1. CHAPTER 21: URINARY SYSTEM Miss Hillemann Human Anatomy & Physiology Neshaminy High School

2. Urinary System Nephrology: study of the anatomy, physiology, and disorders of the kidneys. Urology: branch of medicine that deal with the male and female urinary systems and the male reproductive systems. Urologist: physician who specializes in this field.

3. Components of the Urinary System 2 kidneys- filter the blood and return most of the water and solutes to the bloodstream 2 ureters- passageway for urine from the collecting tubules in the kidney to the urinary bladder 1 urinary bladder- stores urine 1 urethra- expels the urine

4. Functions of the Urinary System Regulation of ion levels in the blood Regulation of blood volume and blood pressure. Regulation of blood pH Production of hormones. ◦ Calcitriol (active form of vitamin D)- regulate calcium homeostasis ◦ Erythropoietin- stimulates production of RBCs Excretion of wastes. ◦ Ammonia, urea, bilirubin, creatinine, and uric acid.

5. Structure of the Kidneys Pair of reddish kidney-shaped organs 2 Main Regions: 1.Renal cortex: outer light-red region  Renal columns-extensions of the renal cortex fill the spaces between the renal pyramids 2.Renal medulla: inner, dark red-brown region  Several cone-shaped renal pyramids

6. Nephrons functional units of the kidney About a million in each kidney Number of nephrons is constant from birth. Two parts: 1.Renal corpuscle: where blood is filtered a)Glomerulus b)Glomerular (Bowman’s) capsule 2.Renal tubule: where the filtered fluid (glomoerular filtrate) passes

7. Nephron (cont’d) 3 parts of the renal tubule: 1.Proximal convoluted tubule: attached to the glomerular capsule. Convoluted= Tightly coiled. Reabsorbs most of the water and glucose from glomerular filtrate. 2.Loop of Henle: a)Descending limb of the loop of Henle b)Ascending limb of the loop of Henle 3.Distal convoluted tubule: farthest away from the glomerular capsule

9. Formation of Urine 1. Glomerular filtration: blood pressure forces water and solutes in blood plasma across the wall of glomerular capillaries, forming glomerular filtrate. 2. Tubular re-absorption: tubule and duct cells return ~99% of the filtered water and useful solutes to the blood through peritubular capillaries 3. Tubular secretion: tubule and duct cells remove wastes, drugs and excess ions from blood in peritubular capillaries and transport them into the fluid in the renal tubules.

10. URINE FORMATION

11. Antidiuretic Hormone (ADH) Produced by the posterior pituitary Acts on tubule cells in the last part of the distal convoluted tubules and throughout the collecting ducts Increases facultative water reabsorption Decreases urine production Stimuli for ADH secretion: ◦ Concentration of water in blood decreases ◦ Decrease in blood volume

12. Negative feedback regulation of water reabsorption by ADH