P1) Describe the main sites of reabsorption in the kidneyBowman’s Capsule, Glomerulus:The the sac of the Bowman’s capsule is thin which covers the Glomerulus. The glomerulus is composed of clustered together capillaries which carries the blood. The Bowman’s capsule contains 2 layers. The interior layer that covers the Glomerulus while the exterior layer continues to layer the renal tube walls. Its main role of the Bowman’s capsule is to filter out the wastes and other substances such as water and salts. The Glomerulus role is to create urine by filtering down the blood. This is then transported through the Bowman’s capsule and then into the proximal convoluted tubules.http://www.innerbody.com/image_card08/card65-new.html#continuedProximal convoluted tubule:The Proximal convoluted tubule is located between the Bowman’s capsule and the loop of henle. It’s main function is to allow the glucose, water and other substances such as peptides and nutrients to flow back into the bloodstream from the tubule fluid. This happens because the ciliated cells which are present there creates a larger surface area which therefore allows faster and more amounts of nutrients to be absorbed. https://www.merriam-webster.com/dictionary/proximal%20convoluted%20tubulehttps://www.mytutor.co.uk/answers/10629/A-Level/Biology/Describe-and-explain-the-main-function-of-the-proximal-convoluted-tubule-in-filtration-absorptionLoop of HenleThe loop of Henle’s structure is a “U” shape part of the nephron. At first, it is made up of a thin descending limb, followed by a thick descending limb. Then lastly a thin ascending limb. In the thin descending limb, the fluid present is mainly consistent of sodium chloride and urea as well as other chemicals. This will at this stage filter out of the blood. The cells present in the descending limb are very permeable in water therefore the concentration of urea increases in this location. This therefore, causes the water to get reabsorbed into the thin descending limb. In the ascending limb, the cells present are only permeable to the sodium chloride. The sodium chloride present gets absorbed into the tissue of the medulla. The thick ascending limb then reabsorbs the sodium chloride by the sodium potassium cotransporter.https://www.news-medical.net/health/The-Loop-of-Henle.aspxDistal convoluted tubuleThe Distal convoluted tubule is located and founded between the loop of Henle and the collecting tubule. This contains specialised epithelial cells which are cuboidal shaped. This allows a greater surface area to allow more transport of minerals such as calcium, sodium and potassium as well as the regulation of the pH. Collecting ductThe Collecting duct is at the end of the Nephron. The main function is to move the urine to the larger ducts which will connect to the renal calyces. This is where the urine is stored. The urine then later get transported through the renal pelvis, ureter and finally to the urinary bladder where the urine gets released out of the body. This then ends the urinary system. Each of the tubule of the collecting duct connects to the cortex located on the outer layer of the kidney. The tubule walls are lined up with hair like structures called microvilli. These microvillis releases hormones. https://www.britannica.com/science/renal-collecting-tubuleM1) Describe how reabsorption occurs in each of the main sitesTubular reabsorption is when the water and the solutes such as minerals are moved and filtered in and out of your bloodstream. Reabsorption occurs here the 2nd time as the 1st time of reabsorption happens at the digestive tract when eating food. The fluid which is filtered at the beginning (Glomerulus and Bowman’s capsule) is like blood plasma but does not contain proteins and is not like urine at all yet. The absorptions allows the water and solutes to return back to the extracellular fluids and into the circulatory system. The nephrons also lets out substances which are no longer needed in the bloodstream and into the filtrate. Homeostasis allows the body fluid to be in balance because of the specialised design of the nephrons. The amount of minerals and the extracellular fluid are kept in a stable and safe level. Each part of the nephrons are specialised for different roles of reabsorption. The cells of these walls are specialised as the cell shape is cuboidal and epithelial. Some areas contains microvilli. Both these specialities and the length of the tubule makes the absorption rate increase significantly as the surface area increases. This allows more exchange to take place at the same time. Another speciality of the nephrons is that there is many mitochondria present which helps to create energy for allowing active transport to occur effectively. Firstly, the water is moved either actively or passively to the space outside from the tubule and its permeable walls. And next in reabsorption, the water and minerals passes into the walls of the capillary which then travels to the bloodstream.In the body fluid, sodium which is present is positively charged electrolyte. The blood pressure and the amount of blood present can be affected by the amount of sodium present. Sodium when reabsorbed is linked to the passive water movement. The flow of the water is in balance of the osmotic pressure. This makes the body fluid extracellular volume