Class 11 Biology - Chapter 16 Digestion and absorption NCERT Complete short notes | NEET 2027 | 3 - 4Q Fix = 12+ Marks

*Hello Friends 👋

As a NEET Dropper, I'm sharing my complete notes of Chapter 16: Digestion and Absorption with you all.

Mouth se leke Anus tak - Full NCERT + PYQ 

3-4 Questions fix aate hain NEET me is chapter se 🔥

Jo coaching me bhi nahi milta wo yaha hai =

All Digestive Enzymes Chart + Hormone Control + Absorption Mechanism + Disorders

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### *1. DIGESTIVE SYSTEM* `Alimentary Canal + Glands`

*Figure 1: Human Digestive System*

Mouth → Buccal Cavity → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus

Glands = Salivary + Gastric + Liver + Pancreas + Intestinal

Wall Structure = 4 Layers = Outer to Inner

1. Serosa = Outermost = Mesothelium + Thin CT

2. Muscularis = Inner Circular + Outer Longitudinal = Peristalsis

   Stomach = Oblique muscle extra

3. Sub-mucosa = Loose CT = Nerves + Blood + Lymph = Meissner's plexus

4. Mucosa = Innermost = Rugae, Villi, Goblet cells

   Muscularis mucosa = Thin muscle = Auerbach's plexus between layers

### *2. DIGESTION IN BUCCAL CAVITY* `Mouth`

Teeth = 32 = Thecodont + Diphyodont + Heterodont

Dental Formula = Adult = 2123/2123 × 2 = 32

                 Child = 2102/2102 × 2 = 20 = Milk teeth

Tongue = Gustatory receptors = Taste buds + Papillae + Frenulum attachment

Salivary Glands = 3 Pairs = Parotid + Submaxillary/Submandibular + Sublingual

Saliva = 1.5L/day = pH 6.8 = Mucus + Lysozyme + Salivary Amylase/Ptyalin

Function:

1. Starch → Maltose + Isomaltose + α-Dextrin = 30% digestion

   Optimal pH = 6.8, Inactivated in stomach pH 1.8

2. Lysozyme = Antibacterial

3. Lubrication = Bolus formation

Bolus = Food + Saliva → Deglutition = Swallowing

Epiglottis = Prevents food in trachea

### *3. OESOPHAGUS + STOMACH*

Oesophagus = 25cm = Muscular tube = No digestion

Peristalsis = Involuntary wave = Bolus to stomach

Stomach = J-shaped = 4 Parts = Cardiac + Fundus + Body + Pyloric

Capacity = 1-2L, Rugae = Folds = Increase area

Gastric Glands = 3 Types of Cells

1. Chief/Peptic/Zymogenic = Pepsinogen + Prorennin

2. Oxyntic/Parietal = HCl + Castle's Intrinsic Factor

3. Goblet/Mucous = Mucus = Protect from HCl

Gastric Juice = 2-3L/day = pH 1.8 = Highly acidic

Digestion:

1. HCl = Pepsinogen → Pepsin = Active pH 1.8-3.5

2. Proteins → Proteoses + Peptones = 10-20% digestion

3. Milk Casein → Paracasein → Ca-Paracaseinate = Curd = Rennin in infants

4. Lipase = Triglycerides → Diglycerides = Very less = No bile here

5. Intrinsic Factor = B12 absorption in ileum

Chyme = Semi-fluid acidic food → Pyloric sphincter → Duodenum

### *4. SMALL INTESTINE* `Main Digestion + Absorption`

Parts = Duodenum 25cm = C-shaped + Jejunum 2.5m + Ileum 3.5m = Total 6m

Mucosa = Villi + Microvilli = Brush border = Increase area 600x

Crypts of Lieberkuhn = Intestinal glands = Between villi

Brunner's Glands = Duodenum submucosa = Alkaline mucus

A. Liver = Largest gland = 1.2-1.5 kg = Right upper abdomen

   Lobules = Hepatic cells = Secrete Bile = 800-1000mL/day

   Bile = Bile salts + Bile pigments + Cholesterol + Phospholipids

   No enzymes in bile

   Functions: 1. Emulsification = Fat → Micelles 2. Activate Lipase

              3. Bilirubin + Biliverdin = Hb breakdown = Yellow faeces

   Gall Bladder = Stores + Concentrates bile

B. Pancreas = Heterocrine = 99% Exocrine + 1% Endocrine

   Exocrine = Acini = Pancreatic juice = 1-2L/day = pH 8.8

   Complete Digestive Juice = All 3 types enzymes

Hepato-Pancreatic Duct = Bile + Pancreatic juice → Ampulla of Vater

Sphincter of Oddi = Controls entry to duodenum

Pancreatic Juice Enzymes:

