Chapter 9: The Digestive System Flashcards
_______________, as a part of metabolism, involves the oxidation of glucose and fatty acids for energy.
Intracellular digestion
The process by which the nutrients are obtained from food occurs within the lumen of the alimentary canal and is known as _________________.
Extracellular digestion
The alimentary canal runs from the ___________ to the ___________ and is sectioned off by sphincters.
- Mouth
- Anus
____________ are the circular smooth muscles around the alimentary canal that can contract to allow compartmentalization of function.
Sphincters
____________ involves the breakdown of food into its constituent organic molecules: starches and other carbohydrates into monosaccharides, lipids (fats) into free fatty acids and glycerol, and proteins into amino acids.
Digestion
_____________ digestion is the physical breakdown of large food particles into smaller food particles, but does not involve breaking chemical bonds.
Mechanical digestion
_____________ digestion is the enzymatic cleavage of chemical bonds, such as peptide bonds of proteins or the glycosidic bonds of starches.
Chemical digestion
_____________ involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body’s tissues and cells.
Absorption
The digestive tract begins with:
- Oral cavity (mouth)
- _____________
- Esophagus
- Stomach
- _____________
- _____________
- _____________
- Oral cavity (mouth)
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
The ___________________ is a collection of one hundred million neurons that govern the function of the gastrointestinal system.
Enteric nervous system
______________ is the rhythmic contractions of the gut tube to move materials through the system.
Peristalsis
The enteric nervous system can function independently of the brain and spinal cord, although it is heavily regulated by the ______________ nervous system.
Autonomic nervous system
The _____________ nervous system is involved in stimulation of digestive activities, increasing secretions from exocrine glands and promoting peristalsis.
Parasympathetic nervous system
The ______________ nervous system is involved in the inhibition of stimulation of digestive activities, increasing secretions from exocrine glands and promoting peristalsis.
Sympathetic nervous system
The fact that so often we feel sleepy and lethargic after eating a big meal (often called a food coma colloquially) is due, in part, to _______________ nervous system.
Parasympathetic nervous system
All of the glands of the body (except sweat glands) are innervated by the _______________ nervous system.
Parasympathetic nervous system
________________ (_______, or ____________) and _______________ trigger the sensation of thirst, encouraging the behaviour of fluid consumption.
- Antidiuretic hormone (ADH, or vasopressin)
- Aldosterone
_____________, secreted by the pancreas to stimulate the feelings of hunger.
Glucagon
______________, secreted by the stomach and pancreas to stimulate the feelings of hunger.
Ghrelin
___________ and ____________ do the opposite of glucagon and ghrelin, stimulating feelings of satiety.
- Leptin
- Cholecystokinin
_____________ digestion in the mouth (oral cavity) involves the breaking up of large food particles into smaller particles using the teeth, tongue, and lips.
Mechanical digestion
The process of breaking up of large food particles into smaller particles using the teeth, tongue, and lips is called _____________ (__________)
Mastication (chewing)
____________ helps to increase the surface area-to-volume ratio of the food, creating more surface area for enzymatic digestion as it passes through the gut tube. It also moderates the size of food particles entering the lumen of the alimentary canal.
Chewing/mastication
____________ digestion is the breaking down of chemical bonds in the macromolecules that make up food.
Chemical digestion
___________ aids mechanical digestion by moistening and lubricating food.
Saliva
The three pairs of salivary glands, like all glands of the digestive tract, are innervated by the ______________ nervous system.
Parasympathetic nervous system
_______________ (also known as __________) is capable of hydrolyzing starch into smaller sugars (maltose and dextrins)
Salivary amylase (ptyalin)
_____________, contained in saliva, catalyzes the hydrolysis of lipids.
Lipase
Our muscular tongue forms the food into a ___________, which is forced back to the pharynx and swallowed.
Bolus
The ______________ nervous system increases the viscosity of saliva, which is why dry mouth and even a tacky sensation in the mouth occurs during a fight-or-flight response.
Sympathetic nervous system
The __________ is the cavity that leads from the mouth and posterior nasal cavity to the esophagus.
Pharynx
The pharynx can be divided into three parts: the _____________ (behind the nasal cavity), the _____________ (at the back of the mouth), and the _________________ (above the vocal cord).
- 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.
Epiglottis
______________ is a muscular tube that connects the pharynx to the stomach.
Esophagus
While the top of the esophagus is under __________ (voluntary) nervous system, the bottom - and most of the gastrointestinal tract, for that matter - is under __________ (involuntary) nervous control.
- Somatic nervous system
- Autonomic nervous system
Certain factors such as exposure to chemicals, infectious agents, physical stimulation in the posterior pharynx, and even cognitive stimulation, can lead to reversal of peristalsis in the process of ___________ (____________).
Emesis (vomiting)
Swallowing is initiated in the muscles of the oropharynx, which constitute the ____________________.
