Transcript SENSES (Ch 14, pp. 265-291)

DIGESTIVE SYSTEM
- Transfers nutrients, salts, H2O and vitamins in food
from external to internal environment
Anatomy:
Digestive tract (gastrointestinal (GI) tract)
Mouth -> Pharynx -> Esophagus
-> Stomach
-> Small intestine
-> Large intestine -> Anus
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DIGESTIVE SYSTEM
Digestive System:
Mouth:
- teeth = mastication (incisors, canines, molars)
-3 pairs salivary glands secrete saliva:
1) moistens and lubricates food
2) amylase
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DIGESTIVE SYSTEM
Digestive System Organs
Pharynx and Esophagus
- transport food and water to stomach
- swallowing reflex: epiglottis
As food approaches stomach, sphincter relaxes so
food can go into stomach
Sphincter closes -> Prevents acid reflux
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DIGESTIVE SYSTEM
Digestive System Organs
Stomach
- STORES food
- gastric juice = pepsin (Enzyme) and HCl
(low pH!)
- Digestion/churning
- No Absorption of food
- Gastric mucosal barrier (thick)
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DIGESTIVE SYSTEM
Digestive System Organs
Small Intestine
- Most digestion occurs here
- Digestion by small intestine & pancreatic
enzymes
- Most absorption
= villi: contains capillaries & a lacteal
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DIGESTIVE SYSTEM
Digestive System Organs
Small Intestine
Digestion in small intestine depends on
substances secreted by 3 accessory organs:
i) Pancreas
- pancreatic juice
= digestive enzymes
1. pancreatic amylase
2. trypsin
3. lipase
(another function?)
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DIGESTIVE SYSTEM
Digestive System Organs
Small Intestine
Digestion in small intestine depends on substances
secreted by 3 accessory organs:
ii) Liver
1) secretes bile salts
2) metabolic processing
3) detoxification
4) stores glycogen, fats, minerals, vitamins
What is glycogen? Why is it important?
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DIGESTIVE SYSTEM
Digestive System Organs
ii) Liver
- Bile = bile salts, but they are stored in…
iii) Gallbladder
Bile => emulsification of fat
-> Digest fat -> Absorbed into lacteal
*** Nutrient-rich blood from Small Intestine
-> Hepatic Portal System
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DIGESTIVE SYSTEM
Digestive System Organs
5) Large Intestine
5 x longer to move through than small intestine
mass movements (every 8-12 hrs; more often
after meals)
absorption of salts/water, secretion of mucus,
microorganism activity
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DIGESTIVE SYSTEM
Control of Digestion
A. Neural
- Involuntary nervous system
- Sight and SMELL stimulate gastric juices
(stomach) via neural activity
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DIGESTIVE SYSTEM
Nutrition
B. Micronutrients are also required:
1) Vitamins
- 13 different vitamins
- Vitamin D => bone strength
- Vitamin C => immune system
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DIGESTIVE SYSTEM
Nutrition
2) Minerals
a) Macrominerals
- more than 100 mg/day
- includes: sodium
magnesium
phosphorus
chlorine
potassium
calcium
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DIGESTIVE SYSTEM
Nutrition
2) Minerals
b) Microminerals
- less 20 mg/day
- very specific functions
- e.g., iron => hemoglobin
iodine => thyroid hormone
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