Understanding the Human Body: Internal Environment and Blood Circulation

Internal Environment

The internal environment is the set of surrounding cells and liquids of an organism. Cells extract the nutrients and oxygen they need from it, and discharge waste and carbon dioxide produced during metabolism. The interstitial fluid originates from blood that has been filtered through the thin walls of blood capillaries.

Homeostasis

Homeostasis is a set of mechanisms whose mission is to maintain a constant internal environment, meaning that its properties do not vary. The maintenance of these properties is called homeostasis, and the task is performed by different devices and systems of the organism.

Veins and Arteries

Arteries and veins differ in that arteries carry blood from the heart to the various organs of the body, and veins carry blood from the various organs toward the heart. Also, an artery bleeds much more easily and takes much longer to stop bleeding than a vein.

Blood Capillaries

Blood capillaries have a very thin wall because there occurs an exchange of nutrients, oxygen, etc.

Functions of Blood

Blood plays the following roles:

• Transports nutrients from the digestive system to every cell in the body.
• Carries oxygen from the lungs to the cells, and carbon dioxide produced by these in reverse order.
• Collects the waste produced by the cells to deliver it to the excretory system, so that it may be disposed of outside.
• Carries the body's defense cells.
• Participates in the regulation of body temperature by heating or cooling.

Hemoglobin

Hemoglobin is a protein found inside red blood cells. Its function is to transport oxygen from the lungs to various body cells and remove the carbon dioxide produced by these cells.

Different Blood Cells

• Red blood cells or erythrocytes: Carry oxygen from the lungs to various body cells and remove carbon dioxide produced.
• White blood cells or leukocytes: Participate in defensive functions against infections.
• Platelets or thrombocytes: Participate in the processes of blood coagulation.

Erythrocytes, Leukocytes, and Thrombocytes

• Erythrocytes: Blood cells lacking nuclei, with a flattened shape, flattened at their center, containing hemoglobin.
• Leukocytes: Nucleated blood cells, irregularly shaped.
• Thrombocytes: Cellular fragments that assist in blood coagulation.

Mitral and Tricuspid Valves

The difference between the mitral and tricuspid valves is that the mitral valve connects the left atrium and ventricle and consists of two lamellae, and the tricuspid valve connects the right atrium and ventricle and consists of three lamellae.

Semilunar Valves

The function of the semilunar valves is to prevent the return of blood that enters the ventricles. They are located at the beginning of the arteries.

Coronary Arteries

The function of the coronary arteries is to provide blood supply, oxygen, and nutrients to the heart.

Double Circulation

Our circulation is double because, in the course of a complete blood circuit, blood passes twice through the heart, thus establishing two circuits. It is considered complete because there is no mixing of oxygen-rich blood with carbon dioxide-rich blood.

• Arteries: Rich in oxygen.
• Veins: Rich in carbon dioxide.
• General Circulation: Rich in oxygen.