Transportation In Plants And Animals

CloseArteries are thick-walled blood vessels that carry oxygen-rich blood away from the heart to various parts of the body. They have thick, muscular, and elastic walls because blood flows through them under high pressure. The largest artery is the aorta, which emerges from the left ventricle.

CloseCapillaries are the smallest and most numerous blood vessels. Their walls are only one cell thick, which allows oxygen, carbon dioxide, nutrients, and waste products to pass easily between the blood and body tissues. This exchange is the main function of capillaries.

CloseThe human heart has four chambers. The two upper chambers are called atria (singular: atrium) or auricles. They receive blood coming into the heart. The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs.

CloseThe ventricles are the two lower chambers of the heart. They have thicker muscular walls than the atria because they need to pump blood out of the heart with great force. The right ventricle pumps blood to the lungs, and the left ventricle pumps blood to the rest of the body.

CloseThe tricuspid valve has three flaps and is located between the right atrium and right ventricle. It prevents the backflow of blood into the right atrium when the right ventricle contracts. The bicuspid (mitral) valve is on the left side between the left atrium and left ventricle.

CloseThe aorta is the main and largest artery in the human body. It arises from the left ventricle and carries oxygenated blood to all parts of the body except the lungs. It is about 3-4 cm in diameter and branches into many smaller arteries.

CloseThe pulmonary artery is unique because it carries deoxygenated blood. It arises from the right ventricle and carries blood to the lungs for oxygenation. Most other arteries carry oxygenated blood, but the pulmonary artery is an exception.

CloseThe pulmonary vein is unique because it carries oxygenated blood. After blood picks up oxygen in the lungs, the pulmonary vein transports this oxygen-rich blood back to the left atrium of the heart. Most other veins carry deoxygenated blood.

CloseThe superior vena cava is a large vein that collects deoxygenated blood from the head, neck, arms, and chest (upper part of the body) and delivers it to the right atrium. The inferior vena cava brings blood from the lower part of the body.

CloseThe septum is a thick muscular wall that divides the heart into left and right halves. This separation prevents oxygenated blood (on the left side) from mixing with deoxygenated blood (on the right side), ensuring efficient oxygen delivery to the body.

CloseThe average weight of an adult human heart is about 250 to 300 grams (roughly the size of a fist). In females, it is slightly lighter (around 200-250 grams), and in males, it is heavier (around 250-300 grams). The heart grows from birth to adulthood.

CloseAn adult human heart pumps approximately 5 liters of blood per minute at rest. In one hour, that is 300 liters, and in 24 hours, it pumps about 7,200 liters of blood. This is enough to fill about 40 large bathtubs. The amount increases during exercise.

CloseRed blood cells contain hemoglobin, a protein that binds to oxygen in the lungs. As blood circulates, hemoglobin releases oxygen to all body tissues. RBCs are biconcave in shape to increase surface area for oxygen exchange. They have no nucleus in mammals.

CloseHemoglobin is an iron-containing protein pigment found in red blood cells. Iron gives blood its red color. Hemoglobin binds reversibly with oxygen to form oxyhemoglobin (bright red) in the lungs and releases oxygen in tissues (dark red). It also carries some carbon dioxide.

CloseWhite blood cells are the soldiers of the body. They protect against infections by engulfing bacteria (phagocytosis), producing antibodies, and destroying viruses and parasites. They are fewer in number than RBCs (about 1 WBC per 600 RBCs) but increase during infection.

ClosePlatelets are tiny, disc-shaped cell fragments without a nucleus. When a blood vessel is injured, platelets gather at the site, become sticky, and release chemicals that start the clotting process. This forms a plug that prevents further bleeding and allows wound healing.

CloseInsects like cockroaches have colorless blood called hemolymph. They do not have hemoglobin. Their blood does not carry oxygen; instead, oxygen is carried directly to tissues through a system of air tubes called tracheae. Hemolymph mainly transports nutrients and waste.

CloseThis is the main functional difference. Arteries always carry blood away from the heart (to the body or lungs), while veins always carry blood toward the heart (back from body or lungs). Additionally, arteries have thick walls and no valves (except semilunar valves at heart), while veins have thinner walls and valves.

