Understanding the Cardiovascular, Blood, and Lymphatic Systems
The Cardiovascular System
The heart is the pump that moves blood through the cardiovascular system. It consists of two halves separated by a muscular wall.
Structure of the Heart
Each half of the heart is divided into an upper and lower cavity. The heart is enclosed in the pericardium, a double sac that provides a fluid-filled space for it to beat freely.
- Myocardium: Muscle tissue that forms the heart.
- Atria: The upper chambers of the heart.
- Ventricles: The heart’s lower chambers.
- Atrioventricular Valves: Mitral (left) and tricuspid (right).
- Semilunar Valves: Pulmonary (blood without oxygen) and aortic (oxygenated blood).
Operation of the Heart
- Diastole: Relaxation phase where blood passes from the atria to the ventricles.
- Systole: Contraction phase where blood passes from the ventricles to the pulmonary artery and aorta.
Blood Circuit
Blood flows through blood vessels driven by the heart’s movements. Each beat consists of a systole and a diastole. In this cycle, blood enters the atria, passes into the ventricles, and exits into the arteries.
Cycle Rate
- Ventricular Systole: Begins with the contraction of the ventricles, carrying blood away from the heart through the aorta and pulmonary arteries.
- Ventricular Diastole: The ventricles relax and fill with blood due to pressure.
- Atrial Systole: The atria contract, and the atrioventricular valves open, driving blood into the ventricles.
- Diastole: The atria relax and fill with blood from the vena cava and pulmonary veins.
Blood Circulation
The general circuit begins in the left ventricle, where oxygenated blood goes to the aorta artery, which branches throughout the body, reaching the cells of organs. Deoxygenated blood is collected in venules.
The pulmonary circuit begins in the right ventricle, where oxygen-poor blood is pumped into the pulmonary artery, which branches into two branches that go to the lungs. Here, blood is oxygenated and returns through the pulmonary veins to reach the left atrium.
Blood Vessels
Blood vessels are a network of tubes that carry blood from the heart to the body.
Arteries
Arteries carry blood from the heart to the organs and lungs. They leave the ventricles and consist of muscle tissue to withstand the high pressure that moves blood.
Veins
Veins carry blood from the organs to the heart. They have valves that open and close to prevent backward flow of blood.
Blood Components and Functions
Blood consists of a liquid called plasma (a yellow liquid).
Components of Blood
- Red Blood Cells: Small cells without nuclei that carry oxygen.
- White Blood Cells (Lymphocytes, Granulocytes): Various types of cells involved in immune defense.
- Platelets: Pieces or fragments of the cell membrane that assist in blood clotting.
Functions of Blood
- Transport and Exchange of Nutrients: Intake of nutrients and oxygen and removal of CO2 to the cells.
- Temperature Control: Blood transports heat between the body’s core and its surface.
- Defense of the Body: Protects the body from bacteria entering the body.
Internal Environment
The internal environment consists of blood, lymph (waste going into the blood and collected by the lymphatic vessels), and interstitial fluid (surrounding the cells and taking waste to the lymphatic system).
Lymphatic System
The lymphatic system consists of lymphatic vessels (tubes with valves that prevent the retreat of lymph) and lymph nodes (where lymph is collected and cleaned; lymphocytes are manufactured to defend the body).
Functions of the Lymphatic System
- Maintains fluid balance in the internal environment.
- Transports lipids to avoid direct entry into the blood.
- Defends the body via lymphocytes.
Excretory System
Excretion is the elimination of waste substances from the cells. Kidney function governs the chemical composition of the blood and regulates water loss through urine.
Nephron
The nephron is the functional unit of the kidney.
Structure of the Nephron
- Glomerulus: Formed by capillaries with a filtering function.
- Renal Tubule: Formed by the loop of Henle.
- Collecting Duct: Its function is to expel noxious substances.
- Renal Pelvis: A cavity reaching the collecting ducts, narrowing to form the ureter.