Circulatory System Development I

Question 1

Percentage of congenital defects that are heart defects

Answer 1

20%

Question 2

Most common heart defect

Answer 2

Ventricular septal defect

Question 3

Percentage of congenital heart defects w/ unknown cause

Answer 3

85%

Question 4

Percentage of heart defects have genetic basis

Answer 4

10%

Question 5

Down syndrome is assoc. w/ congenital heart defects in ___ percentage of cases

Answer 5

50%

Question 6

Percentage of congenital heart defects caused by teratogens

Answer 6

5% of cases

Question 7

What kind of drug is assoc. w/ heart defects

Answer 7

Lithium

Question 8

Maternal diseases that affect heart formation

Answer 8

Diabetes and German measles

Question 9

How long does embryo obtain nourishment via simple diffusion

Answer 9

Through 2nd week

Question 10

First organ system to develop

Answer 10

Cardiovascular system formed primarily by extraembryonic and intraembryonic mesoderm

Question 11

Mesenchymal cells

Answer 11

. Primary CT cells in extraembryonic and intraembryonic mesoderm form clumps

Question 12

Blood islands

Answer 12

. Clumps in mesoderm
. Coalesce to form primitive blood vessels lined w/ endothelial cells and filled w/ primitive blood cells
. smooth muscle and CT of blood. Vessels form later from same mesoderm

Question 13

Primitive blood vessels connect the embryo to vessels in the ____

Answer 13

Yolk sac (Vitelline vessels) and the placenta (umbilical vessels)

Question 14

Blood flows out to embryo proper in ____ that fuse caudally to form ___

Answer 14

. Paired dorsal aortae

. Single dorsal aorta

Question 15

Cardinal veins

Answer 15

. Carries blood back from embryo proper

Question 16

Heart development begins as paired ______

Answer 16

Cardiogenic cords in the intraembryonic splanchnic mesoderm in the cardiogenic area

Question 17

Cardiogenic area

Answer 17

. Originally lies cranial to oropharyngeal membrane

. Comes to lie in area of future thoracic cavity when embryo undergoes folding

Question 18

Cardiogenic cords develop lumens and become ____

Answer 18

Paired R and L endothelial heart tubes

Question 19

Heart tubes

Answer 19

. Formed only of endothelium, but cardiac muscle and CT layer develop later from surrounding mesoderm
. Non-cellular layer of cardiac jelly lies immediately external to the endothelium
. Mucopolysaccharide-rich layer is later invaded by endothelial cells forming endocardium cushion tissue that helped form heart valves
. Tubes fuse together to form a single heart tube

Question 20

Single heart tube

Answer 20

. Connected to embryonic vessels and vessels in the umbilical cord and yolk sac
. Heart tube elongates and develops various dilutions and constrictions

Question 21

Sinus venous (SV)

Answer 21

. Received blood from Vitelline, cardinal and umbilical veins via sinus horns

Question 22

Common atrium (A)

Answer 22

Single chamber

Question 23

SV and A constitute the ____

Answer 23

Venous (caudal) region

Question 24

Primitive ventricle (V)

Answer 24

. Single chamber

. Called primitive L ventricle when it develops trabeculae Carneae

Question 25

Constriction btw primitie atrium and primitive ventricle becomes ___

Answer 25

Coronary (AV) sulcus

Question 26

Atrioventricular canal

Answer 26

Channel btw common atrium and primitive ventricle

Question 27

Bulbus cordis (B)

Answer 27

. Prox. Portion develops trabeculae carneae and becomes primitive R ventricle . Distal portion adjacent to truncus arteriosus (TA) is called conus cordis

Question 28

truncus arteriosus (TA) leads into ___

Answer 28

. Right and left aortic arches that connect to dorsal aortae

Question 29

Arterial (cranial) region

Answer 29

V, B, and TA

Question 30

Day primitive heart starts to beat and how

Answer 30

22 by peristaltic contractions that begin at sinus venosus and push blood through heart

Question 31

T/F primitive heart contractions DO NOT require innervation or development of conducting system

Answer 31

T

Question 32

Looping process of heart

Answer 32

. Heart grows and forms S-shaped loop that projects anteriorly . Venous end of heart moves cranially by moving dorsal to arterial end

Question 33

Formation of visceral and parietal pericardium

Answer 33

. After embryo folds, developing heart lies dorsal to portion of intraembryonic celom that will form pericardial sac . Sac grows ant. And it pushes into the intraembryonic celom forming this

Question 34

Because of heart looping, venous portions of the heart form _____ and primitive ventricle projects ____ and the truncus arteriosus exits pericardial sac ____

Answer 34

. Form base of heart . Projects ant. . Superiorly

Question 35

What weeks does partitioning of the heart into 4 chambers begin?

