Chapter 27: The Reproductive System PDF

The Reproductive System Chapter 27 27.1 – Anatomy and Physiology of the Male Reproductive System › Gamete – specialized sex cell carrying 23 chromosomes › Sperm – male gamete › Oocyte – female gamete › Testes – produce sperm and androgens to support reproduction, located inside the scrotum to stay 2...

The Reproductive System Chapter 27 27.1 – Anatomy and Physiology of the Male Reproductive System › Gamete – specialized sex cell carrying 23 chromosomes › Sperm – male gamete › Oocyte – female gamete › Testes – produce sperm and androgens to support reproduction, located inside the scrotum to stay 2-4 degrees cooler than body temperature › Dartos and cremaster muscles contract or relax to raise or lower the testes 27.1- Testes › Male gonads – reproductive organs, paired, 2 layers › Tunica vaginalis – serous membrane, outer layer › Tunica albuginea – tough connective tissue, covers entire testes and separates them into 300-400 lobules › Seminiferous tubules – where sperm develops inside the lobules, tightly coiled › Testes descend at about month 7 in the womb › Cryptorchidism – testes fail to descend before birth 27.1 › Sertoli Cells – promote sperm production and can eliminate germ cells too, they create the blood-testis barrier due to tight junctions › Spermatogonia – stem cells or germ cells of the testes › Spermatogenesis – process of producing sperm in the seminiferous tubules, begins at puberty, 1 cycle takes 64 days and a cycle starts every 16 days. Produces 4 haploid daughter cells (spermatids) 27.1 – Structure of Formed Sperm › Smaller than most cells, 85,000 times less volume than female gamete, produce 100 - 300 million each day › Head – haploid nucleus and little cytoplasm, covered in lysosomal enzymes in the acrosome › Mid-piece – tightly packed mitochondria › Tail – flagellum for movement or motility 27.1 – Sperm Travel › Start in seminiferous tubules and move via fluid to epididymis, takes 12 days to move through epididymis › Epididymis – 6 meters long, tightly coiled, continues maturation, sperm are moved by smooth muscle until the tail fully develops, sperm are stored in the tail of the epididymis until ejaculation occurs › Duct system – sperm exit and are pushed to ductus deferens (thick muscular tube, part of spermatic cord) › Ampulla – where the duct ends, posterior to bladder 27.1 › Seminal Vesicles – glands that contribute 60% of semen volume, lots of fructose for ATP. Meets sperm in ejaculatory duct › Prostate gland – as big as a walnut, muscle and gland tissue, secretes fluid to coagulate the semen which will later de-coagulate in the female, prostate size doubles at puberty and gradually grows after age 25 › Benign prostatic hyperplasia (BPH) – prostate gets to big (urge to urinate, weak stream, discomfort) › Prostate cancer – 2nd most common in men. Detected by Hx, blood test, and rectal exam 27.1 › Bulbourethral Glands – final addition to semen, thick and salty fluid to lubricate end of urethra and vagina and clean urine residue, comes after arousal and before semen release (can cause pregnancy) 27.1 - Penis › 3 chambers surrounding the urethra fill with blood (vasocongestion) during arousal and REM sleep › Nitric oxide (NO) is released to dilate blood vessels and rapidly increase blood volume to fill chambers › The filled chambers put pressure on venules preventing drainage 27.1 - Testosterone › Secreted by 7th week of development to differentiate male sexual organs, increases again at puberty › Keeps male reproductive system working properly, produce 6 – 7 mg/day, low levels lead to infertility › Muscle development, bone growth, secondary sex characteristics, and libido in men and women › Ovaries and adrenal glands secrete a small amount › Controlled by hypothalamus and pituitary gland, GnRH stimulates release of LH and FSH 27.1 › FSH – stimulates spermatogenesis and the release of inhibin › LH – upregulates the production of testosterone 27.2 – Female Reproductive System › Produce gametes and hormones as well as support and deliver a developing fetus to the world › Primarily inside the pelvic cavity › Ovaries – female gonads › Oocyte – gamete produced in females › Vulva – external reproductive structures › Labia minora – protect reproductive tract and urethra 27.2 › Clitoris – from same cells as penis, has abundant nerve innervation › Hymen – thin membrane that partially covers the vagina › Vagina – muscular canal, entrance to reproductive tract, exit for fetus, expands for intercourse and childbirth, acidic pH make it a self cleaning organ 27.2 - Ovaries › Paired gonads the size of an almond › Attached to uterus by ovarian ligament › Superficial ovarian epithelium covers dense tunica albuginea › Oocytes develop in the outer layer of the cortex › Follicle – supporting cells surrounding the oocyte › Ovarian medulla – blood vessels, lymph vessels, and nerves of the ovary 27.2 – Ovarian Cycle › About 28 days, not the same as menstrual cycle › Only during reproductive years › Has 2 interrelated processes › Oogenesis – production of female gamete › Folliculogenesis – growth and development of follicles 27.2 Ovarian Cycle › Follicular Phase – follicles mature and get ready to release an oocyte › Ovulation – the release of a mature oocyte › Luteal Phase – the dominant follicle becomes the corpus luteum and produces lots of progesterone 27.2 - Oogenesis › Oogonia – ovarian stem cell, divide by mitosis, formed during fetal development › Primary oocytes halt development until puberty and they last until menopause › 1-2 million in an infant, 