1. LEARNING SCIENCE THROUGH ACTIVE LEARNING 4 th Comenius Project Meeting June 2013 LEARNING SCIENCE THROUGH ACTIVE LEARNING 4 th Comenius Project Meeting June 2013 C OLLABORATIVE LEARNING AS ACTIVE LEARNING METHOD

2. The Human Excretory System “TUDOR VIANU” SECONDARY SCHOOL GIURGIU

3. The aim of the lesson: To emphasize the structural and functional particularities of the kidney and urinary tract for a better understanding of the process of excretion, the removal of toxic waste produced by the metabolism of the cells. Objectives: Identify and describe the structure of the excretory system organs to explain the relationship between structure and functionIdentify and describe the structure of the excretory system organs to explain the relationship between structure and function Explain the nephron’s structural features as a morphofunctional unit of the kidneyExplain the nephron’s structural features as a morphofunctional unit of the kidney Graphical representation of the excretory system componentsGraphical representation of the excretory system components The proper usage of terms specific to biologyThe proper usage of terms specific to biology Underline the importance of excretion for people’s healthUnderline the importance of excretion for people’s health Teaching methods: Conversation, experiment, observation, demonstration, shaping Material resources: For every group of students: pig kidneys, dissection case, eye-glass, microscope, and worksheet For the whole class: excretory system sketch, human body model, kidney model, images

4. Lesson’s evolution: The lesson starts with the students being asked questions which lead them to a better understanding of the excretory function. Previously learnt knowledge will be used in order to study of the following functions: digestion and absorption, circulation and respiration. The following questions can be used to start the conversation: Which are the vital substances for a proper functioning of the organism? Which are the vital substances for a proper functioning of the organism? How does the human body secure such substances? Which functions are used? How does the human body secure such substances? Which functions are used? How do the nutrients get to the body cells? How do the nutrients get to the body cells? Answering the questions above will make the students use the previously studied knowledge in a new context. Mentioning these problems will implicitly lead to debating the possibility of removing the toxic products resulted from burnings and cell activity. Mentioning these problems will implicitly lead to debating the possibility of removing the toxic products resulted from burnings and cell activity.

5. In this situation, the teacher asks the students use what they know, offering them the opportunity to make new analogies and correlations. Pictures, drawings and molds are used in order to highlight the excretory system components and their structural features. The students are asked to observe kidney components, firstly with naked eyes and then with a magnifying glass. Based on discussions with the whole class, conclusions are drawn and the components of the excretory system and kidney composition are written on the blackboard and in the notebooks. To study the nephron, we use a mold and some images which illustrate the structural components. There are created the necessary elements for understanding the process of urine in the nephron. These explanations and presentations highlight the correlation between the structure and functioning of the nephron components.

6. Excretory System The kidneys regulate the amount of water, salts and other substances in the blood. The kidneys are fist-sized, bean shaped structures that remove nitrogenous wastes (urine) and excess salts from the blood. The ureters are tubes that carry urine from the pelvis of the kidneys to the urinary bladder. The urinary bladder temporarily stores urine until it is released from the body. The urethra is the tube that carries urine from the urinary bladder to the outside of the body. The outer end of the urethra is controlled by a circular muscle called a sphincter.

7. Excretory System

8. The Kidney Each kidney is composed of three sections: the outer (renal) cortex, the (renal) medulla (middle part) and the hollow inner (renal) pelvis. The cortex is where the blood is filtered. The medulla contains the collecting ducts which carry filtrate (filtered substances) to the pelvis. The pelvis is a hollow cavity where urine accumulates and drains into the ureter.

9. How blood is Filtered The filtering units of the kidneys are the nephrons. There are approximately one million nephrons in each kidney. The nephrons are located within the cortex and medulla of each kidney. The tubes of the nephron are surrounded by cells and a network of blood vessels spreads throughout the tissue. Therefore, material that leaves the nephron enters the surrounding cells and returns to the bloodstream by a network of vessels.

10. Parts of the Nephron Each nephron consists of the following parts: –1) glomerulus ; –2) Bowman’s capsule ; –3) proximal tubule ; –4) loop of Henle ; –5) distal tubule ; –6) collecting duct.

11. The Glomerulus The glomerulus is a mass of thin-walled capillaries. The Bowman’s capsule is a double-walled, cup-shaped structure. The proximal tubule leads from the Bowman’s capsule to the Loop of Henle. The loop of Henle is a long loop which extends into the medulla. The distal tubule connects the loop of Henle to the collecting duct.

