Gastrointestinal System Flashcards
What are the two main structures of the digestive system?
- alimentary canal aka GI tract- tube that starts at the mouth and ends at anus [ peristalsis occurs here]
- accessory organs- secretes items to aid in digestion
What are the accessory organs?
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
What are the main structures of the GI tract?
- mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, illeum), large intestines (appendix, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal)
What is a function of the appendix
immune function (has good bacteria)
What is the function of the rectum?
temporarily stores feces
What are the functions of the digestive system?
- ingest, digest, absorb (nutrients like amino acids or glucose are absorbed into the bloodstream) food and eliminate the undigested food remains as feces
What are the two types of digestion done by the GI tract.
- mechanical digestion
- chemical digestion
Explain mechnical digestion
Name examples of mechanical digestion
- physical breakdown of food into smaller particles to aid in chemical digestion; NO chemical rxn
- examples: chewing and grinding in the mouth; churning and mixing in the stomach
Explain chemical digestion
Name examples of chemical digestion
- done by enzymes and acid; chemical rxn present (changes one substance into another)
- example: starch broken down into glucose; proteins broken down into AA; fats, lipids broken down into fatty acids and glycerol
Rest and digest is done by which arm of the nervous system?
parasympathetic
General pathway of food travel from the mouth to the anus
- mouth- teeth, tongue, salivary glands
- pharynx
- esophagus
- LES
- stomach
- pyloric sphincter
- small intestines- duodenum, jejunum, ileum
- large intestine- appendix, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal
Where does mechnical digestion begin?
teeth of the mouth
Where is the first area of chemical digestion?
-
mouth, more specifically, the
saliva from salivary glands that contains amylase to digest starch, amylose
Where is the first site of protein digestion?
stomach
through pepsin released by chief cells
Where is most of the chemical digestion and absorption done?
chemical digestion: duodenum of the small intestines
absorption: proximal jejunum is the most, and then duodenum
What nerve does sensory control to the top teeth? bottom teeth?
CN 5 (trigeminal) -
* top teeth: maxillary branch
* bottom teeth: mandibular branch
tongue
- What type of muscle is the tongue?
- What is the function?
- What nerve does motor control?
- skeletal
- mixes the food with saliva
- CN 12 (hypoglossal)
Where is the food bolus made?
by the teeth, tongue, and salivary glands of the mouth
What is present in the saliva made by salivary glands?
amylase, which digests starches (a complex carb) into simple sugars AS WELL AS lipase
What are the 3 salivary glands? What nerves control them? What branch of the NS do those nerves belong to?
- parotid- CN9 (glossopharyngeal- parasympathetic)
- sublingual- CN 7 (facial- parasympathetic)
- submandibular- CN 7 (facial- parasympathetic)
What type of muscle is the esophagus? Explain the movements through it.
- smooth muscle
- when the m. contracts, it does peristalsis to push food bolus down.
What are the 2 important sphincters of the GI tract? What are the general functions of each?
- LES- closes to prevent food from going back up the esophagus
- Pyloric- closes to prevent food from leaving the stomach early before it is fully mixed up as chyme
Two pathological states of LES
- too tight- achalasia: food harder time to enter stomach and so pt loses weight bc not able to eat as much food
- too relaxed- GERD: food (acidic) goes up esophagus due to hormone (ie. relaxin from pregnancy) or mechanical (ie. preggo and large belly or overweight) or other reasons.
What is the function of the stomach?
- mechanical and chemical digestion
- copiouos amount of mechnical digestion are accomplished through it having 3 layers; it mixes and churns food and turns it into chyme.
- chemical digestion: pepsin in stomach to breakdown proteins
Where is food turned into chyme?
stomach. through its mixing and churning action of food and combining it with digestive juices
What are the functions of the liver?
