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Reproductive Physiology (The Mammary Gland (Anatomy aspects (Duct system…

- - - - Migrate into sex cords in genital ridge and populate it
        
        Primordial germ cell became the oocyte for both male and female
    - - Consists of:
        
        Mesenchyme
        
        Mesenchyme differentiate to become Leydig cells
        
        Mesenchyme became the theca cells
        
        Sex cords
        
        Formed at the cortical region of genital ridge
        
        Development in Male
        
        Sex cords became the seminiferous tubule, Sertolli cells
        
        Invaginate into the medulla
        
        Wolfian duct develop to become epididymis, vas deferens and part of urethra
        
        Development in Female
        
        Sex cords became the granulosa cells
        
        Mullerian duct became the oviduct, uterus, cervix, vagina
        
        End of mullerian duct differentiate to become fimbriae to receive ovum from the ovary
  - - - Produced by testis in male
      - Internal genitalia
        
        Converted from androgen by 5-a-reductase enzyme
        
        Maintain Wolfian (Mesonephros) duct
        
        Mesonephric tubule arising from Wolfian duct differentiate to become Rete Testis
        
        Rete testis contains Mullerian inhibiting factor, that prevent development of Mullerian duct
      - External genitalia
        
        Masculinization fom the penis and scrotum
      - Exert influence to hypothalamus at birth
        
        Masculinization
        
        Exposure to testosterone
        
        Aromatization (Conversion) of Androgen to Estrogen
    - - Internal genitalia
        
        Mullerian duct continue to develop
        
        Became the oviduct, uterus, cervix and 1/3 of vagina cranially
      - External genitalia
        
        Formation of labia (female counterpart of scrotum) that becomes the vulva
        
        clitoris (female counterpart of Glans penis)
  - - - Release hormones to control pituitary gland
        
        Via axons of neurons
        
        Via vascular portal system
        
        for eg. pulsatile release Gonadotrophin Releasing Hormone (GnRH)
        
        Affect the adenohypophysis
        
        pulsatile release of
    - - consists of three lobes
        
        Pars distalis (Adenohypophysis)
        
        Reproductive hormones
        
        (Gonadotrophin)
        
        LH
        
        FSH
        
        Prolactin
        
        Other hormones
        
        Growth hormone
        
        TSH
        
        Adrenocorticotrophic hormone (ACTH)
        
        Pars intermedia
        
        Pars Nervosa (Neurohypophysis)
        
        Paraventricular nuclei
        
        Oxytocin
        
        Supraoptic nuclei
        
        Antidiuretic hormone (Vasopressin)
  - - - Gonadotrophin
        
        FSH
        
        Follicular phase
        
        presence of estrogen
        
        decrease amplitude of gonadotrophin pulsatile release, frequency is increased due to absence of progesterone
        
        positive feedback, surge of estrogen
        
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        absence of progesterone
        
        LH
        
        Luteinizing phase
    - - Catecholamine dopamine, GABA, and GAP inhibit prolactin
- - - - May be chosen from dominant follicle that grow at the onset of corpus luteum regression. This is of because of low progesterone leads to higher frequency pulsatile release of Gonadotrophin, thus more FSH is produced
    - - LH surge causes ovulation by removing the inhibiting factors that prevent resumption of oocyte’s meiosis and luteinization of tissue. It also causes release of factors such as prostaglanding F2a that allows the disintegration of connective tissue at thecal layers that allow follicle to rupture and ovulation to occur
  - - - Corpus luteum secretes progesterone after luteinization that causes granulosa cells to secretes progesterone instead of estrogen. Luteinization occurs during the preovulatory LH surge and ovulation. Progesterone important for initiation and maintenance of pregnancy secreted usually within 24 hours after ovulation, some before ovulation during preovulartory LH surge. In rodents, prolactin substitute LH
    - - Caused by prostaglanding F2a secreted by the uterus 14 days postovulation. Uterus must be exposed to estrogen and progesterone to release prostaglandin, then prostaglandin inhibits production of progesterone, and cause uterus to secrete oxytocin, which binds to oxytocin receptors at uterus to release more prostaglandin
      - Prostaglandin must be released by pulse at 6 hours interval, 4 to 5 times in 24 hours for complete luteolysis
      - Mode of transfer by local countercurrent transfer (from high concentration uteroovarian vein to ovarian artery) or general systemic transfer
      - Release of prostaglandin stops once progesterone concentration reach base level
    - - Factors that affect lifespan of CL include
        
        Presence of embryo (blockage of prostaglandin synthesis)
        
        Absence of uterine infection in mares (mares predisposed to uterine infection?)
        
