exam 1 digestive Flashcards
What are the 2 main groups of the digestive system?
gastrointestinal tract & accessory digestive organs
What is the GI tract?
a continuous tube from mouth to anus with food passing through its lumen (hollow center)
What are accessory digestive organs?
they participate in the digestive process but are not tubular (don’t have food passing through them)
What are the tissue layers that make up the entire GI tract (from deep to superficial)?
mucosa, submucosa, muscularis, & covering
What is the mucosa?
layer of mucous epithelium that lines the tract; the mucous produced by goblet cells protects this lining
What are the 3 parts of the mucosa?
mucous epithelium, lamina propria, & muscularis mucosa
What is the mucous epithelium?
deepest part of the mucosa; faces lumen
What is the lamina propria?
thin layer of connective tissue
What is the muscularis mucosa?
thin layer of smooth muscle; contracts to create ridges & folds in the mucosa
What is the submucosa?
thick layer of connective tissue containing blood vessels, glands, and nerves
What is the submucosal plexus?
formed by the nerves of the submucosa; controls the muscularis mucosa
What is the muscularis?
smooth muscle layers that contract to push food through the lumen of the GI tract; this is called peristalsis
What is the myenteric plexus?
embedded in the muscularis nerves; it is controlled by the ANS & allows for peristalsis; sympathetic stimulation slows this activity & parasympathetic stimulation speeds it up
What is the covering?
the outermost layer of the GI tract; 2 types which are serosa & adventitia
What is serosa?
thin moist serous membrane called peritoneum; it is folded into 2 surfaces which are parietal & visceral peritoneum
What is parietal peritoneum?
lines the walls of the abdominopelvic cavity
What is the visceral peritoneum?
adheres onto organs
What is inside the space between the parietal & visceral peritoneum?
serous fluid that provides lubrication and decreases friction as we move
What is adventitia?
tough connective tissue covering that binds/holds specific organs & nearby blood vessels in place
What organs are covered in adventitia?
pharynx, esophagus, rectum, & anal canal
What is the anterior boundary of the mouth cavity?
the labia which are the lips; they are covered in non-keratinized stratified epithelium which makes them more prone to chapping/sunburn
What is the red margin?
outer part of the lips; it is a deeper color due to visible blood vessels
What is the labial frenulum?
slender strand of mucous membrane that holds the lips to the gingivae (gums)
What is the superior boundary of the mouth cavity?
the roof of the mouth which is made of the hard & soft palates
What is the hard palate?
made of palatine bones & palatine processes
What is the soft palate?
all muscle with no bony support; the most posterior part of the mouth cavity; ends at the uvula; these muscles push bolus (food) into the pharynx
What is the inferior boundary of the mouth cavity?
the floor of the mouth which holds the tongue
What is the lingual frenulum?
slender strand of mucous membrane that anchors the tongue; looks blue due to a deep blood vessel called the deep lingual vein
What is the posterior boundary of the mouth cavity?
fauces; this is the hole where bolus (food) passes into the pharynx
What is the oral vestibule?
space between the cheeks & gums and between the lips & gums
What is the esophagus?
10 inch long muscular tube that connects the oropharynx to the stomach; lined with stratified epithelium for protection
What is unique about the muscularis layer of the esophagus?
it has regions of smooth & skeletal muscle; superior 1/3 is skeletal, middle 1/3 is a combo, & inferior 1/3 is smooth controlled entirely by the ANS
Where is the esophagus located?
posterior to the trachea; it passes through the diaphragm at a hole called the esophageal hiatus
What is the cardiac sphincter?
surrounds the esophageal hiatus; it opens/closes the esophagus appropriately; the esophagus remains closed unless we are actively swallowing & then it moves bolus using peristalsis
What is the stomach?
