Body Fluids and Circulation

• The heart has four chambers: two atria and two ventricles.
• Living cells need to be provided with nutrients, O2, and other essential substances
• Waste or harmful substances produced by cells must be continuously removed for healthy tissue functioning
• Efficient mechanisms are essential for the movement of substances to and from cells
• Different groups of animals have evolved different methods for substance transport
• Sponges and coelenterates circulate water through their body cavities to facilitate substance exchange
• Most higher organisms, including humans, use blood as the main body fluid for substance transport
• Lymph also helps in the transport of certain substances
• Blood is a special connective tissue consisting of plasma and formed elements
• Plasma constitutes nearly 55% of blood and contains water and proteins
• Major proteins in plasma are fibrinogen, globulins, and albumins
• Formed elements in blood include erythrocytes, leucocytes, and platelets
• Erythrocytes are red blood cells, most abundant in blood, lack a nucleus, and contain haemoglobin
• Leucocytes are white blood cells, nucleated, and involved in defense mechanisms
• Platelets, or thrombocytes, are cell fragments involved in blood clotting
• Blood groups are classified into ABO and Rh groups
• ABO grouping is based on the presence of antigens A and B on RBCs and antibodies in plasma
• Rh grouping is based on the presence of the Rh antigen on RBCs
• Coagulation of blood is a mechanism to prevent excessive blood loss from the body
• Lymph is a fluid that collects interstitial fluid from tissues and drains it back to major veins
• Lymph contains lymphocytes responsible for immune responses and is a carrier for nutrients and hormones
• Circulatory patterns can be open or closed, with vertebrates having a closed circulatory system
• All vertebrates possess a muscular chambered heart
• Human circulatory system consists of a muscular chambered heart, closed branching blood vessels, and blood
• Heart has four chambers: two atria and two ventricles, separated by septa and valves
• Cardiac muscles make up the entire heart, with thicker walls in the ventricles
• Specialised nodal tissue in the heart includes the sino-atrial node (SAN) and atrio-ventricular node (AVN)
• Atrio-ventricular bundle (AV bundle) passes through the atrio-ventricular septa to emerge on the top of the inter-ventricular septum
• The heart is myogenic, meaning its normal activities are regulated intrinsically by specialized muscles (nodal tissue)
• The heart consists of two atria and two ventricles
• The heart has a complete double circulation system, with two circulatory pathways: pulmonary and systemic
• Pulmonary circulation starts with the pumping of deoxygenated blood by the right ventricle to the lungs, where it is oxygenated and returned to the left atrium
• Systemic circulation starts with the pumping of oxygenated blood by the left ventricle to the aorta, which is carried to all body tissues, and the deoxygenated blood is collected by the veins and returned to the right atrium
• The heart is composed of a network of vessels and a fluid called blood
• The heart has the ability to alter the stroke volume and heart rate, thereby affecting the cardiac output
• The cardiac output is the volume of blood pumped out by each ventricle per minute and averages 5000 mL or 5 litres in a healthy individual
• The heart has a sequential event called the cardiac cycle, consisting of systole and diastole of both the atria and ventricles
• The heart beats 72 times per minute, with each ventricle pumping out approximately 70 mL of blood during a cardiac cycle
• The electrical activity of the heart can be recorded using an electrocardiograph (ECG), which is a graphical representation of the electrical activity of the heart during a cardiac cycle
• The heart has two prominent sounds produced during each cardiac cycle: the first heart sound (lub) associated with the closure of the tricuspid and bicuspid valves, and the second heart sound (dub) associated with the closure of the semilunar valves