"Estrogen is involved in a feedback mechanism associated with the follicular phase of menstruation.<span> In a negative feedback mechanism, estrogen released from follicles influences the pituitary gland to decrease the production of follicle stimulating hormone, also known as FSH. In a positive feedback mechanism, rising estrogen causes FSH to increase"
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Following fertilization, the single-celled zygote undergoes cleavage, where it is then divided into numerous tiny cells. After 3 to 4 days of fertilization, the cleavage produces a 16 celled embryonic stage known as morula, which is contained within the zona pellucida.
After about 4-5 days of fertilization, cleavage produces a sphere mass of cells known as blastomeres, which is covered by a layer known as trophoblast and has a fluid-filled cavity in the center, known as blastocoel. The blastomeres then migrate inward, changing position and undergoing rearrangements. This is known as gastrulation.
Gastrulation then causes the development of three germ layers: ectoderma, endoderma, and mesoderma. The interaction of cells and the rearrangement of tissues and organs occurs only after the formation of germ layers.
Answer:
Simple squamous epithelium,stratified squamous epithelium,pseudostratified columnar epithelium
Explanation:
The respiratory system is made up of many different types of tissues and they differ according to their locations in the respiratory system.
1.Simple squamous epithelium: It is found within the alveoles of the lungs. These cells are single layer,flat (squamous) cells. It controls the permeability of blood vessels in the lungs. When you inhale it allows more oxygen to be absorbed in the blood flows.
2.stratified squamous epithelium: It is found at mouth surface primarily tongue and throat . These cells are stratified that is they are many layered because everyday whatever we put in our mouth and throat it protects from wear and tear. It gives physical protection from pathogens as well.
3.pseudostratified columnar epithelium: It is a lining of the nasal cavity trachea and bronchi. This layer is ciliary to trap patheogen on entering into the lungs.
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