3 Male Reproductive System The male gonads (testes) produce sperm and lie within the scrotumSperm are delivered to the exterior through a system of ducts: epididymis ductus deferens ejaculatory duct urethraAccessory sex glands:Empty their secretions into the ducts during ejaculationInclude the seminal vesicles, prostate gland, and bulbourethral glands
5 The ScrotumSac of skin and superficial fascia that hangs outside the abdominopelvic cavity containing paired testicles.Spermatic Cord: enclose nerves and blood vesselsThe Testes are kept 3C lower than core body temperature (needed for sperm production) controlled by:Cremaster muscleWhen it is cold it contracts pulling the testes up toward the core of the body.When it is warm these muscles relax allowing the testes to descend away from the body.
7 Seminiferous Tubules Produce the sperm Surrounding the seminiferous tubules are interstitial cells that produce Testosterone
8 The EpididymisSperm enter the epididymis were excess testicular fluid is absorbed and nutrients are provided to the sperm to enable them become motileUpon ejaculation the epididymis contracts, expelling sperm into the ductus (VAS) deferens.
9 Spermatids to Sperm Sperm have three major regions Head – contains DNA and has a helmet like acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the eggMidpiece – contains mitochondria spiraled around the tail filamentsTail – a typical flagellum produced by a centriole
11 Male Sexual ResponseErection: Mediated by parasympathetic nervous system during sexual stimulation. Penile arteries dilate which causes the erectile tissue corpora cavernosa to compress the penile veins draining the penis. Ejaculation: Mediated by the sympathetic nervous system. Muscles of the pelvic floor and accessory glands(seminal vesicles, prostate gland, bulbourethral glands) contract secreting the contents out the urethra as semen.
12 Ductus Deferens and Seminal Vesicles Ductus Deferens : runs from the epididymis to its an enlarged section (ampulla) where it merges with the seminal vesicleSperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra during ejaculationVasectomy – cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth controlSeminal vesicle lies on the posterior wall of the bladder. They functions to:and secrete 60% of the volume of semenSemen – viscous alkaline fluid containing:fructose: fuel for the road tripprostaglandins which stimulate reverse peristalsis in the uterusascorbic acid
13 Accessory Glands Prostate Gland Doughnut-shaped gland that encircles part of the urethra inferior to the bladderPlays a major role in the activation of spermaccounts for one-third of the semen volumeIts milky, slightly acid fluid, which contains citrate, enzymes, and prostate-specific antigen (PSA),Acts as a anticoagulant for sperm. Elevated blood levels suggest damage to the prostate which allows PSA to enter the blood. The following are associated with elevated levels:Prostate cancer, prostatitis and BPHBulbourethral Glands (Cowper’s Glands)Pea-sized glands inferior to the prostateProduce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra
14 Hormonal Regulation of Testicular Function The hypothalamus releases gonadotropin-releasing hormone (GnRH)GnRH stimulates the anterior pituitary to secrete FSH and LHFSH causes sustentacular cells ( Nurse) to release androgen-binding protein (ABP) and inhibin.LH stimulates interstitial cells to release testosteroneTestosteroneABP binding of testosterone enhances spermatogenesissecondary sex characteristics.
16 Additional Effects of Testosterone Prostate – converts Testosterone into dihydrotestosterone (DHT) before it can bind within the nucleus.High levels of DHT may increase prostate size and cause male pattern baldness.Symptoms of testosterone deficiency:Increased risk of insulin resistance and DM:Increased visceral obesity: increases activity of the enzyme aromatase which can convert testosterone into estrogen .gynecomastia : female breast development in malesXenoestrogens : compounds found in pesticides, plastic bottles (Bisphenol A) also increase estrogen levelsDecreased muscle mass and bone strengthSleep apneaLow Libido
17 Female Reproductive Anatomy Ovaries are the primary female reproductive organsMake female gametes (ova)Secrete female sex hormones (estrogen and progesterone)Accessory ducts include uterine tubes, uterus, and vaginaInternal genitalia – ovaries and the internal ductsExternal genitalia – external sex organs
19 External Genitalia: Vulva Perineum- space between vagina and anusLies external to the vagina and includes the mons pubis, labia, clitorisMons pubis – round, fatty area overlying the pubic symphysisLabia majora – elongated, hair-covered, fatty skin folds covering the labia minoraLabia minora – hair-free skin folds covers the urethral and vaginal openingsClitoris (erectile tissue)Primary center for sexual stimulation
20 Vagina Thin-walled tube lying between the bladder and the rectum. Extending from the cervix to the exterior of the body.Provides a passageway for birth, menstrual flow, and is the organ for sexual intercourse.
21 UterusHollow, thick-walled organ located in the pelvis anterior to the rectum and posterosuperior to the bladderBody – major portion of the uterusFundus – rounded region superior to the entrance of the uterine tubesCervix- distal tip contacts the vagina.
22 Fallopian TubesReceive the ovulated oocyte and provide a site for fertilization at the distal quarter of the tube.Expand distally around the ovary forming the ampullaThe ampulla ends in the funnel-shaped, ciliated infundibulum containing fingerlike projections called fimbriae.
