Urinary System

Organs

• Kidney

  • filters blood

  • retroperitoneal (kidneys are behind the peritoneum)

    • kidney surgeries are done from the back

  • protected by the floating ribs

  • right kidney is lower to make space for the liver

    • used to have 6 kidneys and each set went higher than the last (started from the belt line)

  • Cortex (outer region)

  • Medulla (inner region)

  • Pyramids (inside the medulla)

    • urine is made here →urine drips into the pelvis region

  • Pelvis

    • urine that is dripped here is collected and then later taken out of the kidney by the ureter

  • Calyces - funnel

    • gathers fluid to be stored in the bladder

• Ureter

• Urinary Bladder

  • makes nothing

• Urethra

Kidney Regulation

• blood composition and volume

  • NH2 + H2O→NH3 + OH-

    • lets out ammonia which you need to pee (poisonous)blood pressure & volume

    • blood volume and pressure drops when you pee (brain sends a signal to drink more water to bring it up)

  • blood pH

  • blood calcium concentration

    • if calcium isn’t absorbed it gets peed out

    • kidneys have to absorb it

  • red blood cell concentration

    • if the O2 is too low in blood the kidneys release eurethropoeitin to the blood marrow

Renal Capsule

• Bowman’s Capsule

  • All fenestration happens here

• Glomerulus

Renal Tubules

• proximal convulted tubule - closer to bowman’s capsule

• loop of Henle (descending & ascending)

  • goes into the medulla

• distal convulted tubule - farther from bowman’s capsule

Renal Calculi

• kidney stones ( stops urine from leaving the kidney - poisons it)

Formation of Urine

• Filtration

  • substances forced out through glomerular fenestrations

    • regulating different types of pressure (NFP = 55-30=15)

      • blood pressure (positive pressure ~55mmHg)

      • osmotic pressure (positive pressure ~30mmHg)

      • capsular pessure (negative pressure ~15mmHg)

  • amino acids, glucose, H2O, Na, HCO, PO4, urea

  • Glomelular Filtration Rate - how fast you make pee

• Reabsorption - 99% is absorbed, 1% is the poison that you don’t want to reabsorb

  • getting back the good stuff back into the blood stream

    • uses ATP + a lot of diffusion and osmosis

  • PCT ~ 65%

    • has microville - increases surface area which allows it to reclaim more things faster

  • loop of Henle ~15%

  • DCT + collecting duct 19% = 99%

• Secretion

  • moving large, unfiltered and reabosrbed toxins back into the renal tubules

    • eliminated nitrogenous wastes : urea and uric acid (was reabsorbed)

    • rids the body of excess K+ (was reabsorbed)

    • contrpl pH (secretes more H+)

    • allows molecules too big to be filtered to leave the body

Composition of Urine

• 95% water

• 5% solids

  • mostly urea, uric acid, and creatinine

  • ions: K+, Na+, phosphate and sulfate

• pH 6, can go as high as 8

• slightly aromatic (if left standing forms NH3)

Ureters (tubes leaving kidneys)

• slender muscular tubes conveying urine into the bladder via pertistalsis

• ~6-8 mm diameter proximal

• ~2.2-1.8 mm distal

Urinary Bladder

• storage for urine

• detrusor muscle - aids in mictrurition

Trigone (region of most bacterial infections)

• where two ureters enter the bladder and the urethra exits

Urethra

• drains urine from the bladder

• ~8-9 mm diameter

• external urethral sphincter (voluntary)

• internal urethral sphincter (involuntary)

Regulating Blood Pressure

• juxtaglomerular cells (baroreceptors)

  • cover afferent arteriole

• macula densa cells (chemoreceptors)

  • in between afferent and efferent arteriole

High Blood Pressure

• myogenic mechanism - triggered causing smooth muscles of artioles to contract

• too little Na+ and Cl- is reclaimed strimulating the macula densa cells to inhibit nitric oxide from juxtaglomular apparatus causing arterioles to constrict

Low Blood Pressure

• juxtaglomerular cells do not stretch (afferent arteriole does not fill as much)

  • release renin

    • catalyst - converts plasma protein angeiotensinogen →angiotensin I

    • angiotensin converting enzyme can converts angiotensin I →angiotensin II (very powerful vasocontrictor)

• blood flow slows in the glomerulus (GFR is too slow - too much reabsorption)

• brain releases antidiuretic (retains water)

• adrenal glands release aldosterone (retains sodium)

Chronic Hypertension

• can cause damage to renal vessels (vessels are constricting but blood is still trying to flow through)

• nephrons don’t receive adequate oxygen

• less blood is filtered

• fluid is retained

• blood pressure rises