Circulatory & Respiratory Systems

The blood flow & respiration

Circulatory System - the body system that delivers oxygen and nutrients throughout the body

The Relationship Between Arteries, Veins, and Capillaries

Arteries, veins, and capillaries all carry blood throughout the body, but what makes them separate from each other is where the blood is taken. Arteries deliver blood away from the heart through the body, while veins take this blood delivered to body parts, and takes them back to the heart. Capillaries work on a smaller level than this, and take blood from cell to cell, rather than organs.

Diagram of the Heart

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The Route's that Blood Takes Through the Heart

Blood enters through the right atrium through the superior and inferior vena cavas, and then through the tricuspid valve, and then through to the right ventricle. After this, it goes through the pulmonary valve to the pulmonary arteries, then to the lungs. In the lungs, the blood is oxygenated and then returned to the heart through the pulmonary veins, and then into the bicuspid valve to go to the left ventricle. From the left ventricle, it goes to the aortic valves into the aorta, and the aorta pumps the blood out and the cycle begins again.

The Composition of Blood

Blood in a simplified way is just cells, cell pieces, and plasma. Blood is mainly composed of plasma and red blood cells (erythrocytes), and is also made up of platelets and white blood cells (leukocytes). Plasma is extremely important in blood, because it carries all the nutrients and hormones and other things that need to be delivered through the body. Erythrocytes and leukocytes are not similar in their functions, in which the erythrocytes carry oxygen and other gases throughout the body, and leukocytes fight against pathogens and anything foreign. Platelets are pretty much what makes up a scab, in which when there is an open wound, platelets rush to the wound to clot the blood and scab it.

Disorders of the Circulatory System

Arrhythmia - Arrhythmia is a heart issue, in which you have an irregular heartbeat. Signs of this could be chest pains, dizziness, and other things related to dizziness such as fainting, or getting light-headed easily. This can be treated through medication, but no over-the-counter drug could take care of it.

Atherosclerosis - Atherosclerosis is also a heart issue, where there is plaque build up within the arteries, slowing down blood flow to whatever artery the blood is traveling to. Symptoms of this are fatigue, muscle weakness, and pain where the artery is blocked. This could be treated by simply living a healthier lifestyle, and maintaining a healthy weight.

Circulatory System - the body system in which gas exchange takes place, allowing for oxygen and carbon dioxide exchange, and maintains homeostasis.

The Features of Alveoli

Alveoli are the tiny air sacs of the lungs, one alveoli is called an alveolus and it is the size of a grain of sand, the surface is moist with surfactant increasing surface area for gas exchange to take place, there are approximately 300 million to 600 million making up a massive surface area for gas exchange, it has been reported that if you laid out all of the alveoli the surface area would be equivalent to a tennis court, the tissue is spongy and elastic which allows for expansion and contraction, alveoli are housed in capillaries in a large complex network, the capillaries also penetrate the alveoli, the capillaries have a lower oxygen concentration that the alveoli and thus oxygen diffuses from the alveoli to the capillary and carbon dioxide diffuses from the pulmonary capillary to the alveoli for it to be exhaled as a waste product.

How is Carbon Dioxide and Oxygen Transported Through the Blood?

Red blood cells carry oxygen in the blood, specifically oxygen binds to hemoglobin which is a iron rich protein and is transported to cells in the body; carbon dioxide is formed by the cells as a waste product and it is released into the blood as carbonic acid. (carbon dioxide bound to water)

Diagram of the Human Ventilation System

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Disorders of the Respiratory System

Asthma is an airway obstruction and hyperreactivity of the airways as well as inflammation and hypersecretion of mucus, obstruction is reversible with medications. SIgns and symptoms include coughing, wheezing, chest tightness, and shortness of breath. Treatment of asthma includes bronchodilators which is medication that relaxes the smooth muscles surrounding the airways and thus reduces bronchoconstriction or bronchospasm which contributes to airway obstruction. Inhaled steroids are also part of the treatment for asthma in order to reduce inflammation of the airway tissue and decrease mucus production.


Pulmonary fibrosis is a condition affecting the lungs in which the lung tissues becomes hardened, fibrotic, and restricted, decreasing surface area for gas exchange. SIgns and symptoms include cough, shortness of breath, chest discomfort, and inspiratory crackles when listening with a stethoscope on exam. In particular, idiopathic pulmonary fibrosis, is a form of pulmonary fibrosis that the exact incidence and prevalence in the US has been estimated to be around 14 and 42 cases per 100,000 patients. This condition and prevalence is similar in the UK as well. There are many causes for pulmonary fibrosis, such as autoimmune diseases like rheumatoid arthritis, sometimes patients have pulmonary fibrosis for unknown reasons called idiopathic pulmonary fibrosis, the main treatment for pulmonary fibrosis has been supplemental oxygen therapy, steroids, and now the FDA has recently approved 2 new medications for the treatment of idiopathic pulmonary fibrosis to control fibroblasts formation affecting the lungs. The medications are extremely expensive and patients typically die of respiratory failure within 6 months from time of diagnosis to two years with regards to idiopathic pulmonary fibrosis; otherwise, patients with other causes of fibrosis may live up to five or more years with proper immunosuppressive therapy.