The document provides an overview of the human digestive system, including its main components and functions. It describes the digestive tract which processes food from the mouth through the esophagus, stomach, and intestines. It also outlines the accessory organs that help with digestion, such as the liver, gallbladder and pancreas. The six main functions of the digestive system are ingestion, mechanical and chemical digestion, movement of food and waste, absorption of nutrients, and elimination of waste.

1. DIGESTIVE SYSTEM
Yoga Life Asanas and Meditation

3. • The digestive system includes the digestive tract
and its accessory organs, which process food into
molecules that can be absorbed and utilized by
the cells of the body.
• Food is broken down, bit by bit, until the
molecules are small enough to be absorbed and
the waste products are eliminated.
• The digestive tract, also called the alimentary
canal or gastrointestinal (GI) tract, consists of a
long continuous tube that extends from the mouth
to the anus.
• It includes the mouth, pharynx, esophagus,
stomach, small intestine, and large intestine. The
tongue and teeth are accessory structures
located in the mouth.
• The salivary glands, liver, gallbladder, and
pancreas are major accessory organs that have a
role in digestion. These organs secrete fluids into
the digestive tract.

4. Food undergoes three types of processes in the body:
• Digestion
• Absorption
• Elimination
Digestion and absorption occur in the digestive tract.
After the nutrients are absorbed, they are available to all
cells in the body and are utilized by the body cells in
metabolism.

6. The digestive system prepares nutrients for
utilization by body cells through six activities, or
functions
Ingestion
The first activity of the digestive system is to take in food through
the mouth. This process, called ingestion, has to take place
before anything else can happen.
Mechanical Digestion
The large pieces of food that are ingested have to be broken into
smaller particles that can be acted upon by various enzymes. This
is mechanical digestion, which begins in the mouth with chewing
or mastication and continues with churning and mixing actions in
the stomach.

7. The digestive system prepares nutrients
for utilization by body cells through six
activities, or functions
Chemical Digestion
The complex molecules of carbohydrates, proteins, and
fats are transformed by chemical digestion into smaller
molecules that can be absorbed and utilized by the cells.
Chemical digestion, through a process called hydrolysis,
uses water and digestive enzymes to break down the
complex molecules. Digestive enzymes speed up the
hydrolysis process, which is otherwise very slow.
Movements
After ingestion and mastication, the food particles move
from the mouth into the pharynx, then into the
esophagus. This movement is deglutition or swallowing.
Mixing movements occur in the stomach as a result of
smooth muscle contraction. These repetitive contractions
usually occur in small segments of the digestive tract and
mix the food particles with enzymes and other fluids. The
movements that propel the food particles through the
digestive tract are called peristalsis. These are rhythmic
waves of contractions that move the food particles
through the various regions in which mechanical and
chemical digestion takes place.

8. The digestive system prepares nutrients for utilization by
body cells through six activities, or functions
Absorption
The simple molecules that result from chemical digestion
pass through cell membranes of the lining in the small
intestine into the blood or lymph capillaries. This process is
called absorption.
Elimination
The food molecules that cannot be digested or absorbed
need to be eliminated from the body. The removal of
indigestible wastes through the anus, in the form of feces, is
defecation or elimination.

9. • ,

10. • ,

11. Regions of the Digestive System
• At its simplest, the digestive system
is a tube running from mouth to
anus. Its chief goal is to break down
huge macromolecules (proteins, fats
and starch), which cannot be
absorbed intact, into smaller
molecules (amino acids, fatty acids
and glucose) that can be absorbed
across the wall of the tube, and into
the circulatory system for
dissemination throughout the body.

