Digestive system Flashcards
Four layers of the digestive tubes
Mucosa: Inner layer, epithelial cells Submucosal: layer of connective tissue Muscularis: Smooth muscle with two sublayers Longitudinal and circular Serosa: Outer layer, thin membrane
Sphincters
- sphincter muscles relax opening the passageway
- Sphincter muscles contract closing the passagway
Ingestion
intake of food via the mouth
Digestion
mechanically or chemically breaking down food into their subunits
Movement
food must be moved along the GI tract in order to fulfill all functions; mixing
Absorption
movement of nutrients across the GI tract wall to be delivered to cell via the blood (From lumen to cardiovascular system. Enter blood stream. )
Elimination
removal of indigestible molecules; defecation
Chewing and Swallowing
- Food processing begins the moment food enters your mouth (mechanical and chemical digestion)
- mechanical digestion increases surface area
- Enzymes begin chemical digestion of starches
Teeth
- Twenty primary teeth; thirty-two adult teeth
- Tooth structure: enamel, dentin, and pulp
- Shape of a tooth fits its function
- Incisors (chisel-shaped); bite off chunks of food
- Canines (cone-shaped); tear food
- Premolars and molars (broad crowns and rounded cusps); grind food
Three salivary glands
Parotid
Submandibular glands
Sublingual glands
Saliva
Mostly water
Bicarbonate buffer: used maintain the pH of our saliva. (when you eat something acidic, it will try to neutralize it)
Mucons: protection and lubrication
Salivary amylase: begins starch digestion
Formation of a bolus
Food lubricated in mouth
Role of hard palate and tongue
Pharynx connects with
Trachea
Esophagus
Steps of swallowing
- Muscular contractions push bolus to the pharynx:(Pharyngeal involuntary stage)
- Epiglottis closes larynx
- Uvula covers nasal cavity opening
- Breathing stops momentarily
- Bolus moves down esophagus into stomach (Esophageal involuntary stage)
Peristalsis
- moves bolus down to stomach
- Lower esophageal sphincter (LES) opens
The Stomach
- Muscular (three sublayers), stretchable sac
- Mixes and stores ingested food
- Secretions
- Forms chyme
- Food passes to the small intestine through the pyloric -
sphincter due to peristalsis - Empty stomach has folds called rugae
Gastric juice
- Water
- Parietal cells – HCl and intrinsic factor (Vitamin B12 absorption)
- Mucus: lubricant and protectant
- Chief Cells - Pepsinogen → pepsin; begins protein digestion
- Hydrogen steals bond, to satisfy need of the acid
- One of the strongest acids
- Digestion is not over in the stomach
- Thick layer of mucous that protected lining of stomach from the acid.Breaks down all molecules. If it thins out, you can get an ulcer (digests your own stomach) Can lead to hole in stomach.
- Chief cells: pepsinogen is inactive, the active form is -
- pepsin: breaks down peptide bonds (amino acids [proteins]) pH-2 (can only work in stomach)
- Helicobacter pylori:can cause cancer: Thin mucous, stomach gets eaten away.
Helicobacter pylori
- Produce toxins
- Stomach inflammation; may lead to ulcers
- 80% cured with antibiotics
Three regions of the small intestine
- The duodenum – next to stomach
- The jejunum
- The ileum – next to large intestine
Villi
- Millions
- Contain blood vessels and a lymph vessel
Micro villi
- Projection on the villi
- increase surface area even more Increases absorption efficiency.
Pancreas
- gland cells behind and below the stomach
- Exocrine gland cells: release digestive enzymes for breakdown of complex carbohydrates, proteins, lipids, and nucleic acids
- Endocrine gland cells: produce hormones
Bicarbonate; neutralizes chyme - pancreas has endocrine (inside) and exocrine (outside) functions.
Endocrine (insulin)
Exocrine (enzymes that aid in digestion), (bicarbonate - neutralizes acids) - need it because it just came out of highly acidic stomach.
Gallbladder
- Sausage-shaped, green-colored sac tucked under the liver
- Stores excess bile produced by the liver
- Bile Released into the upper small intestine
- Helps in fat digestion and absorption
- storage center
- store excess bile (produced in the liver)
- Bile released in to small intestine - fat digestion)
Liver
- Manufactures bile: composed of bile salts
- Secretes cholesterol into bile; too much cholesterol can lead to gallstones
- Hepatic portal vein
- Comes from the small intestine filled with nutrients
- Converts and stores excess glucose as glycogen
- Manufactures blood plasma proteins
- Inactivates many hormones
- Removes toxins
- Converts ammonia to urea, which is excreted in urine
Bile
filters blood from what we just absorbed
- excess glucose (store it as glycogen)
Segmentation
- Enhances back and forth mixing
- Increases surface area
Protein digestion
Stomach - Pepsin Small intestine - Peptidases - Trypsin and chymotrypsin from pancreas - Begins in the stomach (pepsin) then goes to small intestines (peptidases, trypsin, chymotrypsin)
Fat digestion
- Small intestine
- Triglycerides emulsified by bile
- Lipase - brake down into monoglycerides and fatty acids
- starts in stomach with hydrocloric acids, mostly broken down my bile (increases the surface area) creates lipase (breaks down lipids)
Enzymes
- functional proteins; work best under a set of optimal conditions
- pH, temperature, substrate, and product levels
Specific for a particular substrate and catalyze a reaction
Names are usually built from name of substrate, followed by “-ase”
Simple Sugar, Amino Acid, and Fat absorption
- Glucose and amino acids absorbed directly into blood vessels
- Monoglycerides and fatty acids form micelles
- Reform into triglycerides
- Enter the lacteals in the villi (Lymph System)
- Enter the bloodstream
The Large Intestine
- Function: Water reabsorption, ion uptake, and feces formation
- Cecum merges with the colon; U-shaped
- Appendix: no known digestive function
- Rectum
- Anal canal and anus; terminal opening of GI tract
- Role of microorganisms in the large intestine
- Example, E. coli - Fecal contamination of water and food supply
- Measure amounts of “coliform bacteria”
How Control Systems Regulate Digestion
- Nerves and hormones regulate food digestion
- Antagonistic hormones in the stomach
- Gastrin causes release of HCl
- Somatostatin shuts down production of HCl
Cholecystokinin
triggers pancreatic enzymes and bile release
Secretin
slows contractions and causes release of bicarbonate from the pancreas
Glucose insulinotropic peptide
triggers release of insulin from the pancreas
Gastroesophageal reflux disease
- “Heartburn”
- Acidic chyme backs up into the esophagus
- Irritation and burning
- Use of antacids
- Limit intake of acidic foods
Constipation
- Hard to eliminate feces
- Too hard; too much water reabsorbed
- Stays in colon too long
- May cause hemorrhoids
- Enlarged and inflamed blood vessels of the anus
- May be due to lack of fiber in diet
Irritable bowel syndrome
“spastic colon” common
Colon cancer
- Number two cancer diagnosis in the United States
- Early warning signs
- Depressed area of abnormal cells
- Polyps
- Causes: Genetics, High-fat, low-fiber diet
Lactose intolerance
- Deficiency of lactase
Crohn’s disease
- Inflammation of the intestinal lining
Gingivitis
- Inflammation of the gums; periodontal disease
- Preventative measures
Pseudomonas and Salmonella
- “Food poisoning”
