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In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages. [2] [4] The main stages of animal embryonic development are as follows: The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula.
In animals, fertilization begins the process of embryonic development with the creation of a zygote, a single cell resulting from the fusion of gametes (e.g. egg and sperm). [5] The development of a zygote into a multicellular embryo proceeds through a series of recognizable stages, often divided into cleavage, blastula, gastrulation, and ...
The first trimester is from the last menstrual period through the 13th week, the second trimester is 14th–28/29th week, and the third trimester is 29/30th–42nd week. [6] Birth normally occurs at a gestational age of about 40 weeks, though it is common for births to occur from 37 to 42 weeks. [ 6 ]
2-Month-Old Puppy Development. When puppies are around the age of 8 to 12 weeks, there is a lot going on from a developmental standpoint. During this period, puppies are in the prime time of the ...
Pyometra is a result of hormonal and structural changes in the uterus lining. This can happen at any age, regardless of how many heat cycles have occurred or previous pregnancies (or lack thereof), although it becomes more common as the dog gets older. The main risk period for a female is for eight weeks after her peak standing heat has ended. [2]
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus , and ends once it leaves the uterus.
Due to the fact that placental mammals and marsupials nourish their developing embryos via the placenta, the ovum in these species does not contain significant amounts of yolk, and the yolk sac in the embryo is relatively small in size, in comparison with both the size of the embryo itself and the size of yolk sac in embryos of comparable developmental age from lower chordates.
A Reddit user shared a photo of an pregnant dog's X-ray and you can clearly see all her babies: Pregnant dog x-ray from pics The photo became incredibly popular, garnering thousands of comments.