Document Detail

Fetomaternal interactions and influences during equine pregnancy.
MedLine Citation:
PMID:  11277870     Owner:  NLM     Status:  MEDLINE    
The equine embryo takes 6 days to traverse the oviduct and, when it finally enters the uterus, it remains spherical in shape and moves continually throughout the uterine lumen until day 17 after ovulation to deliver its maternal recognition of pregnancy signal to the entire endometrium. Between day 25 and day 35 after ovulation, the trophoblast cells of a discrete annulate portion of the chorion multiply rapidly and acquire an invasive phenotype and, between day 36 and day 38, migrate deeply into the maternal endometrium to form the equine-unique endometrial protuberances known as endometrial cups. These cups secrete large quantities of a gonadotrophic hormone (eCG) into the maternal circulation which, in conjunction with pituitary FSH, stimulates the development of accessory luteal structures in the maternal ovaries to supplement the supply of progesterone to maintain the pregnancy until the placenta can assume this role at about day 100. The non-invasive allantochorion extends slowly to fill the uterus by days 80-85 and its microcotyledonary architecture, which provides both haemotrophic and histotrophic nutrition for the growing fetus, is not fully established until days 120-140. The fetoplacental unit synthesizes large quantities of steroid hormones during the second half of pregnancy, using fetal C-19 precursors secreted by the enlarged fetal gonads for the production of oestrogens and maternal C-21 precursors for the synthesis of progesterone and large quantities of 5alpha-reduced progestagens. Near term, additional pregnenelone is secreted by the fetal adrenal glands so that the mare exhibits the unusual phenomenon of foaling while maternal serum progestagen concentrations are increasing and oestrogen concentrations are decreasing.
W R Allen
Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Reproduction (Cambridge, England)     Volume:  121     ISSN:  1470-1626     ISO Abbreviation:  Reproduction     Publication Date:  2001 Apr 
Date Detail:
Created Date:  2001-03-30     Completed Date:  2001-07-19     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  100966036     Medline TA:  Reproduction     Country:  England    
Other Details:
Languages:  eng     Pagination:  513-27     Citation Subset:  IM    
Thoroughbred Breeders' Association, Equine Fertility Unit, Mertoun Paddocks, Woodditton Road, Newmarket, Suffolk CB8 9BH, UK.
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MeSH Terms
Embryo Transfer / veterinary
Embryonic and Fetal Development
Endometrium / physiology
Extraembryonic Membranes / physiology
Fetus / physiology*
Gestational Age
Gonads / embryology
Horses / physiology*
Pregnancy, Animal / physiology*

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