Chapter 9: The Digestive System Flashcards
____________ digestion, as a part of metabolism, involves the oxidation of glucose and fatty acids for energy (must be extracted from our food)
Intracellular
Nutrients are obtained from food and this occurs within the lumen of our ____________ canal, and is known as ____________ digestion.
alimentary; extracellular
this is technically “outside” the body
The alimentary canal runs from the mouth to the anus and is sectioned off by ____________, or circular smooth muscles around the canal that can contract to allow compartmentalization of function.
sphincters
____________ involves the breakdown of food into its constituent organic molecules.
Digestion
Starches/carbs break down into ____________, lipids breakdown into ____________, and proteins into ____________ ____________.
monosaccharides; free fatty acids and glycerol; amino acids
____________ digestion is the physical breakdown of large food particles into smaller food particles, but does not involve breaking chemical bonds. ____________ digestion is the enzymatic cleavage of chemical bonds.
Mechanial; chemical
____________ involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to tissues/cells.
Absorption
The digestive tract begins with the ________ ____________ followed by the ____________, a shared pathway for both food entering the digestive system and air entering the respiratory system.
oral cavity (mouth); pharynx
From the pharynx, food enters the ____________, which transports it to the ____________. From their, food travels to the ____________ ____________ then to the ____________ ____________.
Esophagus; stomach; small intestine; large intestine
Waste products of digestion enter the ____________, where feces are stored until an appropriate time of release.
rectum
The ____________ nervous system is a collection of one hundred million neurons that govern the function of the GI system. These neurons trigger ____________, or rhythmic contractions of the gut tube, in order to move materials through the system.
enteric; peristalsis
The enteric nervous system can function independently of the brain and spinal cord, although it is heavily regulated by the ____________ nervous system.
autonomic
The (sympathetic/parasympathetic?) division is involved in stimulation of digestive activities, e.g. increasing exocrine secretion and promoting peristalsis, and the (sympathetic/parasympathetic?) is involved in inhibition of these activities.
parasympathetic; sympathetic
Several hormones are involved with feeding behavior, including antidiuretic hormone (ADH or vasopressin), aldosterone, glucagon, ghrelin, leptin, and cholecystokinin.
________ and ____________________ trigger the sensation of thirst, encouraging the behavior of fluid consumption.
________________, secreted by the pancreas, and ________, secreted by the stomach and pancreas, stimulate feelings of hunger.
________ and ________________________ do the opposite, stimulating feelings of satiety.
ADH and aldosterone; ghrelin; leptin and cholecystokinin
The salivary glands, like all glands of the digestive tract, are innervated by the ____________ nervous system.
parasympathetic
Saliva contains salivary ____________, also known as ptyalin, and lipase.
amylase
Salivary ____________ hydrolyzes starch into smaller sugars (maltose and dextrins), while ____________ catalyzes the hydrolysis of lipids.
amylase; lipase
Our muscular tongue forms the food into a ____________, which is forced back to the pharynx and swallowed.
bolus
The ____________ is the cavity that leads from the mouth and posterior nasal cavity to the esophagus. It also connects to the larynx.
pharynx
The pharynx can be divided into 3 parts:
1. ____________ (behind the nasal cavity)
2. ____________ (back of mouth)
3. ____________ (above vocal cords)
- nasopharynx
- oropharynx
- laryngopharynx
Food is prevented from entering the larynx during swallowing by the ____________, a cartilaginous structure that folds down to cover the laryngeal inlet. Failure of this can lead to aspiration of food and choking.
Epiglottis
The ____________ is a muscular tube that connects the pharynx to the stomach. The top third is composed of skeletal muscle, bottom third is smooth muscle, and middle third is a mix of both.
esophagus
top is somatic control, bottom is autonomic control
The reversal of peristalsis by exposure to chemicals, infectious agents, physical stimulation in the posterior pharynx, and even cognitive stimulation, can lead to the reversal of perisalsis in the process of ____________ (vomiting).
emesis
Swallowing is initiated in the muscles of the ____________, which consitute the ________ ____________ ____________.
oropharynx; upper esophageal sphincter
As the bolus approaches the stomach, a muscular ring known as the ____________ ____________ ____________ relaxes and opens to allow passage of food.
lower esophageal sphincter (cardiac sphincter)
No mechanical or chemical digestion takes place in the ____________, except for the continued enzymatic activity initated in the mouth by salivary enzymes.
esophagus
The ____________ is a highly muscular organ with a capacity of approx. 2 liters.
stomach
The stomach is located in the ________ ________ quadrant of the abdominal cavity, underneath the ________________. It uses HCl and enzymes to digest food, and must have thick mucosa to prevent autodigestion.
upper left; diaphragm
The stomach is divded into what 4 main divisions? Which 2 contain mostly gastric glands? Which 2 contain mostly pyloric glands?
