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84 Cards in this Set
- Front
- Back
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Embryonic period
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Zygote formation thru 8th week
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Fetal period
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End of 8th week - birth
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Major period of risk for teratogens
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3-8 weeks
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Primordial germ cells: When do they differentiate?
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4-6 weeks
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What layer do primordial germ cells differentiate from?
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Endodermal layer of yolk sac
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When do the genital ridges form?
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6-12 weeks
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In males, what do the primordial germ cells become (immediately after)?
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Spermatogonia, after dividing several times
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What causes maturation of seminiferous tubules?
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Testosterone release
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What do the spermatogonia become? (Hint: meiosis)
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Spermatozoa
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In females, what do the primordial germ cells become?
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Oogonia
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What do the oogonia become?
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Primary oocytes
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When do the oogonia enter meiosis?
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As primary oocytes, by the 3rd month
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When are all the primary oocytes a female will produce formed by?
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5th month
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What stage of meiosis do the primary oocytes remain arrested in until puberty/ovulation?
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Prophase 1
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What is the name of the layer of cells surrounding the oocytes?
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Primary follicle
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What does the hypothalamus release during the menstrual cycle?
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Gonadotropin releasing hormone
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What does Gonadotropin releasing hormone do?
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Stimulates anterior pituitary to release follicle stimulating hormone (FSH) and luteinizing hormone (LH)
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What does FSH do?
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Escalates follicular growth/causes maturation of the follicle. Follicle produces estrogen.
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What causes corpus luteum to form in the empty follicle (after egg has been released?)
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luteinizing hormone
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When is there an FSH spike?
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3 days into menstrual cycle
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When is there an LH spike?
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14 days into menstrual cycle
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What does corpus luteum release?
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Progesterone
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What does progesterone do?
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Supports the maintenance and thickening of the endometrial lining.
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What happens to the corpus luteum is pregnancy does NOT occur?
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Shrinks due to reduced progesterone. Uterine lining is shed (period)
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What happens to the corpus luteum is pregnancy DOES occur?
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Persists and maintains uterine lining
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Where does fertilization occur?
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Ampullary duct of fallopian tube
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What causes the oocyte to resume mitosis?
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Penetration of the zone pellucida by sperm
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What does the morula split into?
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1) Inner cell mass/embryoblast
2) Outer cell mass/trophoblast |
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What part of the blastocyst become the placenta?
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Outer cell mass/trophoblast
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What part of the blastocyst become the embryo?
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Inner cell mass/embryoblast
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What is the invasive cell type that causes the blastocyst to burrow into uterine wall?
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Syncytiotrophoblastic cells
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What hormone prevents degradation of the corpus luteum?
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Human chorionic gonadotropin
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What does the embryoblast split into?
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Epiblast, hypoblast. Together called bilaminar disc.
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What makes up the chorion?
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Outermose fetal membrane made of 3 tissues:
1) Syncytiotrophoblast 2) Cytotrophoblast 3) extraembryonic somatopleuric mesoderm |
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Defn of gastrulation (DETAILED)
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Bilaminar disc (epi- and hypoblast) changes to trilaminar disc (endo-, meso-, and ectoderm)
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Nervous tissue, skin, and hair are derived from what cell layer?
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ectoderm
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Vascular, urogenial, muscle system, and axial skeleton from what cell layer?
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mesoderm
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GI tract, respiratory, urinary system from what cell layer?
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endoderm
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When does implantation occur?
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about 7 days
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What is the first structure formed that starts gastrulation?
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Primitive streak
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What is the cranial end of the primitive streak called?
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Primitive node
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What happens to the epiblast after the primitive streak is formed?
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Epiblast cells migrate down into the streak between the epi and hypoblast layers, pushing the hypoblast out to form the endoderm
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What are the three parts of the mesoderm?
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Paraxial, intermediate, and lateral
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What part of the mesoderm are the somites derived from?
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Paraxial
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What do the somites split into (3) and what do these form?
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1) Myotomes : muscle
2) Dermatomes: skin 3) Sclerotomes : vertebrae |
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What borders the coelom?
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Somatic and splanchnic mesoderm layers
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What forms the visceral pleura?
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Splanchnic mesoderm (from lateral plate mesoderm)
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What forms the parietal pleura?
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Somatic mesoderm (from lateral plate mesoderm)
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What is the first structure to (begin to) subdivide the coelum into thoracic and abdominal cavities?
