Digestive system Flashcards
List the five layers of the digestive tract
- Mucosa (inner layer) mucus producing cells
- Submucosal layer
- Circular smooth muscle fibers
- Longitudinal smooth muscle fibers
- The outer layer of the wall comprises the visceral peritoneum or serosa
peritoneum
large serous membrane in the abdominal cavity
The _______________ covers the abdominal wall and the superior surface of the urinary bladder and uterus and then continues to form the __________________
parietal peritoneum
visceral peritoneum
Purpose of the mesentery
The mesentery supports the intestines and conveys blood vessels and nerves to supply the wall of the intestines
greater omentum
The greater omentum is a layer of fatty peritoneum that hangs from the stomach like an apron over the anterior surface of the intestines
lesser omentum
The lesser omentum is part of the peritoneum that suspends the stomach and duodenum from the liver
what happens when inflammation develops in the intestinal wall,
the greater omentum, with its many lymph nodes , tend to adhere to the site , walling off the inflammation and temporarily localizing the source of the problem
Inflammation of the omentum and peritoneum may lead to ___________ and the formation of ________ between structures in the abdominal cavity which may lead to obstruction
scar tissue
adhesions
The _______________ are located posterior to the stomach against the abdominal wall and behind the parietal peritoneum
kidneys and pancreas
What is unique about the kidneys and pancreas which makes them retroperitoneal organs
They are covered with peritoneum only on the anterior surface and are therefore referred to as retroperitoneal organs
Where does saliva come from?
from parotid, sublingual and submandibular glands
amylase
enzyme from saliva which begins the digestion of CHO
When food is ready to be swallowed, the tongue pushes the Bolus or ball of food back into the pharyngeal wall. Receptors of the __________________________ nerves relay the information to the swallowing center in the medulla
trigeminal and glossopharyngeal
describe the sequence of events in the swallowing reflex
- The soft palate is pulled upward –
- The vocal cords are approximated –
- The epiglottis covers the larynx –
- Respiration ceases –
- The bolus is seized by the constricted pharynx –
- As the bolus of food moves into the esophagus, distending the wall, peristalsis is activated pushing the food down –
- The lower esophageal sphincter relaxes allowing it to drop into the stomach
what normally prevents reflux of gastric contents
The pressure in the sphincter normally prevents reflux of gastric contents back up the esophagus
parietal cells that secrete
HCl
chief cells that secrete
pepsinogen (converted to pepsin by HCl)
Secretions from the liver and pancreas are added to the chyme, where?
duodenum
glycogenolysis
Glycogen to glucose
gluconeogenesis
Converts protein and fat to glucose
With the help of ___________, the liver produces proteins that are important in blood clotting
vitamin K
A toxic substance called ammonia is a by-product of changing amino acids in foods so that they can be used to produce energy. •The liver cells convert ammonia to a much less toxic substance called _____, which is released into the blood
urea
After urea is released from the liver into the blood, how is it next metabolized?
Urea is then transported to the kidneys and passes out of the body in urine
Liver tissue is made up of lots of smaller units of liver cells called ___________
lobules
Blood coming from the digestive organs flows through the____________ to the liver, carrying nutrients, medication and also toxic substances
portal vein
Blood coming from the digestive organs flows through the portal vein to the liver, carrying nutrients, medication and also toxic substances. Once they reach the liver, what happens next?
these substances are processed, stored, altered, detoxified, and passed back into the blood or released in the bowel to be eliminated
the pancreas contains 2 basic types of tissue:
Acini- produces digestive enzymes
Islets- produces hormones
Acini produces:
- Amylase- carbohydrates
- Lipase- fats
- Trypsin- proteins
Islets produces:
- Insulin- lowers level of blood glucose
- Glucagon- raises level of blood glucose
- Somatostatin- regulates
the small intestine has 3 sections, list them
- Duodenum –
- Jejunum –
- Ileum
peristalsis
The contents move slowly along the tube, influenced by both mixing and propulsive movements of the wall
The duodenum contains Brunner’s glands which produce
bicarbonate. In combination with bicarbonate from pancreatic juice, this neutralizes HCl of the stomach
plicae circulares
Small intestines transverse folds of the mucosa covered with villi and microvilli
what is the advantage of plicae circlares
These numerous tiny projections greatly increase the absorptive surface area of the small intestine
__________ in the mucosa secrete large quantities of mucus into the intestine to protect the intestinal wall and buffer the acid chyme
Goblet cells
The __________ marks the entry point from the ileum into the large intestine or colon
ileocecal valve
Absorption of what happens in the colon
Absorption of large amounts of water and electrolytes takes place in the colon
Absorption of large amounts of water and electrolytes takes place in the colon. This “recycling” process is of critical importance, for what?
in maintaining the fluid and acid-base balances in the body
where is bilirubin converted to urobilinogen?
by resident bacteria in Lg Int.
where would one find Peyer’s patches and what are they for?
The ileum have Peyer’s patches (lymphoid tissue) which limit the spread of these bacteria to the small intestine
The rectum stores the solid feces until sufficient distention of the rectal wall stimulates the defecation reflex. Describe the sequence of events
- 1Sensory nerve impulse (from the stretch receptors) are transmitted to the sacral cord
- PNS transmit motor impulses and relax the anal sphincter
- Pelvic muscles contract and voluntary relaxation of the external sphincter allows defecation to occur
- Elimination of feces can be assisted by increasing intra-abdominal pressure through contraction of abdominal muscles and the diaphragm
- If, under voluntary control, the external sphincter remains closed, the defecation reflex subsides temporarily
When the PNS is stimulated, how does this affect digestion?
Stimulation of the parasympathetic nervous system (PNS) results in increased motility (peristalsis) and increased secretions in the digestive system. “Rest and digest”
When the SNS is stimulated, how does this affect digestion?
it inhibits gastrointestinal activity (“fight or flight”)
_________ is secreted by mucosal cells in the pyloric antrum in response to distention of the stomach
Gastrin
how does gastrin work?
- Gastrin is secreted by mucosal cells in the pyloric antrum in response to distention of the stomach •
- Gastrin enters the blood and circulates, the returns to stimulate the gastric cells to increase secretions, increase gastric motility and relax the pyloric and iliocecal sphincters thus promoting stomach emptying
•When chyme enters the duodenum, mucosal cells release the hormones ________________
secretin and cholecystokinin
secretin
Secretin decreases gastric secretions and increases the bicarbonate ion content of pancreatic secretions and bile when the chyme is highly acidic
cholecystokinin CCK
•CCK inhibits gastric emptying, stimulates pancreatic secretions and stimulates contraction of the gallbladder to increase bile flow into the duodenum
Where are carbohydrates digested?
•Carbohydrates (starches) are first digested in the mouth and then in the intestine
Where are carbohydrates absorbed?
•They are broken down by enzymes into simple sugars (monosaccharides) that are absorbed in the jejunum and ileum
where are proteins broken down
•Proteins are first split into peptides (short chains of amino acid) in the stomach and intestine and then further broken down by peptidases into amino acid
•_______________ chops up lipid molecules into fatty acid molecules and glycerol molecules
Pancreatic lipase