- produces and secretes bile, which can be temp stored in the gallbladder or released through the common bile duct directly into the duodenum after a meal
- processes nutrients (carbs, proteins) from the blood through input from the Hepatic portal vein (from gut) and Hepatic Artery (from aorta)- takes the amino acids from nutrient absorption it needs and then distributes the rest
- blood sugar (glucose) regulator- stores excess glucose as glyogen (glycogenesis) or even fat (lipogenesis) after carb meal ingestion and digestion OR if sense low blood glucose, does breakdown of glycogen into glucose (glycogenolysis), lipolysis, or gluconeogenesis (from AA or glycerol) [ keeps blood glucose at arond 100 mg/dL]
- detoxification (ie. enzymes to breakdown alcohol and drugs)- so removes waste from blood like kidney and spleen
- deamination- removes amino group (NH2) from amino acids, which turn it into ammonia (NH3), which is TOXIC, so liver enzymes convert it into urea, which is NON-toxic, and is taken up by the kidney’s to be excreted in the urine.
- makes plasma proteins: albumin-holds water in blood vessels to maintain BP, transferin- transports Fe stored in liver to bone marrow to be incorporated into developing RBC’s, clotting factors (including fibrinogen)- to prevent bleeding out, complement to fight off infections
- stores fat soluble vitamins A, D, E, and K.
- conjugates bilirubin, which is a breakdown product of RBC (spleen also does old RBC removal)
glycogen is a polysaccharide equivalent to plant starch
hepcidin made in the liver INHIBITS iron absorption bc too much iron leads to liver, spleen, and joint issues.
What substances are released into the duodenum to aid in chemical digestion? Where do those things come from and how do they get to duodenum?
- pancreatic- amylase, trypsin, lipase via pancreatic duct to duodenum
- liver- bile via common bile duct to the duodenum or stored bile from gallbladder
- both those ducts meet at ampulla of vater to get into duodenum and release of contents are controlled by the sphincter of Oddi.
What is the function of bile?
- the bile salts part of the bile aids in lipid digestion: helps the lipids better dissolve in water by emulsifying - make hydrophobic substance water soluble- them into fat droplets aka micelles- so that pancreatic lipases, which are water soluble, can act on the fat droplets and turn them into fatty acids and glycerol.
- enhances absorption of fat soluble vitamins (A, D, E, K)- rlly these vit only absorb well when present in fatty food and NOT fat free food.
What type of digestion is emulsifying?
mechnical
Indications of liver problems
- fat in stool bc shows that not able to produce bile to help breakdown the fats to be absorbed into blood stream
- elevated liver enzymes like ALT (alanine transaminase), which normally turns alanine, an amino acid, into pyruvate.
- bleeding issues bc liver produces most of the clotting factors
- erratic BP bc produces albumin that normally holds water in vessels to maintain BP.
- high ammonia, which is toxic and can lead to confusion, bc liver is supposed to turn it into nontoxic urea
- nonalcoholic fatty liver dz
- cirrhosis
- hepatitis
What is the importance of Vit K?
needed in clotting factor production
note: calcium is also important for blood clotting
What is the function of the gallbladder?
store and concentrate bile; when there is food, it contracts and sends bile to the duodenum via the common bile duct
if too much bile is concentrated = get gall stones
What is the function of the pancreas (3 types of items it secretes)?
- makes exocrine products: MOST of the digestive enzymes (amylase, trypsin, lipase) that are then sent through the pancreatic duct to the duodenum
Note: pancreatic enzymes are activated by bicarb, which is also secreted by the pancreas
- also make bicarb, which neutralizes the acidic chyme coming from the stomach, so it prevents ulcers
- makes endocrine products: beta cells also makes insulin, a hormone, bc it is secreted into the blood
enzymes
What does amylase do?
breakdown starch into simple sugars
Bile is an enzyme T or F?
FALSE, it IS a chemical but is NOT an enzyme
Where do H. Pylori love to live and what can it cause?
- pylorus of the stomach
- stomach ulcers
What does the smooth m. in the digestive system do? What organs do they do that function in?
