urinary system

Cards (46)

  • The glomeruli create about 200 liters of filtrate each day, we excrete 1 - 2 liters though
  • Signs of dehydration
    • Darker urine
    • Slight scent of ammonia
    • May urinate less often
  • Urine color changes
    • Pink or bright red (kidney stone or cancer)
  • Some foods may change urine aroma, but they are harmless
  • A minimum of 500ml of urine each day is required to remove wastes
  • pH
    Can range from 4.58.0
  • Specific gravity
    The number of solutes per unit volume, pure water = 1.0
  • Polyuria
    • >2.5 L/day – diabetes mellitus, diabetes insipidus, excess water, caffeine, or alcohol, kidney disease, certain drugs (diuretics), sickle cell anemia
  • Oliguria
    • 300-500 mL/day – dehydration, blood loss, diarrhea, cardiogenic shock, kidney disease, enlarged prostate
  • Anuria
    • <50 mL/day – kidney failure, obstruction (stone or tumor), enlarged prostate
  • The presence of leukocytes may indicate a urinary tract infection
  • Trace protein in urine is ok, but excessive protein usually means damage to the glomerulus
  • Ketones may be seen in urine in a diabetic or someone eating a very high fat diet
  • Nitrates occur naturally in urine, but nitrite may be evidence of an infection
  • Blood should only appear in the urine in sample resulting from menstrual contamination
  • Urethra
    • Transports urine from bladder to outside of body, internal and external sphincters
    • Females – 4 cm long, less of a barrier for infection
    • Males – passes through prostate gland, average of 20 cm long, has 4 sections (preprostatic, prostatic, membranous, and spongy or penile urethra)
  • Bladder
    • Collects urine from both ureters, highly distensible
    • Compressed by enlarged uterus or prostate causing more frequent urination
    • Can hold 500-600 mL
    • Micturition reflex – the urge to urinate with about 150 mL of fluid, easily controlled
  • Ureters
    • Propels urine by peristalsis from the kidney to the bladder, 1 way valve to prevent reflux
    • About 30 cm long, coated with protective mucous from goblet cells
  • Kidneys
    • Lie on either side of the spine well protected by muscle, fat, and ribs
    • They are about the size of your fist, male is typically larger
    • They receive 25% of cardiac output at rest
    • Right kidney is a little lower due to displacement by the liver
    • An adrenal gland sits atop each kidney
  • Internal Anatomy of Kidney
    • Outer cortex
    • Inner medulla containing papillae and pyramids separated by columns to form lobes
    • Papillae drain into calyces for excretion
  • Renal Hilum
    • Entry and exit for vessels, nerves, lymphatics, and ureters
    • Renal pelvis funnels urine into ureters by peristalsis
    • Arteries branch multiple times and eventually become afferent arterioles that service about 1.3 million nephrons in each kidney
  • Nephron
    • Functional unit of the kidney, cleanse blood and balance constituents
    • Afferent arteriole becomes the glomerulus which sits next to Bowman's capsule and together they form the renal corpuscle
    • After the glomerulus the vessel becomes the efferent arteriole and it forms a network around the nephron before returning to the venous system
    • The network is there to recover water and solutes that need to be reabsorbed into circulation
  • Microscopic Anatomy of the Kidney
    • Nephrons take filtrate of the blood and form urine
    • Main task is to maintain homeostatic balance of plasma and excrete potential toxins
    • Nephrons filter, reabsorb, and secrete
    • Also adjust BP, RBC production, and calcium absorption
    • Renal corpuscle – high pressure glomerulus pushes solutes through filtration slits and into the Bowman's capsule, filtration slits match up with fenestrations along capillary
    • Bowman's capsule forms a lumen and directs fluid to the Proximal Convoluted Tubule (PCT)
    • 10-20% of plasma filters through the filtration slits
    • Fenestrations prevent blood cells and large proteins from passing out of glomerulus
    • Proteins associated with pores are slightly negative so more positive substances can get
  • Macula densa
    • Part of DCT, measures sodium and flow rate
    • They release ATP and adenosine in response to changes in flow rate and sodium
    • Juxtaglomerular cell will contract or relax based on osmolarity of plasma fluid
    • Macula densa also regulates renin release
  • Proximal Convoluted Tubule
    • Between Bowman's capsule and Loop of Henle, simple cuboidal cells with prominent microvilli for efficient absorption and secretion of solutes, lots of mitochondria for active transport
  • Loop of Henle
    • Descending and ascending portions, thick cuboidal cells and thin simple squamous cells closest to peak of loop
  • Distal Convoluted Tubule (DCT)
    • Much like PCT just shorter and with fewer microvilli
  • Collecting Ducts
    • Collects filtrate from several nephrons, they merge in the medulla and form about 30 terminal ducts which empty at the papilla, lined with ADH receptors to insert aquaporin channel proteins into their membranes
  • Glomerular Filtration Rate (GFR)

