Micro 10

why when embryo begins to develop does the cardiovascular system develop first?

the early embryo can be sustained by diffusion but as get larger cant be supported by diffusion as distance nutrient sneed to cross get larger so a circulatory system become snecessary before organs mature so they can be supplied

is the cardiovascular system the first functional system in an embryo?

yes

what does the mesoderm give rise to for cardiovascular?

vascular and cardiac mesenchymal precursors

what do angioblastic cells do?

contribute to blood vessel formation

what call process of blood vessel formation?

angiogenisis

what does early vessel formation develop?

a network that later expands and remodels

what is the cardiogenic field?

horse shoe shaped cardiogenic region in embryonic disc that lies cranial and lateral to neural plate that has blood forming cavities in the visceral mesoderm that will coalesce and form the primitive heart, blood vessels and blood cells

what does embryonic folding change?

the position of the cranial field

what are the folding and steps that the cranial cardiogenic field undergoes in order?

the field is brought caudo-ventrally then the developing aorta approaches the cardiac tube which is then brought to a ventral position to the dorsal aorta and the vitelline veins. The caudal part of the cardiogenic tube fuses with the vitelline veins and the two sides of the cardiac tube fuse as well. The paired cardiac primordia move towards the midline and the dorsal and ventral aorta connect.

what do dorsal and ventral aorta connect?

the early circulation

what does fusion of the dorsal and ventral aorta establish?

a primitive heart tube

what occurs to the primitive heart tube?

the tube is initially straight but then undergoes elongation and looping resulting in the bulbus cordia, primitive ventricle and atrium acquire new spatial relationship and the establishment of the arrangement needed for subsequent septation to form heart chambers

what is a primitive atrium?

anterior/trabeculated regions of the right and left atria

what is primitive ventricle?

much of the left ventricular trabeculated region

what is the bulbus cordis?

the right ventricle and ventricular outflow region in embryo

what is the truncus arteriosus?

the aorta and pulmonary trunk after partitioning

what is the sinus venous?

the smooth part of the right atrium and associated venous structures

what do endocardial cushions partition?

the common atrioventricular canal

what does cushion tissue contribute to?

the cardiac septa and atrioventricular junction

what must partitioning preserve?

suitable fetal blood flow during development

what is the steps of partitioning to form heart?

1. the primary atrial septum/septum primum and intraventricular septum begins to develop and the septum primum grows towards the endocardial cushions forming ostium primum that is a foramen that premits interatrial blood flow

2. the ostium primium narrows and closes and the ostium secundum forms and preserves blood flow allowing right to laeft atrial passage

3. the second atrial septum/septum secundum grows to the right of septum primum creating the fetal foramen ovale connecting the right and left atria

4. the interventricular septum growing upwards from the ventricular floor and fuses with the endocardial cushion seperating right and left ventricles

what does ostium primum initially permit?

interarterial blood flow

when does the ostium primum narrow?

narrows as the septum primum approaches the cushions

what does the septum primum form adjacent to the foramen ovale?

a mobile flap

what allows blood to flow from right atrium to left atrium through foramen oval in fetus?

the fetal right atrial pressure

what closes the formen ovale after birth?

firs breaths after birth lower pulmonary vascular resistance and the left atria pressure rises switching the sides of the pressure gradient which forces the mobile flap formed by septum primum closed

does functional closure of the foramen ovale precede anatomical fusion?

yes

what does the truncus arteriosus divide into?

the aorta and pulmonary trunk

what establishes the normal crossing pattern of thevessels of the heart?

the spiral development of the aorticopulmonary septum

where is right ventricular blood directed to?

pulmonary trunk

where is the left ventricular blood directed to?

aorta

what can alter aorta and pulmonary trunk alignmnet?

abnormal outflow sepation

what happens if complete transposition of the great vessels occurs?

the aorta arises from the right ventricle and then the deoxygenated blood will flow to body while oxygenated flows to lungs

what do embryonic aortic arch arteries form paired connections with?

dorsal aortae

what occurs to selected arch segments?

