MG Ch 15
Inside of parietal cells of the gastric pits, the enzyme catalyzes the production of carbonic acid (H2CO3) from carbon dioxide and water
carbonic anhydrase
Regulation of gastric secretion and motility by the CNS prior to the arrival of food in the stomach is called the phase
cephalic
The three phases of gastrointestinal control include the and phases, identified by where a stimulus is perceived
cephalic gastric intestinal
The solution in the stomach that contains exocrine secretions of gastric glands, fragments of ingested food, salt, and water, is called
chyme
When stomach exocrine secretions are mixed with ingested food particles, small molecules, and water, it forms a solution known as
chyme
A main function of the serosa layer of the intestinal wall is
connecting the gut to the abdominal wall and supporting the gastrointestinal tract within the abdominal cavity
The esophagus
connects the pharynx and the stomach
The epithelial cells lining the gastrointestinal tract are completely replaced about once every 5
days
When the acidity of gastric juice increases, gastrin secretion
decreases
As partially digested proteins exit the stomach and their pH buffering capacity is no longer present, the pH of gastric contents and the secretion of HCl and gastrin
decreases; is inhibited
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 consists of neurons that are located within the organs of the digestive tract, and control reflexes associated with digestive secretion and motility
enteric nervous system
The submucous plexus and the myenteric plexus are components of the
enteric nervous system
Some digestive enzymes are secreted from exocrine glands into the lumen of the GI tract, while others are located on the basolateral membranes of the intestinal epithelium.
false
The cephalic phase of gastrointestinal control is defined as that initiated by receptors present upstream of the small intestine, including taste receptors and stomach stretch receptors
false
The origin of hydrogen ions that are pumped across the apical membrane of parietal cells of the stomach is
from carbonic acid, created when carbonic anhydrase catalyzes the reaction of CO2 with H2O
The uppermost part of the body of the stomach is referred to as the
fundus
The phase of digestive regulation that is responsive to the distension and acidity of the stomach as well as the presence of amino acids and peptides, is the phase
gastric
During the last half of pregnancy, increased pressure in the abdominal cavity and movement of the lower esophagus into the thoracic cavity can result in
gastroesophageal reflux
Recurring regurgitation of acid into the esophagus from the stomach accompanied by heartburn and other complications is called disease
gastroesophageal reflux
Collectively, the tubular organs through which food passes during the digestive process are referred to as the
gastrointestinal tract alimentary canal
Billions of bacteria are present in the which doesn't cause harm because that space is part of the
gastrointestinal tract lumen; external environment
Entry of gastric juice into the esophagus causes a painful sensation commonly referred to as
heartburn
Glands that secrete mucus, hydrochloric acid, and the enzyme precursor pepsinogen are found mainly
in the body of the stomach
Gastrin, acetylcholine, and histamine all (increase or decrease?) the secretion of acid by parietal cells
increase
After a bolus has entered the stomach, the esophagus is protected from gastric juice by continued constriction of the
lower esophageal sphincter
Relaxation of the permits a bolus to pass from the esophagus into the stomach
lower esophageal sphincter
Of the four histological layers that make up the wall of the intestinal tract, the one closest to the lumen is called the
mucosa
The innermost layer of the four histological layers making up the wall of the small intestine (facing the lumen) is called the
mucosa
Arrange the layers of the wall of the gastrointestinal tract from the closest to the lumen (top) to furthest from the lumen (bottom)
mucosa submucosa muscularis externa serosa
A non-enzymatic component of saliva that lubricates food particles and helps form them into a bolus for swallowing is called
mucus
The has both circular and longitudinal muscle layers, which can contract to change the circumference and length of the gastrointestinal tract
muscularis externa
The myenteric plexus is located between the two layers of the
muscularis externa
The cells of the enteric nervous system include the plexus, which mainly regulates motility functions, and the plexus, which mainly influences secretory activity
myenteric submucosal
In the digestive system, the general term describing the transport of digestive products across the mucosal layer from the lumen of the tract into the blood or lymph is
