Grade 11 life sciences: Excretory system

Introduction

Welcome to the life science webquest, students in grades 11. Today we will begin a new topic, the excretory system. we going to focus on human excretion 

Task

We'll work separately owing to COVID 19 restrictions, as well as to ensure that each of you understands because you'll all be providing input.

The practical consist of part and and part two

Part 1: You are required to do a model of dissection of sheep kidney (18)

PART 2: 

The main functions of the kidney is to help to maintain homeostatic control in the body. The table below compares the concentration of different substances: blood plasma, the filrate in Bowman’s capsule and urine in a person

Substance

Glomerular filtrate

(g/100cm^3)

Glomerular plasma

(g/cm^3)

Urine (g/100cm^3

protein

0

7.00

0

glucose

0.10

0.10

0

Uric acid

0.002

0.002

0.03

sodium

0.32

0.32

0.60

phosphates

0.003

0.003

0.18

sulphates

0.003

0.003

0.12

water

98.00

92.00

96.00

urea

0.03

0.03

2.0

 

 

2.1 Name two substances, other than those listed in the table, that may be present in urine (2)

2.2 briefly explain why:

2.2.1 glucose is present in the glomerular filtrate but absent in the urine (2)

2.2.2 in some cases glucose may appear in the urine (2)

2.2.3 no protein is found in the filtrate even though it is present in the blood plasma (2)

2.3 suggest a reason for the increased concentration of urea in urine (2)

2.4 account for the high percentage of phosphates and sulphates in the urine compared to the glomerular filtrate (2)

                                                                                                                              12 marks

Total 30 marks



 

Process

 

Practical Examination

Part 1: Dissection of sheep kidney

  1. Each learner must collect a kidney specimen from the teacher
  2. Also ensure you have all relevant equipment and materials for this activity e.g, newspaper, dissecting board, scalpel, etc.
  3. Prepare the specimen appropriately and then do a longitudinal dissection of the kidney.
  4. Identify and label the following parts: cortex, pyramid, calyx, pelvis, and papilla
  5. Draw and label what you observe.

Part 2: answer all questions

Evaluation

part 1

RUBRIC

  1. DISSECTION OF PART 1

The following criteria can be used to assess this skill

 

Criteria

Suggested mark scheme

1

Getting started:

Was the dissecting used?

Was the newspaper placed on the dissection board?

Did the learner remove the fat from around the kidney?

 

 

1

1

 

1

2

Cutting of specimen:

Longitudinal section made

1

3

Neatness of dissection

  • Perfect with all parts clearly visible and no mutilation
  • Most parts clearly visible but some no mutilation
  • Specimen badly mutilated and parts not clearly

 

4

 

2

 

0

 

  1. Drawing from the specimen

 

Criteria

Suggested mark scheme

1

Correct representation:

Does the drawing resemble the dissected specimen.

1

2

Caption:

Does it have heading

1

3

Magnification:

Is this indicated in the caption of the drawing

1

4

Labels correctly in the caption representing parts:

Cortex

Medulla

Pyramid

Calyx

Pelvis

Papilla

Any 5

5

5

Biological drawing requirements:

Are the position of parts correct?

Are the parts drawn in appropriate proportion to one another?

1

1

Part 2:

2.1. Creatinine in humans and hippicuric acid in herbivorous animals

2.2.

2.2.1. Glucose is conserved because it is used for energy in the body and is reabsorbed in the loop of Henle.

2.2.2. Glucose may appear in the urine because:

  • There is kidney malfunction.
  • The pancreas is failing to produce insulin, or the body is resistant to insulin and so glucose is not taken up to the body cells.

2.2.3. Protein molecules are too large to pass through the pores in the endothelial layer in Bowman’s capsule.

2.3. Large amounts of protein in the diet result in deamination in the liver resulting in the production of urea and so to the concentration of urea in the blood and urine rises.

2.4. This is the result of tabular excretion. These substances are acidic salts and are actively taken out of the blood and added to the filtrate. Their excretion maintains the slightly alkaline medium in the blood.

 

Conclusion

 

As every learner will be doing the assessment individually, make sure you put an effort to your work because it will be contributing to the term mark. 

 

Credits

Teacher Page

                                                INTRODUCTION

Teachers activity                                                   Learners possible answers

What is excretion

  • nd maintain acid-base balance Excretion, the process by which animals rid themselves of waste products and of the nitrogenous by products of metabolism. Through excretion organisms control osmotic pressure the balance between inorganic ions and water ae.

  • Removal of waste product out of the body

  • Removal of urinary out of body

                                                        DEVELOPMENT

  • Certain waste and harmful substances are formed during the functioning of body cells.  When these toxic materials are not removed from the body, they get mixed with blood and can damage the cells of the body. The removal of such poisonous waste materials is therefore necessary.

  • Gut: function is the digestion, absorption of nutrients and the excretion of waste.

  • Skin: The skin plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea, a byproduct of protein catabolism.



 

  • Kidney and bladder: The kidneys make urine by filtering wastes and extra water from blood. Urine travels from the kidneys through two thin tubes called ureters and fills the bladder. When the bladder is full, a person urinates through the urethra to eliminate the waste

Liver: regulates most chemical levels in the blood and excretes a product called bile. This helps carry away waste products from the liver. Production of bile, which helps carry away waste and break down fats in the small intestine during digestion. Production of certain proteins for blood plasma.

Lungs: The lungs are responsible for the excretion of gaseous wastes, primarily carbon dioxide from cellular respiration in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases

  • Homeostasis is the body's attempt to maintain a constant internal environment. One of the major ways the body achieves homeostasis is through excretion, the process of removing wastes and excess water from the body. Most of the mechanisms that control homeostasis in the human body involve negative feedback.

  • Chronic kidney disease. The most common form of kidney disease is chronic kidney disease.

  • Kidney stones. Kidney stones are another common kidney problem.

  • Glomerulonephritis

  • Polycystic kidney disease.

  • Urinary tract infections