Normal pH of human blood?

Appeared in: BSF Staff Nurse - 2021

Explanation

The normal physiological pH of human arterial blood is tightly regulated between 7.35 and 7.45.
This range represents a slightly alkaline state, which is crucial for maintaining homeostasis and ensuring proper function of all enzymatic and cellular activities.
The option 7.34–7.45 is the only one that encompasses this critical range.
Venous blood is slightly more acidic (around 7.35) due to the presence of carbon dioxide from metabolic waste.

Option A: A pH range of 6.5–7.0 is acidic and falls into the category of severe acidosis, which is incompatible with life. Normal saliva can have a pH in this range, but not blood.
Option B: A pH range of 5.5–6.5 is highly acidic. This level of acidity in the blood would be fatal. This range is more typical for urine, which can vary widely to excrete excess acid from the body.
Option D: A pH range of 8.4–8.5 is highly alkaline (basic) and represents severe, life-threatening alkalosis. While some body fluids like pancreatic juice are alkaline, they do not reach this extreme level.

Clinical Relevance

Nursing practice connection: Knowing Normal blood pH and acid-base balance helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses frequently monitor a patient's acid-base status through Arterial Blood Gas (ABG) analysis, where pH is a critical parameter.
Clinical signs of acidosis include headache, confusion, and drowsiness, while alkalosis can present with lightheadedness, muscle twitching, and nausea.
Understanding normal pH is fundamental for managing patients with respiratory diseases, kidney failure, or metabolic conditions like diabetic ketoacidosis.

How to Approach the Question

This is a factual recall question that tests your knowledge of a fundamental physiological value.
First, identify the key concept in the question: 'Normal pH of human blood'.
Recall the specific, narrow range for blood pH from your studies. Remember that it is slightly alkaline.
Evaluate the given options. Eliminate any ranges that are clearly acidic (below 7.0) or excessively alkaline.
Option A (6.5-7) and B (5.5-6.5) are acidic. Option D (8.4-8.5) is extremely alkaline. This leaves only one plausible choice.
Select the option that matches the known physiological range of 7.35-7.45.

Concept Tested & Keywords

Qj2AWhW5q84Ijxa3rsJy8I

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 54-56

E6 Physiology Guyton 4SAE Part 2B p. 66-68

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