Cells

Kelly Ann Wright Physiology Access to Health Sciences 1) Describe the main components of the blood. Blood is composed of two components: Plasma, a watery liquid which contains dissolved substances and formed elements, which are cells and cells fragments. The blood consists of about 45% formed elements and 55% plasma. Plasma itself is around 90% water and the remaining 10% is made up of dissolved solutes such as, minerals, urea, glucose and hormones, also containing plasma proteins such as albumin and immunoglobulins (antibodies that fight infection), these proteins never leave the blood. Without plasma, blood cells would have no medium to travel on as they travel throughout the body. The formed elements of the blood include three principle components which are Red blood cells (Erythrocytes), White blood cells (Leukocytes) and platelets. Red blood cells are the most common cell in the blood and carry oxygen around the body from the heart. Erythrocytes contain an oxygen carrying protein called haemoglobin, a pigment that gives blood its red colour. They are biconcave discs with a diameter of 7-8 um, and their plasma membrane is strong and flexible which allows the red blood cell to change shape without rupturing as they squeeze through the narrow capillaries. Red blood cells lack a nucleus and organelles giving it a larger surface area to carry more oxygen. The typical lifespan of a red cell is 90-120 days. (class notes) Figure 1 Figure 2 Figure 3 Neutrophills are the most common type of white blood cell comprising of about 50-70% of all white blood cells. They contain non staining granules and are phagocytic meaning that they can ingest other cells, though they do not survive the process. Neutrophills are fairly uniform in size with a diameter between 12 and 15 micrometres. The nucleus consists of 2-5 lobes which are joined together by hair like filaments Neutrophills are the first immune cells to arrive at a site of infection, through a process called chemotaxis(a force of attraction that determines the direction of which the neutrophills move.) Though nuetrophills are short lived with a life of 12-72hrs they are plentiful and replaced at the rate of 100 000 000 000 per day. Non granular leukocytes include monocytes and Lymphocytes. Monocytes are the largest of the leukocytes(white blood cells), making up between 1-3% of the total. They have a large bean shaped nucleus, and the cytoplasm is blue-grey with a foamy appearance. These cells are made in the bone marrow, spreading throughout the body over a period of one to two days before moving into the tissues, enlarging into phagocytic macrophages. They attack any foreign material such as bacteria or virus, consuming it so that it cannot harm the body also preserving an antigen which helps the body to recognize as harmful. Tortora grabowski (2000) Kelly Ann Wright Physiology Access to Health Sciences Blood platelets(Thrombocytes) are irregularly shaped colourless bodies around 2-4um in diameter and are between 150,000 and 400,000 platelets present in each um of blood. They are fragments of cells that help blood clot when necessary. They have sticky proteins on their outer surface and have the ability to stretch and change shape, helping stop blood loss from damaged blood vessels by forming a platelet plug. They exhibit many granules which contain many chemicals that promote blood clotting. Thrombocytes have a life span of 5-9 days and any aged or dead platelets are removed by macrophages in the spleen and liver. Tortora Grabowski (2000) Figure 4 http://waycoolpics.blogspot.com/2008/07/blood-its-kinda-cool.html Figure 4 illustrates how the thrombocytes gather at the sites of injury producing clotting factor 2)Describe the physiological processes involved and how oxygen and carbon dioxide are transported in the blood. The main role of the transport system is to transport oxygen to the alveoli to the cells around the body as oxygen is needed to keep the cells alive. Oxygen is carried in red blood cells(Erythrocytes ) bound to the protein haemoglobin. Haemoglobin which is present in the cytoplasm of the red blood cell is the chemical that carries the respiratory gases around the body. A haemoglobin molecule consists of a protein called globin, which is composed of four polypeptide chains, two alpha and two beta and four non protein pigments called hemes. Each haem contains one iron atom that combines with an oxygen molecule. The oxygen that is picked up in the lungs is then transported to other tissues in the body where the iron-oxygen reaction is then reversed. The haemoglobin releases the oxygen which diffuses into the interstial fluid and then into the cells. Clegg and mackean (1994) Figure 5 Figure 6 5)http://www.lifescript.com/Health/A-Z/Conditions_A-Z/Conditions/P/Porphyria.aspx 6)http://www.pharmainfo.net/reviews/artificial-blood-current-review Kelly Ann Wright Physiology Access to Health Sciences Haemoglobin also transports around 23% of carbon dioxide. Carbon dioxide enters red blood cells in the tissue capillaries where it then dissolves in the water that is contained within the cell to form carbonic acid (H2CO3). This reaction is catalysed by the enzyme carbonic anhydrase which increases the rate of production of the carbonic acid. The carbonic acid then breaks up forming hydrogen ions and bicarbonate ions. This reaction also occurs outside the red blood