Physiology of Blood and Sweat pH

Normal arterial blood pH averages 7.4, with a range between 7.35 and 7.45.
Maintaining blood pH is essential for proper body function, primarily regulated by the carbonic acid (H2CO3) – bicarbonate ion (HCO3-) buffer system.

Human sweat typically has a pH ranging from 4.5 to 7.0, making it slightly acidic to neutral.
Factors influencing sweat pH include hydration, diet, and environmental conditions.
Lactic acid and urea in sweat contribute to its acidity, which helps protect the skin from bacteria.

Normal urine pH falls between 4.6 and 8.0, with an average of around 6.0, indicating slight acidity.
Urine pH varies based on dietary intake and overall health; high protein diets produce more acidic urine, while fruit and vegetable-rich diets lead to more alkaline urine.

Normal semen pH ranges from 7.2 to 8.0, making it slightly alkaline.
This alkalinity helps sperm survive in the acidic environment of the female reproductive tract, crucial for sperm motility and fertility.

Human gastric juice is highly acidic, with a pH ranging from 1.5 to 3.5, primarily due to hydrochloric acid (HCl).
This acidity is vital for digestion, enzyme activation, and killing harmful bacteria.

Normal saliva pH ranges from 6.2 to 7.6, which is slightly acidic to neutral.
This pH range supports oral health and the initial stages of digestion while providing a protective environment against bacteria.

A Bronsted-Lowry acid donates protons (H+ ions) to other compounds, while a Bronsted-Lowry base accepts protons.
Water can act as both an acid and a base, exhibiting amphiprotic properties by dissociating to produce H3O+ and OH- ions.

pH is a quantitative measure of the acidity or basicity of a solution.
Buffers resist changes in pH when acidic or basic components are added, playing a critical role in biological systems.

Acidosis refers to excessive acidity in body fluids, primarily the blood.
Common causes include:
- Respiratory issues that hinder proper exhalation, leading to CO2 and H+ buildup.
- Metabolic disorders that affect the function of buffers or promote acid production.
Conditions like severe diarrhea can lead to bicarbonate loss and increased acidity.
Diabetic ketoacidosis arises from ketone accumulation in poorly managed diabetes.
Kidney, liver, heart failure, and cancer can also induce metabolic acidosis.