Anatomy of GI Tract with special reference to anatomy and functions of stomach, ( Acid production in the stomach, regulation of acid production through parasympathetic nervous system, pepsin role in protein digestion) small intestine and large intestine, anatomy and functions of salivary glands, pancreas and liver, movements of GIT, digestion and absorption of nutrients and disorders of GIT.

1. Digestive system
Miss. Gayatri K. Bahatkar

2. Human digestive system
 The digestive system of the human body comprises a group of organs working together
to convert food into energy for the body. Anatomically, the digestive system is made up
of the gastrointestinal tract, along with accessory organs such as the liver, pancreas and
gallbladder. The hollow organs that make up the gastrointestinal tract (GI tract) include
the mouth, stomach, oesophagus, small intestine and large intestine that contains the
rectum and anus.
 Human Digestive System and Nutrition involve the intake of food by an organism and
its utilization for energy. This is a vital process which helps living beings to obtain their
energy from various sources. The food which we eat undergoes much processing before
the nutrients present in them are utilized to generate energy. This processing is known as
digestion. Humans and other animals have specialized organs and systems for this
process.
 The digestion process involves the alimentary canal along with various accessory organs
and organ systems. In humans, the process is quite simple due to our monogastric
nature. This means that we have a one-chambered stomach, unlike other animals such as
cows, which have four chambers.

3. Diagram Of The Human Digestive System

5. Parts of the Human Digestive System
 The digestive system of the human body comprises a group of organs that work
together in converting food into energy and other basic nutrients to power the body.
The food we take in is digested and utilized by our body, and the unused parts of the
food are defecated.
 The digestive system of the human body is the sum of the gastrointestinal tract
(GIT; also called alimentary canal) and accessory organs (tongue, liver, pancreas,
etc.). These two parts together help in the digestion process.
 The alimentary canal is the long tube through which the food that we eat is passed.
It begins at the mouth (buccal or oral cavity), passes through the pharynx,
oesophagus or food pipe, stomach, small intestines, large intestines, rectum and
finally ends at the anus. The food particles gradually get digested as they travel
through various compartments of the alimentary canal.
 Accessory organs are organs which participate in the digestion process but are not
actually a part of GIT. They stimulate the digestion by releasing certain enzymes
that help in breaking down the food.
 Let us have a detailed look at the digestive system of the human body, along with its
parts and functions:

6. Mouth
 Food starts its journey from the mouth or the oral cavity. There are many other organs that
contribute to the digestion process, including teeth, salivary glands, and tongue. Teeth are
designed for grinding food particles into small pieces and are moistened with saliva before
the tongue pushes the food into the pharynx.
Pharynx
 A fibromuscular y-shaped tube attached to the terminal end of the mouth. It is mainly
involved in the passage of chewed/crushed food from the mouth through the oesophagus. It
also has a major part in the respiratory system, as air travels through the pharynx from the
nasal cavity on its way to the lungs.
Oesophagus
 This is a muscular tube that connects the pharynx, which is a part of an upper section of the
gastrointestinal tract. It supplies swallowed food along with its length

7.  Stomach
 It serves as a muscular bag which is situated towards the left side of the abdominal cavity,
beneath the diaphragm. This vital organ acts as a storage for the food and provides enough
time to digest meals. The stomach also produces digestive enzymes and hydrochloric acid
that maintains the process of digestion.
 Mucous: It is an aqueous secretion produced by the mucous membranes. It functions by
protecting the stomach lining and gastric pits from the acid, which is produced by the glands
to destroy the bacteria that entered along with the food particles.
 Digestive enzymes: They are the group of enzymes which functions by breaking down
polymeric macromolecules like biopolymers into their smaller and simpler substances.
 Hydrochloric acid: It is the digestive fluid formed by the stomach during the process of
digestion. It functions by destroying harmful microorganisms present in the food particles.

