Quantcast Pulmonary Cycle. - Basic Human Anatomy

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
a. General. The human cardiovascular circulatory system is described as a
closed, two-cycle system.
(1) It is closed because at no place is the blood as whole blood ever outside
the system.
(2) It is two-cycle because the blood passes through the heart twice with
each complete circuit of the body. In the pulmonary cycle, the blood passes from the
right heart, through the lungs, and to the left heart. In the systemic cycle, the blood
passes from the left heart, through the body in general, and returns to the right heart.
(3) It is common for an area of the body to be supplied by more than one
blood vessel so that if one is damaged, the others will continue the supply. This is
known as collateral circulation. However, there are situations, such as in the heart and
the brain, where a single artery supplies a specific part of a structure. Such an artery is
called an end artery. When an end artery is damaged, that area supplied by it will
usually die, as in the case of the coronary artery (para 9-7c) above or in the case of a
"stroke" in the brain.
b. Pulmonary Cycle. The pulmonary cycle begins in the right ventricle of the
heart. Contraction of the right ventricular wall applies pressure to the blood. This forces
the tricuspid valve closed and the closed valve prevents blood from going back into the
right atrium. The pressure forces blood past the semilunar valve into the pulmonary
trunk. Upon relaxation of the right ventricle, back pressure of the blood in the pulmo-
nary trunk closes the pulmonary semilunar valve. The blood then passes into the lungs
through the pulmonary arterial system. Gases are exchanged between the alveoli of
the lungs and the blood in the capillaries next to the alveoli. This blood, now saturated
with oxygen, is collected by the pulmonary veins and carried to the left atrium of the
heart. This completes the pulmonary cycle.
c. Systemic Cycle.
(1) Left ventricle of the heart. The oxygen-saturated blood is moved from the
left atrium into the left ventricle. When the left ventricular wall contracts, the pressure
closes the mitral valve, which prevents blood from returning to the left atrium. The con-
traction of the left ventricular wall therefore forces the blood through the aortic semilunar
valve into the aortic arch. Upon relaxation of the left ventricular wall, the back pressure
of the aortic arch forces the aortic semilunar valve closed.
(2) Arterial distributions. The blood then passes through the various arteries
to the tissues of the body. See figure 9-5 for an illustration of the main arteries of the
human body.

Medical News
Sport can help multiple sclerosis patients
A study developed at the Miguel Hernández University of Elche...
Cause of donor death should not automatically exclude lungs from transplant consideration
Patients receiving lungs from donors whose cause of death was...
Exposure to dim light at night may make breast cancers resistant to chemotherapy
For rats bearing human breast tumors, exposure to dim light...
Researchers study novel drug-delivery system
University of Mississippi School of Pharmacy researchers are studying an...
New study detects early metabolic signals that our bodies are not coping with diet or lifestyle
New research from the University of Aberdeen's Rowett Institute of...
Apples are simple, healthful, yet full of variety
With autumn's arrival and National Apple Month right around the...
Working group tackles public health and health inequality
Public health and health inequality are embedded in complex systems,...
Eighty percent of bowel cancers halted with existing medicines
(Medical Xpress)—An international team of scientists has shown that more...
Gene interacts with stress and leads to heart disease in some people
A new genetic finding from Duke Medicine suggests that some...
Treatment of substance abuse can lessen risk of future violence in mentally ill, study finds
If a person is dually diagnosed with a severe mental...
Omega-3 fatty acids may prevent some forms of depression
Patients with increased inflammation, including those receiving cytokines for medical...
Study establishes zebrafish as a model for flu study
In the ongoing struggle to prevent and manage seasonal flu...
Learn how to recognize, intervene in domestic violence cases
As recently as 40 years ago, domestic violence often was...
Scientists wield plant viruses against deadly human disease
Case Western Reserve University researchers hope to take a healthy...
Ethical behavior can be contagious, study says
A new study from Penn State Smeal College of Business...
Researchers explore new possibilities for the treatment of epilepsy
Ongoing research at Iowa State University is investigating the connection...
Technology could reduce the amount of time to determine whether a cancer drug is working
An official at a life sciences startup based on a...
Pill coated with tiny needles can deliver drugs directly into the lining of the digestive tract
Given a choice, most patients would prefer to take a...
Predicting the future course of psychotic illness
University of Adelaide psychiatry researchers have developed a model that...
Exercise to prevent falls and fractures
Boosting your activity levels and doing strength and balance exercises...

Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +