CV and RESP system Flashcards
how does the early embryo access nutrients and oxygen and get rid of waste products?
through placenta
what does the heart form from?
from mesoderm around 18 to 19 days after fertilisation
3 germ layers of heart are?
ectoderm (top)
mesoderm (middle)
endoderm (bottom)
cardiogenic area or plate?
within mesoderm, a horseshoe-shaped area develops
where does the cardiogenic plate move to?
moves ventral to the pharynx as the head process grows upward and outward
what is the cardiogenic plate formed from?
from cardiac myoblasts and blood islands (forerunners of blood cells and vessels)
within each side of the cardiogenic area, what forms?
an endocardial tube forms (lined by endothelial cells)
where do the endocardial tubes fuse?
they fuse midway along their length, forming the tubular heart or cardiac tube
a single tube is formed with an arterial and a venous end
atria are the?
blood receiving chambers
ventricles are the?
blood pumping chambers
what is the auricle?
it is the blind ear-shaped pouch of the atrium
as endocardial tube lengthens, what happens?
it loops on itself
this puts the bulbus cordis (right ventricle) beside the ventricle (left) and the atrium dorsal to the ventricle
what happens to the venous return during morphogenesis?
it is shifted to the right
the larger right sinus venosus becomes the right atrium (embryonic atrium becomes auricles)
the smaller left sinus venosus joins the future right atrium as the coronary sinus venosus
describe the formation of cardiac chambers:
partitions form a 4-chambered organ. The septa that form:
divide the atrium and ventricle (cardiac cushions/septum intermedium)
divide the atrium (septum primum and secundum)
divide the ventricle (interventricular septum)
divide the outflow tracts (aortico-pulmonary septum)
Why is it relevant that the foramen secundum forms BEFORE the foramen primum
closes?
so we can create valve
you have two septums
formation of aorta and pulmonary valves:
form from swellings of sub-endothelial mesenchymal tissue
then remodelled to form thin walled cusps
formation of the A-V valves?
form from the proliferation of mesenchymal tissue at the rim of the AV opening, attached to the myocardium
valves remodeled, but remain anchored by muscular strands to the ventricular walls
formation of blood vessels: how many stages?
2 stages
what are the two stages for the formation of the blood vessels?
vasculogenesis and angiogenesis
vasculogenesis?
formation of blood vessels form blood islands
vessel formation happens when island vesicles coalesce, sprout buds and fuse to form vascular channels
angiogenesis?
budding of new vessels from existing vessels
begins with blood island formation in splanchnic mesoderm of the yolk sac and allantois
formation of aortic arches?
bilaterally, ventral & dorsal aortae are connected by up to six aortic arches
what is the first aortic arch?
the cranial fusion between dorsal aortae and cardiac tubes becomes the 1st aortic arches
in total - 6 pairs of aortic arches will develop
what does the aortic arch give rise to?
gives rise to major vascular structures
3rd aortic arches formation?
internal and common carotid arteries
left 4th aortic arch formation?
definitive aortic arch
right 4th aortic arch formation?
proximal part of right subclavian artery
6th aortic arches formation?
pulmonary arteries (and ductus arteriosus)
what are foetal shunts?
allow blood to bypass the lungs and liver
give examples of foetal shunts?
foramen ovale (between right and left atria)
ductus arteriosus (between pulmonary trunk and aorta)
Ductus venosus (between umbilical vein and caudal vena cava)
where does the respiratory diverticulum arise from?
from foregut endoderm and goes on to form:
epithelial lining of trachea
larynx
bronchi and alveoli
where does the lung bud from?
from the left and right principal bronchi - which divide into ever-smaller branches, down to alveolar ducts and alveoli
what are lungs filled with during development?
filled with fluid during development
mostly glandular secretions, some amniotic fluid
foetal cardiovascular system consist of?
two large left and right umbilical arteries
and the umbilical vein
location of two large left and right umbilical arteries?
extending from the caudal end of the abdominal aorta
umbilical vein - where does it go?
