EK B2 Ch5 Digestive System COPY Flashcards

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1
Q

Digestive system

A
  • Breaks down food and absorbs constituents
  • Can be thought of as a “tube within a tube”
  • Digestive tract begins at mouth and ends at anus
  • Digestive system is specialized (cows can digest plant cellulose, humans can’t)
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2
Q

Three classes of organisms classified by diet

A
  • Carnivore = meat eating
  • Herbivore = plant eating
  • Omnivore = meat and plant eating
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3
Q

digestive tract

A
  • Digestive tract and liver are contained in the peritoneal cavity
  • Digestive tract has several tissue layers
  • Mucosa secretes mucus and enzymes, is the epithelium that lines inside of tract
  • Submucosa surrounds mucosa, contains blood vessels, lymph vessels, and nerves
  • Inner muscle layer (circular muscle) surrounds submucosa
  • Outer muscle layer (longitudinal muscle) surrounds inner muscle
  • Serosa and peritoneum surround muscle
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4
Q

GI motility and peristalsis

A
  • Smooth muscle contraction in GI enables food movement and mixing
  • Peristalsis is wavelike smooth muscle contraction that propels food forward
  • Peristalsis functions throughout digestive tract
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5
Q

Mouth and ingestion

A
  • Food is ingested and tasted in the mouth
  • Mechanical digestion by teeth and tongue
  • Lubricate food with saliva and chew to smaller bits
  • Chemical digestion of carbohydrates
  • Salivary amylase breaks down starch → smaller sugars
  • Chewed food is shaped into a bolus
  • Tongue moves bolus to back of mouth, swallowing moves bolus into pharynx
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6
Q

pharynx

A

Pharynx and esophagus do not digest food

• Pharynx is entrance to digestive and respiratory systems

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7
Q

pharynx and esophagus

A
  • Pharynx and esophagus do not digest food
  • Pharynx is entrance to digestive and respiratory systems
  • Esophagus leads to digestive system
  • Trachea leads to respiratory system
  • Epiglottis is a flap that covers the trachea during swallowing
  • Peristalsis moves bolus through pharynx to esophagus
  • Lower esophageal (cardiac) sphincter controls entry of bolus to stomach
  • Sphincter = smooth muscle ring
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8
Q

sphincter

A

= smooth muscle ring

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9
Q

trachea

A

leads to respiratory system

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10
Q

Esophagus

A

Esophagus leads to digestive system

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11
Q

stomach 2

A
  • Mechanical digestion from churning (smooth muscle contractions)
  • Chemical digestion of protein
  • Little absorption in stomach (only water, alcohol, a few drugs)
  • Stomach is elastic, folds (rugae) expand to accommodate food

Secretions include alkaline mucus, hydrochloric acid, and pepsinogen zymogen

  • Secretions controlled by hormones and nervous system
  • Acid environment (pH ~ 2)
  • Acidity inactivates bacterial and viral pathogens, denatures proteins
  • Acidity inactivates salivary amylase, activates pepsinogen → pepsin
  • Mucus and tight junctions protect stomach lining
  • Lack of mucus or failure of junctions → ulcer (sore)
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12
Q

pepsin

A
  • Acidity inactivates salivary amylase, activates pepsinogen → pepsin
  • Pepsin hydrolyzes proteins into shorter polypeptides
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13
Q

Chyme

A
  • Chyme = soupy, partially digested food mixture
  • Chyme exits stomach through the pyloric sphincter
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14
Q

stomach cell types

A
  • Chief cells secrete pepsinogen
  • Parietal cells secrete hydrochloric acid (pump H+ and Cl–)
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15
Q

small intestine

A
  • Chemical digestion of carbohydrate, protein, and lipid
  • Absorption of most nutrients
  • Longest part of the digestive tract
  • Three regions of small intestine: duodenum, jejunum, ileum
  • Most digestion takes place in duodenum
  • Most absorption takes place in jejunum, ileum
  • Acidic chyme is neutralized by sodium bicarbonate (from pancreas)
  • Ileocecal valve controls exit to large intestine
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16
Q

small intestine enzymes and secretions

A
  • Key digestive substances in small intestine are made in the pancreas and liver
  • Small intestine secretes a hormone called cholecystokinin (CCK)
  • CCK stimulates release of bile from gallbladder and enzymes from pancreas
  • Bile is made in the liver and stored in the gallbladder
  • Proteases, lipases, amylase, DNAse, RNAse from pancreas

• Small intestine makes some of its own enzymes to hydrolyze protein and carbohydrates

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17
Q

Bile

A
  • is made in the liver and stored in the gallbladder
  • Bile emulsifies fats (mechanical digestion increases fat surface area, then lipases perform chemical breakdown)
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18
Q

CCK

A
  • Small intestine secretes a hormone called cholecystokinin (CCK)
  • CCK stimulates release of bile from gallbladder and enzymes from pancreas
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19
Q

Aminopeptidase

A

Aminopeptidase cuts protein from N terminus

Small intestine makes some of its own enzymes to hydrolyze protein and carbohydrates: aminopeptidase is one of them

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20
Q

Maltase

A

Maltase hydrolyzes maltose → glucose and glucose enzyme of small intestine!