Upper esophageal sphincter
As the bolus approaches the stomach, a muscular ring known as the __________________ (______________) relaxes and opens to allow the passage of food.
Lower esophageal sphincter (cardiac sphincter)
The ____________ is a highly muscular organ with a capacity of approximately two litres.
Stomach
The stomach can be divided into 4 main anatomical divisions: the __________ and ___________, which contain mostly gastric glands.
- Fundus
- Body
The stomach can be divided into 4 main anatomical divisions: the ____________ and ___________, which contain mostly pyloric glands.
- Antrum
- Pylorus
The internal curvature of the stomach is called the ______________.
Lesser curvature
The external curvature of the stomach is called the _______________.
Greater curvature
The lining of the stomach is thrown into folds called ___________.
Rugae
The ____________ respond to signals from the vagus nerve of the parasympathetic nervous system, which is activated by the brain in response to the sight, taste, and smell of food.
Gastric glands
Gastric glands have three different cell types: ___________ cells, __________ cells, and ____________ cells.
- Mucous cells
- Chief cells
- Parietal cells
_____________ produce the bicarbonate-rich mucus that protects the muscular wall from the harshly acidic (pH = 2) and proteolytic environment of the stomach.
Mucous cells
______________ is a combination of secretions from the other two cell types in the gastric glands: chief cells and parietal cells.
Gastric juice
The ______________ secrete pepsinogen.
Chief cells
Pepsinogen is the inactive, zymogen form of ____________, a proteolytic enzyme.
Pepsin
Hydrogen ions in the stomach are secreted by _____________ as hydrochloric acid, cleave pepsinogen to pepsin.
Parietal cells
_________ digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments.
Pepsin
In addition to HCl, parietal cells secrete _______________, a glycoprotein involved in the proper absorption of vitamin B12.
Intrinsic factor
The pyloric glands contain __________ that secrete gastrin.
G-cells
__________ induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract, mixing its contents.
Gastrin
The stomach secretes 6 products:
1. _____________ (kills microbes, denatures proteins, and converts pepsinogen into pepsin)
2. ______________ (cleaved in the stomach to pepsin; an enzyme that partially digests proteins)
3. Mucus (protects mucosa)
4. _______________ (protects mucosa)
5. Water (dissolves and dilutes ingested material)
6. _____________ (required for normal absorption of vitamin B12)
- HCl
- Pepsinogen
- Mucus
- Bicarbonate
- Water
- Intrinsic factor
The ____________ consists of three segments: the duodenum, the jejunum, and the ileum.
Small intestine
Food leaves the stomach through the ____________ and enters the duodenum.
Pyloric sphincter
_______________ are present on the luminal surface of cells lining the duodenum and break down dimers and trimers of biomolecules into absorbable monomers.
Brush-border enzymes
The duodenum secretes ______________, which is involves in the activation of other digestive enzymes from the accessory organs of digestion.
Enteropeptidase
The duodenum secretes hormones like _____________ and ___________________ (____) into the bloodstream.
- Secretin
- Cholecystokinin (CCK)
The _________________ digest disaccharides.
Disaccharidases
______________ digests maltose.
Maltase
_____________ digests isomaltose.
Isomaltase
__________ digests lactose.
Lactase
__________ digests sucrose
Sucrase
____________ break down proteins (or peptides, as the name implies).
Peptidases
____________ is a peptidase secreted by glands in the duodenum that removes the N-terminal amino acid from a peptide.
Aminopeptidase
____________ cleave the peptide bonds of dipeptides to release free amino acids.
Dipeptidases
________________(formerly called _____________) is an enzyme critical for the activation of trypsinogen, a pancreatic protease, to trypsin.
- Enteropeptidase
- Enterokinase
Enteropeptidase can activate ________________ A and B to their active forms.
Procarboxypeptidase A and B
___________ is a peptide hormone that causes pancreatic enzymes to be released in the duodenum.
Secretin
___________ regulates the pH of the digestive tract by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from the pancreas.
Secretin
Secretin is a ______________, a hormone that slows motility through the digestive tract.
Enterogastrone
______________ (_____) is secreted in response to the entry of chyme (specifically, amino acids and fat in the chyme) into the duodenum.
Cholecystokinin (CCK)
_____________ peptide hormone stimulates the release of both bile and pancreatic juices and also acts in the brain, where it promotes satiety.
Cholecystokinin (CCK)
_________ is a complex fluid composed of bile salts, pigments, and cholesterol.
Bile
___________ are derived from cholesterol and are not enzymes. They serve an important tool in the mechanical digestion of fats and ultimately facilitate the chemical digestion of lipids.
Bile salts
____________ have hydrophobic and hydrophilic regions, allowing them to serve as a bridge between aqueous and lipid environments.
