Lesuyai Organic Guides 2025
BIO201 – Topic 25: The Human Excretory System and
Osmoregulation
25.1 Introduction
The excretory system removes metabolic waste and regulates internal water and ion balance.
25.2 Definition of Excretion and Osmoregulation
Excretion removes metabolic wastes; osmoregulation maintains stable water and electrolyte balance.
25.3 Major Excretory Organs
Includes kidneys, liver, lungs, skin, and large intestine, each contributing to waste removal.
25.4 Structure of the Kidney
The kidney contains cortex, medulla, pelvis, renal vessels, and millions of nephrons.
25.5 Structure and Function of a Nephron
Nephron parts include Bowman's capsule, glomerulus, PCT, Loop of Henle, DCT, and collecting duct.
25.6 Processes in Urine Formation
Ultrafiltration, selective reabsorption, tubular secretion, and urine concentration.
25.7 Hormonal Regulation
ADH increases water reabsorption; aldosterone regulates sodium; RAAS controls blood pressure.
25.8 Disorders of the Excretory System
Kidney stones, UTIs, renal failure, gout, edema, and diabetes insipidus.
25.9 Summary
The excretory system is essential for waste removal and homeostasis through coordinated organ function.
25.10 Exam Questions with Answers
Q: 1. Define excretion.
A: Removal of metabolic waste products from the body.
Q: 2. What is osmoregulation?
A: Control of water and solute balance in the body.
Q: 3. Name two excretory products of the kidneys.
A: Urea and creatinine.
© Lesuyai Organic Guides 2025 | BIO201 – Topic 25
BIO201 – Topic 25: The Human Excretory System and
Osmoregulation
25.1 Introduction
The excretory system removes metabolic waste and regulates internal water and ion balance.
25.2 Definition of Excretion and Osmoregulation
Excretion removes metabolic wastes; osmoregulation maintains stable water and electrolyte balance.
25.3 Major Excretory Organs
Includes kidneys, liver, lungs, skin, and large intestine, each contributing to waste removal.
25.4 Structure of the Kidney
The kidney contains cortex, medulla, pelvis, renal vessels, and millions of nephrons.
25.5 Structure and Function of a Nephron
Nephron parts include Bowman's capsule, glomerulus, PCT, Loop of Henle, DCT, and collecting duct.
25.6 Processes in Urine Formation
Ultrafiltration, selective reabsorption, tubular secretion, and urine concentration.
25.7 Hormonal Regulation
ADH increases water reabsorption; aldosterone regulates sodium; RAAS controls blood pressure.
25.8 Disorders of the Excretory System
Kidney stones, UTIs, renal failure, gout, edema, and diabetes insipidus.
25.9 Summary
The excretory system is essential for waste removal and homeostasis through coordinated organ function.
25.10 Exam Questions with Answers
Q: 1. Define excretion.
A: Removal of metabolic waste products from the body.
Q: 2. What is osmoregulation?
A: Control of water and solute balance in the body.
Q: 3. Name two excretory products of the kidneys.
A: Urea and creatinine.
© Lesuyai Organic Guides 2025 | BIO201 – Topic 25
