ICSE 9 Biology Tissues Short

⚡ Quick Revision: Introduction to Plant Tissues

Meristematic Tissue (Growth Tissue)

• ✔ Cells are small, cubical, with thin cellulose walls and dense cytoplasm.
• ✔ Continuously dividing cells found at growth regions like root and shoot tips.
• ✔ Vacuoles are usually absent because cells are metabolically very active.

Type of Meristem	Location	Function
Apical Meristem	Tips of roots and stems	Increase in length (Primary growth).
Lateral Meristem	Below bark (Cambium)	Increase in thickness/girth.

Term Card

Differentiation: The process by which meristematic cells take up a permanent shape, size, and function to become permanent tissue.

[Diagram: Labeled Apical and Lateral Meristem]

Position of Meristems

❌ Don't Confuse:

Meristematic with Permanent tissue. Meristematic cells divide forever; Permanent cells have lost the ability to divide.

⚡ Quick Revision: Permanent Plant Tissues

1. Simple Permanent Tissues

• ✔ Parenchyma: Living cells with thin walls; primary function is storage and photosynthesis.
• ✔ Collenchyma: Living cells thickened at corners; provides flexibility and mechanical support.
• ✔ Sclerenchyma: Dead cells with thick lignified walls; provides rigidity (e.g., coconut husk).

Feature	Parenchyma	Collenchyma	Sclerenchyma
Vitality	Living	Living	Dead
Cell Wall	Thin (Cellulose)	Thick corners	Very thick (Lignin)

Term Card

Aerenchyma: Specialized parenchyma with large air cavities found in aquatic plants to help them float.

❌ Don't Confuse:

Chlorenchyma with Collenchyma. Chlorenchyma is parenchyma with chlorophyll; Collenchyma is the support tissue in stems.

⚡ Quick Revision: Complex Permanent Tissues (Vascular Bundles)

What makes them "Complex"?

• ✔ Composed of more than one type of cell working together as a single unit.
• ✔ Responsible for the conduction of water, minerals, and food throughout the plant.
• ✔ Includes two main types: Xylem (Water-conducting) and Phloem (Food-conducting).

Feature	Xylem (Wood)	Phloem (Bast)
Function	Conducts water & minerals upward from roots.	Conducts prepared food (sugar) to all parts.
Components	Tracheids, Vessels, Xylem Fibres, Xylem Parenchyma.	Sieve tubes, Companion cells, Phloem Fibres, Phloem Parenchyma.
Flow Direction	Unidirectional (Only Up)	Bidirectional (Up & Down)

Term Card

Tracheary Elements: Tracheids and Vessels are the main conducting elements of xylem; both are dead at maturity.

❌ Don't Confuse:

Xylem Parenchyma with other xylem cells. It is the only living component of the xylem; all others are dead.

⚡ Quick Revision: Animal Tissues - Epithelial

Epithelial Tissue (Covering Tissue)

• ✔ Forms the outer protective layer of the body and lines internal organs.
• ✔ Cells are tightly packed with very little intercellular space; rests on a basement membrane.
• ✔ Acts as a barrier to keep different body systems separate.

Type	Cell Shape	Location
Squamous	Flat, scale-like	Lining of blood vessels, lung alveoli.
Cuboidal	Cube-like	Kidney tubules, salivary glands.
Columnar	Pillar-like	Inner lining of stomach and intestines.
Ciliated	Columnar with cilia	Respiratory tract (moves mucus).

Term Card

Stratified Squamous: Squamous cells arranged in multiple layers (strata) to prevent wear and tear, found in the Skin.

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Variations in Epithelial Cells

❌ Don't Confuse:

Glandular Epithelium is simply columnar or cuboidal epithelium that has folded inward to secrete chemicals (like sweat or oil).

