Excretion
Overview
Every metabolic reaction in your body generates waste. Some of these waste products are toxic and must be removed before they accumulate to dangerous levels. Excretion is the process that gets rid of them, and the kidneys are the organs that do most of the heavy lifting, filtering your entire blood volume roughly 40 times every day.
In this lesson you will learn what excretory products the body makes and which organs remove them, how the nephron filters blood and produces urine, and how ADH regulates the water content of the blood. Kidney function is a favourite topic for structured questions on both Paper 1 and Paper 2.
Objectives
- Understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf
- Know the excretory products of the lungs, kidneys and skin (organs of excretion)
- Understand how the kidney carries out its roles of excretion and osmoregulation
- Describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra
- Describe the structure of a nephron, including the Bowman's capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct
- Describe ultrafiltration in the Bowman's capsule and the composition of the glomerular filtrate
- Understand how water is reabsorbed into the blood from the collecting duct
- Understand why selective reabsorption of glucose occurs at the proximal convoluted tubule
- Describe the role of ADH in regulating the water content of the blood
- Understand that urine contains water, urea and ions
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Excretion. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Where is urea produced? A) Kidneys B) Liver C) Lungs D) Bladder Answer: B
- Which process forces small molecules out of the blood in the glomerulus? A) Osmosis B) Active transport C) Ultrafiltration D) Diffusion Answer: C
- Glucose is reabsorbed in the proximal convoluted tubule by: A) Diffusion B) Osmosis C) Ultrafiltration D) Active transport Answer: D
- When a person is dehydrated, what happens to ADH levels? A) They increase B) They decrease C) They stay the same D) ADH is not involved Answer: A
- Which substance should NOT be found in the urine of a healthy person? A) Urea B) Water C) Glucose D) Ions Answer: C
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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