Unit D

Module 8 ~ Lesson 5


In this lesson, you explored the following questions:

  • How do the kidneys contribute to homeostasis in terms of water and ions?
  • How does the design of the kidney relate to dialysis technologies?

The kidneys maintain the water-salt balance in the body. Water balance is maintained when the body senses osmotic pressure via osmoreceptors. High or low pressures stimulate or inhibit the release of antidiuretic hormone (ADH). ADH causes the collecting ducts and distal tubules to become more permeable to water, thereby helping the body to conserve water when necessary.

Another hormone, aldosterone, regulates the amount of salt in the body by reabsorbing sodium ions. Aldosterone increases the permeability of the collecting duct and distal tubules for sodium ions. Urinalysis can be used as a tool to determine health conditions. Dialysis is when blood is filtered using principles of diffusion either internally (using your intestine) or externally (being hooked up to a machine).

Lesson Glossary

aldosterone: a hormone that causes the tubules of the kidneys to retain sodium and water; increases the volume of fluid in the body, and drives up the blood pressure.

antidiuretic hormone: a hormone in all mammals that stimulates increased water reabsorption by the kidneys; also called vasopressin

dehydration: a relative deficiency of water molecules in relation to other dissolved solutes; can be caused by blood loss, vomiting, excess exertion, or malnutrition

diabetes insipidus: a condition characterized by the excretion of large amounts of severely diluted urine; which cannot be reduced when fluid intake is reduced; It denotes an inability of the kidney to concentrate urine; caused by a deficiency of antidiuretic hormone (ADH), also known as vasopressin.

hypothalamus: a gland located above the brain stem and connects the nervous system with the endocrine system by relaying messages to the pituitary gland; it is the size of an almond

osmoreceptors: a sensor found in the hypothalamus of the brain that detects changes in osmotic pressure


Complete Unit D: Section 6 Assignment now.