The document provides information on the structure and function of the digestive system. It begins with an overview of the basic components of the alimentary canal including the mouth, salivary glands, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anal canal, and accessory organs like the liver, pancreas, and bile duct. It then describes the layers of the alimentary canal including the peritoneum, muscle layers, submucosa, and mucosa. Specific structures like the tongue, teeth, stomach, small intestine and large intestine are examined in more detail. The functions of digestion and absorption in the mouth, stomach, small intestine, large intestine and accessory organs are

1. HUMAN ANATOMY AND PHYSIOLOGY
B. PHARMACY- 2ND SEMESTER
CHAPTER-3
DIGESTIVE SYSTEM
Guru Gobind Singh College of Pharmacy,
Yamunanagar

3. Content of Digestive system
• Introduction
• Basic structure of alimentary canal
Anatomical structure of alimentary canal
• Mouth
• Salivary gland
• Pharynx
• Oesophagus
• Stomach
• Small Intestine
• Large intestine, rectum, anal canal
Accessory organs
• Liver
• Pancreas
• Biliary tract (Bile duct, Gall bladder)

4. Structure of alimentary canal

5. Peritoneum
• The peritoneum is the largest serous membrane of the body, it is a
closed sac, containing a small amount of serous fluid with in
abdominal cavity
• It has two layers
• Parietal peritoneum
• Visceral peritoneum
Muscle layer
• Longitudinal and circular muscle layers are present. Between these
two layers blood vessels, lymph vessels and plexuses network
(Myenteric plexuses) is present.
• Longitudinal muscle layer
• Circular muscle layer

6. Submucosa
• This consist of loose areolar connective tissue containing collagen
and some elastic fiber which helps in the binding of muscle layer to
mucosa.
Mucosa
• This consist of three layers of tissue:
• Mucous membrane: formed by columnar epithelium is the
innermost layer and has three functions: Protection, secretion and
absorption
• Lamina propria: consisting of loose connective tissue, supports
blood vessels, nourish inner epithelial layer and varying amount of
lymphoid tissue that protects against microbial invades.
• Muscularis mucosa: a thin outer layer of smooth muscle that
provide involutions of mucosal layer

7. Mouth

8. Tongue
• Composed of voluntary muscle, attached by base of hyoid bone
and by a fold of its mucous membrane covering called frenulum to
the floor of the mouth. Superior surface consist of stratified
squamous epithelium.
• Function of tongue:
• Chewing (mastication)
• Swallowing (deglutition)
• Speech
• Taste

9. Teeth
• Embedded in the sockets of mandible and maxilla
• Two types:
• Temporary (Deciduous teeth: 20 teeth)
• Permanent teeth: 30-32 teeth

10. The roof of mouth

11. The section of a tooth

12. Salivary glands
1. Parotid gland
2. Submandibular gland
3. Sublingual gland

13. Pharynx
The pharynx is divided for descriptive purpose into three parts, the
nasopharynx, oropharynx and laryngopharynx. The nasopharynx is
important in respiration. The oropharynx and laryngopharynx are
passages common to both the respiratory and the digestive systems.
Food passes from the oral cavity into the pharynx then to the
oesophagus below, with which it is continuous.

14. Oesophagus
• The oesophagus is about 25
cm long and about 2 cm in
diameter and lies in the
median plane in the thorax
in front of the vertebral
column behind the trachea
and the heart.
• cricopharyngeal sphincter
• cardiac or lower
oesophageal sphincter

15. Regions
of
Abdominal
cavity

16. Stomach
• The stomach is a J-shaped
dilated portion of the
alimentary tract situated in
the epigastric, umbilical and
left hypochondriac regions of
the abdominal cavity.
• The stomach is continuous
with the oesophagus at the
cardiac sphincter and with
the duodenum at the pyloric
sphincter. It has two
curvatures.
• The stomach is divided into
three regions: the fundus, the
body and the antrum.

