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Embryo Farmer Test 3

Embryology - Dr. Farmer - Test 3

QuestionAnswer
Angioblastic cords Week 3 - splanchnic mesoderm
Week 4 Heartbeat and blood flow 1st detected
Endocardial heart tubes Anterior to prechordal plate, then move to ventral portion of neck/thorax; fuse to form single tube-becomes endothelium; primordial myocardium around tube, splanchnic mesoderm, becomes myocardium in adult
Divisions Sinus venosus (rt. atrium)-receives blood, fixed in place by septum transversum, Atrium (rt and left), AV canal (AV valves), Ventricle (left), bulbus cordis-proximal-trabeculae of rt. ventricle, distal-conus cordis-outflow of both ventricles
Truncus Arteriosus Roots of pulmonary trunk and aorta, distributes blood, continuous cranially with aortic sac, fixed in place by pharyngeal arches
Bulboventricular loop By rapid growth of bulbis cordis and ventricles, causes atrium and sinus venosus to lie dorsal to trucus arteriosus, bulbus cordis and ventricles
Partitioning of AV canal Endocardial cushions-from dorsal/ventral walls; divide AV canal into left and right canal
Septum primum From roof of common atrium; foramen primus-ostium primum; foramen secundum-ostium secundum
Septum secundum To right of septum primum, foramen ovale
Sinus venosus Rt atrium (left horn becomes coronary sinus); Rt horn enlarges and opens into rt atrium; receives blood from head/neck thru developing SVC; receives all placental blood and caudal regions thru developing IVC; rt atrium-sinus venarum; crista terminalis
Left atrium Incorporation of primordial pulmonary veins
Ventricle Primordial IV septum-muscular ridge-midline near apex-becomes musc part of IV septum; ventricle walls dilate lateral to septum; IV foramen-b/t free edge of IV septum and fused endocardial cushions-closes wk 7
Closure of IV foramen IV foramen closure-bulbar ridges of bulbus cordis-endorcardial cushions; separate rt and left ventricles-rt opens to pulmonary trunk; left opens to aorta
Partitioning of bulbus cordis and truncus arteriosus Begins week 5-bulbar and truncal ridges-continuous with one another-from neural crest; ridges spiral 180 degrees-form aorticopulmonary septum-separates aorta and pulmonary trunks
Atrial septal defects Ostium secundum-patent foramen ovale due to faulty septum primum or secundum; ostium primum-incomp. fusion of endocard cush; patent foramen, cleft in left AV valve; probe patent foramen ovale-usu. not clinically significant
Common atrium septums primum and secundum don't form
Ventricular septal defects Membranous-most common, membranous ventricle fails to form; muscular-frequent, multi small openings, excess cavitation in wall formation; absence of IV septum-common ventricle, failure of muscular septum to form
Persistent truncus arteriosus Failure of truncal ridge and aorticopulmonary septal formation; common vessel drains heart and supplies system, pulmonary and coronary circulation; always accompanied by ventricular septal defect
Transposition of the Great Vessels Most common cause of cyanotic heart disease, most commonly aorta anterior to and rt of pulm trunk, aorta from rt vent, pulm trunk from left vent, accompanied by atrial septal defect and occasionally persistent ductus arteriosus, failure to spiral?
Unequal division of truncus arteriosus Faulty partitioning, includes IV septal defect, may include stenosis of valves, pulmonary valve stenosis or infundibular stenosis causes hypertrophy of rt ventricle
Tetralogy of Fallot Most commonly involving conotruncal region, 4 defects due to unequal divisions-pulmonary stenosis, ventricular septal defect, overriding aorta, rt ventricular hypertrophy
Aortic arches 1 for each pharyngeal arch-arise from aortic sac; 1 to 6
Dorsal aortae Fuse to form single vessel; caudal end becomes median sacral a.
Intersegmental aa. In neck become vertebral aa.; 7th intersegmental-left becomes left subclavian a.; rt becomes distal rt subclavian a.; in thorax-become intercostal aa.; 5th lumbar intersegmentals become common iliac aa.
Vitelline aa. Supply yolk sac; as gut develops, forms trunks associated with gut-celiac trunk, superior mesenteric a., inferior mesenteric a.
Umbilical aa. Branches form dorsal aortae, week 4 connects with developing common iliac a.; after birth-proximal becomes internal iliac aa. and superior vesical aa. and distal becomes median umbilical ligaments
Arch 1 derivatives Mostly regresses, maxillary aa., part of external carotid a.
Arch 2 derivatives Mostly regresses, hyoid aa. and stapedial aa. of middle ear
Arch 3 derivatives Proximal-common carotid aa. and external carotid aa.; distal-proximal portion of internal carotid aa., distal portion derived from dorsal aorta
Arch 4 derivatives Left-part of aortic arch between left common carotid and left subclavian aa.; right-proximal portion of right subclavian a.
Arch 5 derivatives Rudimentary or nonexistent
Arch 6 derivatives - LEFT Left-proximal-left pulmonary a., distal-ductus arteriosus-prenatal shunt b/t pulmonary a. and aorta, left recurrent laryngeal n. passes inferiorly
Arch 6 derivatives - RIGHT Right-proximal-right pulmonary a.-distal degenerates-allows right recurrent laryngeal n. to rise and hook around right subclavian a.
