PregnancyCorpus Luteum Dependency and

Non-Dependency

Corpus Luteum

•Yellow Body (Latin)

•The remains of a follicle after ovulation

•Corpus Luteum Haemorrhagicum

•Endocrine Gland

Corpus Luteum• Two Hormonal Mechanisms

• First System

• Ensures morphogenesis

• Stimulates Progesterone Production

• Second System

• Stops secretory phenomena

• Morphological regression

Corpus Luteum

•Luteal Phase

•Estrogen and Progesterone secreted by CL exert Negative Feedback on GnRH release

•decreased FSH and LH

Corpus Luteum•Fertilization

•Blastocyst trophoblast secretes Chorionic Gonadotropin

•Corpus Luteum Graviditatis

•No Fertilization

•CL degenerates into Corpus Luteum Albicans

Hormones

Luteinizing Hormone

OvarianInterstitial

Cells

Corpus Luteum

Formation

Hormones

Corpus Luteum

Development , Maintenance of Female Characteristics

Oocyte maturation

Uterine Proliferation

Estradiol-17β

ProgesteroneMaintains uterine secretion

Stimulates mammary duct formation

Most Tissues

Uterus, Mammary Glands

Increased FSH and LH levels stimulate secretion

Increased LH and prolactin levels stimulate Secretion

Hormones

PlacentaChorionic

Gonadotropin

Further growthof

Corpus Luteum

Corpus Luteum and Pregnancy

•Placental Chorionic Gonadotropin takes over the gonadotropic function of the anterior pituitary during early pregnancy by maintaining the CL

•Placenta will soon take over CL function

Corpus Luteum and Pregnancy

•Gestation

•Progesterone and Estrogen from CL or placenta

•Initiates mammary tissues in preparation for lactation

Corpus Luteum and Pregnancy

•Life span of CL prolonged during pregnancy

•Stimulation maybe due to presence of embryo

Corpus Luteum of Pseudo-Pregnancy

•If no pregnancy resulted, CL disappears after 12 days after ovulation and the estrous cycle is re-established

•CL of pseudo-pregnancy cause an increase in uterine size and proliferation of mammary glands that may tend to lactate

Importance of CL to Animals

• Sheeps and Pigs

• presence of embryos prolong CL life span but does not increase functional capacity

• CL of pregnancy dependent on embryo

• may protect CL from lytic effects of the uterus

• may block uterus from acquiring its lytic properties

Importance of CL to Animals

• Guinea pig, rat, mouse

• life-span and the functional activity of the the CL increased during pregnancy

• luteal function of CL is affected by the presence of the embryo

• In guinea pigs, embryos maintain and stimulate CL of pregnancy independently of hypophyseal control from 2nd/3rd day after mating

Importance of CL to Animals

• Incomplete Cyclers

• such as laboratory rodents

• CL is the major source of progesterone only after an ovum is fertilized

• Equidae

• CL of pregnancy degenerates in early gestation but replaced by accessory corpora lutea

Importance of CL to Animals

•Ewes can maintain pregnancy without CL after the 55th day of gestation

•Torpedo marmorata

•CL is reported to be steroidogenic

•Nectophrynoides occidentalis

•CL remain throughout pregnancy and secrete progesterone

Nectophrynoides sp. Torpedo marmorata

Importance of CL to Animals

•Macropus eugenii

•removal of CL before day 17 interferes with successful parturition

•progesterone and relaxin from CL are needed for a healthy birth of a young

Macropus eugenii

Importance of CL to Animals

•Mustelid carnivores, some kangaroos

•CL regulate the embryonic diapause of the blastocyst

Importance of CL to Animals

•There are some species in which CL are not affected by pregnancy

•Mustela furo

•CL are maintained by a pituitary luteotrophin

•Unaffected by any placental luteotrophic effect

Mustela furo

Importance of CL to Animals

•Mustela mustela and Mustela vison

•Embryo have little effect on luteal function

•CL of pregnancy closely resembles CL of pseudo-pregnancy

Importance of CL to Animals

•Didelphis virginiana

•CL of gestation regresses before parturition

•Trichosurus vulpecula

•presence of embryos in the uterus is totally without effect on CL

Didelphis virginianaTrichosurus vulpecula

Importance of CL to Animals

•In reptiles,

•CL formation follows ovulation

•Duration is brief esp. in egg-laying species

•Thamnopis elegans

•Luteoctomy caused a delay in parturition; young have placenta with yolk still in yolk sac

Importance of CL to Animals•Storeria dekayi

•CL contains 21-dehydrolase

Thamnopis elegans

Storeria dekayi

References• Casida, L. E., & E. J. Warwick. The Necessity of the Corpus Luteum for

Maintenance of Pregnancy in the Ewe. J Anim Sci 1945. 4:34-36.

• Denamur, R. Formation and Maintenance of Corpora Lutea in Domestic Animals. J Anim Sci 1968. 27: 163-180.

• Jameson, E. W. Jr. (1988). Vertebrate Reproduction. John Wiley & Sons : Canada.

• Moor, R. M. Effect of Embryo on Corpus Luteum Function. J Anim Sci 1968. 27: 97-118.

• Nalbandov, A. V. (1958). Reproductive Physiology : Comparative Reproductive Physiology of Domestic Animals, Laboratory Animals and Man. W.H. Freeman : San Francisco, USA.

• Randall, D., W. Burggren & K. French. (2002). Eckert Animal Physiology (5th ed.). W.H. Freeman : China.