K2KARAKORAM
मराठीEnglish
Open the app

State Board · Class 11 · Biology

Lesson 10: Animal Tissue

7 concepts · 56 practice questions with answers · Free to read

This lesson is also in: मराठी

Histology and simple epithelia

Link to Std 9–10

Std 9 introduced tissues; here we study structure, function and location of all four animal tissues in detail.

From daily life

Floor tiles cover a floor; epithelium likewise covers the inner and outer surfaces of the body.

Simple definition

Histology = study of tissues. Epithelium = tightly packed cells on a basement membrane with little matrix; simple = one layer, compound = several layers.

Simple epitheliaCells → Tissues → Organs → Organ systemsHistology = study of tissues (Bichat = ‘Father of Histology’)Four tissues: epithelial | connective | muscular | nervousSquamousflat, like tilesCuboidalcube-shapedColumnartall, microvilliCiliatedhair-like ciliaEpithelium: tight cells, little matrix, on a basement membrane; avascular; regenerates wellFunctions: protection, absorption, transport, filtration, secretionSquamous: vessels, alveoli | Cuboidal: ducts, nephronColumnar: intestine, gall bladder | Ciliated: trachea, oviduct

In the figure : Histology and four simple epithelia.

Rule 1 : Histology and epithelium — Cells → tissues → organs → organ systems. Animals have four tissues: epithelial, connective, muscular, nervous. Bichat = Father of Histology. Epithelium covers outer and inner surfaces; tightly packed on a basement membrane; avascular; regenerates well; functions: protection, absorption, transport, filtration, secretion.

  • Easy : Epi = above; thelium = layer of cells.
  • Medium : Epithelium has no blood vessels.
  • Exam-type (CET) : Somatic = body cells; germ = sperm/ova.

Rule 2 : Four simple epithelia — Squamous: flat, central nucleus; blood vessels, alveoli, coelom. Cuboidal: cube-shaped; secretion, absorption; salivary duct, nephron. Columnar: tall, basal nucleus, microvilli; intestine, gall bladder. Ciliated: cilia; trachea, oviduct; moves material in one direction.

  • Easy : Squamous = pavement epithelium.
  • Medium : Cilia push dust out of the trachea.
  • Exam-type (CET) : Microvilli in columnar epithelium widen the absorbing surface.
Remember

Squamous flat, cuboidal cube, columnar tall, ciliated hairy.

Common mistake and CET trap

‘Epithelium has blood vessels’ is wrong. Trap: ‘squamous nucleus at the base’ is wrong (centre).

Shortcut

Memory clue : "S-C-C-C: Flat, Cube, Column, Cilia".

Spot the difference

TypeShapeSite
SquamousFlatAlveoli
CuboidalCubeNephron
ColumnarTallIntestine
CiliatedCiliaTrachea

Practice questions

Easy
  1. 1What is histology?
  2. 2Father of histology?
  3. 3Four animal tissues.
Medium
  1. 4Two features of epithelium.
  2. 5Where is squamous epithelium?
  3. 6Special feature of columnar?
Challenging
  1. 7Function of ciliated epithelium?
  2. 8Simple vs compound.
Show answers (try them yourself first)
  1. 1Study of tissue structure.
  2. 2Bichat.
  3. 3Epithelial, connective, muscular, nervous.
  4. 4Avascular; regenerates well.
  5. 5Blood vessels, alveoli.
  6. 6Microvilli; basal nucleus.
  7. 7Moves material in one direction.
  8. 8One layer / many layers.

Glandular, sensory, germinal and compound epithelia; cell junctions

From daily life

Glands give saliva, sweat and mucus; eye, nose and ear sense stimuli; skin has many layers.

Simple definition

Glandular (secretion), sensory (stimuli), germinal (gametes), compound (stratified, transitional). Cell junctions = structures joining cells.

Epithelia and junctionsOther epithelia and cell junctionsGlandularSensoryGerminalsecretes; exocrine (duct)endocrine (ductless)perceives stimuli: nose,ear, eyemeiosis → gametestestis, ovaryCompound epitheliumStratified: skin; top stratum corneumTransitional: bladder (stretch)Cell junctionsTightseals gapsGapions passDesmosomesmechanical strengthHemidesmosomesto basement membraneGlandular: goblet (unicellular), salivary (multicellular)Exocrine = saliva, sweat | Endocrine = thyroid, pituitaryAdherens junctions: signalling, not strength

In the figure : Other epithelia, compound epithelium and four cell junctions.

