Human Digestive System:

• The breakdown of complex food is called Digestion.
• Carbohydrates break down into Glucose.
  Protein breakdown into Amino Acid.
  Fat breakdown into Fatty Acid.
• In the Human digestive system, the breakdown of complex food is absorbed by the blood and transported to all body parts.
• Digestion is the hydrolytic reaction.
•  

Alimentary Canal:

• Length: 30 feet or 9 Meters
• It has 7 Parts:
  Alimentary Canal: Mouth→Oesophagus→Stomach→Small Intestine→Large Intestine→Rectum→Anus.

Mouth: The First part of the Human Digestive System

• In the human digestive system, the Partial digestion of Carbohydrates/ Starch takes place here.
• Saliva:
  (1.) Lubricant: MUCUS
  (2) Enzymes: (I) Ptyalin (ii) Lysozyme
  (I) Ptyalin: It converts starch into Maltose
  (ii) Lysozyme: It kills bacteria present in the food.
• Appiglotis:  It Separates food pipe from the windpipe.
• PH of Saliva: 6.8
  Note: PH: Potential of Hydrogen. It measures the concentration of Hydrogen ions in the substance. 
  Enzymes get their energy from PH. PH scale was discovered by Soren Peter. PH is also called the ‘Bio-catalyst of the body‘.

Oesophagus:

• NO digestion of food takes place here.
• Length: 25cm
• Food moves in it by ‘Peristalsis Pressure’.
• Divided into three parts: (i) Cervical (ii) Thoracic (iii) Abdominal

Stomach:

• Partial digestion of Protein and fats takes place here.
• It produces Glycoprotein in the intestine, which is essential for the absorption of vitamin B_12.
• The stomach has three cells:
  (i) Peptic/ Zymogenic/ Chief Cell: Secrete two types of Pro-enzymes- 1. Pepsinogen, 2. Pro-renin
  Pepsinogen + HCL = Pepsin
  Pro-renin + HCL = Renin
• (ii) Oxyntic/ Parietal Cell: HCL is released by it, which activates Pepsinogen and pro-renin.
• (iii) Globlet Cell: Released MOUCUS substance which protects the Stomach wall from acid(HCL) attack.
• Pepsin:
  It converts protein into Polypeptides(amino acids).
  PH of pepsin: 2.2
  Renin: It converts Milk into casein Protein
• Parts of Stomach: 
  (i) Cardia (Upper part)
  (ii) Fundus (MIddle Part)
  (iii) Pyloric (Lower part- in this part Gastric gland is found).

Small Intestine:

• The major part of the Digestive System.
• The longest part of the alimentary canal: 6.25 meters.
• Small Intestine has three parts:
  (i) Duodenum (uncoiled)
  (ii) Jejunum (Slightly coiled)
  (iii) ileum (Highly coiled)
• Digestion and absorption of Protein, Carbohydrates, Fats, Nucleic Acid, etc takes place here.

Large Intestine: 

• No digestion of food takes place as already digested food reaches here.
• Complete Absorption of food and water takes place here.
• Length: 1.5 meters
• Three parts:
  (i)Caecum
  (ii)Colon
  (iii)Rectum
• Note: The ileum of the small intestine and the Ceacum of the large intestine are connected.

Liver:

• Weight of Liver in human:
  Male=1.4-1.8kg and Female=1.2-1.5kg.
• Unit of liver: Hepatocyte
• The first Organ work in a baby is the liver.
• The liver is made of hepatocyte cells. These cells are covered in the ‘Glisson’s capsule’
• The liver is the largest organ of our body. It helps get rid of toxic materials from our bodies.
  It detoxifies the drugs and alcohol from the body.
• Liver Function: 
  1. Production of Bile Juice (85% H₂O + 12% pigment)_. Ph = 7 to 8.6 (alkaline).
  Bile juice helps in the Emulsification of fats (which means it transfers fat into the blood).
  Bile juice does not help in the digestion of food because there are no enzymes present in it.
• Two Pigments are present in the bile juice: (i)Biliverdin and (ii) Bilirubin
  (i) Biliverdin: Green in color and present in low amount.
  (ii) Bilirubin: Yellow and present in large amounts. It is responsible for the yellow color of Plasma and Fences.
• 2. Deamination (remove ammonia from the body).
• 3. Excretion of urea from the body.
• 4. Glycogensis (convert excess glucose into glycogen)
• 5. Glycogenolysis (convert excess glycogen into glucose)
• 6. Lipogensis (convert excess glucose and amino acid into fats).
• 7. Haemopoesis (Formation of RBCs)
• 8. Secretion of Protein:
  Heparin (Blood anti-coagulation properties)
  Fibrinogen (Helps in blood clotting)
• 9. Synthesis of vitamin A form β-carotene.
• 10. Production of heat – control body temperature.
• 11. Osmoregulation – balanced body water level
• 12. Storage: Glycogen, Fats, Blood, Water, Iron, Potassium, and Vitamins K, E, D, A.  
  [Vitamins soluble in Fats: KEDA]

Gall Bladder:

• It only stores bile juice.
• Stone (पथरी): made of Calcium Oxalate.
• Rats and Horses have no gallbladder present in their body.

Pancreas:

• It is both the Endocrine as well as Exocrine gland.
• Exocrine Part: consists of Pancreatic juice
  Pancreatic juice contains: (i) Insulin, (ii) Glucagon, (iii) Somatostatin
• Endocrine Part: consists group of cells called ‘ISLETS OF LANGERHANS‘
  ISLETS OF LANGERHANS have four cells:
  1. α-cell (alfa): Secrete – Glucogen Hormones
  2. β-cell (beta): Secrete – Insulin Hormones
  3. δ-cell (delta): Secrete –  Somatostatin Hormones
  4. F-cell or PP-cell: Digestion
• Glucogen Hormones increase the amount of Glucose in our body
  Insulin Hormones decrease the amount of Glucose in our body
  Somatostatin Hormone controls both the glycogen as well as insulin. This opposite effect is called the ‘Antagonistic Effect’ 
• When Insulin(↑) ⇒ Glucose (↓)  Results in Hypo-gly-comma  
  When Insulin(↓) ⇒ Glucose (↑)  Results in Diabetic/ Mellitus
• Insulin:
  Discovery: Dr. H Banting
  Metal present in insulin: Zinc
  Metal present in Haemoglobin: Fe
  Metal present in Chloroplast: Mg