cells in the plasma but is a much slower process due to the lack of carbonic anhydrase. The hydrogen ions that are produced from the breakdown of carbonic acid combine with haemoglobin in the red blood cell, and the bicarbonate ions react with the hydrogen ions forming carbon dioxide and water. Clegg and Mackean (1994) Q3a)Describe the structure of the three types of blood vessel and their role in the closed system The blood is carried around the body through arteries, veins and capillaries. The artery is the blood vessel that carries oxygenated blood away from the heart. They vary in size depending on their position in the body and how far away from the heart they are. Arteries are composed of thick muscle and elastic fibres, these thick walls enable them to withstand the pressure created by the pumping of the heart. Arteries consist of an inner lining, one cell thick, called endothelium (Tunica intima) a middle layer of smooth muscle and elastic tissue(Tunica media) and an outer layer that is mostly loose connective tissue (Tunica adventria) which holds the multi layered tube together. The muscle layer in arteries and arterioles is thick and the overall structure quite elastic, enabling them to withstand greater blood pressure than can veins. Arteries contain about 20% of blood at any time. Veins carry de oxygenated blood back to the heart. They have the same three layers as arteries, but they have less muscle and elastic tissue in the tunica media making their walls thinner. Unlike arteries, veins have valves that allow blood to flow in one direction, back to the heart. These valves help maintain blood flow where blood pressure has to push blood upwards. The smallest of the veins, which are furthest from the heart are known as venules. Veins contain about 75% of blood at any time. Capillaries are the shortest, narrowest and thinnest blood vessels and connect arterioles to venules completing the circuit. Capillaries consist of a single layer of endothelial cells with some connective tissue binding the cells. Capillaries act as a link between arteries and veins and there are no valves present. Capillaries contain about 5% of blood at any time The arteries, veins and capillaries are described to be in closed system as the blood never comes into contact with any of the other cells in the body, staying in the blood vessels where oxygen is diffused through the cell wall of the capillary. Kent (2000) Kelly Ann Wright Physiology Access to Health Sciences 3b) Explain why the circulation is described as being a 'double' system The double circulatory system is referred to as two separate pumps, One being that of the pulmonary circulation and the other in the systematic circulation. The human heart has two pumps, one on the left with the left atrium and ventricle and one on the right along with the right atrium and ventricle. The left side pumps the oxygenated blood into the systemic circulation and the right side pumps de oxygenated blood to the pulmonary circulation. Seymour (2000) Figure 7 http://agingresearch.buffalo.edu/assets/images/chfcirculatory Figure 7 is a demonstration of the double circulatory system. Within the system there are many valves. There are three primary types. The first is called the bicuspid valve and is located between the left atrium and the left ventricle. The purpose of the valve is to allow the oxygenated blood to flow from the left atrium to the left ventricle during ventricular relaxation. The bicuspid valve also stops the blood from flowing back into the left atrium during the ventricular contraction. The second of the main valves is the tricuspid valve, and this is found between the right atrium and the right ventricle. This allows the de oxygenated blood to run from the right atrium to the right ventricle during ventricular relaxation. It also prevents the blood flowing back into right atrium during ventricular contraction. The final valves are two valves called the semiunar valves, found at the beginning of the arteries leaving the heart. The reason it is called the double circulatory system is because it has two loops, one from the heart to the lungs, and one from the heart to the rest of the body. The double circulatory system is a big advantage, as the blood can be pumped to the rest of the body at a higher pressure. Seymour (2000) Kelly Ann Wright Physiology Access to Health Sciences 4)Tissue fluid formation is an important part of circulation. Explain how it is produced and re-absorbed. Hydrostatic pressure is produced when blood passes from the arterioles into the narrow capillaries, this pressure pushes fluid through the capillary walls. The fluid is known as inter cellular and is called tissue fluid; this then bathes all the cells. The tissue fluid contains many different molecules, such as glucose, amino acids, fatty acids, salts and oxygen. These are essential for the maintenance of the cells. When this happens the cells produce carbon dioxide and other waste products, and it is only when the tissue fluid returns to the circulation, that the waste can be removed from the tissue. The way that materials are exchanged between blood and tissues is by the means of the tissue fluid. Osmosis occurs when most of the tissue fluid passes back into the venules. Because the plasma proteins that are in the blood are to big to pass through the capillary walls, this creates an osmotic