Rule 1 : Glandular, sensory, germinal — Glandular: secretory granules; unicellular (intestinal goblet cell) or multicellular; exocrine (duct: salivary, sweat) and endocrine (ductless, into blood: thyroid, pituitary). Sensory: nose, ear, eye; sensory hairs. Germinal: meiosis forms gametes; seminiferous tubules, ovary.

  • Easy : Exocrine = duct; endocrine = into blood.
  • Medium : Goblet cell makes mucus.
  • Exam-type (CET) : Pancreas is both exocrine and endocrine.

Rule 2 : Compound epithelium and junctions — Stratified: many layers; top layer flat and dead (stratum corneum); skin, oesophagus, vagina. Transitional: changes shape with stretch; urinary bladder. Junctions: tight (seal gaps), desmosomes (mechanical strength), gap (ions/small molecules pass), adherens (signalling), hemidesmosomes (to basement membrane).

  • Easy : Gap junction = message exchange.
  • Medium : Desmosomes also in cardiac muscle and meninges.
  • Exam-type (CET) : Stratified = protection.
Remember

Tight seals, desmo strengthens, gap messages, hemi to the base.

Common mistake and CET trap

‘Endocrine glands have ducts’ is wrong. Trap: ‘transitional = skin’ is wrong (bladder).

Shortcut

Memory clue : "Exo = Exit by a duct; Endo = ENters blood".

Spot the difference

PointExocrineEndocrine
DuctYesNo
SecretionEnzymes, salivaHormones
ExampleSalivaryThyroid

Practice questions

Easy
  1. 1What is a goblet cell?
  2. 2Example of exocrine.
  3. 3Where is germinal epithelium?
Medium
  1. 4Where is stratified epithelium?
  2. 5Where is transitional epithelium?
  3. 6Function of tight junction?
Challenging
  1. 7Where are desmosomes?
  2. 8Function of gap junction?
Show answers (try them yourself first)
  1. 1Unicellular gland making mucus.
  2. 2Salivary, sweat glands.
  3. 3Seminiferous tubules, ovary.
  4. 4Epidermis, oesophagus.
  5. 5Urinary bladder.
  6. 6Prevent leakage; maintain polarity.
  7. 7Epithelium, cardiac muscle, meninges.
  8. 8Allows ions and small molecules through.

Connective tissue: areolar and adipose

From daily life

Soft filler stops items moving in a parcel; areolar tissue similarly packs the body and links organs.

Simple definition

Connective tissue = binds and supports organs; abundant matrix; vascular except cartilage. Types: proper (loose, dense), supporting (cartilage, bone), fluid (blood, lymph).

Areolar and adiposeAreolar (loose)FibroblastMastMacrophageWhite fibres (collagen) = strengthYellow fibres (elastin) = elasticAdiposefat droplet; nucleus pushed to edgeWhite (adults) | Brown (more vessels)Areolar: under skin, between muscles/bones; packing, healingMast cell: heparin, histamine | macrophage: phagocyticAdipose: insulator, shock absorber, energy storeSites: sole, palm, around kidneyAll connective tissues: abundant matrix; vascular except cartilage

In the figure : Fibres and cells of areolar tissue; adipose tissue.

Rule 1 : Areolar tissue — Jelly-like matrix. Two fibres: white (collagen) = tensile strength; yellow (elastin) = elasticity. Four cells: fibroblast (makes fibres and matrix), mast cell (heparin, histamine), macrophage (phagocytic), adipocyte. Site: under skin, around muscles, bones, organs. Function: packing, healing.

  • Easy : Collagen = strength; elastin = elastic.
  • Medium : Fibroblast makes fibres.
  • Exam-type (CET) : Macrophage = amoeboid phagocyte.

Rule 2 : Adipose tissue — Many adipocytes; fat droplet in the cell, nucleus pushed to the edge; little matrix and few fibres. White adipose (adults; opaque), brown adipose (more vessels; brown). Functions: insulator, shock absorber, energy store. Sites: sole, palm, around kidneys.

  • Easy : Adipose = fat warehouse.
  • Medium : Brown fat has more blood vessels.
  • Exam-type (CET) : The droplet fills the centre, so the nucleus sits at the edge.
Remember

White fibre = strength; yellow = stretch; adipose = fat.

Common mistake and CET trap

‘Collagen is elastic’ is wrong (elastin). Trap: ‘adipocyte nucleus is central’ is wrong.

Shortcut

Memory clue : "White = Withstand pull (collagen); Yellow = Yield (elastin)".