        Absence of uterine horn (lengthen luteal phase)
        
        Endometritis cause by bacterial contamination cause increased synthesis of PGF2a, causes premature luteolysis, and shorterning of estrous cycle
  - - - Induced ovulator
        
        copulation is required to induce ovulation though elevated oestrogen level is needed for animal to be sexually receptive
        
        In rodents, ovarian cycle is extended because of copulation due to the release of prolactin which lengthens the luteal phase even in the absence of pregnancy
      - Spontaneous ovulator
        
        spontaneous ovulatory ovulate due to surge of gn release induced by oestrogen, follicular phase and luteal phase differ in large domestic animals and high primates.
        
        In high primates, follicular phase and luteal phase is separated completely in high primates whereas in large domestic animals, follicle growth can occur even into the luteal phase. This causes the ovarian cycle to be shorter in large domestic animal due to shorter luteolysis to ovulation intervals
- - - - Stages of Estrual Cycle
        
        2) Estrus: Period of sexual receptivity
        
        1) Proestrus: period of follicle development, occur subsequent to luteal regression and end at estrus
        
        In dog, proestrus are delayed by anaestrus for 2 to 3 months
        
        In pig, proestrus does not occur for 5-6 days
        
        In domestic animals, proestrus begins within 48 hours after end of luteal phase
        
        3) Metestrus: period of initial development of corpus luteum
        
        4) Diestrus: period of mature phase of CL
      - Terms used depends on:
        
        Behavioural = sexually receptive or not including pro, met and di,
        
        Eg, in horse difficult to assess CL via rectal palpation, so are classified by sexual behaviour, estrus or nonestrus
        
        Gonadal if differentiation of follicles and CL is possible
        
        Ovarian status of dog and cat can be determined with vaginal cytology
        
        Follicular phase: proestrus and estrus, Luteal phase: metestrus and diestrus
    - - Primates are receptive throughout reproductive cycle so menstrual cycle term is used with menstruation as the start of the cycle
  - - - Loose
        
        First onset of sexual activity/menstrual
      - Technical
        
        first ovulation
    - - Size
      - Age
    - - Maturation of Hypothalamus
        
        Before puberty, GnRH and Gn are kept in check by negative feedback inhibition of estrogen towards the hypothalamus (highly sensitive to negative feedback of estrogen)
        
        Upon maturation of hypothalamus, sensitivity to negative feedback inhibition of estrogen is reduced
      - After the cessation to the exposure to long photoperiod
        
        Long photoexposure allows hypothalamus to mature and decrease sensitivity towards -ve inhibition of estrogen
        
        Photoperiod can have suppressive effect on the timing of puberty in different animals
    - - o Follicles develop due to surge of gonadotrophin
        
        o Hypothalamus has less sensitivity to -ve inhibition of estrogen produced by growing follicles
        
        o Preovulatory surge of Gn induced by oestrogen cause production of luteal structure for short time (3-4 days), luteinization of the follicles, after the regression of the luteal structure, Gn surge and ovulation occurs and CL is formed
        
        o After this, normal ovary cycle begins
  - - - cause failure of follicular development and ovulation
        
        Eventually, ovarian follicle activity ceases, oestrogen concentration drop, and due to loss of -ve inhibition by oestrogen, GN concentration increases dramatically
    - - But as observed in dog, as age increase, ovarian cycle also increases, due to increased intervals between estrus, litter size also diminishes
  - - - Testosterone (aromatized to estrogen) causes masculinization of the sexual centers in the hypothalamus
      - Absence of testosterone, the hypothalamus becomes feminized
    - - change in hormone concentration
      - Synergism between hormones : estrogen priming before progesterone
      - Sequence of exposure to hormones : progesterone priming required before oestrogen exposure
        
        exposure to progesterone required prior to exposure to estrogen to express estrus. First estrus cycle doesnt elicit estrus behaviour unless first exposed to progesterone
      - Testosterone increases sexual predisposal to female primate
      - GnRH increase sexual receptivity due to its surge preovulatory release
  - - - suppressive effect on ovarian activity
        
        Suckling stimulate prolactin synthesis by suppressing the production of prolactin inhibiting factors such as dopamine and GnRH
    - - Caused period of active ovarian cycle and another period of inactive ovarian activity (anestrus) in a year
    - - Must have adequate level of nutrition to initiate ovarian activity
        
        Lactating cows in postpartum period are unable to resume ovarian cycle unless deficit of nutritional balance is met
    - - Attraction of male to female during sexual receptivity
      - Whitten effect = estrus synchronization with the introduction of male, causes release of Gn
      - Bruce effect = blockage of pregnancy development by introduction of strange male in proximity to recently bred female, by blocking release of prolactin that maintains CL in rodent, causes regression and eventually fetal loss
- - - - 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
        
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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
      - Fertilization occurs in ampulla
        
        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
    - - How does body recognize it is in pregnacy?
        
