Mare Reproductive Anatomy

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Mare ReproductiveAnatomy
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Mare Reproduction System

• The mares role on a breeding farm encompasses a
  wide variety contributions.
• In addition to her genetic contribution, the mare
  protects and nourishes her offspring.

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Mare Reproductive Anatomy

• The reproductive system is divided into 2 groups
• Intrinsic to the reproductive tract
• 1. Ovaries 4. cervix
• 2. Oviducts 5. Vagina
• 3. Uterus 6. Vulva
• Extrinsic to the reproductive tract
• (isolated from the reproductive tract)
• 1. Retina 2. Pineal gland
• 3. Hypothalamus 4. Pituitary gland

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Mare Reproductive Anatomy (ovary)

• Ovary female reprod. glands containing the
  ova or germ cell.
• Located below the 4th and 5th lumbar vertebrae.
• Ovaries are bean shaped in appearance.

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Mare Reproductive Anatomy (ovary)

• The convex side of the ovary is called the bilus.
• It is the area of attachment to the abdominal
  cavity.
• The blood vessels and nerves which serve the
  entire ovary pass though this region.

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Mare Reproductive Anatomy (ovary)

• The concave side of the ovary contains an area
  unique to the mare, the ovulation fossa.
• This wedge-shaped area is the only portion of the
  ovary from which ova may be shed (ovulated).

When a filly is born, the ovarian cortex already
contains a full complement of oocytes (egg
cells).
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Mare Reproductive Anatomy (ovary)

• Of the hundreds of thousands of primordial
  follicles present in the ovary at birth, only a
  small fraction will ever reach maturity and
  liberate their ova (ovulate).
• Most follicles degenerate or undergo partial
  development and then disappear.

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Mare Reproductive Anatomy (ovary)

• Among other functions, the cellular layer of the
  follicles produce the hormone estrogen .
• As the enlarged preovulatory or Graafian follicle
  nears maturity, it bulges from the ovarys
  surface.
• This bulge can be felt through the rectal wall
  via palpation.

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Mare Reproductive Anatomy (ovary)

• Ultrasonic images of the preovulatory follicle
  appear as a black area within the grayish tones
  of surrounding ovarian tissues.
• The follicles diameter indicates its
  maturity.
• Those 35 mm or greater are considered capable of
  ovulating.

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Follicle Growth Pattern
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Mare Reproductive Anatomy (ovary)

• Another cortical structure, the corpus
• luteum forms from the tissue remaining after a
  follicle ruptures at ovulation.
• Unlike the follicle, the corpus luteum is
  solid-cored.
• Secretes the hormone progesterone.

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Mare Reproductive Anatomy (ovary)
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Mare Reproductive Anatomy (oviduct)

• Oviduct are tiny, highly coiled tubes.
• Fallopian tubes
• Site of fertilization
• 3 parts
• Infundibulum
• Ampulla
• Isthmus

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Mare Reproductive Anatomy (oviduct)

• The ovarian end of the oviduct is called the
  infundibulum.
• It is enlarged and shaped like a catchers mitt
  with finger like projections from its end called
  fimbrae.
• Fertilization of the ovum occurs in the ampulla.
• The final portion of the oviduct, where it
  narrows to join the uterus is called the
  isthmus.

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Mare Reproductive Anatomy (uterus)

• Uterus is a multi-layered, hollow, Y-shaped
  organ.
• The ultimate function of the uterus is to
• protect
• nourish
• provide an environment conducive to the
  development of the embryo and fetus
• to expel the fetus during birth

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Mare Reproductive Anatomy (uterus)

• The uterus is suspended within the body cavity by
  two tough, sheet-like structures called the broad
  ligaments.
• Sagging of these ligaments with age, parity or
  trauma can cause a downward tilting of the
  uterus.

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Mare Reproductive Anatomy (uterus)
Horns of Uterus
Uterine-ovarian a.
Uterine a.
Endometrium
Broad ligament
Body of Uterus
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Mare Reproductive Anatomy (uterus)

• This conformation can predispose the mare to the
  backwash of urine into the reproductive tract and
  its accumulation at the cervix.
• Urine pooling can cause uterine infection and
  poor fertility.

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Mare Reproductive Anatomy (uterus)
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Mare Reproductive Anatomy (uterus)

• Maintaining healthy tissues w/in the endometrium
  is crucial for optimal fertility.
• In fact, endometritis (uterine infection) is a
  major cause of infertility in mares.

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Mare Reproductive Anatomy (cervix)

• Cervix highly distensible muscle that acts as a
  barrier between the vagina and the uterus.
• It is approximately 4 inches long and appears as
  a circle of folded tissue at the anterior surface
  of the vaginal vault.

Cervix
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Mare Reproductive Anatomy (cervix)

• In response to increase estrogen production
  during estrus, the cervix appears pink due to
  increased vascularity.
• During this period, it produces an abundance
  of thin, watery mucus and is so relaxed that it
  is often found lying limply on the vaginal
  floor.

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Mare Reproductive Anatomy (cervix)

• The flaccid cervical tone facilitates passage of
  semen or breeding instruments directly into the
  uterus during live cover or artificial breeding.

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Mare Reproductive Anatomy (cervix)

• In contrast, when the cervix is under the
  influence of progesterone during diestrous
  periods and pregnancy, it appears
• blanched,
• produces a thick, sticky mucus,
• tightly closed and held in the center of the
  vaginal wall.

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Mare Reproductive Anatomy (cervix)

• The physical barrier produced by a healthy
  cervix provides a major line of defense against
  uterine contamination and infection.
• Consequently, damage to this structure can result
  in significant problems in maintaining fertility.

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Mare Reproductive Anatomy (vagina)

• Vagina consists of a 6 to 8 -inch long
  muscular, mucus membrane-lined tube which
  communicates the vestibule of the vulva to the
  cervix.

Vagina
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Mare Reproductive Anatomy (vagina)

• The vagina is a passageway between the cervix and
  the external opening of the mares reproductive
  tract.
• The vaginal tissues must be extremely elastic and
  distensible to accommodate the penis in breeding
  and the foal during birth.

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Mare Reproductive Anatomy (vulva)

• Vulva is the exterior opening to the
  reproductive canal.
• Contains the
• Labia
• Clitoris
• Vestibule

Labium
Vulva
Vestibule orifice of vagina
Clitoris
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Mare Reproductive Anatomy (vulva)

• Vulva serves as a protector for the mare.
• The labia are the lips of the vulva.
• In normally conformed mares, approx. 80 of
  the opening in the vulva lies below the pelvic
  floor.

Ilium
Anus
Ischial tuber
Vaginal orifice
Labium
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Mare Reproductive Anatomy (vulva)
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Mare Reproductive Anatomy (vulva)

• This conformational flaw can not be altered.
• However, the vulva can be artificially sealed by
  suturing the labia together, a procedure which is
  known as an episoplasty or caslicks.

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Mare Reproductive Anatomy (vestibule)

• The vestibule is the internal portion of the
  vulva and extends about 4 inches to the interior.
• It is separated from the vagina by a fold of
  tissue which includes the hymen.

Hymen
Vestibule
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Mare Reproductive Anatomy (hymen)

• This fold is located just forward of the urethral
  opening.
• The hymen is often intact in maiden mares, and
  may be so thick that it must be ruptured
  surgically prior to first mating to avoid
  physical and psychological trauma to the mare.

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Mare Reproductive Anatomy (clitoris)

• The clitoris is a small knob-shaped structure
  located inside the labia and on the floor of the
  vulva.
• It can be plainly seen during estrus when the
  mare exhibits eversion of the vulva (winking) and
  following urination.

Clitoris