- Contents of Digestive System
01. Definition of Digestive System.
02. Parts of digestive system.
03. Function of digestive system.
04. Oral Cavity.
05. Tongue.
06. Teeth.
07. Salivary Gland.
08. Saliva.
09. Pharynx.
10. Oesophagus.
11. Stomach.
12. Small Intestine.
13. Duodenum.
14. Large Intestine.
15. Difference between large and small intestine.
16. Vermiform Appendix.
17. Liver.
18. Biliary tree or biliary apparatus.
19. Gall Bladder.
20. Bile.
21. Pancreas.
22. Gastric Juice.
23. Pancreatic Juice.
1| DIGESTIVE SYSTEM :
The human digestive system or alimentary canal is a complex series of organs and glands involved in processing of food, extend from oral cavity to the anal canal. It is also known as the gastrointestinal tract or GIT.
2 | FUNCTION OF DIGESTIVE SYSTEM :
a. Ingetion and movement of food through the alimentary canal.
b. Digestion of food by the secretion of digestive juices.
c. Absorption of digestive products water and electrolytes.
d. Transport of absorbed substance to the circulation of blood.
e. Regulation of acid base and water balance.
3 | PARTS OF DIGESTIVE SYSTEM :
1. Oral Cavity.
2. Pharynx :
a. Nasopharynx
b. Oropharynx
c. Laryngopharynx.
3. Oesophagus :
a. Cervical oesophagus.
b. Thoracic oesophagus.
c. Abdominal oesophagus.
4. Stomach.
5. Small Intestine :
a. Duodenum.
b. Jejunum.
c. Ilium.
6. Large Intestine :
a. Caecum
b. Ascending Colon
c. Descending Colon
d. Transverse Colon
e. Sigmoid Colon
f. Rectum.
g. Vermiform Appendix.
h. Anal Canal .
4 | ORAL CAVITY :
- It is the route of entrance to the alimentary canal.
• Function : Receive, mastication, chewing mixing and helping in diglutition of food.
• Contents :
A. Lips B. Palate C. Tongue
D. Teeth E. Salivary Gland
A. Lips : a. Skin ( Outer.)
b. Mucous Membrane ( Inner.)
c. Orbiclaris oris muscle.
d. Labial Gland.
B. Palate : -Two types :
a. Hard Palate( Anterior one third.)
b. Soft Palate ( Posterior two third.)
5 | C. TONGUE :
- The tongue is a solid conical muscular organ covered by the mucous membrane.
* Function of tongue :
a. It is the primary organ of taste.
b. Help in the mastication.
c. It is essential for deglutition.
d. Responsible for speech by phonetic articulation.
e. The tongue also serve as a natural means of cleaning one's teeth.
* Parts of tongue :
a. Oral or papillary part :
- Fungiform Papillae.
- Filiform Papillae.
- Vallate Papillae.
b. Pharangeal part.
* Muscle of tongue or mastication :
A. Extrinsic Muscle :
- Palatoglossus.
- Styloglossus.
- Hypoglossus.
- Geniglossus.
B. Intrinsic Muscle :
- Superior Longitudinal.
- Inferior Longitudinal.
* Blood Supply to the tongue :
A. Artery :
- Lingual artery.
- A branch of External Carotid Artery.
- Tonsillar and ascending pharyngeal arteries.
B. Venous :
- Lingual vein.
- Facial vein.
- Jugular vein.
6 | D. TEETH :
- Tooths are placed in the bony socket by maxilla above and mandible below.
* Types of teeth: Two types
A. Temporary or Deciduous : 20
- Incisor = 4
- Canine = 2
- Molar = 4
B. Permanent teeth : 32
- Incisor = 4
- Canine = 2
- Molar = 6
- Premolar = 4
* Wisdom teeth : It is the last molar tooth that erupts last at the age of 25 years.
* Structure of teeth :
A. Enamel : It is the hardest part of the body.
B. Dentine : It contains calcified material as that of bone.
C. Dental pulp : This is the fibrous tissue containing blood vessels, nerves and lymphatics.
* Function of teeth :
a. The incisor's are cutting teeth, the canine are for holding and tearing and the molars are for grinding of food material.
b. Helps in speech.
c. Organ of self defence.
d. Esthetics : Part of nice smiling and self esteem.
7 | SALIVARY GLAND :
- Salivary glands are a number of glandular structures that produce saliva. 