12. How the kidney does its job! Kidney Action Blood enters Bowman’s capsule through a tiny artery — (the renal artery). The artery branches to form a glomerulus. Blood pressure forces some blood plasma and small particles into the surrounding capsule — (this is called the nephric filtrate). Large particles such as blood cells and proteins remain in capillaries. The nephric filtrate is pushed out of the capsule and into the proximal tubule. This is where reabsorption begins.

13. Kidney action Only materials needed by the body are returned to bloodstream — for example, 99 % of water, all glucose and amino acids and many salts are reabsorbed. Osmosis, diffusion, and active transport draw water, glucose, amino acids and ions from filtrate into surrounding cells. Small villi like projections help in the active transport of glucose out of the filtrate and speed up the reabsorption process. From here, these components return to the bloodstream.

14. Kidney action The filtrate reaches the end of the proximal tubule and the fluid is isotonic with the surrounding cells. Glucose and amino acids have been removed from the filtrate. The filtrate then moves to the loop of Henle whose primary function is to remove water from the filtrate by osmosis.

15. Kidney action There is in increase in sodium concentration in the cells of the loop of Henle as we move from the area of the cortex to the inner pelvis of the kidney. This causes water to be drawn from the filtrate. These high levels of sodium are a result of active transport and results in increased concentration of filtrate (due to water loss).

16. Function of the Kidney The main function of the kidney is to filter blood in order to remove cellular waste products from the body. At any given time, 20 % of blood is in the kidneys. Humans can function with one kidney. If one ceases to work, the other increases in size to handle the workload.

17. The kidney has other functions but it is usually associated with the excretion of cellular waste such as : 1) urea (a nitrogenous waste produced in the liver from the breakdown of protein. It is the main component of urine) ; 2) uric acid (usually produced from breakdown of DNA or RNA) and 3) creatinine (waste product of muscle action).

18. All of these compounds have nitrogen as a major component. The kidneys are more than excretory organs. They are one of the major homeostatic organs of the body. They control water pH, secrete erythropoietin (a hormone that stimulates red blood cell production) and activate vitamin D production in the skin. That is why a doctor can tell so much from a urine sample.

19. Disorders of the Excretory System Our excretory system is very important in maintaining homeostasis. There are certain conditions which can affect the excretory system.Examples:

20. UTI (Urinary Tract Infection) Is a very common disorder. If the bladder has become infected, it is known as cystitis. If the urethra is infected., it is called urethritis. UTI is more common in women than men because of differences in anatomy. Symptoms include painful urination (burning sensation), frequent urination (even if no urine present) and bloody or brown urine. This can lead to chills, fever, nausea, vomiting and upper abdomen tenderness.

21. Kidney Infections Result when an infection reaches the kidneys and becomes known as pyelonephritis. Common causes can be infection from elsewhere in the body or obstruction of the prostate gland (usually in older men). For children, infection can be caused by the tube that drains urine from the kidneys and the bladder.

22. NOTE : If left untreated, all UTI’s can lead to permanent kidney damage and possible kidney failure. The general treatment is by antibiotics. A person needs to maintain good personal hygiene when eliminating wastes (liquid and solid forms) from the body. Also, a person should drink lots of water.

23. Kidney Stones Are also a common kidney disorder. They form when chemicals in the urine precipitate out and form crystals. The most common crystals are from calcium oxalate, while others could be from uric acid and cystine. Kidney stones are more common in men than women and can reoccur at any time. Factors such as recurrent urinary bladder infections, insufficient water intake and consumption, low levels of physical activity, and too much Vitamin C and D intake can lead to kidney stones. One of the best ways to decrease the occurrence of stones is to drink lots of water and to change your dietary habits.

28. At the end of the lesson, students will individually solve a puzzle to help them to retain and systematize the concepts learned and the correlation between kidney structure and its functions. This will be used as an evaluation method. 1 n 2 kidneys 3 pe hx rc 4 glomerulus nr e t i o n

29. 1.Nephron – structure in the kidney that acts as a microscopic filtration unit 2.Kidneys – the structure that regulates the amount of water, salts and other substances in the blood 3.Excretion – the removal of the toxic waste from the body 4.Glomerulus – the mass of very fine blood capillaries at the nephron that acts as a filter

30. This project has been funded with support from the European Commission. This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.