Physiology of small intestine & colon Flashcards by Stacey Hansen

Does the proximal or distal small intestine have more frequent slow waves (BER)?

Proximal (12/min)

distal has 8/min

How well did you know this?

Not at all

Perfectly

Is contractile frequency constant from the duodenum to terminal ileum?

proximal SI has more frequent slow waves than distal SI

How well did you know this?

Not at all

Perfectly

Does vagotomy abolish contractile activity during the digestive period?

How well did you know this?

Not at all

Perfectly

Contractile activity of the small intestine is initiated in response to this

Distention

How well did you know this?

Not at all

Perfectly

These cells are pacemakers in GI smooth muscle, and control slow waves activity/propagation

Interstitial cells of Cajal (ICC)

How well did you know this?

Not at all

Perfectly

Do Interstitial cells of Cajal (ICC) control slow waves or spike potentials of the small intestine?

Slow waves

How well did you know this?

Not at all

Perfectly

This type of GI contraction functions in mixing
Results in increased surface area
Helps the efficacy of digestion and absorption

Segmentation

How well did you know this?

Not at all

Perfectly

This type of GI contraction functions in separation (sphincter)
Is non-propagating

Tonic contraction

How well did you know this?

Not at all

Perfectly

This type of GI contraction functions in propulsion
Stretch, weak, short distance
Due to intact myenteric plexus

Peristalsis

How well did you know this?

Not at all

Perfectly

What is the function of segmentation GI contractions?

Mixing
(helps the efficiency of digestion and absorption)

How well did you know this?

Not at all

Perfectly

What is the function of tonic GI contractions?

Separation (sphincter)

How well did you know this?

Not at all

Perfectly

What is the function of peristalsis GI contractions?

Propulsion

How well did you know this?

Not at all

Perfectly

In paralytic ileus, are slow waves present?

Yes
(but no spike potentials)

How well did you know this?

Not at all

Perfectly

In paralytic ileus, are spike potentials present?

No
(but slow waves are present)

How well did you know this?

Not at all

Perfectly

Paralytic ileus involves continuous firing of these neurons

Intrinsic inhibitory neurons (VIP or nitric oxide)

How well did you know this?

Not at all

Perfectly

Peritoneal irritation can occur during the handling of gut during surgery, and can result in this condition involving the hyperpolarization of smooth muscle

Paralytic ileus

How well did you know this?

Not at all

Perfectly

These cells of the brush border have microvilli

Enterocytes

How well did you know this?

Not at all

Perfectly

Are enterocytes of the brush border absorptive or secretory cells?

Absorptive cells

How well did you know this?

Not at all

Perfectly

Do crypts of Lieberkuhn contain absorptive or secretory cells?

Secretory cells

How well did you know this?

Not at all

Perfectly

Do enterocytes or crypts of Lieberkuhn have absorptive function?

Enterocytes

How well did you know this?

Not at all

Perfectly

Do enterocytes or crypts of Lieberkuhn have secretory function?

Crypts

How well did you know this?

Not at all

Perfectly

Does the small or large intestine absorb more water?

Small intestine

How well did you know this?

Not at all

Perfectly

In the intestine, is water movement passive or active?

PASSIVE always; relies on the movement of ions/substrates

How well did you know this?

Not at all

Perfectly

Does the small or large intestine have leaky junctions?

Small

How well did you know this?

Not at all

Perfectly

Does the small or large intestine have tight junctions?

Large so absorption is more efficient

Does the small or large intestine have more efficient absorption?

Large

Is a meal usually hyper, iso, or hypotonic to plasma?

Hypertonic

In the small intestine, will water move in or out of the gut?

INTO the gut - to dilute the osmolality of meal

By the time a meal reaches the jejunum, is it hyper, iso, or hypotonic to plasma?

Hypotonic (due to the absorption of ions and solutes as the meal traverses the small intestine)

Na/Glucose and Na/AA co-transporters are only in this part of the GI tract

Small intestine

What are the four mechanisms for absorption of sodium in the GI tract?

Na/Glu and Na/AA co-transporter Na/H exchanger Na/H and Cl-/HCO3- exchanger eNaC

Does the small or large intestine absorb more sodium?

