The name given for the circulation that takes place to and from the lungs is pulmonary circulation. Circulation around the body is called systemic circulation. Blood vessels take blood away from the heart are called arteries, as for those that deliver blood to the heart, these are called veins. With pulmonary circulation, the pulmonary artery is what takes deoxygenated blood through the right ventricle and delivers it to the lungs. The pulmonary veins then deliver oxygenated through the left atrium.
The aorta is the main artery that is exiting from the left ventricle and the vena cava is the principle vein that is taking blood back into the heart. The vena cava has two parts to it, which are the superior vena cava and the inferior vena cava. The superior vena cava takes the blood from the head and neck back to the heart as for the inferior vena cava that takes the blood from the rest of the body to the heart. Valves are what make sure that blood travels only in one direction. There are two types of valves which are located within the distance of the atria and the ventricles. These twp types are called the right and left atrio-ventricular valves. Valves are formed of cusps which are very narrow, this is so that they do not go inside out with the pressure of the blood that is flowing. These have cords which connect to their free ends and are attached by petite papillary muscles to the ventricles heart muscles. The papillary muscle because hard just before the pressure of the muscle in the ventricle start to contract, the tendous cords are what holds the valves in position. The pulmonary and the aorta are arteries which have valves called semi-lunar valves. Blood is pushed into the arteries through ventricular muscle contractions, this blood cannot go back into the ventricles one they have relaxed.
The cardiac cycle:
The cardiac cycle is a cycle of events that take place when the heart contracts. The cardiac cycle consists of two phases which are the diastole phase and the systole phase. The diastole phase is where the atria and the ventricles relax. It is in the right and left atria where blood is flown. The valves which are situated between the distance of the atria and ventricles tend to be open, in order to let blood travel to the ventricles. As the systole phase is occurring the ventricle contract blood that has been pumped into the arteries. The lungs receive blood through the pulmonary artery which originally received the blood from the right ventricle. The left ventricle is what transports blood to the aorta.
According to Stretch and white house (2007):
The events in the cardiac cycle can be described in stages as follows:
- Both atria contract forcing blood under pressure into ventricles.
- Ventricles are bulging with blood and the increased pressure forces the atrio-ventricular valves shut (giving rise to the first heart sound-lubb)
- Muscle in the ventricular walls begins to contract, pressure on blood inside rises and forces open the semi-lunar valves in the aorta and pulmonary artery.
- Ventricular systole forces blood into the aorta (left side) and pulmonary artery (right side). These arteries have elastic walls and begin to expand.
- As the blood leaves the ventricles, the muscle starts to relax. For a fraction of a second blood falls backwards, catching the pockets of the semi-lunar valves and making them close (the second heart sound-dup).
- With the ventricles in diastole, the atrio-ventricular valves are pushed open with the blood that has been filling the atria. When the ventricles are about 70 per cent full, the atria contract to push the remaining blood in rapidly and the next cycle has begun.
The heart is constantly filled with blood. The cycle of events is constantly occurring and when the heart rate is high, the time that it takes to fill the heart, with blood, is shortened.
Heart rate and stroke volume:
The total amount of blood that leaves the heart within one minute is known as the cardiac output. In order to work out the cardiac output the amount of blood that is released from the left ventricle in one beat and also the number of beats that occur within a minute. The number of beats that occur within a minute is known as heart rate and the amount of blood that is secreted from the left ventricle is called stroke volume. An average human being has the stroke volume of 70cm3 and the average heart rate is between 60 to 80 beats a minute.
Blood pressure:
Blood pressure (BP) is the force/pressure that the blood has on blood vessels when it is flowing past. Blood pressure can be obtained through the use of a machine called a sphygmomanometer. Blood pressure is usually written as a systolic and diastolic fraction. For example 120/80 (average BP for a healthy adult) = systolic/diastolic. The systolic BP shows the force of the blood when ventricles are contracting. As for the diastolic, it is the opposite it shows the pressure on the walls of the ventricles when they are relaxed and taking in blood. Blood pressure is measured in units of mm Hg. Blood pressure seems to be at its highest in vessels such as the aorta and large arteries as they are located close to the heart. Blood pressure quickly decreases as blood is pumped through the arteries and the arterioles, this is due to the fact the vessels have a certain amount of resistance. The blood pressure that is the capillaries tends to usually be quite low, therefore the blood in the veins is pushed back to the heart though the help of a muscle pump. Veins within the limbs are found in muscle groups, this is because there walls a quite narrow compared to arteries and have valves in the spaces. Muscles compresses the blood uphigh into columns and valves are what prevent it from flowing backwards.
