Topics in the Chapter
  • Introduction
  • Meristematic Tissues
  • Permanent Tissue
  • Simple permanent tissue
  • Difference between Parenchyma, Collenchyma and Sclerenchyma
  • Complex Permanent tissues
  • Xylem
  • Phloem
  • Epithelial Tissue
  • Connective Tissue
  • Fluid or vascular
  • Skeletal Tissue
  • connective Tissue
  • Aerolar tissue
  • Adipose tissue
  • Muscular tissue
  • Nervous tissue
Plant Tissues
  • A group of cells with similar structure or function forms a tissue.
  • Most plant tissues provide structural strength.
  • These tissues are often dead, requiring less maintenance while providing mechanical strength.
  • Plant tissues are categorized into:1.Meristematic tissues & 2. Permanent tissues

Meristematic Tissue

  • Living tissue made of thin-walled, compact cells capable of division and growth.

Features of Meristematic Tissues:

  • Thin cell walls made of cellulose.
  • No intercellular spaces (cells are tightly packed).
  • No vacuoles, but have dense cytoplasm and prominent nuclei.
  • Contain a large number of cell organelles.
  • In an active metabolic state, so they do not store food.
  • Found in actively growing regions such as root and shoot tips.
Classification of Meristematic Tissues

1. Based on Origin:

Primary (Promeristem):

  • Originates from the embryo meristem.
  • Leads to the primary growth (height, length) of plants.

Secondary Meristematic Tissues:

  • Formed by permanent tissues.
  • Increases the diameter of plants, contributing to secondary growth.

2. Based on Location:

Apical Meristem:

  • Located at the growing tips of stems and roots.
  • Leads to the elongation of stems and roots (primary growth).

Intercalary Meristem:

  • Located behind the apex.
  • Part of the apical meristem, left behind during growth.
  • Found at the base of leaves and internodes.
  • Responsible for increasing leaf length (examples: grass, bamboo, mint).

Lateral Meristem:

  • Also called secondary meristem.
  • Found along the sides of the plant's longitudinal axis.
  • Produces vascular tissues and causes an increase in girth.
  • Responsible for secondary growth.
Permanent Tissues Overview
  • Permanent tissues consist of cells that lose the ability to divide.
  • Cells have a definite shape, size, and thickness.
  • Permanent tissues can be living or dead.
  • They arise from meristematic tissues through cell division and differentiation (process where cells become specialized for specific functions).
  • These cells have permanent shape, size, and function.
Types of Permanent Tissues
  1. Simple Permanent Tissues
  2. Complex Permanent Tissues
Simple Permanent Tissues
  • Composed of cells that are similar in structure and function.
  • Divided into: 1. Protective Tissues, & 2. Supporting Tissues

1. Protective Tissues

  • These tissues serve a protective function.
  • Include Epidermis and Cork (Phellem).
(i) Epidermis
  • Forms a one-cell thick outer layer on plant organs (e.g., leaves, flowers, stems, roots).
  • Covered by cuticle (waterproof waxy layer made of cutin).
  • Thicker cuticle in xerophytes (plants in dry environments).
  • Stomata (small pores) present in the epidermis for gas exchange.
  • Guard cells (bean-shaped, with chloroplasts) surround the stomata.

Functions of Epidermis:

  • Protects the plant from water loss and infection.
  • Cuticle reduces transpiration (water evaporation) to prevent wilting.
  • Stomata allow gas exchange (photosynthesis, respiration).
  • Stomata help in transpiration.
(ii) Cork (Phellem)
  • Found in older stems and roots.
  • Composed of dead cells with thick walls.
  • Cell walls contain suberin (waxy material), making them impermeable to water and gases.
  • Cork cells lack protoplasm, filled with resins or tannins.

