The document discusses the human digestive system. It begins with the mouth and ends with the anus. The major organs are the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus. Accessory organs include the liver, salivary glands, gallbladder and pancreas. The digestive process involves ingestion, mechanical and chemical digestion, absorption, assimilation and excretion. Food is broken down and nutrients are absorbed and transported to cells to be used for energy and growth.

1. THE HUMAN NUTRITION
RETHABILE CHABELI

2. • DISCUSS, IDENTIFY AND INTERPRET THE
PATHWAY OF FOOD THROUGH THE BODY AND
PROCESSES THROUGH WHICH FOOD IS BROKEN DOWN
AND USED BY THE BODY.
• MAKE INFERENCES FROM DIAGRAMS AND
GRAPHS.
• DRAW VARIOUS PARTS AND ORGANS OF THE
HUMAN DIGESTIVE TRACT.
• IDENTIFY AND DISCUSS THE HUMAN DIGESTIVE
TRACT BY EXPLAINING THE FUNCTIONS, LOCATION AND
AND STRUCTURE OF THE VARIOUS ORGANS OF THE
HUMAN DIGESTIVE TRACT.
• DISTINGUISH BETWEEN CHEMICAL AND
MECHANICAL DIGESTION.
• EXPLAIN THE ADAPTATION OF THE VILLI TO ITS
FUNCTION.
• DISCUSS THE DIFFERENT PROCESSES ASSOCIATED
WITH NUTRITION.

3. STRUCTURE OF HUMAN DIGESTIVE
TRACT
• Humans have a complete digestive tract
 begins with mouth & ends with anus.
• The major structures of human digestive
tract:
• mouth,
• pharynx,
• esophagus,
• stomach,
• small intestine,
• large intestine,
• rectum and
• anus.

4. THE ACCESSORY ORGANS OF
DIGESTION ARE THE
•Liver
•Salivary glands
•gall bladder
•pancreas

6. WHY IS DIGESTION IMPORTANT?
To convert large
(insoluble molecules)
of food  smaller
soluble molecules
absorbed into the
blood or lymph
capillaries &
used for various
metabolic processes.

7. DIGESTIVE PROCESS
•INGESTION
•DIGESTION – MECHANICAL
AND CHEMICAL
•ABSORPTION
•ASSIMILATION
•EXCRETION

8. PATHWAY OF FOOD AND
RELATED PROCESSES IN
THE BODY

9. MOUTH
•Ingestion:
•Teeth:
- Mechanical digestion

10. STRUCTURE OF A MOLAR

11. SALIVA
 Secreted by the salivary
glands (parotid gland,
sublingual gland & sub-
maxillary gland)
bolus.
• Saliva contains enzyme
(amylase)
• Chemical digestion.

12. TONGUE
• Mixes food with saliva & pushes food
between teeth.
• Makes swallowing easier.

13. ESOPHAGUS
•Bolus  forced down  esophagus
•NB!!! Peristalsis
•No absorption takes place
• epiglottis

14. EPIGLOTTIS

15. PROCESS OF PERISTALSIS

16. PERISTALSIS

17. STOMACH (ISISU)
• Food enters the stomach
• Remains 30 min  (peristalsis).
• Food move with circular movements through
stomach
• Mechanical digestion

18. • Gastric juices  gastrin
• Gastric juices consist of:
• 1.HCl
• 2.digestive enzymes
• 3.mucus
• 4.water.

19. •Gastric juices  chemical digestion 
chym.
• Some absorption occurs in stomach:
• water, glucose, salt and certain drugs and
alcohol

21. SMALL INTESTINE
• Chym enters duodenum (
• Mix with bile &
• pancreatic juices.

22. CHEMICAL DIGESTION
• Secretin  pancreatic juice
• Pancreatic juice contain:
• sodium bicarbonate
• digestive enzymes
• Bile

24. FUNCTIONS OF BILE
•Neutralizes acid
•Emulsifies fats
•absorption of fats.
•Reduce fluidity
•Antiseptic
•absorption of fat-soluble
vitamins.

25. •Chym moves through jejunum
•Mixes with intestinal juice (succus
entericus)
• Peptidase, lipase, lactase, maltase, sucrase
•Succus entericus
• Crypt of Lieberkuhn & glands
of Brunner

26. MECHANICAL DIGESTION
• The 2 muscle layer of the small intestine helps
with the process of peristalsis.
Cross section through the small intestine

27. FUNCTIONS OF THE LIVER - ISIBINDI
•Produces & secretes bile.
•Stores glucose glycogen & controlled
by hormone insulin.
•Convert excess carbohydrates into
(fatty acids + glycerol) = fats.

