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Fetal growth and developement


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During the 3rd week after conception, the embryonic disk differentiates into 3
primary germ layers:
each germ layer of primary tissue develops into distinctive
body systems.
why is it helpful to know which structures rise from each germ layer?
because coexisting defects found in newborns usually arise from the same layer.
what are some examples of coexisting defects found in newborns arising from the same layer?
tracheoesophageal fistula (both organs arise from the endoderm)
heart and kidney defects (both arise from the mesoderm)
why is rubella especially serious in pregnancy?
It is capable of affecting all the germ layers and thereby causing congenital anomalies in a myriad of body systems, irrespective of their origin.
knowing the origins of body structures helps you to understand why certain screening malformations. What is an example?
a kidney x-ray examination may be ordered for a child born with a heart defect.
list the major body systems that are formed from the mesoderm primary tissue layer.
Wall of digestive tract, kidneys and ureter, dermis, reproductive organs - gonads, genital ducts, connective tissue - cartilage, bones, spleen, CV system - heart, arteries, veins, blood, bone marrow, skeleton, muscles, pleura, lymphatic.
list the major body systems that are formed from the endoderm primary tissue layer.
respiratory tract epithelium, epithelium including pharynx, tongue, tonsils, thyroid, parathyroid, thymus, tympanic cavity, lining of digestive tract, urethra and associated glands, primary tissue of liver and pancreas, vagina, mucous membranes of anus and mouth.
list the major body systems that are formed from the ectoderm primary tissue layer.
sweat glands, sebaceous glands, epidermis, nails, hair follicles, eyes lens, sensory epithelium of internal and external ear, nasal cavity, sinuses, mouth, anal canal, CNS, PNS, nasal cavity, oral glands, tooth enamel, pituitary gland, mammary gland, nervous system
What is the purpose of the yolk sac?
Help with transferring maternal nutrients and oxygen to manufacture blood cells and plasma dudring weeks 2 and 3.
The placenta functions as a means of __________ exchange.
The placenta is complete by what week?
12th week
The placenta continues to grow wider until ______weeks
At 20 weeks the placenta overs about _______ of the uterine surface.

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