Ch 05: Tissue | Exam Fusion Prep

📖 What is Tissue?

Group of cells similar in origin and basic structure, functioning together as a unit
Division of Labour in multicellular organisms

Level:Cell → Tissue → Organ → Organ System → Animal

🌿 Plant Tissue — Overview

1. Meristematic Tissue

Capable of continuous cell division
Immature / undifferentiated tissue
Present in developing parts of plant
No intercellular space, no vacuole
Prominent nucleus, dense cytoplasm
Thin cell wall of cellulose

2. Permanent Tissue

Living and dead tissues — no dividing capacity
Fundamental and structural tissues
Formed by differentiation of meristematic tissues
Defined shape and size
Thin cytoplasm, large central vacuole
Intercellular space may be present or absent

🐾 Animal Tissue — Overview

Epithelial

Protective / Lining tissue

Connective

Connects organs

Muscular

Movement & locomotion

Nervous

Sensitivity & coordination

⚡ Quick Recall

Animal tissues are mostly living. The four types are: Epithelial · Connective · Muscular · Nervous → ECMN

🌱 Types of Meristematic Tissue

(i) Apical Meristem

Location: Developing tips of shoots and roots
Function: Elongation of shoots and roots

(ii) Intercalary Meristem

Location: Base of leaves and nodes/internodes of branches
Function: Growth in length of stems and leaves

(iii) Lateral Meristem

Location: Along the sides of stems and roots
Function: Increases thickness of stems and roots

⚠ Exam Trap

Apical = Length (tips) | Intercalary = Length (nodes/base of leaves) | Lateral = Thickness (girth/width). These have three distinct functions and locations.

Protoderm = primary meristem near root and shoot apices; forms mainly the epidermal tissue system.

⚡ Quick Recall

Cork cambium (phellogen) is a lateral meristem. It produces cork (phellem), a secondary protective tissue of dead, suberin-containing cells.

🍃 Simple Permanent Tissue (Same cell types)

1. Parenchyma

Simplest permanent tissue
Location: Cortex & pith of stem/root, Mesophyll of leaves
Living, isodiametric cells
Thin wall, intercellular space present
Function: Storage of food and water

Modifications:

Chlorenchyma: Has chloroplast → photosynthesis (leaves, herbaceous stem)
Aerenchyma: Large air spaces → buoyancy in aquatic plants

2. Collenchyma

Location: Petiole below epidermis, hypodermis of dicot stems
Cells: Living and elongated
Intercellular space usually absent
Deposition of stiff thick cellulose-hemicellulose-pectin at corners of cell
Function: Mechanical support and flexibility

3. Sclerenchyma

Location: Stem, leaf veins, seed coat, outer fibrous husk of coconut
Cells: Dead, elongated, narrow, pointed at both edges
Thick wall: Cellulose + Lignin
Intercellular space absent
Function: Safety, strength and mechanical support

⚠ Exam Trap

Parenchyma = Living | Collenchyma = Living | Sclerenchyma = Dead. Coconut husk = Sclerenchyma. Aerenchyma helps aquatic plants float.

🔀 Complex Permanent Tissue (Different cell types)

Xylem (Water conducting)

Unidirectional transport
Water & minerals: Roots → Stem → Leaves
Components:
- Tracheids
- Vessels
- Xylem Parenchyma (Living)
- Xylem Fibre

Phloem (Food conducting)

Bidirectional transport
Food: Usually leaves → other parts

⚠ Exam Trap

Xylem = Unidirectional (water, roots to leaves). Phloem = Bidirectional (food). Xylem parenchyma = Living component of xylem; this is a common exam trap.

🛡️ Protective Tissue — Overview

Provides safety against mechanical injury, infection and extra water loss
Two types: Epidermis and Cork

1. Epidermis

Outermost, continuous, single-layered protective layer
Usually waxy waterproof layer present
Protects from water loss and mechanical damage
Cuticle: Waterproof thick waxy layer — found in desert plants
Small pores called Stomata present on epidermis of leaf
Stomata regulate: Transpiration + Gaseous exchange
Stomata opening/closing by Guard cells
Dicots: Bean-shaped guard cells
Grasses: Dumbbell-shaped guard cells
Root epidermis modified into Root hair → increases surface area for water absorption

💧 Stomata Guard Cell Mechanism

Condition	Guard Cell State	Stomata
Water enters guard cell	Turgid (swells)	Opens
Water exits guard cell	Loose / Relaxed (shrinks)	Closes

⚠ Exam Trap

Guard cells: Many dicots = Bean-shaped | Grasses = Dumbbell-shaped. This difference in shape is frequently tested directly in MCQs.

2. Cork

Multilayered thick, dead cells formed from secondary meristem
Intercellular space absent, arranged densely
Suberin deposition in cell walls (makes it waterproof)

⚡ Quick Recall

Cork cells = Dead + Suberin = Waterproof + No intercellular space. Robert Hooke observed cork cells and called the compartments “cells.”

