reproduction

Reproduction

Anastasia Kellogg

The Reproductive System of the Mare

• The mare’s reproductive organs are supported by the broad ligament

• The main organs of the female reproductive system are the ovaries, oviducts, and uterus

• The ovaries are the gonads of the female animal, and there are two of them in each animal

• The two main functions of the ovary are the production of eggs (ova) and hormones


• Each ovary is kidney shaped, with a length two inches and a width of an inch and a half

• Developing ovum are surrounded by follicles• When the follicle bursts, ovulation occurs• Ovulation refers to the release of the egg by the

ovary• Oviducts carry the egg from the ovary to the

uterus, and are the sight of fertilization if it is to occur


• The oviduct is 8-12 inches long• The oviduct may also be called the fallopian tube• The uterus, or womb, is where the unborn fetus

grows• The uterus may be divided into the uterine body,

the right horn, and the left horn• The three layers of the uterine wall are the serous

membrane, the myometrium, and the endometrium


• The uterus and birth canal join at the cervix• An ovum=an egg, the plural is ova• Fertilization refers to the union of the egg and

sperm• The period between fertilization and parturition is

called gestation• In the mare gestation lasts about 340 days• Gestation lasts longer in the jenny (female

donkey)


• Immediately after fertilization, the offspring is known as a zygote

• After 6-8 days, the zygote implants itself on the uterine wall, in either the right or left horn, and it is an embryo; after the first trimester it is called a fetus

• Parturition=birth• The placenta is the structure which surrounds the

unborn fetus, through which nutrients and oxygen are passed from the dam (mother)


• The three layers of the placenta are the allantois, amnion, and chorion

• After birth the mare nourishes her foal with milk• The mammary glands of the mare are found in the

udder• Lactation means the production of milk• Colostrum is the antibody rich first milk of the

mare, which provides passive immunity to the foal


• Mastitis is a swelling of the udder

The Reproductive System of the Stallion

• The testicles, or testes are the gonads of the male animal, and are the primary organs of the stallion’s reproductive tract

• The testes produce hormones and sperm cells• Sperm cells, or spermatozoa, are the male sex cells• In the male fetus, the testes are located on the

upper abdominal wall


• Soon after birth, the testes drop down through the inguinal ring and into the scrotum

• If only one teste drops into the scrotum, and the other is permanently retained, the horse is referred to as a cryptorchid

• The normal adult stallion has two testes located in the scrotum


• The testes are suspended from the abdomen by the spermatic cord, which also contains nerves and blood vessels

• The blood vessels in the spermatic cord are arranged so that the blood is cooled before it reaches the testes, since heat inhibits sperm production

• The muscles in the spermatic cord and scrotum control testicular temperature by positioning the testes close to the body in cold weather and farther away when they are warm


• The muscles within the spermatic cord are called the cremaster muscles

• The muscles within the scrotum are called the tunica dartos muscles

• The tissue which separates the two testes is the septum scroti

• Each teste is surrounded by a fibrous capsule called the tunica albuginea


• Each teste is divided into several lobules called lobuli testis

• Within each lobuli testis are the seminiferous tubules, which contain the primary germ cells, which are eventually to become viable spermatozoa


• Sperm production (spermatogenesis):– The change from germ cell to spermatid (immature

sperm cell) lasts about 60 days– Begins in the seminiferous tubules, where germ cells

reproduce by meiosis, or sex cell division– An immature spermatid migrates from the seminferous

tubules to the epididymis– As the spermatid migrates it gains maturity, losing

cytoplasm and gaining a tail, or flagellum– Final maturation occurs within the epididymis


• The epididymis is a long, U-shaped structure attached to the top (long axis) of each teste

• While in the epididymis, sperm are nourished by the fluid around them, and chemicals prevent them from moving their flagellum while they mature, thus enforcing energy conservation

• The vas deferens, or ductus deferens, is the duct which carries mature sperm from the epididymus to the urethra


• The accessory sex glands secrete seminal fluid into the vas deferens, forming semen

• The accessory sex glands of the stallion are the seminal vesticles, the ampulla, and the prostrate gland

• The seminal vesticles, or vesicular glands, secrete a large portion of acidic seminal fluid, which contains high levels of protein and potassium


• The ampulla is the the enlarged glandular portion of the vas deferens, and secretes a large amount of fluid very similar to that of the seminal vesticles

• The prostrate gland produces alkaline fluid that contains proteins, compounds that break up proteins, citric acid, and zinc

• The bulbourethral glands produce a clear fluid that flushes the urethra of urine and bacteria before ejaculation


• Semen, carrying sperm, exits the body through the urethra

• Ejaculation is the forcing of semen from the body• The urethra is found within the penis• The male copulatory organ is the penis, which rests in

the sheath, or prepuce• The path of a sperm cell:

– From the seminiferous tubules (within the testes)– To the epididymis– To the vas deferens– To the urethra and out of the body


• Geldings are not capable of reproduction

reproduction

Health & Medicine

female reproductive

mare gestation

mare mastitis

mares reproductive organs

stallions reproductive

male fetus

sperm cells sperm cells

fetus parturition