Urinary System – Anatomy & Physiology II (SCIE158)

Question-and-answer flashcards covering anatomy, physiology, and regulation of the urinary system, suitable for exam review.

What organs comprise the urinary system?

Kidneys, ureters, urinary bladder, and urethra.

What is the primary homeostatic role of the urinary system?

Managing the volume and composition of the body’s fluid reservoirs, primarily blood.

Name five ions whose blood concentration is regulated by the kidneys.

Na+, K+, Ca2+, Cl−, and phosphate ions (HPO4 2−).

Which two hormones are produced by the kidneys?

Erythropoietin and calcitriol.

How do the kidneys help regulate blood pH?

By excreting H+ and reabsorbing bicarbonate (HCO3−).

Where are the kidneys located?

Retroperitoneally between T12 and L3, with the right kidney slightly lower.

What protects the kidneys externally?

Renal capsule, adipose capsule, renal fascia, and the 11th & 12th ribs.

What structures enter/exit the kidney at the hilum?

Renal artery, renal vein, ureter, nerves, and lymphatics.

What are the two major regions of the kidney parenchyma?

Renal cortex and renal medulla.

What structures make up a renal lobe?

A renal pyramid, overlying cortex, and adjacent renal columns.

Into what do papillary ducts drain urine?

Minor calyces.

What percentage of resting cardiac output goes to the kidneys?

20–25% (about 1.2 L/min).

Name the three capillary networks associated with nephrons.

Glomerular capillaries, peritubular capillaries, and vasa recta.

What is the functional unit of the kidney?

The nephron.

Approximately how many nephrons are in each kidney?

About 1.2 million.

Which part of the nephron is responsible for blood filtration?

The renal corpuscle (glomerulus + Bowman’s capsule).

List the three segments of the renal tubule in order.

Proximal convoluted tubule (PCT), nephron loop (loop of Henle), distal convoluted tubule (DCT).

What cells form the visceral layer of Bowman’s capsule?

Podocytes.

What are the three layers of the filtration membrane?

Fenestrated endothelium, basement membrane, and slit membrane between pedicels.

What is the role of the juxtaglomerular apparatus (JGA)?

Regulates blood pressure and GFR via macula densa and juxtaglomerular cells.

Which type of nephron has short loops and is most numerous?

Cortical nephrons (80–85%).

Which nephrons are responsible for producing concentrated urine?

Juxtamedullary nephrons with long loops of Henle.

List the three stages of urine formation.

Glomerular filtration, tubular reabsorption, and tubular secretion.

Define glomerular filtration rate (GFR).

The amount of filtrate formed by both kidneys each minute (≈125 mL/min in males, 105 mL/min in females).

What is the net filtration pressure (NFP) in the glomerulus?

About 10 mmHg (GBHP 55 – CHP 15 – BCOP 30).

Name the three intrinsic/extrinsic mechanisms regulating GFR.

Renal autoregulation, neural regulation, and hormonal regulation.

Describe the myogenic mechanism of autoregulation.

Afferent arteriole smooth muscle constricts when stretched, reducing GFR.

How does tubuloglomerular feedback reduce GFR?

Macula densa detects high NaCl, inhibits nitric oxide, causing afferent arteriole constriction.

Which nervous system predominates in neural regulation of GFR?

Sympathetic nervous system (causes vasoconstriction of afferent arterioles).

What enzyme do kidneys release when blood pressure drops?

Renin.

What are the two main hormones affecting GFR hormonally?

Angiotensin II (decreases GFR) and Atrial Natriuretic Peptide (ANP) (increases GFR).

Where does obligatory water reabsorption occur?

PCT and descending limb of the nephron loop.

What percentage of water reabsorption is facultative and hormone-dependent?

About 10%, regulated by antidiuretic hormone (ADH) in the collecting ducts.

Which tubule segment reabsorbs all glucose and amino acids?

Proximal convoluted tubule (PCT).

Which hormone stimulates Na+ and water reabsorption in the DCT?

Aldosterone.

What hormone increases Ca2+ reabsorption in the DCT?

Parathyroid hormone (PTH).

Explain tubular secretion’s two primary purposes.

Regulating blood pH (via H+ secretion) and eliminating wastes/drugs from blood to urine.

Why must some drugs be taken multiple times per day in relation to kidney function?

Because the kidneys clear them rapidly through tubular secretion, lowering blood levels.

How does ADH concentration affect urine osmolarity?

Low ADH produces dilute urine; high ADH produces concentrated urine.

Give two common diuretics and their mechanisms.

Caffeine (inhibits Na+ reabsorption) and alcohol (inhibits ADH secretion).

What is the typical daily urine volume?

1–2 liters per 24 hours.

What is normal urine pH range?

4.6 to 8.0 (average 6.0).

Which plasma component should not normally appear in urine and indicates proteinuria?

Albumin.

Name three waste products normally excreted in urine.

Urea, creatinine, and uric acid.

What is dialysis and what kidney functions can it not replace?

Artificial blood cleansing via diffusion; cannot replace hormone production (erythropoietin, renin, calcitriol).

What transport mechanisms move urine down the ureters?

Peristaltic waves, hydrostatic pressure, and gravity.

How is backflow from bladder to ureter prevented?

Physiological valve created by bladder wall compression over ureteral openings.

What is the average bladder capacity?

700–800 mL.

Name the three layers of the ureter/bladder wall.

Mucosa (transitional epithelium), muscularis (smooth muscle), and adventitia (CT).

Which muscle forms the bladder’s muscularis?

The detrusor muscle.

Differentiate internal and external urethral sphincters.

Internal: involuntary smooth muscle; External: voluntary skeletal muscle.

How long is the female urethra versus the male urethra?

Female: 3–4 cm; Male: ~18 cm.

What spinal levels mediate the micturition reflex?

S2–S3 parasympathetic segments.

Define urinary incontinence.

Lack of voluntary control over micturition.

What type of incontinence is triggered by coughing, sneezing, or laughing?

Stress incontinence.

List two age-related anatomical changes in kidneys.

Kidney size shrinks by about one-third and renal blood flow/filtration drops by ~50%.

Why might drug dosages need adjustment in the elderly?

Reduced renal clearance due to decreased GFR and nephron number.

What common prostate change affects urinary function in older men?

Benign prostatic enlargement leading to urinary retention or frequency.