Hard Urine for a Surprise: The Urinary System Quiz / Test | Sci / Tech

Quiz Answer Key and Fun Facts

1. In the third step of embryogenesis, gastrulation, the primary germ layers become distinct and develop. Which of the primary germ layers does the kidney derive from?

Answer: Mesoderm

After the female's ovum has been fertilized by the male's sperm, the process of embryogenesis begins with cleavage. The second step, blastulation, is then followed by gastrulation. Gastrulation is the stage where the three primary germ layers become distinct and develop.

The kidney and the other urogenital organs develop in the mesoderm, as well as all the body's muscle, bone, and connective tissue. In addition, some mesoderm cells will also be determined as the dermis of the skin and the entire cardiovascular system.

The endoderm is responsible for the creation of all the epithelium that line the gastrointestinal tract, the respiratory system, and the urogenital system.

The ectoderm most notably becomes the nervous system, the pituitary gland, medulla, along with the cornea and lens of the eyes. In addition, it will also become the nasal, oral, and anal epithelium.

2. The urea that makes up a portion of the urine that leaves our body is made in the liver. What is the main purpose of urea?

Answer: To eliminate the excess nitrogen in the body

The liver creates urea in order to rid the body of excess nitrogen that comes with breaking down proteins in the liver. The structure of urea is a carbonyl with two amine groups attached to the carbonyl carbon. Once created by the liver, urea is released into the bloodstream and then ultimately excreted out within urine.

3. The kidney is an organ that purifies the blood, which means it must enter and exit the kidney somehow. Does the blood from the kidney enter through the renal artery and exit through the renal vein?

Answer: Yes

The kidney receives the unpurified blood through the renal artery. Then once it goes through all the filtration steps, it will return via the renal vein. The renal vein then leads into the inferior vena cava.

4. The blood begins the filtration process as it enters the glomerulus and into the efferent arteriole. The arteriole constricts and the fluid within the blood, including ions and other small, water-soluble compounds, moves into the glomerular basement through the glomerular capillaries. Once they reach the glomerular capillaries, what structure do they move into?

Answer: Bowman's Capsule

The blood flows into the glomerular basement and then into Bowman's capsule to be filtered further. The molecules that do not pass into the glomerular basement do not get excreted into urine and remain in the blood. Particulate that doesn't get filtered includes blood cells and plasma proteins.

5. The filtrate that initially passes through the glomerular basement will eventually reach the renal tube. The renal tube is surrounded by peritubular capillaries, whose function is to do which of these?

Answer: Reabsorb substances that should remain the bloodstream

The peritubular capillaries are all over the renal tube like vines. After the blood passes through the glomerular basement and through Bowman's capsule, it will be in the renal tube. Here the molecules that should still be in the blood, small, hydrophilic molecules, will be reabsorbed through active transport and taken to the renal vein.

6. The filtrate travels through a series of tubes that perform different functions. Two of these tubes are known as the proximal convoluted tube and the distal convoluted tube. How is the distal convoluted tube different from the proximal one?

Answer: The distal convoluted tube is - under normal conditions - not permeable to water

The proximal convoluted tube is where almost 70% of the filtrate is reabsorbed into the bloodstream. This is where most of the water is reabsorbed. Some solutes are taken with it as well, but the majority that is reabsorbed is water. The tube then flows down into the descending Loop of Henle where more water leaves and then up the ascending Loop of Henle where some ions are removed via active transport.

The filtrate then reaches the distal convoluted tube which is typically impermeable to water, unless the antidiuretic hormone (ADH) has been released.

The release of ADH allows water and urea to permeate the walls of the distal convoluted tube to be put back in the blood. This further makes the filtrate more concentrated. ADH is released when the body's blood is low in volume and there is high bloody osmolarity.

7. When the body's blood has low levels of blood volume, high blood pressure, and high osmolarity. The hormones aldosterone and antidiuretic hormone (ADH) will be released by a certain part of the brain. Which part of the brain releases aldosterone and ADH, respectively?

Answer: ADH: Posterior Pituitary; Aldosterone: Adrenal Cortex

The posterior pituitary releases ADH hormone into the bloodstream when there are low levels of blood volume and/or the blood has high osmolarity (high concentration of solute). In some cases, a drop in blood pressure can also cause ADH's release from the posterior pituitary. This causes the distal convoluted tube to be permeable to water and urea. The solvent leaves through the distal convoluted tube into the tissue of the kidney and gets picked up by the peritubular capillaries. The effects of its release are to increase the blood volume.

The adrenal cortex releases aldosterone into the bloodstream when there is high blood pressure. The aldosterone leads to the increased reabsorption of sodium ions by the distal nephron, specifically in the distal convoluted tube. This helps raise the blood pressure.

8. After the filtrate moves through the proximal convoluted tube it heads down through the descending and ascending Loops of Henle. The descending Loop of Henle is permeable to water and is made of squamous epithelial tissue. The ascending loop is not permeable to water and is made from what epithelial cells?

Answer: Cuboidal

The squamous tissues are so thin that the water can easily diffuse through the layers of the descending Loop of Henle, while the cuboidal epithelial tissue is so large and thick that water is not able to diffuse through. The ascending Loop of Henle thus performs active transport to remove ions.

9. Once the urine has made its way through all the filtration it will make its way through the ureter that leads into the urinary bladder. Here the urine remains until it gets the go ahead from the brain to the leave the body through the internal and external sphincter. What is unique about the external sphincter?

Answer: It's a voluntary muscle

The external sphincter is a voluntary, skeletal muscle that is controlled by ourselves when we want to go to the bathroom. It lets urine flow into the urethra and then out of our bodies.

10. Which of the following is a characteristic of the wastes that the kidneys are able to filter out?

Answer: Hydrophilic

The kidneys are able to remove hydrophilic, polar molecules and ions from the blood. This happens as the fluid of the blood, the plasma, moves into the glomerular basement and, shortly after, Bowman's Capsule. These hydrophilic wastes include the likes of urea, sodium, bicarbonate, and water.

Source: Author ThurstAsh

This quiz was reviewed by FunTrivia editor rossian before going online.
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Urine for a Surprise: The Urinary System Quiz

This is designed for the extremely biologically knowledgeable.

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