#12 the circulatory system (valves, circulatory routes (adult and fetus), coronary circulation)

two main groups of valves

1. atrioventricular valves (entry)

2. semilunar valves (exit)

2 atrioventricular valves

1. bicuspid valve

2. tricuspid valve

bicuspid (mitral) valve

• divides the left atrium and left ventricle

• only valve with 2 cusps (bi)

tricuspid valve

• divides the right atrium and the right ventricle

• 3 cusps (tri)

chordeae tendinae

attach the cusps of the valves to the cardiac muscle (papillary muscles)

what is the chordeae tendinae composed of

collagen connective tissue

what is the chordeae tendinae also referred to as

heart strings

how many cusps do semilunar valves have

3

aortic semilunar valves

divide the left ventricle and the aorta

pulmonary semilunar valves

divide the right ventricle and the pulmonary trunk

what is present in atrioventricular vales but not present in semilunar valves

chordae tendineae

• not used to anchor semilunar valves to the papillary muscles

the heart is located within the…

mediastinum

pericardium

double walled sac that surrounds the heart

3 layers of the pericardium

1. fibrous pericardium

2. serous pericardium

3. epicardium (visceral layer)

fibrous pericaridum

outermost layer

what tissue is the fibrous pericardium composed of

dense irregular connective tissue

what does the fibrous pericardium do

anchors the heart to surrounding tissue (eg. diaphragm) and large vessels (eg. aorta)

2 layers of the serous pericardium

1. parietal layer

2. visceral layer

parietal layer (serous pericardium) is fused to

fused to the fibrous pericardium

the fibrous pericardium and the parietal layer make up the

pericardial sac

visceral layer / epicardium is fused to

the surface of the heart

visceral layer / epicardium functions as

a key portion of the heart wall

pericardial cavity

area between the visceral and parietal layer

• fluid filled to provide lubrication

pulmonary circulation functions to

deliver and return blood to and from the lungs for oxygenation

systemic circulation functions to

deliver and return blood to and from the entire body

what organs are non-functional in the fetus

lungs and the liver

the non-function of the specific fetal organs causes…

a cap in their oxygen and nutrient requirements, therefore shunting blood AWAY

placenta

site of gas and nutrient / waste exchange between mother and fetus

the oxygen nd nutrients are provided to the fetus from

the mothers blood via the placenta

wastes and carbon dioxide produced by the fetus are delivered to

the mothers blood via the placenta

where is blood pressure higher in the fetal heart

right side (because the fetal lungs are non functional)

where is blood pressure higher in the adult heart

left side

where is the foramen ovale (fetal heart)

between the right atrium and the left atrium

what does the foramen ovale allow

exchange of blood between the two sites

when does the foramen ovale close

shortly after birth when pressure on left side of heart becomes higher

ductus Venosus

shunts blood away from liVer

where does the ductus Venosus divert blood to

diverts blood entering fetal circulation from the umbilical vein to the inferior vena cava

when blood enters fetal heart via the inferior vena cava it is diverted away from the lungs by…

the foramen ovale

where does the foramen ovale move blood to

moves blood directly from right atrium to the left atrium

what happens to blood that passes into the right ventricle and onto the pulmonary trunk (fetal circulation)

diverted into the aorta by the ductus arteriosus

how does blood enter maternal circulation

• from the aorta,

• mixed blood is returned to the placenta via umbilical arteries

coronary circulation

oxygenated blood delivered to myocardium to provide oxygen and nutrients to the cells

the 2 aortic branches

right and left coronary arteries

the left coronary arteries supply

left side of the heart with oxygenated blood

the left coronary artery branches into the

1. anterior interventricular artery

2. circumflex artery

anterior interventricular artery

supplies the inter ventricular septum and anterior wall of both ventricles

circumflex artery

supplies the left atrium and the posterior walls of the left ventricle

the right coronary artery branches into the

1. posterior interventricular artery

2. right marginal artery

posterior interventricular artery

supplies posterior ventricular walls

right marginal artery

supplies the myocardium

in coronary circulation, blood flows from the coronary arteries into the

arterioles

arterioles transition into

capillaries which supply the myocardium

capillaries transition into

venules

venules transition into

cardiac veins

cardiac veins transition into

the coronary sinus

the coronary sinus

drains deoxygenated blood into the right atrium to be sent to the lungs