L10 heart development Flashcards
the heart
ventral splanchnic layer of head lateral mesoderm derivative
the heart is directly connected to the pharyngeal arches vix the aortic arches
blood travels through in a tubing - endocardium
pumping portion = myocardium
epicardium forms coronary arteries
pulmonary valve
prevent blood flow from vessels back into ventricles
vertebrate circulation system
left and right coronary arteries on surface of the heart
thick muscular myocardium
mammals:
deoxygenated blood enters right atrium via vena cava right ventricle receives blood and pumps out to the lung via pulmonary arteries
oxygenated blood enters left atrium pumped by left ventricle out into head and into body by the cartoter arteries and dorsal aorta
tadpole circulation sys
pharyngeal arches
with aortic arches inside allow oxygen acquired by the gills to be transported straight into the body
conc
teleost fish inflow from bottom
otherwise common denominator = separate chambers for inflow and outflow
heart is initially upstream of the aoric arches that inside pharyngeal arches
the most caudal aortic arch becomes the pulmonary arteries in lung breathers
function of blood
suppply neutrients
collection and disposal of waste
bufferning and osmoregulation
transport
oxygen
hormones - signalling
immune responses
bod temp in warm blooded animals
skeletal function vis the build up of hydrostatic presure
how does blood get round
small animals w slow metabolism - passive transport / diffusion
larger animals w high metabolic rates - active transport
open circulatory systems = no blood vessels. blood
without specialised pumps = hearts
animal doesnt have to develop and maintain a specialised organ
blood flow can be directly linked to activity e.g. peristatic activity of the gut
closed = with blood vessels
adv = works with a smaller volume of blood
with specialised pump = hearts
adv =
constant and controlled blood flow to all organs
development of high pressure systems
types of animal hearts
linear - insects
chambered w distinct in andoutflow tracs
gastropods - 2 chamers and vertebrates
peristaltic pumps in all bilaterians
amniote heart
starts as a simple tube
loops to the right
forms separate chambers for inflow + outflow
first unctional vertebrate heart is a linear pump
definitie outlow and inflow tracts are added on to primitive heart over time
latral mesoderm contributing cells for the primitibe, beating heart is the primary heart field
more medial/ dorsal mesoderm ells compared to primary heartd freld cells deliver head skeletal muscle + add cells after the heart starts beating these added on cells = secondary heart field cells
pharyngeal arch area cells
endocardim and myocaridum
endoderm closes the foregut
endocardial cells differentiation - edocardial tubes
myocardial cells differentiation around endocardium - contractile tube
cardiac jelly = between the 2
outer somatic aspect of lateral mesoderm will form pericardium + i between = lumen = pericardial cavity
lineage tracing head mesoderm
cells born in the primitive streak will settle in the head mesoderm
cells born later will settle in the trunk
BMP induces Nkx2.5 in the head but not in the trunk mesoderm
BMP from the cranial endoderm induces cardiac precursors or blood from LAteral endoderm
It is blocked by noggin from the notochord
BMP inducers FGF expression
this signals to the cranial lateral mesoderm to support cardiac development and stimulate events in the secondary heart field
Wnt from primitve streak.
and then from the neurl tube stimulate blood and supressed heart devleopment
blocked by wnt inhibitors such as crestn
in the trunk wnt supresses cardiogenesis
lateral plate mesoderm in head and trunk exposed to BMp
in head
bmp from the cranial endoderm induces cardia precursors or blood from lateral mesoderm = blocked by noggin in notochord
bm induces fgf in endodem
fgf signals to cranial lateral mesoderm
BMP from the cranial endoderm induces cardiac precursors or blood from Lateral endoderm
It is blocked by noggin from the notochord
BMP inducers FGF expression
this signals to the cranial lateral mesoderm to support cardiac development and stimulate events in the secondary heart field
Wnt from primitve streak.