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21
Q

Sucrase

A

Sucrase hydrolyzes sucrose → glucose and fructose small intestine enzyme

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22
Q

Lactase

A

Lactase hydrolyzes lactose → glucose and galactose small intestine enzyme

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23
Q

small intestine microscopic structure

A
  • Small intestine surface has “brush-border” appearance
  • Surface is covered with villi (finger-like protrusions)
  • Each villus is a single layer of cells
  • Each cell has many microvilli
  • Villi and microvilli vastly increase surface area
  • Large surface area aids absorption and digestion
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24
Q

nutrient absorption in the small intestine

A
  • Nutrient absorption occurs by diffusion, passive, and active transport
  • Two key routes for nutrient absorption: blood and lymph
  • Each villus has capillaries and a lacteal (lymph vessel) • Amino acids and glucose → capillaries → blood
  • Blood flows directly to liver via hepatic portal vein
  • Fatty acids and glycerol → packaged as chylomicrons → lacteal → lymph
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25
Q

chylomicrons

A
  • Chylomicrons are protein-coated fat droplets
  • Chylomicrons are made from glycerol and fatty acids in small intestine epithelial cells
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26
Q

large intestine

A
  • Large intestine is also called the colon
  • Cecum, ascending colon, transverse colon, descending colon, sigmoid colon
  • Sigmoid colon leads to rectum and anus
  • Appendix is at end of cecum
  • Colon absorbs H2O and salt from chyme
  • As water is absorbed, residual undigested food is converted to feces
  • Colon has more bacteria than any other part of digestive tract
  • Mutualistic bacteria digest some food and provide vitamin B and K
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27
Q

large intestine chyme

A
  • If chyme moves too quickly, water is not absorbed, stool is watery: diarrhea
  • If chyme moves too slowly, too much water absorbed, stool is hard: constipation
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28
Q

pancreas

A
  • Produces sodium bicarbonate to neutralize chyme in small intestine
  • Secretes digestive enzymes (exocrine) into small intestine
  • Trypsin (from trypsinogen) hydrolyzes peptides
  • Chymotrypsin (from chymotrypsinogen) hydrolyzes peptides
  • Carboxypeptidase (from procarboxypeptidase) hydrolyzes peptides from C terminus
  • Pancreatic amylase breaks down carbohydrates
  • Pancreatic lipase breaks down fats into fatty acids and glycerol
  • RNAse and DNAse digest nucleic acids
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29
Q

Chymotrypsin

A

• Chymotrypsin (from chymotrypsinogen) hydrolyzes peptides

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30
Q

Trypsin

A

Trypsin (from trypsinogen) hydrolyzes peptides

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31
Q

Carboxypeptidase

A

Carboxypeptidase (from procarboxypeptidase) hydrolyzes peptides from C terminus

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32
Q

Pancreatic amylase

A

Pancreatic amylase breaks down carbohydrates

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33
Q

Pancreatic lipase

A

• Pancreatic lipase breaks down fats into fatty acids and glycerol

34
Q

Liver

A
  • Key metabolic center
  • Makes bile (stored in gall bladder)
  • Common bile duct conveys bile to small intestine
  • Nutrients from digestion flow through hepatic portal vein to liver → circulation
  • Stores iron and fat soluble vitamins: A, D, E, K
  • Detoxifies drugs and alcohol
  • Converts glucose → glycogen
  • Converts precursors, including pyruvate, oxaloacetate, glycerol and amino acids → glucose (gluconeogenesis)
  • Converts ammonia → urea
  • β-oxidation of fats
  • Deamination of proteins
  • Control fat metabolism and makes cholesterol
  • Liver can regenerate itself from 1/4 of original size
35
Q

when studying digestion keep the organization principles in mind:

A
  1. location
  2. pH
  3. surface area- it is increased by structural arrangements in different regions of the digestive tract, surface area and length promote absorption*
36
Q

amylase

A
  • chemical breakdown of food is initiated by this enzyme, alpha-amylase**
  • contained in saliva
  • this enzyme begins to break down the long straight chains of starch (major carbohydrate in human diet) into polysaccharides by cleaving the alpha-1,4,glycoidic bonds
  • chewing inc the surface area of food enabling more enzymes to act on the food at one time
  • chewed food forms a clump in the mouth called a bolus*
37
Q

peristalsis

A
  • a contraction of smooth muscle in the digestive tract, creates a wave motion that pushes along the partially digested food
  • also occurs in small and large intestines
  • saliva acts as the lubrication for the food, helping it move down the esophagus
  • so this is a wavelike motion of smooth muscle that moves food through the digestive tract like squeezing a tube of toothpaste at the bottom and sliding your fingers toward the top to expel the toothpaste

peristalsis= rings of smooth muscle around esophogaus, that is hwat pushes the food down to the stomach, between the bottom of esophagus and beginning fo stomach there is a spincter

38
Q

gastric juice

A

the acidic environment in the stomach is maintained by this, the inside of the stomach is highly acidic

  • a combination of acid, enzymes and hormones released by cells in the lining of the stomach
  • a full stomach has a pH of 2
  • the low pH of the stomach contributes to protein digestion by denaturing proteins, and also helps to kill ingested bacteria
39
Q

exocrine glands in stomach

A
  • stomach contains exocrine glands in recesses called gastric pits
  • like other exocrine glands, they secrete molecules onto epithelial surfaces instead of blood stream (endocrine glands)
  • in the stomach the exocrine glands use ducts to deliver their secretions to specific locations in the external environment, in this case to the lumen of the digestive tract
  • their job is to maintain the acidity of the environment and aid in digestion
40
Q

endocrine glands (in stomach)

A
  • system of glands that do not have ducts and instead secrete their products directly into the internal environment of the bloodstream to circulate throughout the body
41
Q

4 major cell types in the stomach

A
  1. muscous cells
  2. chief (peptic) cells
  3. partial (oxyntic) cells
  4. G cells
42
Q

mucous cells

A
  • secrete mucus
  • line the stomach wall and the necks of the exocrine glands, composed mainly of a sticky glycoprotein and electrolytes
  • mucus lubcricates the stomach wall so that food can slide along its surface without causing damage
  • also protects the epithelial lining of the stomach wall from the acidic environment inside the stomach
  • some mucous cells screte a small amount of pepsinogen
  • like other cells specializing in secreting mucus cells contain larger amounts of rough ER and golgi bodies to make mucus
43
Q

chief cells

A
  • deep in the exocrine glands secrete pepsinogen*** the zymogen precursor to pepsoin
  • zymogen= meaning proenzymes, are inactive precursurs to enzymes that can be activated to become functional enzymes
  • the low pH in the stomach activates pepsinogen to become pepsin, once activated pepsin begins protein digestion
44
Q

What vitamins does liver store?

A

• Stores iron and fat soluble vitamins: A, D, E, K

45
Q

parietal cells

A
  • secrete hydrochloric acid into the lumen of the stomach through active transport which requires a large input of energy
  • these use a lot of energy to create HCl*** for digestion so these cells contain large numbers of mitochondria needed to produce sufficient energy to establish a proton gradient*

lumen just means the inside space, “inner opening”, cavity or channel within a tube or tubular organ such as a blood vessel or the intestine.

46
Q

pepsin 2

A
  • breaks down proteins
  • pepsin precursor is pepsinogen, is inactive; so it doesnt harm the cells of the stomach as it is released
  • it only becomes active in response to the acidic environment of the stomach*
47
Q

G cells

A
  • secrete gastrin
  • gastrin is a large peptide hormone that stimulates parietal cells to secrete HCl
  • G cells communicate with both the outside (the stomach lumen) and hte inside (the bloodstream) of the body, when activated G cells releases gastrin into the bloodstream, the signal causes inc HCl production in stomach parietal cells
  • the G cells in the stomach wall are activated through a variety of methods…. presence of polypeptides in the stomach, stomach dissension, and input from teh parasympathetic nervous system through the vagus nerve
  • G cells also contain larger amounts of rough ER and golgi bodies*
48
Q

gastrin and histamine inc…..?

A

they inc HCL secretion*

so tied to G cells which secrete gastrin*

49
Q

The villi and microvilli….

A

Each villus is a single layer of cells

Each cell has many microvilli

Villi and microvilli vastly increase surface area

They create more surface area for small intestine which maximizes our absorption of nutrients, because nutrients are absorbed directly across the walls into the blood and so you need a lot of surface area to maximize that absorption! So nutrients don’t flow by and not get absorbed! These structures are very very specialized to maximize surface area, need it for absorption!