Functions of Cork:

  • Acts as a protective barrier, preventing desiccation and injury.
  • Cork is used commercially for its properties like lightness, toughness, elasticity, and compressibility.
  • Applications: insulation, shock absorption, sports goods (cricket balls, shuttlecocks).
2. Supporting Tissues
  • Provide mechanical support to the plant.
  • Types of Supporting Tissues:1. Parenchyma, 2. Collenchyma & 3. Sclerenchyma
(i) Parenchyma
  • Fundamental tissue found in plants.
  • Thin-walled, oval or spherical cells.
  • Cell walls composed of cellulose and pectin.
  • Contains a large central vacuole for food and water storage.
  • Primary function: storage of food.
  • Idioblasts are parenchyma cells that store resins, tannins, gums, oils.
  • Chlorenchyma (parenchyma with chloroplasts) performs photosynthesis (e.g., in mesophyll of leaves).
  • Aerenchyma (parenchyma with air spaces) in aquatic plants provides buoyancy.
  • Parenchyma provides turgidity (firmness) to cells.
(ii) Collenchyma
  • Living mechanical tissue.
  • Elongated cells with thickened corners (due to cellulose and pectin).
  • Provides flexibility to plant parts, allowing bending without breaking.
  • Found in herbaceous dicot stems and leaf margins.
  • Provides mechanical strength and elasticity to growing stems.
  • May contain a few chloroplasts.
(iii) Sclerenchyma
  • Strengthening tissue, composed of dead cells with thick lignified walls.
  • Lignin makes the cells waterproof.
  • No intercellular spaces.
  • Two types of sclerenchyma cells:
* Sclereids (stone cells):
  • Small cells with very thick walls and tiny lumens.
  • Found in drupes (e.g., mango, coconut), legume seeds.
* Fibers:
  • Long, narrow, and lignified cells.
  • Lumens are larger than in sclereids.
  • Used commercially in making ropes, mats, and textile fibers (e.g., jute, coir).

Difference between Parenchyma, Collenchyma, and Sclerenchyma

Complex Permanent Tissues: Xylem & Phloem

  • Complex permanent tissues have more than one cell type that work together.
  • Responsible for transport of organic materials, water, and minerals.
  • These tissues form the vascular bundles (conducting tissues).

Xylem

  • Also called wood, xylem is a vascular tissue responsible for water and mineral conduction.
Four types of elements:
  1. Tracheids: Elongated, dead cells involved in water conduction (found in gymnosperms).
  2. Vessels: Cylindrical tubes forming a continuous channel (found in angiosperms).
  3. Xylem Parenchyma: Stores starch (food).
  4. Xylem Sclerenchyma: Non-living fibres providing mechanical support.
  • Annual xylem rings in tree trunks help determine the age of the tree.

Phloem

  • Phloem conducts food (sugars) in both directions within the plant.
Four types of elements:
  1. Sieve Tubes: Elongated cells with sieve plates for food conduction.
  2. Companion Cells: Assist sieve tubes with metabolic activities; sister cells to sieve tubes.
  3. Phloem Fibres: Provide mechanical support.
  4. Phloem Parenchyma: Stores food and aids in radial conduction.
  • In xylem, movement is unidirectional, but in phloem, it is bidirectional.
Comparison Between Xylem and Phloem
Animal Tissues: Overview
  • Tissues are groups of cells that perform specific functions.
  • Blood and muscles are examples of tissues in our body.
  • Types of Animal Tissues: 1. Epithelial tissue, 2.Connective tissue, 3.Muscular tissue, 4.Nervous tissue

Epithelial Tissue

  • Epithelial tissue: Covers body surfaces, lines cavities, and forms glands.
Characteristics:
  • Cells are tightly packed together.
  • Tissue rests on a non-cellular basement membrane.
  • Blood vessels are absent and it is non-nervous.
  • Mainly serves a protective function.

Types of Epithelial Tissue

1. Squamous Epithelium (also called pavement epithelium)

  • Cells arranged like tiles.
  • Forms delicate linings of mouth, nose, alveoli, and skin.
  • Provides protection, especially in stratified squamous epithelium for preventing wear and tear.

2. Cubical Epithelium

  • Cube-shaped cells.
  • Found in kidney tubules, thyroid vesicles, and glands (salivary, sweat).
  • Functions include absorption, excretion, secretion, and mechanical support.

3. Columnar Epithelium

  • Pillar-like cells, lining organs like stomach and small intestine.
  • Contains microvilli for better absorption.

4. Ciliated Epithelium

  • Cells may be cubical or columnar with hair-like projections called cilia.
  • Helps move ova in the fallopian tube.
Connective Tissue: Overview
  • Connective tissue: Widely spaced cells embedded in an intercellular matrix.
  • Matrix composition determines the tissue's function.
  • Fibres: Contains white and yellow fibres.
  • Primary function: Provides support and helps keep organs in place.
 Types of Connective Tissue

1. Fluid or Vascular Tissue (blood and lymph)

Blood:

  • Matrix: Fluid matrix is called plasma.
  • Functions: Transports nutrients, gases, excretory products, and hormones.