Fun boys trumpy.
- fundus (gastric)
- body (gastric)
- antrum (pyloric)
- pylorus (pyloric)
The internatl curvature of the stomach is called the ________ curvature, the external curvature is called the ________ curvature.
lesser; greater
The lining of the stomach is thrown into folds called ________.
rugae
The mucosa of the stomach contains gastric glands and pyloric glands. The ________ glands respond to singals from the ________ nerve of the parasympathetic nervous system, which is activated by the brain in response to the sight, taste, and smell of food.
gastric; vagus
What are the 3 different cell types of gastric glands?
MCP
- Mucous cells
- Chief cells
- Pareital cells
Gastric gland cells
________ cells produce the bicarbonate-rich mucus that protects the muscular wall from the harshly acidic and proteolytic environment of the stomach.
Mucous
________ juice is a combination from the other 2 cell types in the gastric glands: chief cells and parietal cells.
Gastric
The ________ cells secrete pepsinogen, which is the inactive, zymogen form of pepsin, a proteolytic enzyme.
zymogen = an inactive substance which is converted into an enzyme when activated by another enzyme.
chief
Hydrogen ions in the stomach, secreted by ________ cells as HCl, cleave pepsinogen to pepsin.
parietal
________ digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments. It is most activat at a low pH.
Pepsin
Which bacteria is resilient to stomach acids and can cause inflammation, ulcers, and gastric cancers?
H pylori
In addition to HCl, parietal cells secrete ____________ ________, a glycoprotein involved in the proper absorption of vitamin B12.
intrinsic factor
The ________ glands contain ____-cells that secrete gastrin, a peptide hormone.
pyloric; G
________ induces the parietal cells to secrete more HCl and signals the stomach to contract, mixing its contents.
Gastrin
The digestion of food in the stomach results in an acidic, semifluid mixture known as ________.
chyme
this allows absorption of nutrients to be maximized in the small intestine
What are the 3 segments of the small intestine?
- duodenum
- jejunum
- ileum
What is the duodenum responsible for?
The majority of chemical digestion and some minor involvement in absorption
Food leaves the stomach through the ________ sphincter and enters the ________.
pyloric; duodenum
The presence of chyme in the duodenum causes the release of ________-________ enzymes like disaccharidases (maltase, isomaltase, lactase, and sucrase.
brush-border
Brush-border enzymes are present on the luminal surface of cells lining the ________; what are they responsible for?
duodenum; breaking down dimers/trimers of biomolecules into absorbable monomers
The duodenum also secretes ________________, which is involved in the activation of other digestive enzymes from accessory organs of digestion, and it secretes secretin and cholecystokinin (CCK)
enteropeptidase
The ________________ digest disaccharides. ________ digests maltose, ________ digests isomaltose, ________ digests lactose, and ________ digests sucrose.
disaccharidases; maltase, isomaltase, lactase, sucrase
Bacteria in the intestines then hydrolyze the disaccharide (after processed by enzyme), producing ________________ as a byproduct. Undigested disaccharides can have an osmotic effect, pulling water into the stool and causing diarrhea.
This is why lactose intolerants have bloating, because they don’t digest lactose.
methane
________________ breakdown proteins.
Peptidases
________________ is a peptidase secreted by glands in the duodenum that removes the N-terminal amino acid from a peptide. ________________ cleave the peptide bonds of dipeptides to release free amino acids.
Aminopeptidase; dipeptidases
Unlike carbs, which must be broken down into monosaccharides for absoroption, proteins can be broken down into ________ and still be absorbed in the small intestine.
di- and tripeptides
________________ is an enzyme critical for the activation of trypsinogen, a pancreatic protease, to trypsin. It also activates procarboxypeptidases A and B to their active forms.
Enteropeptidase
After ________________ is activated into trypsin, it initiates an activation cascade.
trypsinogen
________ is a peptide hormone that causes pancreatic enzymes to be released into the duodenum. It also regulates pH by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from the pancreas.
Secretin
Secretin is also an ________________, a hormone that slows motility through the digestive tract, which allows digestive enzymes to act on chyme, especially fats.
enterogastrone
________________ (CCK) is secreted in response to the entry of chyme (specifically, amino acids and fat in the chyme) into the duodenum.
cholecystokinin
CCK stimulates the release of ________ and ________________ ________ and also acts in the brain, where it promotes satiety.
bile and pancreatic juices
________ is a complex fluid composed of ________ salts, pigments, and cholesterol.
Bile; bile
Bile salts are derived from ________________ and are not enzymes, thus do not directly perform chemical digestion. They do serve an important role in mechanical digestion of fats and facilitate the chemical digestion of lipids. They can have hydrophobic and hydrophilic regions, allowing them to serve as a bridge between aqueous and lipid environments. They are like soap.
cholesterol
Bile salts ________ fats and cholesterol into ________. Without bile, fats would spontaneously separate out of the aqueous mixture in the duodenum and would not be accessible to pancreatic ________, which is water-soluble.
emulsify; micelles; lipase
Micelles increase the surface area of fats, increasing the rate at which lipase acts
Proper fat digestion depends on ________ and ________.
bile; lipase
________ gets the fats into solution and increases their surface area by placing them in micelles (mechanical), then ________ hydrolyzes the ester bonds holding the lipids together (chemical).
