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Class 9 Science · Chapter 3 · Part 2 of 2

Tissues in Action

Animal Tissues — Epithelial, Connective, Muscular, Nervous · Joints · Skeletal System

🛡️ Epithelial
🩸 Connective
💪 Muscular
🧠 Nervous
🦴 Skeletal

⬅️ Part 1 covered: Plant Tissues

Meristematic Tissues, Permanent Tissues, Xylem & Phloem, Tissue Systems

PART 2
This part covers: Animal Tissues (Epithelial, Connective, Muscular, Nervous) → Musculoskeletal System → Joints → Skeletal System → Summary → Final Quiz.
📌 Jump to Section
Animal Tissues
Epithelial
Connective
Muscular
Nervous
Joints
Skeletal System
Summary
Definitions
Exam FAQs
Final Quiz

🐾 3.3 Animal Tissues

Like plants, animal cells group together and specialise in performing different functions. Animal tissues are mainly of four types:

• 🛡️ Epithelial tissue — Protection and lining
• 🩸 Connective tissue — Connects and supports
• 💪 Muscular tissue — Movement
• 🧠 Nervous tissue — Communication and control

🛡️ 3.3.1 Epithelial Tissue — Structure and Functions

📖 Definition

Epithelial tissue forms the outer covering of the body (skin) and lines internal organs such as the mouth, lungs, blood vessels, and intestine. Composed of closely packed cells with very little space between them — prevents entry of germs, reduces water loss, and helps in absorption, secretion, and movement of substances.

Function	Structure	Location
Exchange — rapid diffusion of liquids and gases	Single layer of thin, flat cells	Blood vessels, lungs
Protection — against injury, friction, microbes	Many layers; outer cells flat and tightly packed	Skin, mouth, oesophagus
Secretion — mucus, enzymes, hormones, sweat, saliva	Cells specialised for secretion; cuboidal or columnar	Salivary/sweat glands, stomach lining
Sensory — smell, taste, sound, balance	Receptor cells with hair-like cilia	Nostrils, taste buds, inner ear
Absorption — uptake of nutrients, water	Tall, pillar-like cells with microvilli	Lining of small intestine

🎯 Exam Point

Epithelial tissues lining internal organs are usually only one or a few cells thick — to allow quick exchange of materials across them. Thinner layer = faster diffusion.

🩸 3.3.2 Connective Tissue — Connects and Supports

📖 Definition

Connective tissue — A tissue that connects and supports other tissues. The key characteristic is the matrix — a surrounding substance whose nature determines the properties (fluid in blood, solid in bone).

🩸
Blood
Fluid Connective Tissue
Matrix is watery, soft (plasma). Contains RBCs (O₂ transport), WBCs (immunity), Platelets (clotting). Plasma = 55%, formed elements = 45%.
🦴
Bone
Rigid Connective Tissue
Matrix is hard, solid, rigid — has calcium and phosphorus compounds. Gives strength and rigidity, supports body.
👂
Cartilage
Flexible Connective Tissue
Matrix is soft, jelly-like. Provides flexibility and cushioning for shock absorption. Found in ear, nose, between vertebrae.
💛
Tendon
Muscle → Bone
Tough connective tissue. Connects muscle to bone. Transmits force from contracting muscle to bone, causing movement.
🟣
Ligament
Bone → Bone
Connects bone to bone. Provides stability, limits movement, prevents dislocation at joints.
🧪 Activity 3.2 — Blood and Its Components
Cut on skin

Red blood oozes; clot forms → Platelets cause clotting.

Skin infection

Red, swollen, fever → WBCs collect at infected area causing inflammation/pus.

Exercise

Faster breathing, red face → muscles need more O₂ → blood flow increases.

Red colour of blood

Due to haemoglobin (iron-rich protein in RBCs). RBCs live ~4 months.

🔩 Bone Marrow Transplant — Ready to Go Beyond

Stem cells in bone marrow can divide and make new blood cells. In a bone marrow transplant, stem cells from a healthy person are given to patients with blood cancers like Leukemia or disorders like Thalassemia.

✅ Check Your Understanding — Epithelial & Connective Tissue
Q1. Tendons connect:
ABone to bone
BMuscle to bone
CMuscle to muscle
DNerve to bone
Q2. Blood is a connective tissue because its matrix is:
AWatery and fluid (plasma)
BHard and rigid
CSoft and jelly-like
DMade of lignin
Q3. Epithelial tissue lining the small intestine is adapted for:
AProtection only
BAbsorption of nutrients
CSensory function
DForce transmission
📋 Answer Key
Q1B — Muscle to bone — Tendons connect muscles to bones, transmitting force. Ligaments connect bone to bone.
Q2A — Watery fluid (plasma) — Blood’s matrix is plasma. Bone’s matrix is hard (calcium/phosphorus). Cartilage’s matrix is jelly-like.
Q3B — Absorption — Tall, pillar-like cells with hair-like structures (microvilli) in the small intestine lining efficiently absorb nutrients.

