Excretion in Animals

Excretion in Animals

Introduction
While preparing a meal in the kitchen, several items such as food, water and charcoal or firewood are used. In the process, waste products such as peels, bones, dirty water and ash are produced. If these waste products are not cleared from the kitchen, they rot and produce a foul smell making the
kitchen unfit for its function and a breeding area for germs. In a same way, our bodies take in a lot of substances and are constantly using them to carry out processes to sustain our lives. Inevitably waste materials are produced. These need to be removed from the body. The removal of waste products of metabolism from the body is known as excretion. In this chapter, you will understand the different body organs that excrete different waste products. You will also be able to relate the organs of excretion in the human body to their functions. 3.1:

The Process of Excretion in Humans

The process of excretion in humans involves major body organs such as the skin, kidney, lungs and the liver. The waste products include; sweat, urine, carbon dioxide, excess salts, urea and excess water. In Activity 3.1, you will explore the process of excretion in humans

Do this activity in a group.
Key question: How does the process of excretion occur in humans?
What you need: Reference materials about excretion in humans, the Internet, a notebook a pen
What to do:

1. Discuss and;
   identify the organs of excretion and their different waste products i)
   of metabolism.
   ii) distinguish between waste products of metabolism and undigested waste.
2. What would happen if those excretory products were left to accumulate in the body?
3. Using reference materials or the Internet, research about the processes of excretion in humans, the organs and the excretions from those processes. Record our finding in the table below.

Compare your responses with those of another group.
3.2: Excretion in the Different Body Organs
In Activity 3.1, you were able to identify the different excretory organs and their respective waste products. In this section, you will understand how these waste products are excreted through these organs.

The skin is one of the excretory organs of the body. Through the skin, the body releases sweat which contains waste products. See Fig 3.1. In Activity 3.2, you will discover how waste products are eliminated through the skin.

Activity 3.2: Explaining the excretion process that takes place through the skin Do this activity in a group.
Key question: How are waste products eliminated through the skin?
What you need: Reference materials about a skin as an excretory organ, a notebook, a pen
What to do:

1. Your body works best when its temperature is about 370C. When your body gets hotter than that, a part of your brain known as the hypothalamus sends a message to your body telling it to sweat.
   i) Read about the skin and identify the part which produces sweat?
   ii) What do you think are the contents of sweat?
   iii) Explain how sweat is eliminated through the skin.
   iv) Why is it advisable for someone to bathe after doing a physical exercise?
   Discuss your responses with those of another group.

As discussed in chapter 1, lungs, see Fig 3.2; are a pair of spongy air filled organs located on either sides of the chest. Their main function is to enable oxygen that is breathed in to enter the red blood cells and then help the body to excrete carbon dioxide.
In Activity 3.3, you will find out how the lungs help in the process of carbon dioxide excretion.
Activity 3.3: Explaining how the body gets rid of carbon dioxide Do this activity in a pair
Key question: How is carbon dioxide eliminated from the body?
What you need: A chart or simulation showing a path taken by carbon dioxide from cells, manila charts. Those with visual impairments are encouraged to listen to the audio recordings.
What to do:

1. Watch a simulation video or study the diagram in the chart provided and discuss the following questions;
   i) What are the waste products in exhaled air?
   ii) What metabolic activity produces these waste products?
   iii) Describe how carbon dioxide produced in the cells is eliminated
   from the body.
2. What do you think would happen if carbon dioxide is left in the body cells where it is produced?
3. How does the body respond to high levels of carbon dioxide?
   Discuss your responses with the class and write down your conclusion.

Human beings have two kidneys located in the lower abdomen. The kidneys See Fig 3.3, are important excretory organs involved in the removal of nitrogenous waste products from the body. These nitrogenous wastes are excreted in the urine. In Activity 3.4, you will explain the structure and
functions of the kidneys

Activity 3.4: Explaining the structure and functions of the kidneys Do this activity in a pair.
Key question: How is the kidney adapted to its functions?
What you need: A well dissected mammal, reference materials about functions of a kidney, dissection kit, dissecting guide
What to do:

1. You are provided with a dissected animal. Locate the kidneys and;
   i) Note their shape and colour.
   ii) Locate the vessels that supply and drain the kidneys.
   iii) What is the function of the vessels that supply and drain the kidney?
   iv) Using reference materials or the dissecting guide, draw a longitudinal section of the kidney and label the blood vessels, pelvis, cortex and ureter.
   Compare your responses with those of another pair.
   The Nephron
   The kidney contains about a million specialized cells called nephrons. These are structures involved in urine formation. In Activity 3.5, you will draw and label a nephron.

