Essentials of Anatomy and Physiology

426 The Urinary System

Proximal convoluted tubule

H 2 O

Glucose

Amino acids

Small proteins

Minerals

Wastes

Bowman's capsule

Glomerulus

Efferent arteriole

Afferent arteriole

Distal

convoluted

tubule

Collecting

tubule

H 2 O

H+

Ammonia

H 2 O

Glucose

Amino acids

Small proteins

Minerals

H 2 O

H 2 O

Wastes

H+

Na+

K+

Urine

Artery

Vein

Creatinine

Medications

Peritubular

capillaries

Loop of Henle

Glomerular

filtration

Tubular

reabsorption

Tubular secretion

Figure 18–4. Schematic representation of glomerular filtration, tubular reabsorption,

and tubular secretion. The renal tubule has been uncoiled, and the peritubular capillaries

are shown adjacent to the tubule.

QUESTION:Describe tubular secretion; that is, it goes from where to where? What sub-

stances may be secreted?