Exam 4 - Digestive System Flashcards
What are the five stages of digestion?
Ingestion, digestion, absorption, compaction, and defecation
What is ingestion?
Selective intake of food
What is digestion?
Mechanical and chemical breakdown of food into a form usable by the body
What is absorption?
Uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
What is compaction?
Absorbing water and consolidating the indigestible residue into feces
What is defecation?
Elimination of feces
What is mechanical digestion?
The physical breakdown of food into smaller particles
What is chemical digestion?
a series of hydrolysis reactions that break dietary macromolecules into their monomers
What are polysaccharides broken down into?
Monosaccharides
WHat are proteins broken down into?
Amino acids
What are fats broken down into?
Monoglycerides and fatty acid
What are nucleic acids broken down into?
Nucleotides
What is the digestive tract?
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
What is the gastrointestinal tract?
Stomach and intestines
What are accessory organs?
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
What is the enteric nervous system?
Nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow
What is mesenteries?
Connective tissue sheets that suspend stomach and intestines from abdominal wall
What is the parietal peritoneum?
A serous membrane that lines the wall of the abdominal cavity
What is the lesser omentum?
A ventral mesentery that extends from the lesser curvature of the stomach to the liver
What is the greater omentum?
Hangs from the greater curvature of the stomach
What is the mesocolon?
Extension of the mesentery that anchors the colon to the abdominal wall
What is intraperitoneal?
When an organ is enclosed by mesentery on both sides
What is retroperitoneal?
When an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only
What is the functions of the mouth?
Ingestion, taste and sensory responses to food, chewing and chemical digestion, swallowing, speech, and respiration
How many teeth does an adult have?
32
What are the different types of teeth?
3 incisors, 1 canine, 2 premolars, and 3 molars
What is salvia do?
Moistens mouth, begins starch and fat digestion, dissolves molecules, and inhibits bacterial growth
What is salivary amylase?
Enzyme that begins starch digestion in the mouth
What is lingual lipase?
Enzyme that is activated by stomach acid and digests fat after food is swallowed
What is mucus?
Binds and lubricates a mass of food and aids in swallowing
What is lysozyme?
Enzyme that kills bacteria
What is immunoglobulin A?
An antibody that inhibits bacterial growth
What is electrolytes?
Na, K, Cl, Phosphate, and bicarbonate
What are intrinsic salivary glands?
Small glands dispersed amid other oral tissues
What are extrinsic salivary glands?
Three pairs connected to oral cavity by ducts
What is a bolus?
Mass swallowed as a result of saliva binding food particles into a soft, slippery, easily swallowed mass
What is the pharynx?
Muscular funnel connecting oral cavity to esophagus and nasal cavity to larynx
What does the inferior constrictor do?
When not swallowing it remains contracted to exclude air from the esophagus
What is the esophagus?
Straight muscular tube that extends from pharynx to cardiac orifice of stomach
What is the stomach?
A muscular sac in upper left abdominal cavity immediately inferior to diaphragm
Where does most digestion occur?
Small intestines
What are the 4 regions of the stomach?
Cardia, fundus, body, and pyloric region
What is the pylorus?
Narrow passage to duodenum
What are stomach receives and what are they from?
Parasympathetic fibers from vagus
Sympathetic fibers from celiac ganglia
What are gastric pits?
Depressions in gastric mucosa
What are mucous cells?
Secrete mucus; mainly in cardiac and pyloric glands
What are regenerative cells?
Found in base of pit and in beck of gland
What are parietal cells?
Secrete HCl, Intrinsic factor ,and ghrelin
What are chief cells?
Most numerous; secrete gastric lipase and pepsinogen
What are enteroendocrine cells?
Concentrated at end of gland; secrete hormones and paracrine messengers
What are gastric juice?
Mixture of water, HCl, and pepsin; 2-3L per day
What does HCl do?
Activates pepsin and lingual lipase; breaks up connective tissue and plant cell wall; converts Fe3 to Fe2
What are zymogens?
Digestive enzymes secreted as inactive proteins
What is pepsinogen?
Zymogen secreted by chief cells
What does HCl do to pepsinogen?
Removes amino acid and forms pepsin
What is the autocatalytic effect of pepsinogen?
As some pepsin is formed, it converts more pepsinogen into more pepsin
What does pepsin do?
