Blood Components and Functions

• The circulatory system consists of parts of the body that help in transportation of materials.
• In animals this system includes a fluid transport medium, a control center (heart), and path through which the transport medium circulates.

Fluids in the Body

• An adult human body contains 40 liters of fluids.
• Intracellular fluids make up 25 liters and are found within the cells.
• Extracellular fluid makes up the remaining 15 liters and is present in the spaces in the body.
• Blood is a red fluid that circulates through the heart and blood vessels.
• Tissue fluid is a colorless fluid found between cells in various organs.
• As blood flows through capillaries, blood plasma and WBCs move out into the surrounding space, thereby bathing the cells.
• Cells absorb oxygen and nutrients from the tissue fluid, and give back carbon dioxide and wastes.
• Lymph is a faint yellow fluid contained in lymph vessels, and consists of WBCs.
• Lymph vessels pour the lymph back into blood circulation through the subclavian vein.
• Open and closed circulatory systems exist.
• In an open circulatory system, exchange occurs directly between cells and blood, with blood circulating in interstitial spaces.
• These circulatory systems have few blood vessels, which are open-ended as they open into common cavities referred to as the haemocoel.
• Insects are an example of organisms with an open circulatory system.
• In a closed circulatory system, blood circulates within closed vessels and is distinct from the interstitial fluid.
• It is comprised of the heart that pumps blood into the vessels to reach the tissues and organs.
• Exchange of gases occurs in the bloodstream between capillaries and tissues.

Components of Transport (Circulatory) System

• Key components of the circulatory system in humans include blood, heart, blood vessels, and lymph.
• Blood is a fluid connective tissue composed of 55% plasma and 45% formed elements, making up 8% of body weight and circulating to deliver oxygen and nutrients.
• An average adult has 5-6 liters of blood.
• Plasma carries most materials in dissolved form, is mainly water, and carries minerals, amino acids, glucose, urea, hormones, and dissolved proteins.
• Formed elements, including RBCs, WBCs, and platelets, are also present in the blood plasma.
• Plasma is pale yellow, makes up 50% of blood, and contains salts, nutrients, water, and enzymes.
• Blood plasma transfusions are given to patients with liver failure.
• RBCs (erythrocytes) contain hemoglobin, which carries oxygen for respiration.
• Mature human RBCs are small, biconcave, and lack mitochondria or a nucleus.
• The shape of RBC's improves gas exchange.
• Lack of a nucleus in RBCs makes space for hemoglobin in oxygen transport.
• Oxygen binds to hemoglobin in the blood to reach cells of the body.
• Oxygen and hemoglobin combine to produce oxyhemoglobin.
• Carbon dioxide and hemoglobin combine to produce carbaminohemoglobin.
• Carbon monoxide and hemoglobin combine to produce carboxyhemoglobin.
• The lack of mitochondria maximizes the oxygen delivered to tissues.
• Red blood cells have an average life span of 120 days, and are broken down in the liver and spleen, with new cells produced in bone marrow.
• Erythropoietin, a hormone released by the kidneys, controls the production of red blood cells in response to low oxygen levels.
• Hemoglobin is an iron-containing pigment in red blood cells for carrying respiratory gases.
• Deficiency of iron or some vitamin(B12 or Cyanocobalamin) in the food causes deficiency of haemoglobin in causing anaemia.
• Low red blood cell count, pale skin, loss of stamina, dizziness, low oxygen, low metabolic rate, and rapid heartbeat may indicate anaemia.
• Eating iron and vitamin B12 rich foods can cure haemoglobin deficiency.
• WBCs (leukocytes) are less common than red blood cells and make up less than 1% of blood cells.
• Primarily involved in immune responses, recognising and neutralising invaders like bacteria and viruses.
• White blood cells have a normal nucleus and mitochondria.
• Granulocytes include neutrophils, eosinophils, and basophils, all of which have granules in the cytoplasm when stained.
• Agranulocytes are monocytes and lymphocytes and do not have granules in the cytoplasm.
• Some WBCs engulf pathogens, while others launch immune responses and have varying lifespans, and are produced primarily in the bone marrow.
• Blood Platelets (Thrombocytes) help in clotting of the blood during injury to prevent blood loss.
• Platelets are cell fragments involved in blood clotting
• Megakaryocytes break into pieces to produce platelets fragments.