1. Trypsinogen → Enterokinase → Trypsin = Proteins → Peptides

   Chymotrypsinogen → Chymotrypsin, Procarboxypeptidase → Carboxypeptidase

2. Amylase = Starch → Maltose + Isomaltose + α-Dextrin = 100% digestion

3. Lipase = Emulsified fats → Diglycerides → Monoglycerides → Fatty acid + Glycerol

4. Nuclease = DNA, RNA → Nucleotides → Nucleosides

Intestinal Juice = Succus Entericus = 1-2L/day = pH 7.8 = Alkaline

Enzymes = Enterokinase + Erepsin + Maltase + Sucrase + Lactase + Dipeptidase + Nucleotidase + Nucleosidase

Final Digestion:

Maltose → Glucose + Glucose = Maltase

Sucrose → Glucose + Fructose = Sucrase/Invertase

Lactose → Glucose + Galactose = Lactase

Dipeptides → Amino acids = Erepsin = Dipeptidase + Aminopeptidase

Nucleotides → Nucleosides → Sugars + Bases

*Figure 2: Enzyme Summary Table*

**Site** **Enzyme** **Substrate** **Product** **pH**

**Mouth** Salivary Amylase Starch Maltose 6.8

**Stomach** Pepsin Proteins Proteoses+Peptones 1.8-3.5

**Stomach** Rennin Casein Paracasein 1.8-3.5

**Pancreas** Trypsin Proteins/Peptides Dipeptides 7.8-8.8

**Pancreas** Amylase Starch Maltose 7.8-8.8

**Pancreas** Lipase Emulsified Fat FA+Glycerol 7.8-8.8

**Intestine** Maltase Maltose 2 Glucose 7.8

**Intestine** Lactase Lactose Glu+Galactose 7.8

**Intestine** Sucrase Sucrose Glu+Fructose 7.8

**Intestine** Erepsin Dipeptides Amino acids 7.8

### *5. ABSORPTION* `Main Site = Ileum`

Mechanisms:

1. Simple Diffusion = Fructose, FA, Glycerol, Vit K, E, D, A = Along conc gradient

2. Facilitated Diffusion = Fructose = With carrier, no ATP

3. Active Transport = Glucose, Galactose, Amino acids = Na+ co-transport = ATP used

4. Micelles = Bile salts + FA + Glycerol → Diffuse in villi → Re-esterify → Chylomicrons

   Chylomicrons → Lacteal = Lymph vessel = Milky = Thoracic duct → Blood

Villi = Capillary network + Lacteal + Venules

90% Absorption = Small intestine, 10% = Stomach + Large intestine

Water, Minerals, Drugs, Alcohol = Stomach + Small intestine

Hepatic Portal System = Ileum venules → Hepatic portal vein → Liver

Liver = Detoxification + Store excess glucose as glycogen

Except fats → All nutrients first go to liver before systemic circulation

### *6. LARGE INTESTINE* `No Digestion`

Parts = Caecum + Colon + Rectum

Caecum = Vestigial Vermiform Appendix = Small pouch

Colon = Ascending + Transverse + Descending + Sigmoid

Functions:

1. Water absorption = 90% of water reabsorbed here

2. Salt absorption = Na+, Cl-

3. Bacterial flora = E. coli = Vitamin K, B12 synthesis

4. Mucus secretion = Lubrication

5. Faeces formation = Undigested + Bacteria + Bilirubin = Brown

Defecation = Rectum → Anus = Voluntary + Involuntary sphincters

Reflex = Gastrocolic = Food in stomach → Colon peristalsis

### *7. HORMONAL CONTROL* `GI Hormones`

1. Gastrin = G-cells of Pyloric stomach = Stimulates HCl + Pepsin secretion

   Stimulus = Food in stomach

2. Secretin = S-cells of Duodenum = Pancreatic juice HCO3- release = Neutralize acid

   Stimulus = Acidic chyme in duodenum

3. CCK = Cholecystokinin = I-cells of Duodenum = Gall bladder contraction + Pancreatic enzyme release

   Stimulus = Fat + Protein in duodenum

4. GIP = Gastric Inhibitory Peptide = Duodenum = Inhibit gastric secretion + motility

   Stimulus = Fat + Glucose in duodenum

5. Enterogastrone = Duodenum = Inhibit gastric activity

Trick: **G**astrin **G**ets acid, **S**ecretin **S**aves with base, **CCK** **C**ontracts gall bladder

### *8. DISORDERS OF DIGESTIVE SYSTEM* `NEET 1Q Pakka`

1. Jaundice = Liver affected = Bilirubin in blood = Yellow skin + eyes

2. Vomiting = Ejection of stomach content = Medulla reflex

3. Diarrhoea = Watery faeces = Less water absorption = Dehydration

4. Constipation = Faeces retained = More water absorption = Hard faeces

5. Indigestion = Food not digested = Incomplete enzyme secretion

6. PEM = Protein Energy Malnutrition

   a. Marasmus = Protein + Calorie deficiency = Age <1 yr = Muscle wasting

   b. Kwashiorkor = Protein deficiency = Age >1 yr = Oedema + Fatty liver

7. Appendicitis = Appendix inflammation = Surgery needed

8. Ulcer = Mucosa eroded by HCl = H. pylori bacteria

### *9. PYQ HOTSPOTS 2017-2024* 🔥

1. *Enterokinase* = Trypsinogen → Trypsin = Duodenum = NEET 2024

2. *Bile salts* = Emulsification, No enzyme = NEET 2024

3. *Ptyalin* = Salivary amylase, pH 6.8 = NEET 2023

4. *Intrinsic Factor* = Parietal cells = B12 absorption = NEET 2023

5. *Chylomicrons* = Fat absorption via lacteal = NEET 2022

6. *CCK* = Gall bladder contraction = NEET 2022

7. *Rennin* = Infant stomach, Casein curd = NEET 2021

8. *Villi function* = Increase surface area = NEET 2021

9. *Hepatic portal system* = Nutrients to liver first = NEET 2020

10. *Kwashiorkor vs Marasmus* = Protein vs Calorie = NEET 2020

11. *Succus entericus* = Intestinal juice pH 7.8 = NEET 2019

12. *Sphincter of Oddi* = Hepato-pancreatic duct = NEET 2019

13. *Lactase* = Lactose → Glu+Gal = NEET 2018

14. *Gastrin* = HCl secretion stimulate = NEET 2018

15. *Caecum* = Vestigial in humans = NEET 2017

### *10. GOOGLE SE HATKE TRICKS* 🧠

*A. Enzyme Yaad Karne Ka*

Mouth = **M**altose from **M**unching = Amylase

Stomach = **P**epsin for **P**rotein in **P**ot = Low pH

Pancreas = **TAL** = **T**rypsin + **A**mylase + **L**ipase = All in one

Intestine = **M**altase **S**ucrase **L**actase = **M**y **S**weet **L**ove

Trick: **P**unjab **TAL** **M**e **S**ab **L**adke

*B. Hormone Function*

**G**astrin = **G**et acid, **S**ecretin = **S**oda base, **CCK** = **C**ut gall bladder, **GIP** = **G**o slow stomach

Trick: **G**abbar **S**ingh **C**hicken **G**ata

*C. Absorption Route*

Glucose + Amino acid = Blood = Hepatic portal vein → Liver

Fats = Lacteal = Lymph = No liver first = Direct blood

Trick: **F**at **F**lies **L**ymph, **G**lucose **G**oes **B**lood **L**iver

*D. Dental Formula*

Adult = 2123/2123 = 2I + 1C + 2PM + 3M each half

Trick: **2** **I**ndians **1** **C**hinese **2** **P**akistanis **3** **M**alaysians

Total = 8 × 4 = 32

*Diagrams*: Human Digestive System, Villus Structure, Liver Lobule  

 

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