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1. DIGESTIVE SYSTEM

2. a. mouth
b. Larynx
c. esophagus
d. stomach
e. Small
intestine
f. Large
intestine
g. rectum
h. anus
i. Saliva glands
j. liver
k. gallbladder
l. pancreas

3. Digestive System
■ the organs and glands in the body that are responsible
for digestion.
■ Involve the breakdown of foods into simpler nutrients to
be absorbed by our body.
■ Responsible for the survival of the human beings and
animals.

4. TWOTYPES OF DIGESTIVE SYSTEM
■ INCOMPLETE DIGESTIVE SYSTEM – common among invertebrates,
there is only a single opening for
the ingestion of food.
(an anus is absent)
■ COMPLETE DIGESTIVE SYSTEM – common among nematodes,
annelids, mollusks, echinoderms, and
vertebrates, this type has digestive
tubes with two openings.
(a mouth and an anus)

5. FOUR MAJOR FUNCTION OF DIGESTIVE
SYSTEM
1. Ingestion of food
- the intake of foods into the body.
2. Digestion of food
- the process of mechanical and chemical breakdown where by
large food molecules are broken down into soluble and diffusible
molecules that can be absorbed into the body cell.

6. 3. Absorption of nutrients
- it is the process whereby digested food materials are taken
into the body cells and are converted into new protoplasm or
used to provide energy.
4. Eliminates of waste materials
- passing of digested materials out of the digestive tract.

7. Digestion of food follows two distinct
processes;
Physical or Mechanical digestion
-involves the breaking up of food into small
pieces/particles, pushing the food down the food tube,
and mixing with its digestive juices.
Chemical Digestion
-is the breakdown of the complex molecules, such as
proteins, starch, fats contained in foods into soluble
molecules by the action of digestive enzymes.

8. HOW DIGESTION
IS DONE?
It start from….

9. ■ The intake of food starts from our MOUTH, which leads to our mouth
cavity.
■ MECHANICAL DIGESTION starts in the MOUTH (Mastication) where four
kinds of teeth tear the food into pieces:
Four kinds of teeth:
1. INCISORS – thin-edged for cutting food.
2. CANINES – are pointed used for tearing.
3. MOLARS & PREMOLARS – specialized for crushing and grinding.
MECHANICAL PHASE OF DIGESTION INTHE MOUTH

10. THE HUMANTEETH / MAN’S DENTAL SET

11. ■ Mucin- helps to soften the food, while chewing it
helps to break down the foods into smaller pieces.
■ Saliva also contains a chemical substance called
ptyalin ( also called salivary amylase), the enzyme that
chemically digest cooked starch into a disaccharide
maltose.
What happens after you finished chewing the
food?

12. ■ The bite food is then swallowed and is moved through the
pharynx into the esophagus.
Pharynx- common passage for food and air.
- it is the part of the gut which leads from the mouth
to the esophagus and to the trachea by way of the larynx or
voice box.
- the larynx bears a slitlike opening called glottis.
- epiglottis a piece of flaplike cartilage, covers the
larynx.

13. Esophagus- also called gullet.
- a narrow muscular tube.
- comes from the Greek word meaning “to carry
what is eaten”.
- two layers of smooth muscles cause rhythmic,
wavelike contractions of the wall of the gut.
This movements known as peristalsis.

14. MECHANICAL PHASE:THE PROCESS OF PERISTALSIS

15. ■ Then, food is mechanically and enzymatically digested in the stomach.
STOMACH- J shaped organ, it lies beneath the diaphragm and partially covered
by the liver.
- Gastric Juice is a dilute solution of hydrochloric acid and the enzyme
pepsin, an active enzyme secreted by the chief cell of the gastric glands.
-The stomach secretes millions of gastric glands.
■ THE PARIETAL CELLS
– in the gastric glands secrete hydrochloric acid and intrinsic factor, a
substance needed for adequate absorption of vitamin B12.
■ THE CHIEF CELLS
– secrete pepsinogen (an inactive enzyme precursor).When pepsinogen
comes in contact with the acidic gastric juice, it becomes pepsin (the main
digestive enzyme of the stomach).
- pepsin breaks some complex proteins even further into simpler proteins.