Functions of Blood

• Blood transports materials, maintains water balance, plays a role in immune responses, aids in absorption, and excretes waste.
• Blood aids in the transport of materials in the body, with blood plasma as the main transport medium.
• Blood helps control water levels, carrying extra water to be filtered by the kidneys, while retaining water when there is scarcity.
• WBCs protect the body by killing microorganisms
• The blood plasma also carries antibodies to kill invading microorganisms.
• Blood supplies intestines where it absorbs nutrients from digested food and supplies to organs.
• Blood carries wastes like CO2 to the lungs and urea to the kidneys.
• Blood distributes heat, helping maintain normal body temperature.
• Platelets clot blood at injury sites forming a clump and fibrins to complete the clot.

Blood Vessels

• Arteries, veins, and blood capillaries.
• Arteries carry blood away from the heart and have thick walls to withstand high blood pressure.
• Veins carry blood towards the heart, bearing low pressure with thinner walls than arteries and contain valves to prevent backflow.
• Blood Capillaries are the thinnest blood vessels.
• Oxygen, glucose, amino acids, and nutrients pass through the capillary walls into tissue fluid and taken up by surrounding cells. Nitrogenous waste and carbon dioxide are passed from the tissue cells back to the blood via the capillaries.

Arteries vs Veins

• Arteries carry pure, oxygenated, nutrient-rich blood, while veins carry impure, deoxygenated blood.
• Arteries have rigid, thick, highly muscular walls, while veins have thin, collapsible walls.
• Arteries are situated deeply, while veins are superficial and closer to the skin
• Valves are present in veins allowing blood flow in the upward direction.
• Arteries experience high pressure, while veins experience low pressure due to capillary action.
• Pulse is felt on the arteries but not felt on the veins.
• Arterial blood has high oxygen levels and low CO2 content.
• Venous blood has low oxygen levels and high CO2 content.
• Arteries have narrow lumens whereas veins have wide lumens.

Lymph

• The extra tissue fluid in the tissues enters the lymph capillaries.
• Lymph capillaries join up to form lymph vessels.
• Lymph is similar to blood plasma but with less protein; its vessels join veins to supply lymph back into the blood.
• It serves as a source of nutrients for the cells of the tissues.
• Removes fluid with proteins from organs, returning them, playing an important role in killing the microorganisms invading the body.
• Lymph contains specialized WBCs, and helps absorb fats and fat-soluble vitamins in the small intestine.

HEART

• The heart is a hollow muscular organ made of cardiac muscles pumping rhythmically to circulate blood.
• It is located in the chest cavity in between the lungs and is protected by the pericardium, which protects the heart from shocks.
• The human heart is the size of a fist and divided into four chambers: two ventricles and two atria.
• Ventricles are lower chambers that pump blood, and atria are upper chambers that receive blood.
• The right and left regions are separated by the septum.
• The pericardium encloses a fluid-filled cavity, protecting and lubricating the heart.
• Vertebrate hearts range from two chambers in fish to four chambers in avian and mammalian hearts.
• Humans, as mammals, have four chambers (right atrium, left atrium, right ventricle, left ventricle)

Chambers of the Heart

• Atria have thin, less muscular walls, acting as blood-receiving chambers and don't bear much blood pressure.
• Ventricles are muscular chambers responsible for pumping blood and have thicker walls than atria.
• The left ventricle has the thickest walls to force blood into the aorta.
• Valves ensure unidirectional blood flow.
• Atrioventricular valves are located between ventricles and atria.
• The tricuspid valve is between the right ventricle and right atrium, and the mitral valve is between the left ventricle and left atrium.
• Semilunar valves are located between the left ventricle and aorta, as well as between the pulmonary artery and right ventricle.

