The oviduct of a hen is the canal through which an egg passes from the ovary to the outside of the hen’s body. It is also sometimes referred to as the egg tube. The oviduct is a long, coiled tube that provides an egg with albumen, membranes, and a shell as it travels through. Understanding the anatomy and physiology of the oviduct is important for egg production in domestic hens.
Anatomy of the Oviduct
The oviduct is divided into five main regions:
- Infundibulum
- Magnum
- Isthmus
- Uterus
- Vagina
Each region plays a specific role in the formation of the egg. The process begins in the ovary, where yolky follicles develop and ovulate approximately 30 minutes before ovulation. After ovulation, the oocyte (immature ovum) enters the infundibulum region of the oviduct.
Infundibulum
The infundibulum is responsible for catching the oocyte after ovulation. It is a funnel-shaped region near the ovary. The infundibulum has finger-like projections called fimbriae that help catch the oocyte after ovulation. Once caught, the oocyte then moves into the magnum region of the oviduct.
Magnum
The magnum is the longest portion of the oviduct at around 50 centimeters in length. Here, the albumen, or egg white, is secreted and layered around the oocyte. The albumen provides nutrition and protection for the developing embryo. Several layers of albumen are deposited as the oocyte travels through the magnum.
Isthmus
In the isthmus region, the inner and outer shell membranes are added. These membranes will later be used to separate the albumen from the shell. The isthmus region is much shorter than the magnum at around 10 centimeters long.
Uterus
The uterus, also called the shell gland, is where the egg shell is formed. Here, calcium carbonate is deposited around the membranes to form a hard protective shell. The shell provides the developing embryo protection from physical damage and prevents bacterial contamination.
Vagina
The vagina is the last portion of the oviduct where muscular contractions will push the completely formed egg out of the hen’s body. It is connected to the cloaca, which is the common opening for the digestive, urinary, and reproductive tracts in birds.
Physiology of Egg Formation
The process of egg formation takes around 25 hours total as it travels through the oviduct. Here is a breakdown of the timing:
Oviduct Region | Duration |
---|---|
Infundibulum | 15 minutes |
Magnum | 3 hours |
Isthmus | 1.5 hours |
Uterus | 20 hours |
Vagina | 30 minutes – 2 hours |
The longest portion of time is spent in the uterus where the shell is formed. The shell requires significant mineralization which is a slow process. However, each region of the oviduct plays an important role in producing a viable egg.
As the egg travels through the oviduct, it rotates to ensure the egg contents remain centered. Muscular contractions help propel the egg forward through each region. Hormones like estrogen, progesterone, and prostaglandins help regulate muscle contractions in the oviduct to coordinate oviposition, or egg laying.
Abnormalities of the Oviduct
There are some abnormalities that can occur in a hen’s oviduct that can impact egg production and quality:
- Tumors – Tumors can develop in any region of the oviduct and lead to obstruction that blocks the passage of eggs.
- Infection – Bacterial infections like E. coli or Mycoplasma can cause inflammation and lesions in the oviduct.
- Prolapse – Portions of the oviduct can prolapse or fall out of the cloacal opening.
- Egg binding – An egg can get stuck or “bound” in the oviduct, preventing its normal passage.
- Cysts – Fluid-filled cysts can form in the oviduct, disrupting normal function.
Any of these conditions can impact the number and quality of eggs produced. Catching and addressing oviduct issues early is important to optimize hen health and productivity.
Conclusion
The oviduct is a complex organ essential for egg production in hens. It consists of five main regions – the infundibulum, magnum, isthmus, uterus, and vagina. As the egg travels approximately 25 hours through the oviduct, each region deposits important components like albumen, membranes, and shell. Muscular contractions and hormones regulate the movement of the egg through the oviduct. Abnormalities like tumors, infections, prolapse, egg binding, or cysts can have detrimental impacts on egg yield and quality. Understanding the anatomy and physiology of the oviduct gives great insight into the incredible process of egg development in hens.