K2KARAKORAM
मराठीEnglish
Open the app

State Board · Class 11 · Biology

Lesson 14: Human Nutrition

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

This lesson is also in: मराठी

Nutrition, teeth and upper alimentary canal

Link to Std 9–10

Std 8–10 introduced the digestive system; here we study organs, tissues, glands, digestive juices and disorders in detail.

From daily life

A vehicle needs fuel; the body needs food – but food must first be made usable.

Simple definition

Nutrition = taking in and using food: ingestion, digestion, absorption, assimilation, egestion. Digestion = converting complex, non-diffusible food into simple absorbable substances.

Teeth and upper canalToothEnamelDentinPulp cavityRoot canalCrownRootCementumDental formula (each half)I 2/2 C 1/1PM 2/2 M 3/3= 8 × 2 = 16 / jaw= 32 teethThecodont · Diphyodont · HeterodontNutrition = ingestion, digestion, absorption, assimilation, egestionCanal ~8–10 m: mouth → pharynx → oesophagus → stomach → intestine → anusThecodont = socket; diphyodont = two sets; heterodont = four typesTongue: papillae bear taste budsEpiglottis shuts the glottis during swallowingOesophagus ~25 cm; peristalsis pushes food down

In the figure : Tooth anatomy, dental formula and the upper canal.

Rule 1 : Teeth and dental formula — Adults have 32 teeth. Thecodont (in sockets, gomphosis), diphyodont (milk + permanent), heterodont (incisors, canines, premolars, molars). Each half-jaw has 2 I, 1 C, 2 PM, 3 M → I 2/2, C 1/1, PM 2/2, M 3/3 = 16 × 2 = 32. A tooth has crown (enamel, hardest), neck, root (cementum); inside: dentin, pulp cavity (vessels, nerves), root canal.

  • Easy : Enamel = hardest substance in the body.
  • Medium : 2-1-2-3 = I-C-PM-M.
  • Exam-type (CET) : Milk + permanent = diphyodont.

Rule 2 : Mouth, tongue, pharynx, oesophagus — Buccal cavity: lips, cheeks, palate, tongue; mucous lining; salivary glands open here. The tongue is muscular; papillae carry taste buds. The pharynx is a common path for food and air; the epiglottis closes the glottis during swallowing (deglutition). The oesophagus (~25 cm) has mucus lining; peristalsis (wave of contraction–relaxation) pushes food down.

  • Easy : Epiglottis = windpipe lid.
  • Medium : Peristalsis = wave-like movement.
  • Exam-type (CET) : Taste buds sit on papillae.
Remember

Tooth order 2-1-2-3: I-C-PM-M.

Common mistake and CET trap

‘Food passes through the glottis’ is wrong (air). Trap: ‘enamel is soft’ is wrong.

Shortcut

Memory clue : "2-1-2-3 doubled twice = 32".

Spot the difference

TermMeaning
ThecodontSet in sockets
DiphyodontTwo sets
HeterodontFour types

Practice questions

Easy
  1. 1Human dental formula?
  2. 2What is thecodont?
  3. 3Enamel made of?
Medium
  1. 4What is in the pulp cavity?
  2. 5Role of epiglottis?
  3. 6What is peristalsis?
Challenging
  1. 7Where are taste buds?
  2. 8Length of oesophagus?
Show answers (try them yourself first)
  1. 12123/2123 = 32.
  2. 2Teeth set in sockets.
  3. 3Calcium phosphate + carbonate.
  4. 4Blood vessels, nerves.
  5. 5Closes glottis during swallowing.
  6. 6Wave-like muscle movement.
  7. 7On tongue papillae.
  8. 8~25 cm.

Stomach and intestines

From daily life

The stomach is a storage-and-churning bag; the intestines are a long processing tube.

Simple definition

Stomach: J-shaped, 25–30 cm. Small intestine ~6 m (duodenum, jejunum, ileum); large intestine 1.5 m (caecum, colon, rectum).