Types of Circulation

• The human heart separates pure oxygenated and impure blood.
• The main veins (superior and inferior vena cava) collect impure blood from the body and drain it into the Right Atrium.
• Blood passes into the Right Ventricle, then pushed into the Pulmonary Arteries to the lungs for gaseous exchange.
• Pulmonary circulation is the part of circulation responsible for carrying deoxygenated blood away from the heart, to the lungs and then brings oxygenated blood back to the heart.
• Purified blood is supplied from the lungs to the Left Atrium by the Pulmonary Veins.
• Blood passes into the Left Ventricle through the Mitral valve, and is pushed into the Aorta to supply the body.
• Systemic circulation occurs when oxygenated blood is pumped from the heart to the body, and then back again to the heart.
• Coronary circulation supplies oxygenated blood to the heart.
• Double circulation involves blood passing through the heart twice, separating oxygenated and deoxygenated blood to supply oxygen, essential due to the warm-blooded nature and high respiration rate of mammals and birds.
• One circulation is between the heart and body organs, where the left side of the heart receives and pumps oxygenated blood to body organs, which then returns impure blood back to the right side via the veins.
• The other circulation is between the heart and lungs, where the right side pumps impure blood to the lungs to release CO2 and take up oxygen, returning pure oxygenated blood to the left side.
• Animals with single circulations exist too
• Fish have a single circuit and a two-chambered heart with one atrium and one ventricle.
• The atrium collects blood that has returned from the body, while the ventricle pumps the blood to the gills for gas exchange.
• Gill circulation describes blood’s journey to the gills to be re-oxygenated
• Systemic circulation describes blood continuing throughout the rest of the body before arriving back at the atrium; this is called systemic circulation.
• Amphibians have a three chambered heart with two atria and one ventricle.
• There is mixing of the oxygenated and deoxygenated blood in the ventricle.
• Arteries supply fresh oxygenated blood to body organs, dividing into arterioles and then blood capillaries.
• Blood plasma and dissolved materials come out of the thin walls of the capillaries into the tissue.
• Tissue fluid is an intermediate medium between blood and tissue cells and contains oxygen, amino acids, glucose,mineral ions, proteins, etc..
• Body cells take up required materials and release wastes, such as CO2 dissolved into the blood plasma in the capillary.
• Solubility of Carbon dioxide gas in the blood plasma is higher than oxygen.

Cardiac Cycle

• The sequential events in the heart which is cyclically repeated is the cardiac cycle and consists of systole and diastole of both the atria and ventricles.
• Duration of a cardiac cycle is 0.8 seconds.
• Each ventricle pumps about 70 ml of blood (stroke volume).
• Stroke volume multiplied by heart rate gives cardiac output.
• Cardiac output is the volume pumped by each ventricle per minute, averaging 5 liters in a healthy individual.
• Blood is received, tricuspid and bicuspid valves are open, semilunar valves are closed.
• Contraction occurs by the Sino atrial Node stimulating the atria referred to as the atrial systole.
• Conduction to the ventricular side is by the Atrio ventricular node.
• Ventricular muscles contract (ventricular systole), atria relax (diastole), coinciding with the ventricular systole.
• Closure of tricuspid and bicuspid valves increases the ventricular pressure.
• The first heart sound is associated with the closure of the tricuspid and bicuspid valves.
• Semilunar valves open, allowing blood to move into the circulatory pathways.
• The closure of semilunar valves causes ventricular pressure to fall relaxing the ventricles.
• The second heart sound is associated with the closure of the semilunar valves (dub).
• The tricuspid and bicuspid valves are pushed open.
• The SAN generates a new action potential to repeat.
• The first sound lub and the second heart sound is dub during a stethoscope auscultation.

Blood Pressure

• Blood pressure is measured in mm Hg, with a normal range of 120-140/70-90.
• Normal pulse rate is 60-80 per minute.
• A sphygmomanometer measures blood pressure.
• Systolic pressure during heartbeats is 90-120 mm Hg.
• Diastolic pressure between heartbeats is 60-80 mm Hg.
• Hypertension is abnormally high blood pressure, exceeding 140/90 mm Hg.
• Stress and environmental factors impact blood pressure, with lifestyle and diet also playing a role.
• High Sodium results from processed foods, tobacco, and alcohol use.
• High blood pressure exhibits no clear symptoms, contributing to damage to the cardiovascular system, leading to atherosclerosis.
• Weight loss, a balanced low sodium diet, and increased calcium and vitamin D is recommended.
• Pulse Rate is heart beat dilation with artery pumping of blood due to heart beat.