The document summarizes the key parts and functions of the digestive system. It describes the esophagus as the muscular tube connecting the mouth to the stomach. The stomach acts as a storage tank that contains acids and enzymes to further digest food. The small intestine, including the duodenum, jejunum and ileum, absorbs nutrients from food. The large intestine, including the ascending, transverse and descending colon, absorbs water and converts waste into feces. The rectum temporarily stores feces until defecation, while the anus is the opening through which feces leaves the body. Other organs like the liver, pancreas and gallbladder produce enzymes and bile to aid in digestion.

1. THE PARTS OF THE DIGESTIVE SYSTEM
THE OESOPHAGUS
The oesophagus is also known as the gullet or food pipe. It’s part of the digestive system,
which is sometimes called the gastro-intestinal tract. The oesophagus is a long, muscular
tube that connects your mouth to your stomach. When you swallow food, the walls of the
oesophagus squeeze together. This moves the food down the oesophagus to the stomach.
The oesophagus has four layers:
 The mucosa: the inner layer, which is moist to help food pass smoothly into the
stomach.
 The submucosa: this contains glands that produce mucus (phlegm), which keeps the
oesophagus moist.
 The muscularis: the muscle layer, which pushes food down to the stomach.
 The adventitia: the outer layer, which attaches the oesophagus to nearby parts of
the body.

2. THE STOMACH
The stomach is a muscular sac that is located on the left side of the abdominal cavity. In an
average person, the stomach is about the size of their two fists placed next to each other.
This major organ acts as a storage tank for food so that the body has time to digest large
meals properly. The stomach also contains hydrochloric acid and digestive enzymes that
continue the digestion of food that began in the mouth.
The stomach has four parts:
 The cardiac: is the first portion of the stomach and is where food content passes
from the oesophagus into the stomach. The acids and enzymes referred to as the
gastric juices are manufactured in the cardiac.
 The fundus: stores undigested food and also the gases released from the chemical
digestion of food.
 The body of the stomach or the corpus: is the largest of the four parts that make up
the stomach. And this is where the bulk of the partial digestion occurs.
 The pylorus is connected to the beginning of the small intestine. The contents of the
stomach move into the small intestine via the pyloric canal.

3. SMALL INTESTINE
Small Intestine
The small intestine is part of the lower gastrointestinal tract. It is located just inferior
to the stomach and takes up most of the space in the abdominal cavity. The entire
small intestine is coiled like a hose and the inside surface is full of many ridges and
folds. These folds are used to maximize the digestion of food and absorption of
nutrients.
Different parts of the small intestine:
 The duodenum is the first and shortest segment of the small intestine. It receives
partially digested food from the stomach and plays a vital role in the chemical
digestion of chime in preparation for absorption in the small intestine.
 The jejunum: jejunum is the middle segment of the small intestine found between
the duodenum and the ileum. Most of the nutrients present in food are absorbed by
the jejunum before being passed on to the ileum for further absorption
 Ileum: ileum is the last part of the three part tube that makes up the small intestine.
It is where the remaining nutrients are absorbed before moving into the large
intestine.

4. LARGE INTESTINE
The large intestine is the final section of the gastrointestinal tract that performs the vital
task of absorbing water and vitamins while converting digested food into faeces. Although
shorter than the small intestine in length, the large intestine is considerably thicker in
diameter, thus giving it its name.
The ascending colon is one of the four major regions of the colon, which is itself one of the
parts of our large intestine. The ascending colon carries faeces from the cecum superiorly
along the right side of our abdominal cavity to the transverse colon. In the ascending colon,
bacteria digest the transitory faecal matter in order to release vitamins.
The descending colon is a segment of the large intestine and is the third and penultimate
segment of the colon. It transports faeces from the transverse colon inferiorly along the left
side of the abdominal cavity to the sigmoid colon. Faces passing through the descending
colon are stored until they are ready to be eliminated from the body.
The transverse colon is the longest region of the colon and is located between the ascending
colon and descending colon. It is named for the fact that it crosses the abdominal cavity
transversely from the right side to left side just below the stomach. Much of the absorption
and faeces formation of the colon takes place in the transverse colon, making it a very
important region of the digestive system.

5. RECTUM
The rectum is the concluding part of the large intestine that terminates in the anus. The
average length of the human rectum may range between 10 and 15 cm. Its diameter can be
compared to that of the sigmoid colon (the part of the large intestine nearest the rectum) at
its onset. However, it becomes larger near the anus, where it forms the rectal ampulla. The
Key role of the rectal ampulla is to act as a temporary storehouse for faeces. The expansion
of the rectal walls causes the stretch receptors within the walls to stimulate the urge to
defecate. If the defecation process is delayed, it may result in constipation. When the
storage site becomes full, the intrarectal pressure causes the anal canal walls to dilate and
expand. This results in the faeces entering the canal.

6. ANUS
The anus is the opening at the far end of the digestive tract through which stool leaves the
body. The anus is formed partly from the surface layers of the body, including the skin, and
partly from the intestine. The anus is lined with a continuation of the external skin. A
muscular ring (anal sphincter) keeps the anus closed until the person has a bowel
movement.
LIVER
The liver is a large, meaty organ that sits on the right side of the belly. Weighing about 3
pounds, the liver is reddish-brown in colour and feels rubbery to the touch. Normally you
can't feel the liver, because it's protected by the rib cage. The liver has two large sections,
called the right and the left lobes. The gallbladder sits under the liver, along with parts of
the pancreas and intestines. The liver and these organs work together to digest, absorb, and
process food. 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.

7. PANCREAS
The pancreas is a glandular organ in the digestive systemand endocrine system of
vertebrates. In humans, it is located in the abdominal cavity behind the stomach. It is an
endocrine gland producing several important hormones, including insulin, glucagon and
pancreatic polypeptide which circulate in the blood. The pancreas is also a digestive organ,
secreting pancreatic juice containing digestive enzymes that assist digestion and absorption
of nutrients in the small intestine. These enzymes help to further break down the
carbohydrates, proteins, and lipids in the chime.
GALL BLADDER
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. In

8. response to signals, the gallbladder squeezes stored bile into the small intestine through a
series of tubes called ducts. Bile helps digest fats, but the gallbladder itself is not essential.
Removing the gallbladder in an otherwise healthy individual typically causes no observable
problems with health or digestion yet there may be a small risk of diarrhoea and fat
malabsorption
.