By:M. Thiru murugan Unit - 7 Structure and functions of the alimentary tract & is accessory organs. The process of digestion, absorption & metabolism of food constituents 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 & Excretion It is started from mouth and ended at anal canal Parts of Digestive System Accessory organs: Teeth Tongue Salivary glands Liver Gallbladder Pancreas Diagram Functions of Digestive System Ingestion: taking of food into the GIT. i.e. eating & drinking. Propulsion: mixes & moves the contents along the GIT Digestion: breakdown of food Absorption: this is the process by which digested food substances pass into the blood for circulation. Elimination: undigested food substances removed from the GIT as feces by the process of defecation. Mouth: First part of GIT The mouth is an oval-shaped cavity inside the skull. Parts: Lips (Labia), vestibule, mouth cavity, gums, teeth, hard & soft palate, tongue and salivary glands. The mouth is also known as the oral cavity or the buccal cavity. Function of mouth: Mastication (chewing) of food Mixing masticated food with saliva Initiation of swallowing by the tongue Allowing for the sense of taste Tongue or Lingua: The tongue is a muscular organ in the mouth. Small parts called papillae give the tongue its rough structure. Many taste buds present on the surfaces of the papillae Taste buds are sensory organs that are found on your tongue and allow you to experience tastes that are sweet, salty, sour, and bitter Function of tongue: Mastication Deglutition Speech Taste Oral cleaning Teeth: The teeth are the hardest white in oral cavity. There are 20 temporary or deciduous teeth(10 in each Jaw 4 incisors, 2 canines & 4 molars) The permanent or secondary teeth 32 teeth(16 in each jaw - 4 incisors, 2 canines, 4 premolars & 6 molars ) Function of teeth: Chewing food Cutting and grinding food speech Structure of tooth: Crown: part protrude from gums or gingiva Neck: in between crown & root Root: bottom part of the tooth; may be single, double, or triple root embedded in bone Enamel: The hardest, white outer part of the tooth. Dentin: A layer underlying the enamel. Pulp: The softer, living inner structure of teeth. Blood vessels and nerves run through the pulp of the teeth. Cementum: A layer that attach the roots of the teeth to the gums and jawbone. Periodontal ligament: Tissue that helps hold the teeth tightly in jaw. Salivary glands: It secreting saliva There are 3 types Parotid - each side of the face Submandibular - below the mandibular Sublingual – below the tongue All have ducts to supply saliva in mouth Functions: chewing and swallowing, Lubricating effect, dissolves food, taste food, Cleaning mouth, fight against pathogenic microorganisms Pharynx: Muscular tube situated behind th

1. By:
M. Thiru murugan
The Digestive system

2. Unit - 7
a) Structure and functions of the alimentary tract & is
accessory organs.
b)The process of digestion, absorption & metabolism
of food constituents

3. 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 & Excretion
• It is started from mouth and ended at anal canal

4. Parts of Digestive System
Accessory organs:
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
Primary digestive organs:
Mouth.
Pharynx.
Esophagus.
Stomach.
Small Intestine.
Large Intestine.
Rectum.
Anal canal

5. Diagram

6. Functions of Digestive System
•Ingestion: taking of food into the GIT. i.e. eating &
drinking.
•Propulsion: mixes & moves the contents along the GIT
•Digestion: breakdown of food
•Absorption: this is the process by which digested food
substances pass into the blood for circulation.
•Elimination: undigested food substances removed from the
GIT as feces by the process of defecation.

7. Mouth:
• First part of GIT
• The mouth is an oval-shaped cavity inside the
skull.
Parts:
• Lips (Labia), vestibule, mouth cavity, gums, teeth,
hard & soft palate, tongue and salivary glands. The
mouth is also known as the oral cavity or the
buccal cavity.
Function of mouth:
• Mastication (chewing) of food
• Mixing masticated food with saliva
• Initiation of swallowing by the tongue
• Allowing for the sense of taste

8. Tongue or Lingua:
• The tongue is a muscular organ in the mouth.
• Small parts called papillae give the tongue its
rough structure.
• Many taste buds present on the surfaces of the
papillae
• Taste buds are sensory organs that are found on
your tongue and allow you to experience tastes that
are sweet, salty, sour, and bitter
Function of tongue:
• Mastication
• Deglutition
• Speech
• Taste
• Oral cleaning

9. Teeth:
• The teeth are the hardest white in oral
cavity.
• There are 20 temporary or deciduous
teeth(10 in each Jaw 4 incisors, 2
canines & 4 molars)
• The permanent or secondary teeth 32
teeth(16 in each jaw - 4 incisors, 2
canines, 4 premolars & 6 molars )
Function of teeth:
• Chewing food
• Cutting and grinding food
• speech

10. Structure of tooth:
• Crown: part protrude from gums or gingiva
• Neck: in between crown & root
• Root: bottom part of the tooth; may be
single, double, or triple root embedded in
bone
• Enamel: The hardest, white outer part of
the tooth.
• Dentin: A layer underlying the enamel.
• Pulp: The softer, living inner structure of
teeth. Blood vessels and nerves run through
the pulp of the teeth.
• Cementum: A layer that attach the roots of
the teeth to the gums and jawbone.
• Periodontal ligament: Tissue that helps
hold the teeth tightly in jaw.

