DIGESTION The What: Convert big food items into small molecules move them from gut to blood. The Where: In a long tube called the GI tract = gut.
DIGESTIVE SYSTEM MOUTH + GI TRACT + ACCESSORY ORGANS
MOUTH - where it all begins. The entry point Only part of the process that is enjoyable: taste & smell. Enjoyment sustains eating.
Food is swallowed when piece size is acceptably small. Adults usually have 32 teeth (28 w/o wisdoms) of 4 basic types.
½ of each jaw has all teeth types INCISORS = biting/cutting CANINES = tearing PREMOLARS = grinding MOLARS = crushing Wisdoms are molars that have a variety of problems.
Swallowing food is possible due to a cooperation between tongue and saliva. Almost impossible to eat w/o saliva Saliva contains a starch-digesting enzyme: amylase. 3 main glands
Swallowing Muscular tongue manipulates food, mixing it with saliva to form a BOLUS.
Breathing Stops!
Esophagus is a long muscular tube 1 Function: Bolus Transport
PERISTALSIS is a rhythmic, wave length contraction of smooth muscle that propels food.
The basic anatomy of the GUT starts with the esophagus Smooth Muscle Lumen
Sphinctors Muscular valves that control lumen size Relaxed L Contracted Smooth Muscle
Sphinctor Locations Esophagus Stomach Small Intestine Large Rectum Intestine + Anus WHY?
Food residence time in stomach controlled by 2 sphinctors (~ 6 hr)
1 2 3 The stomach is a mechanical churn
STOMACH lining 1 2 3 complexity
Exiting Stomach: ACID CHYME Next section: SMALL INTESTINE Intestine Function 1 Enzymatically attack acid chyme yielding Building Blocks Function 2 Absorption - transporting BB from lumen into bloodstream
A B S O R P T I O N
Good Summary Slide
We ve covered the mouth and gut not enough for nutrient extraction. ACCESSORY ORGANS are necessary: Pancreas & Liver.
I FOOD M BUILDING BLOCKS ABSORPTION P O R T A N T
LARGE INTESTINE Large in diameter but relatively short. Does not secrete enzymes does not absorb BB. Does absorb water and salts. Controls water content of feces (constipation/diarrhea)
Rat?
1 Defecation: 2 Sphinctors 2 (babies?)
FECES * Undigested food (e.g. fiber) * Water * Common bacterial component is nonpathogenic E. coli. Odor? Odiferous breakdown products come from bacteria in large intestine.
MAJOR FOOD GROUPS PROTEINS -- important because breakdown products are AAs which are bb. Of the 20 AAs, body can produce 11 by itself. Other 9 must come from diet and are called ESSENTIAL AAs.
Individual meats are a complete source all 20 Individual vegetables/grains are incomplete sources. diverse vegetarian diet is complete
CARBOHYDRATES Simple sugars and complex carbohydrates Yes simple sugars are critical for cellular energy. But candy and soft drinks are not high quality food because they represent empty calories. Also, sweetness promotes overeating.
Nutritionists urge eating complex carbohydrates (polysaccharides) They are found in well-rounded foods bread, rice, cereal.
FATS We are simultaneously obsessed/terrified of dietary fat. Obsession is reflected in our diets: fried food, fast food, snack food. The terror comes from the media amplifying medical reports. Fat linked to cancers: breast, prostate, colon, pancreas
Fats contain much energy: Proteins = 4.1 Kcal/gram Carbohydrates = 4.1 Kcal/g Fats = 9.2 Kcal/g
Medical advice fluctuates but a recurring theme is less fat is good. Not clear how far to reduce dietary fat.. liver will make fat if necessary. One ESSENTIAL FATTY ACID meaning we must get it from our diet: Linoleic Acid.
CHOLESTEROL - the hysteria molecule. Everybody over the age of 40 knows their number. It s a critically necessary part of our biochemistry. Cell membranes, hormones, vitamin D. Cholesterol is transported around body by protein carriers: - HDL = high density lipoproteins - LDL = low density LDL has been correlated with cardiovascular disease.
L
The Rehnberg Diet based on extensive research while in Beer & Chips college Beer & Wings Beer & Pizza
BMI = ( Weight in Pounds / ( Height in inches x Height in inches ) ) x 703
% of population classified as obese BMI > 30
Children today will have lives shorter than that of their parents
A different problem Anorexia
Weight gain and loss is conceptually simple In practice difficult for many people
For the morbidly obese Bariatric Surgery is a last ditch effort to reduce body weight NIH recommends it for those with BMI > 40
Bariatric Procedures