Digestive System: Also known as gastrointestinal tract, digestive tract, digestional tract, GI tract, GIT, gut, or alimentary canal. Consist of alimentary tract and Accessory organs It involve in Ingestion, Digestion, Absorption and Excretion It is started from mouth and ended at anal canal, that is assisted and supported by many parts. Parts of Digestive System: Primary digestive organs & Accessory organs Primary digestive organs: Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anal canal Accessory organs: Teeth, Tongue, Salivary glands, Liver, Gallbladder, Pancreas. Mouth First part of GIT, Also known as oral or buccal cavity, It consist of muscles & bones Tongue or Lingua:Voluntary muscular structure, Occupies floor of mouth Superior surface consist of numerous papillae contains taste bud for the sense of taste. Attached inferiorly with hyoid bone, Highly mobile muscular part of GIT. Teeth: Teeth are the hard and whitish substances present in the mouth Which is essential for chewing & speech. They fixed in socket of alveolar ridge in mandible & maxilla (Jaw). Diphyodont is a type of dentition in which two successive sets of teeth are developed during the lifetime. The first set of teeth is temporary or deciduous or milk and the other set is permanent teeth Salivary glands: These are exocrine glands found in oral cavity that secrete complex fluid known as saliva Types: Major & Minor salivary glands Major salivary gland: Parotid, Submandibular & Sublingual Minor salivary glands: There are 450 minor salivary glands present in oral cavity, lips, cheeks, palate and floor of the mouth Pharynx: Wide, muscular tube situated behind the nose, mouth & larynx Cavity of pharynx divided into nasopharynx, oropharynx and laryngopharynx. Esophagus: The esophagus is a fibromuscular tube, approximately 25cm in length, It transports food from the pharynx to the stomach. Stomach: The stomach is a hollow organ in the GIT. It is the “J” shaped dilated part, situated in the upper part of the abdomen. Gross Anatomy of stomach: The stomach has four main anatomical divisions; the cardia, fundus, body and pylorus: Cardia: surrounds the superior opening of the stomach. it consist cardiac sphincter Fundus: the rounded, often gas filled portion superior to and left of the cardia. Body: the large central portion inferior to the fundus. Pylorus: This area connects the stomach to the duodenum. It is divided into the pyloric antrum, pyloric canal and pyloric sphincter. Pancreas: The pancreas is a soft, finely lobulated, elongated dual (Exo Endocrine) gland. Liver: It is the largest gland of the body. It involve metabolic activities The liver is one of the vital organs of the body, responsible for chemical actions that the body needs to survive. Small intestine: The intestine which is the longest part of the digestive tube is divided into small intestine and large intestine. Large Intestine or Colon: It is a last part of the GIT

1. The Digestive
system
By Thiru murugan. M
1st Semester Anatomy

2. Unit : III The Digestive system (Syllabus)
• Structure of alimentary canal and accessory organs of digestion
• Application and implications in nursing
• Digestive System:
• Also known as gastrointestinal tract, digestive tract, digestional tract, GI tract, GIT, gut, or
alimentary canal.
• Consist of alimentary tract and Accessory organs
• It involve in Ingestion, Digestion, Absorption and Excretion
• It is started from mouth and ended at anal canal, that is assisted and supported by many
parts.
• Parts of Digestive System: Primary digestive organs & Accessory organs
• Primary digestive organs: Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large
Intestine, Rectum, Anal canal
• Accessory organs: Teeth, Tongue, Salivary glands, Liver, Gallbladder, Pancreas.

3. Diagram

4. • Functions of Digestive System:
• Ingestion: taking of food into the alimentary tract. i.e. eating &
drinking.
• Propulsion: mixes & moves the contents along the alimentary tract.
• Digestion: Mechanical breakdown of food e.g. mastication (chewing)
& Chemical digestion of food into small molecules by enzymes.
• Absorption: this is the process by which digested food substances
pass into the blood for circulation.
• Elimination: food substances that have been eaten but cannot be
digested & absorbed are excreted from the alimentary canal as feces
by the process of defecation.

