Phases Of Stomach |



Digestive System
Q. What type of cell structure is needed for various parts of the digestive
 trust? A drummed/Simple? Absorption? Excretion?
Q. Evolutionarily, what might be of indicator of a simplistic or early 
organism?



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Three Phases of Stomach
1.Cephalic Phase- 1.  Prepares stomach for digestion, 2, Messages sent 
to medulla oblongata, 3, Postaganglionic nerves stimulate the production 
of HCL, pepsin, intristic factors and mucus
2.Gastric Phase- 1. Greatest volume of gastric Secretion (stomach becomes 
distended) 
		2.Hormones stimulate the four components of digestion.
3.Intestinal Phase- 1. Acidic chyme enters the duodenum
 		  2. Causes hormones to be released 
  3.Gastrin is released to further breakdown stomach if the PH of chyme 
is 2.0 or lower, secretion is released which inhibits gastrin secretions.
Movements in stomach
Contractions happen every 20 seconds causing 2 types of movement.
1. Mixing Waves- Pressure on either side forms chyme
2. Peristaltic Wave- Pressure forces chyme into duodenum
 	Problems if stomach empties to fast or to slow?
1. Not enough digestion.  Damage walls of the intestine
2. Damage stomach

Small Intestine
Secretions- 
1. Keep chyme a liquid
2. Protect wall from acidic chyme
3. Produces by mucosa, liver, pancreas

Epithelial Cells-
1. Peptidase breaks peptide bond
2. Disaccaridase break down disaccharides
3. These nutrients are then absorbed 
  Mucus- Protects, keeps Ph high produced in duodenum; by goblet
  Hormones from mucosa stimulate liver and pancreatic secretion
Movement
	1. Segmental- inward pressure on chyme/bolus.  Used to churn 
to acid in digestion
	2. Peristaltic- Pressure releases in front to move chyme.
Absorption
	Done in duodeum and jejunum and ileum
Liver
	Purpose- Detoxify harmful chemicals.
		Stores and processes nutrients…….HOW?
A. Bile- neutralizes stomach acid by increasing the efficeny of fat
digestion/absoption (fat inhibits proper digestion)
Pancrease- Location: lower portion of stomach by duodeum
	Function:  Neutralise acid chyme is small intestine by secreting 
	bicarbonate ions.
	3. This raises the PH and stops pepsin digestion and allows for 
	pancreatic enzymes to do their work.   (Important for digestion 
	of all foods)

Exocrine Activity of Pancreas
1. Controlled by hormones
2. Secretion initiates the release of a watery soln that contains bicarbonate
 ions.  (Acid chyme stimulates release enzyme rich soln.  This is as 
responsible to fatty acids and amino acids in duodenum.
Large Intestine
	18 to 24 hours for material pauses through
	Several microorganisms live in colon.  Many synthesize substances 
that are absorbed
	18 to 12 hours contractions called mass movements propel contents 
to anus after a meal.
	Carbohydrates
  Starches, cellular, glycogen, sugar
	1. Amylase (enzyme) breaks down carbs in mouth from poly to di (5%)
	2. Disaccurides, are broken down in duodenum by di-ase
	3. Mono’s are taken up by active transport through intestinal 
	   epithelial cells 
	4. Converted to glucose by liver glucose
	5. Insulin controls the rate of diffusion into cells.

Lipids
1.Saturated- single bond. It is solid at room temperature.  Found in meat, 
airy, products, eggs, nuts, coconut oil, and palm oil/
2.Unsaturated- one or more double bonds.  Fish and most plant oils
Digestion
1. Emulsification- (from large to small droplets)---; bile salts are 
the agent for the process.; Digestive enzymes can only work at surface 
of lipid.  This is why surface area increases 
by dividing lipid cells.
2. The pancreas and intestinal absorptive cells and digests lipids 
secrete lipase.