Cardiovascular system is composed of Heart – the organ that pumps blood through the system, Blood – connective tissue that has plasma and a variety of cells and substances and Blood Vessels – a network of passageways to transport the blood to and from the body’s cells
Blood vessels are intricate networks of tubes that transport blood throughout the entire body. There are different Walls often called coats or tunics. The Tunica interna is the innermost layer, composed of squamous epithelial cells, provide smooth surface so blood can easily pass through. The Tunica media, the middle layer, thicker and are composed of smooth muscles and elastic tissues and collagen. And the Tunica externa which is outermost layer provides vessel support and protection, composed of fibrous tissue.
There are different blood vessels namely Arteries, Aorta, Arteriole, Capillaries, Venules, and Veins. Arteries are an elastic blood vessel that transports blood away from the heart. Aorta is the largest artery in the body, originating from the left ventricle of the heart and extends down to the abdomen, where it branches off into two smaller arteries. Arteriole is a small diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries. Capillaries are where the change of nutrients, gasses and waste products occurs at the cellular level. Venules are ever merging vessels and the tiniest which forms the larger veins. Veins are an elastic blood vessel that transports blood from various regions of the body to the heart. Veins also have thinner walls than arteries, are more numerous, and have a larger capacity to hold blood.
The Heart is a specially shaped muscle that contains series of chambers that move through out the body. The base of the heart is proximal to your head, while the apex is distal. It is a Single organ that acts as a two separate pumps working together. The right side is responsible for collecting the blood and sending it to lungs to pick up oxygen and get rid of carbon dioxide. The left side collects blood from the lungs and pumps it throughout the body.
Pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava, and the pulmonary artery. It is divided into three layers: Endocardium is the inner layer of the heart. It consists of epithelial tissue and connective tissue. Myocardium is the muscular middle layer of the wall of the heart. It is composed of spontaneously contracting cardiac muscle fibers which allow the heart to contract. And Visceral Pericardium is the outer layer of the wall of the heart. It is composed of connective tissue covered by epithelium. The epicardium is also known as the visceral pericardium. Pericardial Cavity lies between the visceral pericardium and the parietal pericardium which is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes.
There are different Chambers of the Heart. Atria contains the upper two chambers of the heart are called the left atrium and the right atrium. Ventricle contains the lower two chambers of the heart. The wall that separates the two smaller chambers (atria) is called interatrial septum. The wall that separates the two larger chambers (ventricle) is called interventricular septum.
Vena cava is the two largest veins in the body. They carry de-oxygenated blood from various regions of the body to the right atrium. Superior Vena Cava brings de-oxygenated blood from the head, neck, arm and chest regions of the body to the right atrium. Inferior Vena Cava: brings de-oxygenated blood from the lower body regions to the right atrium.
Heart Valves are flap-like structures that allow blood to flow in one direction. There are different valves, the bicuspid valve, tricuspid valve, aortic valve, and pulmonary valve.
Cardiac cycle is the sequence of events that occur when the heart beats. The cardiac cycle is divided into two: Diastole and Systole. Diastole is part of the cycle which Ventricles are relaxed, Atrioventricular valves are open, The sinoatrial (SA) node, which starts cardiac conduction, contracts causing atrial contraction, the atria empty blood into the ventricles, and Semi lunar valves close preventing back flow into the atria. On the other hand, Systole is part of the cycle which Ventricles contract, atrioventricular valves close and semi lunar valves open. And Blood flows to either the pulmonary artery or aorta.
Autorhytmicity is the unique ability of the cardiac muscles that they don’t rely on nerve impulses and hormones to contract because they can contract on their own. Step 1: Pacemaker Impulse Generation - SA node contracts generating nerve impulses. Step 2: AV Node Impulse Conduction - Impulses are delayed for about tenth of a second this allows the atria to contract and empty their contents first. Step 3: AV bundle Impulse Conduction - The bundles branches off into two and the impulses are carried down the center of the heart to the left and right ventricle. Step 4: Purkinje Fibres Impulse conduction- AV bundles divides into Purkinje fibres in the ventricles to contract
The function of the Blood is to transports dissolved gases, Waste products of metabolism, Hormones; Enzymes; Nutrients , Plasma proteins, Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes'), maintain Body Temperature, control, remove toxins from the body, regulate Body Fluid Electrolytes, help to protect us from the invasion and infection by pathogens and toxins.
Erythrocytes (Red blood Cells) RBCs are created by the red bone marrow through a process called hemopoiesis. It performs two crucial functions: transports oxygen from the lungs to the cells in the body with the aid of an iron-containing red pigment called haemoglobin and help to transport carbon dioxide, a by-product of cellular metabolism, from the cells to the lungs for removal from the body.
Leukocytes (White blood Cells) WBCs are guardians from invasion and infection. The types of WBC’s are Polymorphonuclear granulocyte and Agranulocyte. Polymorphonuclear granulocyte composes Neutrophils, Basophils and Eosinophils. Agranulocyte composes of Monocytes and Lymphocytes.
Thrombocytes (Blood Platelets) are the smallest formed elements. It is responsible for the bloods ability to clot and it releases serotonin which can cause smooth muscle constriction and decreased blood flow.
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