Equine Reproduction Flashcards
what is the female germ cell called?
ovum
where is the ovum produced and nurtured?
in the ovary
what does it mean when an ovum is ovulated?
it is released into the oviduct
how long does the ovum remain in the oviduct? where does it go after this?
until fertilization occurs; then passes into the uterus
where does the fetus develop?
in the uterus until parturition
upon parturition, describe the route the fetus takes (5)
through the cervix, vagina, vestibule, and vulva to the exterior of the mare and a hopefully healthy foal is born
what shape and size is the ovary?
kidney bean shapes; generally 60-80mm (3in) length, 25-40mm (1.5 in) wide, and 20-30mm (1 in) tall
where is the mare ovary usually in a nonpregnant mare?
generally located between the last rib and the tuber coxae
what is the tuber coxae?
the point of the hip
where is the ovary found in pregnant mares?
pulled down deeper into the abdomen due to weight of the enlarging uterine contents; pulls down further as pregnancy progresses
what 3 things affect the position of the ovary in mares?
- age of mare
- parity number (number of foals the mare has had)
- contents of the GI tract (more fiber shifts the tract around)
what fixes the repro tract to the body wall?
the broad ligaments
generally describe the broad ligaments
layers of serous membranes of the peritoneum that originate from the sub-lumbar region (3-4 LV to 4SV)
what is the physical role of the broad ligaments?
hold ovary, uterus, and oviduct in place and position/support them
what is the functional role of the brtoad ligaments?
corridors for blood vessels, lympahtic vessels, and nerves
what are the 3 parts to the broad ligament? describe what they support
- mesovarium: supports ovaries
- mesometrium: supports uterus
- mesosalpinx: supports oviducts
what 4 structures are associated with an active ovary?
- follicles
- corpus hemorrhagicum
- corpus luteum
- corpus albicans
what is a follicle?
a fluid filled blister that develops on the surface of the ovary
what are the 2 purposes of the follicle?
- to protect and maintain the growing ovum
- to produce the excitatory hormone estrogen
what does estrogen do?
causes the mare to exhibit signs of estrus
what is the main difference between a horse and a humna ovary?
in humans, the cortex is on the outside and the medulla is on the inside, but in mares, the cortext is on the inside! and the medulla is on the outside
what happens to the follicle as it matures?
the follicle increases in size until it softens and finally ruptures, releasing the ovum (ovulation)
where does ovulation occur in a mare?
in a specialzed area of the ovary called the ovulation fossa
describe the average size of the ovary when ovulation occurs
between 40-45mm, but can be up to 51mm
once the ovum is released, what happens to it?
it is picked up by the fibriae of the infundibulum of the oviduct
what forms are the point of rupture as the follicle collapses during ovulation?
a small hemorrhage called the corpus hemorrhagicum
can you plapate the corpus hemorrhagicum? does it stick around for long?
no; it is difficult to palpate and short-lived for only 2-3 days
what does the corpus hemorrhagicum become after 2-3 days?
the corpus luteum
what is the corpus luteum? what does it do?
yellow body; produced progesterone
what does progesterone released by the corpus luteum do? (2)
- inhibits or stops the mare’s estrus behavior
- acts to maintain pregnancy
how long is progesterone produced from the corpus luteum if the mare is not pregnant? what happens to the CL after this amount of time if not pregnant?
corpus luteum will produce progesterone for about 12 days, then regress if the mare is not pregnant
if a mare is pregnant, how long will the CL be maintained and then what will happen to it?
CL will be maintained for approx 180 days before regression
since the CL is only maintained for approx 180 days of pregnancy, and a mare is pregnant for approx 340 days, what takes over to produce progesterone after the CL regresses?
the placenta
what happens as the CL regresses? (3)
- it is invaded by connective tissue that appears as white areas on the ovaries at the site of the CL
- the remaining scar is known as the corpus albicansm which serves no known function and disppears in approximately 6 months
if a mare is not producing enough of her own progesterone, what can be given? what are the drawbacks with this?
can give regumate, a synthetic progesterone, but it is expensive and must be handled incredibly carefully, especially by women, as it can absorb through the skin and mess with human cycling
why would a mare who must be given regumate to maintain her pregnancy continue to be bred?
if she has great genetics
what is the oviduct called in humans?
fallopian tube
in mares where is the oviduct located?
extends from the ovulation ofssa of ovary to the uterus