Digestive System Anatomy and Function
Processes of the Digestive System
1. Secretion
- endocrine: hormones into blood
- exocrine: enzymes into lumen
2. Digestion
- mechanical/chemical
- most in small intest*
3. Motility
- coordinated muscle contractions along the gastro tract
- too fast? diarhea
- too slow? constipation
4. Absorption
- nutrients from food (lumen) --> cells (transcellular) --> blood
- most in small intest*

(fig 11.0)

(fig 11.1)

Mouth
- no absorption
- mechanical digest begins & digest of carbs
- saliva secreted by 3 exocrine glands
- saliva contains proteins and ions

(fig 11.2)

Salivary Glands
1. Parotid gland: watery liquid & salivary amylase (carb digest)
2. Submanibular gland: thicker liquid, mucus & amylase
3. Sublingual gland: more mucus & less amylase

Stages of Swallowing
1. Voluntary Stage
- chewing
- only voluntary stage*
2. Pharyngeal Stage
- food --> pharynx
- involuntary*
3. Esophageal Stage
- food down esophagus --> stomach
- involuntary*

Mastication
- mechanical manipulation of food into a bolus
- chemical digestion --> salivary amylase
- lingual lipase secreted in mouth but not activated*

Summary of Mouth
Secretion
- saliva (varying composition)
- enzymes: salivary amylase & lingual lipase (inactive)
Digestion
- mechanical & chemical
- salivary amylase --> carb digest
Motility
- mouth=mastication (voluntary)
- esophagus=peristalsis(involuntary)
Absorption
- none

Peristalsis
- bolus down esophagus via coordiated contractions & relaxations
- circular & longitudinal muscles
- medulla oblongata
- secondary peristalsis if food lodged in esophagus

The Stomach
fig11.3

	Criado por efeuneke mais de 10 anos atrás

Notas sobre Gastrointestinal Physiology, criado por efeuneke em 03-04-2014.