12. Regions of the digestive system can be divided into two main parts:
the alimentary tract and accessory organs.
1. Alimentary Tract of the Digestive
System
Mouth
Pharynx & Esophagus
Stomach
Small and Large Intestine
2. Accessory Organs of the Digestive
System
Salivary Glands
Liver
Gallbladder
Pancreas

15. Mouth
The mouth, or oral cavity, is the first part of the digestive
tract. It is adapted to receive food by ingestion, break it
into small particles by mastication, and mix it with saliva.
The lips, cheeks, and palate form the boundaries. The oral
cavity contains the teeth and tongue and receives the
secretions from the salivary glands

16. Pharynx & Esophagus
• Pharynx
Food is forced into the pharynx by the tongue. When
food reaches the opening, sensory receptors
respond and initiate an involuntary swallowing reflex.
This reflex action has several parts. The epiglottis
drops downward to prevent food from entering the
larynx and trachea in order to direct the food into the
esophagus. Peristaltic movements propel the food
from the pharynx into the esophagus.
• Esophagus
The esophagus is a collapsible muscular tube that
serves as a passageway between the pharynx and
stomach. The mucosa has glands that secrete mucus
to keep the lining moist and well lubricated to ease
the passage of food. Upper and lower esophageal
sphincters control the movement of food into and out
of the esophagus. The lower esophageal sphincter is
sometimes called the cardiac sphincter and resides at
the esophagogastric junction.

17. The stomach, which receives food from the esophagus, is in the
upper left quadrant of the abdomen. The stomach muscles
contract periodically, churning food to enhance digestion. The
pyloric sphincter is a muscular valve that opens to allow food to
pass from the stomach to the small intestine. The stomach can
expand or contract depending upon the amount of food
contained within it. When contracted, the interior walls form
numerous folds (rugae), which disappear when the walls are
distended. The thick mucous-membrane lining of the walls is
densely packed with small gastric glands; these secrete a
mixture of enzymes and hydrochloric acid that partly digest
proteins and fats.
Stomach,

18. Stomach,
• The stomach muscles are rarely inactive. Upon entry of
food, they relax briefly, then begin to contract. Periodic
contractions churn and knead food into a semifluid
mixture called chyme; rhythmical pumping (peristaltic)
waves move food toward the pylorus and small
intestine.
• The absorption of food, water, and electrolytes by the
stomach is practically negligible, but iron and highly fat-
soluble substances such as alcohol and some drugs
are absorbed directly.
Stomach Emptying
Relaxation of the pyloric sphincter allows chyme to pass
from the stomach into the small intestine. The rate of
which this occurs depends on the nature of the chyme and
the receptivity of the small intestine.

19. • The intestines are a long, continuous tube running from
the stomach to the anus. Most absorption of nutrients
and water happen in the intestines. The intestines
include the small intestine, large intestine, and rectum.
• The small intestine (small bowel) is about 20 feet long
and about an inch in diameter. Its job is to absorb most
of the nutrients from what we eat and drink. Velvety
tissue lines the small intestine, which is divided into the
duodenum, jejunum, and ileum.
• The large intestine (colon or large bowel) is about 5
feet long and about 3 inches in diameter. The colon
absorbs water from wastes, creating stool. As stool
enters the rectum, nerves there create the urge to
defecate.
Fun Fact about Small & Large
Intestine

20. Small & Large Intestine
Small 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 intestine. The small intestine is
divided into the duodenum, jejunum, and ileum. The small
intestine follows the general structure of the digestive tract
in that the wall has a mucosa.
• The absorptive surface area of the small intestine is
increased by plicae circulares, villi, and microvilli.
• The most important factor for regulating secretions in
the small intestine is the presence of chyme.

22. Small & Large Intestine
Large Intestine
The large intestine is larger in diameter than the small
intestine. It begins where the ileum enters the large
intestine and ends at the anus. The large intestine
consists of the colon, rectum, and anal canal. Unlike the
small intestine, the large intestine produces no digestive
enzymes. Chemical digestion is completed in the small
intestine before the chyme reaches the large intestine.
Functions of the large intestine include the absorption of
water and electrolytes and the elimination of feces.