Stomach and intestinesStomach (J-shaped)OesophagusFundusCardiaBodyPylorusCardiac + pyloric sphinctersSmall intestine ~6 mDuodenum26 cm, UJejunum2.5 mIleum3.5 mLarge intestine 1.5 mCaecum (6 cm) → Colon → Rectum → AnusAppendix : vestigialStomach: 25–30 cm; upper left; stores food 4–5 hCardiac sphincter prevents backflow; pyloric releases forwardIleo-caecal junction: ileum opens into caecumMesenteries hold the coils togetherRectum stores faeces; anus guarded by sphincterCaecum: symbiotic microbes; appendix functional in herbivores

In the figure : Parts of the stomach and intestines.

Rule 1 : Stomach — Upper left of the abdomen. Parts: cardia (cardiac sphincter prevents backflow), fundus (dome), body (large, stores food), pylorus (pyloric sphincter releases food to the duodenum). Food stays 4–5 h; churning; feeling of satiety.

  • Easy : Cardia: no return; pylorus: forward.
  • Medium : Body = storage.
  • Exam-type (CET) : Cardiac at top, pyloric at bottom.

Rule 2 : Small and large intestine — Duodenum 26 cm, ‘U’; jejunum 2.5 m; ileum 3.5 m (joins the caecum at the ileo-caecal junction). Mesenteries hold the coils. Caecum 6 cm; symbiotic microbes; appendix (vestigial in humans). Colon: ascending, transverse, descending. Rectum stores faeces; anus has a sphincter.

  • Easy : Small intestine is long but narrow.
  • Medium : Appendix = vestigial.
  • Exam-type (CET) : Colon has three parts.
Remember

D-J-I: 26 cm, 2.5 m, 3.5 m.

Common mistake and CET trap

‘Small intestine is shorter’ is wrong (it is longer). Trap: ‘appendix is vital in humans’ is wrong.

Shortcut

Memory clue : "Small = 6 m; large = 1.5 m".

Spot the difference

IntestineLengthParts
Small~6 mDuodenum, jejunum, ileum
Large1.5 mCaecum, colon, rectum

Practice questions

Easy
  1. 1Four parts of the stomach.
  2. 2Role of pyloric sphincter?
  3. 3Length of duodenum?
Medium
  1. 4Length of ileum?
  2. 5Role of caecum?
  3. 6What is mesentery?
Challenging
  1. 7Function of rectum?
  2. 8Why cardiac sphincter?
Show answers (try them yourself first)
  1. 1Cardia, fundus, body, pylorus.
  2. 2Releases food into duodenum.
  3. 326 cm.
  4. 43.5 m.
  5. 5Hosts symbiotic microbes.
  6. 6Membrane holding the coils.
  7. 7Stores faeces.
  8. 8Prevents regurgitation.

Histology of alimentary canal and digestive glands

From daily life

The canal wall is like a layered pipe – each layer has its own job.

Simple definition

Four layers (inside to outside): mucosa, submucosa, muscularis, serosa. Digestive glands: salivary glands, liver, pancreas.

Histology and glands4 layers of the canalSerosaMuscularisSubmucosaMucosaDigestive glandsSalivary: 3 pairsParotid · Submandibular · SublingualLiver: 1.2–1.5 kg; largestbile; glycogen; ureaPancreasheterocrine: exo + endoIslets: α glucagon, β insulin, δ somatostatinKupffer cells: destroy toxins, old RBCsMucosa: goblet cells (mucus); rugae + gastric glands in stomachSmall intestine: villi, microvilli, lacteals, crypts of LieberkuhnMuscularis: outer longitudinal, middle circular, inner oblique (stomach)Hepatic lobule: central vein, sinusoids; portal area with 3 vesselsBile duct + pancreatic duct → hepato-pancreatic duct (sphincter of Oddi)Acinar cells: alkaline juice; Brunner's glands in duodenum submucosa

In the figure : Four layers and three digestive glands.

Live figure

Histology of alimentary canal and digestive glands

In the app you can move this figure with your finger.

Open in the app

Rule 1 : Four layers — Serosa: outer; mesothelium (squamous) + connective tissue. Muscularis: smooth muscle; outer longitudinal, middle circular, inner oblique (only in stomach). Submucosa: loose connective tissue; vessels, nerves; Brunner's glands in duodenum. Mucosa: goblet cells (mucus); rugae and gastric glands in stomach; villi (microvilli, lacteal, capillaries) and crypts of Lieberkuhn in small intestine.