400,000 at puberty, 0 at menopause › Ovulation – releasing an oocyte from the ovary › Cells divide unequally and only 1 cell is large enough to become a mature ovum, other 3 are polar bodies 27.2 › Secondary oocyte only divides if penetrated by sperm › Large amount of cytoplasm has nutrients to last from fertilization until implantation, sperm only brings DNA 27.2 - Folliculogenesis › Normally leads to ovulation every 28 days and death to multiple other follicles › Atresia – death of ovarian follicles › A few primordial follicles respond to recruitment each day and become primary follicles › Primary follicles increase in size and become secondary follicles › Oocyte secretes a membrane to increase size and now we have a tertiary follicle 27.2 › Many follicles reach tertiary stage at once, but normally only 1 can survive and the others die › The 1 that survives grows until ovulation and then it will expel its secondary oocyte from the ovary 27.2 › From primordial follicle to tertiary follicle takes about 2 months › Regulated by GnRH, LH, FSH › FSH – stimulate follicles to grow › LH – stimulates follicle cells to produce estradiol, a type of estrogen › Follicular phase – tertiary follicles are growing and secreting estrogen 27.2 › A larger follicle produces more estrogen › More estrogen causes the hypothalamus to reduce production of GnRH, FSH, and LH › The decline of FSH causes most follicles to die › 1 dominant follicle survives to release an oocyte › Dominant follicle depends on size, number of cells, and number of FSH receptors › Dominant follicle will produce more estrogen then previous follicles put together 27.2 › High amount of estrogen breaks the negative feedback loop and FSH and LH are secreted › Now there is a positive feedback loop and the surge of LH leads to ovulation › Enzymes breakdown proteins in the ovary wall › Collapsed follicle becomes the corpus luteum which produces large amounts of progesterone › Progesterone re-establishes the negative feedback to the hypothalamus 27.2 › Implantation must happen in 10-12 days or corpus luteum degrades into corpus albicans and ceases secretion which 27.2 – The Uterine Tubes (Fallopian) › Path from ovary to uterus, not connected to ovary › Isthmus – narrow end connected to uterus › Infundibulum – wide distal end with fimbriae › Ampulla – middle section where fertilization often occurs › Cilia propel oocyte to the uterus and they beat stronger with greater estrogen concentration › Muscular contraction help move the oocyte 27.2 – Uterus and Cervix › Uterus – muscular organ to nourish growing embryo › Fundus – area superior to uterine tubes › Body of uterus – middle section › Cervix – inferior section that projects into the vagina, secretes mucus that assists sperm movement › Uterus is held in place by ligaments and is made of 3 layers (perimetrium, myometrium, endometrium) › The stratum functionalis is the layer of the endometrium that is shed during menstruation 27.2 - continued › Corpus luteum keeps stratum functionalis healthy for implantation › Without progesterone due to lack of implantation blood vessels constrict and rupture so O2 can’t reach endometrial tissue › Menses – dead endometrial tissue and blood are shed › Menarche – the first menses after puberty 27.2 – The Menstrual Cycle › Uterine lining is shed, rebuilds, and prepares for implantation, 3 phases › Timing starts with first day of menses, day 1 of period › Menses phase – lining is shed, lasts about 5 days, hormone levels are low › Proliferative phase – endometrium rebuilds, hormone levels are rising › Secretory phase – started by progesterone from corpus luteum, has body ready for implantation, if hormone levels fall then tissues die resulting in menses 27.2 – The Breasts › Accessory organs that supply milk to infant, lactation › Mammary glands produce milk and it exits from the nipple › Areolar glands surround nipple and secrete lubricating fluid to prevent chaffing › Breasts are supported by suspensory ligaments › Changing hormone levels lead to swelling and tenderness › During pregnancy, mammary tissue develops and breasts enlarge 27.2 – Hormonal Birth Control › Manipulate negative feedback system › They provide constant hormones to prevent FSH and LH production › Endometrial wall will not get as thick › New birth control pills may result in no menses › Missing the wrong day or 2 can lead to ovulation 27.3 – Development of Male and Female › Without chemical prompting, all eggs are female › In embryos the same cells can be male or female, that is known as bipotential › The SRY gene (23rd chromosome) must prompt male development and cause testosterone secretion › Mullerian duct – in females, forms the uterus, uterine tubes, and part of the vagina › Wolffian duct – in males, forms epididymis, ductus deferens, and seminal vesicles 27.3 – The Plague… I mean Puberty › Puberty – stage of sexual maturity, increase in hormone release from hypothalamus, anterior pituitary, and the gonads › LH production increase around age 8 or 9, years before physical changes › Hypothalamus down regulates and gonads up regulate › Amount of body fat is correlated with age of puberty 27.3 – Signs of Puberty › Males – increased larynx size, deeper voice, increased muscular development, and hair growth › Females – fat deposited into breasts and hips, breasts develop, pelvis broadens, and hair growth › Males normally have a later growth spurt (11 -13) and can grow 4 inches per year, development may continue into early 20’s › Females grow earlier (9 – 11) and can grow 3 inches per year for 2 years or more