Digests dietary proteins into shorter peptides
What does gastric lipase do?
Produced by chief cells; digests 10-15% of dietary fats in stomach
What does intrinsic factor do?
Essential to absorption of vitamin B12 by the small intestines
What is the importance of vitamin B12?
It is needed to synthesize hemoglobin
What is the three ways the stomach is protected?
Mucous coat, tight junctions, and epithelial cell replacement
What is the mucous coat?
It is a thick, alkaline mucus resists action of acid and enzymes
What is tight junctions?
Between epithelial cells to prevent gastric juice from seeping through
What is epithelial cell replacement?
Cells live only 3-6 days and sloughed off into the chyme and digested with food
What happens if the methods of protecting the stomach are broken down?
It can cause inflammation and peptic ulcer
What causes most ulcers?
The acid resistance bacteria helicobacter pylori
What does the small intestines receive?
Chyme from stomach and secretions from liver and pancreas
Where is the liver and what is its function?
Inferior to the diaphragm and secretes bile which contributes to digestion
What are the 4 lobes of the liver?
Right, left, quadrate, and caudate
What does the falciform ligament do on the liver?
Separates the right lobe from the left lobe
What is the round ligament on the liver?
It is the fibrous remnant of umbilical vein
What is porta hepatis?
Irregular opening between quadrate and caudate lobes
What separates hepatic lobules?
Stroma
What is between lobules?
A hepatic triad of two vessels and bile ductule
What do hepatocytes do after a meal?
They are absorbed from the blood
What do hepatocytes do between meals?
Break down stored glycogen and release glucose, remove degrade, and secrete products into the blood
Where does the central vein lead to?
Right and left hepatic veins
What are bile canaliculi?
Narrow channels into which the liver secretes bile
What is the common hepatic duct?
Formed from convergence of right and left hepatic ducts on inferior side of the liver
What is the cysticduct?
From gallbladder and joins common hepatic duct
What is the bile duct?
Formed from union of cystic and common hepatic ducts
What is the purpose of the gallbladder?
To store and concentrate bile by absorbing water and electrocytes
Where does the neck of the gallbladder lead to?
The cystic duct
What is bile?
Yellow-green fluid that contains minerals, bile pigments, and bile acid
What is bilirubin?
Principal pigment derived from the decomposition of hemoglobin
What are bile acids?
Steroids synthesized from cholesterol
Where and how much bile acid are reabsorbed?
80% of bile acids are reabsorbed in the ileum and returned to the liver
What are the sections of the pancreas?
The head encircled by duodenum, a body, and a tail
What is the endocrine portion of the pancreas?
Pancreatic islets that secrete insulin and glucagon
What is the exocrine portion of the pancreas?
99% of pancreas that secretes 1.2L to 1.5L of pancreatic juice per day
Where is the pancreatic duct?
Runs lengthwise through middle of the gland
Where is the accessory pancreatic duct?
Smaller duct that branches from the main pancreatic duct
What is pancreatic juice?
Alkaline mixture of water, enzymes, zymogens, NaCO2, and other electrolytes
What are the pancreatic zymogens?
Trypsinogen, chymotrypsinogen, and procarboxypeptidase
What is trypsinogen?
Secreted into intestinal lumen and coverts to trypsin that is an autocatalytic
What is chymotrypsinogen?
Converted to chymotrypsin by trypsin
What is proarboxypeptidase?
Converted to carboxypeptidase by trypsin
What does pancreatic amylase do?
Digest starch
What does pancreatic lipase do?
Digest fat
What does the ribonuclease and deoxyribonuclease do?
Digest RNA and DNA respectively
What are the 3 stimuli responsible for the release of pancreatic juice and bile?
Acetylcholine, cholecystokinin, and secretin
Where is Acetylcholine from?
Vagus and enteric nerves
Where is cholecystokinin from?
Secreted by mucosa of duodenum in response to arrival of fats in small intestine
Where is secretin from?
Released from duodenum in response to acidic chyme arriving from the stomach
What does secretin do?
Stimulates ducts of liver and pancreas to secrete more sodium bicarbonate to raise pH level
What does cholecystokinin do?
Stimulates pancreatic acini to secrete enzymes
What does acetylcholine do?
