Calcium BalanceHormones that Regulate Body CalciumThere are 3 that regulate1. Parathyroid hormone +released from the parathyroid glands embedded in posterior view of thyroid glandessential for life*function to raise plasma Ca2+2. Calcitriol (or vitamin D3) +steroid hormonemade from vitamin D (made in skin or dietary)liver cells take this vitamin D and convert it to intermediate and kidney takes this intermediate and converts it into calcitriol*raises plasma Ca2+3. Calcitonin (-)made by C cells in the thyroid gland*lowers plasma Ca2+Calcium BalanceTop white area: small intestineSource of new calcium added to the body (by absorption of dietary calcium)Two fates:Stays in small intestine and excretedOr absorbed into extracellular tissueBone at left:Bone is important reservoir for calciumCalcium can be taken from the EC fluid and deposited in the bonesThis causes new bone formation- the cells that do this are called osteoblastsOsteoclasts break down the bone and liberate calciummoves calcium back into ECFRight: KidneyCalcium is filtered in the kidney tubuleCan be not reabsorbed and passes in the urine or it can be reabsorbed and put back into the ECFParathyroid hormone: 3 ways to raise calcium plasma1.strongly stimulates bone reabsorption (activity of osteoclasts in freeing calcium2. Reabsorption of calcium back into the blood in kidneythis also lowers plasma phosphate3. Indirectly stimulates the synthesis of calcitriolCalcitriol1. Raises absorption in the small intestine of calcium2. Stimulates bone reabsorptionCortisol:Has affect on raising plasma Ca2+ProlactinAlso raises plasma Ca2+ in women for stimulating milkReabsorption of calcium from digestive tractimportant in women ensures that the calcium for lactation is not provided at the expense of bone strength but is rather new calciumCalcitoninLowers plasma calciumBy counteracting affects of PTHStimulates bone deposition (osteoblasts)Inhibits calcium reabsorption in the kidneypasses out in urineNot important as much in adults but in children and lactating women it doesChildren where bones are growing rapidlynecessary for bone growthDuring pregnancy there is extra demand for calcium and calcitonin is high because stimulation of bone growth protects mothers bones from osteoporosis (does not lower plasma calcium though because there is increased secretion of calcitriol and prolactin)- purely used as a bone protection mechanismReproduction 1Overview of Sexual Differentiation- Part 1Reproductive system is the one place where the main message is not to maintain homeostasis but rather to just prolong the speciesSystems that guarantee the relative constancy of the species not the individualHumans have 22 pairs of autosomal chromosomes and one pair of sex chromosomesGender depends on whether the sperm carries X or Y chromosomeY chromosome carries sex linked genesThree important cell types in the undifferentiated gonads:1. Germ cells2. Coelomic epithelium3. Mesencymeunder the influence of the male chromosome cause the differentiation of these cells into1. Spermatogonia2. Sertoli cells3. Leydig cellsget to work quicklysecrete testosteroneIn the absence of Y chromosome these cells will become1. Oogonia2. Granulosa3. Theca cellsOverview of Sexual Differentiation- Part 2LeftLeydig cells start to secrete testosterone which causes:1. Wolffian ducts to form the male reproductive tract2. Development of external genetaliaSertoli cellsSecrete antimullerian hormone which causes the precursor to the female reproductive system to be destroyedRight : default conditionTheca cells do not secrete testosteronewithout testosterone the wollfian cells degenerate and external genitalia remains not externalbecomes the female reproductive tractBipotential Development of External Genitaliaat 6 weeks see the undifferentiatedgenital tubule, urethral tubule, urethral fold and scrotal swellingsso cant tell difference.in female condition the genital tubule becomes the clitorisurethral folds stay where they arethe labial scrotal swellings do not grow except forming the clitorisunder influence of testosteronedevelopment of the malegenital tubule glands of the penisurethral folds will grow out towards you and close the channel becoming the penile part of the urethrascrotal swellings become the scrotum and the prepuce of the penisEndocrine Control of Sexual MaturationGeneral controlHypothalamus releases GnRHstimulates two cells in anterior pituitary to release LH and FSH (gonadotropins)stimulate the growth of gonads (testes and ovaries)the ovaries secrete progesterone and estradiolthe testes secrete testosteroneboth of them secrete inhibins and activins (peptide hormones) which only activate or inhibit FSH secretion from the anterior pituitaryMale sexual functionTestes secrete testosterone during fetal life but at around the time of birth the testes stop doing this because continued secretion of testosterone becomes dependent on the gonadotropins which haven’t been secreted yetThere’s a 10-13 year period in which testosterone is not secreted and then is secreted again (puberty is happening earlier now). This delay is important because the individual must be capable of sustaining themselves and the body ahs to grow to a certain stature to ensure a reasonable success for reproductionAt puberty the testes become active- due to the hypothalamus starting to secrete more GnRH which will stimulate the anterior pituitary to secrete gonadotropins (secreted in pulses mostly at night-necessary to keep the receptors from disappearing)results in pulses of LH and FSH which stimulates the testes to do their thingSkip ahead 30-40 years to the climacteric- stage of transition from sexually active to not sexually active (more abrupt in women-menopause) In males the spermatogenesis is gradually declined. This starts around age 50 for men and then continues for decades (rather than a few years for women)Male Reproductive AnatomyTestes and ovaries in both males and females differentiate up in the abdomen – in females they stay there but in males they take a long path by trailing the wollfian ducts and passes through a hole which it can pass and get into the scrotumBISC 307L 1st Edition Lecture 19 Current Lecture Calcium Balance- Hormones that Regulate Body Calciumoo There are 3 that regulate 1. Parathyroid hormone + released from the parathyroid glands embedded in posterior view of thyroid gland essential for