It consists of Heart - Aorta - Arteries - Arterioles - Capillaries - Venules - Veins - Venae cavae - Pulmonary arteries - Lungs - Pulmonary veins - Blood
| Chapter 1 Cardiovascular System Information | Chapter 2 | Chapter 3 Blood Pressure - Arteriole - Blood Vessels | Chapter 4 Red and White Blood Cells |
Module 1 - Medical Transcription Tutorials
Aorta - Arteries - Capillaries
Chapter 2
AORTA
The largest artery in the human body, the aorta originates from the left ventricle of the heart and brings oxygenated blood to all parts of the body in the systemic circulation.
The course of the aorta
The aorta is usually divided into several segments. The portion above the diaphragm (in the thorax) is called the thoracic aorta and is sometimes further subdivided into the ascending aorta, aortic arch and descending (thoracic) aorta. The portion below the diaphragm (in the abdomen) is known as the abdominal aorta.
Thoracic aorta
The initial part of the aorta, the ascending aorta, rises out of the left ventricle, from which it is separated by the aortic valve. The two coronary arteries of the heart arise from the aortic root, just above the cusps of the aortic valve.
The aorta then arches back over the right pulmonary artery. Three vessels come out of the aortic arch,
Brachiocephalic artery,
Left common carotid artery, and
Left subclavian artery.
These vessels supply blood to the head, neck, thorax and upper limbs.
The aorta gives off several paired branches as it descends in the thorax. These
includes the
Bronchial arteries,
Esophageal arteries and
Intercostal arteries.
ABDOMINAL AORTA
The abdominal aorta travels down the posterior wall of the abdomen, the
abdominal aorta runs on the left of the inferior vena cava, giving off major
blood vessels to the gut organs and kidneys. There are many recognized variants
in the vasculature of the gastrointestinal system. The most common arrangement
for the abdominal aorta is to give off (in order) a
Celiac artery,
Superior mesenteric artery and
Inferior mesenteric artery.
The renal arteries usually branch from the abdominal aorta in between the celiac
artery and the superior mesenteric artery.
The aorta terminates by dividing into two branches, the left and right common
iliac arteries that branch to supply blood to the lower limbs and the pelvis.
Features
The aorta is an elastic artery, and as such is quite distensible. When the left
ventricle contracts to force blood into the aorta, the aorta expands. This
stretching gives the potential energy that will help maintain blood pressure
during diastole, as during this time the aorta contracts passively.
Diseases
Aneurysm of sinus of Valsalva
Aortic aneurysm
Dissecting aortic aneurysm
Aortic coarctation
Marfan’s syndrome
Inborn cardiovascular defects
ARTERY
Arteries are muscular vessels that carry blood away from the heart to the
tissues and organs of the body (The vessels which return blood to the heart are
veins).
The circulatory system is extremely important in sustaining life. Its proper
functioning is responsible for the delivery of oxygen and nutrients to all
cells, as well as the removal of carbon dioxide, waste products, maintenance of
optimum pH, and the mobility of the elements, proteins and cells, of the immune
system. In First World countries the two leading causes of death, myocardial
infarction and stroke, are each direct results of an arterial system that has
been slowly and progressively compromised by years of deterioration.
Description
The arterial system is the higher-pressure portion of the circulatory
system. Arterial pressure varies between the peak pressure during heart
contraction, called the systolic pressure, and the minimum, or diastolic
pressure between contractions, when the heart rests between cycles. This
pressure variation within the artery produces the pulse which is observable in
any artery, and reflects heart activity.
Anatomy
Arteries are composed of distinct layers of tissue; The innermost
layer, which is in direct contact with the flow of blood is the tunica intima,
commonly called the intima. This layer is made up of mainly endothelial cells.
Outside this layer is the tunica media, or media, which is made up of smooth
muscle cells and elastic tissue. The outermost layer is known as the tunica
adventitia or the adventitia, and is composed of connective tissue.
Types of arteries:
There are several types of arteries in the body:
Pulmonary arteries
The pulmonary arteries carry oxygen deficient blood that has just returned from
the body to the lungs, where carbon dioxide is exchanged for oxygen.
Systemic arteries
Systemic arteries deliver blood to the arterioles, and then to the capillaries,
where nutrients and gasses are exchanged.
The Aorta
The aorta is the root systemic artery. It receives blood directly from the left
ventricle of the heart via the aortic valve. As the aorta branches and these
arteries branch in turn, they become successively smaller in diameter,
successively down to the arteriole. The arterioles supply capillaries, which in
turn empty into venules.
ARTERIOLES
Arterioles, the smallest of the true arteries, help regulate blood pressure and
deliver blood to capillaries.
Arterioles and Blood Pressure
Arterioles have the greatest collective influence on both local blood flow and
on overall blood pressure. They are the primary "adjustable nozzles" in the
blood system, across which the greatest pressure drop occurs. The combination of
heart output (cardiac output) and total peripheral resistance, which refers to
the collective resistance of all of the body's arterioles, are the principal
determinants of arterial blood pressure at any given moment.
Capillaries
Though not considered true arteries, the capillaries are where all of
the important action happens in the circulatory system:
Functions of capillaries
These vessels have no smooth muscle surrounding them and have a diameter less
than that of a red blood cell; a red blood cell is typically 7 micrometers
outside diameter, capillaries typically 5 micrometers inside diameter. The red
blood cells must distort in order to pass through the capillaries.
This small diameter of the capillary provides a relatively large surface area
for the exchange of gases and nutrients.
What are the functions of capillaries:
In the lungs, carbon dioxide is exchanged for oxygen
In the tissues, oxygen and carbon dioxide and nutrients and wastes are exchanged
In the kidneys, wastes are released to be eliminated from the body
In the intestine nutrients are picked up, and wastes released
Chapter 3
Blood Pressure - Arteriole - Blood Vessels
Chapter 1