50
Q

Sphincter =

A

smooth muscle ring

So opening to stomach is pinched closed with this spinchter or ring of smooth muscle important for controlling passage of material

It is called lower esophoagel (cardiac) spincter, some jerk called it cardiac because near body, where is cardiac sphincter NOT IN HEART in bottom of esophogaus*

51
Q

The mouth and digestion 2

A
  1. Goal= break down food and absorb consitutents
  2. Muscle surrounding tube is smooth like muscle, how this massive material starts out at mouth and moves down, how it is propelled forward through rhythmic smooth muscle contractions called peristalsis all the way through digestive tract
  3. Liver and pancreas, mostly send over secretions into the small intestine that helps with this process, called helper/auxillary organs
  4. Mouth- food ingested, tasted and chew it all about digestion= process of breaking down chunks of food, and absorption is getting from tube into blood stream* then to connect with metabolism, once neutrients are absorbed and in blood stream can circulate around get insdie cells, in cells and worked on by medical pathways we talked abut, digestion first main process, comes in two types mechanical or physical digestion
  5. Mechanical digestion chewing ripping bigger chunks into smaller cunks, and chemical digestion hydrolysis reaction being catalyzed, so in the mouth there is lots of mechanical digestion and chewing one type of chemical digestion only of carbohydrates=we have an enzyme in mouth called salivary amaylase= comes from salivary glands, breaks starch down into simpler sugars by hydrolyzing bonds in the starch*
  6. So if you eat a turkey sandwich, bread starts to be chemically digested before the meat. Carbs get digested chemically first, everything is physically broken down by chewing, thing moves bolus or blob of food to back of mouth and swallow it
52
Q

Stomach 3

A

Stomach structurally is stretchy* if you eat a big mean know our stomachs expand, all of these folds stretch to accomodate a big meal, so if we eat a big meal our stomache can stretch other thing that can happen

stomache has mechanisms for inactivating bacteria or other things in our food, our stomache is really really really acidic pH of 2** very protective to have that acidicty in our stomache* but it does create an issue for the stomach because most cells are not very happy in an environment that is so acidic, so very very important we have a mucus lining around stomache to protect walls of stomache from acid soup in stomach, tight junctions in all cells lining stop so acidicy doesn’t leak out to other parts of body, lower esophoagenl cadiac sphincter has to function properly because that is another place where acid splashes out in wrong the direction, acid pushed up into lower part of the esophageus and that is what is referred to as acid reflux*

53
Q

gap junction versus tight junctions

A

gap allows material to pass betweel cells and tight junctions are sealed so nothing can pass through

stomache most famous example of where need tight junction!!! No acidity splash anywhere, heart biggest example where need gap junctions ion to travel from one cell to the other to propagate muscle potientals of muscles in heart to get correct corrdiantion*

You can make different kind so junctions, obviously cardiac muscle cells have gap junctions because of heart and stomache epitheial cells have tight junctions because what is needed in stomache, what underlies function of cell, proteins that make it up, can join togther in a certain way* what are those proteins how are they connecting to eachother, why are these proteins making a little tunnel between thsemvles and those rptoeisn are making a seal, just know that cells are supposed to be forming tight junctions produce certain kinds of proteins and build certain kinds of junctions around membrane to allow those to form***

54
Q

Stomach cells 2

A

2 kinds of cells lining the stomache, there are if you arelooking pits in the walls of the stomache and these are cells lining the pits, need ot know cell names: 3 cells: 1. Muscus cells produce msucus, 2. Parietall cells produce HCL( all acidicy talking about, cells main job in life is to turn out acid into stoamche) 3. then other cells that produce pepsinogen= precursor inactive form of enzyme usually protease enzyme, huge example of zymogen, pepsinogen is secreted by cells called chief cells, then activated by HCL ot pepsin!

parietal cells pumps out hcl* and then you need ot know cleavage reaction catalyzed by HCL that cleaves pepsinogen, turns it into pepsin, and pepsin is a proteases, digestive enzyme that specifically cuts bigger protens into smaller peptides*

HCL activates pepsinogen to pepsin*

55
Q

Stomach secretes….

A

Secretions include alkaline mucus, hydrochloric acid, and pepsinogen zymogen

Acidity inactivates salivary amylase, activates pepsinogen → pepsin

56
Q

If you eat a turkey sandwich….