        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
      - PGF2a synthesis must be suppressed
        
        Modification of synthesis (reduce synthesis)
        
        Change secretion from pulsatile to continuous, absence of pulsatile secretion of PGF2a helps in maintenance of CL
    - - Type of implantation
        
        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
      - Function
        
        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
  - - - PGF2a
        
        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
      - Cortisol initiates oestrogen which initiates PG synthesis
        
        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
      - Oestrogen
        
        Causes formation of oxytocin receptors in myometrium
      - Oxytocin
        
        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
      - Relaxin
        
        Causes ligament and associated muscles surrounding pelvic canals to relax, allowing fetus accomodate
    - - First Stage
        
        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)
      - Second Stage
        
        Actual delivery
      - Third Stage
        
        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
    - - make physical adjustment to life outside such as closure of foramen ovale, ductus arteriosus, and ductus venosus as well as change in lung environment from liquid to gaseous
- - - - Form hollow structure called alveoli
        
        Alveoli is surrounde by myoepithelial cells
        
        Groups of alveoli form lobules which together form lobes
    - - Milk is usually stored here
      - All ducts empty into a large duct
        
        Large duct empty into cisterns a modified storage area
    - - Median suspensory ligament
      - Lateral suspensory ligament
  - - - Intially controlled by embryonic mesenchyme
    - - Estrogen, growth hormone and adrenal steroids
        
        Development of duct system
      - Progesterone and prolactin
        
        Development of alveoli
  - - - Inhibition is removed at or just before parturtion
    - - Highly nutritious
      - Enable passive protection against infectious agents
        
        Contain immunoglobulin obtained from mother via plasma cells migrating from adjacent tissue site
        
        Immunoglobulin can only be absorbed by neonatal gut within first 24-36 hours
  - - - Synthesized upon receiving mechanical stimulus from teat suckling or milking process
      - Dopamine inhibit prolactin synthesis so during milking, dopamin secretion is blocked
      - Vasoactive intestinal peptide stimulate prolactin synthesis
    - - Fat
        
        synthesized from pincing of lipid droplet near plasma membrane at the apex of alveolar cells
        
        energy source, helps offset heat loss in the young
      - Milk proteins
        
        aka. caseins synthesised at endoplasmic reticulum then transfered to Golgi apparatus. released via exocytosis together with lactose
      - Lactose
        
        join milk protein within golgi vesicles and are released from alveolar cells via exocytosis
        
        Main carb
        
        animals must have jejunal lactase to breakdown lactose or lactose will cause osmotic effect leading to diarrhea
        
        Formed from direction of lactose synthetase, an enzyme that is formed from a-lactaalbumin
        
        Progesterone inhibits a-lactaalbumin synthesis
  - - - initiate myoepitelial cells contraction that surrounds the alveoli
      - released via neuroendocrine reflex
        
        tactile stimulation from suckling
        
        manual stimulation of udder during washing before milking
        
        visual, auditory and olfactory stimuli
        
        Ferguson reflex (oxytocin released due to cervical distension), recreated by farmer by blowing air into the cervix through the vagina
  - - - have good carb storage
        
        allows them to stand to start suckling, hypoglycemia wont immediately affect the neonates allowing them to take time to stand and find udder to start suckling
    - - have low carb storage
        
        usually nestled near the mammary gland, are susceptible to hypoglycemia so they need to suckle asap within 30 minutes
        
        Hypoglycemia causes stasis of bowel and neonatal sepsis
  - - - involution of alveolar cells due to back up pressure of milk which also causes inhibition of lactogenesis
    - - Can be induced by using hormone treatement (oestrogen and progesterone)
      - Growth hormone to enhance milk production by diverting nutrients absorbed towards milk synthesis
      - Increased photoperiod exposure associated with increased prolactin secretion
- - - - Hypothalamus
      - Adenohypophysis
    - - Testes
        
        suspended within scrotum by spermatic cord and external cremaster muscle
        
        Located outside abdomen for lower temp
        
        temp must be 2-6 degree lower than body temp, as elevated temp reduces numbers of live normal spermatozoa
        