Small intestine note: Both absorb sodium

This drug used to treat high BP will block reabsorption of Na Works the same way in kidney

Amiloride

Amiloride is used to treat BP, and it blocks the reabsorption of this

Sodium

Aldosterone increases the absorption of this ion in the colon

Sodium

Transcellular absorption of calcium only occurs in this part of the GI tract

Duodenum

In transcellular absorption of calcium, calcium is absorbed via this channel

TRPV 5/6 channel

This hormone causes withdrawal of calcium from bone, which can result in softened bone (basis of Rickets)

Parathyroid hormone

Parathyroid hormone causes withdrawal of calcium from bone, and also causes the release of this, which will result in increased calcium absorption from gut

vitamin D3

In transcellular absorption, calcium enters the cell and becomes bound to this calcium binding protein

Calbindin

The formation of this calcium binding protein is enhanced by vitamin D

Calbindin

Formation of calbindin is enhanced by this vitamin

Vitamin D

This is the primary active transport mechanism used to absorb calcium across the basolateral membrane

Exchange for H+ (plasma calcium membrane ATPase - PCMA)

This is the secondary active transport mechanism used to absorb calcium across the basolateral membrane

Exchange with sodium

Does transcellular or paracellular absorption of calcium occur only in the duodenum?

Transcellular

Does transcellular or paracellular absorption of calcium occur throughout the small intestine?

Paracellular

Rickets is due to a lack of the active form of this vitamin Soft bones, bowed legs, stunted growth

vitamin d

Most iron is absorbed as this form

Fe2+ (ferrous)

During the absorption of iron, Fe2+ enters the cell via this protein

DMT1 (in association with H+)

This is the storage form of iron

Ferritin

Uptake of iron at the apical membrane of enterocyte is limited by this to bind iron

Mobilferrin

This enzyme breaks down heme to produce ferrous iron (Fe2+)

Heme oxygenase

This protein oxidizes Fe2+ to Fe3+, where it can be bound to plasma transferrin

Hephaestin

Iron is stored in this part of the body

Liver

Iron is utilized in this part of the body

Bone marrow

Does the CFTR channel move Cl into or out of the intestinal lumen?

Into

Do prostaglandins stimulate or inhibit secretions in the gut?

Stimulate (not for acid)

Does acetylcholine stimulate or inhibit secretions in the gut?

Stimulates (increase Ca, which stimulates CFTR transport)

Does vasoactive intestinal polypeptide (VIP) stimulate or inhibit secretions in the gut?

Stimulate (increases cAMP which activates CFTR transport of Cl- into lumen)

Cholera toxin results in an increase in this molecule, which stimulates CFTR transport

cAMP

What is the treatment for cholera toxin?

Rehydration (Na+ and glucose)

Digestion of carbohydrates mostly occurs in this part of the GI tract

Proximal small intestine (duodenum)

Is amylose or amylopectin glucose linked together by straight chains?

Amylose

Is amylose or amylopectin glucose chains that are highly branched?

Amylopectin

Is there carbohydrate digestion in the stomach?

No salivary amylase is inactivated by low pH

Positive hydrogen breath test could indicate this condition

Lactose intolerance

These two parts of the GI tract have the highest capacity of carbohydrate absorption

Duodenum and upper jejunum

Glucose and galactose are absorbed via this mechanism

Sodium co-transport SGLT1; secondary active transport

Energy for the absorption of glucose and galactose is derived from this

Sodium-potassium ATPase (secondary active transport)

Fructose is absorbed via this transport mechanism

Carrier mediated facilitated diffusion GLUT5; passive transport

Basolateral transport of carbohydrates occurs via this mechanism

Facilitated diffusion (GLUT2)

Carbohydrates are only absorbed as this form

Monosaccharides

In the stomach, digestion of proteins occurs due to these two compounds

Pepsin and HCl

Trypsinogen is activated by this enzyme in the duodenum to form trypsin

Enteropeptidase

Trypsinogen is activated by enteropeptidase in this part of the GI tract to form trypsin

Duodenum

This organ secretes a trypsin inhibitor that prevents the activation of trypsinogen before it reaches the small intestine

Pancreas

What is the role of bile salts in the digestion and absorption of lipid?