Activity 3.5: Exploring the structure of a nephron
Do this activity individually
Key question: What are the major parts of a nephron?
What you need: Reference materials, the Internet
What to do:

1. Draw the nephron in your note book.
2. Using reference materials, label all the parts indicated in the figure below
3. Explain the function of each of the parts labeled.

3.3: Formation of Urine
Urine formation process is vital to humans because urine is the solution in which nitrogenous and other wastes are eliminated from the body.
Activity 3.6: Understanding the process of urine formation
Do this Activity in a group.
Key question: How is urine formed in the kidneys?
What you need: Reference materials about the process of urine formation, the Internet, a notebook, a pen
What to do:

1. Use reference materials or the Internet to read about the process of urine formation. From your findings:
   i) What is meant by ultrafiltration?
   ii) What factors are required for ultrafiltratin to occur?
   iii)In which part of the nephron does ultrafiltration occur?
   After ultrafiltration, some substances are removed from the solution back into the blood. Why do you think those substances are reabsorbed into the blood?
   iv)Which hormone aids the process identified in (iv) above?
   iv)How does the length of the loop of henle affect the process in above?
   Share your responses with the whole class.

3.4: Kidney Failure
What do you think will happen when kidneys fail to perform their functions? Kidney failure occurs when the kidneys are unable to remove wastes and balance fluids in the body. In Activity 3.7. You will identify the causes, symptoms and treatment of kidney failure.
Activity 3.7: Interviewing a health professional about the causes, symptoms and treatment of kidney failure?
Do this activity as a class
Key question: What are the causes, symptoms and treatment of kidney failure?
What you need: A note book, a pen, questionnaire
What to do:

1. Visit a nearby health facility or interview a health professional invited to your class about the causes, symptoms and treatment of kidney failure. Present your findings in the table below.

2. What health habits can be developed to reduce chances of having kidney failure?
   3.5: Glucose and Proteins in Human Urine
   In senior two, you learnt about the class of carbohydrates to which glucose belongs and the procedure for testing for the presence of reducing sugars and proteins.
3. Human urine contains different types of substances. Presence or absence of some substances such as proteins and glucose can be used to tell the health status of an individual. In Activity 3.8, you will find out the need for testing for reducing sugars and proteinosis human urine.
   Activity 3.8: Finding out the need for tests to determine the presence of glucose and proteins in human urine
   Do this activity in a group.
   Key question: Why is it necessary to carry out tests for proteins and glucose in urine?
   What you need: A notebook, reference materials about glucose and proteins in human urine, the Internet, a pen
   What to do:
4. Discuss the circumstances that might lead to the presence of glucose and proteins in urine.
5. Research and explain how one would test for the presence of glucose and proteins in urine.
6. What would a positive result mean?
7. Explain the importance of testing for presence of glucose and proteins in the human body.
8. Using reference materials or the Internet, find out the health habits one can adopt to maintain normal glucose and protein levels. Compare your findings with those of another group.

Compare your findings with those of another group.

3.6: Disposal of Urine
How is urine disposed in your school? Just like other human waste, proper disposal of human urine is important to keep the environment clean and healthy. Urine can be wasted or put to use. In Activity 3.9, you will explore and recognize the need for proper disposal of urine.
Activity 3.9: Exploring proper urine disposal
Do this a activity in a group.
Key question: How can urine be disposed properly?
What you need: A notebook, a pen
What to do:

1. What are the possible hazards of poor urine disposal?
2. Discuss the proper ways of disposing urine in your school.
3. Discuss how urine can be put to use?
   Compare your conclusions with those of another group.

In this chapter, you have learnt that:
The process of excretion in humans involves the organs like the skin, kidneys, lungs and the liver. These organs make up the excretory system and the waste products of excretion include urine, sweat, carbon dioxide, excess salts, urea, and excess water Urine formation is a vitalprocess in humans because through
it nitrogenous and other waste substances are eliminated from the body Kidney failure occurs when the kidneys are unable to perform their functions of removing wastes and balancing body fluids
Proper urine disposal is important to safeguard human, animal and plant health as well as keep the environment clean.

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