A
  1. If eat turkey sandwich chemical digestion of bread amayalse is in mouth, chemical digestion of turkey just started with pepsin** in stomach
    1. Nutrients absorption happens later but some absorption that happens from stomach, specifically absorption of alcohol and then some drug compounds gets absorbed directly across lining of stomache* that is why if have a drink can feel affect pretty quickly righ through lining of stomache, whereas nutrients from food gets absorbed a bit later down, pepsin enzyme that breaks down proteins* so call it a proteases**
    2. Mechanism for pepsin involes hydrolysis, what pepsin bond actually catalyzing is reaction that hydrolyzes peptide bond*

SO CHEMICAL DIGESTION OF TURKEY BEGINS WITH PEPSIN

57
Q

Small intestine 3 parts:

A

3 sections=Duodenum, jejunum, ileum

Duodenum= first one third of small intesntine is where most chemical digestion takes place in body! Ton of chemical breakdown of food at this point, then the much more chopped up stuff is much smaller pieces of everything moves onto jejunum and ileum where most ABSORPTION takes place, where little molecules at that point down to monomers and amino acid, where stuff is absorbed and passes out of digestive tract into the rest of the body!!

Small intestine needs a TON of help, as a reminder liver and pancreas and gall bladder which works with liver are all sending stuff over to small intestine

So helping really sending stuff to duodenum first part of small intestine, where so much chemical digestion is taking place

We have the acid coming from stomach with a pH of 2, small intestine does not have stuff to protect itself so acid chyme, first role of business for duodenum is to neutralize that aciditiy, so small intestine shouts out to pancreas to send over something to neutralize the aciditiy, pacnreas sends sodium bicarbonate solution

From gen chem this is basic and what alters pH of all this material gushing in small intestine so doesn’t burn a hole in the wall, so pancreas also does a whoel lot more than that, so first to know pancreas sends sodium bicardboante and a lot of other stuff to neutralize chyme in duodenum but then TONS of digestive enzyme for every macromolecule

58
Q

Pancreatic juice

A

trypsin another proteases and chymotrypsin hydrolyzes pepsides

carboxypeptidase, another thing that breaks down peptides

pancreatic amylase to break down carbs and prancreatic lipase to break down fats into fatty acids and glycerol= all of this is sometimes referred to as pancreatic juice, pancreas just sends over big stew of enzymes plus sodium bicarcboante*

endocrine secretions are hromones secretd from cells diretly into blood stream, exocrine secretons are secreted mostly digstive enzymes when mention exocrine secreton! Those are secreted from cells but don’t go into blood stream secreted by ducts!

The fact that all of the pancreatic juice goes through that little tube into the small intestine, that makes all of these enzymes exocrine secertions becuas ethey are going through ducts!

59
Q

Pancreas is famous for being what kind of organ?

A

Pancreas is famous for being an exocrine organ and endocrine organ, in sense that it secretes all of these enzymes so it is exocrine, but also secretes hromones= insulin and glucagon** so it is endocrine!

Different cells in pancreas that do different thing but pancreas can wear an exocrine and endocrine hat, usually both!

exocrine secretions are secreted mostly digstive enzymes when mention exocrine secretion; all of these enzymes are exocrine secertions becuase they are going through ducts!

60
Q

Pancreas enzymes- what causes pancreatitis?

A

Pancreas enzymes are all hydrolytic enzymes, breaking bonds in proteins, carbs or fats*

The enzymes that hydrolyze peptide bonds =chymotrypsin, trypsin, carboxypeptidase, zygmogen given trypsin originally syntehsized as trypsinogen, trypsin actives the others

chymotrypsin is originally made of chymotrypsinogen

carboxypeptidase has a zymogen form called procarboxypetidase

that is very important because zymogens only get activated to their protein cutting form when they get to the small intestine! If they get accidently activated in pancreas start destroying pancreas, whole point of proteases to cut proteins and LOTS of structures in pancreas so that causes pancreaitis, zymgoen is inactive form is the form synthesized first! So think about translation, putting back in biochem conext, translation produces zymogen, so after ribosome and then zymogen have to be activated by HCL or another enzyme in some cases to become active and to start to break peptide bonds!

In a biochem context, it’s an example of posttranslational modification or regulation, all you need to know is produced from ribosome in inactive form, pancreatisis can happen when zymogens get activated inappropriately in the pancreas and start destroying pancreas and then questions about zymgoens supposed to be activated in small intestine!