5. • Mouth
• First part of GIT, Also known as oral or buccal cavity, It consist of muscles & bones
• Relations:
• Anteriorly - lips, Posteriorly – pharynx, Laterally-muscles of cheeks, Superiorly - hard
palate, Inferiorly - tongue & floor of the mouth
• Lips or Labia: Fleshy folds surrounding the opening of mouth, The inner surface of
each lip is attached to Gum by a midline fold of mucous membrane called labial
frenulum
• Cheeks or Buccae: Fleshy flaps, forming large part of each side of face
• Cheek composed – skin, buccinator, parotid gland, blood vessels, nerves, mucous
gland & mucosa
• Palate: form the roof of the oral cavity and floor of nasal cavity.
• It has two parts: an anterior hard palate & a posterior soft palate

6. • Uvula is a curved muscle fold hanging down in middle part of soft palate. it
consist of 4 folds of mucous membranes, the anterior folds called “palatoglossal
arch” & the posterior folds called “palatopharyngeal arch”. On each side between
arch is a collection of lymphoid tissue called “palatine tonsils”
• Gums or Gingivae: Gums are soft tissue which covers the alveolar process of
upper & lower jaw and surrounded the neck of teeth
• Function of mouth:
• Mastication (chewing) of food
• Mixing masticated food with saliva
• Initiation of swallowing by the tongue
• Allowing for the sense of taste
Diagram:

7. • Tongue or Lingua:Voluntary muscular structure, Occupies floor of mouth
• Superior surface consist of numerous papillae contains taste bud for the sense of
taste. Attached inferiorly with hyoid bone, Highly mobile muscular part of GIT.
• Parts of the Tongue: Root, Body, Apex or tip, Dorsal surface & Ventral surface
• Root: Attaches the tongue to roof of the mouth.
• Body: anterior two-thirds of the tongue.
• Apex: Also known as the tip, Rests against the incisor teeth.
• Dorsal surface:
• The top of the tongue has a V-shaped line known as the “terminal sulcus” that
divides the tongue into the anterior & posterior surfaces
• At the apex of “V” a small “foramen Caecum”
• A small medial line extends from tip of the tongue to foramen Caecum which
divides tongue to right & left halves is called “median sulcus”.

8. Dorsal surface of the tongue:
• Arterial supply: Lingual artery
• Venous drainage: Dorsal lingual veins, deep
lingual vein
• Nerve supply: Vagus nerve, hypoglossal
nerve, lingual nerve, Facial nerve,
glossopharyngeal nerve.

9. • Ventral surface: Covered with smooth mucous membrane
• The median mucus fold is called “frenulum linguae”
• Frenulum stretching from floor of the mouth
• On each side of the frenulum, the deep lingual veins can be seen.
Ventral surface:
• Function of Tongue
• Mastication
• Deglutition
• Speech
• Taste
• Oral cleaning

10. • Teeth: Teeth are the hard and whitish substances present in the mouth Which
is essential for chewing & speech. They fixed in socket of alveolar ridge in
mandible & maxilla (Jaw). Diphyodont is a type of dentition in which two
successive sets of teeth are developed during the lifetime. The first set of
teeth is temporary or deciduous or milk and the other set is permanent
teeth
• At birth the teeth of both dentitions(temporary or primary & permanent or
secondary) are present in immature form in mandible & maxilla. There are
20 temporary or deciduous teeth(10 in each Jaw 4 incisors, 2 canines & 4
molars). Temporary deciduous or primary teeth begin to erupt at 6 months
and all temporary teeth should present 24 months.
• The permanent or secondary teeth begin to replace the temporary teeth in 6
year that consist 32 teeth(16 in each jaw - 4 incisors, 2 canines, 4
premolars & 6 molars ) complete by 21st year of life

11. • Arrangement of teeth: Teeth are
arranged in 2 dental arches or jaws
• Maxillary or upper arch (upper jaw)
• Mandibular or lower arch (lower
jaw)

12. Types or forms of teeth: The 4 main types of teeth are:
• Incisors - incisors are 8 in the front center of mouth (4 on both
bottom and top). Incisors - used to bite into your food.
• Canines - canines are the next teeth that develop in mouth.
There are 4 canines in total, and they are sharpest teeth, used for
tearing apart food.
• Premolars - Premolars are used for chopping the food. It have a
flat biting surface. There are 8 premolars in total.
• Molars - molars are largest teeth. Used to grind and crush food.
Molars have a large flat biting surface. Total 12

13. • Structure of tooth: There are 3 basic parts of tooth:
• Crown: part protrude from gums or gingiva
• Root: bottom part of the tooth; may be single, double, or triple root embedded in bone
• Neck: in between crown & root
•Tissues of tooth:
• Enamel: the hard tissue that covers the crown portion of the tooth, supported by
dentine
• Dentin: the material forming the main inner portion of the tooth structure.
• Cementum: the bone like substance covering the root of the tooth. It secure the tooth
in its socket.
• Pulp: the vital tissues of the tooth consisting of nerves, blood vessels, and connective
tissue.
• The Periodontium is the specialized tissues that both surround and support the teeth.