Plasma:

  • Makes up 55% of blood.
  • Consists of 90-91% water, 7% proteins (Albumin, fibrinogen, globulin), and 0.9% inorganic salts.

Corpuscles:

  • Make up 45% of blood.
  • Red Blood Cells (RBCs): Contain haemoglobin, a red pigment that helps in oxygen transportation.
  • White Blood Cells (WBCs): Also called the "soldiers of the body."
  • Function: Protects the body by engulfing bacteria and foreign particles.
  • Types of WBCs: Monocytes, Lymphocytes, Basophils, Neutrophils, Eosinophils.
  • Blood Platelets (Thrombocytes):
  • Spindle-shaped cells involved in blood clotting.

2. Skeletal Tissue

  • Hard connective tissue that forms the body’s supportive framework.
  • Types: Bone and Cartilage.

Bone:

  • Matrix: Hard due to calcium phosphate, CaCO3 (60-70%), and a protein called ossein.
  • Bone cells (osteoblasts): Embedded in the hard matrix.
  • Lamellae: Concentric layers of matrix around a central canal.
  • Marrow cavity: Hollow space in long bones filled with bone marrow.

Cartilage:

  • Elastic and less hard compared to bones.
  • Protein chondrin provides elasticity.
  • Chondroblasts: Widely spaced cells in a matrix reinforced by fibres.
  • Locations: Joints, nose, ear, trachea, larynx.
  • Provides flexibility and tensile strength.

3. Fibrous Connective Tissue

  • Divided into Yellow fibrous connective tissue and White fibrous connective tissue.

Yellow fibrous connective tissue:

  • Elastic due to yellow fibres in the matrix.
  • Forms ligaments that connect bone to bone.

White fibrous connective tissue:

  • Contains white fibres with little matrix.
  • Forms tendons that attach muscles to bones.

4. Areolar Tissue

  • The most widely distributed connective tissue in the body.
  • Fills spaces inside organs.
  • Found between skin and muscles, around blood vessels, nerves, and in bone marrow.

5. Adipose Tissue

  • Oval/round cells filled with fat globules called adipocytes.
  • Locations: Found beneath the skin, around the heart, brain, and under eyeballs.
  • Functions: Acts as an insulator and prevents heat loss.

Muscular Tissue: Overview

  • Muscular tissues enable movement in the body.
  • Made up of long, fibre-like cells known as muscle fibres.
  • These fibres can contract and relax.
  • Types of Muscular Tissue:1.Striated muscles, 2.Cardiac muscle fibres, 3.Non-striated muscles

Types of Muscular Tissue

1. Striated Muscles (Voluntary Muscles)

  • Also called voluntary muscles since they are controlled consciously.
  • Muscle fibres are multinucleated and unbranched.
  • Enclosed by a thin membrane called sarcolemma.
  • Cytoplasm of these fibres is called sarcoplasm.
  • These muscles tire easily and require rest.

2. Cardiac Muscle Fibres

  • Involuntary muscles found only in the heart walls.
  • Structure is between striated and non-striated muscles.
  • Uninucleated and branched fibres, connected by intercalated discs.
  • Responsible for rhythmic contraction and relaxation throughout life.

3. Non-striated Muscles (Smooth Muscles)

  • Also called involuntary muscles.
  • Uninucleated, spindle-shaped fibres.
  • Not enclosed by a membrane, but fibres join together in bundles.
  • Found in organs like the stomach, intestine, urinary bladder, bronchi, and iris of the eye.
  • Responsible for peristaltic movements in the alimentary canal.
Nervous Tissue: Overview
  • Specialized tissue enabling animals to perceive and respond to stimuli.
  • The functional unit is the neuron or nerve cell.
  • The cell body is called cyton and is covered by a plasma membrane.
Neuron Structure

1. Dendron:

  • Short, hair-like extensions from the cyton.
  • Subdivided into dendrites.

2. Axon:

  • A long, cylindrical process extending from the neuron, with fine branches at the end.
  • Covered by a sheath.
  • Transmits impulses between neurons via electrochemical waves.
  • The point where an axon of one neuron connects closely to the dendrites of another neuron is called a synapse.