Ch 17

 Main function: Filter blood and remove salts and nitrogenous waste.  Maintains normal water and electrolyte concentration.  Regulates pH and volume of body fluids.  Controls red blood cell production and blood pressure.

 Kidneys (2) – Remove substances from blood, form urine, and regulate RBC production.  Ureters (2) – Transport urine from kidneys to bladder.  Urinary bladder – Stores urine  Urethra – Conducts urine outside the body

 Location – either side of the vertebral column on posterior wall of the abdominal cavity  High – T12-L3ish Left is slightly higher than right.  Attached to inferior vena cava and abdominal aorta.

 Hilum  Renal sinus – filled with adipose tissue  Renal pelvis – major/minor calyces  Medulla  Cortex – houses nephrons

 Maintain homeostasis Removes wastes from blood and dilute with water and electrolytes to form urine.  Secretes hormone erythropoietin – regulate RBC production  Activates Vitamin D  Maintains blood volume and pressure (enzyme: renin)

 abdominal aorta -> renal arteries -> (kidneys) interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles-> (nephron glomerulus) -> efferent arteriole -> peritubular capillary system -> interlobular vein -> arcuate vein -> interlobar vein -> renal vein (exits kidney) -> inferior vena cava

 Each kidney has about 1 million nephrons.  Two main parts: renal corpuscle and renal tubule.

 Corpuscle –  Glomerulus – filters fluid (step 1 of urine production)  Glomerular capsule – receives filtered fluid

 Tubule  Proximal convoluted tubule  Nephron loop – descending and ascending  Distal convoluted tubule  Collecting Duct

 Juxtaglomerular Apparatus – where ascending loop, afferent, and efferent vessels come together  Involved in renin secretion.

 Urine formation happens through three processes: Glomerular filtration Tubular reabsorption Tubular secretion  Amount of urine = amt. filtered-amt. reabsorbed + amt. secreted

 Glomerular capillaries in glomerulus filter water and other dissolved substances to create glomerular filtrate.  Glomerular filtrate moves to glomerular capsules.

 Pressure is created by hydrostatic pressure of blood.  Pressure is decreased by osmotic pressure of plasma and hydrostatic pressure inside glomerular capsule.  Net filtration pressure = blood’s H-S P – (plasma’s osmotic P + glom.caps’s H-S P)

 Glomerular filtration rate (GFR) – commonly used to measure kidney function.  Affected by changes in diameter of afferent or efferent arterioles.  Can also change due to kidney stones, enlarged prostate gland, etc.

 Filtration Rate Regulation Most of the time, it’s constant. Increases when body fluids are excessive Decreases when body needs to conserve fluids  Controlled by sympathetic nervous system reflexes.  Can also be affected by renin counts.

 From renal tubule back to blood  Changes concentrations in filtrate.  Happens in proximal convoluted tubes using microvilli using carrier proteins.

 Substances reabsorbed: Glucose, amino acids, sodium – active transport Water – osmosis Proteins – pinocytosis Negative ions - diffusion

 From blood back to distal convoluted tubule  Substances secreted: Hydrogen ions and organic compounds – active transport Potassium ions – active and passive transport

 Can be changed by presence of hormones Aldosterone – secreted by adrenal glands (located posteriorly to kidneys); stimulates reabsorption of sodium and secretion of potassium. ADH – secreted by neurons in hypothalamus; responds to decrease in water concentration or blood volume; causes water to be reabsorbed; negative feedback system.  Increased ADH=more water reabsorption  Decreased ADH=less water reabsorption

 Urea – made by amino acid catabolism; reflects amount of protein in diet; 20% leaves/80% reabsorbed  Uric acid – product of metabolism of nucleic acids; small amounts secreted into renal tubule and excreted in urine.

 Determined by the amount of water in diet and plasma.  Changes with changes in diet and metabolic activity.

 Should not have Glucose – sign of diabetes or large glucose intake. Proteins – may be there after strenuous exercise Ketones – after a prolonged fast Blood – sign of disease or disorder

 From collecting tubes in renal medulla  To ureter  To urinary bladder  To urethra

 Ureters - From renal pelvis to bottom of urinary bladder.  Three layers Mucous coat – inside Muscular coat – middle (smooth muscle) Fibrous coat – connective tissue  Flap-like fold acts as valve allowing urine to enter bladder without backflow

 Urinary bladder – hollow, distendable, muscular organ  Stores urine and forces into urethra  Four layers Mucous coat – inner layer (transitional epithelium) Submucous coat Muscular coat – smooth muscle fiber called detrusor muscle Serous coat – outer layer

 Internal urethral sphincter Sustained contraction keeps bladder from emptying Detrusor muscle innervated with parasympathetic nerve fibers  External urethral sphincter Voluntary skeletal muscle

 Micturition – Urination  Stimulated by distension of bladder triggering micturition reflex center Controlled by pons and hypothalamus  Urge felt at about 150 mL  Powerful contractions felt at 300 mL  Pain felt at about 600 mL

 Urethra – tube that conveys urine to outside  Female – 4 cm  Male – shared by urinary and reproductive system

 Kidneys  Ureters  Urinary bladder  Urethra  Renal vein  Renal artery  Distal convoluted tube  Proximal convoluted tube  Nephron loop  Glomerular capsule  Glomerulus  Renal cortex  Renal medullary