Tubule narrows and forms U-shaped turn with simple squamous epithelium. Distal convoluted tubule has cuboidal cells with many mitochondria but no microvilli. Active in tubular secretion for moving molecules from blood into tubule. Glomerular Filtration a. Occurs when whole blood enters afferent arteriole and glomerulus. Glomerular filtrate dissolved molecules are about same concentration as plasma .
Efferent arteriole carries away remaining thicker blood.
Tubular Reabsorption is Both Passive and Active a. Molecules are reabsorbed from tubule into surrounding peritubular capillaries. Tubular Secretion Adds Substances a. Hydrogen and ammonium ions, creatinine, penicillin, etc., move from blood into distal convoluted tubules. Urine contains substances from glomerular filtration and tubular secretion. Reabsorbing Water a.