The Digestive System Flashcards
Define metabolism
the biochemical reactions that allow a cell or organism to extract energy from its surroundings and use that energy for homeostais
Define organic
molecule based on carbon
What are the four important classes of macromolecules
carbohydrates, lipids, proteins, nucleic acids
Carbohydrates consist of …
monosaccharides, dissarcharides, and polysaccharides
What is the difference between saturated and unsaturated fats?
unstaturated; double bonds, bend in fatty acid chain; liguid at room temp(can’t stack easily)
-saturated; no double bonds, no bend, solid at room temp
What is Antherosclerosis and what could it lead to?
Lipid containing deposits(plaque ) build up in the walls of blood vessels
-plaques reduce blood flow which could lead to heart attack or stroke
What are substances animals are required to have in their diet that they can not make for themselves?
essential amino acids, fatty acids, minerals, vitamins
What does the stomach do in digestion
stores food and continues digestion
What does the small intestine do in digestion
completes digestion and begins the absorption of nutrients
What does the large intestine do in digestion
primarily absorbs water and mineral ions from digestive residues
What are sphincters
rings of smooth muscle form valves between major regions of digestive tract
What are common structures in the mammalian digestive system
mouth, pharynx, esophagus, stomach, intestines, anus
What layer is the mucosa in the vertebrate gut
Most inner layer, lines inside of gut, has epithelial cells that absorb nutrients, seal of digestive contents form body fluids
-has glandular cells: secrete enzymes, mucus, pH regulation
What is the submucosa in the vertebrate gut
Second most inner layer; elastic connective tissue, neuron network, blood, and lymph vessels
-neural network: local control of digestive activity
What is the muscularis in the vertebrate gut
Third most inner layer;formed by circular layer (constricts gut diameter) and longitudinal layer (shortens and widens gut): push contents through the gut (peristalsis)
-oblique layer (stomach only)
What is the serosa layer in the gut
outermost gut layer, made of connective tissue that is continuous with mesentery (tissue that suspends digestive organs in the abdomen)
-secretes a lubricating fluid to reduce friction between digestive organs and other organs
Define peristalsis
coordinated contractions of circular and smooth muscles produce perstaltic waves that move digestive contents from mouth to anus
Describe the digestive process all the way to the swallowing reflex
-Digestion begins in the mouth; teeth breaks down food into smaller bits
-Salivary glands in the mouth secret saliva; salivary amylase digests starch
-Food mass (bolus) is swallowed; through the pharynx and esophagus to stomach
-epiglottis blocks trachea
Describe the swallowing reflex
elevation of soft palate prevent food bolus from entering nasal passages
-pressure of tongue seals back of mouth and prevents bolus from backing up
-layrnx moves upward, pushing glottis against epiglottis to prevent bolus from entering airway
Describe the digestion process in the stomach
-stomach secretes gastric juices (HCl and pepsin), mucus
-stomach churns acid contents into chyme
Chief cells secrete:
pepsinogen: the precursor for pepsin
Parietal cells secrete..
-H+ and Cl-
When food enters the stomach..
-stretch receptors in stomach wall are activated; stimulate the release of pepsinogen, HCl, mucus
Define Gastrin
-major hormone that regulates acid secretion in the stomach
Fat is digested in..
small intestines and is digested more slowly than other nutrients, so further emptying of the stomach is prevented until fat is processed
Proteins are broken down by
endopeptidases, exopeptidases
Polysaccharides hydrolyzed by
-amylase, then disaccharidases
Triglycerides hydrolyzed
-by lipase
Nucleic acids hydrolyzed
-by nucleases (DNase, RNase)
Absorption of nutrients begins in the
-small intestine
Villi and microvilli greatly increase the …. Of intestine
surface area
What are intestinal villi
-folds of lining of small intestine
What are microvilli
projections of the plasma membrane of epithelial cells
What is the digestive process in the small intestine
In the duodenum, digestive substances from the pancreas(enzymes) and liver(bile) aid the digestive process
-Pancreas secret digestive enzymes and bicarbonate ions (neutralize acidity) into ducts that empty into the duodenum
What are the three proteolytic enzymes from the pancreas
trypsin, chymotrypsin, carboxypeptidase
What is glucagon and what does it do?