So all those thigns get to small itnstine and do a TON of hydroylsis, every category of macromolcule is represented here, multiple enzymes to break down protein, carbs, fats, nuceluc acids so no matter what you eat will be some chemical digestion based on the activity of these enzymes from pancreas to small intestine, RNAse and DNAse digest nucleic acids

61
Q

Small intestine makes some of its own enzymes to hydrolyze protein and carbohydrates:

A

Small intestine makes some of its own enzymes to hydrolyze protein and carbohydrates:

Aminopeptidase cuts protein from N terminus

Maltase hydrolyzes maltose → glucose and glucose

Sucrase hydrolyzes sucrose → glucose and fructose

Lactase hydrolyzes lactose → glucose and galactose

  1. these are made in addition to pancreas enzymes that come over, so remember all enzymes that break up DISACCHARIDES maltose sucrose and lactose are broken up by maltase, sucrase (glucose plus fructose) dissacharide two monomer units* little moelcuels compared to big molecule of starch, lactase chops up lactose, and maltose is a saccharide made of glucose and glucose*
  2. So that is all happening and then amino peptidase is good to remember btecuse it’s a protease, breaking peptide bonds but all other proteases come from pancrease, so if asked which of the following is produced by cells in small intestine amino peptidase stands out because contrast to all the other ones we have talked about!
62
Q

Bile

A

Fat- trickier for digestive system to handle, harder to solubilize its hydrophobic, if you have a big chunk of butter or something its harder to process in aqueous environment, so mention bile!

BILE= main thing in auxillary organs liver connected closely to digestive tract, liver produces bile and then stored in gallbladder

Gallbladder is the little pocket that sits on bottom of liver, liver makes bile, bile is stored in gallbladder and when food enters small intestine–> bile sent over to first part of small intestine we are talking about

Role of bile acts as emulsifier or detergent= what it is doing is physically breaking up bigger chunks of fat into smaller chunks of fat, same way soap or detergent would, gets in there and helps to solibuilize chunks of fat, physical not a chemical purpose then once the big chunks of fat are broken into smaller chunks of fat then enzyme lipase, on our list of enzymes from pancreas, lipase can get in there and have enough access to do chemistry hydrolyze bonds in triglcyerides*

So then material all chopped up, have a lot of smaller monomers at this point, smaller peptides and aa, triglycerides chopped down to fatty acids and glycerol, sugar broken down to smaller sguars glucose fructose, lactroses, picture smaller monomers moving onto jejunum and ileum where absorption occurs once chopped up everything into smaller parts!

63
Q

What goes into the blood stream right to the liver?

A

The lining example of up and down, up and down surface, top of the lumen, interior of tube, and the finger like projections project up into lumen!

Notice that inside of this there is a capillary and lacteal! The green thing is lacteal or lymph vessel! The break down products of carbs and proteins simple sugars and amino acids, small peptides, will be absorbed directly across epilethial layer of cells into capillarys, look at red arrows in picture, glucose goes straight across epitheial cells into blood/ amino acids right into blood!

The breakdown products of fats take a little bit of a different path, but sticking with glucose and amino acids they go right into blood stream from lumen of small intestine, into a capillary inside one of these villi*

To really connect the dots, the blood in that capillary can come together into larger vessels and go into hepatic portal vein into liver, so blood flow from the digestive system, the blood rich in nutrients that have just been absorbed goes righ to the liver! Through the hepatic portal vein, v important when talking about metabolism, talking about how liver gets first crack and nutrients. The liver has glucokinase instead of hexokinase so can skim off excess glucose and store it as glycogen, can do glycogen making pathway by time the blood gets passed the liver, it should have a tightly regulated concentration of glucose, there shouldn’t be crazy high blood sugar anymore

64
Q

How do fats get

A

From liver gets first crack and nutrients, has glucokinase instead of hexokinase so can skim off excess glucose and store as glycogen, can do glycogen making pathway, by time the blood gets passed the liver! Blood not as high in glucose anymore past liver!

Then blood continues to travel around the body, and insulin is necessary for getting glucose into the cells as blood goes through muscle cells need insulin, insulin helps the sugar get into cells and then the cells can do glycolysis and krebs cycle and make atp and then really connected to all metabolism stuff talking about

Fats get into small inestines, broken up physically by bile, then broken up chemically by lipase, then fatty acids and glycerol and other broken down lipids, but then they don’t pass directly into blood, instead they will go into lympathic system, into that lacteal green vessel can see inside villus!

