Gastrointestinal System Flashcards by Kenneth Padilla

What is the purpose of the gastrointestinal system?

Converts food into nutrients the body can use

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What processes convert food into nutrients?

Digestion and absorption

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Explain the process of digestion

Is the chemical and mechanical breakdown of foods into smaller compounds that can be utilized by the body

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Explain the how food is generally absorbed after digestion

The nutrients are moved from the intestines (where absorption occurs) into the bloodstream

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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

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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

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Is food mechanically or chemically digested in the mouth?

Both!
Mechanical=chewing
Chemical: salivary glands releasing digestive enzymes

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What is a bolus?

The chewed up food within the mouth

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Explain peristalsis

A wavelike contraction of smooth muscle that moves digested material along the digestive tract

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What occurs in the stomach?

The hollow organ below the esophagus where mechanical and chemical digestion occur

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What structure separates the esophagus and the stomach?

Esophageal sphincter

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What structure separates the stomach and the small intestine?

Pyloric sphincter

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What is the typical pH of the stomach?

1-2

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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)

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Once the bolus has been mechanically and chemically digested in the stomach, what does it become?

Chyme

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Where does absorption start?

Small intestine

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What are the 3 parts of the small intestine?

duodenum, jejenum, ileum

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Which structures aid in absorption by releasing digestive secretions in the duodenum?

Liver and gallbladder

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What does the liver and gallbladder release in the duodenum?

Bile

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Where is Bile created and stored?

Created in the liver
Stored in the gallbladder

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How does bile get secreted into the duodenum?

Though the common bile duct

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What macromolecules are digested in the duodenum?

Carbohydrates, protein, fats

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The small intestine is lined with what structure to aid in absorption?

Villi/microvilli

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What are functions of villi/microvilli?

Finger like folds in the lining of the intestine that increase surface area to aid absorption

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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