Learning Reproduction in Farm Animals

04-Endocrine Glands & Hormones

Learning Objectives:

To understand what the reproductive endocrine glands and hormones are.
To understand the characteristics and functions of these hormones.
To understand how the concentrations of these hormones in the blood are controlled.

Endocrine Glands of Reproduction

Endocrine Control of Reproduction

Hormone - Chemical messenger produced by a ductless gland or tissue and carried in the blood to a target organ where it effects a change in cellular activity.

Chemical types of hormones:

Peptide - Few - Several amino acids

Protein - Long chains of amino acids

Glycoprotein - Protein hormone with carbohydrate molecules

Hormone Disappearance Rate

Steroid Hormones - Sex Steroid Biosynthetic Pathway

Synthetic Hormones

Fatty Acids

Concept of Receptors: Cells of target organ have specific receptors for hormones.

For protein & peptide hormones - receptor is in plasma membrane.

For steroid homrones - receptor is in nucleus

For prostaglanding hormones - receptor is in plasma membrane.

Hormone Receptor Activation

Gland	Hormone	Chemical Class	Principal Functions
Ovary Graafian Follicle	Estrogens (Estradiol)	Steroid	Mating behavoir, Secondary sex characteristics, Maintenance of female duct system , Mammary growth
	Inhibin (Folliculostatin)	Protein	Regulates release of FSH from anterior pituitary
Corpus Luteum	Progestins (Progesterone)	Steroid	Maintenance of pregnancy, Mammary growth & secretion
	Relaxin	Polypeptide	Expansion of pelvis Dilation of cervix
Testis Leydig Cells	Androgens (Testosterone)	Steroid	Male mating behavior, Spermatocytogenesis, Maintenance of male duct system & accessory glands
Sertoli Cells	Inhibin	Protein	Regulates release of FSH
Adrenal Cortex	Glucocorticoids (Cortisol)	Steroid	Induction of partruition by fetus Milk synthesis Stress response
Placenta	Human Chorionic Gonadotropin (HCG)	Glycoprotein	LH-like - Involved with establishment of pregnancy in human. Support and maintain CL
Endometrial Cups Mare	Equine Chorionic Gonadotropin (eCG) Old name - Pregnant Mare Serum Gonadotropin (PMSG)	Glycoprotein	FSH-like- some LH activity Immunological protection of foal during pregnancy Formation of accessory CL in mare
	Estrogens/Progestins	Steroids	Regulate placental bloodflow Maintenance of pregnancy
	Relaxin	Protein	Relaxation/dialation of cervix for parturition
	Placenal Lactogen	Glycoprotein	Stimulates mammary growth & milk secretion.
Uterine Endometrium Graafian Follicles Seminal Vesicles	Prostaglandin F2a (PGF2a)	Lipid	Regression of CL Stimulate myometrial contractions Ovulation Sperm transport
Liver	Insulin-like Growth Factors IGF-I & IGF-II	Protein	Stimulates steroidogenesis, Stimulates mammary growth and fetal development
Pineal Gland	Melatonin	Biogenic amine	Control of seasonal reproduction in Mare & Ewe Regulate hair growth
Posterior Pituitary	Oxytocin	Octapeptide	Stimulate myometrial contractions for sperm transport, parturition & milk ejection
Anterior Pituitary	Follicle Stimulating Hormone (FSH) - Follicotropin	Glycoprotein	Stimulate follicle growth Stimulate estrogen production Spermiogenesis in male
	Luteinizing Hormone (LH) - Luteotropin	Glycoprotein	Stimulate ovulation Support CL formation, and progesterone secretion Stimulate testosterone synthesis by leydig cells of testis
	Prolactin	Protein	Stimulate milk synthesis Regulate metabolism for milk synthesis Effects Maternal Behavior
	Adrenalcorticotropic Hormone (ACTH)	Protein	Release of corticosteroids & glucocorticoids from adrenal cortex to initiate parturition
Hypothalamus	Gonadotropic Releasing Hormone (GnRH)	Decapeptide	Stimulates release of FSH and LH from anterior pituitary
	Dopamine	Biogenic Amine	Inhibits release of prolactin
	Corticotropic Releasing Hormone (CRH)	Peptide	Stimulates ACTH release
	Growth Hormone-Releasing Hormone (GRH)	Peptide	Stimulates release of growth hormone
	Oxytocin	Octapeptide	Produced by the hypothalamus, released at the posterior pituitary.

Control of endocrine gland function.

Hypothalamus - Pituitary interrelationships.

Hypothalamo-hypophyseal portal system caries hypothalamic hormones specifically to the anterior pituitary without dilution in the systemic blood.

Specific hypothalamic nuclei secrete releasing or release inhibiting factors that control release of pituitary hormones.

Preovulatory LH surge is controlled by gonadotropin releasing Hormone (GnRH) from the surge center.

Tonic LH release controlled by:

Median Eminence (ME)

Feedback Diagrams

Oxytocin Release

Prostaglandin Control in Luteolysis

Illustration Notes

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