14. • Arterial supply:
• Maxillary teeth: maxillary artery
• Mandibular teeth: maxillary
artery
• Venous return: internal jugular
vein
• Nerve supply: Upper jaw -
maxillary nerve & Lower jaw -
mandibular nerve
Blood & nerve supply of
teeth

15. • Functions of teeth:
• Helps in mastication
• Incisors - cutting of food
• Canine - tearing of food
• Premolar - chopping of food
• Molar – grinding of food
• Help in speech
• Give definite shape and beauty of face
• Maintain personality
• May be used for self protection

16. • Salivary glands: These are exocrine glands found in oral cavity that secrete
complex fluid known as saliva
• Types: Major & Minor salivary glands
• Major salivary gland: Parotid, Submandibular & Sublingual
• Parotid gland: It is a Largest salivary gland, secreting 60 to 65% of total
saliva.
• Pyramidal in shape, paired glands, Located in each side of the face, just below
the external ear. Each gland has a duct called parotid duct or Stenson’s duct.
This duct open into mouth and supply saliva
• Submandibular gland: Located just below the mandibular bone. It has
submandibular duct or Wharton's duct open into the mouth at lingual frenulum
• Sublingual gland: Smallest salivary gland, Located Infront of submandibular
gland below the tongue. Open into oral cavity through small ducts called Rivinus
duct

17. • Minor salivary glands: There are 450 minor salivary
glands present in oral cavity, lips, cheeks, palate and
floor of the mouth
• Continuous slow secreting glands, thus have a important
role in protecting and moistening oral mucosa,
especially when major salivary glands are mostly
inactive.
• Function of salivary gland: Secreting & supplying of
saliva
Major salivary gland:

18. • Structure of salivary glands:
• Salivary glands surrounded by fibrous
capsule.
• They consist number of lobules that made up
of small acini or secretory end pieces lined
with secretory cells.
• Secretions supply into ductules that pour into
mouth through main duct.
• Blood supply: external carotid artery &
external jugular veins
• Nerve supply : facial nerve(VII) & glosso
pharyngeal nerve (IX)

19. • Pharynx: Wide, muscular tube situated behind the nose, mouth & larynx
• Cavity of pharynx divided into nasopharynx, oropharynx and
laryngopharynx.
• Nasopharynx involving in respiration, oropharynx & laryngopharynx
involving digestive system
• Food passes from mouth to esophagus through pharynx
• Layers: in consists 3 layers, the innermost mucous layer, middle submucous
& outer muscular layer
• Blood supply:
• Arterial supply – external carotid & facial arteries
• Venous return – internal jugular & facial veins
• Nerve supply – vagus, glosso pharyngeal & cervical ganglions

20. • Functions of Pharynx:
• Passage of food from mouth to
esophagus
• Bolus move from oropharynx to
laryngo pharynx
• Naso pharynx closed by soft
palate, it prevent food enter into
nose
• Larynx is closed by epiglottis.

21. • Esophagus: The esophagus is a fibromuscular tube, approximately
25cm in length,
• It transports food from the pharynx to the stomach.
• It originates at the inferior border of the cricoid cartilage (C6) and
extends to the cardiac orifice of the stomach (T11).
• The esophagus begins in the neck, at the level of C6. Here, it is
continuous superiorly with the laryngopharynx.
• It descends downward into the superior mediastinum of the thorax,
positioned between the trachea and the vertebral bodies.
• It then enters the abdomen via the esophageal hiatus (an opening in the
right crus of the diaphragm).
• It terminates by joining the cardiac orifice of the stomach.

22. • Parts of the esophagus: 3 parts:
• Cervical part: 4 cm in length, The cervical part
extends from the lower border of cricoid
cartilage to the superior border of manubrium.
• Thoracic part: 20 cm in length, The thoracic
part extends from superior border of manubrium
sterni to the esophageal opening in the
diaphragm.
• Abdominal part:1-2 cm in length, The
abdominal part extends create esophageal
opening in the diaphragm to the cardiac end of
the stomach. The narrowest part of esophagus is
its commencement at the cricopharyngeal
sphincter

23. • Anatomical Structure: The esophagus consist of 4 layers
1. Adventitia: outer layer of connective tissue.
2. Muscle layer: middle layer, consists of longitudinal & circular muscle.
3. Submucosa: inner layer
4. Mucosa: inner most layer
• Esophageal Sphincters: There are 2 sphincters present in the esophagus, known
as the upper and lower esophageal sphincters.
• Upper Esophageal Sphincter: The upper sphincter is an anatomical, striated
muscle sphincter at the junction between the pharynx and esophagus. it is
constricted to prevent the entrance of air into the esophagus.
• Lower Esophageal Sphincter: The lower esophageal sphincter is located at
the gastro-esophageal junction (between the stomach and esophagus). it prevent
the reflux of gastric contents.