⚡ Quick Revision: Animal Tissues - Connective

Connective Tissue (Binding Tissue)

• ✔ Cells are loosely spaced and embedded in an intercellular **matrix**.
• ✔ Connects different organs, provides support, and transports materials.
• ✔ Includes specialized forms like **Fibrous**, **Skeletal**, and **Fluid** tissues.

Sub-Type	Structure/Location	Primary Function
Areolar	Between skin and muscles.	Support and repair of tissues.
Adipose	Below skin (Fat cells).	Storage of fat & insulation.
Tendons	Strong fibrous tissue.	Connects Muscle to Bone.
Ligaments	Highly elastic tissue.	Connects Bone to Bone.

Term Card

Matrix: The non-living ground substance in which connective tissue cells are suspended; can be jelly-like, fluid, or hard.

❌ Don't Confuse:

Tendons with Ligaments. Memory Hack: M-T-B (Muscle-Tendon-Bone) vs B-L-B (Bone-Ligament-Bone).

⚡ Quick Revision: Skeletal & Fluid Connective Tissue

Skeletal Tissue (Supportive)

• ✔ Bone: Hard, non-flexible matrix rich in Calcium and Phosphorus; contains Osteocytes.
• ✔ Cartilage: Flexible matrix with widely spaced cells (Chondrocytes); smooths bone surfaces at joints.
• ✔ Found in the nose tip, external ear (pinna), trachea, and larynx.

Fluid Tissue	Composition	Main Function
Blood	Plasma + RBCs, WBCs, Platelets.	Transport of gases, nutrients, and hormones.
Lymph	Plasma + WBCs (No RBCs).	Immunity and drainage of excess tissue fluid.

Term Card

Haversian Canals: Microscopic tubes in the bone matrix that allow blood vessels and nerves to pass through.

Microscopic Structure of Bone

❌ Don't Confuse:

Osteocytes with Chondrocytes. Osteo = Bone; Chondro = Cartilage. Both are mature cells of their respective tissues.

⚡ Quick Revision: Muscular & Nervous Tissue

Muscular Tissue (Contractile)

• ✔ Consists of elongated cells called muscle fibres responsible for movement.
• ✔ Movement occurs due to special proteins called contractile proteins (actin and myosin).
• ✔ Classified into three types: Striated, Non-striated, and Cardiac.

Feature	Striated (Skeletal)	Smooth (Visceral)	Cardiac (Heart)
Control	Voluntary	Involuntary	Involuntary
Nucleus	Multinucleated	Uninucleated	Uninucleated
Fatigue	Tires easily	Does not fatigue	Never fatigues

Nervous Tissue (Conducting)

• ✔ Specialized to transmit electrical impulses (stimuli) rapidly.
• ✔ The unit of nervous tissue is the **Neuron** (nerve cell).
• ✔ Consists of a cell body (**Cyton**), **Dendrites**, and a long **Axon**.

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Term Card

Synapse: The microscopic gap between the axon terminal of one neuron and the dendrite of the next through which impulses pass.

❌ Don't Confuse:

Nerve with Neuron. A neuron is a single cell; a nerve is a bundle of many axons (nerve fibres) wrapped together.

⚡ Quick Revision: Plant vs. Animal Tissues (Summary)

Feature	Plant Tissues	Animal Tissues
Growth	Localized (Meristems)	Uniform (Throughout body)
Dead vs Living	Mostly dead cells for support	Mostly living cells
Energy Needs	Lower (Stationary)	Higher (Mobile)

Exam Checklist: Can you describe?

• ✔ The location and role of **Cambium** in secondary growth.
• ✔ Difference between **Simple** and **Complex** permanent tissues.
• ✔ The structural unit of bone (Haversian system) vs cartilage (Lacunae).

Term Card

Histology: The branch of biology that deals with the microscopic study of tissues (Father of Histology: Bichat).

❌ Don't Confuse:

Sieve Tubes (Phloem) with Vessels (Xylem). Sieve tubes are living but lack a nucleus; Vessels are dead tubes.