Triglycerides broken down and fats broken by lipase to glycerol and fatty acid some monoglycerides as well smaller breakdown products, those smaller breakdown products go into tan colored epithetial cell then built up again

Triglycerides are reassembled inside the cell, and then they are further packaged with proteins and glycolesterol into these spheres called chylomircons* so in the epithetlial cells lining small intestine chylomicrons made and then go into green vessels called lacteals do not go directly into blood stream* so then everything in lacteal or lymp vessels circulates around and then eventually gets poured into regular veins and venus circulation, duct called thorasis duct near each shoudler, all this stuff gets emptied into regular blood circulation just doesn’t go there right away! Can talk a lot more detail about this lympathic system with immune system, second transport system picks up chylomicrons to around…….? liver uses this to make LDL and HDL good cholesterol versus bad cholesterol*

65
Q

good cholesterl versus bad cholesterol

A

Liver uses what …..to make LDL and HDL good cholesterol versus bad cholesterol* LDL bad ones and HDL is good ones

66
Q

Classic MCAT question which of the following is not absorbed from small intestine=

A

Things like glucose are absorbed from small intestine into blood, but chyromicrons are produced in the cells that line the small intestine* made in the cells the lining of the small intestine, up in pink part is lumen fo small intestine, where all digestion taking place

chyromicrons not absorbed in lumen don’t exist in lumen produced in cell!

67
Q

Main purpose of the colon:

A

Main purpose of the colon: absorb water!

We have absorbed nutrients now have to absorb water, how much is absorbed is partly related to how quickly material moves through colon, remains of digestion and colon move through colon really quickly not enough gets absorbed and ppl have diarreha, if slower and more water gets absorbed can cause constipation!

If you have more solute in the lumen the inside of tube in colon because lets say you eat something that acts as solute and isn’t absorbed, then your fesces can be more watery, more solute in lumen of colon more water will get pulled in there as well!

If don’t absorb molecule moving through colon as solute, can also cause water to be retained in colon, whatever water balance is in all that stuff whenever reaches end of the colon that is what is coming out!

Mutualistic bacteria digest some food and provide vitamin B and K, where research in microbiome is! So anything that stays in tube and is nto absorbed, absorbing means leaving tube and going into blood! Which si super important water you need in body, water drinking etc

68
Q

Large intestine 2

A

After small intestine everything passes into large intestine also refered to as colon! The large intestines has a bunch of sections can see in diagram it goes up over and down and out! Ther eis an asecending and descending colon, then sigmoid colon leads to rectum and anus!

Very beginning part of large intestine called cecum branching off of that is appendix, outcroping of colon and usually only reason ppl heard of appendix it’s a vestigle structure, no function ppl know about, but can be an emergency is the appendix becomes infected or inflamed ppl have to have emergency surgery /inflamed so have ot be removed

Whole colon is really choked full of great bacteria in colon, balance of good bacteria versus bad bacterial, vs pathgentic bacteria, this is where a lot of our good bacteria is, appendix can become infected tons of bacteria in appendix but usually bacteria they are fine with, but under some circumstances balance tipped and pathgenci bacteria an take over and cause an infection*

69
Q

Fat soluble vs water soluble vitamins

A

liver also stores iron and fat solube vitamins so vitams A, D, E,K

some vitamins are water soluble like vitamin C or all B, meaning can have almost unlimited amounts and if you have too much just pee them out,

ADEK are FAT soluble vitamins, stored in liver, a little harder for body to get rid of, ppl debate how much vitamin D we need

Vitamin A can actually be toxic especially to pregnant women, in terms of taking care of patients and making sure someone if taking vitamins they are also not megadosing on vitamin A because v dangerous, vitamin A can cause defects in fetus if take too much; and it is not exactly known can cause a range of symptoms in nonpregnant ppl, sometimes ppl are not aware that you cannot have infinite amounts of vitamin supplements, so many things fortified with vitamins if taking nutrient drinks and pills something can be a potential red flag in clinical environment

70
Q

Liver facts

A

It converts ammonia to urea!

With proteins you can hydrolyze proteins to amino acids then clip off amino group because nitrogen needs to go off of the molecule for the moelcuel to fit into a lot of metabolic pathways we know about, so if cut an amino group off of an amino acid first thing get is ammonia= nh3!

Ammonia is pretty toxic do not want a lot of ammonia floating around in blood, can make blood too basic v toxic for many different reasons, send ammonia to liver to be converted to urea, urea form in which we keep / want our nitrogen based waste, want in urine, excrete nitrogen based waste as urea!!!

So liver responsible for this step taking ammonia comes from amino acid, turning into urea and then kidney gets rid of urea!

Cool crazy fact about liver is can regenerate itself from quarter of riginal size, certainly can’t do that with heart, can’t cut a donor heart in half and give to two different ppl but can do that with liver! A liver can regrow and regenerate itself pretty special among our organs

71
Q

Liver converting ammonia into urea

A

Ammonia is pretty toxic do not want a lot of ammonia floating around in blood, can make blood too basic v toxic for many different reasons, send ammonia to liver to be converted to urea, urea form in which we keep / want our nitrogen based waste, want in urine, excrete nitrogen based waste as urea!!!