  • Easy : Inside → out: M-S-M-S.
  • Medium : Oblique muscle only in stomach.
  • Exam-type (CET) : Villi increase absorption area.

Rule 2 : Salivary glands, liver, pancreas — Salivary glands: 3 pairs: parotid (in front of ear), submandibular, sublingual; serous cells secrete amylase, mucous cells mucus. Liver: largest gland (1.2–1.5 kg); hepatic lobules, Kupffer cells; bile, glycogen store, urea, vitamins A D K B12, prothrombin, fibrinogen. Pancreas: heterocrine; acinar cells (alkaline juice) + islets of Langerhans (α glucagon, β insulin, δ somatostatin). Bile and pancreatic ducts → hepato-pancreatic duct (sphincter of Oddi).

  • Easy : Heterocrine = exocrine + endocrine.
  • Medium : Bile has no enzyme.
  • Exam-type (CET) : Kupffer cells = liver's cleaners.
Remember

Mucosa inside, serosa outside: M-S-M-S.

Common mistake and CET trap

‘Bile has enzymes’ is wrong. Trap: ‘oblique muscle in intestine’ is wrong.

Shortcut

Memory clue : "Liver = largest; islets = insulin".

Spot the difference

GlandFeature
Salivary3 pairs; amylase
LiverLargest; bile
PancreasHeterocrine; islets

Practice questions

Easy
  1. 1Layers of the canal.
  2. 2Role of villi?
  3. 3Where are rugae?
Medium
  1. 4Brunner's glands?
  2. 5Role of Kupffer cells?
  3. 6Why heterocrine?
Challenging
  1. 7What do β cells secrete?
  2. 8Where is sphincter of Oddi?
Show answers (try them yourself first)
  1. 1Mucosa, submucosa, muscularis, serosa.
  2. 2Increase absorption area.
  3. 3In stomach mucosa.
  4. 4In duodenal submucosa.
  5. 5Destroy toxins and old RBCs.
  6. 6Has exocrine and endocrine parts.
  7. 7Insulin.
  8. 8At the opening of the hepato-pancreatic duct.

Digestion in the mouth and stomach

From daily life

Chew bread long enough and it tastes sweet – salivary amylase is making maltose.

Simple definition

Mouth: salivary amylase: starch → maltose. Stomach: pepsin: protein → peptones + proteoses; HCl gives acidity. The mass is then chyme.

Mouth and stomachDigestion in mouth and stomachMouth (pH 6.8)Saliva: 98% water; amylase; lysozymeStarch → Maltose(only ~30%; continues 15–30 min)Bolus = swallowed food ballStomach (pH 1.8)Mucus · Chief · Parietal cellsPepsinogen --HCl--> PepsinProtein → Peptones + ProteosesChyme = semi-fluid acidic massParietal: HCl + intrinsic factor (B12 absorption)HCl: stops amylase; kills germs; activates pepsinogenMucus protects stomach lining from HClRennin: infants only; curdles milk caseinMechanical (churning) + chemical digestionControl: sight/smell, 10th cranial nerve, gastrinSecretin, CCK, GIP reduce gastric secretion

In the figure : Digestion in mouth and stomach.

Rule 1 : Digestion in the mouth — Mechanical: teeth chew, tongue mixes, mucus forms the bolus; swallowed by deglutition. Chemical: salivary amylase (pH 6.8) in saliva (98% water) turns starch → maltose; only ~30% in the mouth, continuing 15–30 min until HCl mixes in the stomach. Lysozyme is antibacterial.

  • Easy : Only starch is digested chemically.
  • Medium : HCl stops amylase.
  • Exam-type (CET) : Bolus = ball of food.

Rule 2 : Digestion in the stomach — Gastric glands: mucus cells (mucus), peptic/chief cells (pepsinogen), parietal/oxyntic cells (HCl + intrinsic factor). HCl acidifies food, kills germs, converts pepsinogen → pepsin (pH 1.8). Pepsin: protein → peptones + proteoses. Rennin in infants curdles milk casein. Result: chyme, passed through the pyloric sphincter. Mucus protects the lining from HCl.

