vet-tech-therio-ch-9

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  1. Genetic Material
    • in nucleus of each cell in the body
    • genes passed on to next generation via the gametes
    • - ova in female
    • - spermatozoa in male
  2. Genetic sex of an animal
    • established at fertilization
    • depends on whether the spermatozoan carries the X or Y chromosome
  3. Phenotype
    • physical expression
    • depends on the action of sex-determining genes (trigger gonad development)
    • secretion of reproductive hormones from the gonads
    • action of these hormones leads to the development of the reproductive system
  4. Reproductive hormones
    • estrogen and testosterone are the biggies
    • control ovulation and fertilization
    • implantation and growth of the embryo into a fetus
    • parturition
  5. Reproductive physiology
    control starts in the brain - hypothalmus and pituitary
  6. Hypothalmus
    • governs the reproductive system
    • send signals to the pituitary gland (hypophysis or hypophyseal gland)
    • lies below the thalmus at the base of the brain
    • actually is part of the brain
    • main action is to control the amount and type of gonadotropic hormones secreted by the pituitary gland
    • other actions:
    • - is responsible for the timing and onset of puberty
    • - sexual interest and the mating drive
    • - supresses production of prolactin
    • - secretes gonadotropin releasing hormone (GnRH), which acts upon pituitary
    • receives neural input from other parts of the brain and its secretion is influenced by...
    • - daylight length
    • -- influences the pineal gland (secretes melatonin during the hours of darkness)
    • - smell
    • -- pheremones (animals smells) can trigger hypothalmic secretions
    • -- eg "ram effect" - ram secretes hormones to bring ewe into season
    • - nutrition
    • -- very thin animals stop their reproductive cycles
    • -- body can't support a pregnancy
    • - sound
    • -- calling cats will bring a tom cat - trigger hypothalmic secretion increasing tom's libido
    • - fear
    • -- of a dominant male
  7. Pituitary gland (hypophyseal gland or hypophysis)
    • controls the gonads - testes or ovaries
    • is an extension of the brain
    • hollow stalk is a part of the 3rd ventricle of the brain
    • divided into 2 parts:
    • - anterior pituitary or anterior lobe (adenohypophysis)
    • - posterior pituitary
  8. Anterior pituitary or anterior lobe (adenohypophysis)
    • secretes 4 reproductive hormones:
    • - luteinizing hormone (LH)
    • - follicle stimulating hormone (FSH)
    • - prolactin
    • - adrenocorticotropic hormone
    • LH and FSH are the pituitary gonadotropins (act upon the gonads)
  9. Testes or ovaries
    release hormones that influence other parts of the reproductive tract
  10. Male reproductive hormones control...
    • production of spermatozoa in the testes
    • development of the male type phenotype:
    • - thickened cheek pouches of the male tom cat - will shrink a bit if neutered
    • - crest or curve of the neck in the stallion
    • development of the male libido (sex drive)
