HBS: Unit 4 Study Guide (ADVANCED)

Explain the exact urine flow sequence from nephron to outside the body.

Nephron → collecting duct → renal papilla → minor calyx → major calyx → renal pelvis → ureter → bladder → urethra → outside body.

Explain the exact blood flow sequence through the kidney.

Descending aorta → renal artery → smaller arteries → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries/vasa recta → renal vein → inferior vena cava.

Why does filtrate not become 172.8 L of urine per day?

The kidneys filter about 172.8 L/day, but most water and useful solutes are reabsorbed from the nephron back into the blood, so only a small amount becomes urine.

Compare filtration, reabsorption, and secretion.

Filtration moves small substances from blood into the nephron; reabsorption moves useful substances from nephron back into blood; secretion moves wastes, drugs, hydrogen ions, and excess ions from blood into nephron.

What should be found in healthy urine, and what should not be found?

Healthy urine should contain urea, excess water, excess salts, and metabolic wastes. It should not contain glucose, blood cells, large proteins, bacteria, or large numbers of white blood cells.

How does the circulatory system interact with the kidneys to create urine?

Blood enters the kidney through renal arteries and reaches the glomerulus. Waste and small molecules are filtered into Bowman’s capsule, while cleaned blood leaves through capillaries and renal veins.

Why would narrowed renal arteries affect kidney function and blood pressure?

Narrowed renal arteries reduce blood flow to kidneys, lowering filtration and waste removal. The kidneys may activate RAAS, causing fluid retention and increased blood pressure.

How do the kidneys help maintain homeostasis?

Kidneys remove wastes, regulate water and electrolyte balance, maintain blood pH, regulate blood volume, and help control blood pressure.

Why does the bladder have transitional epithelium?

Transitional epithelium stretches as the bladder fills. Empty bladder cells are stacked and cube-shaped; full bladder cells flatten to allow expansion.

How are male and female urinary systems different?

Males have a longer urethra that carries urine and semen; females have a shorter urethra that carries urine only.

How can a urinalysis show kidney damage?

Protein or albumin in urine may show glomerular damage because large proteins should normally stay in the blood.

How can a urinalysis suggest diabetes mellitus?

Glucose in urine suggests diabetes because healthy urine normally does not contain glucose.

How can a urinalysis suggest a urinary tract infection?

White blood cells and bacteria in urine suggest infection because they are not normally found in healthy urine.

How can a urinalysis suggest kidney stones?

Red blood cells and crystals in urine may suggest kidney stones, especially if there is pain or abnormal urine appearance.

What does high specific gravity suggest?

High specific gravity means concentrated urine and often suggests dehydration.

What does low specific gravity suggest?

Low specific gravity may suggest overhydration or a kidney concentrating problem.

Why are ketones abnormal in urine?

Ketones suggest rapid fat breakdown, starvation, or uncontrolled diabetes because normal urine should not contain ketones.

Why can kidney stones form?

Kidney stones form when urine has too many crystal-forming substances like calcium, oxalate, or uric acid, or when urine lacks substances that prevent crystals from sticking.

Compare calcium stones and uric acid stones.

Calcium stones are the most common and often contain calcium oxalate. Uric acid stones are linked to dehydration, high-protein diets, fluid loss, and gout.

Compare a healthy kidney and a PKD kidney.

A healthy kidney is smooth, normal-sized, has regular tubules and many blood vessels. A PKD kidney is enlarged, bumpy, has fluid-filled cysts, enlarged tubules, fewer blood vessels, and reduced function.

Why does PKD reduce kidney function?

Fluid-filled cysts enlarge and damage kidney tissue, reducing normal filtering structures and interfering with nephron function.

What symptoms could suggest PKD?

High blood pressure, frequent kidney stones, blood in urine, excessive urination, and back or abdominal pain.

How is PKD inherited or caused?

PKD can be inherited through a mutated PKD gene or caused by a spontaneous mutation.

Why might a PKD patient need dialysis or transplant?

If cyst damage causes kidney failure, dialysis may filter the blood artificially, or a transplant may replace kidney function.

What does eGFR tell doctors?

eGFR estimates how well kidneys filter blood and helps stage chronic kidney disease.

What does uACR tell doctors?

uACR measures albumin in urine; albumin suggests kidney damage and higher CKD progression risk.

Why is albumin in urine concerning?

Albumin is a protein that should mostly stay in blood. If it appears in urine, the kidney filter may be damaged.

What eGFR values are important for dialysis and transplant evaluation?

Dialysis may begin when eGFR is less than 20. Transplant evaluation may begin when eGFR is less than 15.

Why does DNA move toward the positive electrode in gel electrophoresis?

DNA has a negatively charged phosphate backbone, so it is attracted to the positive electrode.

Why do smaller DNA fragments move farther in gel electrophoresis?

Smaller fragments can move through the gel pores more easily, so they travel faster and farther than larger fragments.

Why use more than one restriction enzyme in DNA diagnosis?

Using more than one enzyme creates more fragment patterns, making it easier to detect differences between normal and mutated DNA.

What is the purpose of a DNA ladder?

A DNA ladder provides known fragment sizes so unknown DNA fragments can be compared and estimated.

How could gel electrophoresis help diagnose PKD?

If a person’s DNA fragments match the mutation pattern after restriction enzyme digestion, they may be PKD positive.

What does HLA matching mean in transplant compatibility?

HLA matching compares cell-surface antigens. A better HLA match lowers rejection risk because the immune system is less likely to attack the kidney.

Why does blood type matter in kidney transplant?

Incompatible blood types can trigger immune attack and rejection, so donor and recipient blood types must be compatible.

Why is crossmatch testing important before transplant?

Crossmatch testing checks if the recipient has antibodies against the donor, which could cause rejection.

Why is type O considered the universal blood donor?

Type O can donate to A, B, AB, and O because it lacks A and B antigens.

Why is type AB considered the universal blood recipient?

Type AB can receive A, B, AB, or O because it has both A and B antigens and does not make anti-A or anti-B antibodies.