Stimulates acini to secrete enzymes during cephalic phase
Where does most of the chemical digestion and nutrient absorption occur?
Small intestine
What is the duodenum?
A region of the small intestine, and begins at pyloric valve
What happens in the duodenum?
Fats are broken up by bile acids, pepsin is inactivated by increase pH, pancreatic enzymes perform chemical digestion
Where is the jejunum?
First 40% of small intestineW
What happens in the jejunum?
Most digestion and nutrient absorption
Where is the ileum?
Forms last 60% of small intestine
What does the ileum look like?
Thinner, less muscular and vascular
What are peyer patches?
Prominent lymphatic nodules in cluster on the slide opposite the mesenteric attachment
What are ileocecal junction?
End of small intestine
What is the ileocecal valve?
A sphincter formed by the thickened muscularis of the ileum
What are both the jejunum and ileum?
Intraperitoneal covered with serosa
What are circular folds?
Largest fold of intestinal wall that increase surface area to help with digestion and absorption
What are villi?
Little fingers-like projections that increase surface area by factor of 10
What are microvilli?
Villi on top of the villi (brush border) to increase surface area by a factor of 20
Where are the brush border enzymes?
Contained in plasma membrane of microvilli
What does the brush border enzyme do?
Final stages of enzymatic digestion
What are contact digestion?
Chyme must contact the brush border for digestion to occur
What is segmentation?
Movement in which stationary ring-like constriction appear in several places along the intestine
What does peristalsis do?
Move contents of small intestine toward colon
What are carbohydrates?
Sugar and starches
What are the different types of monosaccharides?
Glucose, galactose, and fructose
What are the different types of disaccharides?
Maltose, sucrose, and lactose
How is maltose formed?
Glucose + glucose
How is sucrose made?
Glucose + fructose
How is lactose made?
Glucose + galactose
What are polysaccharides?
Starch made from glucose
What is the most common startch?
amylose
How are the macromolecules absorbed?
They are all broken down into monosaccharides
How are protein made?
Amino acids linked by peptide bonds
What are the enzymes that digest proteins?
Proteases or peptidases
How are proteins absorbed?
Must be broken down into single amino acids
What are lipids?
Fatty acids, triglycerides, and monoglycerides
What digest lipids?
The enzyme lipase
What is the most digestible dietary carbohydrate?
Starch
What is starch first digested to?
Oligosaccharides
What are oligosaccharides digested to?
Disaccharide maltose
What are maltose digested to?
Glucose
What does salivary amylase do?
Hydrolyzes starch into oligosaccharides
What happens to people without lactase?
Lactose passes undigested into large intestine
What does lactose in large intestine do?
Increases osmolarity of intestinal contents and causes water retention
What does proteases do?
Enzymes that digest proteins
What are lipases?
Fat-digesting enzymes
What happens to vitamins?
They are absorbed unchanged
How much water is absorbed by small intestine
8 L
How much water is absorbed by large intestine?
0.8 L
What is diarrhea?
Occurs when large intestine absorbs too little water
What is constipation?
Occurs when feal movement is slow, too much water gets reabsorbed
Where does the large intestines form?
At the cecum
What is the rectum?
Portion ending at anal canal
What is the anal canal?
Final 3 cm of the large intestine
What are taenia coli?
Longitudinal fibers conc in three thickened, ribbon-like strips
What are haustra?
Pouches in the colon caused by the muscle tone of the taenia coli
What is internal anal sphincter?
Smooth muscle of muscularis externa
What is the external anal sphincter?
Skeletal muscle of pelvic diaphragm
What are feces consist of?
75% water and 25% solids
How often do haustral contractions occur?
every 30 mins
What happens to starch in the mouth?
The salivary amylase breaks it down into oligosaccharides and maltose
What happens to oligosaccharides in the small intestine?
Pancreatic amylase breaks it down into maltose
What happens to lactose in the small intestine?
It splits into fructose and galactose
What happens to protein in the stomach?
Pepsin breaks it into small peptides
what happens to small peptides in the small intestine?
Trypsin, chymotrypsin, carboxypeptidase break it down into dipeptides; turn into free amino acids
What happens to fats in the stomach?
The lingual lipase breaks it into free fatty acids
What happens to fats in small intestine?
Pancreatic lipase breaks it into monoglyceride and free fatty acids; they get turned into triglycerides