CloseWilliam Harvey, an English physician, published his work “De Motu Cordis” in 1628. He was the first to correctly describe that blood circulates throughout the body in a closed system, pumped by the heart through arteries and returning through veins. He also proved that blood flows in one direction.

CloseThe pulmonary artery is the only artery that carries deoxygenated blood. It arises from the right ventricle, divides into left and right branches, and carries blood to the lungs. In the lungs, carbon dioxide is removed and oxygen is added to the blood.

CloseThe pulmonary vein is the only vein that carries oxygenated blood. There are four pulmonary veins (two from each lung) that carry freshly oxygenated blood from the lungs to the left atrium of the heart. From the left atrium, blood goes to the left ventricle and then to the body.

CloseThe left ventricle has the thickest muscular wall because it must pump blood under high pressure to the entire body (except lungs). It has to overcome high resistance in the systemic circulation. The right ventricle only pumps blood to the nearby lungs, so its wall is thinner.

CloseCapillaries form a network (capillary bed) between arterioles (small arteries) and venules (small veins). Their walls are one cell thick, allowing exchange of gases, nutrients, and wastes. No cell in the body is far from a capillary because diffusion is effective only over short distances.

CloseThis is the pulmonary circulation. Deoxygenated blood enters right atrium from vena cava, goes to right ventricle, is pumped through pulmonary artery to lungs. After picking up oxygen, blood returns via pulmonary veins to left atrium. Then it enters left ventricle for systemic circulation.

CloseVeins carry blood back to the heart under low pressure, and gravity can pull blood backward, especially in legs. To prevent this, veins have one-way valves (semilunar flaps) that open only toward the heart. When blood tries to flow backward, the valves close. Arteries do not need valves except at their origin from the heart.

CloseA normal resting heart rate for adults ranges from 60 to 100 beats per minute. Well-trained athletes may have a lower resting heart rate (40-60 bpm). Children have higher heart rates (70-120 bpm). Heart rate increases during exercise, fever, or stress and decreases during sleep.

ClosePlasma is the straw-colored liquid matrix of blood, consisting of about 90-92% water and 8-10% dissolved substances including proteins (albumin, fibrinogen, globulins), glucose, amino acids, hormones, urea, and salts. It helps in transport, maintaining blood pressure, and clotting.

ClosePlasma is the liquid part of blood, not a cellular component. The formed elements (cellular components) are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Plasma is the fluid in which these cells are suspended.

CloseHumans and all mammals have double circulation. Blood passes through the heart twice: first, deoxygenated blood is pumped from heart to lungs (pulmonary circulation), returns to heart, then oxygenated blood is pumped from heart to body (systemic circulation), and returns again. This allows efficient oxygen delivery.

CloseThe bicuspid valve (also called mitral valve) has two flaps and is located on the left side of the heart between the left atrium and left ventricle. It prevents backflow of oxygenated blood from the left ventricle into the left atrium when the ventricle contracts.

CloseSemilunar valves (pulmonary valve and aortic valve) are located at the exits of the ventricles. The pulmonary valve is at the base of the pulmonary artery (from right ventricle), and the aortic valve is at the base of the aorta (from left ventricle). They prevent blood from flowing back into the ventricles after contraction.

CloseCapillaries are the sites of exchange. Their thin walls (single layer of endothelial cells) allow oxygen, carbon dioxide, glucose, and wastes to diffuse between blood and tissues. They are so narrow that red blood cells must pass through in single file, which maximizes contact time for exchange.

CloseThe aorta is the main artery that arises from the left ventricle. It carries oxygen-rich blood to the entire body through its many branches (coronary, carotid, subclavian, mesenteric, renal, iliac arteries). It is the largest artery and has thick elastic walls to withstand high pressure.

CloseAn average adult human has about 5 to 6 liters of blood, which is about 7-8% of body weight. A person weighing 70 kg has approximately 5.5 liters of blood. Blood volume is lower in women and children. Loss of more than 1 liter can be dangerous.