pressure. The tissue fluid is drawn back into the blood due to this pressure,and any fluid that does not return this way gets passed through to the lymph vessels, which are then called lymph. Www.s-cool.co.uk Q5) Describe the structure of the heart and what happens during the cardiac cycle. What role does the sino-atrial and atrioventricular nodes, the autonomic nerves and any relevant hormones, in this process. The heart is a cardiac muscle that is composed of cells named myocytes. It weighs between 7 and 15 ounces and is surrounded in a double layered membrane called the pericardium. The heart comprises of four chambers, the upper chambers are called the left and right atria and the lower chambers are the left and right ventricles. A wall of muscle called the septum separates the left atrium and ventricle from the atria and ventricle on the right. Between the atria and ventricles are atrioventricular valves which prevents the return of blood to the atrium. The left valve consists of two flaps and is called the bicuspid or mitral valve. The valve on the right however has three flaps and named the tricuspid valve. These valves are held together by valve tendons. There are also two semi lunar valves present in the arteries called the pulmonary and aortic valves. Tortora Grabowski (2000) Figure 8 http://www.niaaa.nih.gov/RESOURCES/GRAPHICSGALLERY/CARDIOVASCULARSYSTEM Kelly Ann Wright Physiology Access to Health Sciences The rhythmic series of muscular contractions in the heart comprise the cardiac cycle. This cardiac muscle contract on its own without the need for any nerve impulses( myogenic). It is a small mass of cardiac muscle fibres called the syno-atrial node located in the the right atrium that acts as a pacemaker and keeps the heart regulated. The cardiac cycle can be divides into three separate phases: atrial systole, ventricular systole and Diastole. During Atrial systole the sino-atrial node when contracted transmits electrical impulses into the atria, the atria then contract and in doing so push the blood into the ventricles. In ventricular systole, The electrical signals in the atria are then picked up by the atrioventricular node which passes the signal down to the bottom of the ventricles. The signal is passed through the ventricles through specialised fibres called the bundle of his and spread through the ventricles along purkinje fibres. Once the ventricles have filled up with blood they contract from the bottom up, and squeeze the blood up into the pulmonary arteries. The atrioventricular valves are forced shut preventing blood from entering the atria. Grabowski (2000) The sequence that follows the contraction of both the atrial systole then ventricular is known as diastole. After the ventricles have started to contract the atria begins to relax, this is called atrial systole. Once the blood has left the ventricles ventricular diastole begins. The semi lunar valves close as the ventricles start to relax. The heart beat is also controlled by nerve messages originating from the autonomic nervous system. The autonomic nervous system controls the firing of the sino-atrial node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sino-atrial node so it in turn can increase the heart to twice its normal rate within 3-5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen. The autonomic nervous system provides the heart with a double set of nerves, the sympathetic and the parasympathetic. The sympathetic activates and prepares the body for vigorous muscle activity, stress and emergencies and the parasympathetic lowers activity and operates during normal activity. These two systems generally work in opposition to one another. The adrenal medulla, the inner part of the adrenal gland which are located on top of both kidneys in the body. In times of acute stress the brain and spinal cord send a signal to the adrenal medulla, and secretes epinephrine (adrenaline) and nor epinephrine into the bloodstream. This causes the heart to beat faster, and gets the body ready for physical activity. Glass (2004) Q6) Describe the various structures that make up the respiratory system. Explain how they are involved in ventilation and gaseous exchange. The primary function of the respiratory system is to supply the blood with oxygen so that the blood can deliver oxygen to all parts of the body. All cells metabolically consume oxygen and discharge carbon dioxide. The respiratory system is situated within the thoracic cavity. It is structurally divided into two sections. The upper respiratory system, which includes the nasal cavity, pharynx and other associated structures and the lower respiratory system which includes the larynx, trachea, bronchi, lungs and diaphragm. Kittredge (2000) The nose is the only visible part of the respiratory system that is visible externally. The framework of the nose consists of bone and cartlidge, with connective tissue and skin covering it. The nose has As air is breathed in through the nostrils it enters the nasal cavity, which is then dived into two by the nasal septum. The primary function of the nasal cavity is to smell and to warm the incoming air that enters the nostrils. The nasal cavity is lined with cells that produce mucus. Small foreign matter that enters the cavity gets trapped in the mucus, while small tiny hairs called cilia, push the mucus to the pharynx (throat) , which gets swallowed