Human Reproductive Systems Dr. Jason R. Mayberry Castle View High School

Organ Systems Reproductive Endocrine Nervous Muscular Skeletal Cardiovascular Digestive Respiratory Urinary Immune Integumentary

Gonads and Kidneys both form from mesoderm Urogenital Formation Gonads and Kidneys both form from mesoderm Gonad: organ that produces gametes (testicle or ovary) Kidney: organ that filters blood and produces urine. Gonads are “indifferent” at first and can become either testes or ovaries. Gamete producing cells are stored near the umbilical cord, and migrate into the gonads as they begin to form Urogenital Ridge Gonad Kidney

Primary Sexual Differentiation Different tubes connect the male and female gonad to the external world Precursor tubes to both the male (Vas Deferens) and female (Fallopian Tubes) tubes form in all embryos If the Y chromosome is present (specifically the SRY gene) The gonad becomes a testicle The female tubes degenerate If no Y chromosome (i.e. two X chromosomes) The gonad becomes an ovary The male tubes degenerate. Kidney “Indifferent” Gonad Male Tubes Ureter Female Tubes Male Female

External Genitalia Indifferent Genitalia Indifferent Genitalia: External Genitalia for male and female begin development identically (end of 8th week). If Testes form, testosterone will cause the male genitalia to form. Without testosterone, the genitalia form as a female. External genitalia can be distinguished in a sonogram by the end of the 3rd or 4th month Genital Tubercle Labioscrotal fold Urogenital Fold 6 Weeks Male Development 8 Weeks Female Development 10 Weeks 12 weeks

Descent of the Testicles Testicles descend from original location in the abdomen into the scrotum. Lower temperature in the scrotum is needed for sperm production.

Anatomy of the Male Reproductive System Ampulla of Vas Deferens: widening of Vas Deferens at distal end Accessory Glands: Produce nutrients, pH buffers, lubrication, and enzymes Seminal Vesicles Ejaculatory Duct: Transport of mature sperm to the urethra; paired Prostate Bulbourethra Urethra: Transport of mature sperm out of the penis (Prostatic, Membranous, and Penile); not paired Vas Deferens: Transport of mature sperm to the Ejaculatory duct in the Prostate (sometimes called the Ductus Deferens) Epididymis: Site for sperm maturation and storage Erectile Tissue: With arousal becomes engorges with blood causing an errection. Testicle: location for sperm development within seminiferous tubules (primary reproductive organ; all others are accessory); paired Penis: Delivers Semen to the Female Vagina Scrotum: 2-sided Pouch for the Testes (divided by septum)

Testicle and Sperm Production Vas Deferes Epididymis Leydig Cells: produce Testosterone Seminiferous Tubule: site for sperm production Immotile Sperm Spermatogonia: sperm stem cells Sertoli Cells: Protect and nurture the developing sperm

2n Spermatogonia Before Birth Spermatogonia divide by mitosis then become dormant until puberty Mitosis From Birth To Puberty 2n Mitosis 2n Spermatogonia 1o Spermatocyte 2n 2o Spermatocytes Spermatid 1n Mitosis Spermatogonia 2n 2n 1n Mitosis Spermatogonia 2n 2n 1n Mitosis Spermatogonia 2n 1n 2n

Endocrinology of Sperm Production A complex interaction of hormones is required for sperm formation Hormones produced in the Brain: Hypothalamus produces Gonadotrophic Releasing Hormone (GnRH) Pituitary produces Follicle Stimulating Hormone (FSH), and Leuitinizing Hormone (LH) Hormones produced in the Testicle Testosterone promotes sperm formation Testosterone also promotes male specific charactistics GnRH FSH and LH Testosterone Inhibin ABP ABP

Internal Anatomy of the Female Reproductive System Fallopian Tubes (also called Uterine Tubes or oviduct) Fimbriae Ampulla Ovary Ovarian Ligament Uterus Round Ligament Clitoris Vagina

External Female Genitalia Vulva: External Female Genitalia Clitoris Labia Majora Labia Minora Pubis Bone Urethra Opening Vagina Anus

