The heart and fetal circulation

Pulmonary circuit

Right side of heart pumps blood to lungs (gets oxygenated), then it goes back to left side of heart

Systemic circuit

Left side of heart pumps blood to the body, then it goes back to the right side of the heart

Right side of heart

Deoxygenated blood enters FROM body and gets pumped TO lungs

Left side of heart

Oxygenated blood FROM lungs enters and gets pumped TO body

Right ventricle

Pump DEOXYGENATED blood to lungs through:

• pulmonary trunk; bifurcates into right and left pulmonary arteries

Left ventricle *thickest wall of heart chambers*

pump OXYGENATED blood to body through:

• aorta

• ascending aorta

• arch of aorta

• descending aorta

Left atrium

receive OXYGENATED blood from lungs through:

• 2 right pulmonary veins

• 2 left pulmonary veins

Right atrium

receive DEOXYGENATED blood from body through:

• superior vena cava

• inferior vena cava

• coronary sinus

Left auricle

Increases carrying capacity of heart

Veins toward the heart

• superior vena cava (SVC)

• inferior vena cava (IVC)

• pulmonary veins

Arteries away from heart

• Pulmonary trunk

• Pulmonary arteries

• Aorta

Superior vena cava

returns blood from thoracic wall, upper limb, head and neck

Inferior vena cava

returns blood from the abdomen, pelvis, and lower limb

Valves

prevent back flow of blood in chambers

Atrioventricular valves

prevent backflow into atria, found between atria and ventricles

• Tricuspid

• Bicuspid/Mitral

Semilunar valves

prevent backflow into ventricles, between ventricles and outflow arteries

• pulmonary semilunar

• aortic semilunar

Tricuspid valve (3) comes first

Between right atrium and right ventricle

Bicuspid valve (2) comes second

Between left atrium and left ventricle

Pulmonary semilunar valve

Between right ventricle and pulmonary trunk

Aortic semilunar valve

Between left ventricle and aorta

Systole

ventricles contract pumping blood out of heart

• tricuspid and bicuspid valves close

• “lub”

Diastole

ventricles relax so blood can fill them again

• tricuspid and bicuspid valves open

• pulmonary and aortic valves close

• “dub”

Layers of heart (superficial → deep)

Epicardium → myocardium → endocardium

Right atrium internal features

• pectinate muscle

• opening of coronary sinus

• fossa ovalis

Right ventricle internal features

• pulmonary trunk

• pulmonary semilunar valve

• trabeculae carnae

• tricuspid valve

• chordae tendinae

• papillary muscle

Left ventricle internal features

• aorta

• aortic semilunar valve

• trabeculae carnae

• papillary muscle

• bicuspid valve

• chordae tendinae

Closed valves

• maximal blood flow during relaxation (diastole)

• contraction of myocardium compresses coronary arteries

Open valves

• very little blood flow when contracting (systole)

• entrances to coronary circulation are partially blocked by cusps of open valves

Arterial coronary circulation

base of aorta → R. coronary artery → R. marginal artery AND posterior interventricular artery

base of aorta → L. coronary artery → Circumflex artery AND anterior interventricular artery

Venous coronary circulation

Small cardiac vein → coronary sinus → right atrium

Middle cardiac vein → coronary sinus → right atrium

Great cardiac vein → coronary sinus → right atrium

R. Marginal Artery

Small cardiac vein

Posterior Interventricular Artery

Middle cardiac vien

Anterior interventricular artery

Great cardiac vein

Intrinsic conduction system

cardiac muscle of heart is able to depolarize and contract without impulses from the nervous system

Fetal circulation

• non-functioning lungs

• can not provide its own nutrients

• can not remove its own waste

• must use mothers circulation to compensate for deficiencies

Placenta

develops in the uterus alongside the fetus to allow maternal and fetal blood to communicate

Umbilical vein (1)

• brings oxygen and nutrients TO the fetal heart, oxygenated by mothers lungs

• passes through primitive liver, carrying blood to IVC

• regresses to form ligamentum teres (inferior edge of liver)

Umbilical arteries (2)

take deoxygenated blood AWAY from the fetal heart

Foramen ovale (fetal circulation)

• hole that shunts blood from right atrium to left atrium to bypass lungs

• small amount of blood to nourish tissues

• closure forms fossa ovalis

Ductus arteriosus (fetal circulation)

• shunts blood that made it to the left pulmonary artery to the aorta

• closure forms ligamentum arteriosum

Order of intrinsic conduction system

Sinoatrial node → atrioventricular node → atrioventricular bundle (bundle of His) →Bundle branches → Purkinje fibers

Apex of heart

points to left hip

Pectinate muscles

muscles found along the wall of a portion of atria