Major
Minor* Major Salivary Glands :
A. Two parotid glands : It secrets purely serous of fluid.
B. Two submandibular glands : It secrets both serous and mucous type of fluid.
C. Two Sublingual gland : It secrets both serous and mucous type of fluid.
*Minor Salivary Glands :
A. Labial Gland. C. Palatoglossal
B. Buccal Gland. D. Lingual.
* Function of Salivary Gland :
a. Moistening dry foods to aid swallowing.
b. Providing a medium for dissolved and suspended food materials that chemically stimulate taste buds.
c. Buffering of contents of the oral cavity through its high concentration of bicarbonate ions.
d. Digestion of Carbohydrates by the digestion enzyme alpha-amylase.
e. Controlling the bacteria Flora because of the presence of the antibacterial enzyme lysozome.
8| SALIVA :
- The watery mixture of secretions from the salivary and oral mucous glands that lubricates chewed food and moistures the oral walls.
* Composition :
A. Water : 99.5%
B. Solid : 0.5%
a. Organic :
1. Enzymes -
- Ptyalin (Salivary amylase)
- Lysozyme.
2. Mucous.
b. Inorganic :
1. Cation -
- Sodium ( Na+)
- Potassium ( K+)
2. Anion -
- Chloride ( Cl- )
* Properties of Saliva :
A. Volume : 1L - 1.5L /day
- Parotid Glands 25%
- Submendibular Glands 70%
- Sublingual Glands 5%
* Function of Saliva :
A. Mechanical Function :
a. It keep the mouth moist and thus helps in speech.
b. It facilities swallowing.
c. Makes the food suitable for digestion.
d. Acts as a lubricant.
B. Helps in taste.
C. Digestive function : It break down boiled starch into maltose due to presence of enzyme ptyalin.
D. Excretory function : It excretes urea, some heavy metals, thiocyanates, iodine, penicillin etc.
E. Water balance.
9 | PHARYNX :
- Pharynx is a wide musculo-membranous tube, situated the nose, mouth and larynx. Length → 12-14 cm.
* Parts of Pharynx :
a. Nasopharynx.
b. Oropharynx.
c. Laryngopharynx.
A. Nasophyranx : It is the upper part of pharynx situated behind the nose and above the level of soft palate.
B. Oropharynx : This is the middle part of pharynx situated behind the oral cavity.
C. Laryngopharynx : It is the lower part of pharynx situated behind the larynx. It extends from upper border of epiglottis to the lower border of cricoid cartilage.
* Layers of Pharynx :
a. Areolar coat.
b. Muscular coat.
c. Submucous coat.
d. Mucous membrane.
* Nerve supply of Pharynx : Pharynx is supplied by pharyngeal plexus, which is formed by branch of vagus and glossopharyngeal nerves.
* Blood supply :
A. From branches of external carotid artery.
B. The veins drains into the internal jugular and facial veins through pharyngeal venous plexus.
* Muscles : 1. Circular muscle.
2. Longitudinal muscle.
10 | OESOPHAGUS :
- Oesophagus is a narrow muscular joining the pharynx and stomach and forms a food passage between them. Length : 25cm.
* Parts of oesophagus :
a. Cervical Part : 4 cm
b. Thoracic Part : 20 cm
c. Abdominal Part : 1 cm.
* Layers of oesophagus :
a. Fibrous coat.
b. Muscular coat.
c. Submucosa.
d. Mucosa.
* Blood Supply :
A. Arterial supply :
- Cervical part : Inferior thyroid artery.
- Thoracic part : Descending thoracic artery.
- Abdominal part : Left gastric artery.
B. Venous supply :
- Cervical Part : Brachiocephalic vein.
- Thoracic Part : Azygus vein.
- Abdominal Part : Left gastric vein.
11 | STOMACH :
- Stomach is the most high dialated part of the digestive tube and intervens between the oesophagus and the duodenum.
Fig : Stomach
* Capacity : a. In new born : 30-50ml
b. In adult : 1000-1500ml
*Location : The stomach lies obliquely in the upper left part of abdomen, occupying the epicastic and left hypochondriac and unbilical region.
* Parts of Stomach :
a. 2 orifices : Cardiac orifice, Pyloric orifice.
b. 2 curvature : Lesser curvature, Greater Curvature.
c. 2 surface : Antero-superior surface, Postero-inferior surface.
d. 3 subdivision : Fundus, Body, Pyloric antrum.
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