This presentation covers the anatomy and functions of the human digestive system, detailing processes such as ingestion, digestion, absorption, and waste elimination. It explains the roles of various digestive organs, including the mouth, stomach, small intestine, and large intestine, as well as enzymes and hormones involved in digestion. Additionally, it discusses related health issues like malnutrition and digestive disorders.

1. Digestive System
Anatomy
Supervisor - Dr. Archana Kumar
Department – Amity Institute Of
Biotechnology
By - Aditi Tanwar
B Sc. Zoology hons (2021-2024)

2. With this presentation we will learn to develop an understanding
of the relationships between the structures and functions of the
human digestive system and digestive processes which include
the processes of digestion include six activities: ingestion,
propulsion, mechanical or physical digestion, chemical digestion,
absorption, and defecation.
OBJECTIVES:-
• Be able to describe the major function or functions of each organ in the digestive
system.
• Be able to know how the process of chemical digestion.
• Know the illness related to elimination of waste and diseases related to nutrition
deficiency.

3. General Terminologies
• NUTRITION- the process of taking in
and using food.
• NUTRIENTS- substances in food that
are used as energy sources of the
body
• DIGESTIVE SYSTEM- the organs and
glands in the body that are responsible
for digestion
•
• DIGESTION- the breakdown of food to
smaller molecules

4. TWO TYPES OF DIGESTIVE SYSTEM
• INCOMPLETE DIGESTIVE SYSTEM-
common among invertebrates, there is
only a single opening for the ingestion of
food.
• COMPLETE DIGESTIVE SYSTEM-
common among nematodes, annelids,
mollusks, echinoderms and vertebrates,
this type has digestive tubes with 2
openings.

5. Human Digestive System

6. Human Digestive System
The human digestive system consists of the alimentary canal
and the associated glands.
The alimentary canal begins with an anterior opening – the
mouth, and it opens out posteriorly through the anus. The
mouth leads to the buccal cavity or oral cavity. The oral
cavity has a number of teeth and a muscular tongue. Each
tooth is embedded in a socket of jaw bone. This type of
attachment is called thecodont. Majority of mammals
including human being forms two sets of teeth during their
life, a set of temporary milk or deciduous teeth replaced by a
set of permanent or adult teeth. This type of dentition is
called diphyodont. An adult human has 32 permanent teeth
which are of four different types (Heterodont dentition),
namely, incisors (I), canine (C), premolars (PM) and molars
(M).

7. The hard chewing surface of the teeth, made up of enamel,
helps in the mastication of food. The tongue is a freely
movable muscular organ attached to the floor of the oral
cavity by the frenulum. The upper surface of the tongue has
small projections called papillae, some of which bear taste
buds.

8. 1. Food processing begins in the mouth.
2. The food is then swallowed and moved through pharynx into the
esophagus.
3. Then food is mechanically and enzymatically digested in the
stomach.
4. Most enzymatic digestion takes place in the small intestine.
5. The large intestine then eliminates wastes leading to the opening for
the elimination of waste called anus.

9. TWO PHASES OF DIGESTION
MECHANICAL PHASE - involves the breaking up of
food into small pieces, pushing the food down the food
tube, and mixing it with digestive juices.
CHEMICAL PHASE- involves the further breaking up of
the larger molecules of food into smaller molecules by
the action of digestive enzymes.

10. Process Of Digestion
Mechanical Digestion- starts in the mouth (mastication)
where four kinds of teeth tear the food into pieces.
Chemical Digestion- our mouth has salivary glands that
secrete saliva. This saliva contains the enzyme called
salivary amylase which catalyzes maltose into glucose.
The pharynx and esophagus conduct food to the stomach.
After being chewed, the food is swallowed through the
pharynx extending to the oesophagus.

11. Digestion Of Food In Stomach
The oesophagus is a thin, long tube which extends posteriorly passing
through the neck, thorax and diaphragm and leads to a ‘J’ shaped bag like
structure called stomach.
A muscular sphincter (gastro-oesophageal)
regulates the opening of oesophagus into
the stomach. The stomach, located in the
upper left portion of the abdominal cavity,
has four major parts – a cardiac portion
into which the oesophagus opens, a fundic
region, body (main central region) and a
pyloric portion which opens into the first
part of small intestine. Each of the
openings, the cardiac and the pyloric, has
a sphincter muscle that keeps the
neighboring region closed, except when
food is passing through. In this manner,
food is enclosed by the stomach until ready
for digestion.

12. The stomach has the ability to 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.
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.

14. Small intestine is 5-6m long it is distinguishable into three regions, a ‘C’ shaped
duodenum, a long coiled middle portion jejunum and a highly coiled ileum.
Ileum opens into the large intestine. It consists of caecum, colon and rectum.
Caecum is a small blind sac which hosts some symbiotic micro-organisms. A
narrow finger-like tubular projection, the vermiform appendix which is a vestigial
organ, arises from the caecum. The caecum opens into the colon. The colon is
divided into four parts – an ascending, a transverse, descending part and a
sigmoid colon. The descending part opens into the rectum which opens out
through the anus.

