The cells surrounding the blastocyst now destroy cells in the uterine lining, forming small pools of blood, which in turn stimulate the production of capillaries. This is the first stage in the growth of the placenta.
The inner cell mass of the blastocyst divides rapidly, forming two layers. The top layer becomes the embryo, and cells from there occupy the amniotic cavity.
At the same time, the bottom layer forms a small sac if the cells begin developing in an abnormal position, an ectopic gestation may also occur at this point. Several days later, chorionic villi in the forming placenta anchor the implantation site to the uterus. A system of blood and blood vessels now develops at the point of the newly forming placenta, growing near the implantation site.
The small sac inside the blastocyst begins producing red blood cells. For the next 24 hours, connective tissue develops between the developing placenta and the growing embryo. This later develops into the umbilical cord. Following this, a narrow line of cells appears on the surface on the embryo.
Its growth makes the embryo undergo gastrulation , in which the three primary tissue layers of the fetus, the ectoderm , mesoderm , and endoderm , develop.
The narrow line of cells begin to form the endoderm and mesoderm. The ectoderm begins to grow rapidly as a result of chemicals being produced by the mesoderm. These three layers give rise to all the various types of tissue in the body.
The endoderm later forms the lining of the tongue , digestive tract , lungs , bladder and several glands. The mesoderm forms muscle , bone , and lymph tissue, as well as the interior of the lungs, heart , and reproductive and excretory systems. It also gives rise to the spleen , and produces blood cells.
The ectoderm forms the skin , nails , hair , cornea , lining of the internal and external ear , nose , sinuses , mouth , anus , teeth , pituitary gland , mammary glands , eyes , and all parts of the nervous system.
Approximately 18 days after fertilization, the embryo has divided to form much of the tissue it will need. It is shaped like a pear, where the head region is larger than the tail. The embryo's nervous system is one of the first organic systems to grow.
It begins growing in a concave area known as the neural groove. The blood system continues to grow networks which allow the blood to flow around the embryo. Blood cells are already being produced and are flowing through these developing networks. Secondary blood vessels also begin to develop around the placenta, to supply it with more nutrients.
Blood cells begin to form on the sac in the center of the embryo, as well as cells which begin to differentiate into blood vessels. Endocardial cells begin to form the myocardium. At about 24 days past fertilization, there is a primitive S-shaped tubule heart which begins beating.
The flow of fluids throughout the embryo begins at this stage. For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth.
For most species, the amount a fetus grows before birth determines the length of the gestation period. Smaller species normally have a shorter gestation period than larger animals.
Species that use a breeding season usually give birth during a specific time of year when food is available. Various other factors can come into play in determining the duration of gestation.
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Elephants have the longest gestation period of all mammals, carrying their young for nearly two years before giving birth. Long developmental periods are common among highly intelligent animals.
Both African and Asian elephants have a pregnancy that approaches two years—22 months, to be exact. This is the longest gestation period for any land animal, and one —of the longest for any animal on earth. Elephants produce one baby at a time, and the youngster weighs around kilograms ( pounds) at .
Nov 01, · Gestation Period For Elephants. An elephant's gestation period is 22 months which is the longest of any mammal. Some sharks are thought to have longer pregnancies, the frilled shark is thought to be pregnant from 3 to 4 years but it has not been bophona.ml: Resolved. Elephants have the longest gestation period of all mammals. These gentle giants' pregnancies last for more than a year and a half. The average gestation period of an elephant is about to days, or roughly 95 weeks. By comparison, a human pregnancy lasts an average of days, or 40 weeks.
No. Elephants elephants pregnancy term are large mammals of the family qualities research good paper Elephantidae and the order Proboscidea. Asian elephant populations in Laos, which. Jun 19, · Elephant pregnancy lasts for 22 months. At up to days (average days), elephants have the longest gestation period on earth. New research, published in .