Digestive System Flashcards
Gastric Secretions will stop due to?
Food in duodenum, causes stretching effect, causes hormones to be released, to slow down gastric secretions
- no protein present-HCL’s purpose it’s to convert pepsinogen to pepsin.
- duodenal feedback
- somatostatin release - released by duodenal cells, slow gastric secretion
Phases that control Gastric Secretions
- Cephalic - Thinking about food, causes stomach to release gastrin. Hormone that produces HCL & mucous. Prepares body for food arriving in the body - stomach grumbling. Increase secretions
- Gastric - release of gastrin, gastrin increases HCL. Stretching of stomach. Continues breakdown of proteins. Increase secretions
- Intestinal-duodenal feedback - slow gastric phase (secretions). Stretching effect sends message back to stomach to slow down release of chyme. Gives duodenum time to do its job. Decrease secretions
Factors that effect duodenal activity
- Presence of fat in chyme-bile from liver or gb & lipase (pancreatic/exocrine juice) breakdown & emulsifies fats. The amount of fat affects the amount of time is needed to get through the duodenum
- Hypertonicity of chyme-amount of solutes. Chyme is more viscous than than H2O. Need time to break down large proteins, carbs, & lipids
- Acidity of chyme-time is needed to neutralize acidity. The more acidic, the slower the process.
- Distention of the duodenum-stretching effect, releases hormones & slows down gastric emptying
Duodenal hormones
Effect digestion
Slow gastric secretion; speeds up release of bile & pancreatic juice, Na+ bicarbonate
- Secretin
- Somatostatin
- Cholecystokinin (CCK)
Absorption features
Of
Small Intestine
All 3 are only found in the small intestines-because absorption primarily happens in the small intestines
Main function - increase surface area for digestion & absorption
- Micro villi - cytoplasmic extensions of the cell - columnar cell, extends upward
- Villi - folds in mucosa similar to rugae in stomach
- Circular folds - folds in submucosa
Absorption of
Carbs & amino acids
In small intestines
- Active transport- Na+/K pump
- cell to blood capillaries
- Secondary active transport - glucose (carbs) & amino acids co-transport with Na+
- intestine to cell
- Diffusion-glucose & amino acids
- cell to blood capillaries
Absorption of
Lipids
In small intestine
-Triglycerides broken down by lypase to glycerol & fatty acids.
-bile is released from liver or gall bladder
-bile salts surround the fat molecule, which are called miceles
When bile salt surround fat molecule, it becomes water soluable.
-by diffusion glycerol & fatty acids move into the cell
Bile salts stay in the small intestine & can be re-used
- glycerol & fatty acids reform to become triglycerides again
- cell creates a protein coating around triglyceride. This structure is called chylomicron. This make it water soluble
- blood identifies chylomicron as protein, not fat surrounded by protein.
- chylomicron moves into lymphatic system, then into blood circulatory system
Fructose (carb)
Absorption in
Small intestine
By simple diffusion -uniport-a carrier protein helps fructose to move into the cell
Functions
Of the
Digestive System
- Ingestion - process of physically putting food in the body. Carbs, lipids, proteins.
- Digestion - start breakdown foods into smaller components.
Mechanical-chewing & grinding (muscle contractions)
Chemical-HCL (hydrochloric acid) & mostly enzymes - Secretion - mucous & hormones. HCL & enzymes. Helps overall process
- Movement - smooth muscle contractions. Parastalisis-alternating waves of muscle contractions
- Absorption - carbs & amino acids absorbed directly into the bloodstream.
Fats (lipids) absorbed into lymphatic system, then into the blood stream (circulatory system) - Excretion - deification reflex. Bowel movement. We don’t absorb everything we eat
Names & description
Of
Digestive System
One long tube in the body
Holding tank, tube, canal
- digestive tract
- gastrointestinal tract
- alimentary canal
Food does not become a part of us unless we physically absorb the nutrients in the lymphatic system or blood