absorption
The entry of products of chemical digestion from the lumen of the gastrointestinal tract into blood or lymph is called
absorption
The salivary glands, liver, gallbladder and exocrine pancreas are collectively referred to as the
accessory digestive organs
Partial digestion of starch, a complex dietary carbohydrate, begins in the oral cavity through the action of the salivary enzyme called
amylase
The region of the stomach closest to the pyloric sphincter is referred to as the
antrum
The movement of chemicals and enzymes from exocrine glands into the digestive tract lumen is referred to as
secretion
Swallowing is initiated by
sensory reception of the bolus in the pharynx
The intestinal phase of regulation of the gastrointestinal tract is initiated by stimuli in the
small intestine
The type of muscle present in the lower two-thirds of the esophagus is (skeletal or smooth?), and it is innervated by (somatic or autonomic?) motor fibers
smooth autonomic
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
The histological layer of the gastrointestinal tract wall immediately outside of the mucosa is the
submucosa
External or "extrinsic" control of motility and secretion in the gastrointestinal tract is mediated by
the autonomic nervous system hormones
The lumen of the gastrointestinal tract is part of
the external environment
Stimuli included in cephalic phase control of gastrointestinal function include
the sight of food the smell of food the taste of food
For most ingested substances, the digestive tract will absorb as much of any particular substance that is ingested and thus it does not regulate the total amount of nutrients absorbed or their concentrations in the internal environment
true
The esophageal phase of swallowing begins when the relaxes, permitting entry of the bolus into the esophagus
upper esophageal sphincter
Of the approximately 8 L of fluid entering the gastrointestinal tract by ingestion or secretion each day, approximately what fraction is excreted in the feces?
1%
Arrange in order the events of a local reflex coordinating intestinal motility and secretion. Start with the earliest at the top of the list
1. Stretch and food particles occur inside the GI tract lumen 2. Chemoreceptors and mechanoreceptors in the tract wall are activated 3. Receptor activity stimulates neurons in the myenteric plexus and submuscosal plexus 4. Smooth muscle and exocrine glands act as effectors
Put the typical daily volumes of these fluid movements in descending order, with the largest volume at the top
1. Total amount of fluid absorbed by the gastrointestinal tract in a day 2. Amount of fluid secreted by exocrine glands into the gastrointestinal tract in a day 3. Amount of fluid in foods and liquids ingested in a day
Put the steps of the swallowing reflex in order, with the first step at the top
1. the food bolus is forced into the back of the mouth by the tongue 2. sensory receptors send afferent impulses to the swallowing center in the medulla oblongata 3. The soft palate elevates, repiration is inhibited and the glottis is closed 4. The food bolus forces the epiglottis backward to cover the glottis 5. The upper esophageal sphincter opens and the food bolus passes into the esophagus
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
Which three stimuli initiate gastric phase reflexes of the gastrointestinal tract?
Acidity Amino acids and peptide concentration Distension
Which of these are stimuli that initiate the intestinal phase of gastrointestinal regulation?
Acidity of contents in the small intestine Digestive products in the small intestine Osmolarity in the lumen of the small intestine Distension of the small intestine
Which two of the following, when present in chyme, are mainly responsible for stimulating the secretion of cholecystokinin (CCK) by the small intestine?
Amino acids Free fatty acids
Differentiated cells of the intestinal mucosa are completely replaced every 4-5 days, the result of constant division of epithelial cells located in what region of the wall?
At the base of the villi
Which of these are functions of chewing?
Breaking up large pieces of food into smaller particles Creating a bolus that can be more easily swallowed Mixing food with saliva to create the subjective pleasure of taste
Gastric gland secretion is inhibited in which of the following scenarios?
By the presence of fatty acids in the duodenum By the presence of acid in the duodenum During the intestinal phase of regulation When there is distension of the duodenum
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
What type of cells or tissue make up the serosa of the wall of the gastrointestinal tract?
Connective tissue
Which of these accurately describe general features of the gastrointestinal tract wall from the stomach to the anus?
