USMLE Step 1 Physiology Review 57 03 Stomach & Duodenum

USMLE Step 1 Physiology Review 57 03 Stomach & Duodenum

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Play USMLE Audio MP3 57 03 Stomach & Duodenum Below

Begin 57 03 Stomach & Duodenum Transcription

Okay now for some questions on the stomach. There are a number of different kinds of cells in the stomach that secrete different substances which in turn perform different functions. I will cue you with the function and you give the secreted substance and the cells that secrete it. This substance stimulates hydrochloric acid secretion, intrinsic factor secretion, pepsinogen secretion, and increases stomach motility?

  • Gastrin secreted by the G cells

This substance sterilizes stomach contents and optimizes pepsin function?

  • Gastric acid which is hydrochloric acid and it is secreted by the parietal cells

What are parietal cells also called?

  • Oxyntic cells

This substance binds to vitamin B12 for uptake?

  • Intrinsic factor abbreviated by IF and this is secreted by the parietal cells

This substance becomes pepsin in acid conditions and initiates protein digestion?

  • Pepsinogen secreted from chief cells

What are chief cells also called?

  • Peptic cells

This neutralizes acid protecting stomach walls by buffering the outermost layer of stomach contents?

  • Bicarbonate secreted by sub mucosal cells

This lubricates stomach contents and protects the stomach wall from acid?

  • Mucous secreted by mucous cells

Student doctor please pause the tape and summarize the information discussed on the stomach.

  • There are a number of different kinds of cells in the stomach that secrete different substances which in turn perform different functions. Gastrin secreted by the G cells stimulates hydrochloric acid secretion, intrinsic factor secretion, pepsinogen secretion, and increases stomach motility

Gastric acid, which is hydrochloric acid, is secreted by the parietal cells and sterilizes stomach contents and optimizes pepsin function. Parietal cells are also called Oxyntic cells. Intrinsic factor abbreviated by IF which is secreted by the parietal cells binds to vitamin B12 for uptake. Pepsinogen secreted from chief cells becomes pepsin in acid conditions to initiate protein digestion. Chief cells are also called Peptic cells. Bicarbonate secreted by sub mucosal cells neutralizes acid, protecting stomach walls by buffering the outermost layer of stomach contents. Mucous secreted by mucous cells lubricates stomach contents and protects the stomach wall from acid.

Now we’ll move on to the duodenum with the same format as above. I’ll cue you with the function performed by a given substance and you give the substance and the cells from which the substance is secreted. At the end of this, we’ll also talk about the substance that are secreted into the duodenum from the gallbladder and pancreas.

This substance stimulates hydrochloric acid secretion, intrinsic factor secretion, pepsinogen secretion, and increases stomach motility?

  • Gastrin from the G cells of the duodenum

This substance neutralizes acid, protecting stomach walls by buffering the outermost layer of stomach contents?

  • Bicarbonate secreted by sub mucosal cells

This substance stimulates gallbladder contraction, pancreatic secretion, and retards stomach emptying?

  •  Cholecystokinin or CCK secreted by the I cells of the duodenum

This substance stimulates bicarbonate secretion from the pancreas and inhibits gastric acid secretion?

  • Secretin from the S cells of the duodenum

This inhibits gastric acid secretion and stimulates insulin release?

  • Gastric Inhibitory peptide or GIP secreted from the neuronal cell bodies of the duodenum

Student doctor please pause the tape and summarize the information discussed so far on the duodenum and the substances secreted by the cells of the duodenum

  • Gastrin from the G cells of the duodenum stimulates hydrochloric acid secretion in the stomach, intrinsic factor secretion, pepsinogen secretion, and increases stomach motility. Bicarbonate secreted by sub mucosal cells neutralizes acid, protecting stomach walls by buffering the outermost layer of stomach contents. Cholecystokinin or CCK secreted by the I cells of the duodenum stimulates gallbladder contraction, pancreatic secretion, and retards stomach emptying. Secretin from the S cells of the duodenum stimulates bicarbonate secretion from the pancreas and inhibits gastric acid secretion. Gastric Inhibitory peptide or GIP secreted from the neuronal cells of the duodenum inhibits gastric acid secretion and stimulates insulin release.

Now we’ll move to pancreatic secretions. These are secretions from the pancreas.

This secretion buffers chyme entering from the stomach?

  • Bicarbonate.

This digests lipids?

  • Lipase

This digests complex saccharides?

  • Amylase

This pancreatic secretion digests proteins?

  •  Proteases

This inhibits gastric acid secretion, pepsinogen secretion, pancreatic secretion, inhibits gallbladder contraction and causes insulin release and glucagon release?

  • Somatostatin

Somatostatin comes from what time of cells?

  • The D cells of the pancreas

And where are these D cells also present?

  • In gastrointestinal mucosa

Student doctor please pause the tape and summarize the information discussed on pancreatic secretion.

  • These are secretions into the duodenum from the pancreas. Bicarbonate buffers chyme entering from the stomach. Lipase digests lipids. Amylase digests complex saccharides. Proteases digest proteins. Somatostatin, which comes from the D cells of the pancreas inhibits gastric acid secretion, pepsinogen secretion, pancreatic secretion, inhibits gallbladder contraction and causes insulin release and glucagon release. D cells are also present in the gastrointestinal mucosa.

Now we’ll move to gallbladder secretions. These emulsify lipids along with fat soluble vitamins for better digestion and absorption?

  • Bile salts

These are bile pigments?

  • Bilirubins

What are the two forms of fat secreted by the gallbladder?

  • Cholesterol and phospholipids

Student doctor please pause the tape and summarize the information discussed on gallbladder secretions

  • Bile salts emulsify lipids along with fat soluble vitamins for better digestion and absorption. Bilirubins are bile pigments. Cholesterol and phospholipids are the two forms of fat secreted by the gallbladder.

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