24. • Blood supply: Arterial supply: thoracic aorta, inferior thyroid artery & left
gastric artery
• Venous return: azygous veins, inferior thyroid vein & left gastric vein
• Nerve supply : esophageal plexus, which is formed by a combination of the
parasympathetic vagal trunks and sympathetic fibers from
the cervical & thoracic sympathetic trunks
• Functions of esophagus:
• it act as a transport tube that directs the progression of food and fluids from the
mouth to the stomach.
• Food is transported through the esophagus by Peristalsis.
• Hardening of these muscular layers can interfere with peristalsis and cause
difficulty in swallowing (dysphagia),

25. • Stomach: The stomach is a hollow organ in
the GIT.
• It is the “J” shaped dilated part, situated in the
upper part of the abdomen.
• Gross Anatomy of stomach: The stomach has
four main anatomical divisions; the cardia,
fundus, body and pylorus:
• Cardia: surrounds the superior opening of the
stomach. it consist cardiac sphincter
• Fundus: the rounded, often gas filled portion
superior to and left of the cardia.
• Body: the large central portion inferior to the
fundus.
• Pylorus: This area connects the stomach to the
duodenum. It is divided into the pyloric antrum,
pyloric canal and pyloric sphincter.
Anatomical parts of stomach

26. • Anatomical description of the stomach:
• The stomach has:
Two openings:
1. The cardiac orifice: in between esophagus & the
stomach.
2. The pyloric orifice: in between pylorus & duodenum
Two sphincters:
1.Cardiac sphincter: The lower esophageal sphincter,
or cardiac sphincter, at the upper portion (cardia) of
the stomach. This sphincter prevents the acidic contents
of the stomach from moving upward into the esophagus.
2.Pyloric sphincters: very powerful sphincter, which
regulates the passage of chyme into the duodenum
which is present in between pylorus part of stomach
and duodenum.

27. • Curvatures & omentum of the stomach:
• Lesser curvature: Forms the right border of the
stomach and extends from the cardiac orifice to the
pylorus. It is suspended from the liver by the lesser
omentum.
• Greater curvature: Much longer than the lesser
curvature and extends from the left of the cardiac
orifice, over the dome of the fundus, and along the
left border of the stomach to the pylorus.
• The lesser omentum: (small omentum or gastro
hepatic omentum) is the double layer of peritoneum
that extends from the liver to the lesser curvature of
the stomach & to the first part of the duodenum
• The greater omentum extends from the lower part
of the greater curvature to the transverse colon

28. • The wall of the stomach has four
layers:
• The mucosa is the inner layer
(stomach lining). It contains glands
that produce enzymes & acid,
which help digest food.
• The submucosa attaches the
mucosa to the muscularis.
• The muscularis is a layer of
muscle.
• The serosa is a strong outer
membrane which covers the
stomach.

29. • Arteries of the stomach:
• All are branches of the celiac
artery, Left gastric artery, Right
gastric artery, Left gastroepiploic
artery & Right gastroepiploic
artery.
• Venous return:
• The left & right gastric veins &
the left gastroepiploic veins.
• Nerve Supply of the stomach:
• Sympathetic - celiac plexus and
Parasympathetic – Vagus
• Function of the stomach:
• Temporary storage for food, held for
2 hours or longer
• Mixing and breakdown of food
• Digestion of food: It continues the
mechanical and chemical
digestion of the bolus.
• Production chyme for easy absorption.
• Stomach Produce gastric acid.
• It Slows food entering intestines.
• Help with vitamin a bsorption
(Vitamin B12).

30. •Pancreas: The pancreas is a soft, finely lobulated, elongated dual (Exo Endocrine)
gland.
•The pancreas is an organ of the digestive system and endocrine system.
•In humans, it is situated in the abdomen behind the stomach
•The exocrine part secretes the pancreatic juice and the endocrine part secretes the
hormones (insulin).
•The pancreatic juice helps in the digestion of lipids, carbohydrates, and proteins,
whereas the pancreatic hormones maintain blood glucose.
•The pancreas is “J”- shaped organ
•Pancreas is divided into four parts:
1. Head
2. Neck.
3. Body
4. Tail.