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Septum transversum
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What does the septum transversum become in the adult?
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Central tendon of the diaphragm
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When is embryonic folding taking place?
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4th week
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Pleuroperitoneal membrane: What does it do?
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Closes off the pericardioperitoneal canals, completing separation of thoracic and abdominal cavities.
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What fuses with the septum transversum to become the Pleuroperitoneal membrane?
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Pleuroperitoneal folds
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Why do diaphragmatic hernias occur more often on the L side?
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The pericardioperitoneal canal tend to close later on the Left.
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A congenital diaphragmatic hernia is most likely to occur because of what?
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Failure for the pleuroperitoneal folds to close the pericardioperitoneal canal
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What grow out to separate the pericardial and pleural cavities? (separates lungs from heart)
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Pleuroparicardial membranes
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What makes up the primitive gut?
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From the endoderm.
Originally it has blind ending tubes but remains open to the yolk sac in the middle. |
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What are the 3 components of primitive gut?
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Foregut, midgut (opens into yolk sac), hindgut
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What is the vitelline duct?
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The opening of the midgut that connects the yolk sac to midgut.
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What are the arteries associated with the foregut, midgut, and hindgut?
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Respectively:
celiac trunk, SMA, IMA |
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Which organ in the abdomen is actually formed from mesoderm?
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spleen
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Which direction does the stomach rotate?
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Viewed from above, it rotates clockwise 90 degrees. The L vagus nerve is now anterior, and the R is posterior.
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When and where do first blood vessels form?
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3rd week. Extraembryonic blood vessels form first.
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What layer are blood vessels formed from?
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Mesoderm
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What is the first forerunner of heart?
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Endocardial tubes
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In the embryonic disc with the amnion cut away, where is the angiogenic cell clusters/cardiogenic region?
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Very tip of disc, caudal to everything. Forms horseshoe-like shape around neural region
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What direction does the heart move via transverse and cranial folding?
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Heart moves ventrally.
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Immediately before the bulboventricular loop is formed due to heart cells growing faster than other parts of embryo, the structures that will become the heart is a straight, paired tube. What is the direction of blood flow thru this tube?
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Blood comes into Sinus venosus via 3 pairs of veins. Then goes to pair of primitive atria, --> Primitive ventricle --> Bulbus cordis --> Truncus arteriosus --> Aortic arch
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What is exstrophied into L atrium?
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Primitive pulmonary vein portions
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What are the endocardial cushions?
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They're portions of the heart tube that grow inward at level of atrium and ventricle. They're the first in process of septation, and they make blood choose between a R or L side.
Forms R and L atrioventricular canals. |
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How does separation of the R and L atria occur?
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The septum primum grows from roof towards endocardial cushions, but leaves the foramen primum. Perforations them form in the septum primum before foramen primum closes. Perforations for foramen secundum. The septum secundum forms to the R of septum primum and grows toward endocardial cushion but leaves an opening called foramen ovale. Blood can still flow thru the atria until after birth when the pressure differential (higher in L atrium) closes the foramen ovale.
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What does the right ventricle form from?
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proximal/inferior end of bulbus cordis
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What does the left ventricle form from?
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Primitive ventricle.
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What does the primitive atria become in adult?
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The rough, trabeculated portions of both atria
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What is the truncus arteriosus?
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It's what gets separated to form the pulmonary artery and aorta.
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What types of cells line the forming aorticopulmonary septum?
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Neural crest cells
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Ventricular septal defects usually accompany______________
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aorticopulmonary defects
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What separates at the same time as the aorta and pulmonary artery?
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the two ventricles.
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What can a large L to R ventricular shunt result in?
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Pulmonary hypertension
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How does transposition of the great arteries occur?
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Instead of the normal spiraling of aorticopulmonary septum, it grows in a straight line. Aorta comes out of R ventricle and pulmonary artery comes out of L.
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What is the tetralogy of Fallot?
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1) Pulmonary stenosis (narrowing of pulm a.)
2) Overriding aorta (connected to both ventricles) 3) Ventricular septal defect 4) R Ventricular hypertrophy (Because of increased pressure) |
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The R atrium is primarily derived from what?
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Sinus venosus
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Closure of the foramen primum results from fusion of the _______
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Septum primum and endocardial cushion
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during the early separation of heart chambers, the AV foramen is separated by:
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Endocardial cushion
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