they persit, regress or remodel

what can abnormal remodeling of arch segments do?

alter the arrangement of the great arteries which can have bad outcomes

prior to birth what is fetal circulation designed for?

the in utero aqueous enviroment where the placenta oxygenates fetal blood

what are the 3 essential fetal shunts? what does each do and where located?

ductus venosus: connects the umbilical vein to inferior vena allowing oxygenated blood to bypass liver

foramen ovale: located between atria allows blood to flow from right atrium to left atrium so it doesnt have to go to lungs since cant get oxygen from lungs in utero

ductus arteriosus: connects pulmonary arteries and aorta allowing blood to flow from pulmonary artery into aorta so doesnt have to go to lung since dont get oxygen in lungs while in utero

what oxygenates fetal blood?

the placenta

where does oxygenated umbilical venous blood return and what occurs following this?

blood returns to the fetus and reaches the caudal vena cava where goes into right atrium and then a substantial portion of blood enters the left atrium through the foramen ovale

what does the left fetal heart supply?

the systemic arterial circulation

where does gas exchange occur in fetus?

placenta not alveoli

what is pulmonary resistance like in fetus? what does this do to blood flow?

high pulmonary resistance so blood flow to lungs is limited since no gas exchange occurs there

what do the fetal shunts allow blood to bypass?

the liver and pulmonary circulation

do different streams of fetal blood have different oxygen content?

yes

what steps occur in order when transition from fetal to neonatal circulation?

1. lung expansion decreases pulmonary vascular resistance

2. placental circulation is lost when umbilical vessels close

3. left atrial pressure rises which functionally closes the foramen ovale

4. flow through ductus arteriosus declines as it constricts

whata re the 3 postnatal remnants of the fetal shunt?

ligamentum venosum- remnant of ductus venosus

fossa ovalis- remnant of foramen ovale closure

ligamentum arteriosum- remnant of ductus arteriosus

which closure precedes the other in foramen ovale closure?

functional closure precedes fibrous anatomical closure

what are the 6 steps of the essential sequence of cardiac development?

1-cardiogenic field and cranial mesodermal precursors

2-heart tube from the midline fusion of primordia

3-looping for reorientation of early chambers

4-septation into atria and ventricles

5-form the great vessels (aorta and pulmonary trunk)

6-close shunt and perfuse lungs at birth

what does the heart do?

create pressure and circulate blood

what do arteries do?

distribute blood

what do veins do?

return blood to heart

what recover tissue fluid?

lymphatics

what do capillaries do?

exchange nutrients and waste

whata re 4 main functions of cardiovascular system?

-maintain adequate blood flow and cardiac output

-deliver oxygen, nutrients, hormones, electrolytes and water to tissues

-remove carbon dioxide and other metabolic waste products

-support thermoregulation and normal renal perfusion

what is pulmonary circulation?

from heart to lungs and back to heart

what is systemic circulation?

from heart to body/tissue back to heart

what is the first organ to form in embryo?

heart

who have 4 chambers of their heart?

mammals and birds

what 3 layers compose the heart in order from inside to outside?

endocardium

myocardium

epicardium

what is another way can call epicardium?

visceral pericardium

what layer/tunic find purkinje fibers?

endocardium

what does the endocardium form?

inner lining and valves

what layer of heart is in direct contact with blood?

endocardium

what is the innermost surface of endocardium?

endothelial cells (stratified squamous)

what is the endocardium equivalent to in blood vessels?

tunica intima

what layer of heart is important in hemostasis?

endocardium

what are the 3 layers of endocardium?

1. endothelium

2. basal lamina (connective tissue)

3. subendocardium

what is subendocardium?

subendothelial connective tissue that also contains purkinje fibers and some of the conductive system

what are purkinje fibers?

fast conducting cardiac muscle cells that rapidly transmit electrical impulses to coordinate heart contractions

what are myofibrils like of purkinje fibers?

few myofibrils and are located on periphery

do purkinje fibers have lots of glycogen and mitochondria?

yes

do purkinje fibers have t tubules?

no