Understanding the Reproductive System of Hens: One Ovary, One Oviduct, and Continuous Egg Production

5. Only one ovary and one oviduct develop and become functional in the mature female hen.

In the mature female hen, unlike mammals, only one ovary and one oviduct develop and become functional

In the mature female hen, unlike mammals, only one ovary and one oviduct develop and become functional. This is due to the unique reproductive system of birds.

The ovary in a hen is situated high up in the abdominal cavity near the spine. It is responsible for producing, maturing, and releasing eggs. While female mammals typically have two ovaries, in hens, only the left ovary develops fully. The right ovary typically regresses and is non-functional.

The mature ovary of a hen is composed of thousands of tiny follicles, each containing an immature egg called an ovum. These follicles go through a continual process of development, with one or a few follicles growing and maturing at a time. The yolk, which provides nutrients for the developing embryo, is produced and stored within the growing follicles.

When a hen reaches sexual maturity, the ovary releases a mature egg into the oviduct. The oviduct is a long and convoluted tube that spans the length of the hen’s abdominal cavity. It consists of five different regions: the infundibulum, magnum, isthmus, uterus or shell gland, and the vaginal opening.

The egg’s journey through the oviduct begins in the infundibulum, where fertilization can occur if the hen has mated with a rooster. From there, the egg passes through the magnum, where the albumen or egg white is secreted and forms around the yolk. The egg then moves into the isthmus, where the two shell membranes are added to provide protection.

Next, the egg enters the uterus, also known as the shell gland. In this region, the hard outer shell is formed thanks to the deposition of calcium carbonate. The uterus is also responsible for adding pigmentation to the eggshell, which gives it its characteristic color.

Finally, the fully formed egg reaches the vaginal opening, also called the cloaca, where it is laid. The process from the release of the egg from the ovary to the laying typically takes about 24 to 26 hours.

It is important to note that hens do not have a menstrual cycle or a monthly shedding of the uterine lining as observed in humans and some mammals. Instead, they produce eggs continuously throughout their reproductive lifespan, with the potential for short breaks in egg production.

In summary, the mature female hen has only one functional ovary that produces eggs. The ovulated eggs travel through the oviduct, where they undergo different stages of development, including fertilization (if mating has occurred), albumen formation, membrane deposition, shell formation, and ultimately, laying through the vaginal opening.

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