  11. Female reproductive hormones control...
    • development of the follicles and maturation of the oocytes (ova or eggs)
    • maintenance of pregnancy and lactation
    • development of female behavior
    • more complex reproductive cycle than male
  12. Hypothalamo-hypophyseal axis
    describes the relationship between the hypothalmus and the pituitary gland
  13. Luteinizing hormone
    release of LH is stimulated by gonadotropic releasing hormone (GnRH) from the hypothalmus
  14. Luteinizing hormone in the female
    • high levels
    • - a surge of LH stimulates ovulation
    • low levels
    • - assists FSH in stimulating the development of the follicle in the ovary
    • - supports the corpus luteum in the ovary
    • - stimulates the production of progesterone by the luteal cells (in corpus luteum)
  15. Luteinizing hormone in the male
    • stimulates the Leydig cells of the testes to secrete testosterone
    • high levels
    • - acts as a negative feedback on the hypothalmus and reduces the amount of GnRH produced
  16. Follicle Stimulating Hormone
    release is stimulated by gonadotropin releasing hormone (GnRH)
  17. Follicle Stimulating Hormone in the female
    • stimulates production of follicles in the ovary
    • high levels
    • - acts as a negative feedback on the hypothalmus and reduces the amount of GnRH produced
  18. Negative feedback
    used as a check and balance mechanism
  19. Follicle Stimulating Hormone in the male
    • stimulates the Sertoli cells of the testis to produce androgen binding protein
    • - which stimulates spermatogenesis
    • high levels
    • - acts as a negative feedback on the hypothalmus and reduces the amount of GnRH produced
  20. Prolactin
    • high levels
    • - stimulates production of milk
    • low levels
    • - maintains the corpus luteum in the ovary
  21. Adrenocorticotropic hormone (ACTH)
    stimulates the adrenocortex to release corticosteroids
  22. Corticosteroids in reproduction
    initiate the cascade of events that result in parturition
  23. Posterior Pituitary
    • secretes oxytocin which:
    • - causes milk letdown
    • - causes smooth muscle contraction (uterus)
    • - acts as a prostaglandin precursor (causes corpus luteum regression)
  24. Hormones in female reproductive system
    • hypothalmus makes:
    • - gonadotropin-releasing hormone (GnRH)
    • pituitary gland makes:
    • - follicle stimulating hormone (FSH)
    • - luteinizing hormone (LH)
    • ovaries make:
    • - estrogen (Graafian follicles)
    • - progesterone (corpus luteum)
  25. How a cycle works
    • 1. The hypothalmus secretes gonadotropin releasing hormone (GnRH)
    • 2. This stimulates the pituitary gland to release follicle stimulating hormone (FSH)
    • 3. Its presence in the blood causes the Graafian follicles to grow
    • 4. As they grow, they produce estrogen
    • 5. The higher levels of estrogen in the blood causes the pituitary gland to stop releasing FSH and start releasing luteinizing hormone (LH)
    • 6. This causes the Graafian follicles to rupture, releasing eggs.
    • 7. The ruptured follicle, now a corpus luteum, starts releasing progesterone (needed to maintain pregnancy) into the blood.
    • 8. Its presence stops the pituitary gland from releasing LH and FSH.
    • 9. If conception occurs, the corpus luteum becomes functional and produces progesterone to maintain pregnancy.
    • 10. If conception does not occur, the corpus luteum disappears and progesterone level lowers to the point where cycle ends.
  26. Gonadotropin-releasing hormone (GnRH)
    • produced in the hypothalmus
    • secreted by the pituitary gland to release gonadotropins (LH, FSH)
  27. Graafian follicles
    • small sac in the ovaries the enclose an ovum
    • immature follicles contain an undeveloped egg cell
    • mature follicles break open and release an ovum => ovulation
  28. Prolactin
    • promotes growth of mammary tissue
    • stimulates and sustains milk production in postpartum animals
  29. Pineal gland
    • attached to cerebrum of brain
    • functions as a light receptor
  30. Melatonin
    • synthesized and secreted by the pineal gland (during the hours of darkness)
    • suppresses GnRH, which stops reproductive activity
  31. Luteinizing hormone in the female
    • stimulates ovulation of mature follicles
    • stimulates the development of the follicle in the ovary
    • supports the corpus luteum formation
    • stimulates the production of progesterone
  32. Luteinizing hormone in the male
    stimulates Leydig cells of testes to secrete testosterone
  33. Follicle stimulating hormone in the female
    stimulates the production of follicles in the ovary
  34. Follicle stimulating hormone in the male
