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2011-12-01 17:09:28
vet tech theriogenology chapter 10 part reproductive anatomy physiology male dog set

vet tech theriogenology chapter 10 part 2 reproductive anatomy and physiology of the male dog set
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  1. The Dog
    male dogs are sexually active throughout the year without any influence of season
  2. Puberty
    • when the dog releases spermatozoa in the ejaculate
    • 9-12 months old, sexual maturity is not reached until 15-16 months old (some are 5-6)
    • neuter 5, 6, 7 months old
  3. Normal testes
    • descend into the scrotum a few days after birth...
    • ...may be difficult to palpate at this time (wasilt withdrawn back into inguinal ring)
    • present in scrotum by 8 weeks of age 9can be delayed as late as 6-8 months)
    • >8 months - usually will not descend
    • spermatozoa output is related to testis size
    • - large dogs prodce more spermatozoa than small dogs
    • cryptorchid makes neuter more of a surgery
  4. Spermatogenesis
    • takes place in testes
    • production of male gametes (sperm cells) 62 days
    • during prepubertal period, differentiate into spermatogonia (primary germ cell - becomes spermatozoa) until puberty
    • blood supply network & specialized muscular tissue maintains the temperature of blood supplying the testes below normal BT (body temperature)
  5. Spermatogonia
    primary germ cell
  6. Spermiocytogenesis
    • first stage of spermatogenesis
    • - spermatogonia divide mitotically (seminiferous tubules) to produce new spermatogonia and primary spermatocytes
    • - primary spermatocytes undergo meiotic division to produce secondary spermatocytes
    • - secondary spermatocytes divide meiotically to produce spherical spermatids
  7. Spermiogenesis
    • second stage of spermatogenesis
    • - spherical spermatids mature into elongated spermatids
  8. Spermiation
    • final stage of spermatogenesis
    • - process of release of the elongated spermatids into the lumen of the seminiferous tubules as spermatozoa
  9. Crytorchidism
    • failure of the testes to descend into the scrotum
    • animal is said to be cryptorchid:
    • - unilateral cryptorchid - one side or the other undescended
    • - bilateral cryptorchid - both sides undescended
    • can be genetically influenced
    • more than one reason for cryptorchidism
    • don't want to breed cryptorchid dog
    • can sometimes find undescended testicle with ultrasound
    • - fine white band around testicle if not atrophied (in dogs only)
  10. Prostate
    • only accessory gland in the dog
    • secretes a fluid which liquifies the coagulated semen
    • located caudal to the neck of the bladder, encircles urethra (bladder to outside)
    • androgen (male hormones) dependent (increases in size with testosterone secretion and decreases in size with estrogen secretion
    • size of prostate gland increases with age...
    • - benign prostatic hyperplasia
    • signs of increased signs may inlcude constipation and straining to defecate
    • - could also affect urethra
  11. Mating
    • coitus
    • - protracted procedure
    • - can last up to 20 minutes
  12. Ejaculate
    divided into 3 fractions
  13. First fraction of ejaculate
    • presperm fraction
    • clear fluid with little or no spermatozoa
    • volume varies from a few drops to 10 mls
    • produced while the dof is thrustig and attempting intromission
  14. Second fraction of ejaculate
    • sperm rich
    • milky in color due to presence of numerous spermatozoa
    • volume varies from 1 ml to 2 mls
  15. Third fraction of ejaculate
    • prostatic fluid
    • clear fluid with few spermatozoa
    • can be secreted for 15 minutes or more
  16. Manipulation of reproduction in the dog
    • surgical castration
    • chemical castration
  17. Surgical castration
    • neuter
    • removal of the testicles
    • removew the source of testosterone
    • prostate gland becomes smaller after castration
    • reduces the amount of tissue build up (muscle) because testosterone is an anabolic steroid
  18. Chemical castration
    • blocking of testosterone without actually removing the testicles
    • production of spermatozoa is stopped because testosterone is needed to permit the production of sperm
    • estrogen or progesterone
    • Neutersol (TM)
    • - injected into the testicle - topical anesthetic/sedative
    • - necrotizing agent
    • - 99.6% effective
    • - male dogs, 3-10 months old
    • - does not halt testosterone production completely
    • - atrophy of the testicles, epididymus, and prostate gland
    • - scar tissue formation which prevents movement of sperm from testicles through epididymus