Layers
Of the
Digestive Tract
4 Layers are the foundation, but may change based on where it is in the digestive tract.
- Mucosa - epithelium (inner lining)
- Submucosa - blood vessels, lymphatic vessels, glands, nerves
*absorption happens here - Muscularis Externa - smooth muscle
Creates peristalsis - movement of fluid thru the digestive tract- inner muscle layer (circular)-changes diameter
- outer muscular layer (longitudinal)
- Serosa - connective tissue that holds other 3 layers together
Features of the
Oral Cavity
Teeth & tongue-mechanical digestion
3 salivary glands in submucosa-chemical digestion
Saliva: H2O, mucous (moistens & protects),
Salivary amylase (starts digestion of carbs pH6),
Antibacterial enzymes
Stratified squamous epithelium - multiple layers for more protection
Features of the
Esophagus
10 inches in length
Stratified squamous epithelium
Pathway to stomach
Does NOT release anything
- muscularis Externa
- top 3rd - skeletal muscle
- middle 3rd - skeletal & smooth muscle
- bottom 3rd - smooth muscle
Swallowing we control skeletal muscle
Features of the
Stomach
PH2
Simple columnar epithelium-we replace stomach lining every 20 days. Goes thru mitosis because acid in stomach will eat the cells up.
Rugae-folds in the mucosa. Function-expansion & surface area
* Muscularis Externa-3 smooth muscle layers. Churns & grinds food. Only place in the body that has 3 muscle areas
Proteins begin to digest in the stomach
Cells
Of the
Stomach
- Mucous cells - secrete mucous; protects cells from acid environment & helps protect intestinal lining
- Chief cells - secrete pepsinogen (inactive enzyme), which interacts with HCL->pepsin (active enzyme that breakdown peptide bonds)
- Parietal cells - secrete HCL, which produces acidity
- Entero endocrine cells - release hormones.
Thinking about food causes gastrin to be released. Gastrin increases stomach activity
What is chyme?
Liquid formed in stomach that moves into the small intestines.
Contents: H2O, churned food, enzymes
Features of the
Small Intestines
21 ft. Long
Simple columnar epithelium
3 sections:
Duodenum-digestion thru enzyme action (1 ft)
Jejunum-digestion & begins absorption (8 ft)
Ileum-absorption (12 ft)
Accessory Organs
Of the
Digestive tract
- Liver - produces bilirubin. Bilirubin converts to bile salts. Bile makes fats water soluble (emulsifies)
- Gall bladder - stores bile salts
- Pancreas - very important for homeostasis in the body
a. Exocrine portion-whatever it secretes goes thru a duct or tube system
-enzymes: pH6.
Amylase-breakdown carbs
Protease-breakdown protein
Lypase-breakdown lipids
-sodium bicarbonate - neutralize the acidic chyme (pH2). Raise to pH6, so enzymes can work
b. endocrine portion (islet cells)
- release hormones
- beta cells: release insulin (lower blood sugar)
- alpha cells: release glucagon (raise blood sugar)
Define diabetes mellitus
Type 1 - little or no insulin. Aka: juvenile diabetes
Type 2 - insulin is not working
- Insulin picks up sugar, the dump sugar into diff cells of he body (fat cells, liver cells, muscle cells).
- Sugar reacts with with receptors on the cells.
- Receptor sites are clogged or shut down, so sugar doesn’t have contact with receptor sites
- Body releases more insulin to try to rectify the problem
Solution to
Diabetes Mellitus
Diet & Exercise
Body brings in less food (sugars), then can use stored glucose & fat cells for energy. The fat cells stop releasing enzymes that block receptor sites
Define insulin dependent diabetes
Initially Type 2, used up all insulin. So it turned into Type 1
Functions of the
Large intestines
Compaction of un digested food
Absorption of H2O (minerals, vitamins, & amino acids)
Has E. Coli present, keeps bad bacteria out. Also helps breakdown proteins, which release amino acids, & cause gas
Where do compaction problems primarily occur?
Sigmoid colon
Define diverticulitis
Intestinal wall has gotten weak, so it bulges out. Fecal matter gets stuck in there & becomes infected or inflamed, it could rupture.
Solution: can give bacteria to shrink & heal or colon re-section
Insoluable fiber creates framework (creates skeletal system) for fecal material, which will create less strain on intestinal wall.
If intestines go into shock, it shuts down.
Action of Secretin
Intestinal hormone that stimulates the release of bicarbonate & pepsin
Inhibits gastric acid
Action of
Cholecystokinin CCK
Intestinal hormone that regulates digestive function & may play a role in appetite
Action of
Somatostatin
Hypothalamic hormone that inhibits growth hormone release & gastric paracrine that inhibits gastrin secretion
Action of
Gastrin
Secreted by stomach that stimulates gastric secretion
