Glucose and Water Reabsorption in the Nephron

Glomerulus

Where glucose is first filtered in the nephron; glucose is freely filtered into the glomerular capsule.

Proximal Convoluted Tubule (PCT)

Where glucose is normally reabsorbed in the nephron via sodium-glucose cotransporters.

Distal Convoluted Tubule (DCT)

Indicates high blood glucose levels, such as in diabetes.

Water filtration in the glomerulus

Water is freely filtered along with small solutes.

Water reabsorption in the PCT

Passively, by osmosis as solutes like sodium are reabsorbed.

ADH (Antidiuretic Hormone)

Hormone that controls water reabsorption in the DCT.

Glomerular filtration driving force

Blood pressure (glomerular blood hydrostatic pressure).

Substances not filtered into glomerular capsule

Proteins (like albumin) and blood cells (RBCs, WBCs).

Peritubular capillaries

Aid in tubular reabsorption of water, glucose, sodium, and amino acids.

Effect of increased sodium reabsorption

Water reabsorption also increases, raising blood pressure and reducing urine.

Example of tubular secretion

Potassium (K+) secretion into the nephron tubules.

Fate of most glomerular filtrate

It is reabsorbed back into the blood; only a small portion becomes urine.

Sodium reabsorption and water movement

It creates an osmotic gradient that causes water to follow by osmosis.

ADH release trigger and function

Released during dehydration; increases water reabsorption in DCT & collecting ducts.

ACE inhibitors

They block the renin-angiotensin pathway, reducing sodium reabsorption, water retention, and blood pressure.

Aldosterone's role in the kidney

Increases sodium (and water) reabsorption in the DCT and collecting duct.

ANH and BNP hormones

Reduce sodium reabsorption, increase sodium excretion, and lower blood pressure.

Urine path from kidney to urethra

Kidney → Renal pelvis → Ureters → Bladder → Urethra.

Male and female urethra differences

Male: ~20 cm, passes through penis; Female: ~4 cm, opens above vagina.

Aquaporins

Water channels in cell membranes that help reabsorb water in the kidney.

Detection of drugs and hormones in urine

Because they are filtered and excreted by the kidneys.

Detrusor muscles

Smooth muscles in the bladder that contract during urination.

Retroperitoneal

Located behind the peritoneum; kidneys are retroperitoneal organs.

Urine path from collecting ducts to ureters

Collecting ducts → Renal pelvis → Ureters → Bladder.

Micturition reflex trigger

Bladder stretch; causes detrusor contraction and external sphincter relaxation.