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REPRODUCTIVE SYSTEM (CONTROL OF GONADAL AND GAMETE DEVELOPMENT (OVARIAN…

- - - - FEMALE REPRODUCTIVE SYSTEM
        
        The developing gonad is ovary; the Mullerian duct develops into oviduct, uterus, cervix and vagina. Wolffian duct regresses. The absence of testosterone is important.
        
        The sex cords contribute cells known as follicle cells(initially) and granulosa cells(subsequently) which then surround the oocyte.
        
        The mesenchyme of the genital ridge contributes cell to become theca. The entire structure is called a follicle.
      - MALE REPRODUCTIVE SYSTEM
        
        The developing gonad is testis; rete testis produces Mullerian-inhibiting factor to cause regression of Mullerian duct. The Wolffian duct maintained by androgens produce by testis.
        
        Enzyme 5α-reductase is important for the effect of androgens for testosterone to be converted intracellularly into dihydrotestosterone for masculanization of tissues
        
        The exposure of hypothalamus to androgens at about time of birth causes the hypothalamus to be organized as male
  - - - HYPOTHALAMUS
        
        Nuclei (clusters of neurons) secrete peptide hormones for controlling pituitary activity.
        
        Regulates appetite temperature
        
        Integrates activity of autonomic nervous system
      - ADENOHYPOPHYSIS (PARS DISTALIS)
        
        Produces protein hormones for the control of reproduction
        
        Gonadotropin
        
        Follicle-stimulating hormone (FSH)
        
        plays a dominant role during growth of follicles
        
        Luteinizing hormone (LH)
        
        plays a dominant role during the final stage of follicles maturation during ovulation
        
        Prolactin
        
        Growth hormone (GH)
        
        Corticotropin (adrenocorticotropic hormone, ACTH)
        
        Thyroid-stimulating hormone (TSH)
  - - - GnRH is administered in a continuous manner (can be downregulated)
        
        PULSE GENERATOR SYSTEM FOR RELEASE OF GONADOTROPINS: Increased in the follicular phase and decreased in luteal phase of the estrous cycle
        
        Estrogen: decreases the pulse amplitude
        
        Progesterone: decreases the pulse frequency of gonadotropin secretion
        
        The hypothalamus and adenohypophysis
        
        respond to a sustained increase in estrogen secretion during final antral follicle development causes increase secretion of gonadotropins
        
        by increasing the frequency of pulsatile release of GnRH
        
        Surge of gonadotropin secretion is to induce changes within the follicle that lead to its rupture (ovulation)
  - - - accompanied by intense synthetic activity
        
        a large amount of RNA is synthsized
        
        follicle cells divide to form granulosa that is several cells thick
        
        granulosa cells secrete zona pellucida surrounding the oocyte
        
        the thecal layer of the follicle forms around the membrane propria is to complete the layers of follicle
        
        Primary follicle is formed
    - - FSH and LH receptors develop respectively on granulosa and theca
        
        appearance of fluid that begins to divide granulosa
        
        Antrum formed from fusion of follicular fluid within granulosa
        
        the oocyte remains surrounded by a layer of granulosa cells (cumulus oophorus) attaches to the wall of the follicle by a small stalk of granulosa cells
        
        the theca produces androgens under the influence of LH which diffuses across membrane propria into granulosa where androgens transformed into estrogens.
        
        Late of antral follicle development, FSH and estrogens initiate the formation of LH receptors on granulosa whereas FSH receptors begin to diminish
- - - - cow and doe have specialized area for storing milk which is cistern
- - - - Ducts sytem:under the control of estrogens, growth hormone and adrenal steroids
      - Alveoli: under the control of progesterone and prolactin
- - - - the release of oxytocin occurs within seconds after the stimulus arrive in hypothalamus
        
        increased pressure within the mammary gland
        
        Milk is forced out of alveoli and ducts due to contraction of myoepithelial cells
- - - - scrotum: skin pouch with a subcutaneous fibroelastic and muscular which provides a countercurrent heat exchange mechanism for testicular thermoregulation
      - testis: responsible for steroidogenesis (production of androgens) and spermatogenesis
        
        Interstitial tissue compartment
        
        Leydig cells
        
        seminiferous tubule
        
        Sertoli cells:provide support and nourishment to the developing germ cells
        
        basal compartment
        
        contains spermatogonia
        
        adluminal compartment
        
        represents a special environment for spermatocytes undergo meiosis and continue meiotic divisions
      - Epididymis: conduit spermatozoa and provides a special environment in which spertazoa are concentrated, undergo maturation and acquire fertilizing capacity
      - deferens ducts:transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation.
      - penis: copulatory organ
- - - - i. Mitotic division of type A spermatogonia to maintain population of stem cells
        
        ii. Type A spermatogonia becomes type B
        
        iii. Further mitosis to produce primary spermatocytes
        
        iv. Primary spermatocytes enter the pool of meiotically dividing cells and ultimately produce spermatozoa
    - - i. homologous chromosomes segregate into two resulting cells, creating a haploid condition.
        
        ii. The resultant haploid cells are the secondary spermatocytes with duplicated chromatids
    - - the newly formed spermatids continue to differentiate without dividing to form mature spermatids
- - - - Synthesize and secretes the decapeptide gonadotropin-releasing hormone (GnRH)
        
        GnRH acts directly on gonadotropic cells in the anterior pituitary
- - - - POSITIVELY AFFECTED BY INCREASING PHOTOPERIOD FOR CAT AND HORSE
      - POSITIVELY AFFECTED BY DECREASING PHOTOPERIOD FOR GOAT AND SHEEP
- - - - Before puberty: GnRH and gonadotropin are kept in check because the hypothalamus is highly sensitive to negative-feedback inhibition by estrogens
      - the onset of puberty results in the establishment of cyclical ovarian activity within a relatively short period
  - - - Menopause results from depletion of oocytes which has occured throughout the reproductive life an individual
        
        involves cyclical irregularity caused by failure of follicle development and ovulation
- - - - period of follicle development (occuring after luteal regression and end at estrus)
    - - period of sexual receptivity
    - - period of initial development of corpus luteum
    - - period of mature phase of corpus luteum
- - - - the oocyte and granulosa are kept under control by the production of inhibitory substances
        
        Oocyte-inhibiting factor prevents oocyte from resuming meiosis
        
        Luteinizing-inhibiting factor prevents granulosa from prematurely being changed into luteal tissue
        
        The impact of LH surge blocks the production of these two factors.
        
        the surge of LH on granulosa is to allow initiation of the process luteinization (transform cells from estrogen to progesterone secretion)
        
        the preovulatory surge of LH is to cause granulosa to produce substances (relaxin and prostaglandin) that affect continuity of the connective tissue of the thecal layers of the follicle
- - - - Follicular phase
        
        Ovulation
        
        Luteal phase
- - - - the embryo produces substances that modify uterine production of uterine prostaglandin F2α (PGF2α)
        
        estrogen synthesis by embryo is the way endometrium may be informed regarding the presence of embryo
  - - - in primates, this function is established early in gestation
        
        maintain pregnancy within 2-3 weeks of implantation
      - Hormone that synergize with progesterone for the support of pregnancy is relaxin
- - - - Cervix opens and fetus passed into pelvic canal
        
        Abdominal press becomes the main force involved in the delivery process
    - - Third stage of parturition: the delivery of the fetal membranes