17. Gastric juice and function of stomach
• 2 liter gastric juice secreted daily by specialized secretory glands in
the mucosa composed of:
• Water
• Mineral salts
• Mucous secreted by goblet cells
• Hydrochloric acid
• Intrinsic factor
• Inactive enzyme precursors: Pepsinogens secreted by chief cells in
the glands.
secreted by Parietal cells

18. Function of gastric juice
• Water liquefies the food swallowed
Hydrochloric acid:
• Acidify the food and stop the action of salivary amylase
• Kills ingested microbes
• Provide the acid environment needed for the action of pepsins.
• Pepsinogen are activated to pepsin by hydrochloric acid and by pepsin
already present in the stomach. These enzyme begins the digestion of
proteins. Pepsin have evolved to act most effectively at very low pH,
between 1.5 and 3.5.
• Intrinsic factor: absorption of vit. B12 from ileum.
• Mucous prevent mechanical injury to stomach.
Secretion of gastric juice:
• Cephalic phase
• Gastric phase: Entero-endocrine cells, duodenum secrete the hormone
gastrin which act on stomach through blood and increase the release of
gastric juice
• Intestinal phase: enterogastrone, secretin and cholecystokinins (Brunner
cells).

19. Function of stomach
• Temporary storage: allowing time for the digestive enzyme to act.
• Chemical digestion: pepsin break proteins into polypeptides
(amino acids)
• Mechanical breakdown
• Limited absorption for water, alcohol, and some lipid soluble drug
• Non-specific defense against microbes
• preparation of iron for absorption
• Production and secretion of intrinsic factor
• Regulation of passage of gastric content into the duodenum

20. Small intestine
• Continue with the stomach at pyloric sphincter. It is about 2.5 cm
in diameter and 5 meter long. Lies in abdominal cavity surrounded
by large intestine. It comprises three parts:
• Duodenum: It is about 25 cm long and curves around the head of
pancreas. Secretion from gall bladder and pancreas merge in a
common structure called hepato-pancreatic ampulla and enter the
duodenum at duodenal papilla, the duodenal papilla is guarded by
a ring of smooth muscle called heapto-pancreatic sphincter (of
oddi)
• Jejunum: middle section of intestine and is about 2 meter long
• Ileum: it is terminal section is about 3 meter long and ends at the
ileo-caecal valve which control the flow of food from ileum to
caecum.

21. Intestinal juice
• Around 1500 ml od intestinal juices secreted daily by the glands of
small intestine. It is slightly basic and consist of water, mucus and
mineral salts.
Chemical digestion in small intestine:
When acid chyme passes into the small intestine it is mixed with
pancreatic juice, bile and intestinal juice, and is in contact with the
enterocytes of the villi. In the small intestine the digestion of all the
nutrients is completed:
• carbohydrates are broken down to monosaccharides
• proteins are broken down to amino acids
• fats are broken down to fatty acids and glycerol.

22. Pancreatic juice:
Pancreatic juice enters the duodenum at the hepatopancreatic
ampulla and consists of:
• water
• mineral salts
• enzymes:
— amylase
— lipase
• inactive enzyme precursors:
— trypsinogen
— chymotrypsinogen
— procarboxypeptidase.

23. Large intestine
• 1.5 meter long, beginning at
the caecum in the right iliac
fossa and terminating at
rectum and anal canal.
• The Caecum: First part of large
intestine, continuous with the
ascending colon superiorly
• Vermiform appendix about 8 o
9 cm long.
• The colon: Ascending colon,
transverse colon, descending
colon and sigmoid colon
• The rectum: slightly dilated
portion of the large intestine
about 13 cm long. Leads from
sigmoid colon and terminating
at anal canal
• The anal canal: This is a short
passage about 3.8 cm long long
in adults and leads from the
rectum to the exterior

24. Function of large intestine
• Absorption: water, mineral salts, vitamins, and some drugs are also
absorbed into blood capillaries from small intestine
• Microbial activity: heavily colonized by certain bacteria for the
synthesis of vitamin K and folic acid . They include E. coli,
Enterobactor aerogens, Streptococcus faecalis and Clostridium
perfringens.
• Mass movement
• Defaecation

25. Pancreas
• Pale grey gland about 60 g
• Exocrine gland: consist of
large number of lobule made
up of small acini, the wall of
which consist of secretory
cell. Each lobule is drained by
a tiny duct and these unite to
form pancreatic duct
• Endocrine gland: group of
cells, the pancreatic islet,
endocrine pancreas secrete
the hormone insulin and
glucagon

26. Liver
• Largest gland in the body weighing between 1 and 2.3 kg, situated
in upper part of abdominal cavity. The liver has four lobes.
• Two are larger right lobe and smaller wedge shaped, left lobe, one
is caudate lobe and one is quadrate lobe (on posterior surface).

28. Metabolism of Hemoglobin