8. Small Intestine
The small intestine is a thin, long tube of about 10 feet long and a part of the lower
gastrointestinal tract. It is present just behind the stomach and acquires a maximum area
of the abdominal cavity. The complete small intestine is coiled and the inner surface
consists of folds and ridges.
Large Intestine
 This is a thick, long tube measuring around 5 feet in length. It is present just beneath
the stomach and wraps over the superior and lateral edges of the small intestine. It
absorbs water and consists of bacteria (symbiotic) that support the breakdown of
wastes to fetch small nutrients.
Rectum
 Waste products are passed into the end of the large intestine called the rectum and
eliminated out of the body as a solid matter called stool. It is stored in the rectum as
semi-solid faces which later exits from the body through the anal canal through the
process of defecation.

9.  Accessory Organs
Pancreas
 It is a large gland present just behind the stomach. It is short with its anterior connected
to the duodenum and posterior pointing towards the left part of the abdominal cavity.
The pancreas releases digestive enzymes to complete the process of chemical digestion.
Liver
 The liver is a roughly triangular, reddish-brown accessory organ of the digestive system
located to the right of the stomach. It produces bile, which helps in the digestion of fat
in the small intestine. The bile is stored and recycled in the gallbladder. It is a small,
pear-shaped organ which is located just next to the liver.

10. Digestion process
 The process of digestion begins from the mouth and ends in the small intestine – the large
intestines’ main function is to absorb the remaining water from the undigested food and
enable bacterial fermentation of materials that can no longer be digested.
 The alimentary canal or the gastrointestinal tract is a series of hollow organs and tubes
that begins from the mouth cavity and continues into the pharynx, through the stomach,
small intestines, large intestines, and finally ending at the anus. Food particles gradually
get digested as they travel through various compartments of the gastrointestinal tract.
The digestion process takes place in the following steps.
Ingestion
 The very first step involves mastication (chewing). The salivary glands, along with the
tongue, helps to moisten and lubricate food, before being pushed down into the food pipe.
Mixing and Movement
 It involves the process of lubricating and manipulating food and pushing it down the food
through the food pipe (using peristalsis), and into the stomach.

11. Secretion
 The stomach, small intestine, liver, and pancreas secrete enzymes and acids to aid the
process of digestion. It functions by breaking down food particles into simple
components and easily absorbable components.
Digestion
 The process of converting complex food particles into simpler substances in the
presence of enzymes and acids secreted by different digestive organs.
Absorption
 This process begins in the small intestine where most of the nutrients and minerals are
absorbed. The excess water in the indigestible matter is absorbed by the large
intestines.
Excretion
 The process of removing indigestible substances and waste by-products from the body
through the process of defecation.
 In a nutshell, the digestion process consists of the six following steps:
Ingestion ⇒Mixing and Movement ⇒ Secretion ⇒ Digestion ⇒Absorption ⇒Excretion

12. Anatomy and function of salivary gland
Anatomy of salivary glands
 The salivary glands secrete saliva into the mouth through ducts. This allows you to swallow and
chew food. Saliva can also protect you from oral and pharyngeal infections.
Salivary glands can be divided into two groups:
 Minor salivary glands
 Major salivary glands
Major salivary glands
 There are several large and important salivary glands, but the major ones are the largest and most
important of them. The largest amount of saliva is produced by these glands. The three major
salivary glands are the parotid gland, the submandibular gland, and the sublingual gland.
Parotid glands
 A parotid gland is one of the largest salivary glands. Their size is quite large, and they are located
behind the ear. A duct near your upper second molar allows saliva to flow into your mouth from
these glands. The shallow lobe and deep lobe of the parotid gland are separate. The facial nerve
lies between these two parts. This nerve controls a variety of facial functions, including the ability
to close your eyes, raise your brows, and smile.

13. Submandibular glands
 Submandibular glands are located below the Jaw and measure about the size of a walnut.
They produce saliva, which is then secreted From under the tongue into the mouth. The
Submandibular glands also have superficial and Deep lobes, like the parotid glands. They
are Located near:
• Nerves that help you smile, called marginal mandibular nerves
• You can move your lower lip because of the muscle called platysma muscle.
• The sensation in your togue is allowed by lingual nerve
 As your tongue moves, the hypoglossal nerve allows you to speak and swallow All of
these structures must be protected during treatment to avoid causing damage.
Sublingual glands
 One of the smallest of the main salivary glands is the sublingual gland. Under the tongue
and under the mouth floor are structures with almond-like shapes. These structures are
very rarely affected by tumors.