-glucagon (alpha cells): is released when blood glucose levels start to fall too low
-cause the liver to convert stored glycogen into glucose and release it into the bloodstream, raising blood glucose levels
What is insulin and what does it do?
insulin (beta cells): causes cells in the liver, muscle and fat tissue to take up glucose from the blood
-storing it as glycogen in the liver and muscle and stopping use of fat as an energy source
Liver secretion bile….
-emulsifies fats
Bile salts..
-aid in fat digestion by forming a hydrophillic coat around fats
What is lipase
-an enzyme from pancreas that hydrolyzes the fats in micelles monoglycerides and free fatty acids
Define micelle
structure that has molecules aggregated with the hydrophillic “head” regions in contact with surrounding solvent, sequestering the hydrophobic tail regions in the micelle center
What is bile, where is it made, where is it stored, and what does it do?
bile is made in the liver and the liver secretes bile
-Bile is stored in the gall bladder, released when chyme enters the small intestine
-bile emulsifies fats
What is the mechanism of bile salts and fat breakdown?
bile salts form a hydrophilic coat around the fats; churning motion of the small intestine emulsifies the fat; breaks down the fat down into droplets called micelles
-lipase hydrolyzes the fats in the micelles; producing monoglycerides and free fatty acids that can diffuse into the intestinal cell
What happens in the absorption of fatty acids
-micelles(formed by the bile salts) assist in the absorption of fatty acids, monoglycerides and other products of lipid breakdown by lipase
-micelles get digested and hydrophobic molecules in the micelle are released and enter the mucosal cell cytoplasm
-in the mucosal cell: hydrophobic molecules (fatty acids, monoglycerides) are packed into chylomicrons
What are chylomicrons, where are they secreted and what do they transport
have a protein coat provides a hydrophilic surface that keeps the droplets suspended in the cytosol of the mucosal cell
-secreted into interstitial fluid of the submucosa, taken up by lymph, blood circulation
-They transport lipids absorbed from the intestine to adipose, cardiac and skeletal muscle tissue
Where does the absorption of fluid take place and what happens?
much of it occurs in small intestine but some happens in large intestin
-active uptake of salt, passive following of water
What appetite-regulating hormone triggers hunger?
-Ghrelin
What appetite regulating hormone suppresses appetite when after meals?
-PYY peptide YY secreted by the small intestine
What appetite regulating hormone falls when body fat decreases?
leptin; with the decrease in leptin, appetite increases
With adipose cells full of fat…
-secrete leptin hormone that binds receptors in hypothalamus, stimulates the center that reduces appetite
-increase in metabolic rate(oxidize fatty acids rather than converting them to fat)
With adipose cell low in fat
-less leptin; hypothalamus increase in appetite
-decrease in metabolic rate
What is an overview of digestion
-food in stomach stretches walls. Hormone gastrin is released and stimulates the production of gastric juices
-chyme passes into the small intestine. Digestive hormones: Cholecystokinin(CKK) and secretin are released CCK stimulates the release of digestive enzymes from the pancreas and bile from the gall bladder. Secretin stimulates pancreas to release HCO3-
-if they chyme has a lot of fats, high levels of secretin and CCk inhibit peristalsis in the stomach slowing digestion
A person stops eating end of meal due to…
insulin acting on cells of hypothalamus; glucose uptake by cells in hypothalamus, mechanoreceptors in gut detect distension, chemoreceptors in gut detect food
Absorbed nutrients are delivered to the ….