after passing through the capillary bed in the placentae
this highly oxygenated blood returning from placentae to the umbilical vein bypasses liver sinusoids - ductus venosus
how does foetal heart allow blood to bypass lungs?
foramen ovale - between the two atria
ductus arteriosus - between the aorta and pulmonary trunk
(in foetus pressure in the right side is greater than left)
what is tetralogy of fallot?
malformation of aortico-pulmonary septum (enlarged aorta and pulmonary stenosis) + ventricular septal defect
what are common congenital conditions?
inter-atrial septal defects (e.g. patent foramen ovale)
inter-ventricular septal defects
congenital venous shunts (e.g. persistent ductus venosus)
vascular ring anomalies (e.g. persistent or additional aortic arches)
pulmonary or aortic stenosis
abnormal positioning of the heart (e.g. ectopic heart in the neck - Ectopia cordis)
What are the different parts of the heart tube?
truncus arteriosus
bulbus cordis
ventricle
atrium
sinus venosus
what does the truncus arteriosus part of the heart tube develop into?
it develops into aorta and pulmonary trunk
what part of the heart does the bulbus cordis part of the heart tube develop into?
right ventricle
what part of the heart does the ventricle part of the heart tube develop into?
the left ventricle
what part of the heart tube does the atrium of the heart tube develop into?
cranial portion of both left and right atria/auricles
what part of the heart does the sinus venosus part of the heart tube develop into?
remains bifurcated, a paired area where veins drain
larger right sinus venosus and smaller left sinus venosus
It develops into the caudal portion of right atrium
what are the cardiac cushions?
at the atrioventricular region, two masses of cardiac mesenchymal tissue form
what happens to the cardiac cushions?
they extend towards each other and fuse
what do the fused cushions form?
they form the septum intermedium
what does the septum intermedium do?
it separates the atrio-ventricular canal into right and left atrio-ventricular openings
what is the primary septum?
it is a membranous fold that grows down from the dorsal wall of the atrium towards the endocardial cushions
what does the primary septum divide?
it divides into left and right atria
what is the primary foramen?
it is when the primary septum leaves a small hole near the cushions that will eventually close
before the primary foramen closes - what happens?
before it closes, a second hole forms in the primary septum via apoptosis (secondary foramen)
what is the secondary septum?
it grows from the cranial wall of the right atrium toward the caudal wall
what is the foramen ovale?
the septum remains incomplete and its free edge forms the boundary of an opening - called the foramen ovale
what does the primary septum act like?
it acts like a valve against the muscular secondary septum
what do the expanded part of the bulbus cordis and the ventricle form?
they form a common chamber
what are the ventricles marked by externally?
they are marked by a groove (the interventricular sulcus)
internally, what are the ventricles marked by?
they are marked by a fold (primordial interventricular septum)
what does the embryonic ventricle develop into?
into the left ventricle
what does the embryonic bulbus cordis develop into?
into the right ventricle
as the ventricles expand, what happens to the interventricular septum?
the interventricular septum elongates towards endocardial cushions
what contributes to proper closure of the interventricular septum?
growths from the spiral septum and endocardial cushions both contribute to proper closure of the interventricular septum
what does the truncus divide to form?
it divides to form two outflow tracts
what are the two outflow tracts that the truncus arteriosus divides to form?
the aortic trunk and pulmonary trunk
what is the spiral septum?
this is when ridges appear along the lumen wall, they grow inward and merge to create the spiral septum (aortico-pulmonary septum)
what happens as a result of the spiral septum?
the aorta and pulmonary trunk spiral around one another
what contributes to proper closure of the interventricular septum?
growths from the spiral septum and endocardial cushions both contribute to proper closure of the interventricular system
what aortae develop in the embryo?
paired ventral and dorsal aortae develop in the embryo
due to embryo folding, what happens to the dorsal aorta?
the dorsal aorta ends up dorsal to the cardiac tube
where do the paired ventral aorta receive blood from in order to what?
from truncus arteriosus fuse to form the the adult braciocephalic trunk
what develops in the embryo that leads to the formation of arteries?