- wave peristalsis (from smooth m. contractions) to push food along ie. esophagus and stomach (churn and mix food) and intestines [ this motion is also present in the ureters]
- physical breakdown of food
How does peristalsis occur?
wave like contractions of the smooth muscles.
What type of macromolecule are enzymes usually?
proteins (end in -ase)
enzymes
What do proteases do?
What is an example of a protease?
- breakdown proteins into AA
- trypsin
What does lactase do?
breaks down lactose (a disaccharide carb) into glucose and galactose
What is the function of lipase?
breaks down lipids into fatty acids and glycerol
chemical digestion
- What enzymes are present in the mouth that aid in chemical digestion?
- What structure makes the enzyme?
- What is the enzyme function?
- amylase (as well as lipase) in saliva
- salivary glands
- breaks down starch (a complex carb, specifically amylose) into simple sugars (maltose, a disaccharide)
chemical digestion
- What enzymes are present in the stomach that aid in chemical digestion?
- what cells secrete the enzyme?
- What is the enzyme function?
- What is needed to activate this enzyme?
- pepsin
- gastric chief cells or zymogenic cells
- digests proteins into amino acids
- HCl (acidic environment) , made by the parietal cells
more protein eaten = more pepsin to digest the protein= need more HCL to activate it
Function of:
chief cells
parietal cells
goblet cells
Where are these cells found?
- produce pepsinogen, which turns into active pepsin with the help of HCL from parietal cells, so ultimately makes pepsin.
- make HCL to keep the stomach acidic to activate pepsinogen into pepsin and kill food-borne pathogens
- secretes mucus that protects the stomach lining from potential damage by HCL and digestive enzymes
Chyme is acidic or basic?
very acidic
What is chyme?
a semi fluid mass of digested and undigested food that is HIGHLY ACIDIC
Is the stomach acidic or basic?
acidic
[_____] factor made in [_____] is v. important for [______] absorption in the small intestines for making [______]
- intrinsic; stomach; Vit B 12; RBC’s
- What is needed for Vit B 12 absorption
- Where is that substance made?
- Where is Vit B 12 absorbed?
- intrinisc factor
- stomach
- small intestines -ileum
What is pernicious anemia
dec in vit B 12 absorption due to either stomach damage = no intrinisc factor made that is needed in order for vit to be absorbed or small intestine damage bc absorption site damaged
- common in old ppl and can give IM injections
Is the small intestine acidic or basic?
NOT acidic
chemical digestion
- What enzymes are present in the small intestines that aid in chemical digestion? (break it down into in house small intestine enzymes and enzymes coming from elsewhere)
- What is the enzyme function?
- in house: brush border enzymes- proteases and lactase (and maltase): protein and lactose breakdown, respectively
- pancreatic enzymes from pancreas to duodenum via pancreatic duct: amylase, trypsin, lipase : starch, protein, lipid breakdown, respectively.
[dont forget chemical BUT NOT enzyme from the liver via common bile duct - bile]
How does the small intestines deal with the acidic chyme coming from the _____.
- stomach
- neutralized by substances secreted by accessory organs with secretin release from stomach to stimulate release of: pancreatic bicarb and liver’s bile, which are both alkaline and basic
What is present in the digestive system to better absorb nutrients?
- small intestines have villi and micro villi(create brush border appearance) to increase the SA for absorption
villi= fold; finger like projections into the intestinal lumen
microvilli- microscopic projections of epithelial cells
Function of the large intestines
- NO digestion
- ONLY absorption of mainly H2O (and also absorbs vit K)
What happens to digested food after everything and anything is absorbed?
waste accumulates in rectum and is ready to be ejected through anus
What is urea?
non toxic metabolic waste of proteins made by the liver
What happens if ammonia builds up in the blood?
if hepatocytes can’t turn it into urea, then it can lead to confusion and irritability.