    Volume of filtrate formed per minute, 99% gets reabsorbed
  • Filtrate is formed due to blood hydrostatic pressure in the glomerulus
  • Systemic edema – to much protein is pushed into filtrate, lower osmotic pressure in circulating blood, water leaves capillaries more causing the body to "plump up"
  • Smooth muscle contracts or relaxes to maintain consistent blood flow into glomerulus, if BP falls to much then renal function will be impaired and shock is possible
  • GFR is often estimated by measuring creatinine in the urine
  • Tubular Reabsorption
    • Substances are reabsorbed by active transport, diffusion, facilitated diffusion, secondary active transport, and osmosis
    • Symport mechanism – 2 or more substances cross the membrane in the same direction at the same time
    • Antiport mechanism – 2 or more substances move in opposite directions across the membrane at the same time
  • Proximal Convoluted Terminal (PCT)
    • Sodium is actively pumped out and water is obliged to follow
    • Sodium is symport with chloride, calcium, amino acids, glucose, and phosphate
    • Sodium is antiport with potassium on basal membrane
    • 67% of water, sodium, and potassium are reabsorbed
    • Almost 100 % of glucose, amino acids, and vitamins are reabsorbed
    • Hydrogen ions are recycled so bicarbonate can be recovered
  • Loop Of Henle
    • 2 sections – thick and thin descending and ascending sections
    • Descending loop – permanent aquaporin channel proteins to reabsorb 15% of entering water, about 82% of solutes all ready recovered
    • Ascending loop – Sodium ions are actively pumped out, chloride also gets out through leaky tight junctions causing the interstitial space to be negatively charged compared to the lumen, electromagnetic gradient attracts sodium, calcium, potassium, and magnesium
    • Blood flow is slow to allow proper time to balance nutrients and water for homeostasis
  • Distal Convoluted Tubule (DCT)
    • Aldosterone increases sodium reabsorption
    • Parathyroid hormone will cause a calcium channel in the luminal surface
    • Calcitriol induces the production of calcium-binding proteins to reabsorb Ca++
    • No more Ca++ can be reabsorbed beyond this point
  • Collecting Ducts
    • Regulation of water reabsorption is controlled by Anti Diuretic Hormone (ADH)
    • The amount of aquaporin channels is related to the osmolarity of the blood
    • Also receptors for aldosterone to control Na+ reabsorption
    • Intercalated cells secrete hydrogen ions to lower plasma acidity and raise urine acidity
  • Regulation of Renal Blood Flow
    • Reducing sympathetic stimulation increases blood flow and vice versa
    • The kidney auto regulates filtration rate very well despite changes in BP
    • Myogenic mechanism – a stretch in a smooth muscle causes it to contract, like if BP increases in glomerulus
    • Tubuloglomerular Feedback – releases ATP and adenosine due to Na+ reabsorption rate and flow rate
  • Endocrine Regulation Of Kidney Function
    • Renin-Angiotensin-Aldosterone – increases BP by vasoconstriction and reabsorption of Na+
    • Aldosterone receptors can be triggered by progesterone and cortisol
    • ADH – promotes water recovery, opposite of a diuretic (coffee, tea, alcohol)
    • Endothelins – powerful vasoconstrictors that are released due to angiotensinogen 2, bradykinin, and epinephrine. Chronically elevated in diabetic kidney disease
    • Natriuretic Hormone – opposite of aldosterone, causes Na+ secretion
    • Parathyroid Hormone – causes increase in Ca++ reabsorption and blocks reabsorption of phosphate