Blood vessels - Ateries and arterioles:
Arteries are what carry blood away from the heart, they provide blood to the arterioles (which are smaller blood vessels. The arterioles then supply blood to the capillaries. Oxygenated blood is what is usually transported by the arteries, apart from the pulmonary and umbilical arteries. The arterioles has a large network which provides blood to the capillaries, it is in being able to overcome the resistance of these muscular vessels that blood pressure tends to decrease. Endothelium is what forms the lining of arteries and arterioles. Arteries and arterioles have a muscular outlining and there lumen is circular shaped.
Capillaries:
Capillaries supply nutrients and oxygen to the body’s cells. In the capillaries a protein free plasma filtrate is released from the capillaries arterial ends and this plasma is what gives nutrients and oxygen to body cells. This is tissue fluid which enters the capillaries again through the venous and as this is occurring it takes waste products of the body cells.
Venules and veins:
Venules are little veins which are provided for by capillaries and fed into veins. The vena cava is the largest vein and this vein goes into the heart through the hearts right atrium. Limb veins have valves which help in ensuring that blood flows back to the heart, this is due to low blood pressure being in the veins. Compared to arteries veins have a much thinner muscular coat, it also has more fibrous tissue and a lumen that is oval. Low blood pressure is located in the veins and venules. Veins apart from the pulmonary and umbilical arteries carry deoxygenated blood.
Pulmonary and systemic circulations:
Pulmonary circulation is the name that is given for the circulation of blood that is going to the lungs and leaving the lungs. Systemic circulation is the given name for the circulation of blood around the body. The pulmonary circulation involves the pulmonary arteries transporting deoxygenated blood that has come from the right ventricle into the lungs. As this is occurring the pulmonary veins transport oxygenated blood into the hearts left atrium. Every organ consists of an aterial and venous which provides organ tissues with blood and also drains the blood away. Capillaries are what provide the cells with organ tissues. The systemic circulation involves all the blood vessels that do not take part in the pulmonary circulation.
Structure and function of blood:
Blood is a connective tissue. It’s what carries information through the cells to various parts of the body and external environment. Transportation of substances is the main function of the blood. The blood is used to transport:
- Oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs
- Nutrients to the tissues and cell wastes to organs such as the kidneys so that they can be excreted
- Hormones to the required body organs
- Heat that is formed in active tissues is transported through the blood to less active tissues.
- Antibodies to areas of the body that are infected
The blood is made up of a clear fluid called plasma. The blood is made up of about 55% of plasma fluid and about 45% of blood volume. The plasma is made up of water and substances such as plasma proteins, inorganic salts, nutrients, waste substances, hormones and gases.
Plasma, red blood cells and white blood such as lymphocyte, neutrophil and eosinophil are all part of the blood.
Ethrocytes consist of haemoglobin, which is an essential in order for human survival. Haemoglobin is a protein that contains iron and is important as it forms strong chemical bonds when combined with oxygen when in an environment that has a high concentration of oxygen. The chemical bond that is formed is called oxyhaemoglobin. Oxy haemoglobin is produced within the blood inside lung capillaries and it delivers oxygen to the tissue cells. However when haemoglobin is in an environment where oxygen concentration levels are low, the oxygen is given body cells. At this point haemoglobin has reduced.
Respiratory system
The respiratory system supply’s the blood with oxygen in order for the blood to deliver oxygen to all parts of the body which is done through breathing. When we breathe, we inhale oxygen and exhale carbon dioxide. Respiration is achieved through the mouth, nose, trachea, lungs, and diaphragm, many smaller tubes which connect to tiny sacs called alveoli.