  • Easy : Pepsinogen = inactive; pepsin = active.
  • Medium : Intrinsic factor → B12 absorption.
  • Exam-type (CET) : Rennin is absent in adults.
Remember

Chief = pepsinogen; parietal = HCl.

Common mistake and CET trap

‘Pepsin in the mouth’ is wrong. Trap: ‘rennin in adults’ is wrong.

Shortcut

Memory clue : "Chief cells make pepsinogen; parietal cells make HCl".

Spot the difference

CellSecretion
MucusMucus
Chief / PepticPepsinogen
Parietal / OxynticHCl + intrinsic factor

Practice questions

Easy
  1. 1Enzyme of the mouth?
  2. 2How much starch in the mouth?
  3. 3Water in saliva?
Medium
  1. 4Role of lysozyme?
  2. 5How is pepsinogen activated?
  3. 6Intrinsic factor?
Challenging
  1. 7Who has rennin?
  2. 8What is chyme?
Show answers (try them yourself first)
  1. 1Salivary amylase.
  2. 2~30%.
  3. 398%.
  4. 4Kills bacteria.
  5. 5By HCl → pepsin.
  6. 6For B12 absorption.
  7. 7Infants; curdles milk.
  8. 8Semi-fluid acidic food.

Digestion in the small intestine

From daily life

The final kitchen: bile, pancreatic and intestinal juices complete the breakdown.

Simple definition

Bile (no enzymes) emulsifies fat; pancreatic juice: amylase, lipase, trypsin, nucleases; succus entericus: disaccharidases, dipeptidases. Final food = chyle.

Small-intestine digestionDigestion in the small intestineBile (liver)Pancreatic juiceSuccus entericusno enzyme; emulsifies fatAmylase · Lipase · NucleaseDisacch'ases · Dipeptidase · LipaseStarch / glycogenPancreatic amylaseDisaccharidesMaltose / Sucrose / LactoseMaltase / Sucrase / LactaseGlucose (+ fructose / galactose)Fats (emulsified)LipasesFatty acids + monoglyceridesProteinsTrypsin → chymotrypsinPolypeptides → dipeptidesDipeptidesDipeptidaseAmino acidsNucleic acidsNucleases etc.Sugar + base + phosphateTrypsinogen → trypsin (by enterokinase)Bile pigments (bilirubin, biliverdin) colour faecesBile salts: neutralise acid, emulsify, activate lipaseEnd of digestion: food = chyle (alkaline, ready to absorb)Large gut: no enzymes; bacteria make B vitamins + K

In the figure : The three juices and their action.

Rule 1 : Bile and pancreatic juice — Bile (dark green): pigments (bilirubin, biliverdin), bile salts, cholesterol, phospholipid. Salts neutralise acid, emulsify fat, activate lipase; pigments colour faeces. Pancreatic juice (alkaline): amylase (starch → disaccharides), lipases (fat → fatty acids + monoglycerides), trypsinogen (→ trypsin by enterokinase), chymotrypsinogen, nucleases.

  • Easy : Trypsin: proteins → polypeptides.
  • Medium : Chymotrypsin: polypeptides → dipeptides.
  • Exam-type (CET) : Bile = emulsifier, not an enzyme.

Rule 2 : Succus entericus and end products — Intestinal juice = mucus + enzymes: maltase (maltose → glucose), sucrase (→ glucose + fructose), lactase (→ glucose + galactose), dipeptidase (→ amino acids), lipase. Nucleases → nucleotidases → nucleosidases → sugar + base. At the end the food is chyle. Large gut: no enzymes; bacteria make B vitamins and K; indole, skatole, H₂S cause faecal odour. Control: secretin, CCK, GIP.

  • Easy : Chyle = alkaline, ready to absorb.
  • Medium : No lactase → lactose intolerance.
  • Exam-type (CET) : CCK gives the feeling of fullness.
Remember

Bile = emulsifier; pancreas = enzyme-rich.

Common mistake and CET trap

‘Bile has lipase’ is wrong. Trap: ‘chyme = chyle’ is wrong (chyme in stomach, chyle in intestine).

Shortcut

Memory clue : "Chyme in stomach; chyle in small intestine".