J-shaped pouch for food that lies slightly left from the center & is inferior to the diaphragm; it can stretch to hold lots of food
What are rugae?
ridges folded into the stomach’s mucosal lining that are covered in mucous with lots of goblet cells; between these are grooves called gastric pits which contain secretory cells
What secretory cells are contained in the gastric pits?
chief cells, parietal cells, & enteroendocrine cells
What are chief cells?
secrete pepsinogen (an inactive molecule) that is converted into an active form called pepsin which begins protein digestion
What are parietal cells?
secrete hydrochloric acid which keeps stomach pH at approximately 1.5
What does hydrochloric acid do?
it denatures proteins by breaking the hydrogen bonds, kills most bacteria, & changes pepsinogen into pepsin
What is intrinsic factor?
produced by parietal cells; promotes absorption of vitamin B12
What are enteroendocrine cells?
produce a variety of hormones such as ghrelin & gastrin
What is ghrelin?
causes hunger
What is gastrin?
secreted as the stomach enlarges & stomach pH increases; it stimulates chief cells & parietal cells; increases peristalsis activity
What is a chyme?
name for the “food” that is passing out of the stomach; it exits the stomach through the pyloric sphincter valve & enters the small intestine
What is absorbed by the stomach?
a little water, aspirin, & alcohol
Why are rugae covered in mucous?
to protect the stomach from its own acids
What is the small intestine?
20 ft long tube with 1 inch diameter; highly folded with constant muscle tone to make it fit in the abdominopelvic cavity
What are enterocytes?
cube-shaped cells that make up the mucosal lining of the small intestine which is folded into visible ridges called plicae circularis
Why are the plicae circularis important?
they allow the chyme to travel through the small intestine in a spiral-like fashion like a ramp instead of falling straight through
What are villi?
finger-like projections that cover each plicae circularis fold
What can be found inside each villus?
an arteriole, venule, & lacteal
What is an arteriole?
a small artery that delivers oxygenated blood to enterocytes to keep them alive
What is a venule?
a small vein that absorbs nutrients from the lumen & picks up CO2 from enterocytes (inside this vein is nutrient rich, O2 poor blood)
What is a lacteal?
a small lymph vessel that absorbs specific fats
What are intestinal crypts?
depressions in between the villi of the plicae circularis; they are the source of new enterocytes
What does the small intestine absorb?
90% of all of our nutrients
What is the large intestine?
3 inch diameter & 12 foot long; held in place by connective tissue
What is the ileocecal valve?
a hole where the large intestine opens from the small intestine
What are haustra?
pouches formed in the length of the large intestine due to the constant action of smooth muscle ribbons
What are the functions of the large intestine?
prepares chyme for elimination, absorbs some water, & houses beneficial bacteria that ferment undigested carbs in chyme & produces vitamins K + B
What is the anal sphincter?
surrounds the anal canal that passes through the inferior body wall & is where the large intestine ends
What are teeth?
there are 2 sets: deciduous/baby teeth (20 total) & permanent teeth (32 total including wisdom teeth/3rd molars); they come in various shapes to allow a varied diet
What are the salivary glands?
produce saliva; 3 pairs = parotid, submandibular, & sublingual
What is the parotid salivary gland pair?
anterior & inferior to the ears, covering the masseter
What is Stetson’s duct?
an opening where saliva enters the mouth near the 2nd molar by piercing cheek mucosa
Where is the submandibular salivary gland pair?
inferior to the mandible
Where is the sublingual salivary gland pair?
under the tongue
What are the functions of saliva?
washes teeth, starts starch digestion (amylase), moistens food so it is easier to swallow, & allows us to taste food
What is the liver?
3 pound organ that lies inferior to the diaphragm on the right side of the body; has over 500 functions
What color is the liver?
red/brown due to abundant blood vessels inside
What is the falciform ligament?
a fibrous cord that divides the liver into left & right lobes
What other lobes does the liver have?
the inferior surface of the right lobe is subdivided into quadrate & caudate lobes
What is the portal vein?
contains nutrient-rich, oxygen-poor, “dirty” blood that was absorbed by the villi of the small intestine & enters the inferior surface of the liver through this vein
What does the liver do with the “dirty” blood that enters through the portal vein?
filters out cell fragments, pieces of bacteria, drugs such as tylenol, & alcohol to detoxify the blood
What does the liver manufacture?
cholesterol; this is essential in cell membranes
What does the liver do to ammonia that comes from protein digestion?
it converts it into a less toxic form that is then removed from the blood by the kidneys
What is bilirubin?
a pigment that the liver removes from the hemoglobin of old, worn out red blood cells; it is yellow/brown colored molecule that is disposed of in feces
What is albumin?
