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