and digested in the stomach or expectorated. Kelly Ann Wright Physiology Access to Health Sciences The pharynx is connected to the buccal cavity ( nose and mouth). The upper part of the pharynx lets only air pass through and the lower part permits air, food and fluids to pass. The larynx also referred to as the voice box or glottis is the passageway for air between the pharynx and the trachea. It is formed by nine cartlidges that are connected to one another by muscle and ligaments. The voice tone is generated here and just above this position is a flap of elastic cartlidge tissue called the epiglottis. The epiglottis is covered with a mucus membrane, attached to the root of the tongue and during swallowing it is the epiglottis that covers the larynx to prevent food and liquids entering the respiratory system. Attached to the larynx is the trachea. Kent, M. (2000) The trachea which is also commonly refereed to as the windpipe is the main airway passage to the lungs. It is a flexible tube, 10-12cm long, and normally held open by up to twenty C-shaped rings of cartlidge. The tubes that are contained in the trachea have cells that produce mucus or cilia. The mucus is a slippery secretion produced and covers the mucous membranes. This contains antiseptic enzymes such as lysosome and immunoglobulin which protects the epithelial cells in the respiratory system. The cilia are tiny hairs that protect the nasal passageways and other parts of the respiratory tract. The duty of these tiny hairs is to filter out dust and other foreign particles that enter the nose that is breathed into the body. These move back and forth, pushing any foreign particles either towards the nostrils, where it is blown out, or towards the pharynx, where it travels through the digestive system and out of the body with other waste. Kittredge (2000) The trachea branch out in to two smaller branches called bronchi, which connect to the lungs. Within the lungs the bronchi then divide many times into smaller passageways called the bronchioles. It is the bronchioles that control the airflow resistance and air distribution in the lungs. At the end of each bronchiole within the lung tissue are thousands of small air sacs, called the alveoli. The alveoli are chambers of around one cell thickness. Their walls are extremely thin and they have a large surface area in relation to their volume. They have numerous capillaries which are fluid lined to allow gases to dissolve. They are structured this way for the efficiency of gaseous exchange. The alveoli are important as this is where the exchange of oxygen and carbon dioxide takes place within the body. Oxygen from the inhaled air diffuses through the walls of the alveoli to the red blood cells, where it is then carried by the blood to the body tissue. Carbon dioxide produced by the body returns to the lungs via the blood, where it is diffused through the capillaries and alveoli walls and removed from the body during expiration. The lungs also contain elastic tissues that allows them to inflate and deflate without losing shape and are encased by a thin lining called the pleura. The pleura are a serous membrane which folds back onto itself to form a two layered membrane structure. The thin space between these membranes is known as the pleural cavity and the fluid present within is created due to the work of the golgi complex. The fluid lubricates the lungs during inspiration, so that the lung can expand without any friction occurring. The human ribcage or thoracic cage is a component of the respiratory system and encloses and protects the thoracic cavity which contain the lungs and other vital organs. Just across the bottom of the ribcage is the diaphragm. Tortora and Grabowski (1999) Pulmonary ventilation, otherwise known as breathing, exchange gases between the outside air and the alveoli of the lungs. Ventilation depends on a difference between the atmospheric pressure and the pressure in the alveoli of the lungs. Air flows between the atmosphere and the lungs because of alternating pressure differences created by contraction and relaxation of the respiratory muscles. Just before inhalation/inspiration, the air pressure in the lungs is equal to the pressure of the atmosphere. In order for air to flow into the lungs, the pressure inside the alveoli must become lower than the atmospheric pressure. This is achieved by increasing the volume of the lungs. During inspiration the lungs expand to increase lung volume, this decreases the pressure in the lungs to below atmospheric pressure. It is the diaphragm that begins the first step to expand the lungs. The diaphragm is a dome shaped skeletal muscle situated below the thoracic cavity, that separates the thoracic and abdominal cavities. When the diaphragm contracts it flattens and the Kelly Ann Wright Physiology Access to Health Sciences size of the thoracic cavity increases, lowering the pressure on the lungs. When the intercostal muscles, which are situated between the ribs, contract,the ribs move up and out. By contracting the ddiaphragmnd intercostal muscles reduce the internal pressure compared to the atmospheric pressure. As consequence air rushes into the lungs. During expiration the opposite happens. The diaphragm relaxes, and its dome curves back up into the thoracic cavity, while the intercontinental muscles relax, bringing the ribs down and inwards. As