Reproductive System PDF

PHA106 Pharmaceutical Biosciences 1 REPRODUCTIVE SYSTEM  Learning outcomes  Understanding of male anatomy  Knowledge of structure of the testes and spermatogenesis  Hormonal regulation  Understanding of female anatomy  Knowledge of structure of the ovaries and oogenesis ...

PHA106 Pharmaceutical Biosciences 1 REPRODUCTIVE SYSTEM  Learning outcomes  Understanding of male anatomy  Knowledge of structure of the testes and spermatogenesis  Hormonal regulation  Understanding of female anatomy  Knowledge of structure of the ovaries and oogenesis  Ovarian cycle and uterine cycle  Hormonal regulation  Reproductive system  Function is to produce, store, nourish and transport male and female gametes  Basic components:  Gonads or reproductive organs  Produce gametes and hormones  Ducts which receive and transport gametes  Accessory glands and organs  External genitalia  Male reproductive system  Spermatozoa form in the testes (main gamete)  Travel through epididymis in testes, along vas deferens and exit body via urethra  Seminal vesicle, prostate gland and bulbourethral gland produce fluids which act as lubricants.  Structure of the testes  Each of the testes is made up of a series of lobules,  Each lobule contains ~800 tightly coiled seminiferous tubules (ST) – makes sperm  Spermatogenesis takes place here – sperm production  It begins in the outermost layer of cells and proceed towards the lumen  Seminiferous tubules merge into straight tubules  Merge to from rete testis which connect to the epididymis, connects to vas def, transports sperm  Spermatogenesis  3 integrated processes  Mitosis  Spermatogonium (stem cell- population of cells that keep replenishing cells) divides – one daughter cells remains in situ, the other matures and moves towards the lumen of the Seminiferous Tube  Transforms into primary spermatocyte – 2N chromosomes  Meiosis (chromosomes divided up )  Division of spermatocyte produces spermatids  Cell goes from 2N to 1N chromosome  Spermiogenesis  Spermatids differentiate/ change into physically mature spermatozoa  These are released into lumen of Seminiferous Tube  Spermatozoon/ sperm  3 distinct regions  Head  Contains nucleus with densely packed chromosomes (most important genetically)  Acrosome – contains enzymes essential to fertilisation, uses enzymes to break down surface of egg to allow sperm head to get into egg and mix chromosomes for fertilisation  Midpiece  Contains abundant mitochondria (powerhouse of cell, produce ATP, gives energy.  They have to swim a long way so they need lots of energy  Tail - movement  Flagellum, only example of flagellum in human body (structure similar cilia)flagella whip/ propell sperm forward in a circular motion  No ER, Golgi, lysosomes etc.  Reduces physical size and mass – therefore there are no stores of anything like glucose or anything for respiration to occur, so they have to take in food source from outside surrounding, has high conc of fructose which cell will use in ____ to produce ATP to allow them to move  Accessory glands  Seminal vesicle  60% volume of semen  Fluid contains high conc. of fructose ( bathes in this fluid, food source)  Slightly alkaline seminal fluid neutralises acid secretions of prostate and vagina to neutrilise the acidic urine , alkaline helps neutrilise the pH in female also so semen not damaged  Prostate gland  20-30% volume of semen  Encircles urethra  Contains seminalplasmin protein with antibiotic properties, prevents infection in male reproductive system.  Bulbourethral gland  Produce thick, alkaline mucus – nutrilise any remaining unire acidic  Neutralises any remaining urinary acids  Hormonal regulation  Hypothalamus releases gonadotrophin releasing hormone (GnRH)  Stimulates pituitary to produce follicle stimulating hormone (FSH) and luteinising hormone (LH), they will be released in blood and tell testes to release testosterone  Act on testes to produce testosterone  Maintains libido  Stimulates osteogenesis and myogenesis – men more muscular  Maintains male secondary sex characteristics, facial hair, prostate glands  Maintains male accessory glands  Female reproductive system  Produces sex hormones and gametes  Also protects and supports developing foetus  Oogenesis occurs in the ovaries  Uterine or fallopian tubes  Uterus  Vagina  Structure of the ovaries  Pair of small, pale, lumpy, almond-shaped organs  Ovarian ligament stabilises their position relative to the uterus  Produce oocytes (eggs)  Does this by Oogenesis  Ovarys Secrete female sex hormones – eostrogen and progesterone  Oogenesis  Oogonium divides by mitosis to produce primary oocytes  Primary oocytes prepare to undergo meiosis – proceed to meiosis 1  Held in suspended development until puberty  Rising levels of FSH at puberty trigger the ovarian cycle which allow primary oocytes to do step 2^  Some primary oocytes complete meiosis I to form secondary oocytes  Secondary oocytes leave ovary suspended in metaphase of meiosis II  Meiosis will not be completed until fertilisation occurs  Ovarian cycle Follicular phase  Primary oocytes in outer portion of ovarian cortex(outer layer)live in egg nests – forms primordial follicle with follicle cells  Primary follicle develops – follicular cells divide to produce granulosa cells  Layer of thecal cells develops around follicle (eostrogen produced  Mature graafian follicle formed – LH levels rise and primary oocyte completes meiosis I – 1N cell formed  At ovulation, secondary oocyte released from graafian follicle into fallopian tube, can be fertilised if sperm there  Ovarian cycle Luteal phase  Empty graafian follicle(egg released) collapses and develops into corpus luteum (CL) – endocrine function – produces hormones.  Cholesterol in CL used to synthesise progesterone  Progesterone prepares uterus for pregnancy to make the layer nice and deep and comfy  CL degenerates if fertilisation doesn’t occur  Progesterone and oestrogen levels fall and go back to normal  If fertilisation occurs, CL continues to produce progesterone which maintains uterine lining  Placenta eventually takes over producing progesterone production and CL degrades/ degenerates oestrogen  Uterus  Protects, nourishes (developing embryo/ feutus) and removes wastes from the developing foetus  Cervix at base of uterus, projects into vagina  Uterine wall composed of:  Myometrium – thick, middle layer – contracts during labour  Endometrium - thin, inner layer – thickens to allow embryo to implant  Uterine cycle changes in structure of endothelium  ~28 days long  Uterine cycle  Menses / menstration  Degeneration of endometrium, removing of tissue  Sloughing off of tissue  Proliferative phase  Oestrogens secreted by developing follicles stimulate growth  Secretory phase  Progesterone makes the endometrium receptive to implantation of the blastocyst  Makes environment more receptive ?  Hormonal regulation  Hypothalamus releases GnRH  Stimulates pituitary to produce and secrete FSH and LH  FSH stimulates follicle development and secretion of oestrogen  Also stimulates LH secretion  LH secretion triggers meiosis 1 completion, ovulation and corpus luteum formation  Age-related changes  Male changes  Andropause -  Levels of circulating testosterone fall, because FSH and LH levels have fallen  Decrease in Sperm production but still continues to produce less high conc  Female changes  Menopause  Ovulation and menses cease  Levels of circulating oestrogen, progesterone fall, because FSH and LH have fallen  Osteoporosis can develop  Summary  Male anatomy  Structure of the testes and process of spermatogenesis  Hormonal regulation  Female anatomy  Structure of the ovaries and process of oogenesis  Ovarian cycle and uterine cycle  Hormonal regulation  Additional reading Martini 11th edn. Chapter 28