System krwionośny i limfatyczny

Circulatory System

The human circulatory system is responsible for transporting various substances throughout the body, including oxygen, nutrients, waste products, hormones, and cellular components. It consists of two main parts: the cardiovascular system, which includes the heart and blood vessels; and the lymphatic system, which helps remove excess fluid from tissues. Let's explore these systems in detail.

Heart Anatomy

The heart is a muscular pump located between the lungs, nestled in the ribcage. It has four chambers: left and right atria, and left and right ventricles. Deoxygenated blood returns to the right side of the heart via large veins called vena cavae. The right atrium receives blood from the superior vena cava, which drains blood from the head and arms, and the inferior vena cava, which carries blood from the lower body. From the right atrium, deoxygenated blood passes into the right ventricle through a valve named the tricuspid valve. Oxygenated blood from the lungs enters the left atrium via pulmonary veins. After passing through the bicuspid (mitral) valve, it enters the left ventricle, the chamber that pumps blood out into the circulation.

Blood Composition

Blood is primarily composed of plasma and formed elements. Plasma is a liquid portion of blood containing water, electrolytes, and dissolved gases such as oxygen, carbon dioxide, and nitrogen. Formed elements include red blood cells (erythrocytes), white blood cells (leukocytes), platelets, and clotting factors. Red blood cells contain hemoglobin, which binds with oxygen molecules. White blood cells play a critical role in immune function. Platelets help form blood clots, while clotting factors prevent excessive bleeding.

Blood Vessels

Blood vessels are tubes that transport blood throughout the body. They can be categorized by their size and thickness. Arteries carry oxygenated blood away from the heart, veins transport deoxygenated blood toward the heart, and capillaries facilitate exchange between blood and surrounding tissue. Arteries have thick walls comprising smooth muscle, elastic tissue, and collagen fibers to regulate blood flow, minimize damage due to pressure changes, and prevent rupture. Veins have thinner walls compared to arteries and lack the smooth muscle layer to accommodate blood volume fluctuations. Capillaries, the smallest vessels, allow exchange between blood and interstitial fluid via a process called diffusion.

Circulation Pathways

The circulatory system follows two main pathways: pulmonary circulation, which carries blood to and from the lungs; and systemic circulation, which transports blood to other parts of the body. Pulmonary circulation begins with deoxygenated blood returning to the right side of the heart and then pumped by the right ventricle to the lungs via the pulmonary artery. Here, oxygen is absorbed, and carbon dioxide is released. Oxygenated blood then returns to the left atrium via pulmonary veins, completing pulmonary circulation. Systemic circulation starts with oxygenated blood leaving the left ventricle through the aorta and branching into arteries that supply blood to various organs and tissues. Venous blood returns to the heart through vena cavae.

Lymphatic System

The lymphatic system is an essential part of the circulatory system, as it helps maintain fluid balance and immune function. It consists of a network of lymphatic vessels, lymph nodes, the spleen, and the thymus gland. Lymphatic vessels collect excess fluid from tissues, forming lymph, which contains waste products, proteins, and immune cells. Lymph nodes filter lymph, removing waste and enhancing immune function. The lymphatic system also plays a role in immune defense, as it contains immune cells called lymphocytes that help fight infections. The spleen, a large organ located in the upper left abdomen, helps filter blood and remove old red blood cells.