1. Introduction to the Digestive System
Dr. Munguti J.K

2. Outline The digestion process Divisions of the digestive system
General structure of the hollow GIT
Accessory GI glands

3. Digestive Processes Ingestion Propulsion Mechanical digestion
Chemical digestion
Absorption
Defecation

4. Divisions: Alimentary canal Accessory Digestive Organs
Continuous, muscular digestive tube winding throughout the body
Digests and absorbs food particles
Consists:
Oral cavity, Pharynx, Esophagus, Stomach, Small and Large Intestines
Accessory Digestive Organs
Contains the following organs:
Teeth, Tongue, Gallbladder, Salivary Glands, Liver, and Pancreas

5. General Structure Four basic layers: Mucosa Submucosa
Lining epithelium
Mucosal glands
Lamina propria
Muscularis mucosa
Submucosa
Muscularis externa
Serosa/adventitia

6. Oral Cavity Two components Roof: Contains Oral cavity proper Vestibule
Hard and soft palates
Contains
Tongue
Teeth
Accessory salivary glands

7. Tongue Roughened dorsal surface Functions Filiform papillae
Foliate papillae
Fungiform papillae
Circumvallate papillae
Functions
Sensory organ
Cleaning of the oral cavity
Deglutition
Help in mechanical digestion

8. Salivary Glands Main salivary glands Accessory salivary glands
Parotid
Submandibular
Sublingual
Accessory salivary glands
Functions
Moisten food
Clean the oral cavity
Chemical digestion
Dissolve chemical substances
Lubrication

9. Teeth Deciduous Permanent Incisors- cutting and shredding
Canines- piercing and tearing
Molars- grinding
Premolars- grinding and crushing

10. Oesophagus Muscular tube Has regional constrictions/ blood supply
Skeletal muscles (upper 1/3)
Smooth muscle (lower 1/3)
Has regional constrictions/ blood supply
Regional changes in mucosal epithelium

11. Stomach Parts Greater and lesser curvatures Mucosal folds: rugae
Cardiac
Fundus
Body
Pylorus
Greater and lesser curvatures
Mucosal folds: rugae
3 – layered muscular layer
Longitudinal
Circular
Oblique

13. Stomach Cells types? Functions Chemical digestion Physical digestion
Temporary “storage” of food
Disinfection
Absorption of alcohol
Production of intrinsic factor
Production of hormones

14. Small Intestines Major site for digestion and absorption Cell types?
Duodenum
Jejunum
Ileum
Cell types?
Receives the pancreatic juice
And bile

15. Duodenum Four parts 25 – 30 cm long Secretes intestinal fluid
Superior
Descending
Transverse
Ascending
25 – 30 cm long
Secretes intestinal fluid
Receives the:
CBD
Pancreatic duct

16. Jejunum and Ileum Proximal 2/5 Left upper quadrant Larger diameter
Thicker walled
Less prominent arterial arcades
Longer vasa recti
More mesenteric fat
Distal 3/5

18. Appendix Has lymphoid tissues in its walls Suspended by mesoappendix
Varied location
Retrocecal
Retrocolic
Pelvic
Subcecal
Preileal
Postileal

19. Rectum Continuation of sigmoid colon 3 lateral flexures
Rectosigmoint junction
3 lateral flexures
Superior/ intermediate/ inferior
Terminal segment – ampulla
Lacks
Taenia coli,
Haustra
Omental appendices

20. Anal Canal Extraperitoneal Demarcated from rectum by 3 – 5 cm long
Anorectal ring/ flexure
3 – 5 cm long
Contains the anal sphincters

21. Salivary Glands Main glands Accessory glands Produce saliva Parotid
Submandibular
Sublingual
Accessory glands
Produce saliva
Functions

22. Liver and Gallbladder In the right hypogastrium & epigastrium
Two main surfaces
Diaphragmatic
Visceral

23. Liver – Functions & Relations
Secretory
Excretory
Energy metabolism
Storage functions
Immune?

24. Pancreas Mainly retroperitoneal Several parts Two components Head
Uncinate process
Neck
Body
Tail
Two components
Exocrine
Endocrine

25. Review The digestion process Divisions of the digestive system
General structure of the hollow GIT
Accessory GI glands