Presentation on theme: "The Reproductive System. Male Reproductive System."— Presentation transcript:
The Reproductive System
Male Reproductive System
The male gonads (testes) produce sperm and lie within the scrotum Sperm are delivered to the exterior through a system of ducts: epididymis ductus deferens ejaculatory duct urethra Accessory sex glands: –Empty their secretions into the ducts during ejaculation –Include the seminal vesicles, prostate gland, and bulbourethral glands
The Scrotum Figure 27.2
The Scrotum Sac of skin and superficial fascia that hangs outside the abdominopelvic cavity containing paired testicles. Spermatic Cord: enclose nerves and blood vessels The Testes are kept 3 C lower than core body temperature (needed for sperm production) controlled by: Cremaster muscle –When 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.
Seminiferous Tubules –Produce the sperm –Surrounding the seminiferous tubules are interstitial cells that produce Testosterone
The Epididymis –Sperm enter the epididymis were excess testicular fluid is absorbed and nutrients are provided to the sperm to enable them become motile –Upon ejaculation the epididymis contracts, expelling sperm into the ductus (VAS) deferens.
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 egg –Midpiece – contains mitochondria spiraled around the tail filaments –Tail – a typical flagellum produced by a centriole
Male Sexual Response Erection: 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.
Ductus Deferens and Seminal Vesicles Ductus Deferens : runs from the epididymis to its an enlarged section (ampulla) where it merges with the seminal vesicle Sperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra during ejaculation Vasectomy – cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control Seminal vesicle lies on the posterior wall of the bladder. They functions to: –and secrete 60% of the volume of semen –Semen – viscous alkaline fluid containing: fructose: fuel for the road trip prostaglandins which stimulate reverse peristalsis in the uterus ascorbic acid
Accessory Glands Prostate Gland –Doughnut-shaped gland that encircles part of the urethra inferior to the bladder –Plays a major role in the activation of sperm –accounts for one-third of the semen volume –Its 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 BPH Bulbourethral Glands (Cowper’s Glands) –Pea-sized glands inferior to the prostate –Produce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra
Hormonal Regulation of Testicular Function The hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to secrete FSH and LH –FSH causes sustentacular cells ( Nurse) to release androgen- binding protein (ABP) and inhibin. –LH stimulates interstitial cells to release testosterone Testosterone –ABP binding of testosterone enhances spermatogenesis – secondary sex characteristics.
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 males Xenoestrogens : compounds found in pesticides, plastic bottles (Bisphenol A) also increase estrogen levels Decreased muscle mass and bone strength Sleep apnea Low Libido
Female Reproductive Anatomy Ovaries are the primary female reproductive organs –Make female gametes (ova) –Secrete female sex hormones (estrogen and progesterone) Accessory ducts include uterine tubes, uterus, and vagina Internal genitalia – ovaries and the internal ducts External genitalia – external sex organs
Female Reproductive Anatomy
External Genitalia: Vulva Perineum- space between vagina and anus Lies external to the vagina and includes the mons pubis, labia, clitoris –Mons pubis – round, fatty area overlying the pubic symphysis –Labia majora – elongated, hair- covered, fatty skin folds covering the labia minora –Labia minora – hair-free skin folds covers the urethral and vaginal openings – Clitoris (erectile tissue) Primary center for sexual stimulation
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.
Uterus Hollow, thick-walled organ located in the pelvis anterior to the rectum and posterosuperior to the bladder Body – major portion of the uterus Fundus – rounded region superior to the entrance of the uterine tubes Cervix- distal tip contacts the vagina.
Fallopian Tubes Receive the ovulated oocyte and provide a site for fertilization at the distal quarter of the tube. Expand distally around the ovary forming the ampulla The ampulla ends in the funnel-shaped, ciliated infundibulum containing fingerlike projections called fimbriae.
Uterine Wall Uterine Wall is composed of three layers –Perimetrium – outermost serous layer; the visceral peritoneum –Myometrium – middle layer; interlacing layers of smooth muscle –Endometrium – mucosal lining of the uterine cavity changes in thickness during the menstrual cycle
Ovaries Paired organs that function as both endocrine and reproductive organs. Located within the pelvic cavity on either side of the uterus Each 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 estrogen Estrogen-induced secondary sex characteristics include: –Increased deposition of subcutaneous fat, especially in the hips and breasts –Widening and lightening of the pelvis –Growth of axillary and pubic hair
Hormones and Ovarian Development Follicular phase – period of follicle growth (days 1–14) Day 1 – GnRH stimulates the release of FSH and LH –FSH 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.
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 tube LH transforms the ruptured follicle into a corpus luteum which produces several hormones: Inhibin: inhibits further production FSH and LH progesterone and estrogen which maintain endometrium
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)
Endometrium Has numerous uterine glands that change in length as the endometrial thickness changes Uterine glands supply fertilized egg with nourishment –glycogen-rich uterine fluid. Will increase in size during the first half of the menstrual cycle. Reduction in estrogen levels cause the endometrium to shed
Acrosomal Reaction and Sperm Penetration An ovulated oocyte is encapsulated by: –The corona radiata and zona pellucida –Extracellular matrix Sperm binds to the zona pellucida and undergoes the acrosomal reaction –Enzymes are released near the oocyte –Hundreds of acrosomes release their enzymes (hyaluronidase) to digest the zona pellucida Once a sperm makes contact with the oocyte’s membrane: A calcium mediated reaction blocks other sperm from entering
Acrosomal Reaction and Sperm Penetration
(a) Zygote (fertilized egg) (b) 4-cell stage 2 days (c) Morula 3 days (e) Implanting blastocyst 6 days (d) Early blastocyst 4 days (e) (d) Fertilization (sperm meets egg) Uterine tube Oocyte (egg) (a) Ovulation Ovary (b) (c) Uterus Endometrium Cavity of uterus From Zygote to Blastocyst Degenerating zona pellucida Blastocyst cavity Inner cell mass Blastocyst cavity Trophoblast
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 Blastocyst –outer cells (trophoblast) helps to form placenta –inner cell mass develops into embryo Ectoderm – 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 tissues Implantation of Blastocyst occurs around day 6.
The Female Breast Modified sweat glands consisting of lobes that radiate around and open at the nipple Areola – pigmented skin surrounding the nipple Suspensory ligaments attach the breast to underlying muscle fascia Lobes contain glandular alveoli that produce milk in lactating women Compound alveolar glands pass milk to lactiferous ducts, which open to the outside Figure 27.17
Lactation During 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 prolactin Prolactin stimulates the production of milk in the breasts
Lactation Suckling stimulates both prolactin and oxytocin : –Prolactin secretion allows for continuous milk production –Oxytocin secretion causes the smooth muscle around the alveolar ducts in the breast to eject the milk for the nipple
Chromosomes and Heredity Heredity = transmission of genetic characteristics from parent to offspring –karyotype = chart of chromosomes at metaphase The 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 sex Sperm and egg contain only 23 chromosomes n ( haploid) –fertilized egg has diploid number of chromosomes