2. Created By :-
Pathan A.J. Mahatma gandhi vidyalay,manchar,tal : ambegaon, dist : pune STD:10TH science and technology

3. HUMAN DIGESTIVE SYSTEM
Section II

4. HUMAN DIGESTIVE SYSTEM
Ingestion
Taking food into the alimentary canal
Digestion
The chemical and physical process where large molecules are broken down to small molecule, so that the body can use them to build and nourish cells, and to provide energy.
Chemical digestion involves a chemical change from one sort of molecule to another.
Mechanical digestion involves the teeth and churning movements of the alimentary canal.

5. HUMAN DIGESTIVE SYSTEM
Absorption
The uptake of a substance into the cells of an organism’s body.
Assimilation
The incorporation of absorbed food into various parts of the body
Egestion
The removal of indigestible food from the body

6. The Human Digestive System

7. Structures
Alimentary canal is a muscular tube, running from mouth to anus
Oral cavity
Mouth
Teeth
tongue
Oesophagus
Stomach
Length of time taken for food through the alimentary canal varies depending on the person. On average it takes approx. 10hrs to reach the large intestine. From there it can be released quickly or else it might wait more than a day, depends partly on the amount of fibre in the diet.

8. Structures Liver Pancreas Small intestine Large intestine Anus
Bile duct
Pancreas
Small intestine
Duodenum
ileum
Large intestine
Colon
Rectum
Anus
Length of time taken for food through the alimentary canal varies depending on the person. On average it takes approx. 10hrs to reach the large intestine. From there it can be released quickly or else it might wait more than a day, depends partly on the amount of fibre in the diet.

9. Functions Mouth Ingestion of food here
Bolus formed here. Bolus is a ball of food formed after chewing.
Physical digestion
Tongue and teeth use to masticate the food
Mastication = mechanical grinding action of teeth
Chemical digestion
Saliva released contains salivary amylase which breaks down carbohydrates

10. Functions of the digestive system
Oesophagus
Carry the food from mouth to stomach
Peristalsis – rhythmic waves of contraction by smooth muscles in the wall of the canal that move the food

12. Functions Stomach Physical digestion Chemical digestion
Churning of the stomach helps break down the food
Chemical digestion
Hydrochloric acid released
Protease breaks down proteins
Cardiac sphincter - controls entrance of food into stomach from oesophagus
Stomach
- fully distended, human stomach holds 2-4 litres of food
- glucose and alcohol are absorbed in stomach
- takes about 4 hours to empty stomach

14. Accessory Digestive Organs

15. Functions Liver Bile duct = bile (yellowish-green watery liquid)
used in mechanical digestion of lipids
Large fat droplets broken down, increasing the surface area = emulsification
contains NO enzymes
largest internal organ
processes food by the Hepatic Portal Vein delivered from digestive tract

16. Functions Liver Functions of:
maintenance of a constant glucose level in bloodstream
detoxification of drugs & alcohol
production of bile (acts as emulsifier – begins fat breakdown
destruction old RBC & converts haemoglobin to bilirubin
regulation of cholesterol & other fats
Hepatic portal system: drains blood from digestive tract
Metabolic functions: storage, synthesis, chemical processing
largest internal organ
processes food by the Hepatic Portal Vein delivered from digestive tract

17. Liver - Assimilation
Defined as the incorporation of absorbed food into various parts of the body
The hepatic portal vein delivers the sugars and amino acids to the liver.
The liver ensures the right nutrients are sent to the right cells so that various bodily functions can occur
eg. Amino acids are made into new proteins for growth & repair OR glucose which is used for respiration

18. Accessory Organs: Aid Digestion and Absorption
Pancreas: exocrine functions
Produces pancreatic juice
contains digestive enzymes:
Amylase
Protease
lipase
Secretes sodium bicarbonate to neutralize the stomach acids
Gallbladder: stores bile

19. Functions Small Intestine Functions: Digestion:
neutralize acid from stomach,
add digestive enzymes and bile,
break proteins, carbohydrates and lipids to absorbable materials
Absorption: 95% of food absorbed here
Pyloric sphincter - sphincter separating the stomach and small intestine
regulates the passage of material from stomach to small intestine
Small intestine - surface area of small intestine is 300 m2; about the size of a double tennis court
- about 5 m long

20. Small Intestine
Very long ~5 metres (adult), more time for the food to be absorbed
Highly folded, increases the surface area for absorption
Hepatic portal vein carries the amino acids and sugars to the liver, where they are sorted and redirected to be used by the body or if in excess stored.
Excess sugar stored as GLYCOGEN
Excess amino acids deaminated (broken down) to GLYCOGEN and UREA
Sugars (eg.glucose & fructose) used for cellular respiration
Amino acids used for growth, repair or replacement of cells

21. Small Intestine Two parts Duodenum Ileum Food is mixed with
Bile
Pancreatic juice
Ileum
Intestinal juice
Maltase
Protease (peptides to amino acids)
Where absorption occurs
Inner surface folded and covered in villi

22. Structure of the small intestine

23. Villi Function Structure
Increase the surface area that can absorb food
Structure
Capillary network
Blood
- to collect the sugars
and amino acids
Lacteal (lymph vessels)
collect the fatty acids and
glycerol
One cell thick
Goblet cells
Produce mucus which
protect lining of gut
Lacteal carries the fatty acids and glycerol to the base of the neck where they join the vena cava.
Fats not used immediately for energy are stored under the skin or around vital organs

24. Absorption of Proteins and Carbohydrates

25. Absorption of Fats

26. Major enzymes of digestive system
Carbohydrates
Amylase
Mouth & duodenum
Substrate = starch
Product = maltose
Proteins
Protease
Stomach (pepsin) & duodenum (trypsin)
Substrate = proteins & polypeptides
Product = polypeptides (Stomach) & amino acids
Lipids
Lipase
Duodenum & ileum
Substrate = emulsified fats
Product= fatty acids and glycerol
Ileum enzymes =
maltase – maltose = glucose
Sucrase – sucrose = glucose and fructose
Lactase = lactose = glucose and galactose
Peptidase = polypeptides = amino acids

28. Functions Large Intestine Anus
Functions: absorbs nutrients and water, and eliminates waste
Substances found in large intestine = mostly water, dead bacterial cells, cellulose fibers, other indigestible materials, lubricated by mucus
Anus
Where egestion of waste occurs
Pyloric sphincter - sphincter separating the stomach and small intestine
regulates the passage of material from stomach to small intestine
Small intestine - surface area of small intestine is 300 m2; about the size of a double tennis court
- about 5 m long

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