31. • Blood supply & Nerve supply
• Arterial supply:
• Splenic artery, Superior
pancreaticoduodenal artery and Inferior
pancreaticoduodenal artery.
• Venous drainage: Portal vein, superior
mesenteric vein & splenic vein.
• Nerve supply:
• The sympathetic and parasympathetic
nerve fibers reach the gland along its
arteries from coeliac and superior
mesenteric plexuses.

32. • Ducts of the pancreas:
• There are 2 ducts: main and accessory, which drain the exocrine
secretion into the duodenum.
• Main pancreatic duct:
• It begins in the tail and traverses the whole length of the gland
• At the neck, it turns downward & right to enter into the 2nd part of
duodenum.
• It joins the bile duct as it pierces the duodenal wall to form the
hepatopancreatic ampulla (of Vater) which opens by a narrow mouth
below to the pylorus.
• Accessory pancreatic duct:
• It begins in the lower part of the head, and then runs upward, crossing
in front of main pancreatic duct & opens into the 2nd part of the
duodenum

33. Ducts of the pancreas

34. • Exocrine Function of the Pancreas: It contains exocrine
glands that produce enzymes important to digestion.
• These enzymes include trypsin and chymotrypsin to digest proteins
• Amylase for the digestion of carbohydrates & lipase to break down
fats.
• When food enters the stomach, pancreatic juices are released into
the main pancreatic duct.
• The pancreatic duct joins the common bile duct to form
the ampulla of Vater
• The pancreatic juices and bile that are released into the duodenum,
help the body to digest fats, carbohydrates, and proteins.

35. • Liver: It is the largest gland of the body. It involve metabolic activities
• The liver is one of the vital organs of the body, responsible for chemical
actions that the body needs to survive.
• Liver cells: There are 4 basic cells in the liver:
1. Hepatocytes: 80% of the cells, Store glucose in the form of glycogen,
also vitamin B12, folic acid and iron, Metabolize/detoxify fat & regulates
cholesterol level and Secrete bile (up to 1 litre per day)
2. Hepatic stellate fat storing cells (ITO cells): store approximately
80% of the body's supply of vitamin A & lipids
3. Kupffer cells: Clear the blood of ingested bacterial pathogens, remove
aged RBC
4. Sinusoidal Endothelial Cells: Form the wall of the blood vessels
(sinusoids) that carry blood throughout the liver

37. • Shape: The liver is wedge shaped and resembles a four-sided pyramid
• Colour: It is red-brown in colour.
• Weight: In males: 1.4 to 1.8kg, In females: 1.2 to 1.4kg & At birth: 150 g.
• Proportional weight: In adult 1/40th of the body weight.
• Lobes of the liver:
• The liver is consist of 4 lobes
• Right lobe & Left lobe: The right lobe which forms the base of the
wedge-shaped liver is approximately six times larger than the left lobe.
• Quadrate lobe: between the fossa for gallbladder & the fissure for
ligamentum teres below the porta hepatis.
• Caudate lobe: between the groove for IVC and the fissure for
ligamentum venosum.

38. Posterior
Anterior

39. • Porta hepatis (hilum of the
liver):
• Site: It is found on the
posteroinferior surface and lies
between the caudate & quadrate
lobes.
• Structures forming the
hilum of the liver:
• The right & left hepatic ducts, The
right & left branches of the
hepatic artery, The portal vein,
Sympathetic & parasympathetic
nerve fibers.

40. • Blood supply:
• The liver is a highly vascular organ. It receives blood from 2 sources.
The arterial blood by the hepatic artery & venous blood (rich in
nutrients) is supplied by the portal vein.
• About 80% of this is delivered through the portal vein and 20% is
delivered through the hepatic artery.
• Venous: 3 large hepatic veins, left hepatic vein, middle hepatic
vein & right hepatic vein
• Nerve supply :
• The sympathetic fibers - coeliac plexus.
• The parasympathetic fibers - hepatic branch of the anterior vagal
trunk.

41. • Functions of liver
• Secretary function: Liver Secrete bile for digestion and absorption of
fats.
• Metabolic function: liver involving in metabolism of Carbohydrate, Fat
& Protein
• Detoxicating: Detoxify drugs
• Protective function: Kupffer cells - removes bacteria
• Storage function: Glucose ( in the form of Glycogen), Vit B12, Vit A &
Blood iron.
• Excretory function: Exogenous dyes are excreted
• Synthesis function: Plasma proteins - albumin, α & β globulin,
Coagulation factors I,V, VII, IX & X, Enzymes - alkaline phosphatase.
SGPT, SGOT, Removes ammonia to synthesize urea, Cholesterol.