Answer 35

Week 4

Question 36

Initial separation of the primitive atrium

Answer 36

. After heart tube, the truncus arteriosus located anteriorly presses on the common atrium (post. To the truncus arteriosus) . Protrusion of truncus arteriosus into the common atrium divides the chamber into primitive R and L atria (no septum formed) . Opening of sinus venosus shifts from midline to right so sinus venosus only opens into R atrium

Question 37

Path of blood flow through developing heart at time of initial separation of primitive atrium

Answer 37

``` .sinus venosus primitive R atrium . Primitive L atrium . Atrioventricular canal . Primitive left ventricle . Primitive R ventricle (caudal part of bulbus cordis) . Conus cordis (cranial part of bulbus cordis) . Truncus arteriosus . Aortic arches ```

Question 38

Atrioventricular canal shift

Answer 38

. Originally lies btw primitive left atrium and primitive L ventricle then shifts from left side to midline . Blood passes from primitive atria into both of the primitive ventricles

Question 39

Valve formation

Answer 39

. Endocardial cushions derived from cardiac jelly project into undivided AV canal . Cushions fuse and divide the canal into R and L AV openings . Tri/bicuspid valves will eventually form tissue of endocardial cushions and control blood flow through the R and L AV canals

Question 40

Formation of the definitive R atrium

Answer 40

. Opening btw R atrium and sinus venosus enlarges so right horn of sinus venosus becomes incorporated into wall of R atrium . Primitive R atrium represents by portion of R atrium and auricle lined w/ musculi pectinati . Sinus venosus becomes smooth post. Wall in adult R atrium . Left horn of sinus venosus becomes coronary sinus

Question 41

Formation of definitive L atrium

Answer 41

. As lungs form, the primitive L atrium send vein buds out to each lung . These buds branch out and enlarge . Initial portion of pulmonary veins becomes incorporated into developing L atrium forming its wall . The L auricle is the only remnant of primitive L atrium

Question 42

Foramen (ostium) primum

Answer 42

. Opening btw R and L atrium | . Originally very large

Question 43

Septum primum

Answer 43

. Membrane that grow inf. From the roof of the common atrium . Separates R and L atria and closes the foramen primum as it grows toward endocardial cushions and then fuses w/ cushion

Question 44

Foramen (ostium) secundum

Answer 44

. Before primum disappears the sup. Portion degenerates and this a opening appears . Degeneration of septum primum involves apoptosis . Blood flows from R atrium into L atrium through this

Question 45

Septum secundum

Answer 45

. Second membrane that grows down from atrial roof directly adjacent to septum primum . More rigid than septum primum . Grows until it covered foramen secundum but doesn’t form completely wall btw atria . Oval opening present at inf. End (foramen ovale)

Question 46

T/F septum primum overlaps foramen ovale so there is not a direct line btw foramen secundum and foramen ovale

Answer 46

T, look moves obliquely through interatrial septum prenatally

Question 47

How blood passes from R to L atrium

Answer 47

. Goes through foramen ovale and then through foramen secundum by pushing down portion of septum primum that covers foramen ovale

Question 48

What occurs to septum primum a and secundum after birth?

Answer 48

. Fuse due to shifting in pressure dynamics of the heart from beginning of respiration in newborn . L atrium has high pressure than R atrium . Pressure difference forces septum primum against secundum so that they fuse into solid structure closing the openings btw atria

Question 49

Atrial septal defect (patent foramen ovale)

Answer 49

. Common . Ostium primum type: foramen primum remains open from inadequate septum primum or endocardial cushions growth, located inf. On interatrial septum close to cushions . Foramen secundum: excessive resorption of septum primum during development resulting in large foramen secundum OR inadequate septum secundum development resulting in large foramen ovale, or combo of both

Question 50

Atrial septal defects allow ____

Answer 50

Shunting of blood btw R and L atria mixing oxygenated and deoxygenated blood

Question 51

What happens immediately after birth with atrial septal defects?

Answer 51

. Blood shunts from high pressure L atrium to R atrium . Reactive pulmonary vasoconstriction from volume loading on R side . Inc. resistance o right side causes secondary inc. in pressure in R atrium . Shunt will change direction from left-to-right to right-to-left forcing more deoxygenated blood into L atrium and ventricle . Eventually causes death due to ischemia in organs like kidney and liver