Digestion Part 2
Myenteric Plexus
Activated by the other plexus. Triggers contractions of the muscularis. Embedded between the longitudinal and circular muscle layers.
Disaccharides are an example of which of the following macromolecules?
Carbohydrate
Place the structures of the large intestine in the correct order of flow of waste product beginning nearest to the small intestine towards the rectum.
Cecum Ascending Colon Right Colic Flexure Transverse Colon Left Colic Flexure Descending Colon Sigmoid Colon
Gallstones
Due to a mass of cholesterol, calcium carbonate, and bilirubin Manifestations include jaundice of skin, excessive amounts of fat in stool, and abdominal pain from inflammation in the pancreas. Treatment includes the removal of the gallbladder.
Bile from the liver and digestive juices from the pancreas enter which section of the small intestine?
Duodenum
Ileum
Final region of the small intestine Attaches to the large intestine Absorption of vitamin B12
Duodenum
First region of the small intestine Neutralization of acid Receives chyme, pancreatic juice, and bile Emulsification of lipids
The functions of the large intestine, rectum, and anal canal include:
Haustral churning, peristalsis, and mass peristalsis to drive contents of the colon into the rectum Utilize bacteria in the colon to convert proteins into amino acids, break down amino acids, and produce B vitamins and vitamin K Absorption of some water, ions, and vitamins Formation of feces Defecation
Secretin is released from the duodenum in response to _________.
Hydrochloric acid in chyme
Submucosal Plexus
Initially triggered by distension of the walls of the GI tract. Responsible for activating the other plexus. Triggers secretions within the mucosa.
Normal bacterial flora in the large intestine are responsible for the production of vitamins B and ___.
K
Lipid digestion:stomach
Lingual lipase: produced in the oral cavity via intrinsic salivary glands and will begin the process of digesting triglycerides. Gastric lipase: produced by chief cells in the stomach and will work with lingual lipase to digest triglycerides.
Lipid digestion:oral
Lingual lipase: though it is produced by the lingual glands of the oral cavity, it will not begin chemical digestion until it reaches the stomach.
The act of protein digestion begins in the mouth with ___________digestion. Once in the stomach, ________ hydrolyzes peptide bonds. In the small intestine, trypsin, chymotrypsin, and ______________ continue the breakdown of proteins. The_________ border in the intestines finishes the breakdown and absorption begins.
Mechanical Pepsin carboxypeptidase Brush
Jejunum
Middle region of the small intestine Majority of digestion and absorption Found in the upper left quadrant of the abdominal cavity
General functions of small intestine
Mixing chime with digestive juices and bringing food into contact with mucosa for absorption; peristalsis propels chime through small intestine. Completion of digestion of carbohydrates, proteins, lipids; begins and completes digestion of nucleic acids. Absorption of about 90% of nutrients and water that pass through the digestive system.
Peptic Ulcers
Most cases are due to the presence of Helicobacter pylori. Higher risk in patients that constantly take aspirin or other NSAIDS. Treatment includes bismuth suspensions such as Pepto-Bismol.
Which of the following is a feature that both the stomach and the small intestine have in common?
Mucus-secreting cells
Which of the following body systems would be affected by disfunction of the liver?
Muscular, endocrine, cardiovascular, integument.
Carbohydrate digestion: small intestine
Pancreatic amylase: produced in the pancreas that will convert partially digested starches into oligosaccharides, maltose, and glucose. Brush border enzymes:Maltase - converts maltose to glucoseLactase - converts lactose into glucose and galactoseSucrose - converts sucrose into glucose and lactose
Nucleic acid digestion: small intestine
Pancreatic enzymes:Deoxyribonuclease (DNAse) - breaks down DNARibonuclease (RNAse) - breaks down RNA Brush border enzymes:Phosphatase - converts nucleotides into nucleosides and phosphate.Nucleosidase - converts nucleosides into nitrogenous bases and a pentose (deoxyribose or ribose)
Protein digestion: small intestine
Pancreatic enzymes:Trypsin - converts proteins into polypeptides and peptide fragments.Chymotrypsin - converts proteins into polypeptide and peptide fragmentsCarboxypeptidase - converts proteins into amino acids. Brush border enzymes:Dipeptidase - converts dipeptides into amino acids.Aminopeptidase - converts proteins into amino acids.
