Urine Formation

Review of nephron structure

afferent arteriole glomerulus efferent arteriole proximal convoluted tubule distal convoluted tubule Loop of Henle 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

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 capsule Filtrate- 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 blood Occurs in PCT, LOH, DCT Passes substances from tube to blood via osmosis and active transport Reabsorbs 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 filtrate Occurs in PCT, LOH, DCT Wastes electrolytes water drugs H ions, penicillin, ammonia, K Happens 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 glomerulus 3. Obstruction of the flow of urine.