    stimulates Sertoli cells of testis to stimulate spermatogenesis
  35. Adrenocorticotropic hormone (ACTH)
    stimulates adrenal cortex to release corticosteroids (parturition)
  36. Oxytocin
    • causes milk letdown
    • causes smooth muscle contraction in uterus during parturition
    • prostaglandin precursor - secretion causes corpus luteum regression
  37. Prostaglandin
    • naturally occurring
    • chemically related long-chain fatty acids
    • used in the treatment and regulation of activity of the female reproductive system
    • luteolytic - regression of the corpus luteum
  38. The gonads
    • testis
    • ovary
  39. Testis
    • two different cells produce hormones:
    • - Sertoli cells
    • - Leydig cells
  40. Sertoli cells
    • found within the seminiferous tubules next to the spermatogonia that divide to produce sperm
    • are stimulated by FSH from the anterior pituitary and produce:
    • - Androgen binding protein
    • - Inhibin
    • - Estrogen
  41. Androgen Binding protein
    binds testosterone to stimulate spermatogoenesis
  42. Inhibin
    • depresses secretion of FSH (but has no effect on LH)
    • "seesaw" method of hormone secretion:
    • - as inhibin goes up, FSH goes down
    • - as inhibin goes down, FSH goes down (produces more FSH)
    • - series of checks and balances
  43. Estrogen produced by Sertoli cells
    • testosterone is converted to estrogen (low levels in the male)
    • high levels in the male, inhibit secretions from the anterior pituitary
  44. Leydig cells
    • found between the seiniferous tubules (interstiial cells)
    • stimulated by LH from the anterior pituitary and secrete testosterone
  45. Actions of testosterone
    • inhibit the secretion of LH and FSH, acting as a negative feedback
    • stimulate the growth and activity of the male reproductive tubular genitalia and accessory sex glands and scrotum
    • stimulate spermatogenesis in the presence of androgen binding protein
    • stimulate hypertrophy of cells and organs in general; anabolic (building) activity
    • stimulate male behavior
  46. Male reproductive tubular genitalia
    • epididymis
    • vas deferns
    • ampullae
    • seminal vesicles
    • prostate
    • urethra
    • prepuce
    • penis
  47. Ovary
    • Granulosa cells
    • Luteal cells
  48. Granulosa cells
    • line the tertiary of Graafian follicles in the ovary
    • stimulated by FSH to produce estrogen
  49. Graafian follicles
    small sac in the ovary that encloses the ovum
  50. Actions of estrogen
    • develop and maintain cyclic changes in the female tubular genitalia
    • develop the secretory ducts of the mammary gland and uterine gland
    • stimulate female estrous behavior (mating behavior)
  51. Female tubular genitalia
    • Fallopian tube
    • uterine horn
    • uterine body
    • cervix
    • vagina
  52. Luteal cells
    • cells of the corpus luteum produce:
    • - progesterone
    • - relaxin
    • - oxytocin
    • - estrogen
    • the corpus luteum and the secretion of progesterone is supported by LH secretion
    • LH is luteotropic (stimulates the formation of the corpus luteum)
    • LH & FSH cause ovulation of mature follicles
  53. Progesterone
    • the hormone of pregnancy
    • actions are to:
    • - cause development of uterine glands in an estrus primed uterus
    • - block normal myometrial contractivity of the uterus (prevents premature contractions)
    • - stimulate glandular development of the mammary gland
    • - inhibit GnRH
    • levels rise just before eggs are released
    • testing for progesterone in bitch is a more accurate way to determine the heat cycle than testing for estrogen
  54. Relaxin
    • actions are to:
    • - cause relaxation of the pelvic ligaments and the cervix, enlarging the birth canal
    • - suppress lactation
  55. Oxytocin
    • action is to:
    • - attach to receptors in the uterus and act as a precursor to prostaglandin (which causes regression of the corpus luteum)
  56. Estrogen, progesterone and testosterone
    are steroid hormones
  57. Pineal gland
    • aka epiphyseal cerebri
    • receives messages about day length from other parts of the brain and secretes melatonin
  58. Melatonin
    • turns the hypothalmus on and off
    • synthesized during the hours of darkness
    • action is to supress GnRH
  59. Absence of GnRH
    • no stimulation of the anterior pituitary gland
    • reproduction activity stops
  60. Physiology of parturition
    • onset requires a live fetus
    • secretions from the fetus trigger a cascade of events leading to parturition
    • 1. Trigger for parturition is the secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary of the fetus brought about by...
