Fun Fact Friday - Which Came First?

Yes, kids, it's time we had that 'little talk'. When we were in the Poultry and Rabbit building at the fair, there was an entire wall of educationalish FFA artwork. Some of this revolved around the reproductive process of chickens.
Yeah. Lori and I just didn't get it, exactly. There were lots of snaky tubes, and pipe cleaners glued to cardboard, and it just wasn't making much sense.

And remember, if I find something disturbingly intriguing, you're ALL going to learn about it. And there are some things you can't un-learn, so it's not like doing a somersault or riding a bike. Turn back now if knowing this means you'll never be able to eat eggs again. I will not bear the responsibility for this, nor will I abide another toe. If you don't think you can handle it, go check out this post instead.

But really, how do chickens 'do it'? It sounds like a bad Mister Wizard question from my youth.
Like other reproductive systems, it starts with ovaries. However, chickens, while born with two, develop a 'dominant' ovary. This is the one that starts all the egg-laying. In fact, several of the chickens at the fair had eggs in their cages. That's one of those things that just happens, and if memory serves, it happens about 5.5 times a week. This egg-laying cycle is referred to as a 'clutch'. Chickens run on some weird internal clock, that allows them to produce an egg in just over a day, but once it gets to be 3 pm, no eggs. This ends the cycle, creates a break of a day, and then the hen starts laying again, creating a new clutch.

I don't know if Daylight Savings Time factors into this at all.Hens have about two years of productive laying time in their lives, after which they become soup fodder. Egg formation itself starts when the ovary produces the yolk, with its runny, yolky center, a single cell. The outer membranes and layers get added as the egg passes through the chicken, from the infundibulum (or 'the funnelly bit'), and then through the magnum (or 'the Sellecky bit'). The Sellecky bit is responsible for the secretion of the albumen, or egg white, and on a good day, can encompass two yolks at a time. Magnum, indeed!
Then we move on into the isthmus ('the membrane-y bit') and into the shell gland. What? I didn't figure that one needed a scientific renaming.
Then, and only then, does the egg pass into the vagina. I can't type the word without hearing Phil Hartman as Charlton Heston. However, avian vaginas differ from their mammalian counterpart in this area. Between the shell gland and vagina, chickens (and other birds) have sperm host glands. Hens can maintain a rooster's sperm at body temperature, allowing it to remain viable for up to two weeks inside the vagina. Each time an egg squeezes through the shell gland into the vagina, sperm is expressed back into the earlier stages of egg development, each egg fertilizing its next sibling. Except for the first egg, I guess.

So how does the sperm get there?Sweet, sweet, chicken lovin', that's how. When chickens mate, the rooster presses his 'sexual opening' ('the penis-y bit') against that of the female by mounting her, flapping his wings and biting the hen's neck to maintain his balance. The male's sperm enters the female's sexual opening (cloaca) during this time. After entering the cloaca of the female, the sperm, containing the male's genetic information, travels up the oviduct to the sperm host glands where it awaits the next egg.

Don't you feel better for knowing this? I know I do. Omelet, anyone?

A special thank you to Dr. Thomas Caceci, without whose graphic depiction of the avian reproductive system today's fun facts would not have been possible.