Most of the body's calcium is found in :

IGNOU PB Bsc Entrance-2023

Applied Physiology

Easy

Appeared in: IGNOU PB Bsc Entrance-2023

Explanation

The vast majority, approximately 99%, of the body's total calcium is stored within the bones and teeth.
Bones serve as a large, dynamic reservoir for calcium, releasing it into the bloodstream when levels are low and taking it up when levels are high.
This storage function is critical not only for providing structural integrity to the skeleton but also for maintaining calcium homeostasis throughout the body.
The small fraction of calcium outside the bones is vital for functions like muscle contraction, nerve signaling, and blood clotting.

Option A: While teeth are hard structures containing calcium, their total mass is far less than that of the entire skeleton. Therefore, they hold only a small fraction of the body's total calcium compared to bones.
Option C: Intracellular fluid (the fluid within cells) contains only about 1% of the body's total calcium. While crucial for cell signaling, it is not the primary storage site.
Option D: Extracellular fluid (including blood plasma) contains a very small amount of calcium, typically less than 0.1% of the total. This concentration is tightly regulated but represents a tiny fraction of the body's total calcium stores.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calcium distribution and homeostasis in the human body as background academic context rather than a clinical decision trigger.
Understanding that bones are the main calcium reservoir is fundamental for managing conditions like osteoporosis, hypoparathyroidism, and chronic kidney disease, which all affect calcium balance.
Nurses must monitor serum calcium levels and be vigilant for signs of imbalance. For example, a patient post-thyroidectomy is at risk for hypocalcemia due to potential parathyroid gland damage, requiring close observation for tetany (Trousseau's and Chvostek's signs).
What if a patient has a tumor that secretes parathyroid hormone-related peptide (PTHrP)? This would lead to excessive calcium release from the bones, causing severe hypercalcemia. The nursing priority would shift to managing hypercalcemia symptoms (lethargy, confusion, cardiac arrhythmias) and promoting calcium excretion through hydration.

How to Approach the Question

First, identify the key term in the question: 'Most of'. This indicates the question is asking for the location with the largest quantity.
Next, analyze the options provided: teeth, bones, intracellular fluids, and extracellular fluids.
Recall basic physiological knowledge about mineral storage in the body. Minerals that provide structural support, like calcium, are typically stored in large amounts in hard tissues.
Compare the options. The entire skeleton (bones) is a massive system compared to teeth. Fluids (intra- and extracellular) contain dissolved substances for immediate use, not long-term bulk storage.
Conclude that the bones, which constitute the bulk of the skeletal system, are the logical site for storing the majority of the body's calcium.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2B pp. 62-64, 61-63

E6 Medicine Harrison 22e Part 2 p. 1165-1167