🛡️ Epithelial Tissue

Protective tissue of animal body
Forms lining of body surfaces, organs and organ-system cavities
Continuous and dense cellular level

📋 Types of Epithelial Tissue

Type	Description	Location
Squamous — Simple	Thin, flat, single layer	Lining of blood vessels and lung alveoli
Squamous — Stratified	Multilayered	Skin epidermis; non-keratinised form in mouth and oesophagus
Cuboidal	Cube-shaped cells	Kidney tubules, Sweat glands, Salivary glands, Thyroid glands
Columnar	Column-shaped cells	Stomach, Intestines, Gall bladder, Bile duct
Ciliated Columnar	Multiple hair-like protrusions on free surface	Trachea and Oviduct
Glandular — Single cell	Goblet cells	—
Glandular — Multi cell	Glands	Salivary glands, Thyroid glands

⚠ Exam Trap

Ciliated columnar = Trachea and Oviduct; the cilia move particles. Cuboidal = Kidney tubules. Skin = Stratified squamous.

⚡ Quick Recall

Simple epithelial types: Squamous · Cuboidal · Columnar · Ciliated columnar → SC³

🔗 Connective Tissue — Overview

Connects different organs of body with each other
Cells embedded in intercellular matrix

🦴 Fibrous Connective Tissue

Tendon

Connects Bone to Muscle
Strong, limited flexibility
Has White collagen filaments

Ligament

Connects Bone to Bone
More flexibility
Has Yellow elastin filaments

⚠ Exam Trap

Tendon = Bone ↔ Muscle (White collagen, less flexible) | Ligament = Bone ↔ Bone (Yellow elastin, more flexible). These two should not be confused.

🩸 Fluid Connective Tissue — Blood

Fluid filled vascular tissue
Transports: Nutrients, Gases (CO₂ & O₂), Hormones, Excretory materials

55%

Plasma (Fluid part)

45%

Cells (Solid part)

Plasma (55%)

Fluid matrix
90% Water
8% Protein
2% Minerals / Ions

Blood Cells (45%)

RBC: Red (Fe), Biconcave, Formed in Bone Marrow, Destroyed in Spleen ("Graveyard of RBC")
WBC: Neutrophil, Eosinophil, Basophil, Lymphocyte, Monocyte
Platelets: Blood clotting

⚠ Exam Trap

RBC formed in Bone Marrow, destroyed in Spleen ("Graveyard of RBC"). Lymph = Colourless liquid, RBC absent.

🧊 Original / Proper Connective Tissue

Adipose Tissue

Fat storage cells
Shock absorption + insulation regulation
Present in: Bone marrow, organs, below skin

Areolar Tissue

Loose connective tissue
Matrix: Jelly-like
Present below skin, in blank spaces of hollow organs, near muscles and blood vessels
Function: Repairing and filling of blank spaces

🦴 Skeletal Connective Tissue

Bone

Hard and stiff
Matrix hard due to: Calcium phosphate (chiefly hydroxyapatite) salts
Osteoblasts = bone-forming cells
Provides safety, support to soft organs; gives shape to body

Cartilage

Flexible and strong
Matrix: Chondrin protein, sugar, collagen and elastin fiber
Location: Joints, tip of nose, outer ear, trachea, throat

⚠ Exam Trap

Bone matrix = Calcium phosphate (hydroxyapatite) in a collagenous matrix. Cartilage = Flexible (Chondrin). Bone-forming cells = Osteoblasts. Stem cells present in Bone marrow.

💪 Muscular Tissue

Contains contractile protein: Actin and Myosin
Elongated, large contractile muscle fibres
Movement due to contraction and relaxation

Feature	Striated (Skeletal)	Smooth (Visceral)	Cardiac
Also called	Voluntary / Skeletal / Somatic muscles	Involuntary / Smooth / Visceral muscles	Heart muscles
Branching	Unbranched	Unbranched	Branched
Shape	Elongated, Cylindrical	Elongated, Spindle-shaped (narrow edges)	Branched, Cylindrical, Striated
Nucleus	Multi-nucleate	Uni-nucleate	Uni-nucleate
Bands (Striations)	Present	Absent	Present (but involuntary)
Control	Voluntary	Involuntary	Involuntary
Fatigue	Fast fatigue	Slow, fatigue resistant	Highly fatigue-resistant under normal conditions
Location / Special	Attached to skeleton (movement)	Walls of internal organs	Intercalated discs present

⚠ Exam Trap

Cardiac muscle is both striated and involuntary. Intercalated discs = only in cardiac muscle. Striated = Multi-nucleate. Smooth = Spindle-shaped, Uni-nucleate.

⚡ Quick Recall

Bands present: Striated + Cardiac. Bands absent: Smooth. Voluntary: only Striated. Branched: only Cardiac. Cardiac muscle is highly fatigue-resistant during normal lifelong rhythmic activity.

🧠 Nervous Tissue

Responsible for sensitivity and excitability
Coordinates between different organ systems
Neuron = Functional and Structural unit of nervous tissue
Neuron can be up to 1 m long
Most mature neurons are post-mitotic and generally do not divide
Present in brain, spinal cord and nerves
The outer nucleated cytoplasm of Schwann cells forms the neurilemma in peripheral nerve fibres

⚠ Exam Trap

Most mature neurons are post-mitotic. The outer Schwann-cell layer forms the neurilemma around many peripheral nerve fibres.

📌 Important Additional Facts

Eosine: Luminous red, acidic dye — stains cytoplasm, RBC, collagen and muscle fibres
Stem cells: Present in bone marrow
Schwann cells of nerve tissue = Neurilemma cells
Lymph = Colourless liquid, RBC absent

🧫 Chapter 05 — Tissue