BISC 307L 1st Edition Lecture 19 Current Lecture Calcium Balance Hormones that Regulate Body Calcium o o There are 3 that regulate 1 Parathyroid hormone released from the parathyroid glands embedded in posterior view of thyroid gland essential for life function to raise plasma Ca2 2 Calcitriol or vitamin D3 steroid hormone made 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 Balance o o Top white area small intestine Source of new calcium added to the body by absorption of dietary calcium Two fates Stays in small intestine and excreted Or absorbed into extracellular tissue o Bone at left Bone is important reservoir for calcium Calcium can be taken from the EC fluid and deposited in the bones This causes new bone formation the cells that do this are called osteoblasts Osteoclasts break down the bone and liberate calcium moves calcium back into ECF o Right Kidney Calcium is filtered in the kidney tubule Can be not reabsorbed and passes in the urine or it can be reabsorbed and put back into the ECF o Parathyroid hormone 3 ways to raise calcium plasma 1 strongly stimulates bone reabsorption activity of osteoclasts in freeing calcium 2 Reabsorption of calcium back into the blood in kidney this also lowers plasma phosphate 3 Indirectly stimulates the synthesis of calcitriol o Calcitriol 1 Raises absorption in the small intestine of calcium 2 Stimulates bone reabsorption o Cortisol Has affect on raising plasma Ca2 o Prolactin Also raises plasma Ca2 in women for stimulating milk Reabsorption 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 calcium o Calcitonin Lowers plasma calcium By counteracting affects of PTH Stimulates bone deposition osteoblasts Inhibits calcium reabsorption in the kidney passes out in urine Not important as much in adults but in children and lactating women it does Children where bones are growing rapidly necessary for bone growth During 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 mechanism Reproduction 1 Overview of Sexual Differentiation Part 1 o o Reproductive system is the one place where the main message is not to maintain homeostasis but rather to just prolong the species o Systems that guarantee the relative constancy of the species not the individual o Humans have 22 pairs of autosomal chromosomes and one pair of sex chromosomes Gender depends on whether the sperm carries X or Y chromosome Y chromosome carries sex linked genes o Three important cell types in the undifferentiated gonads 1 Germ cells 2 Coelomic epithelium 3 Mesencyme under the influence of the male chromosome cause the differentiation of these cells into 1 Spermatogonia 2 Sertoli cells 3 Leydig cells get to work quickly secrete testosterone In the absence of Y chromosome these cells will become 1 Oogonia 2 Granulosa 3 Theca cells Overview of Sexual Differentiation Part 2 o o Left Leydig cells start to secrete testosterone which causes 1 Wolffian ducts to form the male reproductive tract 2 Development of external genetalia Sertoli cells Secrete antimullerian hormone which causes the precursor to the female reproductive system to be destroyed o Right default condition Theca cells do not secrete testosterone without testosterone the wollfian cells degenerate and external genitalia remains not external becomes the female reproductive tract Bipotential Development of External Genitalia o at 6 weeks see the undifferentiated genital tubule urethral tubule urethral fold and scrotal swellings so cant tell difference o 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 clitoris o under 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 penis Endocrine Control of Sexual Maturation o o General control Hypothalamus 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 pituitary o Male sexual function Testes 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 yet There 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 reproduction At 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 nightnecessary to keep the receptors from disappearing results in pulses of LH and FSH which stimulates the testes to do their thing Skip ahead 30 40 years to the climacteric stage of transition from sexually active to not sexually active more abrupt in womenmenopause 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 Anatomy o o Testes 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 scrotum