Introduction:
As oocytes grow and develop in the ovaries, the yolk substance gradually accumulates in the egg. The yolk material is layered in concentric circles, forming a dark yolk (yellow yolk) and light yolk (white yolk) arranged in a yolk structure, from which the white yolk forms the yolk heart, which extends to the animal pole, the end is slightly expanded, and the expansion is called the Pane's nucleus.
White yolk contains more protein, and yellow yolk is rich in lipid substances. There is very little cytoplasm in the egg, mainly in an area on top of the animal's polar yolk, where the nucleus is located.
As the yolk material increases within the oocytes, the volume becomes larger and the follicles protrude from the surface of the ovaries. At ovulation, the primary oocytes complete their first mature division and expel the first polar body, becoming subpolar oocytes. This then entered the middle phase of the second meiosis. During ovulation, the follicular membrane ruptures and secondary oocytes are released from the ovaries and are immediately swept up by the very mobile fallopian tube umbrella.
Stay at the umbrella for about 15 minutes, where the fertilization process is completed and the second polar body is expelled if it meets the sperm.
The fallopian tube must be divided into 5 parts:
Umbrella, protein secretion (ampulla), isthmus, uterus, and vagina. It takes about 24 hours for a chicken to produce a complete egg. The umbrella is funnel-shaped with thin edges that form folds. Egg cells stay here for 15-18 minutes and complete fertilization. The protein secretion part has a thick wall, the mucosa forms longitudinal folds, and there are glands secreting concentrated protein wrapped around the yolk, and the egg rotates downward to form a frenulum (egg band) twisted by concentrated protein at both ends. Chicken egg cells stay here for 3 hours. The lumen of the isthmus is narrow, and glandular cell secretions form an inner shell. The eggs stay here for 75 minutes.
The whole process:
The uterus is large part of the fallopian tubes, the mucous membrane forms deep folds, and the muscle layer is developed. This is where the egg cells absorb water to form dilute proteins, and the shell glands secrete calcium-containing compounds to form the egg shell. 4-5 hours before egg laying, uterine wall pigment cells secrete pigment and apply pigment to the surface of the shell, forming various stains. Eggs stay here for 18-20h. The vagina is the end of the fallopian tube, with an opening to the left of the cloaca. After the egg leaves the uterus and enters the cloaca, a strong contraction of the muscles of the cloaca wall allows it to be excreted.
At this point, the egg always moves forward with the thinner end, but half an hour before it is produced, it will turn sharply, so when laying eggs, the egg is laid first at the thicker end.
The early development process of fertilized chicken eggs
Chickens are oviparous animals in which embryos develop. After fertilization, zygotes undergo 24~27 hours of development in the fallopian tubes.
Double yellow eggs
Over such a long period of time, zygotes have developed to the blastocyst stage or even the early gastrulation stage. At this time, a slightly larger white disc called the placenta is visible on the yolk, which contains hundreds of cells, so the egg is no longer a cell.
If the laying hen does not accept mating with a rooster, the eggs laid by her eggs stay in the middle of the second meiotic division, so that each such egg (strictly speaking the yolk) can be seen as a large cell.
The placenta is always up
The egg cell suspended by the frenulum is, like a tumbler, due to the gravity of the yolk granule, its center of gravity is always in the lower half, so that regardless of the position of the egg, the placenta is always facing up, that is, towards the warm body of the hen, favoring the acceptance of the parent bird to hatch the eggs.
The air chamber is at the blunt end of the egg
One end of the egg is blunt and the other is slightly pointed. The presence of a blunt-ended air chamber shifts the center of gravity of the egg to the small head. Due to the shape and center of gravity, when the egg is flat, the yolk always tends to the pointed end, and if it rolls, it will roll in a circle without rolling far, and when rolling, it is always large and out, and if there is a small damage, it will not affect the whole egg. If the air chamber is not at the blunt end, the egg becomes a "tumbler", which is not conducive to the protection and hatching of the embryo.
There is an air chamber at the blunt end, and when the chick is about to hatch, its head tends to face here, and then it uses its mouth to penetrate the air chamber to breathe the air in the air chamber directly.
The shape of the egg is closely related to the shape of the chick in the egg. The tip of the egg is the support point of the chicken's two feet, playing a strong supporting role, so the eggshell that is initially pecked open tends to be blunt.
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