chapter 25

What are the primary functions of the urinary system?

Filter blood, remove wastes, produce urine, regulate water/electrolytes/pH.

What are secondary kidney functions?

BP regulation, osmolarity control, vitamin D activation, erythropoiesis.

What is the normal color of urine?

Pale yellow (urochrome).

Normal urine odor?

Slightly aromatic.

Normal urine pH?

4.5–8 (avg 6).

Normal urine volume per day?

1-2 Liters

Normal specific gravity?

1.001–1.035.

Function of the urethra?

Carries urine out of the body.

What controls urination?

Internal (involuntary) and external (voluntary) sphincters.

Length of male urethra?

20cm

Function of male urethra

Carries urine and semen

Length of female urethra?

3-4cm

Function of female urethra

carries urine only

Bladder mucosa type?

Transitional epithelium.

Bladder muscle name?

Detrusor muscle.

Main bladder function?

Stores and expels urine.

What moves urine through ureters?

Peristalsis + gravity.

Ureter mucosa?

Transitional epithelium.

Kidney size?

Fist-sized (~4–5 inches).

Kidney location?

Retroperitoneal; right lower.

Outer region of kidney?

Cortex

Inner region of kidney?

Medulla

What are renal pyramids?

Cone-shaped structures in medulla

what is the hilum?

Entry/exit for ureter, vessels, nerves

What is a nephron?

Functional unit of the kidney that forms urine.

How many nephrons per kidney?

About 1 million.

What vessel brings blood to the glomerulus?

Afferent arteriole.

What vessel leaves the glomerulus?

Efferent arteriole.

What does Bowman’s capsule do?

Collects filtrate.

What is the glomerulus?

Capillary bed where filtration occurs.

Function of PCT?

Main site of reabsorption.

Descending loop permeability?

Water only.

Ascending loop permeability?

Na⁺ and Cl⁻ only.

Function of DCT?

Regulated reabsorption/secretion.

Collecting duct regulated by?

ADH (water reabsorption).

What do JG cells release?

Renin.

What does the macula densa sense?

NaCl levels in filtrate.

Where does filtration occur?

Glomerulus

How much filtrate is made daily?

180 Liters

What is filtered from urine?

Water, ions, glucose, AAs, urea.

What is NOT filtered from urine?

Proteins, cells.

What is reabsorption?

Returning substances from filtrate to blood.

Major site of reabsorption?

PCT.

Loop of Henle function?

Concentrates filtrate through countercurrent mechanism.

What regulates DCT/CD reabsorption?

Hormones (ADH, aldosterone).

What mechanism concentrates urine?

Countercurrent multiplier.

Where does concentration mainly occur?

Loop of henle and collecting duct.

What is secretion?

Moving substances from blood → filtrate.

What gets secreted?

H⁺, K⁺, drugs, creatinine, urea.

What triggers renin release?

Low BP/low blood volume.

What does Angiotensin II do?

Vasoconstriction + aldosterone release → Higher BP.

What does ADH do?

Increases water reabsorption.

What does ANP do?

Causes sodium and water loss → lowers BP.

What does PTH do in the kidneys?

Higher calcium reabsorption, Lower phosphate.

What does the kidney do to Vitamin D?

Activates it

What hormone increases RBC production?

Erythropoietin (EPO).

How does the kidney regulate BP?

RAAS + volume control.

How does the kidney regulate osmolarity & pH?

Adjusts Na⁺, K⁺, H⁺, and bicarbonate.