Spot the difference

JuiceMain action
BileEmulsify; neutralise acid
PancreaticAmylase, lipase, trypsin
Succus entericusDisaccharidases, dipeptidase

Practice questions

Easy
  1. 1Role of enterokinase?
  2. 2What do bile salts do?
  3. 3Bile pigments?
Medium
  1. 4Lipase products?
  2. 5Role of maltase?
  3. 6What is chyle?
Challenging
  1. 7What is succus entericus?
  2. 8What does secretin do?
Show answers (try them yourself first)
  1. 1Trypsinogen → trypsin.
  2. 2Emulsify; neutralise acid.
  3. 3Bilirubin, biliverdin.
  4. 4Fatty acids + monoglycerides.
  5. 5Maltose → glucose.
  6. 6Alkaline mixture after digestion.
  7. 7Intestinal juice.
  8. 8Inhibits gastric; stimulates bile/pancreatic juice.

Absorption, assimilation and egestion

From daily life

Finished goods travel to warehouses; digested nutrients travel to blood and lymph.

Simple definition

Absorption = digested products passing through the lining into blood/lymph (~90% in small intestine). Assimilation = becoming part of cells. Egestion = expelling undigested waste.

AbsorptionAbsorptionVillicapillary (red) + lacteal (orange)Capillary: glucose, amino acids, waterLacteal: fats, vit A D E KMicelle → chylomicron → lymph~90% absorbed in small intestineModes: simple diffusion, osmosis, facilitated, active transportNa⁺ is active (energy); fructose facilitatedMouth: some drugs; stomach: alcohol, aspirinLarge gut: water, Na⁺, Cl⁻, some vitaminsAssimilation: food becomes part of protoplasmEgestion: faeces in rectum; voluntary expulsion

In the figure : Absorption through villi and the sites.

Rule 1 : Modes and sites of absorption — Modes: simple diffusion (some glucose, amino acids, Cl⁻), osmosis (water), facilitated transport (fructose, some amino acids), active transport (Na⁺; energy, against gradient). Sites: mouth (some drugs), stomach (alcohol, aspirin), small intestine (most), large intestine (water, Na⁺, Cl⁻, some vitamins).

  • Easy : Active = energy, uphill.
  • Medium : Small intestine = ~90%.
  • Exam-type (CET) : Water follows concentration.

Rule 2 : Fat absorption, assimilation, egestion — Glucose, fructose, galactose, amino acids, water-soluble vitamins → villus capillaries. Fatty acids + monoglycerides cannot enter blood directly → bile-salt micelles → in villi they become chylomicrons (protein-coated fat globules) → lacteals (lymph) → blood. Fat-soluble vitamins A D E K go via lacteals. Egestion: faeces form in the colon (water, salts, dead cells, bacteria, undigested food); rectal stretch starts a reflex; expulsion is voluntary (sphincter).

  • Easy : Chylomicron = fat vehicle.
  • Medium : Lacteal = fat route.
  • Exam-type (CET) : Assimilation = food becomes cell material.
Remember

Sugar, protein → capillary; fat → lacteal.

Common mistake and CET trap

‘Fat enters blood directly’ is wrong (micelle → lacteal). Trap: ‘most absorption in large intestine’ is wrong.

Shortcut

Memory clue : "Fat takes the lacteal route; sugar goes straight to blood".

Spot the difference

SubstanceRoute
Glucose, amino acidsCapillary
Fatty acids, A D E KLacteal
Water, Na⁺Large intestine

Practice questions

Easy
  1. 1What is absorption?
  2. 2% absorbed in small intestine?
  3. 3Example of active transport?
Medium
  1. 4What is a micelle?
  2. 5What is a chylomicron?
  3. 6What is a lacteal?
Challenging
  1. 7What is assimilation?
  2. 8How is egestion controlled?
Show answers (try them yourself first)
  1. 1Products pass into blood/lymph.
  2. 2~90%.
  3. 3Na⁺ absorption.
  4. 4Bile-salt sphere carrying fat.
  5. 5Protein-coated fat globule.
  6. 6Lymph vessel in a villus.
  7. 7Food becomes part of cells.
  8. 8Reflex + voluntary sphincter.

Nutritional and digestive disorders

From daily life

A little too much or too little food causes trouble; diet is the medicine.