What dz’s can manifest if there is hepatocyte damage?
- fatty liver dz (ie. from high fructose diet bc the excess that is not used to make ATP has option to be converted into triglycerides and stored in the liver)
- liver cirrhosis (ie. from alcohol)
- hepatitis
Hormones involved in digestion
Insulin
* What secrete this?
* What is its function?
* Effect on blood sugar?
- pancreatic Beta cells
- causes uptake of glucose by cells –> mitochondria can break it down and store energy as ATP through cellular respiration
- ultimately decreases blood sugar
this is an endocrine hormone bc it is secreted into the blood.
Hormones involved in Digestion
Glucagon
* What secrete this?
* What is its function?
* Effect on blood sugar?
- pancreatic alpha cells
- stimulates liver glycogenolysis (also done by skeletal m.), lipolysis (also done by adipose tissue), and gluconeogenesis to release glucose into the blood
- increases blood sugar
this is an endocrine hormone bc it is secreted into the blood.
Hormones Involved in Digestion
Leptin
leads to feeling of fullness
Hormones Invovled in Digestion
Ghrlein
* What is it’s function?
* Where is it made?
- induces hunger (think Grumpy)
- made in the stomach (think stomach Grumbles)
What type of epithelial cells line intestinal walls?
simple columnar epithelium
What are the 4 layers of the intestines histologically wise?
- mucosa
- submucosa
- smooth m. layer
- peritoneum (serosa)
What are the 2 types of muscle that are in the intestinal wall?
circular/ tubular and longitudinal/ wraps around tubular ones
What is in the submucosa of the intestines?
- WBC’s , esp mast cells
- blood vessels (capillaries)
- lymphatic vessels (lacteals)
What is the purpose of the serosa in the intestines?
to make serous fluid in order to decrease friction when the intestines are moving around in the abdominal cavity
After lipids are broken down into fatty acids in the small intestines by [____], they are absorbed directly into [_______] to go to [_______] Bc [__]
- lipases
- the lymphatic vessels
- heart via the vena cava
- the heart relies almost exclusively on fatty acids to make cellular energy [heart CAN’T use glucose to make ATP]
After proteins/starches are broken down into AA and simple sugars in the small intestines by [___] and [___], respectively, they are absorbed directly into the [_____] to be delivered to the [____] in the [___] for processing.
- protease
- amylase
- small intestines blood vessels (capillaries)
- hepatic portal vein (so has alot of nutrients)
- liver
Describe the general process of food processing invovling the stomach, liver, pancreas, and duodenum.
- food chyme is made in stomach and gets to duodenum
2.** bile** either directly freshly made from liver and/or from the stored amount in gallbladder is released through the common bile duct to the duodenum / pancreatic enzymes and bicarb from pancreas through pancreatic duct to the duodenum to help **further chemically digest food ** - digested food (ONLY AA and simple sugars/ carbs NOT fats) is absorbed into the small intestines blood capillaries
- blood flow towards hepatic portal vein, which drains blood from the small intestines (as well as other gut organs) after a meal.
- liver processes the nutrients based on input of levels from the common hepatic artery and hepatic portal vein (ie. if excess sugars –> performs glycogenesis and lipogenesis)(ie. if liver senses low blood sugar–> performs glycogenolysis, lipolysis, or gluconeogenesis (glucogenesis from glycerol and/or AA’s))
- pushes out modified levels of sugars and amino acids through the Hepatic Vein –> Inferior vena cava –> heart
hepatic portal vein
- What main structure does it drain blood from?
- What is in the blood from that structure?
- What other structures does it drain blood from?
- small intestines after a meal
- NEW sugars(glucose and fructose) and AA that were absorbed in the small intestines
- stomach, pancreas, and spleen and large intestines (GUT Organs)
hepatic portal vein
[_____] are the resident WBC’s that prevent food-borne pathogens from infecting us
- Kuppfer cells
pathogens include: bacteria, viruses, fungi, worms.