Bile; lipase
CCK promotes the secretion of pancreatic juices into the ________. Pancreatic juices are a complex mixture of enzymes in a ________________-rich alkaline solution.
See figure 9.3
duodenum; bicarbonate
See figure 9.3
Bicarbonate in pancreatic juices helps to neutralize acidic ________, as well as provide an ideal working environment for digestive enzymes, which are most active at pH 8.5.
chyme
Pancreatic juices contain enzymes that can digest all 3 types of nutrients, which are?
carbs, fats, proteins
The pancreas performs endocrine functions by releasing ________, ________, and ________, which are peptide hormones that maintain blood sugar levels. This hormonal function is limited to cells residing in islets of ________________ scattered throughout the organ.
But the bulk of the pancreas is made of exocrine cells called ________ cells that produce pancreatic juices.
insulin, glucagon, somatostatin; Langerhans; acinar
Pancreatic ________________ breaks down large polysaccharides into small disaccharides. Pancreatic ________________ (trypsinogen, chymotrpsinogen, and carboxypeptidases A and B) are released in their zymogen form, but once activated, are responsible for protein digestion.
amylases, peptidases
________________, produced by the duodendum, is the master switch: it converts trypsinogen to trypsin, which then activates the other zymogens and also activates procarboxypeptidases A and B.
Enteropeptidase
The pancreas also secretes pancreatic ________, to breakdown fats into free fatty acids and glyceorl.
lipases
Pancreatic juices are transferred to the duodenum via a duct system that runs along the middle of the pancreas. Acinar cells secrete their products into ducts, which empty into the duodenum through the ________ and ________ ________________ ________________.
major and minor duodenal papillae
The ________ is located in the upper right quadrant of the abdomen and contains 2 unique structures for communicating with the digestive system. First, ________ ________ connect the liver with the gall bladder and small intestine. The liver also receives blood draining from the abdominal portion of the digestive tract through the ________ ________ vein.
liver; bile ducts; hepatic portal
The liver produces ________, which travels down bile ducts to be stored in the gallbladder or released in the duodenum
bile
Nutrient-rich blood from the hepatic portal vein can be processed by the liver before draining into the ________________ ________ ________ on the way to the right side of the heart.
inferior vena cava
The liver takes up excess sugar to create ________________, the stored form of glucose, and stores fats as ________________.
glycogen; triacylglycerols
The liver can also produce glucose through ________________ and ________________ and mobilizing fats into ________________.
glycogenolysis, gluconeogenesis; lipoproteins
The liver detoxifies both ________________ compounds (made in body) and ________________ compounds (from environment).
e.g. ammonia from amino acid metabolism is converted into urea to be excreted by kidneys; alcohol and meds
endogenous; exogenous
The major pigment in bile is ________________, which is a byproduct of the breakdown of ________________.
bilirubin; hemoglobin
Bilirubin travels to the liver, where it is ________________ (attached) to a protein and secreted into the bile for excretion.
conjugated
If the liver cannot process/excrete bilirubin (due to liver damage, excessive RBC destruction, or bile duct obstruction), ________________ or skin yellowing can occur.
jaundice
The liver also synthesizes certain proteins necessary for proper body function. This includes ________, a protein that maintains plasma oncotic pressure and serves as a carrier for many drugs/hormones, and ________ ________ used during blood coagulation.
albumin; clotting factors
The ________________ is located just beneath the liver and both stores and concentrates bile. Upon release of ________ from the duodenum, this contracts and pushes bile out into the biliary tree.
gallbladder; CCK
Salivary ________ is released by the salivary glands. What does it hydrolyze?
amylase; starch into maltose and dextrins
Pancreatic amylase is released by the ________ into the ________ what does it hydrolyze?
pancrease (acinar cells), duodenum; hydrolyzes starch to maltrose and dextrins
Maltase is released by intestinal glands into the ________. What does it hydrolyze and into what?
duodenum; maltose to 2 glucose molecules
Isomaltase is released by intestinal glands into the ________. What does it hydrolyze and into what?
duodenum; isomaltose to 2 glucose molecules
Sucrase is released by the intestinal glands into ________. What does it hydrolyze and into what?
duodenum; sucrose into glucose and fructose
Lactase is released by the intestinal glands into ________. What does it hydrolyze and into what?