The role of air passages in the nose:
The structure of the nose consists of curled fine bones on the side walls which contain moist ciliated mucous membrane which is filled with blood capillaries. This structure forms a large surface area which is where air enters the body. As the air travels through the nose it is warmed and moistened due to the fact that it comes to contact with the mucous membrane and that ciliated cell are what filters it. Once the air reaches the throat its temperature is almost at the body temperature and it still remains moist. Once the air reaches the throat dust, carbon particles and various other pathogens have been removed.
Structure and function of the trachea, bronchi, lungs- bronchial tree and alveoli:
The trachea starts from the back of the pharynx and then splits into two major bronchi which are each attached to one lung on each side. The earliest section of the trachea is called the larynx which is also known as the voice box. This is the section where sound is formed. This part of the trachea consists of a epiglottis , which is what protects it by not allowing food to enter it during time of food consumption. If food does enter this part then the body tends to react by coughing in order to remove it from the area.
In order to ensure that the trachea and the bronchi do not fall apart, they have rings of cartilage in order to prevent this from occurring. Cartilage that is found in the trachea is C shaped and contains a hole behind it and is closed to the oesophagus ( the food tube) . The reason why this is because when food is chewed it is made into a ball known as bolus before it is swallowed. As the bolus travels down to the stomach it causes the oesophagus to increase in length (stretch) and the rings of cartilage that are in the trachea help this process. The gap that was mentioned before is then covered with soft muscle which stretches and allows food to go through the oesophagus.
At the lungs entrance every bronchus consistently divides and sub divides and then goes into each section of the lung. The very smallest sub-division are called the bronchioles, these provide the air sacs that are found in the lungs with oxygen. This division that are always branching are called the bronchial tree.
Ciliated columnar epithelium cells and mucous are what form the lining of the trachea and the bronchi. Overall the Trachea is the name given for the tube which carries air from the mouth. This tube is then separated into two and it becomes the Bronchi which is what equally divides the air into each lung. When the air enters the lungs it passes through a structure which has an extensive number of blood vessels. Carbon dioxide is taken to the lungs to be removed and oxygen is taken from the lungs to the body by these blood vessels. The Bronchi has a very sensitive lining and is wrapped in a layer of mucus which helps to protect the sensitive structure of the lungs and moisten the air. The Bronchi helps prevent dust and bacteria from getting into the lungs.
The lungs are of a pale pink colour which has a similar shape to the core part of the chest. Each lung consists of small amount of lobes which have a root that is linked to the bronchus, blood vessels and nerves. The outside of the lungs are outlined by the pleura. According to Stretch and whitehouse (2007) ‘ The pleura continues around the inner thoracic cavity so that the twp pleural layers slide over one another with ease and without friction.’ The surface tension found on the thin film of moisture prevents the two pleural layers from ripping apart, instead it only lets them slide away. This signifies that when as the chest wall moves during breathing so does the lungs.
After constantly dividing and sub-dividing into a group of one layered circular structures, what was originally the bronchus becomes the alveoli. The walls of the alveoli contain narrow and yet flat squamous epithelium and the capillaries are what circle each alveolus. During breathing the air that goes into the alveoli is received from the blood by only two narrow and yet single layered walls. Elastic fibres can be found close to the alveoli which are what helps with inspiration and expiration. The inner side of the alveolus is lined by a film of moisture which allows air gases to ravel through into solution. These gases tend to travel past rather quickly due to the fact that the layers of epithelium are very narrow and semi permeable. This transportation of gases is called gaseous exchange. Ciliated cells are situated in the large bronchioles within the respiratory and genitourinary tracts.
Ciliated epithelial tissues consist of plasma membranes which are formed from microtubles which are able of beating rhythmically in order to transmit mucus and other substances through the duct. These types of tissues are mostly found in the respiratory system and on the lining of the oviduct.
Respiratory muscles – intercostal muscles, diaphragm and ventilation:
The respiratory process is linked with the muscles in the ribcage. These muscles are called intercostals muscles which are found between the ribs. Another muscle that is used in the respiratory process is the diaphragm. These muscles interrelate with each other. When a person breathes in the intercostals muscles lift the ribs both forward and up, as for the diaphragm it moves downwards. When a person breathes out both the intercostals muscles and the diaphragm are relaxed.
