Uterus
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- The uterus has a body and two uterine horns (cornua); species variation is seen.
- Cow, Ewe and Mare
- Bipartite uterus
- Horns completely separated by a septum
- Large uterine body p articularly in the mare
- Sow
- Bicornuate uterus
- Very long folded horns
- Adaptation in litter bearing animals
- Diadelphus uterus
- Platypus
- Male has a forked penis
- Duplex uterus
- Simplex uterus
- Primitive forms of uterus found some times in higher animals do not interfere with fertility
Uterine histology
Three distinct layers
- Outer serous membrane – extension of the peritoneum
- Middle myometrium – outer longitudinal & Inner circular smooth muscles
- Vascular layer in between
- Myometrial contractions synchronized with oviducal contractions
- Contract towards ovary at estrus and towards cervix subsequently
- Estradiol increases but progesterone decreases the myometrial contractions
- Inner endometrium
- Epithelium – simple columnar non ciliated in all domestic animals
- Tall and actively secretory at estrus due to stimulation by estrogens
- Low cuboidal during subsequent two days
- Endometrial Glands
- Open into uterine lumen
- Straight at estrus
- Coiled, complex and increasingly secretory during luteal phase
- Volume & composition of the secretions varies with the phases of the cycle
- Important proteins in different species
- Blastokinin, implantation promoting factor, GPC, steroid hormone receptors and uteroferrin
- Cotyledons in the endometrium of ruminants
- For attachment of fetal membranes
- Endometrial glands absent at cotyledons
Functions of the uterus
- Myometrial contractions
- Occur at mating – cause transport of sperm from site of ejaculation to site of fertilization
- Massaging uterus at AI improves fertility
- After estrus the uterine contractions directed towards cervix
- Uterine contractions kept inhibited by high progesterone levels during gestation
- At the end of gestation progesterone levels decrease and estrogens increase which causes uterine contractions that help in parturition
- Pregnancy could be housed only in the uterus since myometrium has the ability grow enormously
- Endometrial Secretions
- Induce capcitation at estrus
- Stimulate sperm metabolism
- GPC makes glycerol available from phosphoglycerol
- Provide nourishment to pre and early post implantation embryo during luteal phase
- Particularly important in farm animals
- Ex; Cow embryos live freely and proliferate extensively till 30d post estrus
- Estrogen and progesterone receptors in the secretions modulate
- Sensitivity of myometrium and proliferation of endometrial epithelium and glands
- Blastokinin in rabbit uterine secretions promotes blastocyst formation
- Implantation promoting factor present in the mouse uterine secretions
- Uteroferrin found in ewe uterine secretions also promotes embryonic growth and implantation
- Maintenance /Regression of CL
- Sends signals to CL about the presence / absence of the conceptus
- Signals carried via the utero-ovarian veno-arterial pathway
- Hysterectomy prolongs life span but partial hysterectomy regresses CL
- IUDs can also prolong the life span of the CL
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Last modified: Saturday, 7 January 2012, 6:18 AM