23 Uterine Wall Uterine Wall is composed of three layers Perimetrium – outermost serous layer; the visceral peritoneumMyometrium – middle layer; interlacing layers of smooth muscleEndometrium – mucosal lining of the uterine cavity changes in thickness during the menstrual cycle
24 OvariesPaired organs that function as both endocrine and reproductive organs .Located within the pelvic cavity on either side of the uterusEach ovary contains primordial follicles consisting of an oocyte and follicular cells.The ovary is stimulated by pituitary secretions of FSH and LH. These hormones collectively stimulate the growth and maturation of the oocyte within the follicle.The mature follicle secretes estrogenEstrogen-induced secondary sex characteristics include:Increased deposition of subcutaneous fat, especially in the hips and breastsWidening and lightening of the pelvisGrowth of axillary and pubic hair
26 Hormones and Ovarian Development Follicular phase – period of follicle growth (days 1–14)Day 1 – GnRH stimulates the release of FSH and LHFSH stimulates mitosis of the primordial follicle into a primary follicle.LH stimulates estrogen secretion promoting the growth of the endometrium and development of the fluid filled antrum characteristic in a mature graafian follicle.
27 Luteal phase of the Ovarian Cycle Luteal phase – period of corpus luteum activity (days 14–28)(Ovulation ) at Day14 a large surge in LH triggers causes follicle to the rupture ejecting the ovum into the fallopian tubeLH transforms the ruptured follicle into a corpus luteum which produces several hormones:Inhibin: inhibits further production FSH and LHprogesterone and estrogen which maintain endometrium
28 Luteal phase of the Ovarian Cycle Human chorionic gonadotropin (hCG) stimulates the continuous secretion of LH preventing the degeneration of the corpus luteum.If pregnancy does occur, the corpus luteum will continue to produce these hormones until the placenta takes over at about 3 months.If pregnancy does not occur, the corpus luteum degenerates in 10 days, leaving a white scar (corpus albicans)
29 EndometriumHas numerous uterine glands that change in length as the endometrial thickness changesUterine glands supply fertilized egg with nourishmentglycogen-rich uterine fluid.Will increase in size during the first half of the menstrual cycle.Reduction in estrogen levels cause the endometrium to shed
30 Acrosomal Reaction and Sperm Penetration An ovulated oocyte is encapsulated by:The corona radiata and zona pellucidaExtracellular matrixSperm binds to the zona pellucida and undergoes the acrosomal reactionEnzymes are released near the oocyteHundreds of acrosomes release their enzymes (hyaluronidase) to digest the zona pellucidaOnce a sperm makes contact with the oocyte’s membrane:A calcium mediated reaction blocks other sperm from entering
32 From Zygote to Blastocyst Degenerating zona pellucidaInner cell massBlastocyst cavityBlastocyst cavityTrophoblast(a) Zygote (fertilized egg)(b) 4-cell stage 2 days(c) Morula 3 days(d) Early blastocyst 4 days(e) Implanting blastocyst 6 daysFertilization (sperm meets egg)(a)(b)(c)Uterine tubeOvaryOocyte (egg)(d)Ovulation(e)UterusEndometriumCavity of uterus
33 From Zygote to Blastocyst Fertilization occurs between the sperm and ovum in the distal ¼ segment of the fallopian tube.Cleavage – a series of mitotic divisions occur for 3 days after fertilization forming a morula stage (solid ball of cells)Zona pellucida disintegrates to release a fluid-filled hollow sphere called a Blastocystouter cells (trophoblast) helps to form placentainner cell mass develops into embryoEctoderm – forms structures of the nervous system and skin epidermis.Endoderm – forms epithelial linings of the digestive, respiratory, and urogenital systems.Mesoderm – forms muscles and various connective tissuesImplantation of Blastocyst occurs around day 6.
34 The Female BreastModified sweat glands consisting of lobes that radiate around and open at the nippleAreola – pigmented skin surrounding the nippleSuspensory ligaments attach the breast to underlying muscle fasciaLobes contain glandular alveoli that produce milk in lactating womenCompound alveolar glands pass milk to lactiferous ducts, which open to the outsideFigure 27.17
35 LactationDuring pregnancy estrogen and progesterone high levels stimulate the hypothalamus to secrete prolactin-releasing hormone (PRH) which targets the anterior pituitary. This results in the secretion of prolactinProlactin stimulates the production of milk in the breasts
36 Lactation Suckling stimulates both prolactin and oxytocin : Prolactin secretion allows for continuous milk productionOxytocin secretion causes the smooth muscle around the alveolar ducts in the breast to eject the milk for the nipple
37 Chromosomes and Heredity Heredity = transmission of genetic characteristics from parent to offspringkaryotype = chart of chromosomes at metaphaseThe body cells have 23 pairs homologous for a total of 46 chromosomes 2n (diploid number of chromosomes) 22 of the 23 pairs guide genetic expression of most other traits. (autosomes)Sex cells (gametes) from the ova and the sperm each has 1 chromosome that determine the sexSperm and egg contain only 23 chromosomes n ( haploid)fertilized egg has diploid number of chromosomes