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Pregnancy and Parturition (Pregnancy (Fertilization (Components…

- - - - Spermatozoa
        
        Stored in epididymis, change from oxidative to glycolytic metabolism, metabolize fructose within repro tract
        
        Adaptation of female reproductive tract for spermatozoa
        
        Movement through cervix aided by thinning of cervical mucus induced by oestrogen
        
        Develop special reservoirs for survival of sperm during transport, such as cervix and oviduct. Sperms are stored here and released continually until fertilization occur after arrival of oocyte within oviduct
        
        Capacitation of sperm
        
        To prepare spermatozoa for successful fertilization
        
        removing the glycoprotein from the sperm cell surface
        
        Allows sperm to undergo acrosomal reaction
        
        allow penetration of sperm through granulosa and zona pellucida to oocytes plasma membrane
        
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        allow it to fuse with oocyte
        
        Causes sperms tail to drive sperm forward
        
        Insemination
        
        Because of time taken for capacitation, insemination is best before ovulation occurs
        
        Female are in heat 24 hours before ovulation, ready to receive sperm just in time before ovulation for maximal fertility in natural conception
      - Ooctyes
        
        Must undergo first meiotic division before fertilization
        
        In some species, oocyte have not completed their first meiotic division after ovulation, sperm need to wait before fertilizing eg. horse and dog
    - - Develops to morula within 4-5 days within oviduct before moving to uterus
        
        allows uterus to finish its inflammatory activity from removal of sperms
        
        Allows endometrial gland to secrete nutrients
  - - - Embryo release substance that suppress uterine synthesis of PGF2a (cause regression of CL)
      - Oestrogen synthesis by the embryo informs the endometrium regarding the presence of embryo
      - Trophoblastin , of immunological importance, allows embryo to not be recognized as foreign object (probably)
      - Movement of embryo within the tract allow for pregnancy recognition
    - - Modification of synthesis (reduce synthesis)
      - Change secretion from pulsatile to continuous, absence of pulsatile secretion of PGF2a helps in maintenance of CL
  - - - Interstitial implantation or Discoid placentation
        
        Trophoblast have intimate connection with interstitium of endometrium
        
        Chorionic gonadotrophin (CG) released from syncitiotrophoblast
        
        CG helps maintain corpus luteum
        
        Occurs in primate
      - Eccentric implantation/Zonary placentation
        
        In dog and cats
      - Implantation within caruncles/Cotyledonary placentation
        
        In ruminants
      - Minor villus implantation/Diffuse placentation
        
        In horse and pig
    - - Provide nutrients and oxygen to fetus
      - As endocrine organ
        
        Oestrogen
        
        In primate, produced through interaction of fetus and placenta as the placenta alone can't synthesize oestrogen
        
        1) placenta produce pregnolone
        
        2) Fetal zone of adrenal cortex transforms pregnolone into c-19 androgen
        
        3) c-19 androgen returned back to placenta and converted into oestrogen
        
        Other animal, occurs late, progesterone is metabolized into oestrogen via placental enzyme
        
        Progesterone
        
        Relaxin
        
        Prepares pelvic canal for passage of birth
        
        equine chorionic gonadotrophin (eCG)
        
        produced by trophoblast, enhance production of progesterone by CL and aids formation of secondary corpus luteum from preformed follicles
        
        Placental lactogen
        
        In primates, is produced when CG is depleting
        
        has somatotrophic and lactogenic effects. for eg. in dairy cattle allow mammary gland alveolar development
        
        Prolactin
        
        Luteotrophic (maintain CL) in dogs
- - - - Released from uterus
      - affect the myometrium by releasing intracellular Ca2+ which bind to actin and myosin to initiate contraction
      - relaxation of the cervix
        
        affect aggregation of collagen fibres
      - Initiation of CL regression
        
        as progesterone suppresses myometrial activity, so PG lifts that suppression
        
        24-36 hours before delivery
    - - Hypothalamus induced adenohypophysis to secrete ACTH that induce fetal adrenal cortex (that has become more mature and became more responsive to ACTH) to release cortisol that shift synthesis from progesterone to oestrogen which increases availability of PGF2a precursor (arachidonic acid) to synthesize PGF2a
    - - Causes formation of oxytocin receptors in myometrium
    - - Released through Ferguson reflex, +ve feedback neuroendocrine reflex where afferent impulse (fetal distending the cervix) reach hypothalamus to release oxytocin via neurohypophysis causing uterine contraction which causes more oxytocin to be released
      - synergistic with PGF2a in uterine contration
    - - Causes ligament and associated muscles surrounding pelvic canals to relax, allowing fetus accomodate
  - - - Presentation of fetus at the internal os of cervix
        
        Initially, myometrial contraction helps push fetus to pelvic canal
        
        Then, abdominal press became the main force (closed epiglottis and increased abdominal force)
    - - Actual delivery
    - - Placenta delivery
        
        Litter bearing animals have immediate placental delivery
        
        Single bearing, placenta may be delivered immediately or within several hours
        
        aided by sustained surge of PGF2a postpartum which also helps reduce uterine size via myometrial contraction