Introduction to Cardiovascular System Flashcards
Cardiovascular system
1st major organ system to function in embryo
All blood vessels begin as what?
Condensations of mesodermal mesenchyme (blood islands) during week 3
Blood islands will rise to what?
Blood cells
Vessels
Heart
Blood islands that would become the heart form where?
In splanchnic mesoderm around future head and neck of embryonic disc (cariogenic region)
When embryonic heart reaches the thorax, it is what?
A pair of endothelial tubes in the body’s midline that fuse into a single tube on Day 20
On what day does the heart start pumping?
Day 22
Are the earliest heart chambers paired or unpaired?
Unpaired
What are the chambers from tail to head?
sinus venosus, atrium, ventricle, and bulbs cordis
Sinus Venous– will become…
- Smooth-walled part of R atrium, coronary sinus, and SA node
- Also contributes to posterior wall of L atrium
Atrium gives rise to?
Ridged parts (pectinate muscles of R and L atria
Ventricle
Strongest pumping chamber
- gives rise to L ventricle
Bulbus cordis
The truncus arteriosus (4a), gives rise to R ventricle, pulmonary trunk, and 1st part of aorta
What shape does the heart take on when the 4 chambers appear?
S- shape
- ventricle moves caudally and atrium cranially. Bending occurs due to rapid growth of ventricle and bulbus cordis
What happens as a result of cardiac looping during week 4?
The heart folds on itself and assumes its normal position in left part of the Thorax with atria posterior and ventricles located in a more anterior direction
What happens by month 2?
The heart is divided into the 4 definitive chambers by formation of midline atrial and ventricular septa and valves
- Develop from regional thickenings of endocardium: endocardial cushions
During fetal development, what are the 3 early vascular systems?
Intraembryonic
Vitelline
Placental
Intraembryonic system
Dorsal aorta supplies blood to embryonic tissues
Cardinal veins return poorly oxygenated blood from body of embryo into heart tube
Vitelline System
Vitelline vessels supply blood to and drain blood from yolk sac
What system contributes to blood supply of gastrointestinal tract?
Vitelline system
Umbilical/Placental system
Paired umbilical arteries deliver deoxygenated blood and fetal waste products to placenta
Well-oxygenated blood and nutrients from placenta are carried to fetal heart tube via an unpaired umbilical vein
By when are all the major vessels formed?
Month 3 of development
What are the differences between fetal and postnatal circulation (O2 and nutrients access)
During pregnancy, the placenta provides both O2 and nutrients to fetus
Therefore, fetal circulation is different in that it bypasses lungs and most of the liver
Umbilical Vein
Provides oxygen
- rich blood from placenta
Some highly oxygenated blood is shunted through…
Through the liver to IVC via ductus venosus
Ductus venosus
Drains into IVC where oxygen-rich placental blood mixes with oxygen-poor blood returning to heart from caudal region of fetal body
Where do the IVC and SVC drain moderately oxygenated blood into?
Right atrium
Blood passage to nonfunctioning lungs is limited by what?
Foramen ovale and ductus arteriosus
Blood from the right atrium passes into the left atrium via what opening?
The foramen ovale in the inter-atrial wall
From the left atrium, where does the blood continue?
To the left ventricle and aorta to supply the body
Does blood from the right atrium reach the right ventricle and pulmonary trunk?
Some blood only
What is the name for the shunt that diverts blood from the pulmonary trunk to the aorta?
Ductus arteriosus (since the lungs are nonfunctioning)
What happens to the ductus arteriosus?
Constricts and closes which persists as ligaments arteriosum
Clamping of umbilical cord causes what?
Umbilical vein to constrict- persists as ligamentum teres (“round ligament”) that anchors liver to body wall
Ductus venosus to close- persists as ligaments venous on inferior surface of liver
Umbilical arteries to close- persist as medial umbilical ligaments (folds in anterior abdominal wall inferior to navel)
What causes the 2 valve flaps of the oval foramen to close? What comes of it?
Oxygenated pulmonary blood pours into the left atrium which raises pressure, the structure known as fossa ovalis in the right atrium persists
What constitutes to the largest category of birth defects?
Heart and vascular abnormalities; present in 1% of live born infants- 30% of heart defects occur in infants with other major malformations
Approximately 2% of heart defects are due to what?
Environmental agents, which most have multifactorial causes
What is the most common congenital heart malformation?
Ventricular Septal Defects (VSDs)
- Occur in isolation in 12/10,000 births (80% concern muscular portion of septum and resolve as child grows)
What occurs when bulbs cordis does not divide properly?
Transposition of the great vessels
- As a result, aorta originates in the right ventricle and the pulmonary trunk from the left ventricle
What has 4 cardiovascular alterations?
- Pulmonary infundibulum stenosis
- Large IV septal defect
- An overriding aorta arising directly above the septal defect
- Right ventricular wall hypertrophy due to right side pressure
