Urine Formation

Review of nephron structure

afferent arteriole

glomerulus

efferent arteriole

proximal convoluted tubule

distal convoluted tubule

Loop of Henle

blood

blood

The Nephron

- Most components of the nephron are within the cortex.

The Nephron

Review of Nephron Structure

Glomerulus Structure

Normal URINE

95% water Urea Uric acid Amino acids (trace) Electrolytes Urochrome =yellow pigment Kidney filter 180 L/Day Urine produced @1.8L/day

Abnormal URINE

RBCs WBCs Glucose Increased amt. of proteins Crystals/kidney stones Ketones Microbes drugs

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Steps to Urine Formation

1. Glomerular filtration- water and other dissolved substances are filtered out of blood and into glomerular capsuleFiltrate- liquid filtered out of capillaries and passes through nephron

Tubular reabsorption and

Tubular secretion

Steps to Urine Formation

2. Tubular Reabsorption- taking needed substances from the filtrate and transferring them back into the bloodOccurs in PCT, LOH, DCTPasses substances from tube to blood via osmosis and active transportReabsorbs water, glucose, amino acids, electrolytes, urea, uric acid, protein

Steps to Urine Formation

3. Tubular Secretion- substances move from blood into the nephron and enter filtrateOccurs in PCT, LOH, DCTWasteselectrolyteswaterdrugsH ions, penicillin, ammonia, KHappens faster than filtration

Tubular reabsorption and

Tubular secretion

Control of Urine Formation

At the same time as tubular absorption takes place in the PCT, tubular excretion is also occurring in the DCT.

Checkpoint

On your notes, write the pathway that urine takes from the blood and out of your body.

Path of Urine Glomerulus PCT Nephron loop (LOH) descending limb Nephron Loop (LOH) ascending limb DCT Collecting duct Papillary duct Renal Papilla Minor calyx Major calyx Renal pelvis Ureter Urinary bladder urethra

Factors that can affect the filtration rate

1. Diameter of the arterioles (both afferent and efferent)2. Permeability of the membrane of the glomerulus3. Obstruction of the flow of urine.