and then from the neurl tube stimulate blood and supressed heart devleopment
blocked by wnt inhibitors such as crestn
in the trunk wnt supresses cardiogenesis
lateral plate mesoderm in head and trunk exposed to BMP
in head = the lateral mesoderm exposed to fgf and protected from wnt by wnt inhibitors
in trunk = lateral mesoderm exposed to BMP + wnt = cells turn into heamangogenic cell = blood + blood vessels
heart tube formation
driven by endoderm the cardiac tissue moves ventrally; the endoderm will fuse to form a gut canal = bilateral heart anlagen also fuse = single tubular heart in ventral midline
closure of the endoderm and cell migration along the endodem brings cardiac precursors to the ventral midlin
failure to reach the midlline leads to the independent formation for 2 bilateral hearts - cardla bifida
BMP induces Nkx2.5 in the head but not in the trunk mesoderm
the Nkx2.5 gen is expressed in cardiac precusor cells and is a conserved regulator of protostome and deutrostome heart devlopment
- necessary but not sufficient for heart development
nkx2.5 is induced by BMP from the lateral mesoderm and endoderm
Nkx2.5 is only induced in the Wnt free area that distinguishes the head from the trunk
in the trunk under the influence of wnt lateral mesodem generates blood and vasculature
specifiying inflow + outflow tract
inflow - retinoic acid active form of vitamin A
cardiac cells stained
cardiac looping and chamber alignment
direction of looping is controlled by the left right asymmetry system - which was established in gastrulation like the rostrol caudal axis
endocardial cushion formation and initial septation of the heart
the endocardium generates extracellular matrix that fills the place between the endocardium and myocardium
formation of chambers and valves
reptiles have 2
birds and mammals only one - other has been repurposed:
one aortic arch forms carotid arteries
and then one side of an aortic arch becomes one of the subclavan artery
the other becomes the descending dorsal aorta
tetrapods - connection w 7th aortic arch with the lungs
fetal oxygen transport from placenta via umbilical veins
feotal haemoglobin has a higher affinity for oxygen
redirecting mammalian blood flow at birth
expansion of the lung at birth
blood travels through atriums
blood is mixed because it travels across the atria and because there is still a connection between pulmonary arteries and descending aorta
= all organs get the same oxygen supply
the expansion of air into the lungs causes pressure changes that redirect the flow of blood in the newborn infant
the ductus arterious sqeeezes breaking off he connection between the aorta and the ppulmonary artery an the for foramen ovule a passageway between the left and right atria also closes
pulmonary seperated from systemic circulation
summary
the direction of heart looping depends on lef right axis determined at gatrulation
heart looping drives the alignment of he cardiac chambers
endocrrdial cushions and the outgrowing atrial and interventricular septa separate the left and right side of the heart
in lung breathing tetrapods the aortic arches are remodelled
the most caudal aortic arch becomes the pulmonary artery
systemic and pulmonary circulation separated at birth
open
initially when the septation that grows out in the middle of the atria left w an opening
how to separate out ventricles
through looping and endocardial cushions as the heart fold with atrium
mothers that drank alcohol can lead to closed internal ventricular septum
which signals
trunk interprets = i must make cardiac cell = myocardium + epicardiums- makes arteries
Nkx2.5 transcription factor involved
BMP and Fgf and bmp inhibitors
the initial signal that tells lateral mesoderm or further out
BMP expressed laterally
the further out the type of mesoderm is the more BMP it sees
noggin expressed in notochord
midline BMP antagonist
further out you have BMP
cardiac mesoderm being lateral mesoderm is
controlled by bMP the mesdoerm in midline is supressed by BMP
endoderm retains BMP signalling in the pouches
what could distinguish the head end from the prospective trunk end
wnt signalling
high im primative streak
as it is a travelling uni as is the signalling
wnt inhibitors
cresent at rostral end
head end gets BMP and no wnt
trunk gets BMP and wnt
fgf
fgf is there to tell cells in mesoderm to keep on dividing and not engage in differentiation yet = contributes to keeping cells in secondary heart field = maintain cell pool into precursor pool
and is then recruited into the heart over time to make mature inflow and outflow
tells cells in prospective facial musculature to not go and differentiate yet
FGF signalling is involved in the specification of the extra embryonic blood items.
fgf and bmp can diffuse over a large distance notch cannot
notch signalling is membrane bound and cannot diffuse
involved when cells are talking to each other and trying to figure out what they are going to do,
whih way they are going to develop
neurogenesis
critical in saying which cells are allowed to differentiate or not
dorsal aorta - where endothelial cells can undergo endothelial haematopoietic transition.where endothelial cells can turn into blood cells, haematopoietic stem cells
angiogenesis
signal synergy
patterning of the somite and the induction of skeletal muscle
BMP + Noggin
cardiogenesis
BMP promotes
Wnt - inhibts
FGF where does it play a role where did we cover it what does it do with watch of these processes cell types
where does it come from where does it go to
why does the circulation system develop so early in the embryo
what happens to the cells that cant get oxygen
hypoxia transcription factor - alpha