What artery is carrying OXYGENATED blood to the liver from the heart?
- What other substance is in that artery?
Common Hepatic Artery
- “old” glucose that is already present in the blood at the time is in the artery and it tells the liver what the current blood glucose is.
What artery is carrying DEoxygenated blood to the liver?
Hepatic portal vein
State the direct path of bile travel from the liver to the duodenum
- R and L hepatic duct
- common hepatic duct
- common bile duct
- ampulla of vater
Name the blood input and output from the liver and what type of blood (oxygenated or deoxygenated) it carries.
- input- common hepatic artery carrying O2 from heart and “old , current glucose”; hepatic portal vein carrying nutrients from meal (ie. “new glucose”) (ie. fructose) and deoxygenated blood from the gut (ie. small intestines)
- output- hepatic vein carrying modified levels of nutrients (ie. sugars and AA’s) after liver processing based on 2 vessel input into the liver.
How do gallstones develop
when too much bile is concentrated in the gallbladder.
What duct controls the bile entering as well as exiting the gallbladder?
cystic duct
How are the pancreatic digestive enzymes activated?
the bicarb that is also secreted by the pancreas
Pancreatic amylase, trypsin, and lipase are what type of hormones?
exocrine hormones and go through pancreatic DUCT
Diarrhea can cause ____ due to the massive loss of ____ from the intestines
- metabolic acidosis
- bicarb (ie. made by the pancreas)
diarrhea can be due to cholera bacteria
What does the liver do with the fructose that comes through the hepatic portal vein after a meal?
- uses as much as it can ASAP to make ATP
- then , does lipogenesis (converts the rest to triglycerides) that is stored in the liver or shipped out as VLDL or LDL through the hepatic vein to adipose tissue for long term storage.
too much fat stored in liver –> fatty liver dz.
What two vessels aid in liver function as the blood glucose regulator
glucose from the common hepatic artery and the hepatic portal vein
What happens when the liver senses “excess glucose” in the blood from the heaptic artery and hepatic portal vein?
What can cause this excess glucose?
- the liver uses gucose to make ATP as needed
- Glycogenesis- store glucose as glycogen in the liver (skeletal m. also does this)
- After store as much glycogen as can, do lipogenesis where use glucose to make lipids.
- a carb heavy diet
insulin can also stimulate these processes
What happens when the liver senses “low glucose” in the blood from the heaptic artery and hepatic portal vein?
What can cause this low glucose?
- glycogenolysis-breakdown stored glycogen
- lipolysis-breakdown stored lipids
- gluconeogenesis- make glucose from amino acids (from protein from diet or from the body itself) or from fatty acids
- stress, not eating enough or lack of carbs in diet
cortisol, glucagon, catecholamines, thyroxine stimulates these processes
What hormone can be used to stimulate a
* decrease in blood glucose
* increase in blood glucose
- insulin
- cortisol, glucagon
- What is ketogenesis?
- What can cause ketogenesis?
- production of ketones, which are glucose substitutes for the body, from fatty acids
- fasting, low carb diet/ keto diet, butter, coconut oil
Explain diabetic ketoacidosis
no insulin or insulin resistance –> less glucose into cells for cellular energy –> liver starts performing ketogenesis to make ketones from fatty acid breakdown –> ketones in blood stream (if ketones build up in blood can cause metabolic acidosis bc ketones are acidic)
more common in those with type 1 diabetes
What organ performs ketogenesis?
What is the start and end product of ketogenesis?
- liver
- start: fatty acids; end: ketones
Where is the first site of mechanical digestion?
teeth in the mouth
chewing and grinding food
Where is most chemical absorption done?
(proximal) jejunum of the small intestines of broken down carbs, proteins, fatty acids; then duodenum
What does the ileum of the small intestines recover from the chyme before it passes into the large intestines?
vitamins (ie. Vit B12), salts, nutrients