Lipid digestion:small intestine
Pancreatic lipase: produced in the pancreas that will convert triglycerides into monoglycerides and fatty acids.
Protein digestion:stomach
Pepsin: active form of pepsinogen produced by the chief cells and activated by hydrochloric acid produced by the parietal cells. Pepsin will begin the process of denaturing proteins into amino acids.
Which of the following is a method of motility in the small intestine? (Select all that apply)
Perstalils segmentation
Which of the following regions of the large intestine is a muscular tube that expands to store accumulated material prior to defecation and terminates at the anal canal?
Rectum
Carbohydrate digestion:stomach
Salivary amylase - produced in the oral cavity and will only work for approximately 15-20 minutes in the stomach before it is denatured.
Carbohydrate digestion:oral
Salivary amylase: produced by the salivary glands and will cleave the bonds between glucose molecules within starches.
Gastrin
Stimulated by distension of the stomach, changes to pH of gastric juices, and presence of proteins and caffeine. Promotes gastric juice secretion, gastric motility, and gastric cell proliferation. Closes the lower esophageal sphincter and relaxes the pyloric sphincter.
Ghrelin
Stimulated by the cephalic phase of digestion and increased near normal mealtimes. Triggers the feeling of hunger.
Secretin
Stimulated by the presence of acidic chyme in the small intestine. Promotes secretion of pancreatic juice and bile rich in bicarbonate ions to neutralize pH. Inhibits secretion of gastric juices, promotes growth of the pancreas, and enhances effects of CCK.
Cholecystokinin (CCK)
Stimulated by the presence of amino acids, triglycerides, and fatty acids in the small intestine. Stimulates secretion of pancreatic juice rich in digestive enzymes, causes bile ejection from the gallbladder, opening of the hepatopancreatic ampulla, induces satiety. Inhibits gastric emptying, promotes growth of the pancreas, and enhances the effects of secretin.
Leptin
Stimulated by the presence of insulin. Signals the hypothalamus to limit food intake. Triggers the feeling of satiety.
colorectal cancer
Testing consists of sigmoidoscopy and colonoscopy. Testing should begin at age 50. Increased risk for smokers, sedimentary individuals, and alcohol drinkers
Why is the colon referred to as the large intestine?
The diameter of the colon is larger than that of the small intestine
Which of the following might stimulate the cephalic phase of gastric secretion?
The thought of food
Chron's disease
Typically diagnosed before the age of 30. Thought to be caused by a mixture of genetic markers and viruses. Manifestations include bloody stool, arthritis, and abdominal pain.
duodenum
a 25 cm long tube that begins at the pyloric sphincter and encircles the head of the pancreas. It will receive the stomach contents, pancreatic juice, and bile. While here, the stomach acid is neutralized, fats are emulsified by bile, pepsin is inactivated, and chemical digestion is carried out by the pancreatic enzymes.
intrinsic defecation reflex
a local reflex, is mediated by the myenteric plexus. The stretch receptors send their signals to the muscularis of the descending colon, sigmoid colon, and the rectum, activating peristatic waves that drive feces downward and relaxes the internal anal sphincter.
Micelles
are responsible for moving the fat droplets from the lumen of the small intestine into the enterocytes (absorptive cells).
duodenal (Brunner's) glands
are responsible for secreting alkaline fluids to neutralize stomach acid pH and mucus to protect and lubricate the duodenum.
chylomicrons
can be transported into the lymph.
A 54-year-old male presents with abdominal pain and blood in his stool. He states that he has been drinking Pepto-Bismol and it has not been effective. He has never had a colonoscopy or sigmoidoscopy. Which of the follow digestive disorders is the likely cause?
colorectal cancer
indigenous microbiota
consists of the bacterial flora that thrive within the large intestine. These bacteria are required to breakdown some of the more complex carbohydrates, proteins, and lipids of the chyme that were not digested in the previous organs.
gastric phase
digestion will begin when food activates stretch and chemoreceptors in the stomach, activating the myenteric and vagovagal reflexes. This will cause gastric secretions to increase via a mixture of the reflexes and the presence of histamine and gastrin.
intestinal phase
digestion will begin when food activates the stretch and chemoreceptors in the stomach. This will trigger the release of secretin and CCK and activate the enterogastric reflex in order to inhibit gastric secretion and motility. Sympathetic innervation will suppress the parasympathetic stimulation of the stomach.