42. Miscellaneous function:
 Reservoir of blood – about 650 ml
 Erythropoiesis
 Hormone metabolism
 Inactivation of insulin, glucagon, vasopressin
 Reduction & conjugation of oestrogen,
testosterone, cortisol, aldosterone.
 Destruction of RBC
 Thermal regulation.

43. • Biliary system: Biliary system consist
of The right and left hepatic ducts, The
common hepatic duct, the gallbladder
and the cystic duct & Common bile duct
• Right & left hepatic ducts: arises
from the right & left lobes of the liver in
the porta hepatis. The hepatic ducts
unite to form the common hepatic duct.
• The common hepatic duct: The Rt &
Lt hepatic ducts unite to form the
common hepatic duct
• Bile Duct: The common hepatic duct
joined on the right side by the cystic
duct from the gallbladder to form the
bile duct ( common bile duct)bile duct
comes into contact with the main
pancreatic duct.

44. • Hepatopancreatic ampulla:
The common bile duct is usually
joined by the main pancreatic
duct, and together they open into
a small ampulla (opening) in the
duodenal wall, called the
hepatopancreatic ampulla
(ampulla of Vater).
• the bile and pancreatic ducts
open separately into the
duodenum.

45. • Gall bladder: The gallbladder is a
pear-shaped sac lying on the
undersurface of the liver. It has a
capacity of 30 to 50 mL and stores
bile, which it concentrates by absorbing
water.
• Parts of gallbladder: divided into the
fundus, body & neck.
 The fundus is rounded and projects
below the inferior margin of the liver
 The body lies in contact with the
visceral surface of the liver
 The neck becomes continuous with the
cystic duct, join the common hepatic
duct, to form the bile duct.

46. • Blood supply: The cystic artery, a branch of the right hepatic artery,
supplies the gallbladder. The cystic vein drains directly into the portal
vein.
• Nerve Supply: Sympathetic and parasympathetic vagal fibers form the
celiac plexus. The gallbladder contracts in response to the hormone
cholecystokinin, which is produced by the mucous membrane of the
duodenum on the arrival of fatty food from the stomach
• Function of gall bladder:
• 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 response to signals, the gallbladder squeezes stored bile into the small
intestine through a series of tubes called ducts.

47. • Small intestine: The intestine which is the longest part of the digestive
tube is divided into small intestine and large intestine.
• Small intestine located at abdominal cavity, extending from the pyloric
sphincter to the ileocecal valve.
• It is about 6 meter long & like middle finger
• Parts of Small intestine: The small intestine is divided into
Duodenum, Jejunum & Ileum.
• Duodenum: The beginning portion of the small intestine, the duodenum
starts at the pylorus part of the stomach and it joins the jejunum. It consist
of 4 parts.
• Duodenum is the shortest, is where preparation for absorption through
small finger-like protrusions called villi begins.
• The duodenum has an important anatomical feature which is the ampulla of
Vater. This is the site at which the bile duct and pancreatic duct supply their
contents into the small intestine which helps with digestion

48. • The duodenum surrounds the head of
the pancreas.
• It receives gastric chyme from the
stomach, together with digestive juices
from the pancreas (digestive enzymes)
and the gall bladder (bile).
• The digestive enzymes break down
proteins and bile - emulsify fats into
micelles(lipid molecules).
• The duodenum contains Brunner’s
glands, which produce a mucus-rich
alkaline secretion containing
bicarbonate. These secretions, in
combination with bicarbonate from
the pancreas, neutralizes the stomach
acids contained in gastric chyme.

49. • The jejunum: upper part of the small intestine, consist of Microvilli for
absorption of nutrients
• The jejunum is specialized for the absorption through its lining
by enterocytes, small nutrient particles which have been previously
digested by enzymes in the duodenum.
• Products of digestion (sugars, amino acids, and fatty acids) are absorbed
into the blood in jejunum through mirovilli.
• The Ileum: it is the final section of the small intestine, contains villi
similar to the jejunum.
• It absorbs mainly vitamin B12 and bile acids, as well as any other
remaining nutrients and whatever products of digestion were not absorbed
by the jejunum.
• The ileum joins to the cecum of the large intestine at the ileocecal junction.