Simple definition

PEM (Protein Energy Malnutrition): Kwashiorkor and Marasmus. Digestive disorders: indigestion, constipation, diarrhoea, jaundice, vomiting.

Nutritional and digestive disordersNutritional and digestive disordersKwashiorkor1–3 yr; protein deficiencyoedema, protruding bellyMarasmus<1 yr; protein + calories lowno fat; ribs visible; no oedemaPEM = Protein Energy MalnutritionIndigestion: overeating, spicy food; acid reflux, heartburnConstipation: <1 stool/week; fibre, fluids, exerciseDiarrhoea: 3+ loose stools/day; dehydrationJaundice: excess bilirubin; yellow eyes/skin, pale stoolVomiting: reverse peristalsis; medulla centreEnergy: fat 9.0 · protein 4.0 · carbohydrate 4.0 kcal/gAlcohol harms the liver: fatty liver, hepatitis, cirrhosis

In the figure : PEM and digestive disorders.

Rule 1 : Kwashiorkor and Marasmus — Kwashiorkor: children 1–3 yr; protein deficiency; underweight, stunted growth, poor appetite, protruding belly, thin legs, oedema of face/legs, skin-hair colour change. Marasmus: under 1 yr; protein + total calories low; no subcutaneous fat, ribs visible, wrinkled skin; no oedema. Causes: poverty, large family, early stopping of breast-feeding, diluted milk. Improves with proper diet. Physiological energy: fat 9.0, protein 4.0, carbohydrate 4.0 kcal/g.

  • Easy : Kwashiorkor = oedema; marasmus = no oedema.
  • Medium : Both are PEM.
  • Exam-type (CET) : Fat = highest calories.

Rule 2 : Digestive disorders — Indigestion: overeating, spices, anxiety; acid reflux, heartburn, dyspepsia; avoid large meals and lying down. Constipation: stool less than once a week; fibre, fluids, exercise. Diarrhoea: more than 3 loose stools a day; dehydration; infection. Jaundice: excess bilirubin or bile-flow obstruction; yellow eyes/skin, pale stool. Vomiting: reverse peristalsis; medulla centre. Alcohol causes fatty liver, hepatitis, cirrhosis.

  • Easy : Jaundice = bilirubin trouble.
  • Medium : Diarrhoea risks dehydration.
  • Exam-type (CET) : Fibre helps constipation.
Remember

Kwashiorkor = swollen; marasmus = meagre.

Common mistake and CET trap

‘Marasmus has oedema’ is wrong. Trap: ‘jaundice is only infection’ is wrong (bilirubin).

Shortcut

Memory clue : "Kwashiorkor swollen; marasmus matchstick-thin".

Spot the difference

PointKwashiorkorMarasmus
Age1–3 yr<1 yr
DeficiencyProteinProtein + calories
OedemaYesNo

Practice questions

Easy
  1. 1What is PEM?
  2. 2Age in kwashiorkor?
  3. 3Oedema in marasmus?
Medium
  1. 4Define constipation.
  2. 5Risk in diarrhoea?
  3. 6Why does jaundice occur?
Challenging
  1. 7Vomiting centre?
  2. 8Highest energy food?
Show answers (try them yourself first)
  1. 1Protein Energy Malnutrition.
  2. 21–3 years.
  3. 3No.
  4. 4<1 stool per week.
  5. 5Dehydration.
  6. 6Excess bilirubin / bile obstruction.
  7. 7Medulla.
  8. 8Fat (9.0 kcal/g).

Quick revision of the whole lesson

ConceptKey fact
Teeth2123/2123 = 32; thecodont
IntestineSmall 6 m; large 1.5 m
GlandsSalivary 3; liver; pancreas
Mouth/stomachAmylase; pepsin + HCl
Small intestineBile, pancreatic, succus; chyle
AbsorptionCapillary vs lacteal; 90%
DisordersPEM; jaundice; diarrhoea

🎯 Most important points for the exam

  • Tooth structure and dental formula.
  • Parts of stomach and intestines.
  • Four layers; glands.
  • Amylase, pepsin, HCl.
  • Bile, pancreatic juice, succus entericus.
  • Micelle, chylomicron, lacteal.
  • Kwashiorkor vs marasmus.
Study mantra

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