Digestive Function

1
Digestive Function

• Digestive system the organ system that processes
  food and then voids it
• Ingestion intake of food
• Digestion mechanical, chemical breakdown of food
  so it is useable by body
• Absorption uptake of nutrients to be delivered
  by the blood and lymph
• Defecation voiding of undigested residue

2
Digestion location

• Mesenteries loose connective tissue that suspend
  the intestine and stomach, this causes freedom of
  movement while processing food
• Most of digestion process occurs under the
  diaphragm in the stomach and intestine

3
Mouth

• Oral cavity most of the mechanical processing
  occurs here
• Process of chewing mixes food with saliva that
  contains enzymes that break down simple starches
  to be absorbed by vessels in cheek wall (Bolus)
• Know the lingual Papillae
• Function and types of teeth, fig 25.6

4
Swallowing

• The pharynx starts the process as food passes the
  upper esophageal sphincter closes, allowing food
  to enter esophagus without air
• As food passes through the esophagus smooth
  muscle that surrounds the esophagus contract in a
  wave like motion called peristalsis to push food
  down

5
Stomach

• The main function is to mix bolus with stomach
  acid (Chyme)
• Chemical and mechanical digestion occur in the
  stomach
• J-shaped organ with the lesser and greater
  curvature
• Broken down into 4 regions cardiac, fundus,
  corpus, and pyloric

6
Stomach

• The walls made of several types of cells
• Mucous cells produce thick mucus layer that
  protects tissue from stomach acid
• Stem cells cells that are in constant production
  to replace cells that die
• Parietal cell produce acid, intrinsic factor
• Chief cells produce pepsinogen
• Enteroendocrine cells produce hormones that
  regulate digestion

7
Secretions

• Stomach acid high concentration HCl with a Ph of
  0.8
• Pepsinogen activated by HCl and changes into
  pepsin to digest protein
• Intrinsic factor key for Vit B12 uptake

8
Vomiting

• Vomiting forceful ejection of chyme
• Controlled by the emetic center found in the
  medulla oblongata
• Nausea sense of stomach discomfort
• Retching precedes vomiting, thoracic expansion
  and abdominal contraction dilates esophagus and
  relaxes lower esophageal sphincter, chyme travels
  up but settles in stomach

9
Vomiting

• Vomiting occurs when abdominal contraction and
  thoracic pressure force the upper esophageal
  sphincter open
• Projectile vomiting is the sudden onset of
  vomiting without nausea and retching