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33 Cards in this Set
- Front
- Back
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Describe the cleavage process that takes place after ovum fertilization.
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Rapid mitotic divisions which lead to increase in cell number but not protoplasm, increasing SA:V ration to increase gas and nutrient exchange
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What is the difference between indeterminate and determinate cleavage?
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Indet: results in cells that maintain ability to develop into complete organism
Det: results in cells with defined differentiation PW |
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What is a morula?
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Ball of cells resulting from cleavage
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What is blastulation? What does it give rise to?
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When morula begins to fill with fluid; becomes hollow sphere known as Blastula (BLASTOCYST in mammals)
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What is a blastocoel?
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Fluid-filled cavity within morula undergoing blastulation
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What are trophoblasts?
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Outer cell layer of blastocyst
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When does implantation occur?
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During blastulation
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What hormone is responsible for preparing the endometrium for implantation?
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Progesterone
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What is an ectopic pregnancy?
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When blastula implants itslef outside of uterus (most frequently in fallopian tube)
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What is gastrulation?
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Formation of 3-layered gastrula from blastula implantation
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Draw and label the major structures of a gastrula.
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Looks like a bubble-letter C
Space within C outline = mesoderm Outline of C = Ectoderm Gap between start and finish of C = blastopore Exact middle of c = endoderm |
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What is the difference between deuterostomes and protostomes? Which class of organism do humans belong to?
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Deuterostomes: blastopore becomes anus
Protostomes: blastopore becomes mouth Humans are deuterostomes |
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What does the ectoderm become?
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Integument, NS, lens
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What does the endoderm become?
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Epithelial linings of digestive and respiratory tract
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What does the mesoderm become?
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Muskuloskeletal, circulation, excretory, gonads, connective
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What are the primary germ layers? Responsbile for?
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Ectoderm, Endoderm, Mesoderm; responsible for differentiation of body
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How is differentiation accomplished?
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Selective transcription of genomes
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What is induction?
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INfluence of specific groups of cells (ORGANIZER) on differentiation of other cells via chemical release of INDUCERS to adj. cells
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What is neurulation?
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Occurs at end of gastrulation to dev'p NS
Rod of mesodermal cells becomes NOTOCHORD which induces ectoderm to become NEURAL FOLD and fuse to become NEURAL TUBE (gives rise to B & SC) Cells at end of each neural fold = NEURAL CREST CELLS which migrate to become PNS |
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When is the embryo considered a fetus?
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Post 8-wks gestation
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Purpose of amnion?
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Tough membrane containing AMNIOTIC FLUID to act as shock absorber from ext and local sources (contractions)
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Purpose of chorion?
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Surrounds amnion, extends CHORIONIC VILLI into uterine wall to becomes PLACENTA
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Purpose of allantois?
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Contains blood vessels which will become UMBILICAL VESSELS which connect fetus to placenta (UMBILICAL CORD)
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What is the diffusive purpose of placenta?
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Site of nutrition, respiration, waste disposal for fetus
Water, glucose, aa's, vits, inorganic salts diffuse across maternal cappilaries into fetal blood |
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How does fetal hemoglobin differ from adult hemoglobin?
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Hb-F has greater affinity for O2; thus O2 diffuses INTO fetal blood while metabolis wastes and CO2 diffuse OUT of fetal blood
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How does the placenta provide protection for the fetus?
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Prevents diffusion of foreign mater into fetal blood (but is permeable to viruses, EtOH, drugs, toxins)
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What is the endocrine role of the placenta?
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Produces progesterone, estrogen and human chorionic gonadtropin
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Purpose of umbilical vein?
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Becomes oxygenated from placenta, delivers blood to fetus
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Describe fetal blood flow starting with the umbilical vein.
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Umbilical vein (O2'd)
Ductus Venosus (SHUNT 1) Inferior VC (partially O2'd) RA -->Foramen Ovale (SHUNT 2) OR -->RV From Foramen: Fovale LA LV DUCTUS ARTERIOSIS (SHUNT 3) Aorta Systemic circ-->Inf VC OR Umbilical artery-->Placenta From RV: RV Pulm Artery Pulm Circ-->Pulm Vein-->LA OR Aorta |
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List the three shunts of the fetal heart and the role each plays.
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Ductus Venosus: Nada
Foramen Ovale: diverts blood from pulmonary circuln (lungs don't oxygenate yet!) Ductus Arteriosis: Diverts blood from lungs |
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What changes in circulation occur after birth?
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Lungs fill with air
Decreased resistance in pulmonary vessels means increased blood flow to lungs Blood flow from umbilical cord stops, decreasing P in Inf VC, decreasing P in RA, increasing P in LA due to Pulmonary output, Foramen Ovale CLOSES Other shunts close too Infants produce Hb-A |
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What are the major events of the three trimesters of human gestation?
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First: Major organs dev'p
Second: fetus grows, moves in amniotic fluid Third: rapid growth, brain dev't, antibodies transported from mother to fetus, growth rate slows, less active (less rom to move) |
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What events allow for birth?
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Strong uterine contractions (labor)
Amniotic sac ruptures Cervix dilates |
