Circulation 3

Circulation 3

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Circulation 3...

Circulation 3:

PATH OF GENERAL CIRCULATION

The aorta is the largest artery in the body. There are three branches from this vessel brachiocephalic , the left common carotid, and the left subclavian arteries. These arteries and their branches carry blood to the arms, head and neck.

Many arteries descend off the aorta carrying oxygenated blood throughout the body. The first branch off the descending aorta is the coronary artery, carrying blood to the muscle of the heart.

As the aorta descends it sends off additional branches to the walls of the body, stomach, intestines liver, pancreas, spleen, kidneys, reproductive organs, urinary bladder, legs and so on.

This is where hormones, nutrients, O2 and other materials are transferred from the blood to the tissues. In turn, metabolic waste such as CO2 and nitrogen are picked up by the blood.

Some circulatory routes within the general circulation are called by special names.

Coronary circulation

Portal circulation

Fetal circulation

CORONARY CIRCULATION

This type of circulation brings oxygenated blood to the heart and is a part of the general circulation.

Two branches that are the right and left coronary arteries. As we know these branches encircle the heart muscle with many tiny branches that go to all parts of the heart muscle itself.

PORTAL CIRCULATION

Is also a branch of the general circulation. Veins from the pancreas, stomach, small intestine, colon, and spleen empty their blood into the portal vein in the liver. It is very important that the venous blood make a detour through the liver before returning to the heart.

This is important because the liver removes excess glucose from the blood and converts it into glycogen to use for exercise or for long periods of work. The liver also detoxifies or neutralizes many toxins or drugs, it also breaks down hormones that are no longer being useful to the body.

Deoxygenated venous blood leaves the liver through the hepatic portal vein which then in turn carries it to the vena cava then throughout he path of the cardiac circulation (right atrium)

Red blood cell debris is carried with bile from the liver into the intestines and removed through feces or bowel movements.

FETAL CIRCULATION

Circulation in the body before birth differs from circulation after birth. In the fetus, the placenta acts like the lungs and therefore cardiopulmonary circulation is not necessary. The fetus secures oxygen and food from maternal blood instead of from it's own lungs or digestive organs.

Specialized blood vessels carry the fetal blood to the placenta where the exchange occurs and then it returns to the fetus. This is done through three vessels that are part of the umbilical cord. These vessels are 2 small umbilical arteries and a single but much larger umbilical vein.

The ductus venosus is actually a continuation of the umbilical vein. It serves as a shunt or a diversion allowing most of the blood returning from the placenta to bypass the immature liver of the fetus and empty directly into the inferior vena cava. Two other structures allow the most of the blood to bypass the developing lungs (which remain collapsed until birth). The foramen ovale shunts blood from the right atrium directly into the left atrium and the ductus arteriosis connects the aorta and the pulmonary artery.

At birth the special fetal blood vessels and shunts become nonfunctional.

When the newborn takes it's first deep breaths, the circulatory system has an increase of pressure as a result of this increase in pressure the foramen ovale , umbilical vessels, ductus venosus and the ductus arteriosus undergo a rapid collapse. This makes this structures no longer functional but better yet no longer needing to be functional. The normal cardiopulmonary circulation then begins.

There are several disorders that can result from the failure of the circulatory system to shift from the fetal route of blood flow at the time of birth.

The ductus ateriosus may fail to close and then allow deoxygenated blood to bypass the lungs.

There is also a condition where the foramen ovale may fail to close and remain as s “hole” in the heart that allows blood to bypass the pulmonary circulation. The baby will become cyanotic due to the lack of O2 in the systemic arterial blood.

There is a condition in infants also called “tetrology of Fallot”. This disorder, named after a French physician consists of four defects; pulmonary stenosis, ventricular septal defect malposition, of the aorta and right ventricular hypertrophy or an increase in the size of the right ventricle. This is a congenital malformation or one that is present from birth. The primary symptoms of this are failure to thrive, cyanosis especially when crying and generally poor development

CIRCULATORY SHOCK

This term refers to the failure of the circulatory system to provide O2 to the tissues so that it may adequately deliver O2 to the tissues of the body.

Left untreated circulatory shock may lead to death. There are a variety of causes:

Cardiogenic- results from any type of heart failure such as after an MI, heart infection, or other heart conditions. If the heart fails as a pump, blood flow to the tissues decreases or stops.

Hypovolemic- results from loss of blood or low blood volume. This results in hypotension and reduced blood flow to tissues.

Septic shock results from complications of septicemia or a condition that results from infectious agents releasing toxins into the blood stream. One type of septic shock is TSS or toxic shock syndrome which usually results from a staph infection in the vagina of menstruating women that ultimately spreads to the blood stream