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Embryology Review

Terms

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Differentiation
Specialization of cells that occurs during development
Morula
Solid Ball of embryonic cells
Blastulation
When the morula (solid ball of cells) develops a fluid-filled cavity called the blastocoel
Blastocoel
Fluid-filled cavity developed from a morula (solid call of cells) during blastrulation
Blastua
Hallow sphere of cells following formation of the blastocoel. Also called the blastocyst. Containes two groups of cells: inner cell mass and trophoblast
inner cell mass
1 of 2 groups of cells in a blastocyst. Protrudes into the blastocyst.
trophoblast
1 of 2 groups of cells in a blastocyst. Surrounds the blastocyst and later gives rise to the chorion
implantation
Embryo implants in uterine wall during blastulation. Progesterone prepares for this process by causing glandular proliferation of the endometrium.
gastrulation
After implantation, cell migration transforms the single cell layer of the blastula into three-layered structure called the gastrul
gastrula
Three layered structure blastula
deuterostome
blastopore becomes the anus
protostome
blastopore becomes the mouth
blastopore
Opening of the archenteron (gut)
ectoderm
1) integument (epidermis, hair, nails, and epithelium of nose, mouth, and anal canal)
2) lens of the eye
3) nervous system
endoderm
1) eptithelial linings of digestive tract and prespiratory tract
2) parts of liver, pancrease, thyroid, and bladder
mesoderm
1) musculoskeletal system
2) circulatory system
3) excretory system
4) gonads, connective tissue throughout body, portions of digestive and respiratory organs
induction
influence of a specific group of cells (organizer) on the Differentiation of another group of cells. Mediated by cehmical substances (inducers) passed from the organizer to adjacent cells.
notochord
Made of mesodermal cells. Develop into nervous system.
neural tube
gives rise to the brain and spinal cord (CNS)
neural crest
Cells at the tip of each neural fold that migrate laterally and give rise to many components of peripheral nervous system (PNS)
chorionic villi
Extend into the uterine wall and become closely associated with endometrial cells, developing into the spongy tissue of the placenta
placenta
Site of nutrition, respiration, and waste disposal for the fetus
Fetal hemoglobin
Has a greater affinity for oxygen than adult hemoglobin, tus oxygen preferentially diffuses into fetal blood, metabolic wasters and CO2 diffuse in the opposite direction-- from fetal blood into maternal blood
Circulatory system between mother and fetus
Maternal and fetal blood do not mix. All exchange of material between maternal and fetal blood vessels occurs in the placenta via diffusion.
Immunological protection of placenta
The placenta offers the fetus some immunological protection by PREVENTING the diffusion of foreign matter into fetal blood
Permeability of placenta
Placenta is permeable to viruses, alcohol, and drugs and toxins, but not bacteria.
Placenta as an endocrine glad
Functions as an endocrin gpland, producing hormones progesterone, estrogen, and human chorionic gonadotropin essential for maintaining pregnancy.
Pregnancy tests
human chorionic gonadotropin (HCG) in urine is the simplest test for pregnancy
Fetal circution differs from adult circulation
1) Blood is oxygenated in the placenta (fetal lungs are nonfunctional)
2) Fetal circulatory route contains 4 shunts that divert blood away from fetal liver and lungs (umbilical vein, dectus venosus, foramen ovale, ductus arteriosus)
umbilical vein
carries oxygenated blood from placenta to the fetus
ductus venosus
By which the blood bypasses the fetal liver before convergining with the inferrior vena cava
Blood mixing in fetus
deoxygenated blood from lungs mixes with the partially oxygenated blood that crossed over from the right atrium via the foramen ovale before being pumped into the systemic circulation by the left ventricle
foramen ovale
A shunt that diverts blood away from the pulmonary arteries where blood bypasses the pulmonary circulation and enters the left atrium directly from the right atrium.
ductus arteriosus
Remaining blood in right atrium empties into the right ventricle and is pumped into the pulmonary artery and most of this blood is shunted directly from the pulmonary artery to the aorta diverting even more blood away from lungs
Fetus blood in pulmonary arteries
Carries partially oxygenated blood to lungs
Fetal lungs
non functional during development. a small amount of partially deoxygenated blood goes to the fetal lungs to unload further oxygen into the developing lungs. Deoxygenated blood then returns to left atrium via pulmonary veins.
umbilical arteris
Retunrs deoxygenated blood from the fetus to the placenta
At birth, forman ovale to closes
Increased left atrial pressure coupled with decreased right atrial pressure causes foramen ovale to close
First trimester of gestation (pregnancy)
Major organs begin to develop
Second trimester of gestation (pregnancy)
Face appears human, toes and fingers elongate
Third trimester of gestation (pregnancy)
Antibodies are transported by highly selective ACTIVE transport from mother to fetus for protection against foreign matter.

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