a protein made by the liver that regulates the osmotic pressure of blood to prevent swelling
What is bile?
a green liquid made by the liver (secreted by hepatocytes) that breaks big pieces of fat into smaller ones that are more easily digested by enzymes
What is glycogen?
an excess sugar that is given short-term storage in the liver & will be converted to fat if it is not used quickly
What are hepatocytes?
cube-shaped cells arranged in rows in hexagonal units; these make up the liver
What are liver sinusoids?
spaces in between plates of hepatocytes where branches of the portal vein run
How do hepatocytes continually adjust the fluids in the liver sinusoids?
the nature of the blood vessel structure in the liver sinusoids
What are fenestrated capillaries?
the type of blood vessel that is the tiny branches of the portal vein; they have large gaps between the cells in their walls allowing materials to flow into/out of them with ease
What are bile ductules?
tiny ducts crisscrossing the blood vessels; they carry bile & eventually form the left & right hepatic ducts that exit the liver
What are Kupffer cells?
phagocytic cells found in the liver that engulf potential pathogens & debris; they store iron, heavy metals such as mercury, & some lipids
What is the gallbladder?
small pear-shaped sack located on the liver’s inferior surface in a shallow depression called the hepatic fossa
What is the gallbladder’s function?
storing & concentrating bile
What is the common hepatic duct?
the gallbladder receives bile from the liver’s left & right hepatic ducts which merge to create this
What is the cystic duct?
where bile from the common hepatic duct is pulled into in the gallbladdder; remains there until needed & it becomes concentrated while there
What is CCK (cholecystokinin)?
a hormone that is released when fats are detected in the duodenum of the small intestine; it triggers peristalsis of the gallbladder’s ducts, releasing bile into the cystic duct
What is the common bile duct?
formed from the cystic duct & common hepatic duct merging; drains bile from both the liver & gallbladder & empties it into the duodenum
What is the duct system throughout the gallbladder called?
the biliary system
What is the pancreas?
soft oval gland located posterior to the stomach’s greater curvature
What are the 2 main functions of the pancreas?
produce 1-2 quarts of pancreatic juice per day & produce hormones that regulate metabolic processes
What is pancreatic juice?
the main digestive fluid that flows into the duodenum; produced by groups of cells called pancreatic acini
What does pancreatic juice do?
it’s full of a variety of enzymes that break down very specific components of the foods we ingest; has a pH of 7.1-8.2 which helps neutralize the acidic chyme that flows into the duodenum from the stomach
What is pancreatic lipase?
breaks down certain lipids/fats
What is nucleases?
breaks down DNA or RNA
What is pancreatic amylase?
breaks down certain starches
What are proteolytic enzymes?
break down proteins when activated in the small intestine
What are pancreatic islets?
cells scattered among the pancreatic acini; they only account for 1% of the pancreas cells but their secretions are vital to survival
What are alpha cells?
produce glucagon which raises blood glucose levels by increasing the rate of glucose released by the liver
What are beta cells?
produce insulin which lowers blood glucose levels by increasing the rate at which cells take & use glucose
What are the 3 structures that serve to hold our organs, vital blood vessels, & nerves in place in the abdominopelvic cavity?
greater omentum, lesser omentum, & mesentary
What is the greater omentum?
an apron-like arrangement of peritoneum that drapes over the transverse colon & the folds of the small intestine
What does the greater omentum contain?
a variety of blood vessels, lymphatic vessels, & nerves that supply the abdominal organs; richly supplied with fat
What is beneficial about the lymph nodes of the greater omentum?
there is an abundance of them & they contain specific white blood cells that help fight infections of the GI tract
Why is it important that the greater omentum has lots of fat?
it is a source of energy storage & also protects our GI organs by cushioning them to prevent injury
The amount of fat in the greater omentum varies among individuals, but how does it look under normal circumstances?
the fat gives the greater omentum a pale yellow lacy appearance; in healthier individuals, the amount & opaqueness of the fat increases
What is the lesser omentum?
a double layer of peritoneum that anchors the lesser curvature of the stomach to the liver & duodenum to hold these organs in place
What is the mesentary?
a double fold of peritoneum that attaches the intestines to the posterior body wall
What does the mesentary contain?
abundant blood vessels & nerves; richly supplied with lymph nodes to prevent infection
