BCMB EXAM 4 - Ch 15 The Digestion and Absorption of Food

Carbonic Acid (H2CO3), produced within parietal cells by the enzyme .......... dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-)

carbonic anhydrase

Which three are preteases secreted from the pancreas?

carboxypeptidase trypsin chymotrypsin

List the path taken by undigested material through the large intestine from beginning to end.

cecum ascending colon transverse colon descending colon sigmoid colon rectum

Blood within the hepatic sinusoids drains into the.....which drains into the vena cava.

central vein

Regulation of gastric secretion and motility by the CNS prior to the arrival of food in the stomach, is called the.....phase

cephalic

The entry of chyme containing fatty acids into the duodenum stimulates secretion of ........., which causes contraction of the gallbladder and relaxation of the sphincter of Oddi.

cholecystokinin

match the following diseases with the mechanism by which each causes diarrhea

cholera: toxin-stimulated secretion of Na+ provides osmotic drive behind movement of water into the intestinal lumen. Celiac Sprue: Gluten sensitivity and associated damage to the intestinal mucosa Lactose Intolerance: retention of undigested lactose results in retention of, rather than absorption of, water in the intestinal lumen.

A protein known as ..... is an amphipathic molecule secreted by the pancreas that binds the lipase enzyme and holds it on the surface of lipid droplets.

colipase

The wall of most of the intestinal tract

contains convolutions that increase the surface area of absorption

Cholecystokinin, CCK, secreted in response to fat in chyme, stimulates.....releasing bile that will emulsify the fat

contraction of the gallbladder

In passing from the thoracic cavity to the abdominal cavity, the esophagus passes through a large muscle called the

diaphragm

The process of dissolving and breaking down macromolecules within the GI tract is referred to as

digestion

the primary functions of the digestive system are

digestion and absorption of ingested food

The main forms of carbohydrate digested by brush border enzymes are

disaccharides

which three stimuli initiate gastric phase reflexes of the gastrointestinal tract?

distension, acidity, amino acids and peptide concentration

Gastric Gland Secretion is inhibited

during the intestinal phase of regulation by the presence of acid in the duodenum by the presence of fatty acids in the duodenum when there is distension of the duodenum

The process of dividing a large mass of lipid into a fine suspension of small lipid particles with greater surface area is called

emulsification

Hormones released by duodenal cells that inhibit gastric acid secretion and motility are collectively called

enterogastrones

the pancreatic enzyme tyrpsin is cleaved from an inactive zymogen precursor by the brush border enzyme

enterokinase

In which two regions of the gastrointestinal tract does the LEAST amount of digestion of food particles occur?

esophagus pharynx

During the last half of pregnancy, increased pressure in the abdominal cavity and movement of the lower esophagus into the throacic cavity can result in

gastroesophageal reflux

Billions of bacteria are present in the.....which doesn't cause harm because that space is part of the....

gastrointestinal tract lumen; external environment

What are the four best - understood gastrointestinal tract hormones?

glucose-dependent insullinotropic peptide cholecytokinin gastrin secretin

Compared to the small intestine, the large intestine

has a greater diameter is shorter has a smaller surface area

Compared to when it is empty between meals, a stomach containing a typical meal

has a larger volume but a similar pressure

Before entering the vena cava, blood draining from intestinal capillary beds travels to the liver via the

hepatic portal vein

External or "Extrinsic" control of motility and secretion in the gastrointestinal tract is mediated by

hormones the autonomic nervous system

Enzymes that act on food molecules in the small intestine are located

in secretions that come from the pancreas on the apical membranes of the epithelial cell lining

What 3 steps are missing from the top of this pathway?

increased plasma cholecystokinin increased cholecystokinin secretion increased intestinal fatty acids and amino acids

Distension of the rectum reflexively relaxes the .... anal sphincter; relaxation of the ..... anal sphincter is under voluntary control.

internal external

neural and hormonal control of the gastrointestinal tract occurs in three different phases depending on where the stimulus originates. These phases include the

intestinal, cephalic and gastric phase

Which of the following are not part of the gastrointestinal tract, but are accessory organs that secrete substances into it?

liver salivary glands pancreas

Capillary blood from the intestinal wall containing absorbed nutrients travels first to the........via the.....

liver; hepatic portal vein

Relaxation of the .... permits a bolus to pass from the esophagus into the stomach.

lower esophageal sphincter

Following ingestion of meals, intense contractions of the large intestine known as....occur.

mass movements

Which of these are functions of chewing?

mixing food with saliva to create the subjective pleasure of taste breaking up large pieces of food into smaller particles creating a bolus that can be more easily swallowed

In the process of lipid absorption, ......... enter epithelial cells from the intestinal lumen across the apical membrane, and ........ are released across from the basolateral membrance

monoglycerides and fatty acids; triglycerides

The chemical digestion of complex carbohydrates begins in the...., but most starch digestion occurs in the....

mouth, small intestine

arrange layers of the wall of the gastrointestinal tract from the closest to the lumen to the furthest from the lumen

mucosa, submucosa, muscularis externa, serosa

Which of these are stimuli that initiate the intestinal phase of gastrointestinal regulation?

acidity of contents in the small intestine distension of the small intestine osmolarity in the lumen of the small intestine digestive products in the small intestine.

