Lecture: Tissues in Biology

Introduction

• Lecturer: Samriddhi from PhysicsWala foundation.
• Chapter Focus: Key points important for exams from NCERT.

Overview of Tissues

• Last Chapter Recap: Studied about cells, parts, and functions.
• Current Chapter: Focus on tissues.
• Exam Focus: Locations and functions of tissues in plants and animals.

Plant Tissues

Types of Plant Tissues

1. Meristematic Tissue: Continuous cell division.

   • Apical Meristem: Present at tips (shoot and root), increases length.
   • Lateral Meristem: Present in stem's circumference, increases thickness.
   • Intercalary Meristem: Located near nodes, increases length between nodes.
   • Characteristics: Small, thin-walled cells, no vacuole, densely packed.

2. Permanent Tissue: Matured meristematic cells, ceased dividing.

   • Types: Simple and Complex.

Simple Permanent Tissues

1. Parenchyma: Most common, functions for storage and photosynthesis (chlorenchyma).
2. Collenchyma: Provides flexibility, thickened at corners.
3. Sclerenchyma: Hard and rigid, dead cells, provides mechanical support.

Complex Permanent Tissues

1. Xylem: Conducts water and minerals from roots to plant. Components: tracheids, vessels, fibers, parenchyma.
2. Phloem: Conducts food from leaves. Components: sieve tubes, companion cells, fibers, parenchyma.

Protective Tissues

1. Epidermis: Outermost layer, provides protection, cuticle layer reduces water loss.
2. Cork: Found in outer bark, dead cells, impregnated with suberin, prevents water loss.

Animal Tissues

Types of Animal Tissues

1. Epithelial Tissues: Covers and protects body organs.
2. Connective Tissues: Supports, binds body structures.
3. Muscular Tissues: Enables movement.
4. Nervous Tissues: Receives, transmits nerve impulses.

Epithelial Tissues

• Structure: Single (simple) or multiple (stratified) layers. Sits on basement membrane.
• Types: Squamous, Cuboidal, Columnar, Ciliated.
  • Squamous: Flat cells, found in lungs, blood vessels.
  • Cuboidal: Cube-shaped, found in kidneys, glands.
  • Columnar: Tall, pillar-like cells, found in digestive tract.
  • Ciliated: Hair-like structures, found in respiratory tract.

Muscular Tissues

1. Striated (Skeletal): Voluntary, attached to bones, striated appearance.
2. Smooth Muscles: Involuntary, found in walls of internal organs, spindle-shaped.
3. Cardiac Muscles: Involuntary, found in heart, striated but branched.

Connective Tissues

• Types: Blood, Bone, Cartilage, Tendons, Ligaments, Areolar, Adipose.
  • Blood: Fluid connective tissue, transports substances.
  • Bone: Supports, protects body parts.
  • Cartilage: Flexible, found in ears, nose, joints.
  • Tendons: Connect muscles to bones.
  • Ligaments: Connect bones to bones.
  • Areolar: Fills spaces between organs.
  • Adipose: Stores fat.

Nervous Tissues

• Components: Neurons (nerve cells).
• Function: Transmits nerve impulses.
• Structure: Cell body, dendrites, axon, myelin sheath.

Conclusion

• Summary: Detailed study of plant and animal tissues, their structure, types, and functions with focus on exam-relevant points.
• Encouragement: Revise notes, underline in NCERT, and ensure conceptual clarity.

Important Points to Remember

• Key definitions, functions, and examples of each tissue type.

Homework

• Understand and write the properties, functions, and differences of various tissues discussed.