Chapter 12 - Excretory System

Question 1

What are the kidneys and their functions?

Answer 1

Bean-shaped organs that extract waste from blood, balance body fluids, forms urine, balances salts/electrolytes and acts as a blood reservoir, holding 25% of the body’s blood.

Question 2

What is the ureter and what does it do?

Answer 2

The tube that conducts urine from the kidney to the bladder.

Question 3

What is the urinary bladder and what does it do?

Answer 3

Bladder stores urine. When stretched, receptors send signals to the brain. A urinary sphincter muscle at the base of the bladder acts as a valve, permitting the storage of urine.

Question 4

What is the urethra?

Answer 4

The tube that carries urine from the bladder to the exterior of the body.

Question 5

What is a nephron and what does it consist of?

Answer 5

A functional unit of the kidney consisted of one million slender tubules.

Question 6

What is the afferent arteriole and what is its function?

Answer 6

A small branch of the renal artery that carries blood to the glomerulus and supplies the nephrons with blood.

Question 7

What is the glomerulus?

Answer 7

The high-pressure capillary bed that is the site of filtration. The glomerulus does not transfer blood into a venule. Blood leaves the glomerulus by efferent arterioles.

Question 8

What is the efferent arteriole and its function?

Answer 8

A small branch of the renal artery that carries blood away from the glomerulus to the peritubular capillaries.

Question 9

What is the peritubular capillary?

Answer 9

A member of the network of small blood vessels that surround the tubule of the nephron. Blood leaves the nephron via a venule that joins the renal vein.

Question 10

What is the Bowman’s capsule and its function?

Answer 10

The cuplike structure that surrounds the glomerulus. It is the funnel-like part of the nephron. Fluid to be processed into urine enters the Bowman’s capsule through blood.

Question 11

What does the cortex of the kidney house?

Answer 11

The Bowman’s capsule, afferent arterioles, and efferent arterioles.

Question 12

What is the proximal tubule and its function?

Answer 12

The section of the nephron joining the Bowman’s capsule with the loop of Henle. Urine is carried through it.

Question 13

What is the loop of Henle?

Answer 13

The section of the tubule that carries the filtrate from the proximal tubule to the distal tubule. The loop of Henle descends into the medulla of the kidney.

Question 14

What is the distal tubule?

Answer 14

Tubule that conducts urine from the loop of Henle to the collection duct.

Question 15

What is the collecting duct?

Answer 15

A tube that carries urine from nephrons to the renal pelvis. Also the last segment of the nephron.

Question 16

What is the liver and its functions?

Answer 16

Transforms ingested toxins, such as alcohol and heavy metals, into soluble compounds that can be eliminated by the kidneys. Also transforms the hazardous products of protein metabolism into metabolites which are then eliminated by the kidneys.

Question 17

What is deamination and where does it occur?

Answer 17

Removal of an amino group from an organic compound. Occurs in the liver. Ex. Proteins contain the amino group NH2 which is a part of the amino acids that should be discarded.

Question 18

What is ammonia? What can it form and where?

Answer 18

A toxic water-soluble gas. Marine species can release ammonia through the day but land animals cannot so it must be stored. It is stored in the liver where two molecules of ammonia combine with CO2 to form urea, another waste product.

Question 19

What is urea?

Answer 19

The nitrogen waste formed from two molecules of ammonia and one molecule of CO2. Urea is 100,000 times less toxic than ammonia. Blood can dissolve 33mg of urea per 100mL of blood.

Question 20

What is uric acid?

Answer 20

A waste product formed from the breakdown of nucleic acids.

Question 21

What does each nephron of the kidney have?

Answer 21

An independent blood supply.

Question 22

What is the capillary bed pressure?

Answer 22

About 25mmHg.

Question 23

What is the glomerulus pressure?

Answer 23

About 65mmHg.

Question 24

How does filtration work in the kidney?

Answer 24

Blood moves through the afferent arteriole into the glomerulus, a high-pressure filter. Dissolved solutes pass through the walls of the glomerulus into the Bowman’s capsule through diffusion. (Some large particles such as plasma proteins, erythrocytes, and platelets don’t pass because they’re too big.)

Question 25

What is filtered through the glomerulus and into the Bowman’s capsule? What isn’t filtered?

Answer 25

Water, sodium chloride, glucose, amino acids, hydrogen ions, and urea are filtered.
Plasma proteins, erythrocytes, and platelets are not filtered.

Question 26

How can selective reabsorption occur?

Answer 26

By both active and passive transport.

Question 27

How is ammonia originated and where is it secreted?

Answer 27

Originated by the deamination of amino acids by the liver and it is excreted in the kidneys.

Question 28

How is urea originated and where is it secreted?

Answer 28

Originated by the deamination of amino acids by the liver and combining with CO2 and it is secreted in the kidneys and skin (in small amounts).

Question 29

What is the basic purpose of the excretory system?

Answer 29

To regulate the composition and volume of body fluids by removing wastes and returning needed substances to the body for reuse.

Question 30

What is secretion? What is needed for secretion?

Answer 30

The movement of wastes from the blood into the nephron to be excreted in the urine. Occurs by active transport so ATP is required.

Question 31

Where does secretion occur?

Answer 31

In the proximal tubule and the distal tubules.

Question 32

How does the glomerulus form urine?

Answer 32

Glomerular blood pressure forces some water and dissolved substances from the blood through the pores in the glomerulus.

Question 33

How does the Bowman’s capsule form urine?

Answer 33

Receives filtrate from the glomerulus.

Question 34

What is ADH and what does it do?

Answer 34

Antidiuretic hormone regulates water reabsorption in the nephron and it is made in the hypothalamus. It is released in response to a decrease in blood volume, or increased concentration of sodium or other substances.

Question 35

What is aldosterone and what does it do?

Answer 35

A hormone produced in the adrenal gland and acts mainly in the functional unit of the kidneys to increase the reabsorption of Na+ ions and water by the kidneys. It works when decreased blood pressure is detected and increases osmolarity in the extracellular fluid which will eventually return blood pressure to normal.

Question 36

What is diabetes mellitus caused by and what are its effects?

Answer 36

Diabetes mellitus is caused by inadequate secretion of insulin from islet cells in the pancreas. Without insulin, blood glucose levels rise and remains in the nephron and is excreted in urine. It also provides osmotic pressure that opposes the osmotic pressure created by other solutes that have been actively transported out of the nephron. Those with diabetes mellitus urinate more and lose more water.

Question 37

What is diabetes nephritis caused by and what are its effects? Give an example of the disease.

Answer 37

Diabetes nephritis is not a single disease but a broad description of many diseases characterized by inflammation of the nephrons. One type of nephritis affects the tiny blood vessels of the glomerulus. It is believed that toxins produced by invading microbes destroy the blood vessels. altering the permeability of the nephron. This allows the large proteins to pass into the nephron and alters osmotic pressure which increases urine output. Nephritis can lead to irreversible kidney damage and failure.

Question 38

What is diabetes insipidus caused by and what are its effects?

Answer 38

Results from a defect in the ADH (antidiuretic hormone) which regulates the water absorption in the nephron. A person with insipidus diabetes produces large amounts of urine.

Question 39

What causes kidney stones and what are its effects?

Answer 39

Kidney stones are caused by the precipitation of mineral solutes from the blood. The sharp sided stones can lodge in the renal pelvis, or they may move down the ureter into the bladder and be passed out of the body with urine. Delicate tissues can be torn, causing pain. Larger stones can be lodged in the ureter which requires medical attention.