Tissues – Class IX

 The human body and plants are made up of billions of cells. A single cell cannot perform all life activities efficiently, so groups of similar cells join together to perform specific functions. Such a group of cells is called a tissue.

---

1. Definition of Tissue

A tissue is a group of structurally and functionally similar cells that work together to perform a particular function.

• In unicellular organisms (e.g., Amoeba), one cell performs all activities.

• In multicellular organisms, division of labour exists through specialised tissues.

---

2. Types of Tissues

(A) Plant Tissues

Plant tissues are broadly classified into Meristematic and Permanent tissues.

(i) Meristematic Tissue

• Made up of actively dividing cells.

• Thin cell wall, dense cytoplasm, large nucleus, no vacuoles.

• Types:

  1. Apical meristem: At root and shoot tips; helps in growth in length.

  2. Intercalary meristem: At internodes, it helps in the growth of organs.

  3. Lateral meristem (cambium): Helps in thickness (girth).

(ii) Permanent Tissue

Cells lose the ability to divide, become specialised.

1. Simple Permanent Tissue: Made of one type of cell.

   • Parenchyma: Thin-walled, stores food, provides support.

   • Collenchyma: Provides flexibility and mechanical support.

   • Sclerenchyma: Thick, lignified walls provide hardness and strength.

2. Complex Permanent Tissue: Made of different types of cells.

   • Xylem: Conducts water and minerals (tracheids, vessels, xylem parenchyma, fibres).

   • Phloem: Conducts food (sieve tubes, companion cells, phloem parenchyma, fibres).

---

(B) Animal Tissues

Animal tissues are grouped into four basic types:

(i) Epithelial Tissue

• Forms covering/lining of body surfaces.

• Functions: protection, absorption, secretion.

• Types: Squamous, Cuboidal, Columnar, Ciliated, Glandular.

(ii) Connective Tissue

• Joins different tissues and provides support.

• Types:

  • Bone: Rigid support, framework.

  • Cartilage: Flexible support.

  • Ligaments: Connect bone to bone.

  • Tendons: Connect muscle to bone.

  • Areolar tissue: Fills space, binds skin to muscles.

  • Adipose tissue: Stores fat, insulates the body.

  • Blood: Transports gases, nutrients, hormones, and waste.

(iii) Muscular Tissue

• Responsible for movement.

• Types:

  1. Striated muscle: Voluntary, skeletal muscles.

  2. Unstriated muscle: Involuntary, smooth muscles.

  3. Cardiac muscle: Involuntary, heart muscles exhibit branched, rhythmic contraction.

(iv) Nervous Tissue

• Made up of neurons.

• Specialised to transmit messages in the form of electrical impulses.

• Consists of the cell body, axon, and dendrites.

---

3. Key Differences Between Plant and Animal Tissues

Feature	Plant Tissue	Animal Tissue
Growth	Localised (in meristems)	Uniform throughout the body
Cell wall	Present (cellulose)	Absent
Type of tissues	Simple (parenchyma, etc.)	More complex (nervous, muscle)
Movement	Absent	Present (muscular tissue)

---

4. Importance of Tissues

• Increases efficiency due to division of labour.

• Provides structural organisation.

• Enables multicellular organisms to perform complex functions.

• Essential for survival, growth, and specialisation.

---

5. Conclusion

Tissues form the fundamental basis of organisation in multicellular organisms. In plants, tissues help in growth, support, and transport, while in animals, they enable protection, movement, communication, and transportation. Understanding tissues lays the groundwork for advanced studies in biology, physiology, and medicine.