2. WHAT IS DIGESTION?
The chemical breakdown of complex
biological molecules into their component
parts is termed as digestion.
The main functions of digestion is to:
• Produce various chemicals to break
down the food.
• Filtering out harmful substances.
• Getting rid of solid wastes.
3. THE DIGESTIVE TRACK
The Digestive track is a long muscular tube
which have many sections and areas. It begins
with the Mouth and ends with
Anus.
The digestive track consists of:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
5. What happens in mouth?
As soon as the food particles enters our mouth,
the digestion process begins. As discussed earlier
our buccal cavity consists of teeth, tongue and saliva.
Teeth: it helps in the mastification of food i.e.
chewing and grinding of food is done with the
help of teeth. The teeth helps in breaking down
food into smaller particles so that digestion can take place easily.
Saliva: saliva is a watery liquid secreted into the mouth by
salivary glands situated below our tongue. The saliva consists of
some special enzymes which helps in the process of digestion. The
enzyme named salivary amylase helps in breaking down starch into
simple sugars. It also contains mucus which helps in softening of
food.
Tongue: It is able to guide and maintain food between the upper
and lower teeth until mastication is complete.
6. After being chewed and swallowed, the food enters the
esophagus. The esophagus is a long tube that runs from the
mouth to the stomach. It uses rhythmic, wave-like muscle
movements (called peristalsis) to force food from the throat
into the stomach. This muscle movement gives us the ability
to eat or drink even when we're upside-down.
7.
8. What really happens in stomach?
The stomach is a muscular, hollow, dilated part of
the digestive system which functions as an
important organ of the digestive tract. From the
mouth, the food is taken to the stomach through
the food-pipe or esophagus. The stomach is a
large organ which expands when food enters it.
The muscular walls of the stomach help in mixing the
food thoroughly with the help of some digestive juices.
These digestion functions are taken care of by
the gastric glands present in the wall of the
stomach. These release :
• HYDROCHLORIC ACID ( H C L )
• PEPSIN
• MUCUS
9. FUNCTIONS OF GASTRIC JUICES
Pepsin: It is a digestive enzyme which helps
in the digestion of protein. It needs an acidic
medium for functioning.
Hydrochloric acid ( HCL ): It provides an acidic
medium for enzyme pepsin for conversion of
proteins into peptides. It even kills the harmful
bacteria that comes along with the food.
Mucus: It lubricates the food and protects
the gastric lining from strong digestive juices.
10. SMALL INTESTINE
After the stomach the food reaches the small
intestine. The small intestine is a coiled tube
beneath the stomach. It is about 20 feet long
but is known as small intestine because it’s
diameter is smaller than the large intestine.
The small intestine has three regions namely:
• Duodenum
• Jejunum
• Ileum
Together with the esophagus, large intestine, and the
stomach, it forms the gastrointestinal tract. In living
humans, the small intestine alone measures about 6 to 7
meters long.
11. ABSORBTION IN SMALL INTESTINE
The internal walls of the small intestine are
covered in finger-like tissue called villi. Each of
these villi is covered in even smaller finger-like
structures called microvilli. These villi and
microvilli increase the surface area available
for the absorption of nutrients. Each villus transports
nutrients to a network of capillaries and fine
lymphatic vessels called lacteals close to its surface.
In the small intestine food that has already been
broken down by chewing and stomach enzymes
is further degraded by additional enzymes. Some of
these chemicals are secreted in the lumen (the hollow area in
the middle of the intestine), but others are transported to the
intestine from other organs such as the pancreas and liver.
12. LARGE INTESTINE
The large intestine is the last part of the digestive system—the
final stage of the alimentary canal—in vertebrate
animals. Its function is to absorb water from
the remaining indigestible food matter, and then
to pass this useless waste material from the body.
The large intestine consists of the cecum and colon. It starts
in in the right iliac region of the pelvis, just at or
below below the right waist, where it is joined to the
bottom bottom end of the small intestine. From here it
continues continues up the abdomen, then across the
of the abdominal cavity, and then it turns
down, continuing to its endpoint at the anus.
The large intestine is about 1.5 meters (4.9 ft) long, which is
about one-fifth of the whole length of the intestinal canal. Waste
from large intestine is pushed into the expanded portion (rectum).
13. Accessory organs
• These are those organs which are not in the
digestive track but helps in digestion.
• Example of such organs are:
Salivary gland Liver Pancreas Gall Bladder
Though these organs are not present in the digestive track,
they actually play a major role in the process of digestion.
They produce or store enzymes that helps in digestion.
14. FUNCTION OF LIVER
Liver is the largest gland of the human body.
It is located in the upper hand right portion of
abdominal cavity. The liver, a dark reddish brown organ has
multiple functions.
FUNCTIONS:
• It secretes bile (a watery greeny substance ) which is stored in
the gall bladder. Bile breaks down large globules of fats into
smaller globules through emulsification.
• Production of certain protein for blood plasma
• Store and release glucose as needed
• Conversion of harmful ammonia to urea
• Regulating blood clotting
• Detoxification
15. FUNCTION OF PANCREAS
Pancreas is a gland organ that is located
below the abdomen. It produces important
enzymes and hormones that help break
down food. The pancreas has endocrine function because it
release juices directly into the blood stream. It is also an
exocrine gland because it secretes pancreatic juice in the
duodenum. The pancreatic juice contains lipase, trypsin
and pancreatic amylase for digestion of lipids, proteins and
starch.
When food leaves the stomach, it is acidic
in nature. Thus in nature. Thus in order to make the food
alkaline pancreatic juices act on it.
16. FUNCTION OF GALL BLADDER AND
SALIVARY GLAND
• SALIVARY GLAND
The salivary glands are located near the mouth.
They produce and secrete saliva, a substance
that helps in moistening the food. The salivary
gland produces salivary amylase which helps in breaking
down of sugar into starch.
• GALL BLADDER
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.
Bile is a yellowish-green fluid produced by liver cells.
19. DIGESTIVE SYSTEM OVERVIEW
The human digestive system is a complex series of organs and
glands that processes food. In order to use the food we eat,
our body has to break the food down into smaller molecules.
The digestive process begins in the mouth. Food is partially
broken down by the process of chewing and by the chemical
action of salivary enzymes. After being chewed, crunched and
swallowed, the food enters the esophagus. The esophagus is
a long tube that runs from the mouth to the stomach. It uses
rhythmic, wave-like muscle movements (called peristalsis) to
force food from the throat into the stomach. The stomach is a
large, sack-like organ that churns the food and bathes it in a very strong acid
(gastric acid). Food in the stomach that is partly digested and mixed with stomach
acids is called chyme. After being in the stomach, food enters the small intestine. In
the small intestine, bile (produced in the liver and stored in the gall bladder),
pancreatic enzymes, and other digestive enzymes produced by the inner wall of
the small intestine help in the breakdown of food. After passing through the
small intestine, food passes into the large intestine. In the large intestine, some of
the water and electrolytes (chemicals like sodium) are removed from the food. Solid
waste is then stored in the rectum until it is excreted via the anus. This finally ends the
process of digestion.