Bile salts
___________ are much like common soaps and detergents. They emulsify fats and cholesterol into micelles.
Bile salts
__________ gets the fats into the solution and increases their surface area by placing them in micelles (mechanical digestion).
Bile
___________ can come in, once the micelles form, to hydrolyze the ester bonds holding the lipids together (chemical digestion).
Lipase
_____________ are a complex mixture of several enzymes in a bicarbonate-rich alkaline solution.
Pancreatic juices
The ____________ from the pancreatic juices helps to neutralize acidic chyme, as well as provide an ideal working environment for the digestive enzymes, which are most active around pH 8.5.
Bicarbonate
__________ is active in the stomach and works best at pH 2.
Pepsin
The bulk of the pancreas, however, is made oof exocrine cells called ____________ that produce pancreatic juices.
Acinar cells
______________ breaks down large polysaccharides into small disaccharides and is therefore responsible for carbohydrate digestion in the small intestine.
Pancreatic amylase
The pancreatic peptidases (_____________, _______________, and ______________ A and B) are released in their zymogen form, but once activated are responsible for protein digestion.
- Trypsinogen
- Chymotrypsinogen
- Carboxypeptidase A and B
________________, produced by the duodenum, is the master switch. It converts trypsinogen to trypsin, which can then activate the other zymogens, and also activates procarboxypeptidase A and B.
Enteropeptidase
The pancreas secretes _____________, which is capable of breaking down fats into free fatty acids and glycerol.
Pancreatic lipase
Like all exocrine cells, acinar cells secrete their products into ducts. These ducts then empty into the duodenum through the _______________ and ________________.
- Major duodenal papillae
- Minor duodenal papillae
____________ connect the liver with both the gallbladder and small intestine.
Bile ducts
__________ is produced in the liver and travels down the bile ducts where it may be stored in the gallbladder or secreted into the duodenum.
Bile
The liver receives all blood draining from the abdominal portion of the digestive tract through the _________________.
Hepatic portal vein
The liver takes up excess sugar to create _____________, the storage form of glucose, and stores fats as ________________.
- Glycogen
- Triacylglycerols
The liver can produce glucose for the rest of the body through _____________ and ______________.
- Glycogenolysis
- Gluconeogenesis
The major pigment in bile is _____________, which is a byproduct of the breakdown of hemoglobin.
Bilirubin
Bilirubin travels to the liver, where it is ____________ (attached to a protein) and secreted into the bile for excretion.
Conjugated
If the liver is unable to process or excrete bilirubin (due to liver damage, excessive red blood cell destruction, or blockage of the bile ducts), ____________ or yellowing of the skin may occur.
Jaundice
The liver synthesizes ___________, a protein that maintains plasma oncotic pressure and also serves as a carrier for many drugs and hormones.
Albumin
The liver synthesizes _____________ that are used during blood coagulation.
Clotting factors
The ____________ is located just beneath the liver and both stores and concentrates bile.
Gallbladder
Upon release of cholecystokinin (CCK), the gallbladder contracts and pushes bile out into the ______________.
Biliary tree
The ______________ is a common site of cholesterol or bilirubin stone formation.
Gallbladder
The small intestine is lined with _______, which are small, finger-like projections from the epithelial lining.
Villi
Each villus has many ___________, drastically increasing the surface area available for absorption.
Microvilli
At the middle of each villus there is a capillary bed for the absorption of water-soluble nutrients and a __________, a lymphatic channel that takes up fats for transport into the lymphatic system.
Lacteal
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
The lacteals, at the beginning of the lymphatic system, converge and enter the venous circulation at the _____________ in the base of the neck, which empties into the left subclavian vein.
Thoracic duct
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 vitamins
Water passes not only ______________ (across the cell membrane), but also _______________ (squeezing between cells) to reach the blood.
- Transcellularly
- Paracellularly
The _____________ is simply an out pocketing that accepts fluid exiting the small intestine through the ileocecal valve.
Cecum
The cecum is the site of attachment of the ____________.
Appendix
The ___________ ‘s main function is to absorb water and salts (such as sodium chloride) from the undigested material left over from the small intestine.
Colon
The small intestine actually absorbs much more water than the colon, so the colon primarily concentrates the remaining material to form _________.
Feces
The ____________ serves as a storage site for feces, which consists of indigestible material, water, bacteria (E. coli and others), and certain digestive secretions that are not reabsorbed (enzymes and some bile).
Rectum
The __________ is the opening through which wastes are eliminated and consists of two sphincters.
Anus
The _______________ of the anus is under voluntary control (somatic), but the ________________ of the anus is under involuntary control (autonomic).
- External anal sphincter
- Internal anal sphincter
Bacteria in the gut produce ___________, which is essential for the production of clotting factors, and ___________ (vitamin ____), which is a coenzyme for many metabolic enzymes.
- Vitamin K
- Biotin (vitamin K)
