Unformatted text preview: al lipase: digests proteins, lipids. Active only in low pH. doesn't digest fats in mouth because does not work in
neutral pH c. Digestion in the mouth
Carbohydrates some carbs digested from salivary amylase Proteins & Lipids no fat or protein digestion occurs in the mouth d. Absorption in the mouth
digesting some carbs but no signiﬁcant absorption of any nutrient in mouth e. Motility in the mouth
as we chew we use our tongue to push food to back of mouth and swallow
motility largely done by tongue here. VI. ESOPHAGUS
tube that connects mouth to stomach.
all conditions that exist in mouth carry on to esophagus
salivary amylase active all the way down esophagus.
Using peristalsis, usually aided by gravity.
what makes it possible to drink water upside down.
food is probably at its firmest right here. Leads to relatively large amount of stretch and large amount
of contraction from peristalsis
at lower end we have Lowest Esophageal Sphincter (LES) separates esophagus from stomach.
keeps conditions of esophagus and stomach separate.
Heart burn and acid reflux caused by LES not working properly VII. STOMACH
1. distensible pouch between esophagus and small intestine
2. stomach wall
rugae: roughness of stomach, sand paper covering, as food is ground up, reduce food to paste
gastric glands: secrete specific things 3. role in digestive functions
a. Secretion in the Stomach
from goblet cells
protects the stomach lining Pepsinogen
inactive form (from chief cells)
Converted to pepsin at low pH
most times secrete where it won't be activated, pepsin is first enzyme to help digest proteins HCl from parietal cells 2 roles: a. denatures proteins (not digestion) b. activates enzymes, lowers pH (pepsinogen to pepsin) Gastrin
released to how much food is there, more food more gastrin, stimulates parietal cells and stimulates chief cells
has to do with how much stretch in the stomach. Histamine
also stimulates parietal cells.
spicy foods will increase histamine. (link between people with ulcers avoiding spicy foods) VII. STOMACH (cont.)
b. Digestion in the Stomach
Carbohydrates none…why? salivary amylase denatures in pH of stomach
partially digested by pepsin Lipids
secreted lingual lipase is activated by low pH in stomach
10-30% of fat digestion is due to lingual lipase "pooling" in stomach c. Absorption in the Stomach
nutrients are NOT absorbed in the stomach
water, alcohol, and aspirin ARE absorbed here d. Motility in the Stomach
Storage - holds food until digestion proceeds and intestines ready to receive it
Mixing - waves of contraction churn food with HCl, lingual lipase & pepsin
Gastric Emptying - squirts liquified food into the small intestine
VIII. SMALL INTESTINE (Part I) longest part of the GI tract (~12 feet long)
1. several sections: duodenum, jejunum, ileum
duodenum: the ﬁrst foot, jejunum the next 4 feet, ileum the last 7 feet 2. structure of SI walls
net result of foldings and projections
SI surface area= 250 square met...
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- Fall '12
- Large intestine, salivary amylase