Invaginations of the epithelium form exocrine glands. Epithelial cells are joined by tight junctions. Most of the luminal surface is highly convoluted, which increases the surface area available for absorption. The lumen is lined by a single layer of epithelial cells.
Which of these are gastric phase stimuli that increase acid secretion in the stomach?
Distension of the stomach Peptides and amino acids in the stomach
In which two regions of the gastrointestinal tract does the least amount of digestion of food particles occur?
Esophagus Pharynx
Which is true about the function of the digestive system?
Even when nutrients are ingested in excess, they are generally completely absorbed and other organs must act to regulate their concentrations.
All neural GI reflexes are initiated by receptors within the gastrointestinal tract
False
Which of these hormones is not predominantly secreted from the small intestine?
Gastrin
What are the four best-understood gastrointestinal tract hormones?
Gastrin Cholecystokinin Secretin Glucose-dependent insulinotropic peptide
Why does pregnancy sometimes result in reflux of gastric chyme through the lower esophageal sphincter?
Increased abdominal mass from the fetus forces the lower esophageal sphincter to move from below the diaphragm to above the diaphragm.
Which of these are stimuli that initiate salivation?
Increased parasympathetic nerve activity Sight of food Stimulation of mechanoreceptors in the mouth Smell of food
Neural and hormonal control of the gastrointestinal tract occurs in three different phases. What are they?
Intestinal phase Gastric phase Cephalic phase
The ATPase pump in the luminal membrane of parietal cells moves into the cells while transporting out of the cells
K+; H+
Which of the following are not part of the gastrointestinal tract, but are accessory organs that secrete substances into it?
Liver Pancreas Salivary glands
Which two are true about the gastric phase of digestive regulation?
Neurons in the stomach mucosa increase the secretion of gastrin and histamine by way of the enteric nervous system. Distension of the stomach and the presence of peptides stimulate parietal cell acid secretion.
Which branch of the nervous system increases the release of gastrin and histamine in the stomach?
Parasympathetic
What term is used to describe the wave-like moving contractions that occur along segments of the gastrointestinal tract?
Peristalsis
Which stimuli initiate local reflexes that regulate intestinal motility and secretion?
Receptors that detect chyme acidity Receptors that detect nutrients such as monosaccharides, fatty acids, and amino acids GI tract wall stretch receptors Receptors that detect chyme osmolarity
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
What is the main efferent signal pathway mediating chewing reflexes?
Somatic nerves
Which of the following does not stimulate the secretion of H+ by parietal cells of the stomach?
Somatostatin
What are the three pairs of salivary glands?
Submandibular gland Parotid gland Sublingual gland
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
T
Which of the following are true statements about the elimination process of digestion?
The kidneys are more responsible for elimination of wastes from the internal environment of the body than the digestive system. 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.
Which is FALSE regarding the function of the esophagus?
The lower esophageal sphincter remains open the entire time that a meal is being consumed, so food can pass easily into the stomach.
Which of these helps prevent the reflux of gastric material into the esophagus during respiratory cycles and abdominal muscle contractions?
The terminal segment of the esophagus is in the abdominal cavity, so increased pressure in that space forces the sphincter closed.
The enteric nervous system contains adrenergic and cholinergic neurons as well as neurons that release other neurotransmitters, such as nitric oxide, several neuropeptides, and ATP
True
Which of the following do NOT need to be digested into smaller forms before the GI tract can absorb them?
Vitamins and minerals
Feces eliminated from the body consist mainly of
bacteria and ingested material that was neither digested nor absorbed
Because the lower esophageal sphincter is located the diaphragm, when the pressure in the abdominal cavity increases the lower esophageal sphincter is
below; prevented from opening
The cells found in gastric glands that secrete HCl and intrinsic factor are called cells
parietal
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
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 and esophagus
Entry of chloride ions (Cl-) into parietal cells from the bloodstream
provides Cl- within the cell for eventual secretion into the stomach lumen occurs by secondary active transport occurs by countertransport exchange with bicarbonate ions (HCO3-)
The "gatekeeper" that regulates the passage of chyme from the stomach to the duodenum is the sphincter
pyloric
