Circulatory system – Transportation
Transportation / Circulation in humans:
As we know our body is made up of cells and nutrients and oxygen needed to survive, and wastes need to be removed from them. transportation of nutrients, gases, wastes, and other substances from one part of our body to the other part, is carried out by blood. In simple words transportation in humans is carried out with the circulation of blood. Since blood passes twice through the human heart, it is termed Double circulation
Function of transportation
- Transport of nutrients to the tissues for their utilization
- Transport of respiratory gases (O2 and CO2) to and from the cells.
- Collection of metabolic wastes from tissues and transporting them to excretory organs for their removal.
- Uniform distribution of heat in the body
Organs involved in transportation -Heart, Blood vessels, Blood, lymph nodes, and lymph vessels.
The heart of human
- The heart is a mesodermally derived organ.
- It is a muscular organ made of cardiac muscle fibers.
- The central pumping organ. consists of 4 chambers, two upper chambers – the atria and two lower chambers – the ventricles. These chambers prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide.
- It performs its function by coordinating contraction and, relaxation and opening and closing of a number of valves present inside the heart.
- The heart is covered by a membrane – the pericardium
- Ventricles consist of thick muscular walls for pumping blood to longer distances.
The valve inside the heart regulate the flow of blood by opening on one side to let blood flow out in one direction only and they prevent the backflow of blood these are-
Right atrioventricular valve or tricuspid valve and Left atrioventricular valve or bicuspid valve. Semilunar valves are situated at the origin of the aorta and pulmonary artery.
A wave of contraction in the heart is conducted from S.A. node to A.V. node to bundle of HIS, to Purkinje fibers.
Transportation process through the heart–
- the blood carries both oxygen and carbon dioxide both so the chamber of the heart prevents the mixing of blood. The carbon dioxide-rich blood goes to the lungs and from here the CO2 gets removed.
- The oxygenated blood from the lungs is brought back to the heart. (oxygenated blood-oxygen rich blood)
- Then this oxygenated blood pumped throughout the body.
The mechanism of whole transportation/ circulation takes place through pathway–
- Oxygen-rich blood goes from the lung to the left atrium of the heart, on the time of receiving this blood The left atrium relaxes.
- In the second step left atrium contracted bicuspid valve opened while the next chamber, the left ventricle, relaxes by this process blood is transferred to the left ventricle.
- left ventricle contracts in its turn the blood is pumped out to the body.
- The right atrium relaxes and then it receives De-oxygenated blood from the body.
- When the right atrium contracts, the tricuspid valve opened the (lower chamber) the right ventricle expands. By this transfers blood to the right ventricle, which pumps the blood to the lungs for oxygenation. As the process of circulation, the oxygenated blood goes through the body.
- Ventricles pump blood to various organs they contain thicker muscular walls than arteries.
- During the contraction of atria or ventricles, the valve prevents the backflow of blood.
Function Major arteries and veins
- Superior vena cava brings deoxygenated blood from the head and shoulder region.
- Inferior vena cava brings deoxygenated blood from the lower parts of the body. These vena cava open in the right atrium Contraction of the right atrium forces this blood into the right ventricle.
- Contraction of the right ventricle pumps blood into the pulmonary artery which transports blood to the lungs. Blood gets oxygenated in the lungs and returns to the left atrium through the pulmonary vein.
- The left ventricle pumps blood into the aorta. The aorta distributes blood throughout the body.
The pulmonary artery is the only artery that carries the de-oxygenated (blood poor in O2) blood. It is called an artery as it carries blood away from the heart.
The pulmonary vein is the only vein that carries oxygenated blood (blood rich in O2). It is called a vein as it carries blood into the heart
Heartbeat- the beating of the heart goes on by itself as long as one is alive.
- It starts with the contraction of atria systole followed by relaxation or diastole. The lubb sound or 1st heart sound occurs due to the closure of atrioventricular valves, the atrial systole.
- Contraction of ventricles followed by relaxation accompanied by the dubb sound or the 2nd heart sound occurs due to closure of semilunar valves.
- The flow of the blood in the arteries exerts pressure on their elastic walls. This pressure is called blood pressure. The pressure of blood at the time of ventricular contraction is higher and is called systolic pressure. When ventricles are relaxed and are being filled with blood, there is a drop in pressure. This lower pressure is called diastolic pressure.
- The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg Blood pressure is measured by an instrument called a sphygmomanometer.
