module 6: embryology and development

CIRCULITORY SYSTEM

blood islands

small pockets of angioblasts dispersed throughout the mesoderm

what do angioblasts do??

build the walls of our blood vessels

endothelial cells originate from

endothelium lining

lines the inside of our blood vessels

HEART DEVELOPMENT

formation of primitive heart tubes

two endocardial tubes fuse together to make primitive heart tubes

what does the heart formation look like?

folding: primitive tubes are forced to fold due to limited space in growing coelom ventricles: move forwards and down

atrium: moves backwards and up s-curve: heart starts to curve in an "S" shape

primitive heart tube 4 main dilations

1. bulbus cordis: has formed into right ventricle, pulmonary trunk, and aorta

2. primitive ventricle: has formed into right ventricle and left ventricle

3. primitive atrium: has formed into right atrium and left atrium

4. sinus venous: has formed into superior vena cava, inferior vena cava, right atria, and the SA node

when do contractions of the heart begin

begin at the end of the third week

what does heart development look like

1. starting at day 20: we have two seperate endocardial tubes 

2. day 21: the two endocardial tubes fuse together causing the formation of primitive heart tube 

3. day 22: we now have fused enough to see the dilations of the heart - dilation closed to the arterial end is the bulbus cordis below that we have the primitive ventricle then the primitive atrium and then the sinus venosus

4. day 23: we have a bending of the tube due to the size of the coelom the heart will bend to find inside (ventricles move down and forward and atria move up and backwards

5. day 28: we see the orientation of the ventricles and the atria in their adult positions

exit point for blood is called what?

arterial end of heart

entrance point for blood is called what?

venous end of the heart

HEART DEVELOPMENT DAY 46 - 50

left ventricle

pump blood out to the body via the aorta

right ventricle

pump blood towards the lungs

how we get blood around the body in babies/adults

1. right atrium down into right ventricle

2. from right ventricle it will get pump out into the lungs where it picks up oxygen

3. returns back into the left atrium

4. left atrium into the left ventricle

5. left ventricle will pump the new oxygenated blood out to the body tissues

how we get blood around the body in fetus

• blood moves right from the right atrium into the left atrium due to the foramen ovale bypassing the lungs then will leave the left ventricle to the body tissue

• it will remain this way until the baby takes its first breath

circulation change at birth in fetus

fetus:

why does blood bypass the lungs? this is because the lungs are deflated

why do we bypass the liver? this is because the placenta is doing the job of the liver by filtering the blood

circulation change at birth in newborn

• cutoff from maternal oxygen supply and nutrient supply! so what happens?? well when they newborn is detached from the placenta it causes a drop in oxygen levels which is the first sign to the brain to take the first breath. once breathing occurs the lungs inflate and all the pressure on the blood vessels on the lungs go away, so the right side of the hearts blood pressure drops bc it can pump into the lungs. but left atrium increases which causes the septum primum onto the septum secundum which will seal off the two holes allowing for correct blood flow to the heart

what does the blood flow look like in our fetus heart before birth

1. blood moves from the pulmonary trunk to the ductus venosus diverts flow from the lungs

2. foramen ovale diverts  flow from lungs

3. ductus venosus diverts flow from the liver

4. oxygen rich blood to the fetus by the umbilical vein

5. oxygen poor blood is carried from the fetus through umbilical arteries 

what does the blood flow look like in our fetus heart after birth

1. air enters the lungs - forcing the blood into pulmonary arteries 

2. foramen ovale closes as pressure builds (now called the fossa ovalis)

3. ductus venosus degenerates becomes the ligamentum venosus 

4. umbilical vein degenerates and becomes the ligamentum teres

5. umbilical arteries degenerate becoming the medial umbilical ligaments 

RESPIRATORY SYSTEM

day 28

lungs begin

they begin as a a single midline evagination of the foregut

what do lung buds branch off trom??

the developing trachea 

branching of bronchi happens how many times?

• 17 times in fetus

• 24 times in adult (not another 24 - 18, 19, 21, 22, 23, 24)

fifth week of bronchi looks like what?

• esophagus

• trachea

• primary bronchus

• secondary bronchial buds

sixth week looks like what??

• esophagus

• trachea

• primary bronchus

• secondary bronchial buds

• tertiary bronchial buds

seventh week looks like what?

• trachea

• right primary bronchus (3 lobes)

  • superior lobe 

  • middle lobe

  • inferior lobe

• left primary bronchus (2 lobes) we need to accommodate the heart

  • left superior lobe

  • left inferior lobe

around the 8th week we develop what?

the plura membrane