liver
-nutrient molecules absorbed from the small intestine are carried by capillaries that collect into veins
-veins join to form hepatic portal vein
Hepatic portal vein leads to capillary bed in the….
liver
What happens in the liver during digestion?
excess glucose is converted into glycogen
-fats and some amino acids are converted into plasma proteins or sugars
-liver synthesizes cholesterol from lipids, carbohydrates and other substances (albumin is made in liver
-liver synthesizes lipoproteins
What are the parts of the large intestine and what’s its role in digestion
Cecum, appendix, colon, rectum
-absorbs water mineral ions from digestive contents
-at end of large intestine, undigested remnants(feces) are expelled from the anus
Digestion is regulated by:
signals from autonomic nervous system
-activity of neuron networks in digestive tube wall
-hormones secreted by digestive system
Regulatory mechanism in digestion respond to…..
-signals from sensory receptors that monitor volume and composition of digestive contents
What is the enteric nervous system
a subdivision of the peripheral nervous system, that directly controls the gastrointestinal system
-embedded in the lining of the gastrointestinal system; includes efferent, afferent, and interneurons
The sensory neurons in the enteric nervous system report on
-mechanical and chemical conditions
Through intestinal muscles, the motor neurons control …..and churning of …..Other neurons control the ……
-peristalsis; intestinal contents
-secretion fo enzymes
ENS alters its response depending on such factors as
-bulk and nutrient composition
Gastrin stimulates..
HCl and pepsinogen in stomach and contractions in stomach and intestines
Secretin is released when…
chyme entrance duodenum, prevents further acid from entering the duodenum until the chyme is neutralized; stimulates HCO3- secretion into the duodenum to neutralize the acid
CCK; cholecytokinin, inhibits….
gastic activity, allows time for nutrients in duodenum to be digested,absorbed. Stimulates release of pancreatic enzymes and bile from the gallbladder
GIP; glucose dependent insulinotropic peptide, secreted when
-a meal enters the digestive tract
-stimulates insulin release by the pancreas
-insulin stimualtes the uptake and storage of glucose
Hypothalamus important in determining appetite because
-appetite center and satiety center
Stop eating end of meal due to
-insulin acting on cells of hypothalamus, glucose uptake by cells in hypothalamus
-machanoreceptors in gut detect distension
-chemoreceptors in gut detect food
Adipose cells full of fat
-secrete leptin hormone, binds receptors in hypothalamus, stimulates the center that reduces appetite
-increase in metabolic rate(oxidize fatty acids rather than converting them to fat
Adipose cells low in fat
-less leptin
-hypothalamus increase in appetite
-decrease in metabolic rate
Ghrelin is a hormone that
-triggers hunger
Leptin is produced by…. And
-adipose and suppresses appetite
-when body fat decreases, leptin levels fall and appetite increases
PYY secreted by…
-small intestine after meals
-suppresses appetite
Where is the lower esophageal sphincter/cardiac sphincter?
Between the esophagus and stomach
Where is the pyloric sphincter ?
Between stomach and small intestine
Where is the ileocecal valve ( sphincter)
Separates small and large intestine
Colostomy bags are attached to a person’s large intestine to collect feces when patients are incapable of expelling it from the anus. A patient suffering from IBD affecting the middle portion of their colon might receive a colostomy bag on which part of the large intestine
A) appendix
B) upper colon
C) cecum
D) rectum
E) ileum
B) upper colon
Which of the following aids the most on the absorption of water soluble products ?
A) pancreatic enzymes
B) enterocyte enzymes
C) intestinal mucosa cells
D) both B and C
E) all of the above
C) intestinal mucosa cells
The agents that help emulsify fats (bile) are produced in
Liver
The highest rate of nutrient absorption occurs in
Small intestine
After ingestion by humans the first category of macromolecules to be chemically digested by enzymes in the mouth is
A) proteins
B) nucleic acids
C) cholesterol and other lipids
D) carbohydrates
E) minerals
D) carbohydrates
