Lecture 21: Thorax IV, Heart Development

Question 1

what is the lub sound

Answer 1

closure of AV valves

Question 2

what is the dub sound

Answer 2

closure of semilunar valves

Question 3

what heart valves are auscultated on left side (3)

Answer 3

-aortic
-pulmonary
-mitral/left atrioventricular

Question 4

what heart valve is auscultated on right side

Answer 4

tricuspid/right atrioventricular

Question 5

where does heart tube/cardiogenic region develop from

Answer 5

visceral lateral plate mesoderm

Question 6

craniocaudal folding: moving head into thorax

Answer 6

-ectoderm and endoderm fold at ends (cranial and caudal ends fold towards each other)
-mesoderm is pulled caudally, now in neck area
-embryo continues folding until cardiogenic region in chest cavity
-heart tubes get pulled into pericardial cavity, they fuse
-

Question 7

how does heart primordium move ventrally (body folding)

Answer 7

pericardial cavity, heart tube and septum transversum move caudally until pericardial cavity is ventral to heart tube
-all these will be ventral to developing foregut

Question 8

what is the septum transversum

Answer 8

precursor to part of diaphragm (caudal to heart)

Question 9

where does the diaphragm migrate

Answer 9

from cervical to thoracic position because of differential growth of embryo

Question 10

formation of phrenic nerve

Answer 10

from axons of ventral rami from cervical spinal cord levels C5-7

Question 11

C7, C6, C5 keep the diaphragm alive

Answer 11

because the phrenic nerve arises in the neck from C5, C6 and C7

Question 12

steps of embryological development (general)

Answer 12

-lateral folding to form heart tube
-cardiac looping
-restructure venous system
-septation
-closing of shunts

Question 13

lateral body folding to move/form endocardial heart tubes

Answer 13

-lateral folding brings 2 endocardial tubes together
-myoblasts give rise to myocardium
-endocardial tubes fuse into 1
-heart tube surrounded by myocardium
-myocardium secretes cardiac jelly

Question 14

what does cardiac jelly turn into

Answer 14

endocardial connective tissue

Question 15

what are the primary outflow of oxygen poor blood from the fetus

Answer 15

dorsal aortae

Question 16

early vessel development and blood flow

Answer 16

-blood received at caudal pole of heart tube at sinus venosus
-blood delivered from cranial end of heart tube and passes through aortic arches and sac

Question 17

function of sinus venosus

Answer 17

receive blood

Question 18

location of sinus venosus

Answer 18

cranial to heart tube (right next to it)

Question 19

structures of heart tube from cranial to caudal (9)

Answer 19

-outflow tracts = dorsal aortae/aortic roots
-aortic sac
-truncus arteriosis
-bulbus cordis
-bulboventricular sulcus
-primitive ventricle
-atrioventricular sulcus
-primitive atria
-sinus venosus

Question 20

primitive ventricle will become

Answer 20

left ventricle

Question 21

truncus arteriosis and conis cordis will become (2)

Answer 21

pulmonary arteries/trunk and aortic arch

Question 22

bulbus cordis will become (3)

Answer 22

right ventricle
right and left outflow tracts (left outflow from left ventricle, right outflow from right ventricle)

Question 23

primitive atria will become (2)

Answer 23

right and left atria

Question 24

sinus venosis will become (3)

Answer 24

common cardinal veins
umbilical veins
vitelline veins

Question 25

when does cardiac looping occur

Answer 25

after formation of heart tube

Question 26

where does cardiac looping occur

Answer 26

inside pericardial cavity

Question 27

cardiac looping: steps

Answer 27

-bulbus cordis shifts cranially, ventrally and to the right -primitive ventricle shifts to the right (towards midline) -primitive atria move caudally, dorsally, to the left (backwards and then upwards, pushed back behind) -formation of interventricular sulcus with ventricle separation starting -conus cordis forms distal outflow tracts for right and left ventricles

Question 28

result of cardiac looping

Answer 28

-displace neighboring structures

Question 29

restructuring of venous system

Answer 29

-veins on left horn of sinus venosis break down -left horn becomes coronary sinus -right horn gets bigger and becomes smooth part of right atrium

Question 30

right common cardinal vein will become

Answer 30

cranial vena cava

Question 31

right vitelline vein will become

Answer 31

caudal vena cava

Question 32

function of inflow tracts

Answer 32

take blood and empty into right atrium

Question 33

what 3 veins are located on the left and right horns of the sinus venosus (lateral to medial)

Answer 33

common cardinal vein umbilical vein vitelline vein

Question 34

what happens to the umbilical vein

Answer 34

distintegrates

Question 35

primitive blood flow

Answer 35

common atrium --> AV canal --> primitive left ventricle --> interventricular foramen --> right ventricle --> out through bulbus cordis (conis cordis and truncus arteriosis)

Question 36

where do pulmonary veins sprout off of

Answer 36

left part of primitive atrium

Question 37

primordial part of left atrium is what

Answer 37

left auricle

Question 38

4 septation processes

Answer 38

-atrioventricular -atrial septation -ventricular septation -articopulmonary septation

Question 39

1st septation to occur

Answer 39

atrioventricular

Question 40

atrioventricular septation: process

Answer 40

-endocardial cushions develop between atrium and ventricle -cushions grow towards each other from each side -fusion divides AV canal into right and left parts

Question 41

what is the structure formed when endocardial cushions fuse (hint: wall)

Answer 41

septum intermedium

Question 42

product of atrioventricular septation

Answer 42

separate left and right sides of heart -create right AV canal and left AV canal

Question 43

function of septum intermedium

Answer 43

separate primitive atria and primitive ventricle

Question 44

what do ventricles/heart do during cushion fusion

Answer 44

heart realigns so both ventricles line up with truncus arteriosis

Question 45

purpose of atrial septation

Answer 45

separate right and left atria

Question 46

atrial septation: process

Answer 46

-septum primum grows between primitive atria roof -grows down toward endocardial cushions but is stopped before reaching which creates a space = foramen primum -foramen primum forms a shunt to bypass the right ventricle -perforations appear in septum primum to form forman secundum as foramen primum closes due to growth of septum primum -septum secundum begins to grow to close foramen secundum

Question 47

foramen ovale: definition and importance

Answer 47

space remaining between septum secundum and formen secundum -where blood bypasses right atrium into left atrium (no lungs)

Question 48

ventricular septation: function

Answer 48

separate bulbus cordis (part of the right ventricle) and primitive ventricle (left ventricle)

Question 49

ventricular septation: process

Answer 49

-muscular interventricular septum arises from floor of primitive ventricle -doesn't fuse with endocardial cushions -incomplete fusion leaves gap = interventricular foramen

Question 50

aorticopulmonary septation: result

Answer 50

divide pulmonary trunk from aorta

Question 51

aorticopulmonary septation: process

Answer 51

-AP septum spirals so aorta and pulmonary trunk twist around each other -pulmonary outflow = right ventricle aortic outflow = left ventricle

Question 52

3 shunts that bypass liver and lungs during fetal circulation

Answer 52

-foramen ovale -ductus arteriosis -ductus venosus

Question 53

formane ovale: shunt

Answer 53

from right atrium to left atrium to bypass right ventricle

Question 54

adult remnant of foramen ovale

Answer 54

fossa ovalis

Question 55

ductus arteriosis

Answer 55

shunt from pulmonary trunk to aorta to bypass lungs

Question 56

adult remnant of ductus arteriosis

Answer 56

ligamentum arteriosum

Question 57

how does foramen ovale close

Answer 57

pressure changes as a result of ductus arteriosus closing pushes septum primum against septum secundum to close off foramen ovale