Icse Tissues
Cell Structure — Icse Tissues
Icse Tissues
Tissue Level Organisation
What is a Tissue?
A tissue is a group of cells that are similar in structure and work together to perform a specific function. Moving from individual cells to tissues is a key step in the organisation of multicellular organisms.
Levels of organisation: Cell → Tissue → Organ → Organ system → Organism
Plant Tissues
1. Meristematic Tissue (dividing tissue)
- Cells are small, thin-walled, with large nuclei — actively dividing
- Found at growing tips: apical meristem (shoot/root tips), lateral meristem (cambium — increases girth)
- Function: growth of plant in length and width
2. Permanent Tissue (stopped dividing)
Simple Permanent Tissue (one cell type)
| Tissue | Description | Function |
|---|---|---|
| Parenchyma | Thin-walled, loosely packed, oval/round cells | Storage, photosynthesis (chlorenchyma), buoyancy (aerenchyma) |
| Collenchyma | Thick at corners, no intercellular spaces | Flexible mechanical support (leaf stalks, stems) |
| Sclerenchyma | Dead cells with very thick, lignified walls | Rigid mechanical support (coconut husk, jute) |
Complex Permanent Tissue (more than one cell type)
| Tissue | Components | Function |
|---|---|---|
| Xylem | Tracheids, vessels, xylem parenchyma, xylem fibres | Conduction of water and minerals upward |
| Phloem | Sieve tubes, companion cells, phloem parenchyma | Conduction of food (sucrose) up and down |
Animal Tissues
1. Epithelial Tissue
- Covers body surfaces, lines organs and cavities
- Tightly packed cells, little intercellular matrix
- Types: squamous (flat), cuboidal (cube-shaped), columnar (column-shaped), ciliated, glandular
- Function: protection, absorption, secretion, sensation
2. Connective Tissue
- Cells scattered in a large intercellular matrix
- Types:
- Areolar: packs organs together, fights infection
- Adipose: fat storage, insulation
- Blood: transport of O₂, nutrients, waste, immunity
- Bone: rigid support, mineral storage
- Cartilage: flexible support (ear, nose, joints)
- Tendon/Ligament: connect muscle-bone / bone-bone
3. Muscular Tissue
| Type | Structure | Control | Location |
|---|---|---|---|
| Striated (skeletal) | Cylindrical, multinucleate, striped | Voluntary | Arms, legs |
| Smooth (unstriated) | Spindle-shaped, uninucleate, no stripes | Involuntary | Gut, blood vessels |
| Cardiac | Cylindrical, branched, intercalated discs | Involuntary | Heart wall only |
4. Nervous Tissue
- Made of neurons (nerve cells)
- Each neuron: cell body (cyton) + dendrites (receive signals) + axon (sends signals)
- Neuroglia: supporting cells surrounding neurons
- Function: receive, process, and transmit electrical signals
ICSE Key Distinctions
- Meristematic vs Permanent: dividing vs non-dividing
- Xylem is dead (tracheids, vessels) but phloem has living cells (sieve tubes + companion cells)
- Sclerenchyma: dead cells → strongest mechanical support; examples: jute fibres, coconut husk
- Cardiac muscle is involuntary but striated — unique combination
- Blood is a liquid connective tissue (matrix = plasma)
Quick Check
- Name the tissue that forms the inner lining of the cheek.
- Which plant tissue conducts food down from leaves?
- Jute fibres are made of which tissue?
- Why is blood classified as connective tissue?
- Stretch: Why can't mature RBCs divide, and what tissue do they belong to?
Key Takeaways (TL;DR)
- What is a Tissue?
- Plant Tissues
- Animal Tissues
- ICSE Key Distinctions
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