Emulsify the large fat molecules

Colipase is released by this organ

Pancreas

This enzyme displaces bile salts from fat to acid pancreatic lipase in the digestion of fat

Colipase

This enzyme serves as a "receptor" for pancreatic lipase, since bile salts will inactivate lipase

Colipase

Colipase displaces these from fat, to pancreatic lipase in the digestion of fats

Bile salts (bile salts will inactivate lipase)

As fatty acids and monoglycerides are formed, they retain association with these to form micelles, within the intestinal lumen

Bile salts

As fatty acids and monoglycerides are formed, they retain association with bile salts to form these, within the intestinal lumen

Micelles

As fatty acids and monoglycerides are formed, they retain association with bile salts to form micelles, within this location

Intestinal lumen

This component of micelles surrounds the others and keeps the fats from recombining

Bile salts

This structure delivers fatty acids and monoglycerides through the unstirred layer

Micelles

This disrupts micelle arrangement

Lower pH at the membrane of the enterocyte

During lipid absorption, these are removed from micelles are recycled via the enterohepatic circulation

Bile salts

Bile salts are removed and recycled via the enterohepatic circulation, and are absorbed in this location

Distal ileum

Are micelles or chylomicrons formed in the intestinal lumen?

Micelles

Are micelles or chylomicrons formed within the enterocyte cell?

Chylomicrons

Once in the enterocyte, the fatty acids, monoglycerides, cholesterol and phospholipids and newly formed triglycerides are packaged into these

Chylomicrons

Once in this location, the fatty acids, monoglycerides, cholesterol and phospholipids and newly formed triglycerides are packaged into chylomicrons

Within the enterocyte

The chylomicrons are coated with apoprotein, and then are transported out this side of the enterocyte and into the lymphatics, to the liver for storage

Basolateral

The chylomicrons are coated with apoprotein, and then are transported out the basolateral side of the enterocyte and into this, to the liver for storage

Lymphatics

These fat soluble vitamins require micelles for absorption

A, D, E, and K2

This fat soluble vitamin is absorbed by an energy dependent, carrier-mediated process

Vitamin K1 (all other fat soluble vitamins require micelles)

These vitamins are absorbed directly into blood

Vitamins B and C (water soluble)

This is also known as Celiac disease or Gluten Enteropathy

Sprue

This is an adverse mucosal response to gluten Stunting of villi and a decrease in surface area for absorption

Sprue (Celiac disease)

This condition is due to inflammation of villi (bacterial, viral, parasite)

Tropical sprue

Does the colon have absorption function?

Yes absorption of water and electrolytes but nutrient absorption DOES NOT take place in the colon

Are there digestive enzymes in the colon?

Does nutrient absorption occur in the colon?

Does the small or large intestine have storage function?

Large intestine

Does the small or large intestine have longer transit time?

Large intestine

Does the small or large intestine have gradient in slow wave frequency?

Small intestine pacemakers are not organized in the large intestine

Does the small or large intestine have migrating motor complex?

Small intestine

Does the small or large intestine more frequently have retrograde movement?

Large intestine

Does the small or large intestine have mass movement?

Large intestine

Does the small or large intestine have continuous longitudinal muscle?

Small intestine

Does the small or large intestine have longitudinal muscle that is 3 discrete bands?

Large intestine

Mixing movements occur in this part of the colon

Proximal colon

Do mixing movements of the large intestine produce net movement?

No - no net movement

This type of contraction in the large intestine is a shuttle between adjacent haustra

Mixing movements

This type of contraction in the large intestine is slow segmental contractions Net movement down colon

Haustral contractions

Do haustral contractions of the large intestine produce net movement?

Yes - net movement down colon

This type of contraction in the large intestine occurs when large areas of colon contract Moves fecal material towards rectum Long bursts of spike potentials

Mass movements

Activation of these nerves relaxes (inhibitory) the internal anal sphincter via the release of VIP and nitric oxide

Parasympathetics

Activation of parasympathetic nerves relaxes (inhibitory) the internal anal sphincter via the release of these two molecules

VIP and nitric oxide

Activation of these nerves contracts the internal anal sphincter (excitatory)

Sympathetics

External anal sphincter receives excitatory innervation via this nerve

Pudendal nerve

Does the internal or external anal sphincter receive excitatory innervation via the pudendal nerve?