15. Absorption in the small
intestines
Once broken down the nutrients are absorbed by the inner walls of the
small intestine into the blood stream. The nutrients are rendered small
enough so that they may pass, or "be transported", across the epithelial
cells of the gastrointestinal tract. The nutrients are absorbed by processes
of simple/passive diffusion, facilitated diffusion, primary active transport,
or secondary active transport.
The small intestine is good for absorption since it has a large inner
surface area. This is formed many tiny finger-like structures of tissue
called villi. The individual epithelial cells also have finger-like projections,
which are called known as microvilli.
For transport, nutrients commonly rely upon:
Lipids – undergo passive or simple diffusion
Short-chain fatty acids – diffusion
Amino acids – primary active transport
Glucose – secondary active transport
Fructose – facilitated diffusion

16. The job of large intestine is to absorb water,
minerals, and some of the remaining nutrients
from your food. It will change the leftover
waste into a bowel movement. This is also
called stool. Rectum stores the stool until we
feel the need to have a bowel movement.
Muscles of rectum then push the stool through
anus and out of body.

17. Liver
 Liver is the largest internal organ of the body.
 It secrets bile which emulsifies fat and stored in gall
bladder then ejected into the small intestine.
 It converts excess glucose to glycogen and stores it.
 Converts excess amino acids into fatty acids and urea.

18. Pancreas
 The pancreas is a compound (both exocrine and endocrine)
elongated organ situated between the limbs of the ‘C’ shaped
duodenum.
 The exocrine portion secretes an alkaline pancreatic juice
containing enzymes
 The endocrine portion secretes hormones, insulin and glucagon
 The enzymes secreted by the pancreas are called trypsin and
chymotrypsin.

19. 1. Bile from the liver and digestive enzymes from the pancreas released into
the duodenum.
2. These two then act on the chyme.
3. Then enzymes produced by the epithelial cells lining duodenum catalyze
the final steps in the digestion of the major types of nutrients.
Chyme moves through the digestive tract by peristalsis and motions of villi.
Enzymes digest chyme as follows:-
• Carbohydrates are digested to monosaccharide or simple sugars.
• Proteins are digested to amino acids
• Fats are digested to fatty acids and monoacylglycerols

20. Some hormones that regulate digestion

21. Absorption
• It is the process by which substances are taken in by the
cells.
• Absorption takes place mainly through the villi of the small
intestine.
• Digested food in the form of amino acids, simple sugar,
fatty acids and glycerol diffuse into the cells of the villi.

22. Process Of Absorption
• Most of the digested food diffuse into capillaries and
reach the blood, while fatty acids and glycerol diffuse into
the lacteals and reach another circulating fluid called
lymph.
• Through diffusion, digested food reaches the blood and
lymph and undergoes a process called circulation.
• The circulating fluids distribute the digested food to all the
cells of the body.
• Undigested food passes through the large intestine where
absorption of some water, minerals and certain drugs
takes place.

23. 1. Vomiting: It is the ejection of stomach contents through the mouth. This
reflex action is controlled by the vomit center in the medulla. A feeling of
nausea precedes vomiting.
2. Jaundice: The liver is affected, skin and eyes turn yellow due to the deposit
of bile pigments.
3. Diarrhea: The abnormal frequency of bowel movement and increased
liquidity of the fecal discharge is known as diarrhea. It reduces the absorption
of food.
4. Constipation: In constipation, the faeces are retained within the colon as
the bowel movements occur irregularly.
5. Indigestion: In this condition, the food is not properly digested leading to a
feeling of fullness. The causes of indigestion are inadequate enzyme
secretion, anxiety, food poisoning, over eating, and spicy food.

24. Protein-energy malnutrition (PEM)
• Marasmus is produced by a simultaneous deficiency of
proteins and calories. It is found in infants less than a year in
age, if mother’s milk is replaced too early by other foods
which are poor in both proteins and caloric value. This often
happens if the mother has second pregnancy or childbirth
when the older infant is still too young. In Marasmus, protein
deficiency impairs growth and replacement of tissue
proteins; extreme emaciation of the body and thinning of
limbs results, the skin becomes dry, thin and wrinkled.
Growth rate and body weight decline considerably. Even
growth and development of brain and mental faculties are
impaired.

25. Protein-energy malnutrition (PEM)
• Kwashiorkor is produced by protein deficiency
unaccompanied by calorie deficiency. It results from the
replacement of mother’s milk by a high calorie low protein
diet in a child more than one year in age. Like marasmus,
kwashiorkor shows wasting of muscles, thinning of limbs,
failure of growth and brain development. But unlike
marasmus, some fat is still left under the skin; moreover,
extensive oedema and swelling of body parts are seen.

26. Bibliography
• Hall, John E. (2011). "General Principles of Gastrointestinal Function". Guyton and Hal
Textbook of Medical Physiology (12th ed.). Saunders Elsevier. p. 755. ISBN 978-
1416045748.
• Saladin, Kenneth (2011). Human Anatomy. McGraw Hill. p. 659. ISBN 9780071222075.
• Saladin, Kenneth (2011). Human Anatomy. McGraw Hill. pp. 621–
622. ISBN 9780071222075.
• Britannica Concise Encyclopaedia. Encyclopaedia Britannica, Inc. 2007. ISBN 978-
1593392932.
• Wood, Jackie D. (2009), "Gastrointestinal Physiology", in Rhoades, Rodney A.; Bell,
David R. (eds.), Medical Physiology: Principles for Clinical Medicine (3rd ed.),
Philadelphia, PA: Lippincott Williams & Wilkins, pp. 463–496
• Maton, Anthea (1993-01-01). Human Biology and Health. Prentice Hall 1993. ISBN 978-
0-13-981176-0