Spot the difference

FibreProteinProperty
WhiteCollagenTensile strength
YellowElastinElastic

Practice questions

Easy
  1. 1Types of connective tissue.
  2. 2What is matrix?
  3. 3Where is areolar tissue?
Medium
  1. 4What does a mast cell secrete?
  2. 5Function of macrophage?
  3. 6Three uses of adipose tissue.
Challenging
  1. 7White vs brown adipose.
  2. 8Which connective tissue is avascular?
Show answers (try them yourself first)
  1. 1Proper, supporting, fluid.
  2. 2Abundant intercellular substance.
  3. 3Under skin, around muscles, bones.
  4. 4Heparin and histamine.
  5. 5Engulfs germs (phagocytosis).
  6. 6Insulator, shock absorber, energy.
  7. 7White in adults; brown has more vessels.
  8. 8Cartilage.

Dense connective tissue and cartilage

From daily life

A rope ties muscle to bone; dense fibre tendon does just that.

Simple definition

Dense connective tissue: tightly packed fibres and fibroblasts; regular (tendon, ligament) / irregular (dermis of skin). Cartilage = tough but flexible supporting tissue (four types).

Tendon and cartilageDense regularTendon: muscle → boneLigament: bone → bone (elastic)parallel fibres (Achilles)Cartilage: four typesHyalineglassy; trachea, bone endsElasticear lobe, nose tipFibro-most rigid; intervertebral discCalcifiedsalt deposits (ageing)Chondrocytes in lacunaeMatrix = chondrin; outside perichondriumChondroblast → chondrocyte (2–8 per lacuna)Cartilage = shark endoskeleton; avascularHyaline = shock absorber, less frictionFibrocartilage lacks perichondrium

In the figure : Dense regular tissue and the four cartilage types.

Rule 1 : Dense connective tissue — Dense regular: parallel collagen fibres. Tendon = muscle → bone (white fibres; Achilles). Ligament = bone → bone (yellow/elastic fibres); prevents dislocation. Dense irregular: fibres in all directions; dermis of skin.

  • Easy : Tendon = muscle to bone.
  • Medium : Ligament = bone to bone, elastic.
  • Exam-type (CET) : Achilles tendon joins calf muscle to heel.

Rule 2 : Cartilage — Matrix = chondrin; outer perichondrium; chondroblast → chondrocyte (2–8 per lacuna). Avascular. Shark endoskeleton. Hyaline: glassy; trachea, ribs, bone ends; shock absorber. Elastic: ear lobe, nose tip. Fibro-: most rigid; no perichondrium; intervertebral discs. Calcified: hardened by salts; with age.

  • Easy : Hyaline is the commonest.
  • Medium : Fibrocartilage = spinal discs.
  • Exam-type (CET) : Calcified cartilage stiffens joints in old age.
Remember

Tendon = muscle-bone; ligament = bone-bone; fibro = hardest.

Common mistake and CET trap

‘Ligament joins muscle to bone’ is wrong. Trap: ‘fibrocartilage has perichondrium’ is wrong.

Shortcut

Memory clue : "Tendon = muscle To bone; Ligament = Links bone to bone".

Spot the difference

PointTendonLigament
JoinsMuscle-boneBone-bone
FibreWhiteYellow

Practice questions

Easy
  1. 1What is a tendon?
  2. 2Function of ligament?
  3. 3Example of dense irregular tissue.
Medium
  1. 4Matrix of cartilage?
  2. 5Where are chondrocytes?
  3. 6Where is hyaline cartilage?
Challenging
  1. 7Example of elastic cartilage.
  2. 8Why does cartilage harden with age?
Show answers (try them yourself first)
  1. 1Dense tissue joining muscle to bone.
  2. 2Joins bones; prevents dislocation.
  3. 3Dermis of skin.
  4. 4Chondrin.
  5. 5In lacunae.
  6. 6Trachea, ribs, bone ends.
  7. 7Ear lobe.
  8. 8Calcification – salts deposit.

Bone and fluid connective tissue

From daily life

Bone is like reinforced concrete: salts give hardness, fibres give strength, vessels inside keep it alive.

Simple definition

Bone = hard matrix (ossein, hydroxy-apatite). Fluid connective tissue = blood and lymph.

Structure of boneBoneHaversian system (osteon)Central canal: artery, vein, nerveLamellae, lacunae, canaliculiMatrix = ossein; hydroxy-apatite saltOuter covering: periosteumOsteoblast = active | osteocyte = inactiveOsteoclast = resorbs boneCompact: haversian system, no spacesSpongy: trabeculae; red bone marrowFluid connective tissue: blood and lymph (detail in XII)Cartilage vs bone: chondrin, avascular / ossein, vascularWhy is bone hard: mineral salt + collagen fibresCartilage hardens with age: calcification

In the figure : Haversian system of bone; fluid connective tissue.

