Chapter 48, (page 936-) Reproductive system Csaba Bödör,

Regulation of the reproduction Pituitary gland: Gonadotropic hormones: FSH and LH Hypothalamus: GnRH (Gonadotropic release hormone) Stimulate gonads: testes and ovaries (growth and function) hormones and gametes ovum and sperms estrogen and testosterone progesterone

Reproduction ASEXUAL REPRODUCTION: Budding, fragmentation, binary fission (recall: bacteria) Parthenogenesis: an unfertilized egg develops into an adult Parents and offspring genetically identical, no gametes, successful in stable environment, energy efficient SEXUAL REPRODUCTION: offspring formed by fusion of two gametes (ovum, sperm) a fertilized egg is formed (zygote) Parents and offspring genetically different, provides genetic variety, successful in unstable environment

External fertilization Mating partners typically release eggs into the water simultaneously Internal fertilization Male delivers sperm into the female’s body Hermaphroditism Single individual produces both eggs and sperm Fertilization

Spermatogenesis spermatogonia Mitosis primary spermatocytes Meiosis secondary spermatocytes spermatids mature sperms

Spermatogenesis Testes, seminiferous tubules Stored: epididymis, vas deferens

Spermatogenesis Interstitial cells: testosteron Sertoli cells > tight junctions (ch5) Blood-testis barrier Signaling molecules, nourishing fluid

Structure of a mature sperm Acrosome contains an enzyme which helps to penetrate the egg cell

Endocrine regulation of reproduction – male Testosterone establishes and maintains Primary sex characteristics Secondary sex characteristics Endocrine regulation of reproduction involves: –Hypothalamus (GnRH) –Pituitary gland (FSH and LH) –Testes (Testosterone, ABP and inhibin)

Principal male reproductive hormones !!!

Regulation of reproduction in the male

Human female reproductive system Ovaries : hormones gametes Fertilization: in the oviducts Uterus Incubator for the embryo Cervix extends into the vagina Epithelial lining of the uterus **

Oogenesis Development of a human ovum Primary oocyte (2n) Meiosis I. polar body (n) + secondary oocyte (n) 2 polar bodies (n) polar body (n) + ovum (n) Oogonium * (2n) Primary oocyte and granulosa cells make up a follicle Meiosis II.

Development of follicles in the ovary As the follicle grows: Connective tissue cells form a layer of theca cells Primary oocyte undergoes meiosis > secondary oocyte and a polar body The secondary oocyte is ejected and enters an oviduct to be fertilized The part of the remaining follicle develops into a corpus luteum (temporary endocrine gland) ** progesteron glycoproteins

The menstrual cycle 28 days, 0-5 days: menstruation 14 th day: ovulation, pre- and post ovulatory phases Preovulatory phase (follicular phase) GnRH stimulates the pituitary to secrete FSH and LH FSH stimulates few follicles to begin to develop, and estrogen production of granulosa cells (part of follicles) estrogen acts as a hormone + autocrine and paracrine regulator as well (further increase in estrogen) LH stimulates theca cells (androgen production), androgens are converted to estrogen in granulosa cells Estrogen stimulates endometrium development (thickens, new vessels) LH stimulates final maturation of the follicle and ovulation (LH surge)

The menstrual cycle Postovulatory phase (luteal phase) LH promotes the development of corpus luteum corpus luteum secretes progesteron, estrogen (and inhibin) Progesterone: stimulates glands of the endometrium > fluid, nutrients Progesterone and estrogen inhibit GnRH, FSH, LH secretion so no new follicles develop If fertilization does not occur, the corpus luteum degenerates (8 d), hormone levels fall, and menstruation occurs low progesteron and estrogen >>> >>> no inhibition of LH, FSH >>> >>> new follicles start to develop

Feedback mechanisms in endocrine regulation of female reproduction

Principal female reproductive hormones

Conception Fertilization and the subsequent establishment of the pregnancy

Events following fertilization Human chorionic gonadotropin (hCG) >>> corpus luteum 32 cells 7th day after fertilization

Human fertilization –Fusion of secondary oocyte and sperm to form a zygote –Embryo implants in the uterus –hCG is the hormone that maintains the corpus luteum –Estrogen and progesterone Secreted by corpus luteum (first trimester) and then by placenta (membranes + uterine tissue) Human birth process –Several hormones, including estrogen, oxytocin, and prostaglandins regulate parturition –Labor (series of involuntary contractions of the uterus) Divided into three stages The baby is delivered during the second stage

Contraception –Hormonal methods, such as oral contraceptives –Intrauterine devices –Condoms and contraceptive diaphragms –Sterilization (vasectomy or tubal ligation) Scrotum, inguinal canals epydidymis, vas deferens, ejaculatory duct, urethra, release Accessory glands: seminal vesicles, prostate gland, bulbourethral gland Penis: glans, prepuce, erectile tissue, cavernous bodies, spongy body, erection

Female reproductive system Breasts Function in lactation Prolactin stimulates milk production Oxytocin stimulates milk ejection from the alveoli into the ducts

Sterilization