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.
MD0006
9-12



Medical News
Nurse-Patient Ratio Law in MA Raises Cost, Quality Concerns
(MedPage Today) -- Mandated staffing ratios are good for nurses,...
medpagetoday.com
Resveratrol Induces Fat Browning, Weight Loss in Mice (CME/CE)
(MedPage Today) -- The polyphenol resveratrol appears to induce the...
medpagetoday.com
People Prefer Curves Over Angles? That's Improbable!
(MedPage Today) -- Also, men and women have the same...
medpagetoday.com
Immigrant children given adult dose of hepatitis A vaccine
About 250 immigrant children were given an adult dose of...
medicalxpress.com
Second-line cetuximab active beyond progression in quadruple wild-type patients with mCRC
Patients with metastatic colorectal cancer (mCRC) that are mutation-free in...
medicalxpress.com
MERS cases keep coming from Samsung hospital
Another doctor at a major hospital that has been the...
medicalxpress.com
Doc Shortages, Better Bedside Manner: Healthcare Career Insights
(MedPage Today) -- Must reads about the latest news and...
medpagetoday.com
Study Predicts Huge Toll of Hep C Drugs on Calif. Budget
(MedPage Today) -- Cost estimates range from $512 million to...
medpagetoday.com
Genes Not Responsible for Migraine-Heart Disease Link (CME/CE)
(MedPage Today) -- Migraine without aura actually shares cardioprotective gene...
medpagetoday.com
REM sleep critical for young brain development; medication interferes
Rapid eye movement or REM sleep actively converts waking experiences...
medicalxpress.com
Body Size Not a Factor in Ovarian Ca Dosing (CME/CE)
(MedPage Today) -- Relative dose intensity had stronger link to...
medpagetoday.com
Tweet of the Week: Twitter Banter Escalates Into Pun Battle
(MedPage Today) -- A scientific porcupine named Bill? Nye-quill. Well,...
medpagetoday.com
Liberia works to contain Ebola, find source of new cases
Liberia is working hard to contain Ebola and find the...
medicalxpress.com
Happy Fourth of July from Stanford Medicine
Happy Fourth of July! Our office is closed in honor...
scopeblog.stanford.edu
CMS Floats Outpatient Payment Update, FDA Eyes Codeine Cough Syrups
(MedPage Today) -- Also: House members question CMS fraud prevention...
medpagetoday.com
Noise from fireworks threatens young ears
(HealthDay)—The Fourth of July weekend is a time for celebrations...
medicalxpress.com
Many new teen drivers 'crash' in simulated driving task
(HealthDay)—Around four in 10 newly licensed teen drivers "crashed" in...
medicalxpress.com
Telehealth and High Deductibles Slow Health Spending
(MedPage Today) -- Health spending in employer-based market is trending...
medpagetoday.com
Brain folding related to surface area and thickness, not number of neurons
(Medical Xpress)—A pair of researchers with Universidade Federal do Rio...
medicalxpress.com
New test could predict arthritis drug failure in patients
A study of 311 patients by The University of Manchester...
medicalxpress.com
 


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 +