14. Minor salivary gland
 Small salivary glands are distributed all over the mouth and aerodigestive tract. It is
impossible to see these glands without a microscope because they are much smaller than
the major salivary glands. The majority of them are found in the walls of the mouth, on
the tongue, inside the cheeks, in the nose, in the sinuses, and in the larynx (voice box). It
is extremely rare for salivary glands to develop small tumors. The likelihood of
malignant tumors is higher than benign ones. The cancers that affect the roof of the
mouth are most likely to affect the minor salivary glands.
Functions of salivary glands
 Many different purposes are served by saliva. Saliva forms the finely packed ball of food
we roll in our mouths, as well as being the only secretion of our salivary glands. The
shape of this food ball allows it to pass through our alimentary canal with ease. Saliva
also has protective properties that make it an effective lubricant. While swallowing a
bolus, our saliva protects our mouths, teeth, and throats from bacteria. Aside from that, it
helps cleanse the mouth after meals and gives food a taste by converting fat into chemical
compounds.

17. Function Secrete saliva for initial phases of digestion and for protection and
lubrication of oral cavity
Types of glands Serous: parotid gland
Mucous: sublingual gland, minor salivary gland
Mixed: submandibular gland
Parotid gland Location: between ramus of mandible and sternocleidomastoid
muscle
Excretory duct: Stensen's duct (opens on the buccal wall at the
level of maxillary second molar)
Submandibular
gland
Location: beneath the tongue
Excretory duct: Wharton's duct (opens at sublingual papilla under
tongue)
Sublingual gland Location: beneath the sublingual fold
Excretory duct: multiple ducts that open along sublingual folds
Minor glands Location: bucca, labia, lingual mucosa, soft palate, hard palate
Clinical relations Cysts, inflammation, tumors

18. Anatomy and function of pancreas
 Location As a horizontal organ (15 cm long) lying obliquely across the posterior
abdominal wall, the pancreas is elongated and horizontal, lying between the L1 and L2
vertebral bodies. The oblique positioning of the pancreas makes it impossible to see the
entire organ in a single transverse section in the clinical context. During its travel through
the epigastric and left hypochondriac regions of the abdomen, the pancreas comes into
contact with several neighbouring structures. Besides the tail, the pancreas is located in the
retroperitoneum, behind the peritoneum, in the abdominal cavity.
 Parts It is now time to move on to exploring the anatomy of the pancreas, since you know
now where it is located. The body, the uncinate process, the neck, the body, and the tail
make up the five anatomical sections of the parenchymatous organ. Pancreas expands
medially at the head. The duodenum extends downwards and horizontally around the
pancreatic head. On the inferior surface of the head, we see the uncinate process, which
extends in a posterior direction towards the inferior mesenteric artery. In addition to the
head, the neck continues laterally from it, a short extension of around 2 cm that joins the
head to the body. As well as the origins of the hepatic portal vein and superior mesenteric
artery.

19.  Upon merging with the splenic vein, the superior mesenteric vein is present. Besides
their surfaces (anteroposterior and posterior) and borders (superior and inferior),
pancreatic bodies also have two integral lobes. The bursa of the L2 vertebra is located
anteriorly. A smaller bursa called the omental bursa is located near it. The pancreatic
body has several vessels and glands posterior to it, including the superior mesenteric
artery, left kidney vessels, left suprarenal gland, and left renal vessels. Lastly, the
pancreas is composed of the intraperitoneal tail. Splenic vessels run along the
splenorenal ligament and the splenic hilum is closely related to it.
 Ducts (Wirsung) in the pancreatic parenchyma: one in the tail and one in the head. The
hepatopancreatic duct, or ampulla of Vater, connects the liver with the pancreatic head.
On the major duodenal papilla, it opens into the duodenum descending part. Flow
through smooth muscle is controlled by the sphincter of Oddi through the ampulla of
Vater. Hepatopancreatic duct resorption is also prevented due to this device. A
sphincter sets up at the end of the main pancreatic and bile ducts to regulate the flow
of these fluids. Pancreatic accessory ducts are in addition to the main duct. In the
duodenum, in the descending part of the pancreatic neck, the main pancreatic duct
opens.

21. Functions of pancreas
 An exocrine gland runs the length of your pancreas. It produces enzymes that help
to break down food (digestion). Your pancreas releases the following enzymes:
 Lipase: Works with bile (a fluid produced by the liver) to break down fats.
 Amylase: Breaks down carbohydrates for energy.
 Protease: Breaks down proteins.
 When food enters your stomach:
 Your pancreas releases the pancreatic enzymes into small ducts (tubes) that flow
into the main pancreatic duct.
 Your main pancreatic duct connects with your bile duct. This duct transports bile
from your liver to your gallbladder.
 From the gallbladder, the bile travels to part of your small intestine called the
duodenum.
 Both the bile and the pancreatic enzymes enter your duodenum to break down
food.

22.  How does the pancreas affect blood sugar?
 The endocrine glands in your pancreas release hormones that control
blood sugar (glucose). These hormones are:
 Insulin: Reduces high blood sugar levels.
 Glucagon: Increases low blood sugar levels.
 Your body needs balanced blood sugar to help with your kidneys, liver
and brain. Your heart and circulatory system and nervous system also
need balanced levels of insulin and glucagon to function.

23. Anatomy and function of liver
Anatomy of liver
 In your belly (abdomen) top right corner is the liver. There is a cavity beneath the
diaphragm above the stomach, right kidney, intestines, and the right kidney. It
performs a variety of functions.
 Blood is supplied to the liver from two distinct sources:
 By way of the hepatic artery, blood is supplied with oxygen to the liver.
 Hepatic portal veins bring nutrient-rich blood into the liver.
 The liver consists of two lobes. Each lobe contains eight segments. Segments are
divided into thousands of small lobes (lobules). There are tiny ducts (tubes)
connecting the lobules that connect with the larger ducts to form the hepatic duct. As
bile is made in the liver, it travels through the common hepatic duct and on to the
gallbladder and the duodenum. Bile aids digestion by being yellow or orange and
helping to break down food.

25. Functions of liver
 The liver is responsible for controlling the majority of chemical levels in the blood. The
liver secretes this yellow or orange liquid. By breaking down fats, it makes them easier to
digest and absorb. As the blood leaves the stomach and intestines, it is filtered by the liver.
In the liver, blood is broken down, balanced, and nutrient-rich nutrients are created for the
body. As well as breaking down the medicines in the blood to make them easier to use by
the body, it metabolizes them. This liver performs several important functions, including:
• Bile helps transport waste away from the small intestine and break down fat during
digestion.
• It is also responsible for producing proteins for blood plasma
• Produces cholesterol and special proteins for carrying fat around the body
• Glucose is stored and released as Necessary
• The liver uses the iron in hemoglobin to produce hemoglobin.
• Produces urea (one of the materials excreted in the urine as a result of protein Metabolism
that is harmful.

26.  Blood is cleansed of harmful substances and medicines Aids clotting of the blood
 By making immune factors, it removes bacteria from the bloodstream and
protects the body against infections
 Bilirubin is cleared by this medication (high levels of bilirubin cause yellowing of
the skin and eyes).
 The liver excretes harmful substances into the bile or blood after they have been
broken down by the liver. As bowel movements leave the body, bile by-products
enter the intestine By excreting blood by-products as urine; the kidneys eliminate
these substances from the body.

