digestive system

Pancreatic enzymes function optimally in a pH range of:

6-7

physiological circumstance most likely to increase the amount of circulating leptin A) increased fatty acid production B) increased fatty acid breakdown C) increased blood glucose levels D) fasting for longer than 6 hours

A

Leptin

A hormone produced by adipose (fat) cells that acts as a satiety factor in regulating appetite.

intrinsic factor

A substance produced by the mucosa of the stomach and intestines that is essential for the absorption of vitamin B12 and water to dilute the bolus

fat soluble vitamins

A, D, E, K

Which of the following essential vitamins can be eliminated through the urinary system?

B and C

water soluble vitamins

B and C

Which of the following hormones regulate(s) appetite? Select all that apply. A) gastrin B) ghrelin C) leptin D) secretin E) cholecystokinin (CCK)

B,C,E

the relationship between villi, microvilli, and enterocytes

Enterocytes are the epithelial cells that make up the small intestine. Because villi are tiny folds of the small intestine's epithelial surface, each villus is composed of hundreds of enterocytes. Microvilli are microscopic hair-like extensions of each enterocyte's cell membrane.

(T or F) The primary role of bile salts is to chemically digest lipids

FALSE! They are not enzymes, they break down large triglycerides mechanically into smaller micelles through emulsification. Lingual and pancreatic lipases are responsible fo the chemical digestion (hydrolysis of triglycerides)

True or false: Pepsin hydrolyzes proteins and peptides in the stomach to generate amino acids.

FALSE. Pepsin begins the process of protein digestion in the stomach. It breaks down larger proteins into peptides. Peptides are not typically broken down into individual amino acids until they come into contact with pancreatic proteases and brush border peptidases in the small intestine.

True or false: Cholecystokinin works synergistically with glucagon to promote the feeling of hunger in response to fasting.

False. Cholecystokinin is a hormone that stimulates digestive processes in response to feeding and consequently promotes satiety rather than hunger. It also tells the gallbladder to release bile from storage and stimulates the release of pancreatic enzymes that break down carbohydrates, proteins, and lipids.

True or false: Although its primary role is nutrient breakdown, the stomach also functions in the absorption of several key macronutrients.

False. The stomach produces gastric acid and several key enzymes involved in nutrient digestion, but it does not directly absorb any of the major macronutrients (proteins, carbohydrates, fats, and nucleic acids).

Helicobacter pylori is a bacterium that has evolved to thrive in the harsh acidic environment of the human stomach. H. pylori infections are asymptomatic in 80% of cases, but can sometimes cause serious conditions like gastritis, gastric ulcers, and stomach cancer. What makes this microorganism so dangerous?

H. pylori can burrow under the protective mucous layer that coats the stomach lining to reach endothelial cells. Once there, these bacteria can irritate stomach tissue, giving rise to a variety of gastric disorders.

what vitamins are synthesized by bacteria in the large intestine?

K and B7

lacteals

Lacteals connect the digestive system to the lymphatic system, which empties into venous circulation. This is where chylomicrons pass to reach into systemic circulation

Vitamin D function

Regulation of calcium and phosphate concentrations in the bloodstream

brush border

Surface of a cell covered with microvilli. increases surface area of a cell for absorption

True or false: Parasympathetic input to the enteric nervous system causes dilation of the blood vessels that supply blood to the gastrointestinal tract.

True. The enteric nervous system is a branch of the autonomic nervous system that responds to both sympathetic and parasympathetic input. Parasympathetic activity promotes "rest and digest" functions, including the dilation of blood vessels supplying the digestive system. This allows blood to be shunted toward digestive organs.

Required for collagen synthesis

Vitamin C

True or false: Bile salts are amphipathic molecules that associate with lipids in the aqueous environment of the duodenum. By preventing the exposure of lipid surface area, they facilitate the action of water-soluble lipases.

While the first sentence is correct, the second sentence is not. Bile salts actually generate more lipid surface area through a process called emulsification. This makes fat globules more accessible to water-soluble lipases, which chemically digest lipids.

The lower esophageal sphincter

a band of muscle that separates the esophagus from the stomach and opens to allow food to pass into the stomach

gastrin

a hormone released by specialized cells in the stomach and promotes gastric acid production.

enterocytes

absorptive epithelial cells that line the walls of the small intestine

calcitriol

active form of vitamin D

why is trypsin secreted from the pancreas as an inactive zymogen

active proteases can cleave pancreatic proteins, resulting in pancreatitis

absorbed through secondary active transport

amino acids and some monosaccharides

enteropeptidase cleaves peptide bonds adjacent to

arginine or lysine residues, to activate a suite of proteases

Secretin stimulates digestion by promoting the release of

bicarbonate

mucous epithelial cells secrete

bicarbonate to neutralize the lining of the stomach

functions of the liver

bile production, storage, detoxification, fatty acid mobilization, glycogen metabolism, drug metabolism

vitamin K is essential for

blood clotting

The enteric nervous system

branch of autonomic NS, independent of para/sympathetic controls everything in GI tract, pancreas, and gall bladder 2 networks: 1. myenteric plexus- controls gut motility 2. submucosal plexus- controls blood flow, enzyme secretion, ion exchange

Epithelial cells of the small intestine secrete ________ which hydrolyze disaccharides into monosaccharides

brush border disaccharidases

How is pepsinogen converted to pepsin?

