Structure and Function of the Female Canine Reproductive Tract
What Is the Female Canine Reproductive Tract?
The female canine reproductive tract consists of the female genital organs including the ovaries, uterus, vagina, vulva, and mammary glands.
Where Is the Female Canine Reproductive Tract Located?
The reproductive organs are located in the abdomen, and the mammary glands are located in two rows along the outside of the abdomen, running from the groin to the chest. The right and left ovaries are located just behind the kidneys. The ovaries are connected to the uterus by small ducts called oviducts. The uterus extends from the area behind the ovary to the back of the abdomen just in front of the pelvis. The uterus terminates at the cervix, which separates the uterus from the vagina. The vagina passes through the pelvis to the vulva, which is the external opening of the genital passage.
What Is the General Structure of the Canine Female Reproductive Tract?
Ovaries are suspended from the top of the abdomen by a broad ligament called the suspensory ligament. Oviducts are small tubes that extend from the ovaries to the uterine horns. At the end of the oviduct nearest the ovary a funnel-like structure, the infundibulum, catches the egg (ovum) when it is released from the ovary.
The uterus of the dog is Y-shaped, with the arms of the "Y" being longer than the stem. The long arms of the uterus are called the horns, and the short stem is called the body. The uterine horns extend from each ovary and join to form the body of the uterus. When the female is pregnant, the fetuses are arranged in a row in both horns. The very tip or base of the Y is the cervix.
The walls of the uterus are lined with a vascular and glandular lining (mucosa) and contain smooth muscle. The muscular substance of the uterus is called the myometrium; the inner lining is called the endometrium.
The cervix contains connective tissue and muscle that form a firm tube-like sphincter. The cervix is usually closed to prevent infection. During fertilization and birth the sphincter of the cervix is relaxed or opened.
The vagina of the bitch is very long and passes through the pelvis toward the vulva. In a 25-pound dog, the vagina averages 12 cm long and 1.5 cm in diameter. Both the length and diameter increase considerably during pregnancy and birth.
The vaginal walls are made up of an inner mucosal layer, a middle smooth muscle layer, and an external coat of connective tissue. The vaginal mucosa contains numerous folds, which allows for great expansion and stretching.
Mammary glands are composed of connective tissue to provide support and structure, blood vessels, lymphatic vessels and glandular tissue. Mammary glands contain small saclike glands that secrete and store milk. Milk eventually travels through a duct system to empty into the teat. The dog usually has five pairs of mammary glands.
What Are the Functions of the Female Reproductive Tract?
The ovaries contain the eggs (ova) that are waiting to be fertilized. The ovaries also produce the female hormones of estrogen and progesterone. The eggs are released from small saclike structures called follicles during the process of ovulation and pass through the fallopian tubes into the uterus. When a bitch is spayed, the ovaries, oviducts, and uterus are removed.
The primary function of the uterus is reproduction. It serves as the site for implantation of fertilized ova (eggs) and for the growth and development of the fetus. The uterus houses the fetus until it is ready to be delivered.
The vagina provides a passage way from the outside of the body to the uterus. During breeding, sperm is deposited in the vagina by the male dog. The vagina provides a protected passage for fetuses to move from the uterus to the outside and also protects the opening of the urethra (where urine leaves the body).
The vulva protects the opening of the vagina and provides external markings that identify the animal as a female. The function of the mammary glands is to produce milk for any offspring.