What process adds water to large molecules in the GI tract in order to break them down into monomers?
Within what organ does absorption of the products of digestion take place?
the small intestine
What process involves taking food into the mouth?
What is the physiological term for the chewing of food and mixing it with saliva?
What is the physiological term for swallowing?
What are rhythmic wave-like contractions that move food through the GI tract?
What is the passage of digested end products into the blood or lymph?
What is the complete term for GI tract?
What are the two general categories of structures that form the digestive system?
the gastrointestinal tract and the accessory digestive organs
List the organs of the gastrointestinal tract.
List the accessory organs of the digestive system.
What is the general term for the layers of the digestive system?
List the four layers of the digestive system from the lumen outwards.
What is the absorptive layer of the GI tract?
What increases the surface area of the absorptive surface of the GI tract?
the long length of the GI tract
What are the mucus-secreting cells of the GI tract?
What is the thick, highly vascular layer of connective tissue where absorbed molecules enter blood and lymphatic vessels?
What layer of the GI tract is responsible for segmental contractions and peristalic movements?
What are the two layers of the muscularis of the GI tract?
the inner circular layer and the outer longitudinal layer
What is the outer most layer of the GI tract?
What cranial nerve carries impulses to and from the digestive system?
the vagus nerve
What regions of the spinal cord carry impulses to and from the GI tract?
What is the effect of the parasympathetic division of the ANS on the digestive system?
It stimulates motility and secretions
What is the effect of the sympathetic activity on the digestive system?
It reduces peristalsis and secretory activity
What intrinsic system of the GI tract controls its movements?
the enteric nervous system
What two general categories of signals influences the motiliy of the GI tract?
paracrine and endocrea
What enzyme is contained in saliva?
What substance is chemically digested by the enzyme in saliva?
During swallowing, what structure covers the glottis and prevents food from entering the larynx?
What structure connects the oral and nasal cavities to the larynx and esophagus?
What structure connects the pharynx to the stomach?
What type of muscle occurs in the esophagus?
the upper third contains skeletal muscle
the middle third contains a mixture of skeletal and
the terminal portion contains only smooth muscle
Through what opening in the diaphragm does the esophagus pass?
the esophageal hiatus
What action propels food through the GI tract?
What circular muscle prevents reflux from the stomach into the esophagus?
the gastroesophageal sphincter
What is the most distensible part of the GI tract?
What are the functions of the stomach?
storage of food
initial digestion of proteins
killing bacteria with high acidity
moving chyme into the intestine
What circular muscle prevents chyme from leaving the stomach and entering the small intestine?
the pyloric sphincter
What is the region of the stomach where the esophagus enters it?
What is the dom-]shaped region of the stomach?
What is the main portion of the stomach?
What is the terminal, funnel-shaped region of the stomach?
What are the folds within the stomach?
What are the cells that line the gastric pits within the folds of the gastric mucosa?
What cells of the gastric glands secrete HCl?
What cells of the gastric glands secrete pepsinogen?
What process moves H+ into the lumen of the stomach?
active transport via an H+/K+ pump
What nerve stimulates the secretion of HCl into the stomach?
What hormone stimulates the secretion of HCl into the stomach?
What are the functions of HCl in the stomach?
It denatures proteins to make them more digestible, converts pepsinogen into pepsin, and kills bacteria
Both HCl and pepsin can damage the gastric lining and produce a peptic ulcer. What normally prevents this?
There is an adherent, stable layer of mucus on the lining. This mucus contains bicarbonate for neutralizing HCl and is a barrier to the actions of pepsin. The gastric epithelial cells contain tight junctions to prevent HCl and pepsin from penetrating the surface
How often are gastric epithelial cells replaced?
every three days
What does pepsin digest?
What happens to salivary amylase in the stomach?
It is inactivated by the acidity
What commonly ingested substances are absorbed in the stomach?
alcohol and aspirin
What is the erosion of the mucous membrane of the stomach or duodenum caused by the action of HCl?
What bacterium is associated with most gastric ulcers?
What is the first segment of the small intestine?
What is the middle segment of the small intestine?
What is the terminal segment of the small intestine?
What lie within each villus of the small intestine?
a central lacteal
The microvilli of the small intestine create what?
a brush border
What are attached to the microvilli of the small intestine to aid in chemical digestion?
brush border enzymes
List the functions of the large intestine.
absorption of H2O
B & K vitamins
What term refers to the community of organisms living in the large intestine?
