Friday, 25 November 2011

2.63a Heart Structure

Describe the structure of the heart and how it functions.

The heart
If blood is going into the heart. The blood vessel is called the vein.
If the blood is comming out of the heart, the vessel is called an artery.
The technical term of the lung is pulmonary and the pulmonary artery takes blood from the heart to the lungs. The pulmonary vein takes blood from the lung to the heart.
The major artery in the body is the aorta. The major vein in the body is called the vena cava.
The heart has two small chambers which is the left and right atrium and two large chambers which is the left ventricle and the right ventricle.  The left side of the heart and the right side of the heart is seperated by a wall called the septum. The aorta takes blood to the body, pulmonary artery takes blood to the lung, and blood returning from the lung from the pulmonary vein and blood returning to the heart through the vena cava.  The valve on the left side of the heart is called the bicuspid valve and valve on the right side of the heart is called the tricuspid valve. The semi lunar valves are located near the end in the right atrium.

Valve Function
When the pressure is high, the blood forces down through the cuspds of the valve open and the blood flows through to a region to a region with low pressure which is the general rule for the valves and blood flow. On the other side of the same valve, if the high pressure area was lower than the low pressure area, such as when the ventricle contracts (the bicuspid/tricuspid valve) high pressure will get behind the cuspds and cause it to close which makes the heart sound - 'Lup' or 'Lub'. This is the first heart sound. The semi lunar valves also works the same way. When the pressure is high in the ventricle, it forces blood through to the artery, but when the heart relaxes blood flows backwards, closing the semi lunar valves making the second heart soun - 'dup'. Which makes the heart sound 'lup' (closure of the atrio ventricular valve) 'dup' (closure of the semi lunar valve) and this is the sound when you hear your heart beating.

2.62 Clottting

Recall that platelets are involved in blood clotting, which prevents blood loss and the entry of microorganism.

Platelets are produced in the bone marrow which are just fragments of cells.
When we have wounds on our body, the exposure of the platelet to the air is that the platelets releases chemicals. In the blood there is a protein called fibrinogen which is soluble and with the chemical from the platelets, this turns into fibre which is solid. What happens is there will be a matrix/network of fibre molecules on the wound and onto this, solidifies the red blood cells and forms a scab. Beneath which, the cells will will be repairing the wounds and stops blood loss. White blood cell will attack any pathogens entering to wound.

Tuesday, 22 November 2011

2.61 Vaccination

Understand that vaccination results in the manufacture of memory cells, which enables future anti-body production to the pathogen to occur sooner, faster and in greater quantity.

In Vaccination, a type of pathogen is introduced into the blood stream (either dead or weakened). The biological word for weakened in attenuated and these pathogens cannot cause diseases. The fragments of the bacteria are introduced to the lymphocytes which produces plasma cells and memory cells. The reason why we vaccinate is because if this happens naturally, it will take time and during this time the organism may be killed or be very severely damaged. If we introduce cells which are attenuated they won't do any harm to the body and still help with the production of memory cells. So if the person actually catches the pathogen which are strong and harmful  the pathogen would be quickly picked up and be eliminated before it harms our body.

2.60b Lymphocytes

Describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen.

Unlike Phagocytes, Lymphocytes has a large nucleus.
  • Each type of bacteria has a particular Lymphocyte that can detect it.
  • This is a specific indentification by Lymphocyte of the bacteria. If there was a different bacteria it would require a different Lymphocyte.
  • When they come together, the cell divides to form two different clones and these are called memory cells. The other clones (the Plasma cells) which are produced are the ones that are going to produce the anti-bodies. All genetically identical to the first one.

  • The Plasma cells secrete protein molecules into the bloodstream which are called anti-bodies. One possible action for an anti-body is that it will attach to bacterial cell and act as a label that will attract phagocytes. Second mechanism is that the anti-body attaches and causes bacterial lysis and kills the bacteria. The third more of action, is causing many bacterias to stick together and this is called Aggrototination. This means that the Phagocytes can then engulf the bacterias

  • If after the infection, we meet the same type of bacterial cell The chances of it meeting the memory cell is greater than meeting the original cell and so the consequence of this is is that it reacts faster and more anti-bodies. This is called the seconday response which means the Plasma Cells are the primary response.

