U8 Urinary System: Written questions:

Describe the primary functions of the urinary system

The urinary system removes wastes (like urea), regulates water and salt balance, maintains blood pH, controls blood volume and pressure, and helps maintain homeostasis

Describe the process of urine formation

• Blood enters the glomerulus and is filtered into Bowman's capsule.

• Filtrate moves through the proximal convoluted tubule where nutrients such as glucose are reabsorbed into the blood.

• In the loop of Henle, water leaves the filtrate by osmosis because of the high salt concentration in the medulla.

• In the distal convoluted tubule, blood pH is regulated and substances such as histamines and penicillin may be secreted into the urine.

• In the collecting duct, additional water is reabsorbed.

• The concentrated urine travels to the renal pelvis and then the ureter.

Describe the release and action of ADH.

• Produced by the hypothalamus.

• Released by the posterior pituitary gland.

• Released when blood volume decreases (dehydration).

• Increases the permeability of the collecting duct to water.

• More water is reabsorbed into the blood.

• Urine becomes more concentrated and lower in volume.

Describe the release and action of aldosterone.

• Produced by the adrenal cortex.

• Acts on the distal convoluted tubule.

• Increases sodium reabsorption and potassium secretion.

• Water follows sodium back into the blood.

• Urine becomes more concentrated and lower in volume.

How is the pH of blood regulated by the urinary system?

Blood pH is regulated primarily in the distal convoluted tubule by controlling the movement of hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻) between the blood and the forming urine.

• If blood pH is too low (acidic), more H⁺ is excreted into the urine.

• If blood pH is too high (basic), more HCO₃⁻ is reabsorbed into the blood and less H⁺ is excreted.

Normal blood pH is approximately 7.35.

What happens if the kidneys are damaged?

Waste builds up in the blood, and water, salts, and pH balance are disrupted.

How do kidneys regulate pH?

They remove H⁺ and keep bicarbonate to balance blood pH

What do ADH and aldosterone do?

ADH increases water reabsorption. Aldosterone increases salt reabsorption, which helps hold water.

Name the four main organs of the urinary system and state one function of each.

Kidneys: filter blood and make urine
Ureters: move urine to bladder
Bladder: stores urine
Urethra: releases urine outside body

Describe how the nephron produces urine in basic steps.

Filtration → reabsorption → secretion → urine formation.

What is glomerular filtration, and where does it occur?

when blood pressure pushes water and small molecules from blood into Bowman’s capsule in the kidney

• Define reabsorption and secretion in the nephron.

• Reabsorption is the movement of substances such as water, glucose, and ions from the nephron back into the blood capillaries.

• Secretion is the movement of wastes and excess substances (like hydrogen ions or drugs) from the blood into the nephron to be eliminated in urine

• Explain the role of ADH (antidiuretic hormone) in urine concentration.

ADH tells the kidneys to reabsorb more water, making less urine that is more concentrated.

What substances are normally found in urine?

Why is glucose normally absent in urine?

What does glucose in urine usually mean?

• Water, urea, salts, and creatinine

• Because the kidneys reabsorb all glucose back into the blood.

• It usually means diabetes or high blood sugar.

What happens to urine during dehydration?

Less urine is made, it becomes darker and more concentrated, and ADH increases.

A patient has glucose in their urine. Explain what might be happening in their body

This usually indicates diabetes or very high blood sugar.

The kidneys cannot reabsorb all the glucose, so some ends up in the urine.

A person has damage to their kidneys. Predict how this could affect homeostasis in the body.

Kidney damage causes waste buildup in the blood, water and salt imbalance, and poor control of blood pressure and pH. This disrupts homeostasis.

Explain why the kidneys are important for regulating blood pH.

The kidneys regulate blood pH by removing excess hydrogen ions (acid) into the urine and keeping bicarbonate in the blood, which helps neutralize acid and keep pH stable.

• Explain the process of urine formation from blood entering the kidney to urine leaving the body.

• Glomerulus: filters blood into nephron

• Proximal tubule: takes back most useful stuff (water, glucose, salts)

• Loop of Henle: takes back water + salt to concentrate urine

• Distal tubule: fine-tunes salts and wastes

• Collecting duct: adjusts final water amount → makes urine

• Ureter → bladder → urethra: urine leaves body

• Describe the structure of the nephron and explain how each part contributes to urine formation.

Glomerulus/Bowman’s capsule – filters blood.
Proximal tubule – reabsorbs nutrients, water, and ions.
Loop of Henle – reabsorbs water and salt to concentrate urine.
Distal tubule – adjusts ion balance and removes wastes.
Collecting duct – reabsorbs water (ADH) and forms final urine.

• Explain how the urinary system helps maintain homeostasis in the body. Include at least three different functions.

Regulates water levels in the body (hydration).
Controls electrolytes like sodium and potassium for nerve/muscle function.
Helps control blood pressure by adjusting blood volume.
Removes toxic waste like urea

• Describe how hormones regulate kidney function (include ADH and aldosterone).

by controlling water and salt balance.

ADH increases water reabsorption in the collecting ducts, reducing urine volume and conserving water. Aldosterone increases sodium reabsorption (and potassium excretion); water follows sodium, increasing blood volume and pressure.

Compare filtration, reabsorption, and secretion in detail, including where each occurs and why each is important.

Filtration: blood pressure forces water and small molecules into nephron at glomerulus.
Reabsorption: useful substances move from nephron back into blood (mostly in PCT).
Secretion: extra wastes and ions move from blood into nephron (mainly DCT).
Together they form urine and maintain body balance.