50. • Blood supply & Nerve supply:
• Duodenum:
• Arterial supply: Superior pancreaticoduodenal artery & Inferior
pancreaticoduodenal artery
• Venous supply: splenic, superior mesenteric and portal veins
• Nerve supply: celiac plexus (sympathetic), vagus nerve (CN X)
(parasympathetic)
• Jejunum and ileum:
• Arterial supply: superior mesenteric artery
• Venous supply: superior mesenteric vein -> portal vein
• Nerve supply: celiac & superior mesenteric plexus(sympathetic), vagus
nerve (CN X) (parasympathetic)

51.  Peritoneum: A double layer of
peritoneum called the
mesentery
 Attaches the jejunum and ileum to
the posterior abdominal wall
 It is fan shaped.
 The large blood vessels and nerves lie
on the posterior abdominal wall and
the branches to the small intestine
pass between the two layers of the
mesentery.

52.  The intestinal villi or villi: In walls of intestines there is a columnar
epithelial cells, or enterocytes, with tiny microvilli on their free border.
 The villi: tiny finger-like projections of the mucosal layer into the
intestinal lumen, about 0.5 to 1 mm long.
 They give the surface of the intestinal mucosa a velvety appearance.
 They are large and numerous in the duodenum & jejunum, but are
smaller and fewer in the ileum.
• Goblet cells : secrete mucus
• A network of blood and lymph capillaries located in villi.
• The lymph capillaries are called lacteals because absorbed fat gives the
lymph a milky appearance.
• Absorption and some final stages of digestion of nutrients take place in
the enterocytes before entering the blood and lymph capillaries.

54.  Intestinal glands:
• These are simple tubular glands distributed over the entire mucous
membrane of the jejunum and ileum.
• They open by small circular apertures on the surface of mucous
membrane between the villi.
• They secrete digestive enzymes and mucus.
 Functions of the small intestine:
• Onward movement of food contents by peristalsis
• Secretion of intestinal juice
• Completion of chemical digestion of carbohydrates, protein, and fats in
the enterocytes of the villi.
• Absorption of nutrients.
• Secretion of the hormones cholecystokinin(CCK) and secretin.

55. • Protection against infection by microbes that have survived the
antimicrobial action of the hydrochloric acid in the stomach, by the
solitary lymph follicles and aggregated lymph follicles (Peyer’s
patches)
• The small intestine is responsible for absorption of nutrients, salt, and
water.
• For example, the duodenum plays an important role in coordinating
how the stomach empties as well as the rate of emptying of bile duct
juices into the intestine.
• The duodenum is also a major site for absorption of iron.
• The jejunum is a major site for absorption of the vitamin, folic acid and
the end of the ileum is the most important site for absorption for the
vitamin B12, and bile salts

56. • Large Intestine or Colon: It is a last part of the digestive
system .
• Larger in diameter, but shorter than the small intestine
• Length: 1.5 meter & Diameter: 6.5 cm
• Location: beginning at the caecum & terminating at the rectum
& anal canal deep in the pelvis.
• The parts of the large intestine form a frame for the small
intestine.
• Parts: there are 4 parts of Large intestine
1. Caecum & Appendix
2. Colon
3. Rectum
4. Anal canal

57. • 1. Caecum:This is the first part of
large intestine.
• It is dilated region which has a blind
end inferiorly and is continuous with
the ascending colon superiorly.
• Located just below the junction of the
ileocecal valve open from the ileum.
• Attached to its posteromedial surface is
the appendix.
• Ileocecal valve that separates
the small intestine and the large
intestine. Its function is to limit
backflow of colonic contents into
the ileum.

58. • Functions the caecum:
• The caecum start the process of fluid
and electrolyte reabsorption, which
occurs to a large extent in the ascending
and transverse colon.
• The distensible nature and 'sac-like'
morphology of the caecum are
adaptations for the storage of larger
volumes of semiliquid chyme entering
from the small bowel via the ileocecal
valve.
• Blood supply: ileocolic artery,
ileocolic vein,
• Nerve: sympathetic and
parasympathetic nerves via the superior
mesenteric plexus

59. • Appendix (Vermiform Appendix): It is a fine tube, closed at one end,
which lead from the caecum. The appendix is a slender & worm-shaped
pouch.
• Same structure as a wall of large intestine but contains lymphoid tissue.
• No digestive function, problems when it becomes inflamed.
• The human appendix averages 9 cm in length but can range from 5 to
35 cm.
• The diameter of the appendix is 6 mm & more than 6 mm is considered a
thickened or inflamed appendix.
• The appendix is usually located in the lower right quadrant of the abdomen,
near the right hip bone.