💪 3.3.3 Muscular Tissue — Controls Movement

🦾 Skeletal (Striated) Muscle

• Attached to skeleton
• Voluntary movements (running, writing)
• Cells: long, cylindrical, unbranched, multinucleate
• Shows striations

🫀 Smooth Muscle

• Found in stomach, intestines
• Involuntary movements
• Cells: spindle-shaped, single nucleus
• No striations

❤️ Cardiac Muscle

• Found only in heart
• Involuntary, rhythmic
• Cells: cylindrical, branched, single nucleus
• Faint striations, never fatigues

Feature	Skeletal	Smooth	Cardiac
Control	Voluntary	Involuntary	Involuntary
Shape	Long cylindrical	Spindle-shaped	Cylindrical, branched
Nucleus	Multinucleate	Single	Single
Striations	Present	Absent	Faint

🧠 3.3.4 Nervous Tissue — Sense, Communicate, Respond

📖 Definition

Nervous tissue forms the body’s control and coordination network. Cells = neurons — specialised to receive, process and transmit messages. The brain is the control centre.

Structure of a Neuron — Three Main Parts

• Cell body — Contains nucleus; controls cell activities.
• Dendrites — Receive signals from other neurons.
• Axon — Long fibre that carries messages away to axon terminals, which transmit to other cells.

Example: During exercise, the brain signals the heart (via nervous tissue) to beat faster, meeting increased O₂ demand.

⭐ Important Fact

Muscles (voluntary and involuntary) cannot function independently — they receive instructions from nervous tissue. The musculoskeletal system functions under the control of the nervous system.

✅ Check Your Understanding — Muscular & Nervous Tissue
Q4. Cardiac muscle differs from skeletal muscle because it is:
AVoluntary and striated
BSpindle-shaped, non-striated
CInvoluntary, branched, single nucleus
DMultinucleate, unbranched
Q5. Which part of a neuron receives signals from other neurons?
AAxon
BDendrites
CCell body
DAxon terminals
Q6. Which type of movement is controlled by skeletal muscles?
AHeartbeat
BFood movement in intestine
CRunning and writing
DAutomatic breathing
📋 Answer Key
Q4C — Involuntary, branched, single nucleus — Cardiac muscle is involuntary (like smooth) but cylindrical and branched (unlike smooth), with faint striations.
Q5B — Dendrites — Dendrites receive signals. Axon carries messages away from the cell body.
Q6C — Running and writing — Skeletal muscles are voluntary. Heartbeat and digestion are involuntary (cardiac/smooth muscles).

🦴 3.4 & 3.5 Musculoskeletal System & Types of Joints

The musculoskeletal system is made up of bones, muscles, joints, cartilage, tendons and ligaments. Helps us stand upright, move, maintain posture, protect organs.

• Muscles pull on bones via tendons to produce movement at joints.
• Adult human skeleton = about 12–15% of body weight.
• Adult males: ~40–50% muscle mass; adult females: ~30–40%.

📖 Definition — Joint

Joint — A junction between two or more bones. Joints allow movement but cannot move bones on their own (muscles cause movement).

⚽
Ball & Socket
📍 Shoulder, Hip
Rounded bone end fits into a hollow. Allows forward, backward, sideways, circular movement — maximum range.
🚪
Hinge Joint
📍 Elbow, Knee
Like a door hinge — bends/straightens in one direction only. Kneecap protects the knee joint.
🔄
Pivot Joint
📍 Neck
Skull connects to backbone here — allows head to move side to side, like a doorknob.
🔒
Fixed Joint
📍 Skull bones
Bones cannot move. Skull bones joined by fixed joints — protect brain, eyes, ears.

✅ Check Your Understanding — Joints
Q7. Which type of joint is present at the shoulder?
ABall and socket joint
BHinge joint
CPivot joint
DFixed joint
Q8. The skull bones are connected by:
AHinge joints
BPivot joints
CBall and socket joints
DFixed joints
📋 Answer Key
Q7A — Ball and socket joint — Allows maximum movement in all directions at the shoulder.
Q8D — Fixed joints — Skull bones cannot move; fixed joints keep the brain safe even when the body moves.