Rule 1 : Structure of bone — Outer periosteum; matrix = ossein (hydroxy-apatite salts); lacunae in lamellae joined by canaliculi. Cells: osteoblast (active), osteocyte (inactive), osteoclast (resorbs). Haversian canal: artery, vein, nerve. Compact bone: Haversian system; spongy bone: trabeculae + red marrow.

  • Easy : Osteoblast builds; osteoclast breaks.
  • Medium : Haversian system = mammalian bone.
  • Exam-type (CET) : Spongy bone holds red marrow.

Rule 2 : Fluid connective tissue — Blood and lymph are fluid connective tissues; detailed in Std XII ‘Circulation’. Cartilage vs bone: cartilage = chondrin, avascular, flexible; bone = ossein, vascular, hard.

  • Easy : Blood = fluid tissue.
  • Medium : Bone is vascular; cartilage is not.
  • Exam-type (CET) : Bone is strong due to salts + collagen.
Remember

Osteo-blast builds, -clast breaks; Haversian canal = artery + vein + nerve.

Common mistake and CET trap

‘Bone is avascular’ is wrong. Trap: ‘osteoclast forms bone’ is wrong.

Shortcut

Memory clue : "Blast = Build; Clast = Crush".

Spot the difference

CellStateRole
OsteoblastActiveForms bone
OsteocyteInactiveMaintains
Osteoclast—Resorbs

Practice questions

Easy
  1. 1What is ossein?
  2. 2What is periosteum?
  3. 3What is in a Haversian canal?
Medium
  1. 4Lacunae and canaliculi?
  2. 5Spongy bone has?
  3. 6Fluid connective tissues?
Challenging
  1. 7Why is bone stronger than cartilage?
  2. 8Bone vs cartilage.
Show answers (try them yourself first)
  1. 1Hard matrix of bone.
  2. 2Outer membrane of bone.
  3. 3Artery, vein, nerve.
  4. 4Cavities and fine canals.
  5. 5Trabeculae, red marrow.
  6. 6Blood and lymph.
  7. 7Mineral salts + collagen.
  8. 8Ossein/chondrin; vascular/avascular.

Muscular tissue

From daily life

A muscle shortens when you lift your arm; the heart beats without stopping because its muscle is different.

Simple definition

Muscle fibre = elongated cell; sarcolemma, sarcoplasm, myofibrils (actin + myosin). Three types: skeletal, smooth, cardiac.

Types of muscleSkeletalSmoothCardiacattached to bonesvoluntary; striatedmultinucleate, peripheralsheets; hollow organsinvoluntary; no striationsone nucleus; fusiformheart (myocardium)involuntary; striatedintercalated disc; branchedSarcomereZZA band (myosin + actin) | H zone | M lineI bandI bandSkeletal: epimysium → fasciculus (perimysium) → fibreSarcolemma, sarcoplasm, myofibrils (actin + myosin)Myogenic heart (mammals) | neurogenic heart (some animals)

In the figure : Three muscle types and structure of a sarcomere.

Rule 1 : Three types — Skeletal: attached to bones; striated; voluntary; multinucleate (peripheral nuclei). Smooth: sheets/layers; fusiform; one nucleus; no striations; involuntary; slow, sustained contraction; autonomic nerves. Cardiac: myocardium of the heart; striated; involuntary; branched; intercalated discs (rapid conduction). Myogenic heart (mammals) / neurogenic.

  • Easy : Skeletal = striated + voluntary.
  • Medium : Smooth = involuntary; unstriated.
  • Exam-type (CET) : Cardiac = striated yet involuntary.

Rule 2 : Sarcomere — Sarcomere = contractile unit. Central dark A band (myosin + actin); its centre has the H zone and M line; light I bands (actin only) on either side; adjacent I bands separated by the Z line. Myosin thick, actin thin. Skeletal muscle: epimysium → fasciculus (perimysium) → fibre.

  • Easy : Z line to Z line = one sarcomere.
  • Medium : I band = actin only; A band = both.
  • Exam-type (CET) : Muscle cells have many mitochondria.
Remember

Skeletal = striated + voluntary; smooth = slow + spindle; cardiac = cannot stop.

Common mistake and CET trap

‘Smooth muscle is striated’ is wrong. Trap: ‘cardiac muscle is voluntary’ is wrong.

Shortcut

Memory clue : "Smooth = Spindle + Single nucleus; Skeletal = Several nuclei".