Lactose; glucose and galactose
Pepsin(ogen) is made by gastric glands (which type of cell?) and works in the ________. What does it hydrolyze and into what? What activates it?
chief; stomach; specific peptide bonds; activated by HCl
Trypsin(ogen) is made by the pancreas (which type of cell?) and works in the ________. What does it hydrolyze and into what?
What does it convert? What activates it?
acinar cell; duodenum; specific peptide bonds
Converts chymotrypsinogen to chymotrypsin; activated by enteropeptidase
Chymotrypsin is made by the pancreas (which type of cell?) and worksi n the ________. What does it hydrolyze and into what? What activates it?
duodenum; specific peptide bonds; trypsin
(Pro)carboxy peptidases A and B are made in the pancreas and work in the ________. What does it hydrolyze? What activates it?
duodenum; terminal peptide bond at carboxy end; enteropeptidase
Aminopeptidase is made in the intestinal glands and works in the ________. What does it hydrolyze?
duodenum; terminal peptide bond at amino end
Dipeptidases are made in the intestinal glands and work in the ________. What does it hydrolyze?
duodenum; pairs of amino acids
Enteropeptidase is made in intestinal glands and works in the ________. What does it convert and into what?
duodenum; converts trypsinogen into trypsin and procarboxypeptidases A and B to carboxypeptidases A and B
Bile is made in the ________ and works in the ________. What does it do?
liver; duodenum; emulsifies fat
Lipase is made by ________ and works in the duodenum. What does it hydrolyze?
pancreas; lipids
What are the 3 segments of the small intestine?
- Duodenum
- Jejenum
- Ileum
The duodenum is primarily involved in ________, and the jejenum and ileum are involved in ________.
digestion; absorption
The small intestine is lined with ________, which are small, finger-like projections from the epithelial lining. Each villus has many ________________ to increase surface area.
villi; microvilli
Each villus has a ____________ ____ in the middle of it for the absorption of water-soluble nutrients, and a ________, a lymphatic channel that takes up fats for transport into the lymphatic system.
capillary bed; lacteal
What happens in the small intestine?
Simple sugars and amino acids are absorbed by secondary active transport and facilitated diffusion into the epithelial cells lining the small intestine.
Once substances pass into the epithelial cell membrane into the intestinal ____________. Blood constantly passes the epithelial cells, carrying the carbs and amino acid molecules away.
capillaries
This creates a concentration gradient such that the blood always has a lower concentration of monosaccharides and amino acids than inside the epithelial cells. Thus, simple carbs and amino acids diffuse from the epithelial cells into the capillaries. The absorbed molecules then go to the liver via the hepatic portal circulation.
Short-chain fatty acids also diffuse directly into the intestinal ________. They do not require transporters because they are nonpolar.
capillaries
Larger fats, glycerol, and cholesterol move separately into the intestinal cells but then reform into ________________.
triglycerides
The triglycerides and esterified cholesterol molecules are packaged into ________________.
chylomicrons
Rather than entering the bloodstream, chylomicrons enter the lymphatic circulation through ________, small vessels that form the beginning of the lymphatic system.
lacteals
Lacteals converge and enter the venous circulation at the ________ duct in the base of the neck, which empties into the left subclavian vein.
thoracic
Failure to digest and absorb fat properly can lead to deficiencies of ______-__________ vitamins.
fat-soluble
The ________-________ vitamins are taken up, along with water, amino acids, and carbohydrates, across the endothelial cells of the small intestine , passing directly into the plasma.
water-soluble
The small intestine absorbs ________ in addition to fats, carbs, amino acids, and vitamins. As solutes are absorbed into the bloodstream, it is drawn with them, eventually reaching the capillaries.
water
The large intestine is the final part of the GI tract and is primarily involved in what?
Water absorption
What are the 3 major sections of the large intestine?
- Cecum
- Colon
- Rectum
The ________ is simply an outpocketing that accepts fluid exiting the small intestine through the ________________ ________. The ________________ is attached.
cecum; ileocecal valve; appendix
The appendix is a small finger-like that is believed to be ________________, but it may actually have a role in warding off certain bacterial infections and repopulating the colon with normal flora after diarrhea.
vestigial
What are the 4 parts of the colon?
- ascending
- transverse
- descending
- sigmoid
The small intestine actually absorbs much more water than the colon, so it primarily does what?
Concentrates the remaining material to form feces
The ________ serves as a storage site forfeces. The ________ is the opening through which wastes are eliminated and consists of what 2 sphincters?
rectum; anus; internal and external anal sphincters
The external sphincter is under ________ control (somatic), but the internal sphincter is under ________ control (autonomic).
voluntary; involuntary