🦷 3.6 Skeletal System

The skeletal system consists of a framework of bones providing strength and protecting internal organs. Includes skull, vertebral column, and rib cage.

• Vertebral column (backbone/spine) — Series of small bones called vertebrae. Supports body, helps stand upright. Cartilage disc between vertebrae acts as cushion.
• Rib cage — 12 pairs of ribs. Protects heart and lungs. Attached to spine (back) and sternum (front) by flexible cartilage. Expands/contracts during breathing.
• Skull — Hard case of flat bones joined by fixed joints. Protects brain, eyes, ears.

🌏 Bridging Science and Society — Yoga

Yoga includes physical postures, breathing, and meditation. Improves flexibility, posture, breathing; reduces stress; helps prevent lifestyle diseases. 21st June = International Yoga Day. Maintaining correct posture, nutrition, exercise and yoga keeps bones strong, muscles fit, joints flexible.

🥕
F. C. Steward (1958) — Totipotency in Plants

Showed single cells from vascular phloem of carrot can regenerate whole plants. Phloem cells dedifferentiated → undifferentiated mass → redifferentiated → complete plant. Proved totipotency — ability of mature plant cells to develop into a new plant under specific conditions.

🔩 Crown Gall Disease

Crown gall disease causes tumour-like swellings on stems due to uncontrolled cell division, caused by Agrobacterium tumefaciens. Scientists studied how this bacterium transfers genetic material into plant cells — now used in plant tissue culture and genetic engineering to introduce useful genes for improved crops.

📋 Chapter Summary — Animal Tissues

🛡️EpithelialOuter covering + internal lining. Types: Exchange, Protection, Secretion, Sensory, Absorption.
🩸ConnectiveBlood (fluid), Bone (rigid), Cartilage (jelly-like), Tendon (muscle→bone), Ligament (bone→bone).
💪MuscularSkeletal (voluntary, striated). Smooth (involuntary, no striations). Cardiac (involuntary, branched).
🧠NervousNeurons = cell body + dendrites + axon. Brain = control centre.
🔗JointsBall & socket (shoulder/hip). Hinge (elbow/knee). Pivot (neck). Fixed (skull).
🦴Skeletal SystemSkull, vertebrae, rib cage (12 pairs). Skeleton = 12-15% of body weight.

🔑 Keywords — Animal Tissues

Epithelial TissueConnective TissueMatrixBloodBoneCartilageTendonLigamentRBCsWBCsPlateletsHaemoglobinSkeletal MuscleSmooth MuscleCardiac MuscleMuscle FibreStriatedVoluntaryInvoluntaryNervous TissueNeuronDendritesAxonMusculoskeletal SystemJointBall and SocketHinge JointPivot JointFixed JointVertebraeRib CageSternumTotipotencyDedifferentiationRedifferentiation

📖 Important Definitions — Animal Tissues

Connective TissueA tissue that connects and supports other tissues. Cells surrounded by a matrix. Includes blood, bone, cartilage, tendons, ligaments.
TendonTough connective tissue connecting muscle to bone. Transmits force from contracting muscle to bone, causing movement at a joint.
LigamentConnective tissue connecting bone to bone. Provides stability at joints, limits excessive movement, prevents dislocation.
NeuronStructural/functional unit of nervous tissue. Specialised to receive, process and transmit messages. Has cell body, dendrites, axon.
JointA junction between two or more bones. Allows movement. Types: ball and socket, hinge, pivot, fixed.
TotipotencyAbility of mature plant cells to dedifferentiate, divide, and redifferentiate into a complete new plant under specific conditions. Demonstrated by F. C. Steward (1958).

❓ Frequently Asked Exam Concepts — Animal Tissues

What is the difference between tendon and ligament? ▶
Tendon connects muscle to bone. When a muscle contracts, the tendon transmits this force to the bone, causing movement at a joint. Ligament connects bone to bone. It provides stability, limits excessive movement, and prevents dislocation. Both are connective tissues.
What is the difference between skeletal, smooth and cardiac muscles? ▶
Skeletal muscles: voluntary, attached to skeleton, long cylindrical unbranched fibres, multinucleate, striated. Smooth muscles: involuntary, found in stomach/intestines, spindle-shaped, single nucleus, no striations. Cardiac muscles: involuntary, found only in heart, cylindrical branched, single nucleus, faint striations, never fatigue.
Why are some body joints (like skull) fixed while others (like shoulder) allow free movement? ▶
Fixed joints (skull) protect delicate organs like the brain — movement here would be dangerous, so the bones are joined rigidly. Ball and socket joints (shoulder, hip) need to allow a wide range of movement for activities like throwing, running, and reaching, so the rounded bone end fits loosely into a hollow socket, permitting movement in many directions.
Why is epithelial tissue lining internal organs usually thin? ▶
Epithelial tissues lining internal organs like blood vessels and lungs need to allow rapid diffusion of gases and liquids (like oxygen and carbon dioxide). A thin layer (often single-celled) reduces the distance substances must travel, allowing fast and efficient exchange — essential for processes like gas exchange in the lungs.

