Nutr. 202: Module 3

Digestion and Absorption

GI tract

gastrointestinal tract/alimentary canal

GI tract consists of:

organs, outer layer of muscles, primary/secondary organs, inner layer of glands, absorptive cells

primary organs

mouth, esophagus, stomach, small intestine, large intestine, rectum

secondary organs

salivary glands, liver, pancreas, gallbladder

digestive proceses

mechanical and chemical

Food components that do not require digestion to be absorbed

water, minerals/vitamins, small molecules

What are the five main sphincters?

upper esophageal, lower esophageal, pyloric, illeocecal valve, anal sphincters

What are two complications with improper function of sphincters?

Heartburn, vomiting?

What are the five main tastes?

sweet, sour, salty, bitter, umami

What percent of flavor perception is smell?

80%

Where does chemical digestion start?

Salivary amylase, lipase is released, saliva added to lubricate blogs

What is the volume capacity of the stomach?

1-4liters

What are the main gastric juices?

hydrochloric acid, intrinsic factor, mucus, pepsin, gastrin

HCl

\-secreted by parietal cells

\-denatures proteins

intrinsic factor

required to absorb B12

mucus

\-secreted by goblet cells

\-protects stomach from acid

gastin

control HCl

gastric rug

longitudinal folds, started layers to help digestion and protection

How much chyme is secreted through the pyloric sphincter at a time?

3ml

What are the three sections of the small intestine?

Duodenum, jejunum, ileum

Duodenum

neutralizes chyme

jejunum

where most digestion and absorption (of most macronutrients)occurs

ileum

absorption (of fats/lipids)

How does absorption occur in the small intestine?

Assisted by plicae, with villi (lacteals) and microvilli and intestinal crypts

pancreas

secretes alkaline bicarbonate to neutralize chyme

liver

emulsifies fats with bile

gallbladder

stores bile

Absorption of water soluble nutrients

absorbed through intestinal wall, carried by capillaries to liver

absorption of fat-soluble nutrients

absorbed by lacteals that travel through lymph system and enters blood stream through subclavian vein at thoracic duct

How long does food remain in the stomach?

6-8hrs

How long does food remain in the large intestine?

12-24hrs

What is the main function of the large intestine?

propulsion, absorption of water/sodium, waste prepped for poo.

What’s left after the small intestine?

water, plant fibers, bacteria, other

CARB digestion

\-broken down in mouth by salivary amylase

\-digested in stomach

\-broken down in small intestine by pancreatic amylase

\-enters blood as glucose

FAT digestion

\-droplets enter small intestine after eating

\-bile emulsifies fats, lipase breaks into short chain fatty acids

\-longer chain acids made into chylomicrons

\-enter lymphatic system through lacteals

PROTEIN digestion

\-denatured by HCl in stomach

\-broken into smaller units→a.a. in small intestine

\-travels through blood to liver

Vitamin digestion

\-no digestion needed

alcohol digestion

\-some absorbed in stomach and small intestine

\-transferred to liver for detoxification

mineral absorption

\-absorbed all along small intestine and based on body’s need

water digestion

\-most absorbed in small intestine, some in l.i.

\-follows sodium in small intestine

ulcer/peptic ulcer

erosions that occur in lining of stomach/upper small intestine

Cause of ulcer

helioacter pylori

constipation

caused by low fiber (less than 30g) and low exercise.

Causes: hard to poo

diarrhea

\-caused by bacterial/viral infection

\-causes: watery poo

heartburn/reflux

\-caused by: obesity, hernias, pregnancy, sphincter issues

\-causes: pain in chest when acid refluxes into eosphagus

lactose intolerance

\-cause: genetic inability to break down lactose (no lactase)

irritable bowel syndrome

\-cause: overly sensitive muslces/nerves overreact

\-causes: cramping, diarrhea, constipation

ulcerative colitis

\-cause: hereditary, overreactive immune system

\-causes: chronically inflames large intestine

healthy food trends

probiotics, prebiotics, synbiotics

prebiotics

non-digestible carb sources use to support metabolism in large intestine

synbiotics

pre+pro