Electro Cardiogram (ECG) is the instrument that records the conduction of heartbeat. This helps in detecting heartbeat disorders
Blood vessels– The tubes transporting blood are called Blood Vessels. The wall of a blood vessel has three layers, tunica externa, tunica media, and tunica interna. These are of three types (i) Artery (ii) Capillary and, (iii) Vein
Artery – Since the blood carried from the heart under high pressure, the arteries have thick, elastic walls. Arteries are the vessels that carry blood away from the heart to various organs of the body
After reaching an organ or tissue the arteries divides into small vessels to get blood in cells.
The smallest vessels have walls that are one-cell thick and are called capillaries
Veins collect the blood from different organs and bring it back to the heart and there is no high pressure as the valve helps to prevent the backflow of blood. So in comparison to arteries, these are thin.
- Plasma – Plasma is a fluid part of the blood and is composed of 90% of water.
- Blood Cells-Red blood cells, white blood cells, and platelets constitute the solid part of the blood
- (we will study the explanation of blood in another blog.)
maintenance by platelets– to avoid continue bleeding blood has platelet cells that circulate around the body and plug these leaks by helping to clot the blood at these points of injury.
Lymph– The clear, colorless liquid moving out of the capillary wall is called Lymph. Lymph comes into direct contact with body cells. The spleen and tonsils are lymphoid organs.
Functions of lymph–
- Supplies nutrition and oxygen to those parts of the body where blood cannot reach
- Drains away, excess tissue fluid from extracellular spaces and pours back into the blood.
- Absorbs and transports fats absorbed from the small intestine (lacteals)
- Collects nitrogenous waste
- Lymphocytes and antibodies present in lymph help in removing bacteria
Circulation in some other animals –
- The circulatory system may be open or closed type Open circulatory system- Blood does not flow in closed vessels rather it flows through parts of the body cavity. It remains mixed with the body fluid.
- For example- The circulatory system of cockroaches is of open type.
- Animals, like amphibians or many reptiles, have three-chambered hearts and they having a mixed stream of oxygenated and deoxygenated bloodstreams.
- Fishes having only a two-chambered heart, and the blood is pumped to the gills, get oxygenated in gills, and passes directly to the rest of the body. Blood goes only once through the heart in the fish during one cycle of passage through the body.
- In these organisms energy requirement is low, so there is no need of high efficiency of oxygen that’s why here single pathway or single circulation occurs.
Transportation/ Circulation in plants
Transportation –It is a vital process in plants. Plants transport all the nutrients and water which is needed for survival from their roots to the tips of the leaves. The water and mineral are mostly observed from the root, some exceptions as aquatic plants. As such in animals, the plants also do the transportation of nutrients to cells by means of circulation.
- As we know the soil is the nearest and richest source of raw materials like nitrogen, phosphorus, and other minerals so it is taken from roots.
- CO2 is obtained from the surrounding through the minute pore of leaves called stomata.
In-plant transport systems, movement of energy from leaves and raw material from root takes place in different pathways followed by two types of tissues-
- xylem -Transport of water
- phloem- Transport of food and other substances
Transport of water–
Xylem is a long, non-living tube which is running from the roots to the leaves through the stem. Vessels and tracheids of the roots, stems, and leaves are interconnected in the xylem to form a continuous system of water-conducting channels reaching all parts of the plant. The water gets absorbed by root hair and undergoes cell to cell movement by osmosis until it reaches the xylem. After this, the water transported through the xylem vessels into the leaves and is evaporated by the process of transpiration.
Transpiration -It is the process in which evaporation of water takes place through openings known as stomata. A pull is created by replacing the water that evaporated. This pull in the xylem tissues goes all due to the cohesive forces. This is negative water pressure that occurs in the roots led eventually result in an increased uptake of water from the soil.
- Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves.
- It also helps in temperature regulation in plants. The stomata open during daytime; the transpiration pull becomes the major driving force in the movement of water in the xylem.
Transport of food and other substances– The phloem is responsible for translocation (This transport of soluble products of photosynthesis is called translocation) of nutrients and sugar like carbohydrates amino acids and other substances in plants produced by leaves to all metabolically active area these are roots, fruits, and seeds to growing organs.
- Phloem is made up of living cells. The cell wall of these cells forms small holes at the ends of the cells called sieve tubes.
- Translocation in phloem utilizes energy and it is done by a pressure called osmotic pressure, with the help of the pressure, materials get able to move in low concentration and moves according to the need of the plant.
We can see the role of osmotic pressure in the example, in the spring season, the sugar stored in root and stem tissues translocated to the buds with the help of energy.
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