External anal sphincter

Does distention of the rectum relax or contract the internal anal sphincter?

Relax (with this, there is an increase in pressure on the external anal sphincter that wanes over time if defecation does not occur)

Does distention of the rectum relax or contract the external anal sphincter?

Contracts (continence)

Is voluntary relaxation of external anal sphincter necessary for defecation?

Yes

Is the defecation reflex good with liquids?

No good with solids but not liquids

The large intestine absorbs these three ions

Sodium, chloride and water

The large intestine secretes this ion

Bicarb

Is there substrate coupled Na+ transport in the colon?

Are there gap or tight junctions in the colon?

tight junctions much higher resistance to movement of molecules

Does the colon absorb Na+ against or along a concentration gradient?

Against

Absorption of sodium in the small intestine ceases when levels fall below this

130 mM

Is potassium secreted or absorbed when concentrations are below 15 mM in the colon?

Secreted occurs with chronic diarrhea or laxatives abuse; hypokalemia

Is potassium secreted or absorbed when concentrations are greater than 15 mM in the colon?

Absorbed

Is the normal state of potassium in the colon absorption or secretion?

Absorption (potassium is absorbed in exchange with H+)

Aspirin and alcohol are absorbed in part of the gut

Stomach

Calcium and iron are absorbed in part of the gut

Duodenum and jejunum

Water soluble vitamins are absorbed in part of the gut

Jejunum and ileum

Short chain fatty acids from bacteria are absorbed in this part of the gut

Colon

This type of diarrhea involves a decrease in surface area for reabsorption of water and electrolytes Related to inflammation of the mucosa of the small and large intestines (proteins, mucus, blood)

Inflammatory (exudative) diarrhea

This type of diarrhea involves a deficiency in the absorption of products of digestion in the small intestine For example, lactose intolerance, osmotic flow of water into the intestinal lumen

Osmotic diarrhea

Psychogenic diarrhea is probably related to activation of this

Parasympathetics

This type of diarrhea is related to bacterial infections of the crypts of small and large intestines E. coli and cholera toxin

Secretory (infectious) diarrhea

How do E. coli and cholera produce diarrhea?

1. stimulate cAMP to increase Cl- transport 2. Na+ and water follow to produce diarrhea

Congenital megacolon (Hirschsprung's disease) is due to an absence of this in the colon Areas of contraction in colon

Myenteric plexus

This is due to absence of myenteric plexus in colon; areas of contraction in colon

Congenital megacolon (Hirschsprung's disease)

This condition involves a spastic colon Altered bowel habit and abdominal pain in the absence of detectable structural abnormalities

Irritable bowel syndrome (IBS)

Are there structural abnormalities in Irritable bowel syndrome (IBS)?

Does this describe IBS or IBD: Usually fine at night but symptoms appear during wake hours So brain-gut link

Irritable bowel syndrome (IBS)

Is Irritable bowel syndrome (IBS) more prevalent in women or men?

Women (3x)

Is IBS or IBD related to brain-gut link?

Irritable bowel syndrome (IBS)

This is herniation of the mucosa and submucosa through the muscularis propria

Diverticulosis

This occurs when the mucosa in a diverticulum is perforated

Diverticulitis

Diverticulitis most often occurs in this part of the colon

sigmoid colon

Is diverticulitis diet related?

Yes; decreased in those with high fiber diets

Crohn's disease and ulcerative colitis are this type of disease

Irritable bowel disease (IBD)

Crohn's disease typically occurs in this part of the GI tract

Distal ileum or colon (although any region of gut can be involved)

This condition is characterized by ulcerations and inflammation involving the entire thickness of the gut wall Thickening of the intestinal mucosa (malabsorption and diarrhea)

Crohn's disease

Is Crohn's disease a type of IBS or IBD?

Irritable bowel disease (IBD)

This condition is inflammation of the colon with rectal bleeding Can involve the entire length of the colon

Ulcerative colitis

Does Ulcerative colitis involve the entire length of the colon?

Yes (unlike Crohn's)

Are perforations usually seen in ulcerative colitis?

Does Crohn's disease or ulcerative colitis involve the entire length of the colon?

Ulcerative colitis

After surgery to remove a diseased segment with Crohn's disease, can the condition re-occur at other areas?

yes