16. ■ The stomach joins the small intestine, through a muscular to valve called the pyloric
sphincter.
■ After mixing the food inside of the stomach and then it became soft, watery
substance forming chyme.This now ready to move slowly to the next part, which is
the small intestine.
■ Digestion is completed in the small intestine and nutrients are absorbed through its
wall.
■ The small intestine is about 5 to 6 meters (about 17ft.) in length and has three
regions.
1. Duodenum- the U shape
2. Jejunum
3. Ileum- the much coiled
- Intestinal juice helps break down food arriving from your stomach.This juice does
not work alone, it is helped by the juices that are produces by two organs which
are the liver and pancreas.

17. How absorption of food nutrients is
done?
■ Protein are broken down individual amino acids.
■ Carbohydrate are broken down into simpler sugar.
■ Fats are broken down into fatty acids and glycerol.
■ It’s inner lining is covered with a million of tiny fingerlike
structures called villi (villus), projecting into the intestinal
cavity.

18. Some Digestive Enzymes
Digestive Juice Source Digestive Enzymes Works on Change it to
Saliva Salivary glands
Ptyalin (salivary
amylase) and
mucin
Starch Complex sugar
Gastric juice
Gastric glands in
the stomach
pepsin proteins Simpler proteins
Pancreatic juice Pancreas
Pancreatic amylase Starch Complex sugar
Trypsin Proteins Simpler proteins
Lipase Fats Fatty acids and
glycerol
Intestinal juice
Intestinal glands
in small intestine
Lactase, maltase,
sucrase
Complex sugar Simple sugar
Peptidase Simpler proteins Amino acids
Lipase Fats
Fatty acids and
glycerol

19. THETHREE REGIONS OFTHE SMALL INTESTINE

20. THE LAYERS OFTHE SMALL INTESTINE (Labelled)

21. LIVER
■ the largest internal organ of the body and also one of the most complex organs
which lies in the upper right abdomen just under the diaphragm.
■ Its dark and color red.
■ the liver secretes BILE.
BILE – greenish-yellow fluid secreted by the liver which emulsifies fats
-bile is temporarily stored in gallbladder, greenish-yellow bag.
- has three attached blood vessels
1. hepatic portal vein
2. hepatic vein
3. hepatic artery
■ Other important functions of the liver.
– Protein synthesis
– Iron storage
– Detoxification
– Heat production

22. Pancreas
- Is a soft triangular gland lying between the small intestine and the
stomach.
- It is connected to the duodenum of the small intestine by means of
pancreatic duct.
- It produces pancreatic juices, which is a mixture of digestive enzymes.
- This enzymes move to small intestine at the same time the bile does and help
to break down proteins, starches, and fats.
- The enzymes secreted by the pancreas are calledTRYPSIN and
CHYMOTRYPSIN.
- It also secretes INSULIN, which plays an important role in the control of the
blood sugar level in the body and utilization of carbohydrates.

23. Absorption in the large intestine.
■ Shorter but much broader than the small intestine.
■ At the junction between the small intestine and the ascending colon (part of the large
intestine) is a small sac, called the caecum and the blindly ending appendix.
■ Is about 1.5 meters long consist of the following:
1. Caecum and the appendix
2. Ascending colon running upwards along the right side of the abdominal cavity.
3. Horizontal transverse colon
4. Descending colon which runs downward to join the rectum
5. Rectum (a short muscular tube)
FUNCTIONS OF LARGE INTESTINE;
- to absorb water and mineral salt.
■ Most of the water that is contained in undigested food is absorbed.
■ Helpful bacteria resides at the large intestine make certain vitamins, such as vitamin K
and B vitamins, that also needed by our body.

24. Elimination of waste materials;
■ Materials that are not absorbed in the large intestine is called feces.
– Made up of dead bacteria and some fat and protein.
Undigested food roughage, dried out digested juices, mucus, and
discarded intestinal cells, is stored temporarily in the rectum.
When the rectum contracts, the feces is expelled through the
opening called anus.
The process of removing undigested matter from the body is called
egestion, defecation, or vowel movement.

25. How long food stays in the digestive organs
Structure Primary Function
Time food stays in the
structure
Mouth
Mechanical and chemical
digestion
5-30 seconds
Esophagus
Transport of food after
swallowing
7- 10 seconds
Stomach
Mechanical and chemical
digestion of food
2-24 hours
Small intestine
Mechanical and chemical
digestion of food
3-5 hours
Large intestine Water absorption 18 hours- 2 days