23. Small & Large Intestine
The colon extends from the cecum up the right side of the abdomen,
across the upper abdomen, and then down the left side of the
abdomen, finally connecting to the rectum. The colon has four parts:
the ascending colon and transverse colon, which absorb water and
salts; and the descending colon, which holds the resulting waste.
Bacteria in the colon help to digest the remaining food products.
Ascending Colon: The ascending colon is on the right side of the
abdomen, which starts from the cecum to the liver (hepatic flexure).
Transverse Colon: The transverse colon starts from the hepatic
flexure (the turn of the colon by the liver) to the splenic flexure (the
turn of the colon by the spleen).
Descending Colon: The descending colon starts from the splenic
flexure to the beginning of the sigmoid colon.
Sigmoid Colon: The sigmoid colon starts after the descending
colon and before the rectum.

24. Small & Large Intestine
Rectum and Anus,
The anus is the opening at the end of the digestive tract
where stool leaves the body. The rectum is the section of
the digestive tract above the anus where stool is held
before it passes out of the body through the anus.
• The rectum is a chamber that begins at the end of the
large intestine, immediately following the sigmoid
colon, and ends at the anus. Ordinarily, the rectum is
empty because stool is stored higher in the descending
colon. Eventually, the descending colon becomes full,
and stool passes into the rectum, causing an urge to
move the bowels (defecate).

25. Accessory Organs
The salivary glands, liver, gallbladder, and pancreas are not part of the
digestive tract, but they have a role in digestive activities and are
considered accessory organs.
Salivary Glands,
The salivary glands secrete saliva into the oral cavity, where it is mixed
with food. Saliva contains water, mucus, and enzyme amylase.
Functions of saliva include the following:
• It has a cleansing action on the teeth.
• It moistens and lubricates food during chewing and swallowing.
• It dissolves certain molecules so that food can be tasted.
• It begins the chemical digestion of starches through the action of
amylase, which breaks down polysaccharides into disaccharides.

26. Accessory Organs
Liver,
It is the largest gland in the body. The liver's main job is to filter the
blood coming from the digestive tract, before passing it to the rest of
the body. The liver also detoxifies chemicals and metabolizes drugs.
As it does so, the liver secretes bile that ends up back in the intestines.
The liver also makes proteins important for blood clotting and other
functions.
• This organ is vital to the body’s metabolic functions and immune
system. Without a functioning liver, a person cannot survive.
• The liver stores vitamins as well as minerals such as copper and
iron, releasing them if the body needs them. The liver also helps to
break down fats in a person’s diet. It either stores fats or releases
them as energy.

27. Gallbladder,
The gallbladder is a small pouch that sits just under the liver.
The gallbladder stores bile produced by the liver. After meals,
the gallbladder is empty and flat, like a deflated balloon. Before
a meal, the gallbladder may be full of bile and about the size of a
small pear. The gallbladder stores bile, a combination of fluids,
fat, and cholesterol. Bile helps break down fat from food in your
intestine. The gallbladder delivers bile into the small intestine.
This allows fat-soluble vitamins and nutrients to be more easily
absorbed into the bloodstream.
Accessory Organs

28. Accessory
Organs
Pancreas,
The pancreas is an organ located in the
abdomen. It plays an essential role in
converting the food we eat into fuel for the
body's cells. The pancreas has two main
functions: an exocrine function that helps in
digestion and an endocrine function that
regulates blood sugar.
• A healthy pancreas produces the correct
chemicals in the proper quantities, at the
right times, to digest the foods we eat.

29. Review: Introduction to the Digestive System
Here is what we have learned from Introduction to the Digestive System:
• The digestive tract includes the digestive tract and its accessory organs, which
process food into molecules that can be absorbed and utilized by the cells of the
body.
• Food undergoes three types of processes in the body: digestion, absorption, and
elimination.
• The digestive system prepares nutrients for utilization by body cells through six
activities, or functions: ingestion, mechanical digestion, chemical digestion,
movements, absorption, and elimination.
• The wall of the digestive tract has four layers or tunics: mucosa, submucosa,
muscular layer, and serous layer or serosa.
• Regions of the digestive system can be divided into two main parts: alimentary tract
and accessory organs.
• The alimentary tract of the digestive system is composed of the mouth, pharynx,
esophagus, stomach, small and large intestines, rectum and anus.
• Associated with the alimentary tract are the following accessory organs: salivary
glands, liver, gallbladder, and pancreas.