11. Salivary glands:
• It secreting saliva
• There are 3 types
• Parotid - each side of the face
• Submandibular - below the
mandibular
• Sublingual – below the tongue
• All have ducts to supply saliva in
mouth
• Functions: chewing and swallowing,
Lubricating effect, dissolves food,
taste food, Cleaning mouth, fight
against pathogenic microorganisms

12. Pharynx:
• Muscular tube situated behind the
nose, mouth & larynx
• Nasopharynx, oropharynx,
laryngopharynx.
• Nasopharynx involving in
respiration, oropharynx &
laryngopharynx involving
digestive system
• Food passes from mouth to
esophagus through pharynx

13. Esophagus
• fibromuscular tube, approximately
25cm in length
• It transports food from the pharynx to
the stomach.
• begins in the neck and end in
the stomach
Parts of the esophagus:
1. Cervical part
2. Thoracic part
3. Abdominal part
Function:

14. Stomach:
• The stomach is a hollow organ in the GIT.
• “J” shaped organ.
• Parts: cardia, fundus, body and pylorus:
• Two openings: the cardiac & pyloric
orifices
• Two sphincters: cardiac & pyloric
sphincters
• Two curvatures: the greater and lesser
curvatures
• Two surfaces: anterior and posterior
surfaces.

15. Gastric or stomach secretions:
 The gastric mucosa secretes 1.2 to 1.5 litres of gastric juice per day.
 Gastric juice make food particles soluble & start digestion
 It helps to converts the gastric contents to a semiliquid mass
called chyme, thus preparing it for absorption in the small intestine.
Function of stomach:
1. Storage for food,
2. Mixing and breakdown of food
3. Digestion of food
4. Produce gastric acid.

16. Pancreas:
• The pancreas is an organ of the
digestive system and endocrine system.
It secrete pancreatic juice help for
digestion
• Pancreas is divided into four
parts: Head , Neck, Body, Tail.
• Exocrine Function: It contains
exocrine glands that
produce enzymes important to
digestion.
• Endocrine function: Maintaining
proper blood sugar levels

17. Liver:
• The largest gland in our body & vital organ
• It secretes bile
• There are 4 lobes in liver: right, left,
Quadrate lobe, Caudate lobe
• The gallbladder is a pear-shaped sac lying on
the liver. It stores bile
Functions of liver:
• Secrete bile
• Metabolic function: Carbohydrate, Fat & Protein
• Protective function removes bacteria
• Storage function: Glucose
• Destruction of RBC

18. Small intestine:
• Small intestine located at abdominal
cavity, Surrounded by large intestine
• The small intestine is divided into
Duodenum, Jejunum & Ileum.
• Micro villi: tiny finger-like parts
are present on the wall of small
intestine.
• It is involving in absorption of food
• Function:Peristalsis, secreting
enzymes, absorption of food

19. Large intestine:
• It is a last part of the digestive system
4 parts:
1. Caecum & Appendix
2. Colon:(Ascending, Transverse,
Descending, Sigmoid colons)
3. Rectum
4. Anal canal
Functions:
• Absorption of water, Microbial
activity, Mass movement, Defecation

20. The process of digestion, absorption and metabolism of food
constituents
• Peristalsis: Peristalsis is a smooth muscle contractions that move the
food down through the esophagus and intestines
• Digestion Is the breakdown of food into smaller components that can
be more easily absorbed
A. Mechanical digestion: Means food is broken into smaller pieces by
teeth and peristalsis.
B. Chemical digestion: Means foods are broken down into nutrients
by Enzymes.
• Absorption: Define as the passage of nutrients into the blood or
lymphatic system. Digested food molecules are absorbed in the small
intestine.

21. The process of digestion, absorption and metabolism of
food constituents
• The remaining undigested food is stored in the rectum. It then
comes out of the rectum through the anus as faeces. This process
is called egestion
• Metabolism is the process by which your body converts what
you eat and drink into energy. It occurs after digestion and
absorption
• It has 2 process:
1. Catabolic: the breaking down of compounds
2. Anabolic: the building up (synthesis) of compounds