Collectively, the tubular organs through which food passes during the digestive process are referred to as the

alimentary canal gastrointestinal tract

The region of the stomach closest to the pyloric sphincter is referred to as the

antrum

powerful contractions of the stomach wall that sweep along the stomach force the pyloric sphincter closed, causing a rebound of chyme back toward the stomach that is called

retropulsion

glucose and galactose are absorbed from the lumen of the intestine into intestinal epithelial cells by

secondary active transport

An increase in acidity detected within the duodenum is the principle stimulator of the secretion of the hormone....

secretin

The movement of chemicals and enzymes from exocrine glands into the digestive tract lumen is referred to as..

secretion

Which are functions of the large intestine?

secretion of mucus, HCO3- and K+ Store fecal material prior to defecation concentrate fecal material by absorbing water

Of the four histological layers that make up the wall of the intestinal tract, the one farthest from the lumen is called the

serosa

Swallowing muscles in the upper one-third of the esophagus are composed of....muscle that are innervated by..... motor fibers

skeletal; somatic

Pacemaker cells in the wall of the stomach undergo spontaneous depolarizations and repolarizations. What two terms refer to this electrical mechanism

slow waves basic electrical rhythm

In addition to being the primary organ of nutrient absorption, the majority of ingested and secreted water is absorbed in the:

small intestine

The........is the region of the gastrointestinal tract that connects the stomach to the large intestine.

small intestine

absorption of ingested and secreted water primarily occurs in the

small intestine

The type of muscle present in the lower two-thirds of the esopahgus is ......, and it is innervated by .... motor fibers

smooth autonomic

A decrease in the pH of gastric juices stimulates an increase in the secretion of ....

somatostatin

The digestive organ connecting the esophagus and the small intestine is the

stomach

The main function of the..... is to store, dissolve, and partially digest the macromolecules in food and to regulate the rate at which its contents empty into the small intestine

stomach

Put these structures in the order that chyme passes through them during digestion, with the first at the top

stomach duodenum jejunum ileum large intestine

Distension of the colon activates...nervous that....the ileocecal valve.

sympathetic; contract

Stronger contractions of stomach smooth muscle occur when

the frequency of action potentials generated by slow waves increases

Segmentation contractions occur when the slow wave depolarizations in the smooth muscle cells exceed a ..... value and an action potential is generated.

threshold

Name the process of forcefully ejecting stomach or intestinal contents via the esophagus and mouth.

vomiting

Inactive digestive enzymes are stored in pancreatic acinar cells in inactive forms known as...

zymogens

arrange in order in which they occur during the gastric phase positive feedback loop:

1) partial digestion of proteins 2) G cells stimulated to secrete gastrin 3) Gastrin stimulates secretion of histamine, HCL and pepsinogen 4) further digestion of proteins 5) Additional gastrin secretion

Which is TRUE about the stomach?

It has a volume of about 50ml when empty, but during a meal it relaxes to a volume as large as 1.5 L without an increase in pressure

Approximately how long does it take a peristaltic wave to travel the length of the esophagus after swallowing?

9 seconds

Which three of the following are true regarding the mechanism of secretion of hydrogen ions (H+) by parietal cells of the stomach?

A primary active antiporter exchanges H+ for K+ across the apical membrane. H+ is transported across the apical membrance against a concentration gradient. H+ ions are created within parietal cells by the dissociation of H2CO3 into H+ and HCO3-.

The hormone....is secreted by the small intestine in response to the presence of fatty acids and amino acids, and it stimulates the release of digestive enzymes from cells of the....

CCK pancreas

Pancreatic secretion of bicarbonate and enzymes increases during a meal, mainly as a result of stimulation by the hormones

CCK and Secretin

Arrange the following steps in the order they occur in the pancreas' production and secretion of bicarbonate ions, with the first step at the top.

CO2 and H20 are converted to H2CO3 by carbonic anhydrase H2CO3 dissociates into H+ and HCO3- HCO3- is transported into the lumen in exchange of Cl-

Arrange the following to summarize the production of bicarbonate ions for pancreatic juice

CO2 enters ductule cells from bloodstream Carbonic anhydrase synthesizes H2CO3 from CO2 and H20 H2CO3 dissociates into H+ and HCO3- HCO3- is secreted into pancreatic juice

Which two homrones are main stimulators of pancreatic exocrine secretions?

