Quiz 5

• In proximal tubule secretion, protons use the apical NHE and ammonium ions use the Na/NH4 antiporter of the apical surface
• Proximal tubule secretion:

  1. Na and HCO3 enter bowman's capsule
  2. Na/H antiport exchanger brings Na into proximal cell and protons out
  3. HCO3 combines with H to make CO2 and water
  4. CO2 diffuses into cells and recombines with water to make H and HCO3
  5. Na and HCO3 use basolateral symporter to be absorbed into the blood
  6. inside cell, glutamine produces NH4 and HCO3
  7. NH4 enter Bowman and Na enters cell using apical exchanger
  8. Na/HCO3 symporter reabsorbs them into blood
• Acidosis:

  • type A intercalated discs
  • high proton concentration in blood (low pH)
  • apical ATPase pumps protons into lumen by bringing in CO2 from blood and K is reabsorbed from lumen
  • K brought back into blood through diffusion
• Excessive hydration:

  1. low blood osmolarity
  2. low ADH secretion
  3. removal of water channels from collecting duct
  4. low water reabsorption by osmosis
  5. large urine volume
• the medullary osmotic gradient is established and maintained by the juxtamedullary nephron and vasa recta and is utilized by the collecting duct to make concentrated urine
• The countercurrent multiplier makes the osmotic gradient to reabsorb water:

  1. ascending limb = actively move NaCl and not water
  2. descending limb = permeable to water, not solutes
  3. papillary duct = reabsorbs urea
• the vasa recta acts as the countercurrent exchanger and passively moves water back to the blood

  • descending = NaCl in
  • ascending = water in
• Testosterone controls internal genetalia and DHT control external
• Female sex production:

  1. gonad cortex becomes the ovary in absence of SRY gene
  2. degeneration of wolfferian duct
  3. mullerian duct becomes the upper vagina, fallopian tubes, and uterus
• Male sex production:

  1. gonad medulla becomes testis in presence of SRY gene
  2. degeneration of mullerian duct
  3. wolfferian duct becomes the seminal vesicle, vas deferen, and epidymus (prostate forms using DHT)
• Testis function:

  1. spermatogenesis
  2. production and secretion of testosterone
• Organic ion proximal tubule secretion:

  1. primary active = Na/K ATPase on basolateral keeps low intracellular NA
  2. secondary active = NaDC contransporter on basolateral and apical sides being Na and dicarbonate inside cell
  3. tertiary active = OAT brings in organic anions and dicarbonate out
  4. apical antiporter = being anions in from the lumen and organic anions into the lumen
• Proximal tubule organic anions:

  1. bile salt
  2. urate
  3. vitamins (folate, ascorbate)
  4. PAH
  5. penicilin
  6. toxic chemicals
• Proximal tubule organic cations:

  1. creatinine
  2. dopamine
  3. epinephrine
  4. atropine
  5. morphine
  6. cimetidine
  7. isoproterenol
  8. procainamide
• Alkalosis:

  • type B intercalated discs
  • low blood proton concentration (high pH)
  • basolateral ATPase brings protons into blood by breaking down CO2 in cell
  • Cl reabsorbed from lumen, while HCO3 and K are excreted
• Aldosterone Na reabsorption is stimulated by:

  1. low blood pressure (renin-ANG II)
  2. high extracellular K
• Aldosterone Na Reabsorption:

  1. aldosterone from blood combines with cytoplasmic receptor
  2. the formed hormone-receptor complex initiates nucleus transcription
  3. translation and protein synthesis form new protein channels and pumps
  4. aldosterone-induced proteins modify existing proteins
  5. increase in Na reabsorption and K secretion
• Spermatogenesis:

  1. spermatogenia (stem cell) = mitosis
  2. primary spermatocyte = first meiosis
  3. secondary spermatocyte = second meiosis
  4. spermatia = differentiate
  5. spermatozoa (lumen)
• Basal compartment is external to the sertoli cells and houses the spermatogenia
• Adluminal compartment includes the lumen and sertoli cells and houses spermatocytes, round spermatids, and immobile spermatozoa
• Loop of Henle reaborption (15% water and 25% NaCl):

  • thin descending = permeable to water, not urea and ions
  • thin ascending = permeable to ions, not water
  • thick ascending = impermeable to water and ions and actively pumps out NaCl
• Distal tubule exchanges K for Na and H for K
• Distal Tubule and Collecting Duct:

  • reabsorbs
  • Na, Cl (aldosterone)
  • water (ADH)
  • secretes
  • K (aldosterone)
  • H (pH)
  • NH4
  • organic ions
  • penicilin
  • creatinine
• Vasopresssin (ADH) is stimulated by:

  1. osmolarity > 280 mOsm
  2. low arterial stretch, due to low blood volume
  3. low blood pressure
• Vasopressin (ADH) in Collecting Duct:

  1. vasopressin from blood binds to basolateral membrane receptor
  2. cAMP is activated and sends a secondary messenger signal
  3. cell inserts aquaporins into apical membrane using storage vesicles
  4. water is absorbed from lumen to blood using osmosis
• Testosterone, secreted by leydig cells, controls the development of wolffian ducts into accessory structures and male external genitalia
• Antimullerain hormone, secreted by sertoli cells, controls the regression of the mullerian duct
• Inhibin, produced by FSH, inhibits FSH, while testosterone inhibits LH and GnRH
• Sertoli cells:

  1. promote and sustain sperm
  2. secrete growth factors
  3. secrete androgen binding protein
  4. blood testis barrier
  5. phagocytosis of defective sperm
  6. production and secretion of hormones
  7. inhibin
  8. MIS
• Leydig cell:

  1. production and secretion of testosterone
  2. gonadogenesis (fetal life)
  3. quiescent (after brith)
  4. sexual maturity (after puberty)
• FSH stimulates sertoli cells to release paracrine agents and secrete ABP
• in response to FSH and testosterone, the sertoli cells support spermatogenesis
• in response to luteinizing hormone, the leydig cells produce steroids, including testosterone
• Pituitary Gonadotropin FSH:

  1. stimulates granulosa cell growth
  2. stimulates key enzyme aromatase
  3. induces LH receptors on the granulosa cell
• Pituitary Gonadotropin LH:

  1. stimulates thecal cell growth
  2. neutralizes peptide oocyte maturation inhibitor
  3. induces pseudo-inflammatory response by activating prostaglandin endoperoxide synthase
  4. stimulates progesterone synthesis
• Ovarian and Uterine Cycle:

  1. follicular ovarian
  2. ovarian follicle growth (menses)
  3. dominant follicle buds on ovary surface (proliferative phase)
  4. ovulation
  5. dominant follicle bursts
  6. luteal ovarian
  7. follicles forming wall remain in ovary and corpus luteum forms (secretory phase)
  8. menstrual flow
• Cyclic Ovarian and Uterine Cycle feedback:

  • negative

  1. low steroid hormone level
  2. secretion of GnRH and gonadotropins
  3. growth of follicle and increased estrogen
  4. dominating follicle outgrows and estrogen levels get too high

  • positive

  1. LH surge stimulates corpus luteum

  • negative

  1. increase in progesterone and estrogen
  2. LH drops
  3. regression of corpus luteum
  4. corpus albicans
• Feedback effects:

  • estrogen in low to moderate concentrations inhibits FSH and LH production
  • inhibin acts to inhibit FSH secretion
  • estrogen in high concentrations has a positive feedback effect to increase LH secretion to decrease FSH, in response to GnRH
  • high concentrations of estrogen and progesterone causes feedback inhibition of GnRH, thus FSH and LH