem: Conducts water and minerals; made of tracheids, vessels, xylem parenchyma, xylem fibers.

   • Phloem: Conducts food (translocation); consists of sieve tubes, companion cells, phloem fibers, phloem parenchyma.

Protective Tissue

• Epidermis: Outer layer of cells; may have stomata for gas exchange.

• Cork (bark): Dead cells that prevent water loss.

Cuticle: Thick waxy coating in desert plants to reduce transpiration.Protective Tissues

Animal Tissues

Different types of Animal Tissues

1. Epithelial Tissue

Covers the body and lines organs and cavities.

Types:

1. Squamous Epithelium: Thin, flat cells (e.g., lining of blood vessels, alveoli).

2. Cuboidal Epithelium: Cube-shaped cells (e.g., kidney tubules, salivary glands).

3. Columnar Epithelium: Tall, pillar-like cells (e.g., lining of intestines).

4. Ciliated Epithelium: Has cilia to move substances (e.g., respiratory tract).

5. Glandular Epithelium: Modified to secrete substances (e.g., glands).

2. Connective Tissue (Most Abundant in Animals)

Has the largest intercellular spaces.

Types:

1. Blood: Fluid connective tissue; transports oxygen, nutrients, waste.

2. Bone: Hardest tissue; provides structure and support.

3. Cartilage: Smoothens joints; found in nose, ear, trachea.

4. Ligament: Connects bone to bone; provides flexibility.

5. Tendon: Connects muscle to bone; provides strength.

6. Adipose Tissue: Stores fat (found in hump of camels, blubber of whales, thick tail of merino sheep).

7. Areolar Tissue: Binds organs; found between skin and muscles.

3. Muscular Tissue (For Movement)

Contains contractile proteins for contraction and relaxation.

Types:

1. Striated (Skeletal) Muscle: Voluntary, multinucleated, present in limbs.

2. Smooth Muscle: Involuntary, spindle-shaped, found in blood vessels, digestive system.

3. Cardiac Muscle: Involuntary, branched, rhythmic contractions, found in the heart.

4. Nervous Tissue (For Coordination)

Neurons (nerve cells) conduct electrical impulses.

Parts:

1. Cell body (contains nucleus and cytoplasm).

2. Dendrites (receive signals).

3. Axon (transmits signals).

Nerves are bundles of neurons.

Practice Questions

Q1. Why does an organism-plant or animal, require different types of cells in the body?

Ans. Any organism will have a wide range of cell types. This is because each cell type specialises in one particular function. And for the proper working of an organism many functions like food transport, immunity, strength, etc., are needed to be performed properly.

Q2. Why are voluntary muscles also called skeletal muscles?

Ans. Voluntary muscles are also called skeletal muscles because they are mostly attached to the bones and help in body movement.

Q3. Why is the epidermis present as a thick waxy coating of cutin in desert plants?

Ans. A thick waxy coating of cutin is present in desert plants to prevent excessive loss of water during transpiration. Due to this, plants can survive in scarcity of water in deserts.

Q4. How are glandular epithelium formed?

Ans. An epithelial cell often acquires additional specialisation as gland cells, which can secrete substances at the epithelial surface. Sometimes, a portion of the epithelial tissue folds inward and a multicellular gland is formed. This is the glandular epithelium.

Q5.
(a) What is the lining of blood vessels made up of?
(b) What is the lining of small intestine made up of?
(c) What is the lining of kidney tubules made up of?
(d) Where are the epithelial cells with cilia found?
Ans.
(a) Squamous epithelium
(b) Columnar epithelium
(c) Cuboidal epithelium
(d) Respiratory tract