GASTROINTESTINAL TRACT

1
GASTROINTESTINAL TRACT

• Continuous tube, pathway of food through the body
• Four layers of tissue
• Mucosa innermost, secretes mucus
• Submucosa blood vessels, nerves
• Muscularis two or three muscle layers
• Serosa thin, slippery, connective

2
(No Transcript)
3
(No Transcript)
4
DIGESTION

• Mechanical digestion breaking food into smaller
  pieces
• Chemical digestion break bonds, produce
  monomers

5

• Mouth
• Teeth and tongue begin mechanical digestion
• Teeth slice, tear, or grind
• Crown root Enamel, dentin, pulp
• Bacteria sugar cavities
• Saliva moistens food, eases swallowing
• Salivary amylase begins starch breakdown

6
(No Transcript)
7
(No Transcript)
8

• Pharynx (throat)
• Shared space for breathing, swallowing
• Flaps close off nasal cavity, glottis
• Esophagus
• Connects pharynx stomach
• Muscular contractions peristalsis

9

• Stomach
• Expandable closed either end by sphicters
• If lower esophageal sphincter weak, heartburn
• Stomach wall three muscle layers muscularis
• Churning action liquefies food ? chyme
• Gastric pits secrete pepsinogen and hydrochloric
  acid
• Pepsinogen HCL ? pepsin
• Pepsin enzyme that digests protein to amino acids

10
(No Transcript)
11
(No Transcript)
12

• HCL kills most bacteria, tenderizes tough food
• Why is stomach lining not digested?
• Mucus protects
• Enzymes start out inactive
• Cells divide/replace quickly
• Small Intestine
• Majority of chemical digestion here
• Accessory organs liver gallbladder, pancreas
• Arrival of chyme in duodenum (1st 25 cm of the
  small intestine) ? hormone release

13

• Secretin causes sodium bicarbonate to be
  released by pancreas neutralizes stomach acid
• Cholecystokinin causes release of enzymes from
  pancreas and bile from liver
• Bile
• Consists of water, ions, cholesterol,bile
  pigments, bile salts
• Bile salts emulsify fats
• Made in the liver and stored in the gallbladder
• Gallstones can form, block ducts

14
(No Transcript)
15

• Digestive Enzymes
• Starch ? disaccharides
• Salivary amylase
• Pancreatic amylase duodenum
• Disaccharides ? monosaccharides
• Maltase, sucrase, lactase - in small intestine
• Proteins ?polypeptides ? amino acids
• Pepsin in stomach
• Others in small intestine
• Triglycerides ? Glycerol fatty acids
• Lipase in small intestine

16

• Absorption of nutrients wall of small intestine
  
• Requires a large surface area
• Circular folds, villi, microvilli
• Each villus has capillaries, lymph vessel
  (lacteal)
• Small nutrient molecules diffuse to blood
• Fats are packaged, go to lymph
• Liver adjusts glucose level, removes poisons

17
(No Transcript)
18

• Large Intestine
• Indigestible material bacteria
• Water absorbed too much ? constipation, too
  little ? diarrhea
• Bacteria typically harmless normal flora
  produce vitamins (K). live on foods we cant
  digest (produce gas)
• Indigestible material (feces) leaves rectum under
  control of sphincter muscle

19
(No Transcript)
20
NUTRIENTS

• Energy-providing fats, carbohydrates, proteins
• No energy vitamins, minerals, water
• Fats (triglycerides) not evil!!!
• Benefits include
• Cell membrane components
• Insulation and cushioning
• Carry fat soluble vitamins
• Soften skin
• Synthesis if hormones

21

• Saturated and unsaturated
• Risks of high-fat diets include obesity, cancer,
  atherosclerosis
• Cholesterol
• More of it found in LDL than HDL
• LDL carries cholesterol from liver to body cells
  excess deposited on artery walls
• HDL brings back to liver eliminated with bile

22

• Carbohydrates
• Sugars, starch, fiber
• Starch complex carbohydrates comes packaged
  with other high quality nutrients
• Fiber soluble and insoluble
• Insoluble fiber from skins tough parts of
  fruits and vegetables
• Adds bulk to material in colon, which speeds up
  peristalsis
• Contact with carcinogens reduced
• Less risk of constipation
• Soluble fiber from oat bran, apples, beans, etc.

23

• Combines with bile salts and cholesterol in small
  intestine and prevents them from being absorbed
  similar effects to insoluble fiber
• Protein
• Can be energy source, but typically used as amino
  acid building blocks
• Amino acids are not stored need 8 essential ones
  at every meal
• Animal proteins complete, but plant protein not
• Vegetarians need to think about complementing

24

• Recommended Diet
• Carbohydrates 55-60 of calories
• Fats 30 of calories (no more), unsaturated
  better
• Protein 10-15 of calories
• Calories energy measure (Kcal)
• Fats 9 cal per gram carbs protein 4 cal per
  gram

25

• Nutrition Labels
• Check serving size
• Total fat saturated unsaturated
• Total carbohydrate sugars fiber starch
• Calories per gram Fat 9, Carbohydrate and
  Protein 4
• Vitamins Minerals
• Needed in tiny amounts (metabolic purposes) if
  lacking, deficiency diseases
• Vitamins organic (carbon containing)
• Minerals inorganic

26

• Often part of enzymes (cofactors)
• Vitamins grouped as water-soluble fat soluble
• Vitamin C
• Deficiency is scurvy
• Bleeding gums, poor wound heealing, loose teeth,
  painful joints
• British sailors in 1700s citrus fruits
  (limeys)
• Now know required for collagen synthesis

27

• Vitamin A
• Example of fat-soluble
• Night-blindness, dry skin, bones, hair, etc.
• Component of rhodopsin
• Can be synthesized in the body from carotene
• Examples of Minerals
• Calcium, phosphate bones and teeth
• Potassium, sodium body water balance, nerve
  message
• Iron hemoglobin
• Zinc cofactor in digestive enzymes

28
OBESITY

• When calorie intake exceeds energy usage, you
  gain weight
• Eat less OR burn more calories
• Rapid weight loss is self-defeating because
  valuable water and lean muscle lost
• Body fights calorie reduction appetite
  increases metabolic rate slows

29
EATING DISORDERS

• Obsession with weight loss, distorted body image
  anorexia
• Life-threatening treatment involves
  psychological medical help, involvement of
  family friends