Spot the difference

PointSkeletalSmoothCardiac
StriationsYesNoYes
ControlVoluntaryInvoluntaryInvoluntary
NucleiManyOne1–2

Practice questions

Easy
  1. 1Covering of a muscle fibre?
  2. 2Myofibrils are made of?
  3. 3Where is smooth muscle?
Medium
  1. 4Where are intercalated discs?
  2. 5What is a myogenic heart?
  3. 6What is in the A band?
Challenging
  1. 7What is in the I band?
  2. 8Skeletal vs smooth.
Show answers (try them yourself first)
  1. 1Sarcolemma.
  2. 2Actin and myosin.
  3. 3Walls of hollow organs.
  4. 4Cardiac muscle.
  5. 5Generates its own impulse (mammals).
  6. 6Myosin + actin.
  7. 7Only actin.
  8. 8Striated voluntary multinucleate / unstriated involuntary uninucleate.

Nervous tissue

From daily life

Electricity runs along wires; a message likewise runs along nerve fibres – the brain knows of a burnt foot in an instant.

Simple definition

Neuron = structural and functional unit of nervous tissue; properties: excitability and conductivity. Neuroglia = supporting cells. No matrix.

NeuronNeuron: structure and typesCyton(Nissl granules)DendritesMyelin sheath (Schwann)Node of RanvierAxonTelodendronimpulse →Afferent = sensoryEfferent = motorInterneuronsense organ → CNSCNS → effectorintegrates impulsesBy processes: unipolar (1) | bipolar (2; retina, nose) | multipolar (>2)Myelinated = fast (saltatory) | non-myelinated = slow; autonomicNeuron: excitability + conductivity; no centriole → no regenerationNeuroglia: support cells; can divide

In the figure : Structure and types of neurons.

Rule 1 : Structure of a neuron — Cyton (cell body; neuroplasm, Nissl granules, nucleus) → dendron/dendrites (impulse towards cyton) and axon (away from cyton; axolemma, axoplasm). The axon has a myelin sheath + neurilemma (Schwann cell); gaps = nodes of Ranvier; end = telodendron. Neurons do not divide (no centriole); neuroglia do.

  • Easy : Dendron = entrance; axon = exit.
  • Medium : Myelin = fatty insulator.
  • Exam-type (CET) : Nissl granules contain RNA.

Rule 2 : Types of neurons — By function: afferent/sensory (organ → CNS), efferent/motor (CNS → effector), interneuron. By processes: unipolar (1), bipolar (2; retina, nose), multipolar (>2; one axon, axon-hillock). Myelinated = fast, saltatory conduction (cranial nerves); non-myelinated = slow (autonomic).

  • Easy : Afferent = Arrives at CNS; efferent = Exits CNS.
  • Medium : Saltatory = jumping from node to node.
  • Exam-type (CET) : Synapse = contact between neurons (Std XII).
Remember

Afferent = in; efferent = out; myelin = fast.

Common mistake and CET trap

‘Neurons divide’ is wrong. Trap: ‘autonomic nerves are myelinated’ is wrong.

Shortcut

Memory clue : "A-fferent = Arrive; E-fferent = Exit".

Spot the difference

PointMyelinatedNon-myelinated
SpeedFastSlow
ColourWhiteGrey
ExampleCranial nervesAutonomic

Practice questions

Easy
  1. 1What is a neuron?
  2. 2What is a cyton?
  3. 3What is a node of Ranvier?
Medium
  1. 4What does an afferent neuron do?
  2. 5Example of a bipolar neuron.
  3. 6What is saltatory conduction?
Challenging
  1. 7Why don't neurons regenerate?
  2. 8What is neuroglia?
Show answers (try them yourself first)
  1. 1Structural and functional unit of the nervous system.
  2. 2Cell body of a neuron.
  3. 3Gap in myelin along the axon.
  4. 4Carries impulses from sense organ to CNS.
  5. 5Retina, olfactory epithelium.
  6. 6Impulse jumps from node to node.
  7. 7They lack centrioles.
  8. 8Non-nervous supporting cells.

Quick revision of the whole lesson

ConceptKey fact
EpitheliumAvascular; S-C-C-C types
Glands / junctionsExocrine ducts; endocrine into blood; tight, gap, desmo
Areolar / adiposeCollagen strength; elastin stretch; fat
Tendon / ligamentMuscle-bone / bone-bone; four cartilages
BoneOssein; Haversian; osteoblast/clast
MuscleSkeletal, smooth, cardiac; sarcomere
NeuronCyton, dendron, axon; myelin; 3 types

🎯 Most important points for the exam

  • Four epithelia and their locations.
  • Exocrine/endocrine; cell junctions.
  • Areolar and adipose structure.
  • Tendon/ligament; cartilage types.
  • Three muscles compared; sarcomere.
  • Neuron structure and types.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.