2.60a Phagocytosis

Describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen.

The process starts with a white blood cell and you can recognise white blood cells through the lobuded nuclues.
  • Phacytosis is the first line of defense of our body, it defends us against bacterias in our blood stream. The white cell can detect the presence of the bacteria because of the chemical the bacteria gives off.
  • The consequence is that the Phagocyte (white blood cell), the chemical stimulus starts the cell to surround the bacteria cells.  The extention is called the Pseudopodia. If we move on to the next stage, the bacteria is closed by the cell membrane of the Phagocyte - this is called the fuse stage.
  • This leads to the next stage which is bacteria enclosed which is called the vescicle. The next step is that the white cell will introduce enzymes which will destroy the bacterial cell. What often happens is that the white cell is excrete and release the fragment of the dead bacteria.




2.57 Composition of Blood

Recall the composition of blood: red blood cells, white blood cells, platelets and plasma.

  • In the blood 45% are cells and 55% are the plasmas.
  • Of the cells the types we have are red blood cells, known as Erythrocytes and the White Blood Cells and in the White blood cells we have phagocytes and Lymphocytes.
  • A plasma is largely composed of water.
  • Also in blood there are fragments of the dead red blood cells known as platelets. These play important role in clotting.

Thursday, 17 November 2011

2.59 Red Blood Cells

Describe the adaptations of red blood cells for the transport of oxygen including shape, structure and the presence of haemaglobin.

If we had a cubic millimeter of blood, there would be 5x10^6 red blood cells, which is 5 million red blood cells per cubic millimeter of blood. Which means 5 trillion cells in a 5 litre circulatory system.

  • The shape is described as a Bioconcave disc. This shape gives you short diffusion distance for oxygen so we get fast diffusion.
  • There is no nucleus in the red blood cell, which means more space for haemaglobin and no mitochondria means that the red blood cells will not use up the oxygen it is transporting.
  • The presence of haemaglobin - haemaglobin is able to carry oxygen and there are millions of haemaglobin molecules (5x10^6) per cell. Each one carrying 4 oxygen molecules.

2.58 Role of Plasma

Understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy.


  • As previously noted, blood is 55% composed of plasma and 45% cells. Plasma is mainly composed of water and the water properties that makes it import is that it is a solvent and a fluid
  • The transportation of carbon dioxide is carried in the plasma dissolved in a form of hydrogen carbonate ions  and some carbon dioxide directly. 
  • Digested food takes the form of soluble sugars and amino acids, which can be transported to the cells through the plasma.
  • Waste molecules such as Urea involved in excretion, are also transported from the liver to the kidney dissolved in the plasma of blood. 
  • In communication terms, blood carries signals from the body through hormones such as ADH, Insulin and Glucagon.
  • Another good property of water is that it is very good at carrying heat so becomes important in maintaining body temperature.

Thursday, 3 November 2011

2.75 Urine

Recall that urine contains water, urea and salts.
  • Urine contains salts, water and urea.
  • Water and salt particularly affects the composition of the tissue fluid which is called osmoregulation.
  • The removal of the urea is part of the excretion of metabolic waste.
  • The salt, water and urea composition in each person varies depending on the condition the person is in.

2.74 ADH

Describe the role of ADH (antidiuretic  hormone) in regulating the water content of the blood.
  • Anti-diuretic hormone is produced in a region of the brain known as the hypothalamus. Like all hormones it flows through the blood stream and the target is the kidney.
  • The effect of ADH is to control and alter the composition of water which is in blood.
  • ADH has the ability to make blood more or less concentrated to keep the tissue fluid isotonic.
  • This is the role of ADH.
  • ADH targets the collecting duct and the effect of ADH is that it allows more water to come out of the collecting duct
  • We know that water selective reabsorption happens in the collecting duct but ADH can increase the amount of water going into the blood.
  • ADH makes the collecting duct walls more porous so that more water can escape from the collecting duct and this water goes back to the blood. 
  • The consequence of ADH secretion is that the urine would be more concentrated and have a lower volume.

