Learning Reproduction in Farm Animals

04-Endocrine Glands & Hormones



 

Learning Objectives:

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.

   
 
 
 
 
 
 
 
 
 
 

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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