Lec 4 Flashcards
Blood pathway
Vascular Development (begins when)
3-4 weeks after conception
What cells differentiate into vessels
mesodermal
Vasculogenesis vs Angiogenesis
vasculo - formation of arteries and veins
ONLY DURING EMBROYONIC DEVELOPMENT
angiogenesis; formation of vascular branches from existing blood vessels OCCURS DURING EMBRYONIC AND THROUGHOUT LIFE
3 layers of blood vessels
tunica externa (adventitia) - outer connective tissue
tunica media - middle smooth muscle
tunica intima - inner endothelial layer
large elastic arteries
Aorta, left common carotid artery artery
tunica media
elastic fibers to allow expansion and recoil
constant flow of blood during diastole
Medium muscular arteries
femoral artery, axillary artery
tunica media
smooth muscle fibers to allow for regulation of diameter and control blood flow to different parts of the body
Small arteries and arterioles
controls the filling of capillaries
Distinguishing features of veins
larger and more compliant than arteries
thin walls (especially tunica media)
large lumens - larger blood reservoir
*one way valves
One way valves :
typically located in veins inferior to the heart
facilitate blood flow toward the heart
affected by autonomic nervous system and skeletal muscle pump
What does the autonomic nervous system regulate
BP and peripheral resistance
What are the sympathetic and parasympathetic roles in circulation?
sympathetic - increases HR and causes vasoconstriction
parasympathetic - decrease HR and cause vasodilation
Embryo: when does the heart develop
3 weeks after conception
recognizable structure after 20 days - heart tube that begins to elongate
When does circulation begin?
4 weeks gestation - rhythmic pulsations of primitive heart tube
Gestation
3 weeks
4 weeks
7 weeks
week 3; heart and vessels develop
week 4: heart begins to beat and pump blood
week 7: heart forms into 4 chamber structure
Shunting systems (prenatal)
small passages for blood to travel through in order to bypass body parts that are not yet developed
shunting systems; foramen ovale
Ductus arteriosus
Ductus venosus
foramen ovale; R atrium to L atrium
ductus arteriosus; R pulmonary artery to aorta
ductus venosus; inferior vena cava to umbilical vein
What happens to shunting systems?
close and form new structures
foramen ovale
fossa ovalis
ductus arteriosus
ligamentum arteriosum
umbilical venosus
ligamentum teres
ductus venosus
ligamentum venosum
umbilical arteries
lateral umbilical ligaments
_ % of live births have congenital heart disease
1
leading non-infectious death in 1st year
CV development; infancy and childhood
left side of heart becomes predominant
left ventricle wall becomes twice as thick by adulthood
heart changes from horizontal to vertical orientation with lung expansion
heart size increases with body weight
Heart volume (infancy and childhood)
40 mL at birth
80 mL 6 months
160 mL at age 2
Ratio of heart voume to body weight
remains constant = 10 mL/kg of body weight
Cardiac muscle changes in infancy and childhood
Myocytes; increase in cross sectional area and number of myofibrils in cross-section
increased contraction of myocyte
myofibrils mature and change from a random orientation to being oriented in the same direction
stroke volume = increased efficiency
NO INCREASE IN THE NUMBER OF MYOCYTES
Vascular changes infancy and childhood
increased heart vascularization
at birth - 1 vessel for every 6 muscle fibers
adulthood 1:1 ratio
Fetal blood has more Hb and less O2 saturation
As infants lungs begin to function, blood has less Hb and more O2 saturation