The movement that occurs in the thorax when air travels enters and leaves it is called ventilation. Ventilation involves receiving oxygen and getting rid of waste products. Ventilation is made up of two parts which is inspiration and expiration. Respiratory muscles have a role in the process of ventilation. There are two types of intercostal muscles which are located between the ribs. The diaphragm is linked to the lower ribs and is what splits the thorax from the abdomen.
- Inspiration: Inspiration is the inhalation of air. As intercostal muscles contract, the ribs move upwards and outwards, the fact that the diaphragm contracts causes it to flatten. All these contractions cause an increase in the volume of the thorax and the lungs causing the pressure inside the lungs to reduce allowing air from the environment to enter.
- Expiration: When breathing during periods of rest the main pressure that occurs during expiration is the elastic recoil of the fibres which surround the alveoli, at this point the diaphragm is relaxed. Although this is the case, when exertion occurs more forcible expiration also occurs as the intercostal muscles contract causing the ribs to move downwards and inwards. According to stretch and whitehouse (2007) ‘ the volume of the thorax decreases, the pressure increases above that of the environmental air and air rushes out.’
Gaseous exchange:
In the air that we inhale twenty per cent of it is oxygen and the other eighty per cent is nitrogen. Carbon dioxide is not in haled. In the air that we expire there is sixteen per cent of oxygen and eight per cent nitrogen and also four per cent carbon dioxide. Nitrogen seems to have the highest percentage however it does not have a role in respiration. Inhalation of air refills the lung alveoli with a high concentration of dissolved oxygen molecules. Transportation of diffused oxygen by the blood stream ensures that concentration remains low. In regards to carbon dioxide, the blood consists of high concentration and low concentration is found within the air. A process called diffusion gets rid from the blood. Internal respiration in cells gets rid of waste products like carbon dioxide and water.
Diffusion:
The molecules that are found in liquids and gases constantly move in random motion. The process of diffusion occurs in liquids and in gases. Diffusion involves a large range of molecules combining with a small range of molecules. As the number of molecules increase, diffusion eventually stops, this is called the equilibrium. Diffusion plays a major role in the human body as it is used for transportation. Diffusion transports molecules of a gas or a liquid from an area of high concentration to an area where concentration is low. Diffusion only takes place when barriers between all molecules are narrow.
Digestive system
The alimentary canal:
Within the human body there is a tube that goes from the mouth to the anus, this tube is called the alimentary canal. The alimentary canal passes through other areas such as the stomach, liver, pancreas, duodenum, ileum and colon.
The oesophagus:
The oesophagus takes food that has just been consumed from the mouth into the stomach. Food travels down the oesophagus through muscular contractions called peristalsis.
Stomach:
The largest part of the alimentary canal is the stomach. In the human body the stomach is found behind the rib cage and located under the diaphragm towards the left side. The stomach is supplied food from the oesophagus. The stomach can store food for up to three hours, protein rich food tends to stay in the stomach for the longest period of time. Whilst food is in the stomach, its walls roll the food and pour gastric gland secretions. This forms a material called chyme.
Gastric glands form gastric juice which consists gastric protease and hydrochloric acid. Gastric juices are used on proteins. Rennin is an enzymes that in the body of babies it digests and solidifies milk proteins. The stomachs pH is very acidic. It has a ph between one and two. The stomach consists of an epithelial lining which has goblet cells that form thick mucus which is what prevents the lining suffering from acid erosion.
Through the pyloric sphincter, the stomach release chyme into the duodenum.
The duodenum:
The small intestine consists of two parts the duodenum, is the first part. The duodenum is the part in the alimentary canal that comes after the stomach. The duodenum has a role in digestion, it works with the liver and the pancreas in order to do this. The lover and the pancreas secrete juices to the duodenum. The wall in the duodenum has glands that release juices which contain enzymes. These juices have a role in the digestion of proteins, fats, lipids and carbohydrates.
The ileum:
The second part of the small intestine is called the ileum. The ileum plays a role in the absorption of food. Once the food has reached this stage it has now become fully digested. Them ileum has special features to allow it to absorb food. It has a folded interior, is long in length, its lining is filled with villi which is covered with microvilli. These special features highly increase the surface area for nutrient absorption.
