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Reproductive Endocrinology

Animal Breeding

Pensacola Jr College

Endocrinology

w Endocrine Glands = ductless glands that secrete hormones directly into the bloodstream

w Hormone = molecule carried by blood to target organ, binds to receptors, regulates an activity

Hormone Types

w Protein hormones

•   Large

•   Have cell surface receptors

•   Break down if given orally

w Steroid hormones

•   Small

•   Have internal cell receptors

•   Absorbed if given orally

Endocrine Control

w Negative feedback = hormone exerts negative control over earlier steps in chain

w Positive feedback = hormone exerts positive control over earlier steps in chain

Example of Feedback Theory

Endocrine Reproductive Glands

Endocrine Reproductive Hormones

 

 

 

Female Repro Hormones

w GnRH made in nerve cell bodies in hypothalamus ΰ portal vessels ΰ carried to anterior pituitary

w Stimulates LH and FSH production in ant. pituitary ΰ carried to ovaries

Female (cont’d)

w LH in ovaries:

•   Causes ovulation

•   Stimulates CL formation

•   Stimulates luteal cells to produce progesterone

w FSH in ovaries:

•   Makes follicles grow

•   Stimulates granulosa cells to produce estrogen, inhibin

Female hormone feedback

w Progesterone has negative feedback on LH, FSH, GnRH

w Inhibin has negative feedback on FSH

w Estrogen

•   small doses have negative feedback on LH, FSH, GnRH

•   Large dose– positive feedback

 

Female repro steroids

w Estrogen = the cycle / preparation hormone

•   Female development

•   Cyclical changes in the reproductive tract, estrus cycle

•   Mating behavior

•   Mammary tissue growth (ducts)

Female repro steroids

w Progesterone = hormone of pregnancy

•   Inhibits mating behavior

•   Maintenance of pregnancy (uterine endometrial growth, stops cycling)

•   Mammary tissue growth (glandular)

Male Repro Hormones

w GnRH made in nerve cell bodies in hypothalamus ΰ portal vessels ΰ carried to anterior pituitary

w Stimulates LH and FSH production in ant. pituitary ΰ carried to testes

Male (cont’d)

w LH in testes:

•   Receptor sites on leydig cells

•   Stimulates testosterone production

w FSH in testes:

•   Receptor sites on sertoli cells

•   Stimulates ABP (binds T) and inhibin production

•   Stimulates sperm formation

Male hormone feedback

w Testosterone has negative feedback on LH, FSH, GnRH

w Inhibin has negative feedback on FSH

 

Male repro steroid

w Testosterone

•   Development and maintenance of all the male ducts, glands, etc.

•   Spermatogenesis

•   Seminal fluid production

•   Male sexual behavior

Prolactin in Reproduction

w Produced by anterior pituitary

w Controls milk production

w Controls reproduction in many seasonal breeders

•   Increases LH receptor sites on CL ΰ increases progesterone

•   Thus, low prolactin delays implantation

Control of Prolactin

w Pineal gland produces the hormone melatonin at high levels during darkness

w Lots of melatonin during short daylength (fall/winter)

w Melatonin inhibits prolactin

w Increasing daylengths thus allow increased prolactin

Oxytocin in Reproduction

w Produced by hypothalamus cell bodies

w Carried on nerve fibers to posterior pituitary for storage

w Functions:

•   Contractions of uterus in birth

•   Milk ejections in lactation

w Positive feedback loop from nerve stimulation

Example Hormone Research in Zoos:

w  “Urinary Steroid Hormone Analysis of Ovarian Cycles and Pregnancy in Mandrills (Mandrillus sphinx) Indicate That Menses, Copulatory Behavior, Sexual Swellings and Reproductive Condition Are Associated With Changing Estrone Conjugates (E1C) and Pregnanediol-3-Glucuronide (PdG

w  Disney’s Animal Kingdom