02 - Cardiac Development Flashcards
What are the two closed circuits of the adult circulatory system
How are they connected
connected in series
- pulmonary circuit –> removal of CO2, oxygenation of blood
- systemic circuit –> delivery of O2 and nutrients to tissues, transportation of wastes to organs of elimination
TF for adults, pressure on the right side of the heart is greater than the pressure on the left side of the heart
F
pressure on the left side (oxygenated blood) of the heart is greater than the pressure on the right side (deoxygenated blood) of the heart
What is the fetal circulatory system composed of
How do they communicate
open circuits that operate in parallel
two circuits communicate through bypasses/shunts
Which side is pressure greater in a fetus circulatory system
right side greater than left side (high pulmonary resistance)
- vessels in the lungs are collapsed because not breathing out air
Where is blood with the highest oxygen content found in a fetus
in the umbilical vein (oxygenated)
- because exchanged blood with maternal blood across the pacental membrane
Where happens in a fetus placenta
gas exchange, nutrient and waste transfer
- provides oxygen and nutrients to the fetus
does the work of the heart, the kidney and the liver
TF fetal circulation mixes with maternal circulation
False
- never mixes
- at most, two cells away from each other
placenta acts as an exchange membrane
Describe how the blood flows through the circulatory system
- placenta
- umbilical vein(highest oxygen concentration)
- umbilicus
- liver (developing, not functioning) – so a lot of blood bypasses through to the ductus venosus
- inferior vena cava (also drains blood from lower abdomen so mixes with deoxygenated blood)
- right atrium
- left atrium (directly because foramen ovale –> hole in interatrial septum – wall between atriums)
- left ventricle
- aorta
- supplies rest of body
- umbilical arteries –> become part of umbilical cord, wrap around umbilical vein and send systemic blood to placenta to offload waste and get oxygen back
Blood can also enter right atrium from sup vena cava (head, neck, upper limbs) –> right ventricle –> pulmonary trunk –> aorta through ductus arteriosus (allows mixed blood from right side to systemic circuit)
interal iliac: branch off of the abdominal aorta – goes to right and left legs, across pelvis, feeds bladder and reproductive structures and placenta
don’t need to send a lot to lungs because not doing gas exchange
Which structures allow mixed blood from right side of heart to left side of heart
ductus arteriosus
foramen ovale
What are the purposes of bypasses and shunts
divert blood around organs that have limited function in utero
deliver oxygenated blood from he placenta to the systemic circuit (left side of heart) as quickly as possible
Which fetal structures change postnatal
foramen ovale
ductus arteriosus
ductus venous
umbilical arteries
umbilical vein
What happens when bypasses/shutns and other fetal vessels close after birth
become remnant structures that persist in the adult
What happens to the umbilical vein at birth
umbilical vein –> ligamentum teres (white band of tissue in the anterior abdominal wall) – collagen (scar tissue)
What happens to the ductus arteriosis
ductus arteriosus closes – because of vasoconstricts after taking first breath -> lungs starts producing bradykinin to tell to close – replaced by collagen, becomes ligamentum arteriosum
What happens to the ductus venosus
ductus phenosis – vein collapses to seperate right and left lobes of liver –> ligamentum venosum
What happens to the formane ovale
foramen ovale closes - first expansion of lungs decreases pulmonary vascular resistance – (alveoli exapands, BV stretches = open up) pressure on the right decreases compared to left causing the foramen ovale to close (prevents blood from going from left to right) –> develops fossa ovalis (depression)
What happens to the umbilical arteries
become medial umbilical ligamets (from bladder up the anterior abdominal wall)
Describe the development of the heart
fusion of heart tubes (20-21 days)
- two tubes fuse together with a venous (entering) end and an arteriol (ejection) end
sacculation (22 days)
elongation
- forms buldges –> truncus arteriosus (great vessels coming off heart) –> bulbus cordis (right ventricle) –> ventricle (left ventricle)–> atrium –> sinus venosus
folding (U- to S-shape) (24 days)
partitioning
- forms all the chambers of the heart (still has all the parts from sacculation and elongation)
primordial heart (28 days)
- primordial structures become the chambers and great vessels of the heart
What does the truncus arteriosus develop into
great vessels of the heart (aorta & pulmonary trunk) – major outflow tracts of atriums
When does the development occur
through the division of the truncus arteriosus by an aorticopulmonary (spiral) septum
What does the septum form from
lateral ridges of the truncus arteriosis
spiral septum will twist 180 degrees when completely formed
What happens with persistent truncus
failure of the aorticopulmonary septum to form
- right and left ventricles share the same outflow tract and there is mixing of blood
- also a ventricular septal
= right ventricular hypertrophy
What happens if the aorticopulmonary septum does not spiral 180 degrees
leads to transposition (switch) of the great vessels
- the right ventricle leads to the aorta while the left ventricle leads to the pulmonary trunk (two circuits operating in isolation)
= right ventricular hypertrophy
Where do the semilunar valves of the heart develop
at the base of the truncus arteriosus
What does the formation of the spiral septum help to do
- partition the truncus arteriosus into great vessles
- partition the semilunar valve cusps
What does the truncus arteriosus develop into (how does it partition the semilunar valves)
1 vessel + 4 cusps –> 2 vessels + 3 cusps each
What happens in unequal partitioning of the truncus arteriosus by the aorticopulmonary septum
results in semilunar valve stenosis
- one side expanded
- one side stenosed
What happens in pulmonary valve stenosis (narrowing)
obstruction
reduced flow into pulmonary trunk
pressure overload - more resistance and pressure on right side of heart
acyanotic or cyanotic depends on the extent of the stenosis (assuming the DA has closed)
How to repair a valve stenosis
- stabalize with prostaglandins to promote relaxation of ductal smooth muscle
- undergo balloon valvuloplasty to repair the stenosed pulmonary valve (stretches valve)
- balloon catheter advanced up the femoral vein –> IVC –> right atrium –> right ventricle –> pulmonary semilunar valve
What happens in patent ductus arteriosus
leads to volume overload in the pulmonary circuit – too much blood flow
increased blood flow can lead to pulmonary edema (interferes with proper oxygenation of the blood)
shunt (blood flowing from aorta to trunk)
blood flows from aorta to pulmonary trunk
Volume overload – more blood volume in the pulmonary circuit
acyanotic or cyanotic depends on the extent of the volume overload (pulmonary edema)
How to treat patent ductus arteriosus
ligation (tying off) of the patent ductus arteriosus
stabalize before surgery using indomethacin (a prostaglandin synthesis inhibitor)
How is the interatrial septum formed
first wall – septum primum
- forms the valve
second wall – septum secundum
- forms the bulk of the interatrial septum and the foramen ovale (between the two atria and an associated valve that closes at the time of birth)
What does the valve of the foramen ovale do
permits blood to flow from right to left in utero but prevents left to right movement postnatally
What controls the opening and closing of the foramen ovale
changes in pressure
What are the two major vascular changes that occur imediately after birth
- increased systemic resistance with loss of placenta
- decreased pulmonary vascular resistance with breathing
What happens in a patent foramen ovale
foramen ovale is open after birth
- volume overlaod of the right side of the heart as blood is shunted from left to right atrium (too much blood in lungs, but wouldnt cause edema)
- mixing blood from right to left shunt (goes back through lungs)
shunt
flow from left to right atrium
volume overload -more blood volume through the pulmonary circuit
asymptomatic for decades (rarely cyanotic)
What happens in the formation of the interventircular septum
from the apex toward sthe centre of the hear (endocardial cushion)
- consists of a muscular and membranous (thin) portion
gives rise the valves of the heart