2.73 Glucose Reabsorption

Understand that selective reabsorption of glucose occurs at the proximal convoluted tubule.

Selective reabsorption means that it is selected and the reabsorption refers to idea that the glomerulus filtrate will go back to the blood.
  • Filtration happens in the bowman's capsule and the glumerulus filtrate will contain the molecule glucose (and many others e.g. water, salts, amino acids and urea).
  • At the end of the nephron is urine and normally urine does not contain glucose.
  • If you test and find glucose in your urine it is a condition known as diabetes.
  • In the first (proximal) convoluted tubule glucose is removed and taken back to blood.

2.72 Water re-absorption

Understand that water is reabsorbed into the flood from collecting duct

From the previous syllabus statement we learned that Ultrafiltration happens in the bowman's capsule.
  • High pressure blood is forced into the bowman's capsule and the dissolved contents of the blood are forced into the glumerula filtrate and this tube contains glucose, water, salts and urea.
  • When the filtration occurs it will filter out too much water and as the filtrate passes along the tubule here. When it reaches the Collecting duct as the filtrate pass through the collecting duct what happens is that water is removed from the filtrate.
  • The water is then returned to the blood vessel and will go back to the blood stream.
  • Selected reabsorption occurs in the collecting duct.

2.71 Ultrafiltration

Describe ultrafiltration in the Bowman's capsule and the composition of the glomerular filtrate.

In this diagram, we have the same one from 2.70.
  • Nephron's function is to filter blood and ultimately in two things - filtered blood and the waste (urine)
  • The urine is going to emerge at the bottom of the tube and this urine is composed of largely water, salts and also the molecule known as urea (nitrogen waste). The urine goes out into the pelvic region.
  • The first process starts at the bowman's capsule, and the process is called ultrafiltration - the filtration of molecules.
  • The filtration of blood begins with blood comming in through the afferent arteriole and this blood is in high pressure. It is then twisted and branched and becomes much, much smaller (glomerulus) and comes out through the blood vessel efferent arteriole which the diameter of this vessel is smaller than the afferent arteriole.
  • The high pressure forces the liquid (plasma) and plasma contains all the substance contained in blood for example water, salts, amino acids, glucose and urea. These are all forced out from the blood into the space, the inside of the bowman's capsule.
  • When the plasma is forced into bowman's capsule, we call this filtrate and because it is in the glomerulus we call this glomerula filtrate.
  • The blood has been filtered due to high pressure because of the smaller area of the blood vessel.

2.70 Nephron Structure

Describe the structure of a nephron, to cinclude Bowman's capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct.

  • Nephron is the functional unit of the kidney. The part that does the filtration and of the composition of blood.
  • The aorta brings blood and through the renal artery reaches the kidney and waste (urine) then goes through the ureter to the bladder.
  • The filtered blood exits the renal vein and return to the vena cava. If we slice through the kidney we see different colored region, the lighter colored region is called the cotex and the inner, slightly colored region is called the medulla and the lighter colored space is the pelvic region.
  •  In this space it is where the urine collects and drains down the ureter.
  •  The region of the different color is because the kidney is made up of millions of tubes.
  •  The tube starts on the edge of the medulla and moves directly upwards through the medulla and up through the cortex and then will reach a dead-end and is called the bowman's capsule.

If we look at this is more detail we will be looking at the nephron.
  • The tubular structure is called the nephron.
  • Above the dotted line is the cortex and below the dotted line is the medulla.
  • At the end of this tube it will be the pelvic region and its at this place where the urine emerges.
  • The twisted part is called the convoluted tubules and the end tube is called the collecting duct.
  • The dip in the middle is called the loop of henle.
  • The dead end is called the bowman's capsule. The tight knot of blood vessel is called the glomerulus.
  • The first twisted section is called the proximal convoluted tubule (PCT).
  • The second twisted section is called the distal convoluted tubule (DCT).
  • It's the arrangement which gives the different colored region of the kidney. There are millions of nephrons in a kidney.