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Unit 6 Circulation, Respiration, and Regulation

In this unit learners will explore how the cardiovascular, pulmonary, and renal systems regulate the body’s homeostatic functions and apply this knowledge to the diagnosis, treatment and management of both acute and chronic diseases caused by abnormal functions of these systems.  This integration of basic sciences with osteopathic clinical skills will be developed through learner participation in case-based learning, simulation activities, and community engagement projects that emphasize pertinent biomedical, bioethical, and public health principles.  Each learner’s professional identity formation as an osteopathic physician will continue in this unit through an emphasis on how health care teams work in the diagnosis, treatment, and management of diseases that impact regulatory functions. The learners will also be challenged to understand how the practice of self-care, awareness, and lifestyle modifications can regulate wellness in the individual and community.


In ancient times, the circulatory system was thought to provide energy for the vital spirit with its center, the heart, as the soul.1 With the advancement of science, it is now known that the circulatory system provides oxygen and nutrients to meet the metabolic demands of the body. Moreover, the regulation and maintenance of the circulatory system through complex integration of the heart, lungs, and kidneys is essential for good health. Habits such as illicit drug, alcohol, and tobacco use, poor diet, and a sedentary lifestyle impair the functions of the circulatory, respiratory, and renal systems leading to the manifestations of disease.  Epidemiological evidence for determining risk factors and education on the promotion of healthy lifestyle modifications are key components in the prevention of both acute and chronic diseases.

In understanding the role of the circulatory system, Dr. A.T. Still stated “the rule of artery and vein is universal in all living beings, and the osteopath [osteopathic physician] just know and abide by its ruling, or he [she] will not succeed as a healer.”2 The heart serves as a pump for the circulatory system working in concert with the lungs for gas exchange and the kidneys for filtration to supply blood to every tissue and organ.  Together these organs maintain homeostasis through regulation of blood pressure and acid-base balance.

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States, accounting for one in seven deaths.3 Despite the decline over the last few decades in age-standardized cardiovascular related deaths, there is a still an overwhelming increase in risk factors for various CVD.3 Moreover, in context to global health, CVD is seen as a major component of leading noncommunicable diseases, such as chronic respiratory disease, diabetes mellitus, and cancer.4 Diseases of the heart, lungs, and renal systems comprise the majority of comorbidities accounting for over 65% of deaths in the United States.5

Comorbidities increase the burden of disease, with many sharing common modifiable risk factors such as smoking, obesity, sedentary lifestyles, and unhealthy diets. Type 2 diabetes is a prime example of a chronic disease that increases the risk of fatal complications such as CVD, kidney failure, and infection. In the United States, 68% of people with diabetes also have hypertension.3 Similarly, patients with chronic obstructive pulmonary disease are two times more likely to have CVD-related hospitalization and mortality including arrhythmias, ischemic heart disease, and congestive heart failure.6 Furthermore, the combination of these disease pathologies leads to a vicious cycle in which one exacerbates the other causing dramatic increases in morbidity and mortality resulting in increased economic burden of health care costs.3-6

1Schultz, S. G. (2002). William Harvey and the circulation of the blood: The birth of a scientific revolution and modern physiology. News in Physiological Sciences: An International Journal of Physiology Produced Jointly by the International Union of Physiological Sciences and the American Physiological Society, 17, 175-180.
2Still A.T. 1899 Philosophy of Osteopathy. Academy of Osteopathy, Kirksville, MO
3Benjamin, E. J., Blaha, M. J., Chiuve, S. E., Cushman, M., Das, S. R., Deo, R., et al. (2017). Heart disease and stroke statistics-2017 update: A report from the american heart association. Circulation, 135(10), e146-e603.
4Bloom, D.E., Cafiero, E.T., Jané-Llopis, E., Abrahams-Gessel, S., Bloom, L.R., Fathima, S., et al. (2011). The Global Economic Burden of Noncommunicable Diseases. Geneva: World Economic Forum
5Morbidity and Mortality Weekly Report (MMWR) Indicators for Chronic Disease Surveillance — United States, 2013 Recommendations and Reports; January 9, 2015 / 64(RR01)
6Dalal, A. A., Shah, M., Lunacsek, O., & Hanania, N. A. (2011). Clinical and economic burden of patients diagnosed with COPD with comorbid cardiovascular disease. Respiratory Medicine, 105(10), 1516-1522.