-
What process adds water to large molecules in the GI tract in order to break them down into monomers?
hydrolysis
-
Within what organ does absorption of the products of digestion take place?
the small intestine
-
What process involves taking food into the mouth?
ingestion
-
What is the physiological term for the chewing of food and mixing it with saliva?
mastication
-
What is the physiological term for swallowing?
deglutition
-
What are rhythmic wave-like contractions that move food through the GI tract?
peristalsis
-
What is the passage of digested end products into the blood or lymph?
absorption
-
What is the complete term for GI tract?
gastrointestinal 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.
- oral cavity
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
-
List the accessory organs of the digestive system.
- teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
-
What is the general term for the layers of the digestive system?
tunics
-
List the four layers of the digestive system from the lumen outwards.
- mucosa
- submucosa
- muscularis
- serosa
-
What is the absorptive layer of the GI tract?
the mucosa
-
What increases the surface area of the absorptive surface of the GI tract?
- the long length of the GI tract
- folds
- villi
- microvilli
-
What are the mucus-secreting cells of the GI tract?
goblet cells
-
What is the thick, highly vascular layer of connective tissue where absorbed molecules enter blood and lymphatic vessels?
submucosa
-
What layer of the GI tract is responsible for segmental contractions and peristalic movements?
muscularis
-
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?
the serosa
-
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?
S2-S4
-
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?
salivary amylase
-
What substance is chemically digested by the enzyme in saliva?
starch
-
During swallowing, what structure covers the glottis and prevents food from entering the larynx?
the epiglottis
-
What structure connects the oral and nasal cavities to the larynx and esophagus?
the pharynx
-
What structure connects the pharynx to the stomach?
the esophagus
-
What type of muscle occurs in the esophagus?
- the upper third contains skeletal muscle
- the middle third contains a mixture of skeletal and
- smooth muscle
- 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?
peristalsis
-
What circular muscle prevents reflux from the stomach into the esophagus?
the gastroesophageal sphincter
-
What is the most distensible part of the GI tract?
the stomach
-
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?
the cardia
-
What is the dom-]shaped region of the stomach?
the fundus
-
What is the main portion of the stomach?
the body
-
What is the terminal, funnel-shaped region of the stomach?
the pylorus
-
What are the folds within the stomach?
gastric rugae
-
What are the cells that line the gastric pits within the folds of the gastric mucosa?
gastric glands
-
What cells of the gastric glands secrete HCl?
parietal cells
-
What cells of the gastric glands secrete pepsinogen?
chief cells
-
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?
the vagus
-
What hormone stimulates the secretion of HCl into the stomach?
gastrin
-
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?
proteins
-
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?
peptic ulcer
-
What bacterium is associated with most gastric ulcers?
Helicobacter pylori
-
What is the first segment of the small intestine?
the duodenum
-
What is the middle segment of the small intestine?
the jejunum
-
What is the terminal segment of the small intestine?
the ileum
-
What lie within each villus of the small intestine?
- lymphocytes
- capillaries
- 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
- electrolytes
- B & K vitamins
- folic acid
-
What term refers to the community of organisms living in the large intestine?
microflora
-
About how many species of bacteria live in the large intestine?
400
-
What do the bacteria of the large intestine produce?
- folic acid
- vitamin K
- fatty acids
-
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.
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
- anal canal
-
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?
90%
-
How does the large intestine absorb water?
By setting up an osmotic gradient established by Na+/K+ pumps
-
What can the large intestine secrete?
Na+
-
What is the medical term for the waste products eliminated after digestion?
feces
-
What is the medical term for the elimination of feces?
defecation
-
What is the largest internal organ?
the liver
-
What is the histological term for cells that carry out the functions of the liver?
heypatocytes
-
What structures do hepatocytes form in the liver?
hepatic plates
-
How many cells thick are hepatic plates?
1 or 2 cells
-
What separates hepatic plates?
fenestrated sinusoids
-
What is the only organ capable of regenerating itself?
the liver
-
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?
liver lobules
-
What product of the liver is secreted into the duodenum and takes part in the digestive process?
bile
-
What is the recirculation of compounds between the liver and intestine?
enterohepatic circulation
-
What are the five major categories of liver function?
- detoxification
- carbohydrate metabolism
- lipid metabolism
- protein synthesis
- secretion of bile
-
How much bile is produced every day?
250-1500 ml
-
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?
albumin
-
Free bilirubin combines with glucuronic acid to form what substance?
conjugated bilirubin
-
What form of bilirubin is secreted in bile?
conjugated bilirubin
-
Conjugated bilirubin is converted by intestinal bacteria into what substance?
urobilinogen
-
What form of is absorbed by the intestine and is filtered out of the blood by the kidneys?
urobilinogen
-
What makes urine yellow and feces brown?
urobilinogen
-
Where is bile made?
in the liver
-
What structure functions to store bile?
the gallbladder
-
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?
the liver
-
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?
ketogenesis
-
What substances are formed by the liver during fasting to provide an energy source for the body?
ketone bodies
-
What substance formed by the liver contributes the most to the colloid osmotic pressure of the blood?
albumin
-
What organ makes albumin in order to maintain the osmotic pressure of blood?
the liver
-
What organ produces clotting factors?
the liver
-
What accessory digestive organ lies deep to the stomach?
the pancreas
-
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?
- trypsin
- lipase
- pancreatic amylase
-
What substance formed by the pancreas rises the pH of chyme?
bicarbonate
-
What enzyme digest proteins within the lumen of the small intestine?
trypsin
-
What enzyme digest carbohydrates within the lumen of the small intestine?
pancreatic amylase
-
What enzyme digest fats within the lumen of the small intestine?
lipase
-
What substances complete digestion on the epithelium of the small intestine?
brush border enzymes
-
What are the three phases of extrinsic gastric control?
- cephalic
- gastric
- intestinal
-
What phase of extrinsic gastric control is carried out by the brain via the vagus nerve?
cephalic
-
What phase of gastric control involves the arrival of food in the stomach?
gastric phase
-
What hormone produced by the stomach brings about the secretion of HCl and pepsinogen?
gastrin
-
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?
the enteric nervous system
|
|
