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Cardiovascular > 7. Embryology of the Heart (HARC) > Flashcards

7. Embryology of the Heart (HARC) Flashcards

1
Q

when does FORMATION of the HEART BEGIN

A

DAY 18

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2
Q

when is the FIRST HEARTBEAT

A

22 DAYS

(blood forms later)

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3
Q

what are the 3 steps in the FORMATION of the HEART

A
  1. ENDOCARDIAL TUBES (primitive vessels) form on both sides of the embryo
  2. Folding of the embryo brings them together, so they FUSE to form SINGLE HEART TUBE
  3. Heart Tube FOLDS and PARTITIONS to create a
    4-CHAMBERED STRUCTURE
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4
Q

REGIONS of the HEART TUBE:
(at 21 DAYS)

A

caudal end

  • SINUS VENOSUM (Venous Inflow tract)
  • PRIMITIVE ATRIUM
  • PRIMITIVE VENTRICLE
  • BULBUS CORDIS
  • TRUNCUS ARTERIOSUS (Arterial outflow tract)

cranial end

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5
Q

name of the VENOUS INFLOW TRACT of the Developing heart

A

SINUS VENOSUS

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6
Q

name of the ARTERIAL OUTFLOW TRACT of the developing heart

A

TRUNCUS ARTERIOSUS

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7
Q

FOLDING of the HEART TUBE is the cause of..

A

ASYMMETRICAL GROWTH

  • Rapid GROWTH of the BULUS CORDIS and VENTRICLE
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8
Q

when does FOLDING of the HEART START

A

22 DAYS

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9
Q

what is visible from the growth of the Bulbus Cordis and Ventricle at day 22

A

BULBOVENTRICULAR GROOVE

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10
Q

what new STRUCTURES are visible from FOLDING at 23 DAYS

A

ATRIOVENTRICULAR GROOVE
(between atrium and growing ventricle)

(as well as bulboventricular groove)

1ST AORTIC ARCHES from the Truncus Arteriosus

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11
Q

when does the ATRIUM come POSTERIOR to / together with the VENTRICLE
(when starts to look like adult heart shape)

A

25 DAYS

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12
Q

PARTITIONING of the Heart (internal surface) into 4 CHAMBERS consists of 4 step:

A
  • FORMATION of ENDOCARDIAL CUSHIONS
  • PARTITIONING of ATRIUM (R+L)
  • PARTITIONING of VENTRICLE (R+L)
  • PARTITIONING of BULBUS CORDIS & TRUNCUS ARTERIOSUS (into aorta and pulmonary trunk)
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13
Q

what do the ENDOCARDIAL CUSHIONS do/become in partitioning of the heart

A

SEPARATES ATRIUM & VENTRICLES

BECOME ATRIOVENTRICULAR VALVES

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14
Q

what PARTITIONS the SINGLE ATRIUM into RIGHT and LEFT atria

A

ATRIAL SEPTUM (growing down)

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15
Q

what PARTITIONS the SINGLE VENTRICLE into RIGHT and LEFT atria

A

INTERVENTRICULAR SEPTUM

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16
Q

PARTITIONING of what gives rise to the AORTA and PULMONARY TRUNK

A

BULBUS CORDIS and TRUNCUS ARTERIOSUS

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17
Q

what do the ATRIOVENTRICULAR VALVES come from

A

ENDOCARDIAL CUSHIONS

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18
Q

when does PARTITIONING of the ATRIA take place

A

WEEKS 5-7

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19
Q

the 1ST WALL that forms in the ATRIA (to separate left and right) is the..

A

SEPTUM PRIMUM

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20
Q

1ST HOLE that forms in the SEPTUM PRIMUM

A

FORAMEN PRIMUM

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21
Q

2ND HOLE that forms in the SEPTUM PRIMUM

A

FORAMEN SECUNDUM

as small holes fuse together to become large foramen, allows foramen primum to disappear (fuse together

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22
Q

2ND HOLE that forms in the SEPTUM PRIMUM

A

FORAMEN SECUNDUM

as small holes fuse together to become large foramen, allows foramen primum to disappear (fuse together)

23
Q

what structure connects the openings into the right atria

A

SINUS SEPTUM

(forms part of the VALVE of the IVC, and VALVE of the CORONARY SINUS)

24
Q

2ND WALL that develops in the ATRIUM and how does it grow

A

SEPTUM SECUNDUM

  • Creates FLAP
  • COVERS SEPTUM SECUNDUM (hole) in the SEPTUM PRIMUM

allows blood to pass from RIGHT -> LEFT ATRIUM
but not left to right

25
Q

the FORAMEN OVALE is an OPENING in which structure

A

SEPTUM SECUNDUM of the atrium

26
Q

in the PARTITIONING of the BULBUS CORDIS and TRUNCUS ARTERIOSUS what form
(to give rise to aorta and pulmonary trunk)

A

BULBAR RIDGES and TRUNCAL RIDGES

27
Q

BULBAR and TRUNCAL RIDGES FUSE to form..

A

AORTICOPULMONARY SEPTUM

  • SEPARATES AORTA and PULMONARY TRUNK
28
Q

what happens to the TRUNCUS ARTERIOSUS during partition (key step)

A

180 DEGREE ROTATION

  • TWISTING
29
Q

SINUS VENOSUS (VENOUS INFLOW tract to heart) has RIGHT and LEFT HORNS

what does the LEFT HORN BECOME (regresses)

A

CORONARY SINUS

  • Drains into CORONARY ARTERIES
30
Q

SINUS VENOSUS (VENOUS INFLOW tract to heart) has RIGHT and LEFT HORNS

what does the RIGHT HORN BECOME (remains)

A
  • part of the SVC
  • part of the RIGHT ATRIUM
    (smooth wall part)
31
Q

CORONARY SINUS is DERIVED FROM..

