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MOUTH
Turns food into small
pieces with the help ESOPHAGU
of the teeth and S
Carries food from
saliva.
the mouth to the
stomach.
 Liver
Produces bile, breaks
down fat, and removes
toxins STOMACH
Gallbladder Churns and
Stores the Pancreas mixes food
bile the liver Produces enzymes with gastric
produces that help break juice
down food
 SMALL
INTESTINES
Digests and absorbs
proteins, fats, and
carbohydrates
LARGE
INTESTINES
Absorbs salt and water from
food, leaving a soft mass
called stool
 RECTUM
ANUS Acts as the stool's
temporary storage
Where stool exits
the body
 DIGESTIO
refers N
to the breakdown of food into
smaller components that can be
absorbed into the bloodstream.
 2
TYPES
MECHANICAL DIGESTION
-occurs in the mouth when food is physically broken up
into smaller pieces
CHEMICAL DIGESTION
-takes place in the gastrointestinal tract when the
digestive enzymes break down the food into small
molecules.
 Role of Digestion
Provide energy and necessary nutrients for bodily
processes such as:
-movement
-growth
-repair
-reproduction
 Mouth
Digestion in humans starts in the mouth where food is
chewed and broken down to smaller pieces for easier
digestion (mechanical digestion).
Initial chemical digestion starts also in the mouth. This
is carried out by molecules that speed up chemical
reactions called enzymes.
 Amylas
an enzyme present inesaliva helps break down
carbohydrates, which are large complex molecules, into
simple ones that can be used by the body.
 The Pharynx
The pharynx muscular walls function in the process of
swallowing, and it serves as a pathway for the
movement of food from the mouth to the esophagus.
The constrictive circular muscles of the pharynx’s outer
layer paly a big role in peristalsis.
 Peristalsis
A series of contractions will help propel ingested food
and drink down the intestinal tract safely.
The inner layer’s longitudinal muscles, on the other
hand, will widen the pharynx laterally and lift it
upward, thus allowing the swallowing of ingested food
and drink.
 Esophagu
s
about 20 cm long. Its functions include secreting mucus
and moving food from the throat to the stomach using
muscle movement (peristalsis).
 Stomach
a J-shaped muscular bag that stores the food and breaks
it down into tiny pieces. It mixes food with gastric
juices that contain enzymes to break down proteins and
lipids.
Hydrochloric acid in the stomach kills bacteria. Food
found in the stomach is called chyme.
 Small Intestine
is a little over 5 meters long and lies in the abdominal
cavity surrounded by the large intestine.
Chemical digestion of food is completed and most of
the absorption of nutrients takes place.
 Small Intestine
Lining of the intestine walls has finger like projections
called villi, to increase surface area.
 3 sections of the small intestine
DUODENUM
-the first part of the small intestine.
-connects to the stomach.
-Helps to further digest food coming from the stomach.
-absorbs nutrients (vitamins, minerals, carbohydrates,
fats and proteins) and water.
 3 sections of the small intestine
JEJUNUM
-middle section of the small intestine and is about 2
meters long.
-its main function is absorption of important nutrients
such as sugar, fatty acids, and amino acids.
3 sections of the small intestine
ILEUM
-connects to the large intestine
-helps further digest and absorb nutrients.
 Large Intestine
-absorption of water continues until the familiar
semisolid consistency of feces is achieved.
Mineral salts, vitamins and some drugs are also
absorbed.
-it is about 5 feet long and is divided into 5 segments.
 Large Intestine
-absorption of water continues until the familiar
semisolid consistency of feces is achieved.
Mineral salts, vitamins and some drugs are also
absorbed.
-it is about 5 feet long and is divided into 5 segments.
 Rectum and Anal Canal
Rectum
-is a straight 8 inch chamber that connects the colon to
the anus.
-its job is to receive stool from the colon, let you know
that there is stool to be evacuated and to hold the stool
until evacuation happens.
 Rectum and Anal Canal
When anything (gas or stool) comes into the rectum,
sensors send a message to the brain. The brain then
decides if the rectal contents can be released or not.
 Rectum and Anal Canal
Anus
-the last part of the digestive tract.
-it is a 2 inch long canal consisting of the pelvic floor
muscles and the two anal sphincters ( internal and external).
The lining of the upper anus is able to detect rectal contents.
It lets you know whether the contents are liquid, gas or
solid.
Accessory Organs of the Human
Digestive System
 Teeth
• responsible for the mechanical digestion of food on
the mouth- mastification.
Classification of teeth
-incisors, the chisel-shaped frontal teeth, specialized in
cutting. The fang like teeth are called canine and are
best for piercing and tearing.
-premolars and molars, teeth responsible for crushing
and grinding.
 Salivary Glands
-present in the oral cavity and pour their secretions into
the mouth.
Saliva is combined secretions from the salivary glands
and the small mucus- secreting glands of the lining of
the oral cavity.
About 1.5 liters of saliva is produced daily. Salivary
glands and saliva work ass chemical digestion of
carbohydrates.
 Saliva contains the enzyme amylase that begins the
breakdown of complex sugars, reducing them to the
disaccharide maltose. Dry food entering the mouth is
moistened and lubricated by saliva before it can be
made into a bolus ready for swallowing.
 The Pancreas
-secretes enzymes that helps break down substances for
proper digestion and absorption.
trypsin and chymotrypsin-digest proteins
amylase- digest carbohydrates
lipase- digest fats
 The Liver
-largest gland in the body.
The liver directly affects digestion by producing bile.
Bile helps digest fat.
 The Gallbladder
-a small, thin-walled sac located beneath the liver.
This organ stores and concentrates the bile produced in
the liver which will be then used in digestion of fats
and lipids.
HOW DIGESTION WORKS?
Digestion is the process by which the gastrointestinal
system retrieves important nutrients for the body and
chemically changes the unused food into waste.
The first step is mastification or chewing of food in the
mouth. Saliva initiates digestion and changes the
chewed food into a soft mass called bolus. Bolus is
made slippery by saliva, making it easier to be
swallowed and slip down the back of the throat and
esophagus.
 Hydrochloric acid is released inside the stomach that
causes to break down large food molecules into smaller
ones and liquefies the bolus. The liquefied bolus, now
called chime, then enters the first section of the small
intestine (duodenum). It is here that enzymes released
from the pancreas, liver and gallbladder further
breakdown chime into elements that can be easily
absorbed and used by the body.
The small intestine is lined with a heavily folded inner
mucosa and small fingerlike projections called villi.
The villi permit digested food to enter the bloodstream.
All nutrients and vitamins are absorbed here in the
small intestine. Chime can travel through up to 20 feet
of small intestine before it passes through the large
intestine.
 A very little digestion occurs in the large intestine.
Waste is formed from the deposits of undigested food
in the large intestine. As the waste passes through the
large intestine, it becomes more and more solid because
of the water that is continuously being reabsorbed from
the waste. Waste deposits in the rectum, or end of the
large intestine, until the brain signals for it to be
expelled from the body.