27. Disorders of the Human Digestive System
 Vomiting: It is the ejection of stomach contents through the mouth.
 Diarrhea: It is the abnormal watery bowel movement. Prolonged diarrhea eventually
leads to dehydration.
 Constipation: A condition in which the faces are clutched within the rectum due to an
irregular bowel movement.
 Indigestion: A pain or discomfort in the stomach which is caused when food is not
digested properly, resulting in the feeling of fullness. Indigestion is mainly caused due
to inadequate enzyme secretion, food poisoning, anxiety, overeating and eating spicy
foods.

28. Gastrointestinal Reflux Disease (GERD)
 Gastroesophageal reflux disease (GERD) occurs when stomach acid frequently
flows back into your esophagus. The acid reflux can irritate the lining of your
digestive system.
Common symptoms include:
 Heartburn
 Chest pain
 Difficulty swallowing
 A feeling of a lump in your throat
 Regurgitation of food and liquids that taste sour
 Disrupted sleep
 Laryngitis
 Chronic coughing, especially at night
Treatment often involves lifestyle and diet changes, along with acid reflux
medication.

29. Celiac Disease
 This digestive disease is also categorized as an immune system disorder. Celiac disease is
triggered by the consumption of foods that contain gluten.
 Gluten is a protein that is found in wheat, barley, and rye. Over time it can wreak have on
the small intestine causing digestive problems and nutrient deficiencies from a lack of
proper nutrient absorption.
Symptoms of Celiac Disease include:
 Diarrhea
 Fatigue
 Weight loss
 Bloating and gas
 Abdominal pain
 Nausea and vomiting
 Constipation
There is no cure for Celiac Disease, but most people can promote intestinal healing and
mitigate symptom frequency and severity by sticking to a strict gluten-free diet.

30. Irritable Bowel Syndrome (IBS)
IBS is a common digestive disorder that affects the large intestine. The main cause of the disorder is still
not well understood by medical professionals.
Symptoms include:
 Abdominal pain and cramping
 Bloating and gas
 Diarrhea
 Constipation
 Changes in the appearance of your bowels
 Inconsistent bowel movement frequency
Most can control their symptoms by managing diet, lifestyle and stress. Those living with more severe
symptoms can be treated with prescription medication.

31. Ulcerative Colitis
 Ulcerative colitis is a chronic inflammatory bowel disease. With this disease, abnormal
reactions of the immune system cause chronic inflammation and painful ulcers on the
inner lining of the large intestine.
 Ulcerative colitis is most likely to develop in people between the ages of 15 and 30 but
can be diagnosed at any age.
Symptom severity varies greatly depending on the amount of inflammation in the large
intestine but often include:
 Diarrhea, with blood or pus, Abdominal pain and cramping
 Rectal pain, Rectal bleeding
 Urgency to defecate, Inability to defecate
 Weight loss, Fatigue, Fever
 Failure to grow (in children)
There is no cure for ulcerative colitis but many people experience long periods of
remission with no active symptoms.

32. Crohn's Disease
 Crohn’s Disease is another form of inflammatory bowel disease which causes inflammation of the
digestive tract.
 Inflammation caused by this disease can involve various sections of the digestive tract which often
spread into deeper layers of the bowel.
 Crohn's disease can be extremely painful and debilitating and sometimes lead to life-threatening
complications.
Symptoms include:
 Diarrhea
 Fever, Fatigue
 Abdominal pain and cramping
 Blood in your stool, Mouth sores
 Reduced appetite, Weight loss
 Pain or drainage near or around the anus
 Inflammation of skin, eyes and joints ,liver or bile ducts
 Kidney stones, Anemia
There is no cure for Crohn’s Disease, professional medical treatment can help mitigate symptoms that
lead to long-term remission.

33. References
1. https://www.geeksforgeeks.org/human-digestive-system-digestive-glands/
2. https://nursinglecture.com/salivary-glands/
3. Lindsay R. Piraino , Danielle S. W. Benoit and Lisa A. DeLouise; MDPI Journal;
Salivary Gland Tissue Engineering Approaches: State of the Art and Future
Directions; 2021, 10(7), 1723
4. https://www.kenhub.com/en/library/anatomy/the-salivary-glands
5. Byjus.com/biology/human-digestive-system/

34. THANK YOU