60. • Structure of Appendix: Its position
within the abdomen corresponds to a
point on the surface known as
McBurney's point.
• The appendix is connected to
the mesentery in the lower region of
the ileum, by a short region of
the mesocolon known as
the mesoappendix.
• Blood Supply: appendix artery,
appendix vein & portal vein.
• Nerve supply: celiac plexus and
lesser splanchnic nerve T10, T11

61. •2.colon: Divided into 4 Parts:
1. The ascending colon
2. The transverse colon
3. The descending colon
4. The sigmoid colon
• Ascending colon: This first part of the
large intestine is connected to the small
intestine by cecum.
• The ascending colon runs through the
abdominal cavity, upwards toward the
transverse colon.
• The cecum receives the solid wastes of
digestion from the ileum via the ileocecal
valve, then reaches the ascending colon.

62. • This passes upwards from the caecum to the level of liver where it curves
acutely to the left at the hepatic flexure to become the transverse colon.
• Transverse colon:
• It is starting from the hepatic flexure to the splenic flexure.
• It curves accurately downward to become descending colon.
• Descending colon:
• From the splenic flexure to the beginning of the sigmoid colon.
• The function of the descending colon is to store feces that will be emptied
into the rectum.
• Sigmoid colon:
• after the descending colon and before the rectum.
• The name sigmoid means S-shaped.
• Stool move from sigmoid colon into the rectum.

63. • Taeniae coli: Taeniae coli, three
thickened bands of longitudinal muscle.
(taeniae meaning ribbon in Latin)
• The teniae coli contract lengthwise to
produce the haustra, the bulges in the
colon
• The haustra (singular haustrum) of
the colon are the small pouches caused by
sacculation (sac formation), which give
the colon its segmented appearance.
• One haustrum distends as it fills
with chyme, which stimulates muscles to
contract, pushing the contents to the next
haustrum.

64. • Rectum:
• It is the final straight portion of the large intestine
• Structure:
• This is a slightly dilated section of the large intestine 13 cm long.
• The rectum is a continuation of the sigmoid colon & connects to the anus.
• Anus: The human anus is the external opening of the rectum.
• Anal canal is short passage about 3.8 cm long from rectum to the exterior.
• Two sphincters control the anus :
• 1. Internal sphincter: consisting smooth muscle, under the control of
ANS & involuntary.
• 2. External sphincter: formed by skeletal muscle, under to voluntary
control.
• It is located behind the perineum which is located behind the vagina in
females and behind the scrotum in males.

65. Rectum & Anus

66. • Structure of Large Intestine
• The 4 layer of tissue in GI tract are present in caecum, colon, rectum & the anal
canal
1. Mucus
2. Sub mucus
3. Muscle
4. Serous
1) Mucus: It consist Goblet cells which produce mucus to act as a lubricant.
2) In the sub mucosal layer there is more lymphoid tissue providing non
specific defense against microbes
3) Muscle: The arrangement of the longitudinal & circular muscle fibers.
4) Serosa forms the outermost layer. It protect from friction between
abdominal organs and the surrounding muscles

67. • Arterial supply of Large intestine:
Superior mesenteric artery, inferior
mesenteric artery, and The middle and
inferior rectal arteries
• Venous drainage: the superior and
inferior mesenteric veins & internal iliac
veins.
• Nerve Supply:
• Parasympathetic innervations:
• The vagus nerve (CNX), responsible for
increasing secretomotor activity.
• Sympathetic innervations: The T10-L2
thoracolumbar outflow of sympathetic
fibers are responsible for the inhibitory
activity.

68. • Functions of the Large Intestine:
• Absorption of water: Absorption of large amount of water & mineral salts,
vitamins and some drugs are also absorbed in large intestine.
• Microbial activity: The large intestine is heavily colonized by certain types of
bacteria, E.g.: E.coli, Enterobacter aerogenes, & Streptococcus faecalis
• Mass movement: wave of strong peristalsis sweep along the transverse colon
forcing its contents into the descending and sigmoid colons. This is known as
mass movement
• Defecation: the process of eliminating undigested & waste as fecal matter.
• Constitution of feces: The feces consist of a semisolid brown mass.It contain
water (60 to 70%), Fiber, microbes, Epithelial cells shed from the walls of the
tract, Fatty acids & Mucus secreted by the epithelial lining of the large intestine.
• Goblet cells: produce mucus to act as a lubricant