Development of the Heart

Question 1

when does the CV system begin to appear?

Answer 1

mid week 3, heart functions during week 4

Question 2

establishing and patterning of primary heart

Answer 2

-progenitor cells (once in epiblasts) migrate thru primitive streak into splanchnic layer of lat plate mesoderm

Question 3

what is the first sign of heart

Answer 3

solid horseshoe shape = primary heart field (PHF) (cells will form atria, LV and part of RV)

• underlying endoderm induces PHF to form cardiac myoblasts
• blood islands and vessels via vasculogenesis)
• vasculogenesis: BVs arise from blood islands
• angiogenesis: BVs sprout from existing vessels

Question 4

when does heart tube formation and positioning occur

Answer 4

18-22 days

Question 5

heart tube formation and positioning

Answer 5

• blood islands unite in jorseshoe shaped endotheliam lined tube in cardiogenic region (endocardial tubes)
• other islands appear at midline to form dorsal aortae
• lat body folding creates primordial heart tube (lat sides forl ventrally and medially and fuse at midline)
• cranial caudal folding occurs and repositions developing heart and pericardial cavities

Question 6

what is the hinge for ventral swinging during body folding?

Answer 6

oropharyngeal mem

Question 7

position of heart prior to folding

Answer 7

rostral to oropharyngeal mem and ventral to pericardial cavity

Question 8

what initially attaches heart tube to dorsal side of pericardial sac

Answer 8

dorsal mesocardium

*middle part disappears to form transverse pericardial sinus (present in adults)

Question 9

what gives rise to SA and AV nodes

Answer 9

SA canal

Question 10

sinus venoses

Answer 10

• receive blood from 3 paired vv
  1. viteline vv
  2. umbilical vv
  3. common cardinal vv

Question 11

what happens when blood flow in heart shifts R

Answer 11

R horn becomes larger than L

-L sinus horn becomes 1. oblique vv of LA 2. coronary sinus

Question 12

what does R sinus horn become incorporated into

Answer 12

R atrium (smooth walled part, sinus venarum), resulting in 1. L valve and septum spurium fuse with atrial septum

2. sup portion of R valve disappears
3. inf part of R valve becomes valve of IVC and coronary sinus

Question 13

what is the ridge separating smooth and rough wall of RA

Answer 13

crista terminalis

Question 14

when does partitioning of heart occus

Answer 14

30 days

Question 15

partitioning of heart

Answer 15

• atrial partitioning beginning
• primary IV foramen undivided
• outflow tracts undivided
• prox part bulbus cordis becomes trabeculated = R vent
• AV canal undivided

Question 16

what are the two ways to form septa

Answer 16

1. endocardial cushions

2. growth/expansion (meeting and fusing)

Question 17

septum primum

Answer 17

-extends toward end cushions in AV canal (opening below = ostium primum, foramen primum), it closes perforations in septum primum coalesce to form ostium/foramen secundum

Question 18

septum secundum

Answer 18

develops from roof of primordial atrium, to the R of the septum primum, grows inferiorly and develops opening (foramen ovale)

Question 19

formation of fossa ovalis

Answer 19

after birth, prressure forces septums primum and secundum together

Question 20

partitioning of outflow tracts

Answer 20

• neural crest cells migrate into truncus arteriosus and bulbus cordis
• form truncal ridges and bulbar ridges (helps create septum in outflow tract)
• ridges spiral 180 resulting in spiral aorticopulmonary septum when ridges fuse

Question 21

definitive structure of truncus arteriosus

Answer 21

roots and prox portions of aorta and pulm tr

Question 22

definitive structure of conus cordis

Answer 22

outflow tracts of ventricles

Question 23

definitive structure of prox segment of bulbus cordis

Answer 23

R vent

Question 24

definitive structure of primordial vent

Answer 24

L vent

Question 25

definitive structure of primordial atrium

Answer 25

L and R auricles and trabeculated portions of aorta

Question 26

definitive structure of R horn of sinus venosus

Answer 26

sinus venarum (smooth walled part of RA)

Question 27

definitive structure of L horn of sinus venosus

Answer 27

coronary sinus

Question 28

definitive structure of primordial pulm v and brs

Answer 28

smooth walled portions of LA