Practical 3 - Digestive Flashcards
What are the 5 functions of the digestive system?
ingestion, digestion, absorption, compaction, and defecation
What is the pathway of digestion?
mouth, salivary glands, esophagus, stomach, liver/gallbladder, pancreas, small intestine, large intestine, rectum/anus
What are the GI tract organs?
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
What are the accessory organs?
teeth, tongue, salivary glands, liver, gall bladder, and pancreas
What are the three salivary glands, and where are they located?
parotid - side of cheek
sublingual - under the tongue
submandibular - below the mandible
Define absorption
uptake of a substance
Define desiccation
removing water
Define secretion
release of a substance
Define mechanical digestion
breakdown of chunks of food into smaller bits of the same food (no molecular alteration)
Define chemical digestion
breakdown of macronutrients by enzymes or acid into smaller molecules
Define ingestion
consumption via mouth
Define mastication
chewing
Define deglutition
swallowing
Define propulsion
pushing or moving forward
Define peristalsis
waves of smooth muscle contraction that causes propulsion
Define defecation
expelling feces (anything that is not broken down or absorbed) from the GI tract
Define churning
method of mechanical breakdown
Define segmentation
mechanical breakdown in intestines, breaking food into segments as well as mixing and moving in both directions
Define bolus
rounded mushy lump of food (esophagus)
Define chyme
liquified food (stomach and small intestines)
Where is feces found?
the colon (large intestine)
How does chyme become mixed together in the small intestine?
peristalsis + segmentation
food/chyme is segmented, peristalsis pushes it forward, then it is segmented again, etc…
each wave of peristalsis has a new set of segments that continually mix the food more and more
What are the layers of the digestive tract from superficial to deep (lumen outwards)? Practice with model photos.
mucosa
-epithelium
-lamina propria
-muscularis mucosae
submucosa
muscularis externa
-inner circular
-outer longitudinal
serosa (or adventitia)
What does the myenteric plexus do? Where is it located?
controls peristalsis and other contraction of the muscularis externa
located in between the layers of the muscularis externa (outside the inner circular layer, but inside the outer longitudinal layer)
What does the submucosal plexus do? Where is it located?
controls the muscularis mucosae and glandular secretions of the mucosa.
located just outside of the muscularis mucosae of the mucosa, right on top of the submucosa
Explain the visceral and parietal peritoneum, as well as retroperitoneal organs (and examples).
parietal peritoneum lines the abdominal cavity, while visceral covers the abdominal organs
retroperitoneal organs lie outside and posterior to the peritoneum, and include the duodenum, part of the pancreas, and portions of the large intestine
What are the 5 peritoneal folds?
mesentery, mesocolon, falciform ligament, greater omentum, and lesser omentum
Where is the mesentery/what does it do? How can it be seen?
holds the small intestine to the posterior abdominal wall
look at the back of the model, it is the pale pink sheet that connects all of the small intestines to the back
Where is the mesocolon/what does it do? How can it be seen?
holds the large intestine to the posterior abdominal wall
seen by looking at the top of the model, connects large intestine to posterior wall (looks like the pancreas on the model)
Where is the falciform ligament/what does it do? How can it be seen?
binds the liver to the anterior abdominal wall
separates the left and right lobe of the liver
Where is the greater omentum/what does it do?
layer of fat that loosely covers the transverse colon and small intestine
Where is the lesser omentum/what does it do?
connects medial curve of the stomach with the liver
What does the upper esophageal sphincter do?
regulate swallowing reflex and keeps excess air out of the esophagus when not in use
What does the lower esophageal sphincter do?
prevents reflex of contents from the stomach
Name the three muscles of the stomach/layers of the muscularis externa from superficial to deep. What is their collective role?
What additional roles does the stomach have?
What is another vital feature of the stomach?
inner oblique muscle
middle circular muscle
outer longitudinal muscle
churn the food in multiple directions
stomach also secretes acid, enzymes, and mucus to liquify the food into chyme
Rugae of mucosa - look wrinkly, allow for expansion, and increase surface area
What structures enter and exit the stomach? What are the other regions of the stomach?
esophagus enters, duodenum exits
cardia, fundus, body, and pyloric antrum + canal
What is the role of the cardia region of the stomach?
interface between the esophagus and stomach (the “entry”)
What is the role of the fundus of the stomach?
holds undigested food and gases released during digestion
What is the role of the body of the stomach?
main portion of the stomach where most churning and digestion takes place
What is the role of the pyloric antrum+canal of the stomach?
holds the broken down food until it is ready to release into the small intestine (duodenum)`
What does the pyloric sphincter do?
keeps contents in the stomach until liquified and regulate a slow release of chyme
What are the 5 types of cells in gastric glands?