Fructose -
facilitated diffusion
Which of the following hormones are the primary regulators of digestion.
gastrin,, secretin, CCK
parasympathetic reflex
is a spinal reflex that will take longer than the intrinsic defecation reflex, but it will result in stronger signals. The stretch receptors, in this case, send their signals to the spinal cord. Motor pelvic nerves will intensify peristalsis in the descending colon, sigmoid colon, and rectum while relaxing the internal anal sphincter.
Sodium
is absorbed alongside sugars and amino acids.
Calcium
is absorbed through calcium channels when parathyroid hormone is present.
Phosphate
is absorbed via active transport
Potassium
is absorbed via simple diffusion
Chloride
is actively transported in the ileum via an antiporter pump that exchanges it for bicarbonate ions.
The peristaltic movement of colonic contents rapidly towards the rectum approximately 1-3 times per day is called __________.
mass movement
Digested triglycerides are contained within the ___________ prior to being transported across the simple columnar epithelial lining of the small intestine into the epithelial cells.
micelles
Carbohydrates Fats Proteins Nucleic acid
monosaccharides monoglycerides and fatty acids amino acids nucleotides
Peyer's patches
mucosa-associated lymphatic tissues (MALT) found in the ileum of the small intestine to respond to pathogens.
Protein digestion: oral
none
nucleic acid digestion: oral
none
nucleic acid digestion:stomach
none
cephalic phase
of digestion begins with the thought, smell, or sight of food. This will stimulate gastric secretion and motility prior to ingestion and deglutition.
The ____________ is a mixed gland with endocrine and exocrine functions that produces the majority of the digestive enzymes.
pancreas
Defecation is stimulated by _____________.
parasympathetic and local reflexes
Which of the following enzymes is produced by the stomach?
pepsin
Villi:
projections that extend into the lumen and contain absorptive cells and goblet cells which protect the underlying tissues from digestive enzymes.
Emulsification
refers to the process by which large lipid droplets are converted into smaller lipid droplets and giving them polarity. This process serves to increase surface area and give polarity to the fat droplet so that proper enzymatic attachment can occur and thereby facilitate lipid digestion.
Iron
requires hormonal regulation for its absorption via hepcidin produced by the liver. Hepcidin will only be released with levels of iron in the liver fall.
intestinal glands
responsible for secreting intestinal juice to assist in absorption and have a diverse array of specialized cells. The absorptive cells digest and absorb nutrients. The goblet cells secrete mucus. The enteroendocrine cells secrete the hormones secretin (S) and cholecystokinin (CCK). Finally, the Paneth cells secrete lysozymes.
Digestive reflexes that do not involve the central nervous system but instead are localized and only occur within the enteric nervous system are called ___________ reflexes.
short
jejunum
significantly longer than the duodenum, measuring at a length of between 1.0 and 1.7 meters that begins in the upper left quadrant of the abdomen and lies primarily in the umbilical region. The majority of digestion and nutrient absorption occurs here.
During digestion, the major site of nutrient absorption is the _____________.
small intestine
Microvilli:
smaller projections that secrete brush border enzymes int the lumen of the small intestine in order to aid in digestion.
Glucose -
sodium-glucose symporters
A friend tells you that he has been diagnosed with a peptic ulcer. Which of the following do you advise him to do? (Select all that apply.)
stop smoking, take pepto bismol, take an antibiotic
ileum
the final segment of the small intestine, measuring at 1.6 to 2.7 meters in length and occupies the hypogastric region of the abdomen and will meet the large intestine at the ileocecal junction. It is responsible for the absorption of vitamin B12 and bile salts.
Circular folds:
transverse spiral ridges within the mucosa and submucosa to provide greater surface area for thorough mixing and nutrient absorption.
Which of the following is inhibited by the sympathetic nervous system? (Select all that apply.)
urination, salivation, digestion, defecation, absorption
long (vagovagal) reflexes
will be triggered with the activation of sensory autonomic nerve fibers that send signals to the brainstem. Branches of the vagus nerves will stimulate digestive motility.
short (myenteric) reflexes
will be triggered with the activation of stretch or chemoreceptors in the digestive tract that will send signals to the myenteric plexus in order to stimulate contraction of the muscularis layers.
