Urinary System and Fluid-Electrolyte Balance: Anatomy, Physiology, and pH

Where are the kidneys located?

Under back muscles, behind the parietal peritoneum, above the waistline, with the right kidney slightly lower than the left.

What are the two main internal structures of the kidney?

Renal cortex (outer layer) and renal medulla (inner portion).

What are renal pyramids?

Triangular divisions of the renal medulla.

What is the renal pelvis?

An expansion of the upper end of the ureter that lies inside the kidney.

What are nephrons?

Microscopic units of the kidneys responsible for filtering blood and forming urine.

What is the renal corpuscle composed of?

Bowman's capsule and its glomerulus.

What is Bowman's capsule?

A cup-shaped structure that encases the glomerulus.

What is the function of the glomerulus?

A network of blood capillaries surrounded by Bowman's capsule that filters blood.

What percentage of nephrons are cortical nephrons?

85% of total nephrons.

What is the specialized role of juxtamedullary nephrons?

They play a specialized role in concentrating urine.

What are the components of the renal tubule?

Proximal convoluted tubule, loop of Henle (descending and ascending loops).

What is the first segment of the renal tubule?

Proximal convoluted tubule.

What is the function of the distal convoluted tubule?

Excrete toxins and nitrogenous wastes, regulate chemical levels in blood, maintain water balance, and help regulate blood pressure.

What are the three processes involved in urine formation?

Filtration, reabsorption, and secretion.

What occurs during the filtration process in the kidneys?

Glomerular blood pressure causes water and dissolved substances to filter from the glomerulus into Bowman's capsule.

What is the normal glomerular filtration rate?

125 ml per minute.

What happens during the reabsorption process in the kidneys?

Substances move from renal tubules into blood in peritubular capillaries; water, nutrients, and ions are reabsorbed.

How is water reabsorbed in the kidneys?

By osmosis from the proximal tubules.

What occurs during the secretion process in the kidneys?

Substances move from blood in peritubular capillaries into urine in the distal and collecting tubules.

What substances are commonly secreted during kidney secretion?

Hydrogen ions, potassium ions, certain drugs, and ammonia.

What hormone primarily controls urine volume?

Antidiuretic hormone (ADH).

What is the structure of ureters?

Narrow long tubes with expanded upper ends (renal pelvis) lined with mucous membrane and muscular layer.

What is the function of the urinary bladder?

Storage of urine before voiding.

What is the structure of the urethra?

A narrow tube from the urinary bladder to the exterior, lined with mucous membrane.

What is the function of the urethra?

Passage of urine from the bladder to the exterior of the body and passage of male reproductive fluid (semen).

What is micturition?

The process of urination or voiding.

What initiates the emptying reflex in the bladder?

A stretch reflex in the bladder wall.

What is enuresis?

Involuntary urination in young children.

What is nocturnal enuresis?

Nighttime bed-wetting.

What is urinary retention?

Urine is produced but not voided.

What is urinary suppression?

No urine is produced, but the bladder is normal.

What is incontinence?

Urine is voided involuntarily.

What are the main sources of body fluid intake?

Liquids we drink and food we eat, including catabolism.

What organs are primarily responsible for fluid output?

Lungs, kidneys, skin, and large intestine.

What is the difference between electrolytes and nonelectrolytes?

Electrolytes dissociate into ions in water, while nonelectrolytes do not.

What is dehydration?

Total volume of body fluids is smaller than normal, with fluid output exceeding fluid input.

What is overhydration?

Total volume of body fluids is larger than normal, with fluid input exceeding output.

What is hyperkalemia?

Blood potassium levels are too high.

What is hypernatremia?

Blood sodium levels are too high.

What is hypokalemia?

Blood potassium levels are too low.

What is hypocalcemia?

Blood calcium levels are too low.

What does pH indicate?

The hydrogen ion (H+) concentration of a fluid, with pH 7.0 being neutral.

What are buffers in blood?

Chemical substances that prevent sharp changes in pH when acids or bases are added.

What is the normal ratio of sodium bicarbonate to carbonic acid in blood?

20:1

What physiological mechanisms regulate changes in blood pH?

Respiratory rate changes, renal activity, and buffering by chemical substances.

How quickly do respiratory mechanisms act to regulate pH?

Within minutes.

How do kidneys regulate blood pH?

By secreting hydrogen ions and ammonia into urine and reabsorbing sodium bicarbonate.

What is acidosis?

A condition characterized by an excess of carbonic acid in the blood.

What is alkalosis?

A condition characterized by a deficit of carbonic acid in the blood.

What happens to blood pH when the amount of carbonic acid increases?

Blood pH decreases.

What happens to blood pH when the amount of sodium bicarbonate decreases?

Blood pH decreases.

What are the two kinds of pH imbalance?

Acidosis and alkalosis.

What regulates blood levels of sodium bicarbonate?

The kidneys.

What regulates carbonic acid levels in blood?

The lungs.

What is respiratory acidosis?

A condition caused by carbonic acid excess due to respiratory disturbances.

What is respiratory alkalosis?

A condition caused by carbonic acid deficit due to respiratory disturbances.

What is metabolic acidosis?

A condition characterized by a bicarbonate deficit.

What is metabolic alkalosis?

A condition characterized by a bicarbonate excess.

How does respiration affect blood pH?

Respiration removes CO2, decreasing carbonic acid levels and increasing blood pH.

What is the effect of buffering on fixed acids in tissue capillaries?

It prevents sharp changes in pH.

What physiological change occurs when blood pH decreases slightly?

H+ concentration in blood increases slightly.

What role do the distal tubules play in pH regulation?

They secrete hydrogen ions and ammonia into urine in exchange for sodium bicarbonate.

What can cause disturbances in pH balance?

Relative quantities of sodium bicarbonate and carbonic acid in the blood.