What do they each produce?
mucous cells, regenerative stem cells, parietal cells, chief cells, and enteroendocrine cells (G cells)
mucous cells - mucous
parietal cells - HCl
chief cells - pepsinogen and gastric lipase
enteroendocrine - gastrin into the blood stream
Where does most absorption of fluid and nutrients occur?
small intestine
What are the functions of the small intestine?
secretion, mixing, propulsion, segmentation, chemical and mechanical digestion
What are the three regions of the small intestine?
duodenum, jejunum, and ileum
What does the ileal papilla do? What is another name for it?
valve separating the small from the large intestine, keeps bacteria in the large intestine from invading the small intestine
aka the ileocecal sphincter
What are circular folds? Can you see them?
They are folds of mucosa and submucosa that increase the surface area for absorption of nutrients. They are visible to the naked eye.
What three things give the small intestine more surface area?
plicae circularis (circular folds), villi, and microvilli
What is the name for a lymph vessel that runs through a villus?
lacteal
What are the roles of the large intestine?
What are the regions?
absorb remaining water (desiccaton) and segments bolus
cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, and anus
How long does it take for a meal to become feces?
What percent of feces is bacteria?
36-48 hours
30% bacteria
What type of tissue composes the internal and external anal sphincters?
Are they voluntary or involuntary?
internal anal sphincter: smooth muscle, involuntary
external anal sphincter: skeletal muscle, regulates movement of feces, voluntary
Compare and contrast histology slides of stomach, small intestine, and large intestine. What are some key differences?
stomach - flat tops, gastric pits/glands, puffy parietal cells
small intestine - long squiggly villi, intestinal crypts
large intestine - very flat tops, intestinal glands, lots of goblet cells
What are the names of the tissue that connects inferior and superior lips to the gums?
inferior and superior labial frenulum
What is the proper name for the gums?
gingivae
What are the 4 types of teeth and their function?
molars - grind
premolars - crush/grind
canines - tear/shred
incisors - cut
Describe the structures of the tooth and what they do.
enamel
dentin
pulp cavity
cementum - attach the root to the periodontal ligament
periodontal ligament - anchor the tooth to the underlying bone
apical foramen - opening where blood vessels, lymphatic vessels, and nerves enter a tooth
What are the two main types of salivary glands and their location/function?
intrinsic salivary glands (minor) - scattered throughout the mouth, always producing saliva
extrinsic salivary glands (major) - 3 pairs of distinct glands located outside the oral mucosa
What cells can be recognized in the histology of a salivary gland?
duct cells - bright white blobs (form ducts leading to the oral cavity)
secretory cells
- serous/acini cells : look like a blackberry (watery fluid and enzymes)
- mucous cells : groups of pale blobs (mucus)
Of the three extrinsic salivary glands, which has the most duct cells?
sublingual
What composes the hepatic triad?
branch of the hepatic portal vein, branch of the hepatic artery, and a bile ductile
What are the tiny tubes that are all over a liver lobule?
bile canaliculi
What connects the central vein to the edges of the liver lobule?
hepatic sinusoid
What are the cells that make up the majority of a liver lobule, and what do they do?
hepatocytes, make bile
What is the difference in function between the liver and gallbladder?
liver - produce bile
gallbladder - store and concentrate bile
What merges into the common hepatic duct?
right hepatic duct and left hepatic duct
What merges into the common bile duct?
common hepatic duct and cystic duct
What merges at the hepatopancreatic ampulla?
common bile duct and pancreatic duct
Bile dumps into the duodenum through the…
duodenal papilla/hepatopancreatic sphincter
What is liver cirrhosis, and what are the major results of this disease?
scarring of the liver due to long term liver damage
prevents the liver from working properly, leads to end-stage liver disease and liver failure
What are the pathophysiological steps of liver cirrhosis?
previous conditions cause inflammation and death of cells, cell repair leads to a build-up of scar tissue and nodules of regenerating cells, scar tissue obstructs the hepatic circulation and bile passages
What are the two main causes/risk factors of liver cirrhosis?
fatty liver disease and hepatitis infection
How does fatty liver disease cause liver cirrhosis?