by HCl, hydrolyzes peptide bonds between hydrophobic or aromatic amino acids, so it has enough specificity to cleave peptides without converting them into individual amino acids in the stomach

the 3 main segments of the large intestine

cecum, colon, rectum

which hormone functions both in digestion and appetite regulation?

cholecystokinin (CCK)

Fatty acids absorbed by enterocytes enter circulation after being packaged into:

chylomicrons

Enterocytes secrete

disaccharidases and peptidases

pylorus

distal region of the stomach, opening to the duodenum

which organs/tissue types synthesize and release digestive hormones?

duodenum, pancreas, stomach G cells, adipocytes

trypsinogen is activated by

enteropeptidase

T or F: epithelial cells of the stomach produce pepsin and intrinsic factor, which have anti inflammatory properties.

false

True or false: Food moves from the mouth into the stomach by peristalsis, which refers to the wave-like contractions of skeletal muscle lining the entire length of the esophagus.

false

T or F: lactose intolerance is an autoimmune reaction

false lactose is not a body cell the immune system can attack

True/false: Dietary fatty acids enter the bloodstream immediately after absorption in the small intestine.

false. Chylomicrons are shunted into lacteals, which eventually empty into the bloodstream

The liver converts excess glucose and amino acids into

fatty acids

Which of the following molecules enter enterocytes in the small intestine via passive diffusion? A) fatty acids B) amino acids C) monoshaccharides D) triglycerides

fatty acids, because they are small and hydrophobic

anal sphincter

final sphincter of the digestive tract; separates the rectum and anus and allows the elimination of feces

duodenum

first section of the small intestine

Gastrin promotes digestion by stimulating the secretion of

gastric acid

G cells secrete

gastrin

pro-digestion hormones

gastrin, CCK, secretin

Coenzymes are a subcategory of cofactors that

have a complex organic structure

parietal cells secrete

hydrochloric acid

Which digestive organ hosts the largest community of bacteria in the human body?

large intestine

ileum

last part of small intestine

After a meal, high levels of what hormone suppress appetite and promote digestion?

leptin and cholecystokinin

macrominerals

minerals that the body needs in fairly large amounts such as calcium, sodium, and potassium.

all of the organs that play a role in carbohydrate digestion

mouth, pancreas, small intestine

cardiac sphincter

opening from the esophagus to the stomach

pyloric sphincter

opens to allow chyme to flow into the duodenum of the small intestine.

cecum

part of the large intestine, a pouch connected to the junction of the ileum at the ileocecal sphincter

chief cells secrete

pepsinogen

hepatic portal system function

pick up digested nutrients from enterocytes; delivers them to liver for processing & storage

Which macromolecules are NOT digested in the stomach?

polysaccharides, lipids, triglycerides, amino acids

somatostatin

prevents release of insulin & glucagon, inhibits secretion of pro-digestive enzymes (CCK, secretin, gastrin), stalls digestion, and inhibits the growth hormone

Where is bile produced and stored?

produced in the liver and stored in the gallbladder

Fasting refers to the metabolic state achieved after 8-12 hours have elapsed since a person's last meal. It is characterized by low blood glucose levels and elevated levels of circulating fatty acids. By this logic, fasting most likely:

promotes appetite and inhibits digestion

functions of the stomach?

protein digestion Aiding in vit B12 absorption

the success of gastric bypass surgery can be explained by

removal of upper portion of the stomach means less ghrelin is secreted to stimulate appetite and signal hunger

vitamin A is also known as _______ and is essential for

retinol; low light vision

iologists have argued that the gastrointestinal tract can be viewed as an outgrowth of the immune system. What are the immune functions of the digestive system?

saliva contains lysozyme, which kills bacteria stomach pH is so low that many pathogens don't survive

saliva contains what type of enzymes

salivary amylase -> breaks down lingual lipase -> breaks down lipids lysozyme -> kills bacterial

Which of the following answer choices best characterizes the transport mechanism through which glucose molecules move into enterocytes from the lumen of the small intestine?

secondary active transport

S cells secrete

secretin (duodenum)

Ghrelin

signals hunger

vitamin D can be synthesized in the

skin, using UV light

Cholesystokinin is secreted by

small intestine

What lines the esophagus?

smooth muscle

Roles of Cholecystokinin (CCK)

stimulates release of bile from the gallbladder stimulates the release of digestive enzymes from the pancreas inhibits hunger

Role of secretin

stimulates the pancreas to secrete bicarbonate-rich pancreatic juice into the duodenum. This results in a pH around 6-7 in the duodenum, which is much more optimal for the function of pancreatic enzymes

carbohydrates are mechanically digested in the

stomach

The capillaries of the small intestine drain into

the hepatic portal vein

in the large intestine, water moves from

the intestinal lumen into epithelial cell

jejunum

the middle portion of the small intestine; longest part

fundus

top of the stomach

pancreatic lipase breaks down

triglycerides into fatty acids and monoglycerides

True or false: Lacteals are small vessels that drain directly into the lymphatic system. They conduct chylomicrons from enterocytes into systemic circulation.

true

Ghrelin is secreted by

upper stomach and pancreas

pancreatitis happens when

zymogens become active and start digesting pancreatic proteins that make up the pancreas itself