Urinary System

Anatomy: Paired kidneys Paired ureters Single bladder Single urethra

Function: Rids the body of nitrogenous waste Regulates blood chemistry

Kidneys Location: Superior lumbar Against dorsal wall Supported by fat cushions

Outside Anatomy Renal Capsule- fibrous, surrounds and protects the kidney Medial Hilus- area where renal arteries, renal vein and ureter attach

Inside anatomy Renal Pelvis- flat basin like cavity – continuous with the ureter Outer Cortex- lighter color outside margins, under the capsule

Renal medulla- deeper, inner portion, darker color Renal Pyramids- cone shaped, base faces cortex, apex (tip) faces inner most area Calyces (calyx)- cup like extensions of the pelvis enclose the tip of the pyramids, collect urine that drains from the pyramids

Blood Supply The kidneys have a rich blood supply ¼ of blood goes through per minute Renal Arteries  Interlobar arteries  arcuate arteries  interlobular arteries Renal Veins  interlobular veins  arcuate veins  interlobar veins

Nephron Functional and structural unit of the kidney 1 million nephrons per kidney In charge of filtering, re- absorption, and excretion

Parts of the Nephron: Glomerulus- a knot of capillaries Renal Tubule- Bowman’s Capsule – cup shaped, completely encloses the glomerulus

The remaining tubule is about 5cm long with 3 regions: -Proximal Convoluted Tubule (desending) -Loop of Henle -Distal Convoluted tubule (ascending)

Most of the nephron is located in the cortex, although the Loop of Henle dips down into the medulla

The collecting tubules receive urine from many nephrons Deliver urine to the calyces  Renal Pelvis  Ureter  Bladder  Urethra  out

Blood Supply The glomerulus is fed and drained by 2 arterioles One feeds in = afferent arteriole One drains out = efferent arteriole The efferent continues to wrap around and cling to the tubules = peritubular bed

The peritubular capillaries cling to the tubules and drains into the interlobular vein

Blood pressure is high in the glomerulus- it is an arteriole going into capillaries It forces fluid and solutes out of the blood That drainage is captured in Bowman’s Capsule

-Red blood cells are too large to be squeezed out -Plasma is 92% water, 8% proteins, salts, sugar, oxygen, CO2, gases

Urine Formation 4 Steps: Step 1: pressure filtration- occurs in the glomelular capsule where things are squeezed out: glucose, amino acids, salts, plasma, and nitrogenous waste

What are nitrogenous wastes? Urea- from amino acid metabolism Creatinine- from muscle metabolism Ammonia- from bacteria Uric Acid- from breakdown of nucleotides

Other waste products: Ketones from fat breakdown Urobilinogen from breakdown of bilirubin (makes urine yellow) Pressure forces water and waste out; large proteins and cells stay

Step 2 Selective Re-absorption- takes some of the molecules (important ones)-glucose, amino acids, salts, water, and returns them to the blood by diffusion or active transport

Step 3 Tubular Secretion- actively removes some waste that could not get squeezed out and moves it from the distal convoluted tubule (drugs)

Step 4 Reabsorption of water- occurs all along, but finally in the nephron’s collecting tubes

Hemodialysis Life saving technology, used when nephrons die Based solely on diffusion

Kidneys contribute to regulation of blood pressure by regulating blood volume

Where salt goes  water follows Based on osmosis

If salt is transported into blood: Water follows Blood volume increases Blood pressure increases

Antidiuretic Hormone (ADH) Secreted by the pituitary gland when sodium has been absorbed but not enough water has followed Causes water to be absorbed Less volume of urine is produced

Atrial Natriuretic Hormone (ANH) Has the opposite effect to ADH When excess volume/pressure goes through the heart, the stretch receptors in the heart detect the excess volume The cells release ANH Keeps sodium (and water) from being reabsorbed Urine volume increases  gets excreted