8.5.1 c Kidney Worksheet PDF

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Module 8: Non-infectious diseases and disorders IQ 5 – How can technologies be used to assist people who experience disorders?

Holiday work booklet #3 – The Kidney The anatomy and functioning of the kidney The kidneys are organs that form part of the excretory system. They have 2 primary functions within the human body – waste removal (excretory), and the regulation of water and electrolytes within the body (osmoregulation).

a) shows the location of the L and R kidney within the human body. They are located towards the back of the body (posterior) at around the level of the elbow. They are approximately the size of a small apple.

Each kidney has an artery to carry fresh oxygenated, blood with waste in it to the kidney from the heart, and a vein to carry de-oxygenated blood back towards the heart once it has been cleared of waste. b) shows the internal macroscopic structure of the kidney. The kidney is made up of 3 layers – the cortex (outer layer, dark in colour), the medulla (middle layer, lighter in colour and make up of pyramids) and the pelvis (innermost layer) c) shows the macroscopic structure/location of the nephron– the smallest functional unit of the kidney. The nephron begins with the Bowman’s capsule which encircles the glomerulus and collects fluid from the blood through filtration and selectively secretes or absorbs various substances along its length. There are approximately 500000 nephrons in each kidney. d) shows a detailed image of the nephron, glomerulus and associated blood vessels. The nephron ends in the collecting duct which carries nearly fully concentrated urine to the bladder.

The kidney, and more specifically the nephron, works in 3 ways. Use the table below to describe and explain the way that the kidney filters the blood and clears it of toxins and allows it to osmoregulate. Process

Filtration

Substances

Direction of movement of materials

Everything in the blood that is smaller than a red blood cell

Blood --> Nephron

Reabsorption

Nephron --> Blood

Secretion

Blood --> Nephron

Passive or active?

Description of process

Using your understanding of the kidney and the nephron, explain what happens to the following substances from when they enter the kidney: Urea (waste product from the breakdown of protein):

Water:

Salt (Na+ and Cl-):

Amino acids:

Glucose:

Large proteins, red blood cells, white blood cells:

Drugs/toxins:

Label the parts of the nephron, and for each part, give a description of what happens in this location.

Letter

Name

Description

A

B

C

D

E

F

G

The substance which leaves the kidney through the collecting ducts is fully formed urine. The urine travels down the ureter, and the urine is then stored in the bladder. The bladder contains stretch receptors which send messages to the brain to evacuate. The urine flows from the bladder through the urethra.

The waste removal function of the kidney happens continuously – as the body produces urea through the digestion of protein, it is transported to the blood and cleared by the kidneys. The osmoregulation function of the kidney happens as needed. The hypothalamus in the brain is constantly monitoring the composition of the blood – primarily the concentration. If the blood is too concentrated, the hypothalamus stimulates the kidney to retain more water so that the blood dilutes. If the blood is too dilute, the hypothalamus stimulates the kidney to excrete more water so that the blood concentrates. Blood that is overly concentrated causes the release of anti-diuretic hormone (also known as ADH and vasopressin) from the pituitary gland. This causes more water to be retained by the kidney. Blood that is overly dilute causes the release of aldosterone from the adrenal glands, which increases the reabsorption of sodium ions into the blood, making it more concentrated. Complete the table below to summarise the action of hormones on osmoregulation Hormone

ADH

Aldosterone

Released by

Action on nephron

Effect on blood

Effect on urine

When the kidney is not functioning properly Several conditions can lead to kidney functioning at suboptimal level: 

   

Type 1 and Type 2 diabetes: increased blood glucose put strain on the nephrons because they are forced to filter more from the blood. Eventually the glomeruli and Bowman’s capsules become damaged and are not able to filter the blood properly, letting protein and other large molecules into the nephron. Persistent high blood pressure: puts strain on the nephrons and causes them to come damaged and allow inappropriate materials to leak into the nephron. Recurrent kidney infections Kidney stones Tumors in the kidney

When kidney function decreases, there is a spectrum of symptoms for the sufferer. Two kidneys offer a redundant amount of function, so individuals can lose up to 50% of function (either 50% of each kidney or the loss of one entire kidney) without suffering serious, life-altering effects. Symptoms of loss of kidney function can include:      

Digestive: nausea, vomiting, loss of appetite Fluid buildup: swelling, oedema, chest pain from fluid buildup around the heart, shortness of breath from fluid on the lungs, high blood pressure Fatigue and sleeplessness Confusion Muscle twitches and cramps Itching

The primary cure for loss of kidney function is a kidney transplant. However, like most transplant cases, there are far more people in need of donations than there are donors. Kidneys can be donated from healthy individuals on a voluntary basis (usually among family members) but this puts pressure on the one remaining kidney of the healthy donor. While a person suffering loss of kidney function waits for a kidney donation or for treatment of the root cause of the loss, the wastes that the kidney normally filters will build up in the body and have a toxic effect. The blood must be cleared of waste by technology – kidney dialysis. Dialysis allows urea to be drawn out of the blood through filtration. It is effective at keeping levels of toxic urea low enough to keep a person alive, but it is not comparable to the action of a live and functional kidney. Some descriptions of the process of dialysis can be found here and here.

Examination style questions Question 1. Renal dialysis and kidney transplants are very different treatments for the same medical condition. Each treatment was developed from a new application of biological knowledge.’ Justify these statements. (8) Question 2. (a) What chemicals are filtered out of the blood by the kidney? (2) (b) What chemicals are reabsorbed into the blood by the kidney? (2) (c) Explain the steps involved in the formation of urine. (4) Question 3. A diagram of a nephron is shown.

(a) Label each of the two boxes on the diagram using A, B, C or D to identify the processes that take place at this location (2) (b) Which one of the above processes (A, B, C or D) occurs due to active transport? (2) (c) Outline the effect of aldosterone on the control of body fluids. (4) Question 4. (a) Explain ONE reason why the concentration of water in cells should be maintained within a narrow range for optimal cell function. (2) (b) A person has consumed large amounts of water. Complete the table to show the effect on each of the variables listed. (3)

Question 5. Draw a diagram of a mammalian kidney. On your drawing, label THREE regions involved in the excretion of waste products AND indicate the main process that occurs in each of the three regions. (6)...