CloseWilliam Harvey (1578-1657) is credited with the discovery of blood circulation. He performed experiments on animals, calculated blood volume, tied off veins to show valves, and demonstrated that blood flows from arteries to veins. His work overturned centuries-old beliefs of Galen.

CloseThis is the fundamental difference based on direction, not on oxygen content. All arteries (except pulmonary artery) carry oxygenated blood away from the heart. All veins (except pulmonary vein) carry deoxygenated blood toward the heart. Remember: Arteries = Away from heart; Veins = Toward heart.

CloseThe inferior vena cava is a large vein that collects deoxygenated blood from the lower parts of the body (abdomen, pelvis, legs) and brings it back to the right atrium. It is larger in diameter than the superior vena cava and carries blood at lower pressure.

ClosePulse rate is the number of heartbeats per minute. Each heartbeat creates a wave of pressure that can be felt as a pulse in arteries (e.g., at the wrist or neck). The normal pulse rate for adults is 60-100 beats per minute. It is the same as the heart rate.

CloseHemoglobin contains an iron atom in each heme group. When iron binds with oxygen, it forms oxyhemoglobin which is bright red. Without oxygen, deoxyhemoglobin is dark red (bluish through veins). The red color is because of the iron, not because blood is red like a red shirt.

CloseCockroaches and most insects have colorless or pale yellow blood called hemolymph. They lack hemoglobin and red blood cells. Oxygen is not carried by their blood; instead, it diffuses directly to tissues through a tracheal system. Their blood mainly transports nutrients, hormones, and waste.

CloseThe septum is the muscular wall that completely separates the left and right sides of the heart. This prevents oxygenated blood (left side) from mixing with deoxygenated blood (right side). Mixing would reduce the oxygen concentration of blood sent to the body, making circulation less efficient.

CloseBlood pressure has two readings. Systolic pressure (higher number, e.g., 120 mm Hg) occurs when the ventricles contract and push blood into arteries. Diastolic pressure (lower number, e.g., 80 mm Hg) occurs when the ventricles relax. Normal blood pressure is around 120/80 mm Hg.

CloseThe pulmonary artery is the only artery that carries deoxygenated blood. It originates from the right ventricle and takes blood to the lungs for oxygenation. It does not have valves at its origin (it has a semilunar valve at the heart but not along its length like veins).

CloseErythropoietin (EPO) is a hormone produced mainly by the kidneys. When oxygen levels in blood are low (hypoxia), the kidneys release EPO, which travels to the bone marrow and stimulates the production of more red blood cells. This increases oxygen-carrying capacity.

CloseCapillaries have the thinnest walls (single layer of endothelial cells) and no valves. They are the sites of exchange. Arteries have thick muscular walls and no valves (except at heart). Veins have thinner walls than arteries but have valves to prevent backflow.

CloseStroke volume is the amount of blood ejected by a ventricle with each heartbeat. In a resting adult, stroke volume is about 70 mL per beat. Cardiac output is stroke volume multiplied by heart rate (about 70 mL × 70 beats/min = 4900 mL/min or about 5 L/min).

CloseThe pericardium is a double-layered sac that surrounds and protects the heart. It contains a small amount of lubricating fluid (pericardial fluid) that reduces friction as the heart beats. The middle muscular layer is the myocardium, and the inner lining is the endocardium.

CloseIn humans, mature red blood cells lose their nucleus to make more space for hemoglobin. Platelets are cell fragments without a nucleus. White blood cells are the only blood cells that have a nucleus. This nucleus allows them to produce antibodies and enzymes for immune defense.

CloseSystemic circulation carries oxygenated blood from the left ventricle through the aorta to all body tissues. After oxygen is delivered, deoxygenated blood returns through the vena cava to the right atrium. This is the longer loop compared to pulmonary circulation.

CloseAfter the heart pumps blood into arteries, the blood is under high pressure (about 120 mm Hg systolic). Arteries need thick, muscular, elastic walls to withstand this pressure and to maintain the pressure wave. Veins carry blood under low pressure (about 0-10 mm Hg), so they have thinner walls.