    • 1a. stress - fetus reaches a size where placenta can no longer supply nutrients for further growth
    • 2. ACTH cause the fetal and maternal adrenal cortex to release cortisol
    • 3. Raised cortisol levels stimulate production of enzymes that allow conversion of progesterone to estrogen
    • 4. Fall in progesterone removes the block of contraction of smooth muscle of the uterus (myometrium)...
    • 4a. frequency and amplitude of uterine contractions increases
    • 5. Raised levels of estrogen stimulates the production of oxytocin (increases uterine contractions)
    • 6. Regression of the corpus luteum - progesterone levels fall even further
    • 7. Increased uterine contractions cause fetus to move towards the cervix
    • 8. Dilation of cervix causes release of oxytocin
    • 9. Oxytocin induces more uterine contractions which further engage fetus in the cervix and pelvis
    • 10. Relaxin is produced by the placenta and/or the maternal corpus luteum and causes relaxation of the cervix
    • 11. Presence of th fetus in the pelvis stimulates contraction of the abdominal muscles and straining
    • 11a. Abdominal muscle straining is responsible for the final expulsion of the fetus through the birth canal
  61. First stage of labor
    • begins with the onset of increased uterine contractions
    • encompasses numbers 1-7 above
  62. Second stage of labor
    • begins when the fetus enters the birth canal and abdominal straining starts
    • number 8 through period when the fetus is expelled
  63. Third stage of labor
    • expulsion of the placenta (fetal membranes)
    • occurs after the expulsion of the fetus in animals that have one fetus or interspersed with the fetus in litter-bearing animals
  64. Presentation
    describes the relationship of the head and body of the fetus to the long axis of the dam
  65. Anterior presentation
    fetal head is coming first
  66. Posterior presentation
    tail comes first
  67. Transverse presentation
    fetus is across the birth canal
  68. Position
    describes where the fetal verterbral column is relative to the birth canal
  69. Posture
    describes the arrangement of the fetal head and limbs
  70. Normal parturition
    anterior presentation and dorsal position with one foreleg slightly in front of the other so that the head and 2 forelegs form a cone
  71. Lactation
    • mammary glands
    • - modified sweat glands
    • - lie along either side of midline of ventral abdomen
    • - development is triggered by rising levels of prolactin and milk
    • - letdown is triggered by oxytocin
    • colostrum
    • - milk released in the first few hours after parturition
    • - high levels of antibodies
    • - passive immunity to newborn
    • - antibodies absorbed undamaged by newborn in first few hours of life because pH of stomach is neutral
  72. Androgens
    • hormones that determine the expression of the male phenotype...
    • including outward development of secondary sex characteristics and initiation and maintenance of spermatogenesis
  73. Estrogen
    • hormone formed in the ovary
    • responsible for secondary female characteristic development
    • act on female genitalia to produce and environment suitable for fertilization, implantation and nutrition of the early embryo
  74. Testosterone
    • most important male sex hormone
    • produced by the Leydig cells of the testes
    • chief function is to stimulate the development of the male reproductive organs and the secondary sex characteristics
  75. Corpus luteum
    a progesterone secreting yellow glandular mass in the ovary formed from the wall of an ovarian follicle that has matured and released its ovum
  76. Luteotropic
    stimulating the formation of the corpus luteum
  77. Parturition
    act or process of giving birth
  78. Adrenal cortex
    • outer part of the adrenal gland
    • produces 3 main groups of hormones: glucocorticoids, mineralocorticoids and androgens
  79. Myometrium
    smooth muscle layer of uterus

Card Set Information

Author:
 darlene.m.nelson
ID:
 115301
Filename:
 vet-tech-therio-ch-9
Updated:
2011-11-08 02:23:36
Tags:
vet tech theriogenology chapter reproductive physiology set
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vet tech theriogenology chapter 9 reproductive physiology set
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