Digestion

Question 1

38 - General Principles of GI fct, special features, structure

Answer 1

Fct - (each part adapted for fct)

• continual supply of water, electrolytes, vitamins, and nutrients
• motor, secretory, absorptive, excretory, endocrine and blood depot, defensive fct

Needs:

1) motility
2) secretion of digestive juices and digestion
3) absorption and reabsorption of water, various electrolytes, vitamins, and digestive products
4) circulation of blood to carry away the absorbed substances
5) control via local, nervous, and hormonal systems.

Special features
- opened in both its sides.
- anatomically and functionally isolated hollow
organs, separated by sphincters.
- exocrine glands outside it
- nervous and endocrine reg sys in walls
- connected with CNS by afferent and efferent pathways.
- fct as synsctium - long and circ msc connected via gap jct

Structure
TUNICA MUCOSA:
- Lamina epithelialis (simple cuboidal epithelium)
- Lamina propria: BV, nerves, lymph follicles, glands…
- Muscularis mucosae
TUNICA SUBMUCOSA:
- BV+N, lymph, follicles, glands…
- Submucosal (Meissner’s) nerve plexus
TUNICA MUSCULARIS:
- Stratum circulare: circular smooth muscle layer
- myenteric (Auerbach’s) nerve plexus
- Stratum longitudinale: Longitudinal smooth muscle layer
- Stratum obliquum (stomach)
TUNICA SEROSA (simple squamous epithelium)/ ADVENTITIA (connective tissue)