Aortic sac Ascending aorta; 2 horns-left-arch of aorta, right-brachiocephalic trunk
Arch of aorta Aortic sac, left 4th aortic arch, left dorsal aorta
Coarctation (constriction) of aorta Postductal-distal to ductus arteriosus, collateral circulation develops; preductal-no effect prenatally due to presence of patent ductus ateriosus, severe hypoperfusion postnatally when ductus closes
Primordial vv. Vitelline vv. from yolk sac; umbilical vv. from chorion; common, anterior/posterior cardinal vv. from body
Vitelline vv. Plexus around developing duodenum-hepatic portal v.; plexus in septum transversum inverted by developing liver cords-hepatic sinusoids and hepatic vv.; hepatic portion of IVC from rt vitelline v.
Umbilical vv. Rt v. regresses; left v. between liver and sinus venosus regresses, left v. persists as umbilical v.-carries all O2 blood from placenta to embryo; shunt in liver-ductus venosus-shofts blood from umbilical v. to IVC bypassing liver
Cardinal vv. Anterior cardinals-shunt shifts most blood to rt ant. cardinal then to left brachiocephalic v.; rt ant cardinal and common cardinal from SVC; post cardinals mostly regress, form root of azygos v. and common iliac vv.-replaced by supracards and subcards.
Supracardinal vv. drain body wall via intercostal vv.
Subcardinal vv. drain developing kidneys
IVC 4 segments-hepatic-from hepatic v. (right vitelline), prerenal segment-right subcardinal, renal-subcardinal and supracardinal anastomoses, postrenal-from right supracardinals
Fetal circulation High O2, nutrient-rich blood carried by umbilical v.; largely bypasses lungs.liver; liver bypass-ductus venosus-connects umbilical v. and IVC-physiological sphincter regulates flow;
Fetal lung bypass blood from IVC to foramen ovale to left atrium-crista dividens-provides O2 blood to head/neck/heart and upper extremities. Blood from rt ventricle to pulmonary trunk - 10% to lungs, most to ductus arteriosus to descending aorta
Transitional changes at birth Pressure changes, closure of foramen ovale, ductus arteriosus
Pressure changes Loss of placental circulation decreases blood pressure in IVC and right atrium; aeration of lungs-reduces pulmonary resistance, increases pulmonary blood flow, increases left atrial pressure
Closure of foramen ovale By increasing pressure in left atrium and decreasing pressure in right atrium; holds valve closed
Ductus arteriosus Pulmonary resistance lower than systemic resistance, flow into ductus arteriosus ceases, functionally closed within 2 to 3 days, anatomic closure by 4 months
Umbilical v. forms ligamentum teres hepatis (from umbilicus to portal v. in liver)
Ductus venosus Forms ligamentum venosum (within liver between portal v. and IVC)
Umbilical aa. Median umbilical ligament and superior vesical aa. (bladder)
Foramen ovale Fossa ovalis-functional closure at birth, anatomical closure by 3 months
Ductus arteriosus Ligamentum arteriosum by 12 weeks
Patent ductus arteriosus May be associated with rubella during 1st trimester, may be present in preemies, RDS can contribute
Respiratory system origins Endoderm-epithelial lining, splanchnic mesoderm-carticalge and m.; begins in week 4, laryngotracheal (respiratory) diverticulum from foregut, esophagotracheal ridges fuse and form septum-separates esophagus and trachea (and lung buds), laryngeal orifice
Larynx Lining from endoderm, cartilage and m. from mesenchyme of pharyngeal arches 4 and 6, innervated by Vagus n. (CN X)- superior laryngeal n. (arch 4) and recurrent laryngeal n. (arch 6)
Respiratory diverticulum Median trachea-lateral lung (bronchial) buds-penetrates pericardioperitoneal canal lateral to foregut; separate from pericardial cavity and peritoneal cavity by mesodermal folds to form pleural cavities
Bronchial divisions Primary bronchi-define lungs; Secondary bronchi-define lobes; Tertiary bronchi=define bronchopulmonary segments; 17 prenatal divisions, 6 postnatal divisions
Alveoli Appear later than bronchioles; Type I cells form blood-air barrierl Type II secrete surfactant to reduce surface tension in alveoli; # increases greatly after birth
Pseudoglandular developmental stage 5 to 17 weeks-terminal bronchioles only-no respiration possible
Canalicular development stage 16 to 25 weeks-respiratory bronchioles and alveolar ducts
Terminal sac developmental stage 24 weeks to birth, primitive alveoli with types I and II cells
Alveolar developmental stage Late fetal to 8 years-mature alveoli-additional respiratory structures (bronchiols, ducts, sacs, alveoli)
Tracheoesophageal fistulas Associates wtih digestive anomalies
RDS Respiratory Distress Syndrome - hyaline membrane disease, associated with prematurity, insufficient surfactant causes alveoli to collapse
Created by: lkeith