A

LEFT HORN of the SINUS VENOSUS

32
Q

SVC is DERIVED partly FROM…

A

RIGHT HORN of the SINUS VENOSUS

33
Q

FETAL CIRCULATION consists of 3 SHUNTS

A
  • DUCTUS VENOSUS
  • FORAMEN OVALE
  • DUCTUS ARTERIOSUS
34
Q

which FETAL SHUNT(S) is used to BYPASS the LUNGS

A
  • FORAMEN OVALE
  • DUCTUS ARTERIOSUS
35
Q

how does the DUCTUS ARTERIOSUS DIVERT BLOOD away from lungs

A

BLOOD passes from PULMONARY TRUNK INTO AORTA

36
Q

DUCTUS VENOSUS is a shunt used to BYPASS the…

A

LIVER

(as would take oxygenated blood)

37
Q

where does DUCTUS VENOSUS get blood from

A

from PLACENTA

  • takes it INTO IVC

-> HEART (where mixes with venous blood from SVC)

38
Q

DUCTUS ARTERIOSUS REDIRECTS BLOOD into the … instead of lungs

39
Q

how much of FETAL BLOOD does go to the LUNGS

A

10%

(90% prevented by FO and DA)

40
Q

why is only 10% of blood sent to lungs

A
  • lungs develop much later than heart (fully develop and fully functional after birth)
  • pulmonary vessels cannot handle full circulatory load, so reduces pressure on them
  • low oxygen increases pulmonary resistance and over stresses

however small amount allows PRACTICE for lungs and RIGHT VENTRICLE (pumping)

41
Q

what allows the O2-RICH BLOOD in the IVC to enter RIGHT ATRIUM and go straight to the FORAMEN OVALE (where passes into left)

A

PRESSURE and ANGLE

42
Q

where does the RIGHT VENTRICLE get its blood from to pump to developing lungs (to develop/prepare)

A

remainder from SVC / CORONARY SINUS

43
Q

How is FETAL HAEMOGLOBIN in comparison to adult haemoglobin

A

has much HIGHER AFFINITY for O2

  • due to LOW O2 ENVIRONMENT so must be able to LOAD more efficiently
    therefore becomes saturated at lower pO2

SHIFT to LEFT

(switch to adult haemoglobin within 6 months)

44
Q

how is the OXYHAEMOGLOBIN DISSOCIATION CURVE for FETAL OXYGEN

A

shifted to the LEFT due to HIGHER AFFINITY for O2

45
Q

FETAL LUNGS are FLUID-FILLED. what allows for the mechanical CLEARANCE of the fluid at birth

A
  • UTERINE and VAGINAL CONTRACTION COMPRESS fetal thorax (pressure)
  • ALVEOLI FILL and EXPAND after first breath (due to negative pressure) so remaining fluid PUSHED OUT of lungs into capillaries
46
Q

why can BLOOD go to the LUNGS after BIRTH

A

LOWER PULMONARY RESISTANCE

(drastic fall)

47
Q

what CLOSE upon BIRTH

A
  • FORAMEN OVALE (fossa ovalis remnant)
  • DUCTUS ARTERIOSUS (ligamentum arteriosum remnant)
  • DUCTUS VENOSUS (ligamentum venosum)
48
Q

what causes FORAMEN OVALE (flap-like valve) to CLOSE upon BIRTH

A

INCREASED BLOOD FLOW into LEFT ATRIUM from PULMONARY VEINS
(blood now coming in from pulmonary veins too)

  • INCREASED PRESSURE in LEFT ATRIUM

pushes against and causes gradual closure of the flap

(fusion in 3 months approx)

49
Q

what causes the CLOSURE of the DUCTUS ARTERIOSUS

A

PROSTAGLANDINS LEVELS DROP (PGE2, PGE1)

VASOCONSTRICTION of the DA until the LUMEN is FULLY CLOSED

in fetus: prostaglandins PGE2, PGE1 INHIBIT the vasoconstriction of DA

50
Q

in FETUS, PROSTAGLANDINS (PGE2, PGE1) that INHIBIT the VASOCONSTRICTION of DUCTUS ARTERIOSUS are SECRETED by…

A

the PLACENTA

hence after birth, prostaglandins levels drop and DA vasoconstriction

51
Q

what causes the CLOSURE of the DUCTUS VENOSUS at Birth

A

CONSTRICTION of SPHINCTER AROUND DV

  • due to PROSTAGLANDINS (drop)

BLOOD is FORCED into LIVER SINUSOIDS
- EMPTY DV FUSES/CLOSES

52
Q

what is the name of the REMNANT of the DUCTUS VENOSUS and where is it found

A

LIGAMENTUM VENOSUS

  • seen on POSTERIOR view BETWEEN LEFT & RIGHT LOBES of LIVER
53
Q

most common type of ATRIAL SEPTAL DEFECT (ASD):

A

PATENT FORAMEN OVALE / ‘ HOLE IN THE HEART’

foramen ovale portion or full is not fused, remains open (no fossa ovalis)

  • may present as cyanosis (poor circulation)
  • more noticeable in later infancy
    (breathlessness, tired)
54
Q

what can also be present / combined with an ASD

A

VSD - VENTRICULAR SEPTAL DEFECTS

  • PARTIAL ABSENSE of VENTRICULAR SEPTUM
    (rarely complete absence)

Cardiovascular (16 decks)

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