28. •Stores blood temporarily
•Manufactures plasma proteins
Forms heparin
•Detoxifies

29. • Liver breaks down surplus amino acids
through process of deamination:
• Change amino acid  ammonia.
• 2 x ammonia molecules combine with
1 molecule of CO2  urea & water.
• Urea conveyed to kidneys for
excretion.
• Deaminated amino acids converted into
glucose (glucose converted to glycogen
& stored in liver)

30. BLOOD SUPPLY OF THE LIVER
• Hepatic portal vein  digested food
from small intestine to liver
• Hepatic artery  transports O2 &
nutrients to the liver (enter the liver).
• Inside liver blood of these 2 blood vessels
mix
• Waste moves out of liver cells &
transported hepatic vein  inferior
vena cava.

31. BLOOD SUPPLY TO THE
LIVER CELLS

32. ABSORPTION FROM THE SMALL
INTESTINE
• Food mainly absorbed from small
intestine  where all final digestive
processes take place & end-products
of digestion is formed.
• The final products of digestion:
glucose, amino acids, fatty acids and
glycerol formed in small intestine.

33. ADAPTATIONS OF THE SMALL
INTESTINE FOR THE ABSORPTION
OF FOOD.
• The absorptive surface area is increased by:
• The great length of the small intestine (6-
7m)
• The circular folds of the mucosa lining of
the small intestine.
• The millions of villi lining the folds.
• The chym is pushed along very slowly
through the small intestine, allowing time
for absorption to take place.

35. STRUCTURE OF THE VILLUS
• Villus consist of several capillary arteries
supply villus with O2 &
• capillary veins  carry food away from the
villus.
• Lacteals (lymph vessels)  found in center of
each villus  used for the absorption of fats.
• Vessels surrounded by connective tissue & a
layer of columnar epithelial cells with goblet
cells

36. STRUCTURE OF THE VILLUS

37. THE PROCESS OF ABSORPTION IN
THE SMALL INTESTINE
•The columnar epithelial cells play
active part in absorption & able to
allow substances to enter villi
•Amino acids, glucose, mineral salts,
water & vitamins absorbed directly into
the blood.

38. FAT ABSORPTION FROM SMALL
INTESTINE
• Fatty acids (insoluble) combine with bile salts
• To form fatty acid-bile salt complex which is
(soluble) in water.
• This complex plus glycerol component of fat 
absorbed by columnar epithelial cells of villi.
• Inside villus  fatty acids freed from the bile
salts & recombine with glycerol to form tiny fat
globules.

39. FAT ABSORPTION FROM SMALL
INTESTINE
• Some of the fat globules are absorbed
directly into the blood capillaries.
• Most fat globules are absorbed by the
lacteals.
• The lacteals unite to form small lymph
vessels which enter main lymphatic system.
• Fat in lacteal now known as chyle, & it
reaches bloodstream in the end.

40. LARGE INTESTINE
•No digestion takes place in the
colon.
•Undigested food particles from
small intestine enter the caecum
through ileocaecal valve.
•In colon  water is absorbed 
chym becomes semi-solid.

41. LARGE INTESTINE
• Symbiotic bacteria present in colon act
upon food rests  decomposing them &
turning them into faeces.
• Bacteria synthesize vitamins Bgroups and K 
essential for blood clotting process.
• Peristalsis in colon  facilitated by mucus
produced by numerous mucous glands.
• Mucus assists the movement of feces &
protects the wall of the colon.

42. HUMAN COLON

43. RECTUM
•By the time feces reach the
rectum  consist of
approximately 70% water.
•Bacteria account for about
30% of dry mass of feces
•Remainder made up of food
residue (mainly cellulose).

44. FAECES STORED IN RECTUM

45. ANUS
•Defecation (excretion)  brought
about by
•contraction of the circular muscles
of rectum &
•relaxation of the muscles which
make up the anal sphincter.

46. REFERNCES
• Singh P, 2018. Human Digestive system. Available at:
https://www.slideshare.net/poojasingh676/plant-kingdom-112561675?next_slideshow=1
• Cena, S., 2009. Human digestive system. Available at:
https://www.slideshare.net/sjcena/human-digestive-system?qid=945724ff-61bc-468d-
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• Jose, A., S. 2017. Human digestive system: Grade 8. Available at:
https://www.slideshare.net/AaronJose1/the-human-digestive-system-
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• Bhatia S., K. 2018. Physiology of human digestive system. Available at:
https://www.slideshare.net/sanjayqau47/physiology-of-human-digestive-
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• Nori H, 2015. Digestive system structure and functions. Available at:
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• Bhatti S,. S. 2018. Digestive system. Available at:
https://www.slideshare.net/ShaharyarShoukatShou/human-digestive-system-
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