general and 2 types
fat accumulation due to nonalcoholic or alcoholic fatty liver disease
NAFLD - range of liver conditions can cause nonalcoholic steatohepatitis (NASH) and cirrhosis
alcohol abuse (AFLD)
What ways can someone get Hep C?
infection spreads through the blood, can be introduced by unprotected sex, sharing needles/razors/toothbrushes, or infected blood transfusions
What are the symptoms of liver cirrhosis?
extreme fatigue and weakness, nausea, weight loss, jaundice, abdominal pain, spider-like blood vessels, vomiting blood, swelling of extremities, bloody stool, itchy skin, and easy bleeding/bruising
What are the treatments for liver cirrhosis?
manage symptoms and slow progression
limit alcohol consumption (even for NAFLD, which is sped up by alcohol)
lose weight if needed
discontinue liver stressing medications
treat initial condition (hepatitis, antiviral meds)
liver transplant if sever (and rarely)
What is the prevalence of liver cirrhosis?
5th-7th leading cause of death in the US ages 25-60
0.27% is affected
10-20% of heavy drinkers develop cirrhosis
15-30% of people with Hep C will develop cirrhosis
NAFLD is most common form of chronic liver disease in the US, 5-12% progress into cirrhosis
Is liver cirrhosis reverseable?
No
What ar ethe functions of the pancreas?
secrete digestive enzymes and bicarbonate into the duodenum through the duodenal papilla
What cells of the pancreas secrete exocrine products?
acini cells
In the pancreas, 1 —— is surrounded by many ——–
pancreatic islet
exocrine/acini cells
What do the alpha and beta cells of the pancreatic islet do?
alpha - glucagon secretion
beta - insulin secretion
What is an enzyme, and how do they work?
they are a protein that has a specific binding site and works at a particular temperature and pH to carry out chemical reactions more quickly
What is the pH in the mouth, stomach, and small intestine?
mouth and small intestine = 7
stomach = 2
What temperature and pH do most enzymes work best at?
37C and pH=7
Does pH or temperature affect enzyme action in digestion more?
pH affects it more than the temperature
What are other terms for starch? What do the molecules look like? How are starches stored in humans and plants?
also called polysaccharides and carbohydrates
they are glucose molecules bent into rings and linked together
stored as glycogen in the liver in humans, but as cellulose in plants
What is a disaccharide, and what are three examples?
two sugar molecules bonded together
sucrose, lactose, maltose
What is sucrose? Where is it found?
glucose and fructose
found in sugarcane
What is lactose? Where is it found?
glucose and galactose
found in yogurt
What is maltose? Where is it found?
2 glucose
found in wheat
What is a monosaccharide, and what are three examples?
sugar molecules small enough to absorb in the GI tract
glucose, fructose, and galactose
What enzyme from the salivary glands breaks down carbohydrates?
What is the substrate, product, and reaction location?
salivary amylase
polysaccharides —> smaller polysaccharides
mouth
What enzyme from the pancreas breaks down carbohydrates?
What is the substrate, product, and reaction location?
pancreatic amylase
smaller polysaccharides —> di/monosaccharides
small intestine
What enzymes in the brush border break down carbohydrates?
What is the substrate, product, and reaction location for each?
a-dextrinase, sucrase, lactase, and maltase
all in the small intestine
a dextrinase: a dextrins to monosaccharides
sucrase: sucrose to glucose and fructose
lactase: lactose to glucose and galactose
maltase: maltose to 2 glucose
What enzyme digests proteins in the stomach?
Where is it produced, what is the substrate and product?
pepsin
produced by chief cells
polypeptides —> smaller polypeptides
What enzymes digest proteins in the small intestine? Where are they produced, and what are their substrates and products?
trypsin/chymotrypsin: pancreas, breaks small polypeptides into dipeptides and amino acids
aminopeptidase: brush border, breaks small polypeptides into amino acids
dipeptidase: brush border, breaks dipeptides into amino acids
What enzymes digest lipids? Where are they produced, where do they react, and what is their substrate and product?
lingual lipase, gastric lipase, and pancreatic lipase all break lipids into glycerol + fatty acids
lingual is released from salivary glands and reacts in stomach
gastric is released from chief cells and reacts in stomach
pancreatic is produced in the pancreas and reacts in the small intestine
What are lingual papillae? What are the four kinds?
structures that contain taste buds
vallate (v shape, big), fungigorm (mushroom, all over), foliate (rectangle, sides), and filiform (cone, just texture)
Describe the vallate papillae.