About how many species of bacteria live in the large intestine?
What do the bacteria of the large intestine produce?
How do the bacteria of the large intestine protect their host?
They reduce the ability of pathogenic bacteria to infect the large intestine
List the regions of the large intestine.
What circular muscle lies between the small intestine and the large intestine?
the ileocecal valve
The small intestine absorbs most of the water ingested. Of the water entering the large intestine, what percentage is absorbed?
How does the large intestine absorb water?
By setting up an osmotic gradient established by Na+/K+ pumps
What can the large intestine secrete?
What is the medical term for the waste products eliminated after digestion?
What is the medical term for the elimination of feces?
What is the largest internal organ?
What is the histological term for cells that carry out the functions of the liver?
What structures do hepatocytes form in the liver?
How many cells thick are hepatic plates?
1 or 2 cells
What separates hepatic plates?
What is the only organ capable of regenerating itself?
In some cases, such as alcohol abuse or viral hepatitis, regeneration of the liver does not occur. In such cases alcohol abuse or hepatitis can lead to what conditions?
liver fibrosis and, ultimately, cirrhosis
What vascular network carries the products of digestion from the GI tract to the liver?
the hepatic portal system
The liver receives blood from what two vessels?
the hepatic portal system and the hepatic artery
What are the functional units of the liver?
What product of the liver is secreted into the duodenum and takes part in the digestive process?
What is the recirculation of compounds between the liver and intestine?
What are the five major categories of liver function?
secretion of bile
How much bile is produced every day?
Where is bile pigment (bilirubin) produced?
From what is bilirubin produced?
heme groups (minus iron) from hemoglobin
Free bilirubin is carried in the blood on what molecule?
Free bilirubin combines with glucuronic acid to form what substance?
What form of bilirubin is secreted in bile?
Conjugated bilirubin is converted by intestinal bacteria into what substance?
What form of is absorbed by the intestine and is filtered out of the blood by the kidneys?
What makes urine yellow and feces brown?
Where is bile made?
in the liver
What structure functions to store bile?
What is the digestive function of bile?
to emulsify fats
The liver removes hormones, drugs, and other biologically active molecules from the blood by what three processes?
excretion into bile
phagocytosis by Kupffer cells
chemical alteration of molecules
What organ forms urea?
Through what two processes does the liver remove glucose from the blood?
glycogenesis and lipogenesis
Through what two processes does the liver release glucose into the blood?
glycogenolysis and gluconeogenesis
Through what process does the liver convert free fatty acids into ketone bodies?
What substances are formed by the liver during fasting to provide an energy source for the body?
What substance formed by the liver contributes the most to the colloid osmotic pressure of the blood?
What organ makes albumin in order to maintain the osmotic pressure of blood?
What organ produces clotting factors?
What accessory digestive organ lies deep to the stomach?
What clusters of cells within the pancreas carry out that organís endocrine function?
the islet cells
What two hormones are produced by the pancreas?
glucagon and insulin
What three digestive enzymes are made in the pancreas?
What substance formed by the pancreas rises the pH of chyme?
What enzyme digest proteins within the lumen of the small intestine?
What enzyme digest carbohydrates within the lumen of the small intestine?
What enzyme digest fats within the lumen of the small intestine?
What substances complete digestion on the epithelium of the small intestine?
brush border enzymes
What are the three phases of extrinsic gastric control?
What phase of extrinsic gastric control is carried out by the brain via the vagus nerve?
What phase of gastric control involves the arrival of food in the stomach?
What hormone produced by the stomach brings about the secretion of HCl and pepsinogen?
What stimulates the release of gastrin?
short polypeptides and amino acids
What happens in the gastric phase of digestion if the pH in the stomach drops to less than 2.5?
HCl production decreases and will stop at a pH of 1
What phase of gastric control begins as chyme enters the small intestine?
the intestinal phase
What are the neural and hormonal actions of the small intestine on the stomach as chyme enters the small intestine?
A neural reflex inhibits gastric motility and secretion. Fat stimulates the small intestine to secrete enterogasterones (hormones) which also inhibit gastric motility and secretion
What is the network of submucosal and myenteric plexuses within the intestines?