So liver responsible for this step taking ammonia comes form amino acid, turning into urea and then kidney gets rid of urea!

Ammonia= NH3

Our body has a method to safely package ammonia in a less toxic form to be excreted. This safer compound is urea, which is produced by the liver using 2 molecules of ammonia (NH3) and 1 molecule of carbon dioxide (CO2). Most urea is then secreted from the liver and incorporated into urine in the kidney to be excreted from the body, as shown below.

72
Q

HCL….

A

HCL** cleaves pepsinogen to pepsin

cells secrete HCl are called parietal cells** chief cells secrete pepsinogen***

Since these are stomach cells, to protect the lining of stomach mucus protects us from the chyme, the tight junctions prevent acid leaking out

73
Q

Bile 2

A

Bile made in liver, stored in gall bladder and released from gall bladder

It is physiclally breaking down big blobs of fat into smaller blobs** the enzyme that will chemically digest fat after that is lipase

74
Q

How is glucose broken down….

A

Glucose broken down and then reasborbed mostly in jejunum and ilenum, then goes through capillaries then hepatic portal vein

Lipase breaks down trigyclerides> free fatty acids go into epiphelial cells lining small intestine* but then they get build up again intro triglycerides and then built up even more through packages with proteins into chylomicrons

Chylomicrons don’t go directly into blood which go into lacteals part of lympathic system then everything in lympathic system dumps into regular system by way of thorsaic duct by shoulder

Under normal circumstances all glucose should be absorbed in proximal tube, if not shows up in urine and sign of diabetes or high blood sugar***

75
Q

Fatty acid image

Q. 16. Which of the following is NOT absorbed from the intestinal lumen?

a. Chylomicrons
b. amino acids
c. Fatty acids
d. Glucose

A

Answer is a Chylomicrons

  • chylomicrons from there go into green lacetal at hte bottom and from there they circulate in lymphatic system and then all that material in lympahtic system/ fluid in lacteals gets dumped through pores into thoracisc duct in shoulder and hten goes into veins
  • chylmocirons never present in lumen of small intestine, only created inside of that epithelial cell, in tan*
76
Q
  1. What is a lacetal:
    a. absorb glucose from lumen
    b. carry amino acids to the liver via the hepatic portal vein
    c. transport chylomircons
    d. are present within intestinal eptithelial cells
A

answer is c transport chylomicrons

small vessel that transports fluid through the lymphatic system, sometimes they refer to it as a lympth capillary*

chylomicrons pass from epithelial cells lining the small intestine and transported by lacetals**

77
Q
  1. Cholera toxin (vibrio cholerae) stimulates the excessive secretion of chloride ion into the intestinal lumen. Na+ ions follow passively. Which of the following would you NOT expect as a result?
    a. Diarrhea
    b. Increased movement of water into the lumen
    c. Subsequent increase in aldosterone levels
    d. Constipation
A

d. constipation

the lumen of a tube would be like the inside of the tube, can tlak about the lumen of any enclosed thing but here the lumen of the intestine means* inside the tube*** also thinking lumen of ER for protein synthesis, again just means interior*

if we have a cholera toxin causing cl- extra inside of the lumen if think about balance of solute and water, H20 will stay in the lumen more becuase of more solute extra Cl- so all of this extra water that otherwise woud have been reabsorbed, but hanging around because we know water likes to follow solute so becuase of cholera all this excess Cl- so the water hangs out and then the whole thing moves merrily along and by the time all that waste material leaves the body it is much more watery then it would be otherwise*

Would water come in as well following Na+ from outside lumen into colon?- mainly all water already there just doesnt get absorbed because Na/cl-, lot of it is supposed to get absorbed and if it doesnt that is a huge amount of water loss

crazy statistics of ppl which cholera lose body water weigh 10% of water in hours, dramatic and often fatal lose of water* suddenly becasue of all of this* why for ppl who have prompt and good medical care you would not die of water loss you need to be rehydrated and body wait it out. if you do not have access to that you lose too much water fast, so fast and fatal amount of water loss nothing can do

78
Q

Image of what cholera issues would look like:

A
79
Q

What does deamination look like?

A

deamination of proteins happens in liver

80
Q

Conversion of ammonia to urea looks like….

A
81
Q

After the gall bladder is removed from a patient, the patient will most likely have reduced ability to digest:

A

bile

Answer Key: D The gall bladder stores bile produced by the liver and secretes it into the small intestine as needed. Bile acts as an emulsifier, facilitating fat digestion. When the gall bladder is removed, a patient will have reduced ability to digest fats.