Uterus and the Menstrual Cycle Fundus Perimetrium connective tissue that surrounds the outside Myometrium is a thick layer of muscle Endometrium Epithelial Layer lining the inside of the Uterus Stratum Basale Supported by “straight arteries” Permanent layer which gives rise to the Stratum Functionalis Stratum Functionalis Supported by spiral arteries Contains Uterine “milk” glands Menstrual Cycle: Strat. Functionalis is built up and Sloughed off in connection with the Ovarian Cycle Cervix: Opening to the Uterine Cavity External Os opens to Vagina Internal Os opens to Uterine Cavity Mucous Plug in the cervix helps to block infections from entering the Uterus or Peritoneal cavity. Fundus is the top of the Uterus Endometrium Internal Os Myometrium External Os Perimetrium Strat. Functionalis Endometrium Strat. Basalis Myometrium

Mammary Gland Development Adipose Tissue Suspensory Ligaments Areola Nipple Lactiferous Sinus Lactiferous Duct Lobe of Mammary Glands (25-50 per breast) produces milk Before pregnancy the glandular tissue is undeveloped and differences in breast size are due largely to adipose tissue Estrogen during pregnancy stimulate Prolactin release from the Anterior Pituitary (in the brain) Prolactin causes glandular tissue to develop and begin producing milk Progesterone contribute to breast development during pregnancy Oxytocin stimulates cells surrounding the glands to contract resulting in milk release.

Developing Primary Follicle structures within the ovary that contain the Oocyte producing cells. found at different stages of development. Ovulation: After puberty, one follicle matures each month and is released at. Maturing Follicles Graffian Follicle Corpus Albicans Corpus Luteum Ovulation Secondary Follicle Developing Primary Follicle Primary Oocyte: undergoes meiosis to produce an oocyte. Thecal Cells: produce Testosterone Granulosa Cells: convert Testosterone to Estrogen

Female Gametogenesis Meiosis Oogonia 2n Meiosis begins in a woman’s ovary before she is born. resumes in follicles as they develop after puberty Only completes IF fertilized. Mitosis Oogonia 2n Oogonia 2n Final Mitosis 2n 1o Oocyte 2n 1o Oocyte Meiosis Meiosis Begins Meiosis Begins 2n Prophase I of Meiosis 2n Prophase I of Meiosis Birth Ovulation If Fertilization DOES Occur 1n 2o Oocyte 1n 2o Oocyte Metaphase II If Fertilization Does Not Occur 2n Zygote Mitosis 2n 2n Embryo

Gametogenesis: Male Female Comparison Spermatogonia Mitosis 1o Spermatocyte 2o Spermatocytes Spermatids Birth and Puberty Oogonia Final Mitosis Meiosis 1o Oocyte 1o Oocyte Birth to Ovulation If Fertilization Occurs 2o Oocyte 2o Oocyte If Fertilization Does Not Occur Zygote

Cyclic Pituitary and Ovarian Hormone Interactions. GnRH FSH LH Low Estrogen Pro-gesterone Mod Estrogen High Estrogen 28 14 FSH Pituitary Hormones LH Progesterone threshold Estrogen Ovarian Hormones

Ovarian Cycle 7 14 28 Menstrual Phase Proliferative Phase GnRH FSH LH Mod Estrogen Low Estrogen High Estrogen Pro-gesterone Loss of Progesterone Causes spiral arteries to constrict Endometrial Layer degenerates and is sloughed off Estrogen Causes Endometrium to Thicken Causes Glands and Blood Supply develop Progesterone Maintains Endometrium Causes Glands to secrete “Uterine Milk” (nourishes embryo before placental develops) Increases blood flow 7 14 28 Menstrual Phase Proliferative Phase Secretory Phase

Ovarian Cycle FSH LH Progesterone Estrogen 7 14 28 Proliferative Phase GnRH FSH LH Mod Estrogen Low Estrogen High Estrogen Pro-gesterone 28 14 FSH Pituitary Hormones LH Progesterone threshold Estrogen Ovarian Hormones 7 14 28 Proliferative Phase Secretory Phase Menstrual Phase Estrogen Loss of Progesterone Progesterone

Hormonal Regulation of the Ovarian Cycle: Luteal Phase If a Pregnancy does NOT occur then the cycle of hormones continues indefinitely. If pregnancy DOES occur Developing placenta produces Human Chorionic Gonadotropin (HCG) HCG maintains Corpus Luteum for ~8 weeks After 8 weeks the Placenta takes over Estrogen and Progesterone production – maintaining the pregnancy Placental HCG Placental Progesterone and Estrogen 8 weeks