Cholecystokinin secretin

The solution in the stomach that contains exocrine secretions of gastric glands, fragments of ingested food, salt, and water is called

Chyme

Which of these accurately describe general features of the gastrointestinal tract wall from the stomach to the anus?

Epithelial cells are joined by tight junctions Invaginations of the epithelium form exocrine glands The lumen is lined by a single layer of epithelial cells Most of the luminal surface is highly convoluted, which increases the surface area available for absorption

Which are components of the portal triads found within hepatic lobules?

branches of the portal vein branches of the hepatic artery branches of the bile duct

During the digestion of a meal, the most common form of motiity in the small intestine is a peristaltic wave that begins in the duodenum and sweeps continuously to the end of the ileum.

False

Select the TRUE statements.

Feces eliminated from the digestive tract are composed mainly of bacteria and ingested material that was not absorbed. Elimination of waste products from the internal environment is a minor role of the digestive tract. The kidneys are more responsible for elimination of wastes from the internal environment of the body than the digestive system.

Which statements about the function of the enzyme pepsin are TRUE?

It aids the digestion of collagen contained in the connective tissue of ingested meat. It is not essential for protein digestion, because pancreatic enzymes can completely digest ingested proteins. It is inactivated in the alkaline environment of the small intestine.

match these GI tract neural reflexes to their descriptions

Short Reflexes: begin at GI tract receptors and travel through enteric nervous system to effector cells Long Reflexes: begin at GI tract receptors, return signals to effectors from the CNS by way of autonomic nerve fibers

Arrange in order the events of a local reflex coordinating intestinal motility and secretion

Stretch and food particles occur inside the GI tract lumen Chemoreceptors and mechanoreceptors in the tract wall are activated. Receptor activity stimulates neurons in the myenteric plexus and submuscosal plexus. Smooth muscle and exocrine glands act as effectors.

Put the steps of the swallowing reflex in order, with the first step at the top.

The food bolus is forced into the back of the mouth by the tongue. Sensory receptors send afferent impulses to the swallowing center in the medulla oblongata. The soft palate elevates, respiration is inhibited, and the glottis is closed.. The food bolus forces the epiglottis backward to cover the glottis. The upper esophageal sphincter opens and the food bolus passes into the esophagus.

Put the typical daily volumes of these fluid movements in descending order, with the largest volume at the top.

Total amount of fluid absorbed by the gastrointestinal tract in a day. Amount of fluid secreted by exocrine glands into the gastrointestinal tract in a day. Amount of fluid in foods and liquids ingested in a day.

Metabolic activity of bacteria in the large intestine produces vitamins and short-chain fatty acids that play important roles in immunity and cardiovascular health

True

The overall function of the digestive system is to process ingested food into molecular forms that are then transferred, along with small molecules, ions, and water, to the body's internal environment.

True

The stimuli that increase the rate of acid secretion from the stomach also tend to increase the motility of the stomach

True

which of the following is a feature that greatly increases the surface area of the small intestine for absorption of nutrients?

a highly convoluted epithelial surface

the most important component found in bile that contributes to digestion is

bile salts

In a micelle, the......parts of bile salts orient towards the center of the aggregate whereas the.......groups extend toward the water surface on the periphery.

nonpolar, polar

Movement of water into the lumen of the small intestines from the blood occurs primarily by

osmosis

Which branch of the nervous system increases the release of gastrin and histamine in the stomach?

parasympathetic

Match these gastric gland cell types with the correct secretions

parietal cells - hcl and intrinsic factor cheif cells - pepsinogen ECL - histamine Mucous cells - mucus G Cells - Gastrin D cells - somatostatin

There are three pairs of salivary glands:

parotid, sublingual and submandibular

Secretion of HCL from gastric glands is stimulated without hormonal or neural influence by the presence of ....... in the stomach.

partially digested protein

Pepsin is secreted as an inactive zymogen precursor called

pepsinogen

An increase in the amount of....in the stomach increases H* secretion during the gastric phase

peptides

Moving, wave-like contraction of the smooth muscles of the gastrointestinal tract is known as

peristalsis

Food particles on the way from the mouth to the stomach pass through the

pharynx esophagus

which of the following act as emulsifying agents in the small intestine

phospholipids in food and bile salts secreted in the bile

During ingestion of a meal, the parasympathetic nervous system mediates an increase in the volume of the stomach called ......... which allows it to accommodate ingested food without an increase in internal pressure.

receptive relaxation

Contractions of the....the final segment of the large intestine, expel feces in a process called

rectum; defecation