• In the mouth we have the teeth, tongue and salivary glands.
• The denture compose 32 pieces in adults.
• The teeth are formed by a hard, enamel substance and are housed in
• Used to grind food with some movements called chewing, sometimes
when no food remains are removed, holes occur in the enamel called
3. The tongue is a muscle that propels the food bolus into the pharynx.
Also it lies onthe tongue taste, for her distinguish the flavors.
The salivary glands are glands located under the tongue and below
the jaw just below the ears. Also produce saliva to moinsten the cud.
Are substances that begin the transformatios of some foods.
Saliva is a watery substance located in the mouths of animals,
secreted by the salivary glands. Human saliva is 99.5% water, while
the other 0.5% consists
of electrolytes, mucus, glycoproteins, enzymes
(lysozyme), antibacterial, and bacteria compounds.
In the mouth the digestion
of food begins.
• Is a muscular tube, about 25 cm long and 2 cm in
diameter, that carries food from the pharynx to the
• The esophagus normally has three narrowings:
5. The esophagus:
• Has an inner circular muscle layer and outer longitudinal.
• Finish entering the stomach by gastric cardia orifice at
level of seventh costal cartilage left and thoracic vertebra
• The abdominal esophagus is separated from the fundus
of the stomach through the notch of the cardia.
6. The back side of the abdominal esophagus is covered by
peritoneum of the omental pouch, which covers the back of
Fast food passes through the esophagus due to the peristaltic
action of their muscles, with the aid of gravity without
7. • The stomach is a muscular organ located on the left side
of the upper abdomen. The stomach receives food from
the esophagus. the stomach is divided into four sections:
cardia, fundus, body and pylorus.
8. • In the stomachs starts the protein digestion, Parietal cells
secrete HCl, chief cells of the gastric glands to secrete
pepsinogen, Hydrochloric acid activates pepsinogen to
9. The small intestine, which is about 20 feet long, is so
named because its diameter is much smaller than that of the
large intestine. The small intestine has three regions, called
the duodenum, the jejunum, and the ileum
10. • Takes about 4 – 8 hrs to complete its journey.
• Mucosa (inner wall) – secretes several enzymes that acts
on the food.
• Where the pancreatic enzymes are emptied into.
• Digested nutrients are absorbed through intestinal walls.
• Absorbed materials cross the mucosa into the blood then
other parts of the body for storage or further chemical
11. The small intestine extends from the pyloric sphincter to the
ileocecal valve, where it empties into the large intestine. The
small intestine finishes the process of digestion, absorbs the
nutrients, and passes the residue on to the large intestine.
The liver, gallbladder, and pancreas are accessory organs of
the digestive system that are closely associated with the small
The most important factor for regulating secretions in the
small intestine is the presence of chyme. This is largely a local
reflex action in response to chemical and mechanical irritation
from the chyme and in response to distention of the intestinal
wall. This is a direct reflex action, thus the greater the amount
of chyme, the greater the secretion.
• The duodenum is the first and shortest segment of the
small intestine. It receives partially digested food (known
as chyme) from the stomach and plays a vital role in the
chemical digestion of chyme in preparation for absorption
in the small intestine. Many chemical secretions from the
pancreas, liver and gallbladder mix with the chyme in the
duodenum to facilitate chemical digestion.
• Located inferior to the stomach, the duodenum is a 10-12
inch (25-30 cm) long C-shaped, hollow tube. The
duodenum is a part of the gastrointestinal tract, attached
to the pyloric sphincter of the stomach on its superior end
and to the jejunum of the small intestine on its inferior end
14. After being stored and mixed with hydrochloric acid in the
stomach for about 30 to 60 minutes, chyme slowly enters
the duodenum through the pyloric sphincter. Next,
Brunner’s glands in the mucosa of the duodenum secrete
alkaline mucus containing a high concentration of
bicarbonate ions to neutralize the hydrochloric acid present
in the chyme. This alkaline mucus both protects the walls of
the duodenum and helps the chyme to reach a pH
conducive to chemical digestion in the small intestine.
15. Upon reaching the ampulla of Vater in the middle of the
duodenum, chyme is mixed with bile from the liver and
gallbladder, as well as pancreatic juice produced by the
pancreas. These secretions complete the process of chemical
digestion that began in the mouth and stomach by breaking
complex macromolecules into their basic units. Bile produced in
the liver and stored in the gallbladder acts as an emulsifier,
breaking lipids into smaller globules to increase their surface
area. Pancreatic juice contains many enzymes to break
carbohydrates, lipids, proteins and nucleic acids into their
16. It secretes bile which is stored in the gall bladder.
Bile breaks down fats into tiny droplets through
• Regulates sugar/glucose
• Storage of blood
• Generation of heat
17. • The gallbladder is a pear-shaped
sac that is attached to the visceral
surface of the liver by the cystic
duct. The principal function of the
gallbladder is to serve as a storage
reservoir for bile.
Is a spongy, tube-shaped organ about 6 inches long. It is
located in the back of the abdomen, behind the stomach.
The pancreas produces a juice containing several enzymes
that break down carbohydrates, fats, and proteins in food.
including trypsinogen, chymotrypsinogen, elastase,
carboxypeptidase, pancreatic lipase, nucleases and
amylase.The pancreas delivers digestive juice to the small
intestine through small tubes called ducts.
19. Pancreatic juice is alkaline in nature due to the high
concentration of bicarbonate ions. Bicarbonate is useful in
neutralizing the acidic gastric acid, allowing for effective
Pancreatic juice secretion is regulated by the hormones
secretin and cholecystokinin, which is produced by the
walls of the duodenum
The jejunum is the second part of the
small intestine. After food is broken down
in the duodenum, it moves to the
jejunum, where the inside walls absorb
the food's nutrients. The inside walls of
the jejunum have many circular folds,
which make its surface area large
enough to absorb all of the nutrients that
the body needs.
22. • Amino acids and simple sugars like glucose and
fructose diffuse through thin Epithelial cells into
the blood capillaries.
•Fatty acids and glycerol
enter the Lacteal into
the lymphatic system
then finally into the blood
system through the
The ileum is the third part of
the small intestine. It absorbs
bile acids, which are returned
to the liver to be made into
more bile, then stored in the
gallbladder for future use in
the duodenum. The ileum
also absorbs vitamin B12,
which the body uses to make
nerve cells and red blood
24. The large intestine
The large intestine takes about 16 hours to finish the digestion
of the food. It removes water and any remaining absorbable
nutrients from the food before sending the indigestible matter to
the rectum. The colon absorbs vitamins that are created by the
colonic bacteria, such as vitamin K, vitamin
B12, thiamine and riboflavin. It also compacts feces, and
stores fecal matter in the rectum until it can be discharged via
the anus in defecation.
The large intestine also secretes K+
and Cl-.Chloride secretion increases in
cystic fibrosis. Recycling of various
nutrients takes place in colon.
25. • By the time the chyme has reached this tube,
most nutrients and 90% of the water have been
absorbed by the body. At this point some
electrolytes like sodium, magnesium,
and chloride are left as well as indigestible parts of
• As the chyme moves through the large intestine,
most of the remaining water is removed, while the
chyme is mixed with mucus and bacteria (known
as gut flora), and becomes feces.
• The ascending colon receives fecal material as a
liquid. The muscles of the colon then move the
watery waste material forward and slowly absorb all
the excess water. The stools gradually solidify as
they move along into the descending colon.