the diminished size of the thoracic cavity increases the pressure in the lungs, forcing out the air. Www.scienceclarified Q7) What is the role of diffusion in gaseous exchange and explain how the properties of the respiratory surface are involved in this process. Gas exchange, takes place at a respiratory surface or cell membrane. These gases cross the respiratory surface by diffusion. According to www.mrothery.co.uk Ficks law predicts that these respiratory surfaces must have A large surface area A thin permeable surface A moist exchange surface The actual respiratory surface is on the alveoli in the lungs. The walls of the alveoli are composed of a single layer of flattened epithelial cells, as are the walls of the capillaries, so gases need to diffuse through just two thin cells. Water diffuses from the alveoli cells into the alveoli so that they are constantly moist. Oxygen dissolves in this water before diffusing through the cells in the blood, where it is taken up by haemoglobin in the red blood cells. The water also contains a soapy surfactant which reduces its surface tension and stops the alveoli collapsing. The alveoli also contain phagocyte cells to kill any bacteria that have not been trapped by the mucus. Diffusion occurs when molecules move from an area of high concentration to a low concentration. This happens in gaseous exchange as the blood in the capillaries that surround the alveoli has a lower oxygen concentration of oxygen than the air in the alveoli that has just been inhaled. As the alveoli and capillaries have very thin walls, it allows the gases to diffuse across them. The same happens with carbon dioxide. The blood in the surrounding capillaries has a higher concentration of carbon dioxide than the inspired air due to it being a waste product of energy production. Therefore the carbon dioxide diffuses the other way, from the capillaries into the alveoli, where it is then exhaled. Www.mrothery.co.uk Kelly Ann Wright Physiology Access to Health Sciences Q8a) According to www.medical-dictionary.com,The definition of tidal volume is the amount of air inhaled and exhaled during normal ventilation. Inspiratory reserve volume, expiratory reserve volume and tidal volume make up vital capacity. The term vital capacity is defined by www.everythingbio.com as the maximum amount of air that a person can expel from the lungs after first filling the lungs to their maximum extent. The www.medical-dictionary.com explains that inspiratory capacity means the maximum volume of gas that can be inhaled from the end of a resting exhalation. It is equal to the sum of the tidal volume and the inspiratory reserve volume, and measured with a spirometer. According to www.greenfacts.org the ventilation rate is the amount of air inhaled in a specific time period (e.g.,per minute, per hour, per day, etc.) The ventilation rate is also known as the breathing and inhalation rate. (http://www.frca.co.uk/article.aspx'articleid=100023) Figure is a demonstration of how tidal volume, vital capacity, inspiratory capacity and ventilation rate might look on a graph if it was tested on a person. Q8b) 1. The normal value associated with tidal volume is O.5dm³ 2. The normal values associated with the vital capacity for males is 4.5dm³ and for females, 3.2dm³ Q8c) Name an instrument that could be used to determine experimentally the lung capacities. The instrument that could be used to determine experimentally the lung capacities is a spirometer. The spirometer mechanically measures the respiratory system's expiratory volumes and rates. Kelly Ann Wright Physiology Access to Health Sciences Q9a) What is the % composition of inspired and expired air' GAS | Percentage atmospheric (inspired) air | Percentage exhaled air | Water vapour | A little | A lot | Oxygen | 21.00% | 16.00% | Nitrogen | 79.00% | 79.00% | Carbon dioxide | 0.04% | 4.00% | Q9b) Explain the significance of the difference between them During respiration, food in the form of sugar is oxidised by the oxygen. The products of respiration are, Oxygen, Carbon dioxide and Water vapour. During repiration, living things take in oxygen from the air to produce energy and remove carbon dioxide and water vapour, thus the percentage of oxygen gas is higher in inhaled air, compare to exhaled air. In contrast, the percentage of carbon dioxide gas is lower in inhaled air compared to exhaled air. And the percentage of nitrogen and inert gases remain the same in inhaled and exhaled air, this is because both nitrogen and inert gases do not take part in respiration. Exhaled air contains more water vapour than inhaled air, because water vapour is released as a product of respiration. References Clegg, C J. and Mackean, D J, (1994) advanced biology, principles and applications Glass, S. (2004) The circulatory system. perfection learning Kent, M. (2000) Advanced Biology, Oxford university Kittredge, M. (2000) The respiratory system, chelsea house publishers http://www.mrothery.co.uk/ accessed January 2011 http://resources.schoolscience.co.uk/abpi/heart/heart2.html accessed January 2011 http://www.scienceclarified.com/Qu-Ro/Respiratory-System.html accessed January 2011 Seymour, S. (2000) Our circulatory system, mulberry books. Tortora, G J. and Anagnostakos, N P. (1987) Biology a functional approach Tortora, G J. and Grabowski, S R. (1999) Principles of anatomy and physiology, John Wiley and sons