Class 9 Science – Chapter: Tissues

ðŸ”ķ Introduction to Tissues

  • Tissue: A group of cells having a common origin, structure, and function.

  • In multicellular organisms, tissues enable division of labor.

ðŸ”ķ Types of Tissues

Tissues are broadly classified into:

  1. Plant Tissues

  2. Animal Tissues

ðŸŠī PLANT TISSUES

🔷 1. Meristematic Tissue (Actively Dividing Cells)

Type Location Function
Apical Meristem Tips of roots and shoots Growth in length
Lateral Meristem Sides of stem and root Growth in thickness (girth)
Intercalary Meristem At internodes or stem base Growth in between nodes

Characteristics:

  • Actively dividing

  • Small, thin-walled cells

  • Dense cytoplasm and prominent nuclei

  • No vacuoles (or very small)

🔷 2. Permanent Tissue (Non-Dividing Cells)

Formed from meristematic tissue after differentiation.

ðŸ”đ A. Simple Permanent Tissue

Type Structure & Features Function
Parenchyma Living cells, thin-walled, loosely packed Storage, photosynthesis
Collenchyma Living, elongated, thickened at corners Flexibility and support
Sclerenchyma Dead, thick-walled, no intercellular space Strength and rigidity

Special type: Chlorenchyma (photosynthetic parenchyma), Aerenchyma (air spaces in aquatic plants)

ðŸ”đ B. Complex Permanent Tissue

Transports food and water.

Tissue Elements Function
Xylem Tracheids, vessels, xylem parenchyma, xylem fibers Transports water & minerals
Phloem Sieve tubes, companion cells, phloem parenchyma, phloem fibers Transports food

🧍 ANIMAL TISSUES

🔷 1. Epithelial Tissue (Covering/Protective Tissue)

Type Features & Location Function
Squamous Flat cells, lines blood vessels, alveoli Protection, diffusion
Cuboidal Cube-shaped, lines kidney tubules, glands Secretion, absorption
Columnar Tall cells, lines intestine, respiratory tract Absorption, secretion
Ciliated Columnar with cilia, in respiratory tract Movement of mucus
Glandular Specialized for secretion, forms glands Secretes enzymes, hormones

🔷 2. Connective Tissue (Joins, Supports, Protects)

 

  • A type of animal tissue that connects, supports, binds, or separates other tissues and organs.

  • Widely spaced cells in an intercellular matrix (can be liquid, jelly-like, or solid).

  • Provides structural and functional support.

ðŸ”ķ Functions of Connective Tissue

  • Binding organs together.

  • Support and protection of body parts.

  • Transport of substances (like oxygen and nutrients).

  • Storage of fat.

  • Immunity (white blood cells in blood).

ðŸ”ķ Types of Connective Tissue

Connective tissues are classified into three main categories:

1. Loose Connective Tissue

2. Dense Connective Tissue

3. Specialized Connective Tissue

🔷 1. Loose Connective Tissue

Type Structure & Features Function Example
Areolar Loose matrix, fibroblasts, macrophages, collagen & elastin Binds skin to muscles; fills spaces Under skin, around organs
Adipose Fat-filled cells (adipocytes) Insulation, energy storage, shock absorber Below skin, around kidneys

🔷 2. Dense Connective Tissue

  • Matrix has densely packed collagen fibers for strength.

Type Structure Function Example
Tendons Tough, inelastic, made of collagen Connect muscle to bone Achilles tendon
Ligaments Elastic, made of collagen + elastin Connect bone to bone Knee ligament

✅ Tendons = Muscle to Bone
✅ Ligaments = Bone to Bone

🔷 3. Specialized Connective Tissue

Type Matrix Type Function Location/Example
Cartilage Flexible (chondrin) Smooth surface, reduces friction, flexible Nose, ear, trachea, joints
Bone Hard (calcium + collagen) Support, protection, RBC production Skeleton
Blood Liquid (plasma) Transport gases, nutrients, hormones Throughout body (blood vessels)
Lymph Clear, similar to plasma Immunity, returns leaked fluid to blood Lymphatic vessels

ðŸĐļ Components of Blood

Component Function
RBC (Red Blood Cells) Transport oxygen using hemoglobin
WBC (White Blood Cells) Fight infections (immunity)
Platelets Help in blood clotting
Plasma Fluid medium, transports nutrients, waste

📌 Summary Table: Types of Connective Tissue

Category Tissue Matrix Type Main Function
Loose Connective Tissue Areolar Jelly-like Binding, flexibility
  Adipose Fat Insulation, energy storage
Dense Connective Tissue Tendons Collagen fibers Connect muscle to bone
  Ligaments Elastic fibers Connect bone to bone
Specialized Connective Cartilage Chondrin (flexible) Smooth movement, flexibility
  Bone Calcium salts Support, protection, structure
  Blood Plasma (liquid) Transport, immunity
  Lymph Plasma-like fluid Drainage and immune function

📌 Key Characteristics of Connective Tissue

  • Cells are not closely packed; embedded in matrix.

