Mouth to Stomach

1
Mouth to Stomach

• p. 455-461 470-474

2
Parts of the Digestive System

• Alimentary canal / GI tract
• Accessory organs

3
The Alimentary Canal
4
(No Transcript)
5
The Oral Cavity

• Vestibule
• Tongue
• Papillae
• Lingual frenulum
• Mastication

• Functions ingestion, mechanical chemical
  digestion (salivary glands)

6
Teeth
7
Pharynx Esophagus

• 3 regions of pharynx
• Srat. squam. epi.
• Functions
• No digestion or absorption
• Swallowing
• Peristalsis

8
Stomach Main Functions

• Temporary food storage
• Mechanical chemical digestion
• Limited absorption alcohol, aspirin

9
Stomach Anatomy

• Cardiac sphincter
• Pyloric sphincter
• Greater lesser curvatures

• Greater lesser omenta
• Fat deposits
• Lymph nodes

10
Modifications of theStomach Wall

• Mucosa simple columnar w/ goblet cells
• Gastric pits lead into tubular gastric glands,
  which secrete gastric juice
• Muscular layer has THREE layers of muscle
• Rugae folds of stomach wall allow its size to
  increase after a meal
• Stretch stimulates muscle contractions

11
Gastric Glands
12
Gastric Juice

• Gastric glands are lined with
• Chief cells secrete pepsinogen (inactive form
  of the enzyme pepsin)
• Parietal cells secrete hydrochloric acid (HCl)
• HCl converts pepsinogen into pepsin, an enzyme
  that begins protein digestion animation
• Enteroendocrine cells secrete gastrin (a
  hormone)
• Goblet cells near opening of gastric glands

13
Control of Gastric Juice, contd

• Stimuli (sight, smell, taste) cause
• Gastric juice secretion, which leads to
• Gastrin (hormone) secretion
• Increases secretion of gastric juice
• Is this a positive or negative feedback
  mechanism?
• POSITIVE!
• Chyme (partially digested food) entering duodenum
  inhibits gastric juice secretion

14
Action of Gastrin