Gastrointestinal System Flashcards
What is the purpose of the gastrointestinal system?
Converts food into nutrients the body can use
What processes convert food into nutrients?
Digestion and absorption
Explain the process of digestion
Is the chemical and mechanical breakdown of foods into smaller compounds that can be utilized by the body
Explain the how food is generally absorbed after digestion
The nutrients are moved from the intestines (where absorption occurs) into the bloodstream
What is the alimentary canal?
The pathway in the body though which food travels while being digested and absorbed
-as well as the accessory organs that release secretions necessary for digestion to occur
Pathway of food from mouth to being expelled
Mouth > pharynx > esophagus > esophageal sphincter > stomach > pyloric sphincter > small intestine (duodenum, jejenum, ileum) > cecum > large intestine (ascending, transverse, depending) > rectum > anus
Is food mechanically or chemically digested in the mouth?
Both!
Mechanical=chewing
Chemical: salivary glands releasing digestive enzymes
What is a bolus?
The chewed up food within the mouth
Explain peristalsis
A wavelike contraction of smooth muscle that moves digested material along the digestive tract
What occurs in the stomach?
The hollow organ below the esophagus where mechanical and chemical digestion occur
What structure separates the esophagus and the stomach?
Esophageal sphincter
What structure separates the stomach and the small intestine?
Pyloric sphincter
What is the typical pH of the stomach?
1-2
What causes the environment of the stomach to be so acidic?
The acidity is maintained by the gastric juices (HCl, enzymes that begin the chemical digestion of protein)
Once the bolus has been mechanically and chemically digested in the stomach, what does it become?
Chyme
Where does absorption start?
Small intestine
What are the 3 parts of the small intestine?
duodenum, jejenum, ileum
Which structures aid in absorption by releasing digestive secretions in the duodenum?
Liver and gallbladder
What does the liver and gallbladder release in the duodenum?
Bile
Where is Bile created and stored?
Created in the liver
Stored in the gallbladder
How does bile get secreted into the duodenum?
Though the common bile duct
What macromolecules are digested in the duodenum?
Carbohydrates, protein, fats
The small intestine is lined with what structure to aid in absorption?
Villi/microvilli
What are functions of villi/microvilli?
Finger like folds in the lining of the intestine that increase surface area to aid absorption
Which part of the small intestine does most of absorption occurs?
Jejenum (90%)
What is absorbed in the ileum?
Vitamin B12, bile salts, acids
What is the structure that begins the large intestine?
Cecum
The large intestine is also called?
Colon
Where is the remaining waste stored for excretion?
Rectum
What is the anal sphincter?
A ring shaped muscle that tightens to control the excretion of solid waste from the digestive tract
What are the 2 types of digestion?
Mechanical and chemical
Explain the different ways food goes through mechanical digestion
The physical breakdown of food into smaller pieces
-chewing, churning process of the stomach, muscular action of peristalsis, creating greater surface for chemical digestion to take place
Explain chemical digestion
Involves enzymes or acids that break down food at the molecular level
What organs/structures secrete digestive enzymes that take part of chemical digestion?
Liver, pancreas, salivary glands, specialized cells in the lining of the stomach and intestines
What is a zygomen?
An inactive substance that is converted into an active enzyme in the presence of a third substance
Origin and function of Saliva
Origin: salivary glands (mouth)
Function: lubricates mouth, contains salivary amylase that breaks down carbs and starch’s, contains salivary lipase which breaks down fats
Origin and function of Hydrochloric Acid (HCl)
Origin: parietal cells (stomach)
Function:sterilizes harmful bacteria; causes protein to denature; converts pepsinogen into pepsin
Origin and function of Pepsin (ogen)
Origin: Chief cells stomach)
Function: digests protein by breaking bonds of amino acids
Origin and Function of gastric lipase
Origin: chief cells (stomach)
Function: digests lipids and fats in the stomach
Origin and function of mucus
Origin: goblet cells (stomach)
Function:maintains mucosal lining of the stomach; protects the stomach walls from the digestive activity of HCl and other gastric enzymes
Origin and function of Bile
Origin: liver
Function: helps neutralize the acidic chyme as it enters the small intestine; aids in fat digestion and absorption by emulsifying lipid particles
Origin and function of pancreatic bicarbonate
Origin: pancreas
Function: neutralizes chyme as it enters the duodenum
Origin and function of pancreatic lipase
Origin: pancreas
Function: digests lipids and fats in the small intestine
Origin and function of trypsin (ogen) (Proteases)
Origin: pancreas, small intestine
Function:digests proteins in the small intestine
Origin and function of brush border enzymes
Origin: microvilli (small intestine)
Function: includes lactase and other dissacharides that break down lactose and other simple sugars; nucleases that break down nucleic acids; peptidase that complete protein digestion and concert trypsinogen to trypsin
What causes Gastrin to be released and where is it released from? (Target?)
Arrival of protein in the stomach
Released in the stomach
Target: parietal cells of the stomach
What is the function of the hormone Gastrin?
Stimulates gastric acid and mucosal secretion
Increases motility
When protein arrives to the stomach, what hormone is released for gastric acid secretion?
Gastrin
What stimulates the release of Ghrelin and where is it released from? (Target?)
An empty stomach
Released from the stomach
Target: Hypothalamus
What is the function of ghrelin?
Induces hunger
When you are hungry (empty stomach), what hormone is released?
Ghrelin
What stimulates the releases of leptin and where is it released from? (Target?)
Fat in the bloodstream
Released from adipose tissue
Target: hypothalamus
What is the function of leptin?
Reduces hunger by signaling satiety
What stimulates the releases of secretin and where is it released from? (Target)
Arrival of chyme in the duodenum
Released from the small intestine
Target: pancreas, stomach, liver
What is the function of secretin?
Stimulates pancreas to release bicarbonate
Inhibits gastric emptying
Inhibits bile secretion
What stimulates the release of insulin and where is it released from?(target?)
Increase in blood glucose levels
Released from the pancreas
Target: liver, muscle, adipose tissue
What is the function of insulin?
Stimulates uptake of glucose for conversion into glycogen
Decrease blood glucose levels
What stimulates the release of glucagon and where is it released from? (Target?)
Low blood glucose levels
Released from the pancreas (alpha cells)
Target: liver
What is the function of glucagon?
Initiates the breakdown of glycogen
Increase blood glucose levels
What stimulates the release of somatostatin and where is it released from? (Target)
Acid in the stomach
Released from the pancreas’
Target:secretory stomach cells
What is the function of somatostatin?
Inhibits gastric secretion and slows digestion
What stimulates the release of cholecystokinin and where is it released from? (Target?)
Fats and amino acids
Released from: small intestine
Target: gallbladder, pancreas, stomach
What is the function of cholecystokinin (CCK)?
Stimulate gallbladder to release bile
Stimulates the pancreas to release pancreatic enzymes
Inhibits gastric emptying and acid secretion
