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Ch. 19 Blood
Martini - Fundamentals of Anatomy and Physiology 12th Edition
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
All textbooksMartini, Nath, Bartholomew 12th EditionCh. 19 BloodProblem 31
Chapter 19, Problem 31

After Randy was diagnosed with stomach cancer, nearly all of his stomach had to be removed. Postoperative treatment included regular injections of vitamin B12. Why was this vitamin prescribed, and why were injections specified?

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1
Understand the role of vitamin B12 in the body: Vitamin B12 is essential for red blood cell formation, neurological function, and DNA synthesis.
Recognize that vitamin B12 absorption requires intrinsic factor, a protein secreted by parietal cells in the stomach lining, which binds to vitamin B12 and allows its absorption in the ileum.
Since Randy had nearly all of his stomach removed, the intrinsic factor production is severely reduced or absent, impairing the normal absorption of vitamin B12 from the diet.
Because oral vitamin B12 cannot be effectively absorbed without intrinsic factor, vitamin B12 injections are prescribed to bypass the gastrointestinal tract and deliver the vitamin directly into the bloodstream.
Therefore, the injections ensure that Randy receives adequate vitamin B12 to prevent deficiency-related complications such as pernicious anemia and neurological problems.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Role of Vitamin B12 in the Body

Vitamin B12 is essential for red blood cell formation, DNA synthesis, and neurological function. It is primarily absorbed in the ileum after binding to intrinsic factor, a protein produced by stomach cells. Deficiency can lead to anemia and neurological issues.
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Intrinsic Factor and Vitamin B12 Absorption

Intrinsic factor is a glycoprotein secreted by parietal cells in the stomach lining, necessary for vitamin B12 absorption in the small intestine. Removal of most of the stomach reduces intrinsic factor production, impairing B12 absorption and causing deficiency.

Rationale for Vitamin B12 Injections Post-Gastrectomy

After stomach removal, oral vitamin B12 cannot be absorbed effectively due to lack of intrinsic factor. Therefore, vitamin B12 is administered via injections to bypass the gastrointestinal tract, ensuring adequate levels and preventing deficiency-related complications.
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Textbook Question

In the disease mononucleosis ('mono'), the spleen enlarges because of increased numbers of phagocytes and other cells. Common signs and symptoms of this disease include pale complexion, a tired feeling, and a lack of energy sometimes to the point of not being able to get out of bed. What might cause these signs and symptoms?

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Textbook Question

A test for prothrombin time is used to identify deficiencies in the extrinsic clotting pathway; prothrombin time is prolonged if any of the factors are deficient. A test for activated partial thromboplastin time is used in a similar fashion to detect deficiencies in the intrinsic clotting pathway. Which factor would be deficient if a person had a prolonged prothrombin time but a normal partial thromboplastin time?

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Textbook Question

Almost half of our vitamin K is synthesized by bacteria that inhabit the large intestine. Based on this information, how could taking a broad-spectrum antibiotic for a long time cause frequent nosebleeds?

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