uterus of mammals

1. Uterus and its modification in
mammals

2. Uterus
• Uterus is an inverted pear shaped organ of female
reproductive sytem.
• It is a hollow cavity of female mammals in which the fertilized
eggs implant and develops.
• It is situated between the fallopian tube and the vagina.
• It is also known as womb.
Ref. www.britannica.com

3. Structure of the Uterus
• It is 2.5 to 3.0 inches long and about 2.0 to 2.5 inches across at
the top.
• The Fallopian tube enters the uterus from the top and the cervix
extends down the vagina.
• Oviduct serve as passageways for ova to reach uterus.
• It is lined by the endometrium.
Ref. – Man & Vertebrates by Romer

4. Anatomy of Uterus
• From outside to inside the path of the uterus is as follows:
• Vagina:Vagina are soft ,distancible, cornified and also grandular in
some of the animals.
• Vagina joins posteriorly by excretory duct urethra to form a
common urogenital cavity, the vestibule.
• It is absent in monotremes.
• In marsupials vagina is a double organ.
• In placental mammals a single vagina is
present.

5. B:Cervix Uteri(Neck of the Uterus)
It is situated at the neck to the vagina called the neck of uterus.
It is divisible into the following three categories:
1:External orifice of uterus.
2:Canal of the cervix
3:Internal orifice of uterus.
C : Corpus uteri
It is known as body of uterus
Made up of:
1:Cavity of body of uterus
2: Fundus

6. Histology
• 1: Endometrium:
• Lining of the uterine cavity is called endometrium.
• In most of the mammals including humas the endometrium builts a
lining periodially which if no pregnancy occurs is shed or reabsorbed.
• 2:Myometrium.
• Uterus consists of a smooth muscle known as myometrium.
• The inner most layer of the myometrium is
• known
• as junction zone.
• 3:Perimetrium
• It is a loose connective tissue around the
• uterus.
• 4:Peritoneum.
• Uterus is surrounded by the peritoneum.

7. Position of Uterus
• Under normal conditions , the
uterus is antiflux and
antiverted.
• Sometimes is also found in
retroverted or retroflexed
condition .
• It is lined by following
ligaments:
• 1-Anterior ligament
• 2-Posterior ligamnet
• 3-Lateral ligament
• 4-Uterosacral ligament
• 5-Round ligament
• 6-Ovarian ligament
Ref. – www.britannica.com

8. Modification of Uterus
• 1-Duplex Uterus
• It is the most primitive type found
in Eutherian mammals. For
example:Lagomorpha.
• In this type , there are two
separate uteri i.e., completely
double uterus with two cervices,
hence known as duplex uterus.
• Uteri opens into the vagina via
two openings known as os-uteri.
• In montremes , the genital tract is
without vagina . For example :
Ornithorhynchus
• In marsupials, dupex uterus and
dupex vagina is found.
• In placental mammals, the oviduct
unites to form single vagina. For
example : Elephant.

9. Bipartite Uterus
• Here, the uterus is “Y” shaped externally.
• There is beginning of fusion between two uteri
• Examples : Carnivores, pigs,some ungulates.
• It is also found in some ungulates.
Ref Life of Vertebrates by Young

10. Bicornuate Uterus
• These are found in sheep , whales , bats.
• Here, the uterus consist of an enlarged posterior cavity
with two uterine horns leading into it.
• In this type , a larger portion of oviduct functions as
uterus.

11. Simplex Uterus
• It is characteristic of primates including man.
• There is fusion of uterus complete to the mullerian duct
i.e., – uterus and vagina become completely fused.
• There is a single uterine cavity.
• Placenta consists of villi of uterine wall.

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