        Thermoregulation
        
        pendulous scrotal sac
        
        regulate through conduction, convection and evaporation
        
        testicular vasculature
        
        highly coiled and convoluted
        
        reduces mean blood pressure
        
        form venous pampiniform plexus network surrounding testicular artery
        
        allow counter current heat transfer from high heat (artery) to low heat (vein)
        
        dartos and cremaster muscles
        
        control surface area of scrotum
        
        move testes closer or father from abdomen
        
        scrotal skin
        
        thin, lack of hair/fur and fat
        
        Have sebaceous gland and sweat gland
        
        allow evaporation
        
        Extensive blood and lymphatic system
        
        facilitate heat loss through radiation of heat to the environment from blood vessels
        
        has thermoreceptors
        
        Leydig cells
        
        secretes testosterone, bath seminiferous tubules in fluid rich in testosterone
        
        Seminiferous tubles
        
        has 2 compartments
        
        basal
        
        mitosis of spermtogonia
        
        adluminal
        
        meiosis of spermatocytes
        
        has Sertoli cells
        
        provide nourishment to developing spermatocytes
        
        Rete testis
        
        connects testis to epididymis, carrying spermatozoa and fluid
      - Epididymis
        
        consists of head, body and tail
        
        conduit for spermatozoa, allowing them to mature here to be capable of fertilization
      - Vas Deferens
        
        in some species, have ampullae, which act as storage, basically a modified end of epididymis, closely related to ampulla gland?
      - Accessory sex glands
        
        ampullary glands
        
        seminal vesicles
        
        prostate gland
        
        bulbourethral gland
      - Penis
        
        copulatory organ
      - Transfer of spermatozoa
        
        Emission is the release of spermatozoa and accessory gland fluids into the pelvic urethra as a result of sympathetically mediated thoracolumbar reflex contraction of the smooth muscle in the ductus deferens and accessory glands
        
        Ejaculation is the forceful expulsion of semen from the urethra and is prompted by a parasympathetically mediated sacral reflex that induces rhythmic contractions of the bulbospongiosus, ischiocavernosus, and urethralis muscles
        
        After ejaculation, a sacral sympathetically mediated increase in the smooth muscle tone of the cavernous spaces increases the outflow of blood, and contraction of the retractor penis muscle withdraws the penis into the prepuce
  - - - Spermatocytogenesis
        
        has 2 functions:
        
        mitosis of type A spermatogonia that are still uncomitted to immediate spermatozoa production, increase stem cell population
        
        conversion of type A to type B spermatogonia that will undergo mitosis to produce primary spermatocytes that are ready to undergo meiosis for spermatozoa production
      - Meiosis
        
        production of haploid germ cells, spermatids
      - Spermiogenesis
        
        spermatids undergo several transformation to before released as spermatozoa
        
        formation of acrosome
        
        condensation and elongation of nucleus
        
        formation of flagellum
        
        extensive shedding of cytoplasm
        
        after spermiogenesis, is called spermatozoon, consists of:
        
        Head
        
        contain genetic information for fusion with oocyte
        
        covered by acrosome that contains hydrolytic enzyme to enable penetration of oocyte
        
        Middle piece
        
        contains mitochondria to generate energy for movement
        
        Tails
        
        for movement
  - - - Adenohypophysis
        
        Testes
        
        Leydig cells
        
        Binding of LH
        
        Stimulates conversion of cholestrol to testosterone (a type of androgen)
        
        Testoterone
        
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        Sertoli cells
        
        Binding of FSH and testosterone
        
        Synthesize ABP
        
        Synthesize inhibin
        
        stimulate steroid production of Leydig cells
        
        potent inhibitor of FSH from pituitary
        
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        Synthesize estrogen
        
        inhibit LH synthesis throught negative feedback on hypothalamus or adenohypophysis
        
        Synthesize transferin
        
        involved in nutrients transfer to germ cell
        
        release FSH and LH
        
        LH binds to receptor on Leydig cells
        
        FSH binds to receptor on Sertoli cells
      - Secretes GnRH in pulsatile manner
        
        Affect gonadotropic cells of adenohypophysis
  - - - ejaculate contains 50x10^6 with 10% or more motile spermatozoa
    - - Breed
      - Energy intake
      - Season of birth
  - - - positive
        
        administration improve athletic performance
      - negative
        
        use during pre or peripuberty may hinder puberty
        
        impair testicular endocrine function
        
        reduce seminal quality
        
        reduce daily sperm output
        
        reduce testicular size
        
        impairment of spermatogenesis