paired ventral and dorsal aortae develop in the embryo
where does the dorsal aorta end up and why?
ends up dorsal to the cardiac tube due to embryo folding
paired ventral aorta receives blood from where?
from truncus arteriosus and fuses to form the adult brachiocephalic trunk
to help with the formation of arteries - what do the aortae fuse with?
it fuses with the cardiac tubes (and the cardiac tubes fuse with the vitelline veins (1) caudally)
what is found caudal to the aortic arches?
the paired dorsal aortae merge to form a single descending aorta - as found in the adult
how many veins drain into the heart tube?
three paired veins drain into the heart tube
what are the three paired veins that drain into the heart tube?
vitelline veins
umbilical veins
common cardinal veins
what do the vitelline veins do?
they return poorly oxygenated blood from the yolk sac
what do umbilical veins do?
they carry well-oxygenated blood from the primordial placenta
what do the common cardinal veins do?
they return poorly oxygenated blood from the body of the embryo
foetal blood pressure is?
it is low
what powers the foetal pressure?
it is powered by the foetal heart (not by mum)
lots of blood spread out in placenta
what is blood shunted right to left by in the foetal cardiovascular system?
by the foetal ovale
and ductus arteriosus
why is blood shunted right to left in the foetal cardiovascular system?
in order to by pass lungs
describe the lungs of the foetus:
lungs are non-functional collapsed
no air to breathe
describe the foetal pulmonary circulation:
it has a high resistance
vessels here are collapsed
describe the foetal systemic circulation:
it has low resistance
the placenta is a low-resistance area
what must placentae receive?
a large proportion of foetus’s circulating blood
what does contraction of umbilical arteries and veins do?
it prevents bleeding and forces placental blood into foetal circulation
describe what happens when there is contraction of musculature in ductus arteriosus:
physiological shunt closure sends blood to lungs
anatomical closure can take 2 months
in which species may you hear transient cardiac murmurs?
may hear transient cardiac murmur in foals, calves pigs
what allows the ductus arteriosus to close gradually?
reduced venous return through the umbilical vein and ductus venosus
what happens when the foramen ovale closes?
there is increased venous return from lungs to left atrium
reduced venous flow from placenta to right atrium
pressure in left > right, forces septum primum against septum secundum
anatomical closure of foramen ovale takes how long?
takes up to a year in most species
anatomical closure of the ductus arteriosus takes how long?
can take 2 months
what happens to the non-functional vessels at birth?
they regress, become ligaments e.g. umbilical veins - round ligament; ligament arteriosum
why does fluid leave lungs at birth?
compression of thorax squeezes fluid out of lungs
what happens to the lungs at birth?
lungs inflate
pulmonary vascular resistant becomes lower
when does the foramen ovale close?
at birth
when does contraction of umbilical arteries and veins occur?
at birth
when does contraction of musculature in ductus arteriosus occur?
at birth
when does the reduced venous return through the umbilical vein and ductus venosus which allows the ductus arteriosus to gradually close - occur?
at birth
compare the pressure of the CV/resp systems of a foetus compared to a neonate:
low pressure system for a foetus
high pressure system for a neonate
what is the direction of blood shunting for a foetus compared to a neonate?
right to left shunting for a foetus
left to right blood flow for neonate
describe the functionality of the lungs for a foetus compared to a neonate:
lungs non-functional in a foetus
lungs are functional in a neonate
describe the pulmonary resistance of a foetus compared to a neonate:
Increased pulmonary resistance in a foetus
decreased pulmonary resistance in a neonate
describe the systemic resistance in a foetus compared to a neonate:
decreased systemic resistance in a foetus
increased systemic resistance in a neonate
meaning of congenital?
having a trait/condition from birth
what are common congenital conditions of the heart?
inter-atrial septal defects (e.g. patent foramen ovale)
inter-ventricular septal defects
congenital venous shunts (e.g. persistent ductus venosus)
vascular ring anomalies (e.g. persistent or additional aortic arches)
aortic or pulmonary stenosis
abnormal positioning of the heart (e.g. ectopic heart in the neck - Ectopia cordis