  • Matrix decides the nature of tissue (solid in bone, liquid in blood).

  • Highly vascular (except cartilage).

  • Provides support, strength, protection, and transportation.

Would you like:

  • Labeled diagrams of connective tissues?

  • A summary PDF or printable worksheet?

  • A comparison chart with other tissues?

Type Features & Function Example
Areolar Loose, connects tissues and organs Between skin and muscles
Adipose Stores fat, acts as insulator Below skin
Tendons Connect muscles to bones Strong, flexible
Ligaments Connect bones to bones Elastic, support joints
Cartilage Flexible, smooth, less vascular Ear, nose, trachea
Bone Hard, calcium-rich, supports body Skeleton
Blood Fluid connective tissue, transports nutrients, O2 Blood vessels

🔷 3. Muscular Tissue

  • The muscular system is responsible for movement, posture, and locomotion in animals, including humans.

  • It consists of muscles and associated structures (like tendons).

  • Muscles work by contraction and relaxation.

ðŸ”ķ Functions of the Muscular System

  1. Movement – voluntary (e.g., walking) and involuntary (e.g., heartbeat).

  2. Posture and body support.

  3. Circulation – cardiac muscles pump blood.

  4. Digestion – smooth muscles move food.

  5. Heat production – through muscle activity (e.g., shivering).

ðŸ”ķ Types of Muscles in the Human Body

Muscle Type Structure Location Control Function
Skeletal Muscle Long, cylindrical, striated, multinucleated Attached to bones Voluntary Movement of body parts
Smooth Muscle Spindle-shaped, non-striated, uninucleated Walls of internal organs (stomach, intestine, blood vessels) Involuntary Movement of internal organs
Cardiac Muscle Branched, striated, uninucleated Heart Involuntary Pumps blood throughout the body

🔷 1. Skeletal Muscles (Voluntary Muscles)

  • Attached to the skeleton via tendons.

  • Also called striated muscles due to banded appearance.

  • Work under conscious control.

  • Fatigue quickly.

  • Examples: Biceps, triceps, quadriceps.

🔷 2. Smooth Muscles (Involuntary Muscles)

  • Found in walls of internal organs (except heart).

  • Also called non-striated or unstriated muscles.

  • Work automatically (involuntary).

  • Do not fatigue easily.

  • Examples: Muscles in stomach, intestines, urinary bladder.

🔷 3. Cardiac Muscles (Heart Muscles)

  • Found only in the heart.

  • Involuntary but striated like skeletal muscle.

  • Highly resistant to fatigue.

  • Rhythmic and continuous contractions.

  • Specialized for pumping blood.

ðŸ”ķ Muscular Movements

  • Flexion – Bending a joint (e.g., bending elbow).

  • Extension – Straightening a joint.

  • Abduction – Moving a limb away from the body.

  • Adduction – Moving a limb toward the body.

ðŸ”ķ Properties of Muscles

Property Description
Contractility Ability to shorten forcefully
Extensibility Ability to be stretched
Elasticity Ability to return to original shape after stretch
Excitability Responds to stimulation (nerve impulse)

ðŸ§Đ Fun Facts

  • Muscles make up 40–50% of body weight.

  • The strongest muscle (by size) is the masseter (jaw muscle).

  • The largest muscle is the gluteus maximus.

  • Cardiac muscle contracts about 70–80 times per minute (over 100,000 times a day!).

📌 Summary Table

Feature Skeletal Muscle Smooth Muscle Cardiac Muscle
Control Voluntary Involuntary Involuntary
Appearance Striated Non-striated Striated
Nuclei Multinucleated One nucleus One nucleus
Location Bones Internal organs Heart
Fatigue Fatigues easily Slow to fatigue Never fatigues
Type Structure and Control Location Function
Striated Long, cylindrical, voluntary Attached to bones Body movement
Smooth Spindle-shaped, involuntary Internal organs (intestine) Movement of food, urine
Cardiac Branched, involuntary Heart Pumping blood

🔷 4. Nervous Tissue (Control and Coordination)

  • Made of neurons and neuroglial cells.

  • Neuron has: Cell body, axon, and dendrites.

Functions:

  • Receives stimuli and transmits messages.

  • Coordinates body functions.

ðŸ”ķ Summary Table: Differences Between Plant and Animal Tissues

Feature Plant Tissue Animal Tissue
Growth Limited to meristems Uniform throughout
Types Simple and complex More diverse
Function Support, transport, photosynthesis Movement, coordination, support
Cell Wall Present Absent
Vascular Tissue Present (xylem, phloem) Blood is fluid connective tissue

📌 Key Points to Remember

  • Tissues are important for efficient body functioning.

  • Plants have simple organization; animals have complex tissue specialization.

  • Study diagrams of:

    • Meristematic tissue

    • Simple and complex tissues (plant)

    • Types of epithelium, muscle tissue, neuron (animal)

 

Hand written Notes Of CELL: The Fundamental unit of Life