Villus has a lining of columnar and goblet cells and they also have an internal extensive capillary network. Proteins and carbohydrates travel through the capillary network which is emptied in the liver through the hepatic portal vein. Fats travel into the lacteal and then with time it goes through the lymphatic system into regular circulation.
The colon:
On the right side of the abdomen, the small and large intestine join together and combine. Biological remnants called caecum and the appendix are present. In the human body the caecum and the appendix have no role they happen to just be there. If the appendix inflames or ruptures then this can be extremely dangerous and will need to be removed. The caecum and the appendix are not the only two parts that are found in the large intestine the colon and the rectum are also found there. The anus is also present, this is where faeces are released. The colon is located on the right side of the abdomen, it travels from the right side and then changes direction and then passes through the left side and finishes when it reaches the anus. Enzyme juices are not found within the large intestine.
According to stretch and whitehouse (2007) ‘ The colon has a puckered appearance because the outer longitudinal muscle coat splits into three bands and the circular muscle bulges out and between the bands.’
As the transport down the alimentary gland occurs, various glands have secreted water-type juices onto the chyme. The large intestine has a role in slowing down the transport of food waste, as the body cannot lose a certain amount of water. In the colon all that is left is food waste as the small intestine absorbed the nutrients that it needed. At this stage water can be absorbed again and at this point faeces tend to become half solid. Faeces leave the body through muscular activity of the rectum and through anus relaxation.
The liver:
The liver is located in the upper part of the abdomen and on the right side. The liver slightly overlaps the stomach. The liver has various functions within the human body, one being the formation of bile. Bile travels into the duodenum through the bile duct after have been in the gall bladder, which is found on the liver. No enzymes are found in bile however it contains vital bile salts which lead to the emulsification of fats in the duodenum. Due to emulsification fats produce many small globules, which contain a water/lipid surface in order to ensure that can function effectively. Bilirubin and biliverdin are bile pigments that are found in bile. These pigments are unwanted (waste) material released from degraded haemoglobin which originally came from old and broken red blood cells. The brown colour that is on faeces comes from these pigments. Bile is constantly being released from the liver and for a short period it is stored in the gall bladder. When food that is rich in lipids is consumed, bile is released by the gall bladder into the small intestine.
Another function of the liver is that it takes glucose and other sugars from the blood that it has received from the small intestine and turns these into glycogen, which is then stored.
The pancreas:
The pancreas is situated near the duodenum and it is found between the intestines and the stomach. The pancreas releases pancreatic juices which are filled with enzymes and also alkaline salts which help neutralise the stomachs acidic secretions. These juices interrelate with nutrients such as protein, fat and carbohydrates and are responsible for breaking down complex food molecules and turning them into amino acids, glucose and similar simple sugars and also fatty acids and glycerol.
Salivary glands:
There are three types of salivary glands which release saliva into the mouth. Saliva contains salivary amylase, this is what starts the carbohydrates being digested. It also helps keep the mouth wet and in the production of the food bolus.
Role of the digestive system in breakdown and absorption of food materials (ingestion, absorption and egestion):
Ingestion is the name given for the consumption of food. Food is made from large complex molecules which consist of protein, carbohydrate and fat that cannot travel through the alimentary canal. The transformation of these complex molecules into simple soluble molecules allows absorption to take place in the bloodstream and allows metabolic processes to occur. Substances that have not been absorbed are known as waste material and these leave the body through the anus, this is egestion.
Peristalsis:
Peristalsis is the process where food and chyme travel through the alimentary canal. According to stretch and whitehouse (2007) ‘behind the bolus or chyme the inner circular muscle contracts (and the longitudinal muscle relaxes) pushing material in front of it.’ At the front of the material the circular muscle is what relaxes and the longitudinal muscles is what contracts and it is what opens in order to receive food.
Bibliography.
- Marieb,E (2000) Essential of human anatomy and physiology, Addison Wesley Longman inc
- Strectch, B and White house, M (2007) BTEC National Health and social care book 1, Heinemann
- http://biology.about.com/od/anatomy/a/aa060404a.htm