🏆 Final Practice Quiz
15 Mixed MCQs · Full Chapter Coverage (Plant + Animal Tissues)
Q1 — A tissue is defined as:
AA single specialised cell
BGroup of similar cells performing a specific function
CA group of organs
DAn organ system
Q2 — Which meristematic tissue is responsible for growth in length?
AApical meristem
BLateral meristem
CIntercalary meristem
DGround meristem
Q3 — Which simple tissue provides support and flexibility to stems via pectin?
AParenchyma
BCollenchyma
CSclerenchyma
DXylem
Q4 — Sieve tubes in phloem transport:
AWater and minerals
BFood (sugars)
COxygen only
DHormones only
Q5 — Epithelial tissue lining blood vessels is adapted for:
ARapid diffusion
BMechanical protection
CSecretion of enzymes
DSensory function
Q6 — The matrix of bone is made hard by:
APectin
BLignin
CCalcium and phosphorus
DCellulose
Q7 — Platelets in blood are responsible for:
ACarrying oxygen
BFighting infection
CBlood clotting
DTransporting hormones
Q8 — Smooth muscle cells are:
AMultinucleate and striated
BBranched with faint striations
CSpindle-shaped, single nucleus, no striations
DLong cylindrical and unbranched
Q9 — Which part of the neuron carries messages away from the cell body?
ADendrites
BAxon
CCell body
DNucleus
Q10 — The neck joint allowing side-to-side movement of head is a:
ABall and socket
BHinge joint
CPivot joint
DFixed joint
Q11 — F. C. Steward’s carrot experiment proved:
ACell division occurs only in meristems
BMature plant cells can develop into a complete plant (totipotency)
CAnimal cells can regenerate full organisms
DPhloem transports water
Q12 — Which tissue is responsible for increase in girth of a tree trunk?
AApical meristem
BLateral meristem
CIntercalary meristem
DPhloem
Q13 — Which is a COMPLEX permanent tissue?
AParenchyma
BCollenchyma
CXylem
DSclerenchyma
Q14 — Which connects bone to bone and prevents dislocation?
ATendon
BLigament
CCartilage
DBlood
Q15 — Sclerenchyma cells have thick walls due to:
APectin
BLignin
CCellulose only
DStarch
Your Final Quiz Score
0/15
📋 Final Quiz — Answer Key with Explanations
Q1B — A tissue is a group of similar cells performing a specific function together.
Q2A — Apical meristem — Located at root/shoot tips, responsible for growth in length.
Q3B — Collenchyma — Pectin-thickened corners give flexibility, allowing bending without breaking.
Q4B — Food (sugars) — Sieve tubes transport food in both directions; xylem transports water upward.
Q5A — Rapid diffusion — Single thin flat cells allow quick exchange of gases/liquids.
Q6C — Calcium and phosphorus — Gives bone its rigidity. Cartilage matrix is jelly-like (no minerals).
Q7C — Blood clotting — Platelets aggregate at injury sites. RBCs carry oxygen; WBCs fight infection.
Q8C — Spindle-shaped, single nucleus, no striations — Characteristic of smooth muscle (involuntary).
Q9B — Axon — Carries messages from cell body to axon terminals. Dendrites receive signals.
Q10C — Pivot joint — Skull connects to backbone via pivot joint, allowing side-to-side head movement.
Q11B — Totipotency — F. C. Steward (1958) showed mature phloem cells can dedifferentiate, redifferentiate, and grow into complete plants.
Q12B — Lateral meristem — Increases stem diameter (girth), forming annual rings.
Q13C — Xylem — Xylem and phloem are complex tissues (more than one cell type). Parenchyma/collenchyma/sclerenchyma are simple.
Q14B — Ligament — Connects bone to bone, provides stability, prevents dislocation. Tendons connect muscle to bone.
Q15B — Lignin — Lignin deposition makes sclerenchyma cells hard, strong, and dead (woody).