largest taste bud, form a V on the posterior surface of the tongue
Describe the fungiform papillae.
named for their mushroom shape, found all over the tongue
Describe the foliate papillae.
found on the sides of the tongue
Describe the filiform papillae.
most numerous, small and cone-shaped, sense texture but do not contain taste buds
Describe the structure of a taste bud.
first-order taste neurons on the bottom, layer of basal cells, clustered gustatory receptor cells, taste pore on top with gustatory microvilli
What are the 5 taste sensations?
sweet, salty, umami, sour, and bitter
What is the role of saliva in gustation?
saliva breaks things down into smaller molecules (like glucose and fructose) that can be detected by receptors on the tongue
What is the difference in response strength between olfactory and gustatory neurons?
olfactory respond thousand of times more strongly than gustatory do
Describe the pathway of olfaction.
odorants dissolve in mucus, binds to olfactory receptors/sensory neurons, carried to olfactory bulb
What is a protein? What is a polypeptide?
macromolecule with one or more polypeptides (polypeptides are strings of amino acids)
Protein enzymes break polypeptides into…
dipeptides or amino acids
What are lipids? Lipid enzymes break lipids into…
nonpolar macromolecules consisting of one or more fatty acids bound to a glycerol backbone
break lipids into glycerol and fatty acids
What is the role of bile? Describe the pathway of bile action.
emulsifies lipids by mechanically breaking the oil into small droplets
large lipid droplet enters the intestine
bile emulsifies the drop into smaller particles
lipase (from the pancreas) breaks down the fat into fatty acids and monoglycerides
those molecules are absorbed and reform triglyceride in the villi
triglycerides combine with cholesterol, protein and phospholipids to form chylomicrons which enter the lacteal and travel away in the lymph
What is the pathophysiology of celiac disease?
immune reaction to gluten that triggers T cell immune responses in the small intestine
causes damage and atrophy to the intestinal lining/villi, which in turn decreases surface area and absorption of nutrients
What are the digestive syptoms of celiac disease?
Non-digestive symptoms?
digestive:
diarrhea, fatigue, weight loss, bloating and has, abdominal pain, nausea/vomiting, constipation, lactose intolerance
non digestive:
anemia, loss of bone density, itchy or blister skin rash, mouth ulcers, and joint pain
What can celiac disease lead to if not treated?
heart disease, infertility, liver failure, ADHD, small intestine cancer, other autoimmune disorders
Also affects growth/development in children due to malabsorption
What are the treatments for celiac disease?
no known cure
follow a strict gluten-free diet, vitamin and mineral supplements for vitamin deficiency, medical to control intestinal inflammation, medication to treat dermatitis herpetiformis
no treatments for refractory cell disease
What is refractory celiac disease?
small intestine wont heal itself
What medications can control intestinal inflammation?
steroids, azathioprine, and budesonide
What medications treat dermatitis herpetiformis?
dapsone, sulphapyridine
What is the prevalence of celiac disease?
0.7-1.4% of the population
most in US, Europe, and Australia (3-13 per 1000)
females affected at 2x the rate
incidence increasing 7.5% per year over the past decades
What is the pathophysiology of lactose intolerance?
lactase is not produced in high enough quantity (lactase is what breaks down lactose) so they are unable to digest lactose in milk and break down the constituents
lactose gets to the colon and interacts with normal bacteria causing gas and other symptoms
What are the three causes of lactose intolerance?
primary - start life producing lactase but falls off sharply at some point (compared to others, who slowly lose lactase production as they age)
secondary - illness/injury involving the small intestine
congenital - autosomal recessive disorder, born without lactase and do not develop lactase producing cells
What are the symptoms of lactose intolerance?
symptoms start 30 min-2 hours after food/drink
severity depends on how much lactose is ingested and how much lactase is present
loose stool, diarrhea, abdominal bloating, cramps, pain, flatulence, nausea
What are the treatments for lactose intolerance?
no known treatment to produce lactase
eat low lactose diet (limit milk and dairy, eat dairy with naturally lower or reduced lactose, use lactase enzyme tablets to help break down lactose)
treat the underlying conditions (for secondary type)
What is the prevalence of lactose intolerance?
high levels at birth and decrease with age
nonhuman mammals lose ability to digest lactose during adulthood
Asia, South American, and African areas have a higher propensity for lactase deficiency
Northern European descent and Northwestern Indian subcontinent are more likely to retain ability to absorb lactose as adults