stabilized. Reabsorption in the early proximal tubule:Most of the main important substances in the fluid is reabsorbed at this site. Amino acids, glucose, and other minerals and substances gets transported using sodium cotransporters. This allows the sodium to transport to the tubule cells, and move the electrochemical gradient to be maintained. There should not be a increase of sodium present in the cells, to stabilize this, a sodium or potassium ATPase is used. This makes the 3 ions move away from the area and gets moved into the bloodstream. While this happens, 2 of the potassium ions goes and enters to the site. Other substances such as glucose and amino acids are removed out of the cell and into the blood capillaries. This diffuses and lowers the concentration gradient. This is known as a passive transport. When the filtrate has reaches to the middle part of the proximal tubule, all of the glucose and amino acids will have been absorbed. Reabsorption in late proximal convoluted tubule:There is a decrease of main substances present here. The sodium bicarbonate which had been reabsorbed since it was charged negatively with chloride and sodium ions, this is repressed. There is a high increase of chloride ions since the amount of water had been reabsorbed earlier. The chloride ions will be reabsorbed at this stage by the chloride anion. The Chloride anion exchangers present causes the ions to diffuse through the walls of the epithelial cells and then enters the bloodstream. In between the space of the cells and the tubule, passive movement takes place. This area allows reabsorption of water and sodium chloride. The sodium present will be absorbed by the sodium/proton exchangers. The sodium then actively gets transported by the sodium/potassium ATPase into the bloodstream. Reabsorption at the loop of Henle:The fluid then enters the loop of Henle, where countercurrent multiplication takes place. Both the descending limbs and also the ascending limbs dilutes the fluid here. In the thin descending limb, water is mostly reabsorbed here and the sodium and chloride ions are reabsorbed in the thick ascending limb. In the thick ascending limb, the Na-K-Cl cotransporter as well as the Na-K ATPase helps to keep control of the sodium concentration gradient. Both the potassium and the chloride are absorbed and diffused by the channels in the tubule wall which leads to the bloodstream. This causes the electrochemical gradient to decrease. The sodium present is removed out by the Na-K ATpase into the bloodstream. Since the thick ascending limb cannot reabsorb water, water cannot escape with sodium together. Reabsorption in the distal tubule and the collecting duct:As the fluid travels down the distal tubule and the collecting duct, it flows through the medulla which makes it more concentrated. The water then flows out and the concentration decreases along the gradient. More sodium is then absorbed by different transporters and more Potassium/sodium ATPases. At the collecting duct, the hormones released allows more or less sodium reabsorption if needed to. This causes a hypertonic urine which can be more concentrated.https://www.khanacademy.org/test-prep/mcat/organ-systems/the-renal-system/a/tubular-reabsorption-articleP2) Outline the importance of regulating body fluids in the body.The kidneys are important in the body to help to control and regulate the amount and concentration of fluids. Without the regulation of water, this can affect the mechanisms of the body such as the loss of blood or dehydration.Water is mostly gained by consuming food and drinks into the body. In order for there to be water balance, the amount of water consumed should be equal to the amount of water released out of the body. Although water can be released out by sweat, breathing out, the kidneys is used as a main site for water to be regulated and then released. The kidneys can control the amount of water being released into the urine; depending on the volume of water present, it can save and keep the water if the body needs water or if excess water is present, it gets released into the urine to be released out of the body. This means that the urine would be more diluted compared to the plasma. Vasopressin (or ADH) is a peptide hormone released by the part of the brain called the hypothalamus. ADH allows more channels for water to flow through the epithelial cells in the walls of the collecting ducts. THis means that reabsorption of water happens. Absence of ADH causes less water to be absorbed making dilute urine released out. When the plasma gets very concentrated, receptors in the hypothalamus detect the plasmas osmolarity. This makes ADH released. In the heart, the receptors in the atria are turned on more when larger amounts of blood is present. ADH is inhibited since the body has to let out excess fluids. The carotid and aorta arteries are stimulated when the pressure of the blood is decreased. ADH is released to help regulate the amount of volume present for the cells and tissues. The osmolarity has to be regulated and controlled otherwise the cells present in the body can be damaged such as swelling or shrinking too much which can affect the function of the cell. Since there is a large amount of sodium present in the extracellular fluid, this factor changes and determines the fluids osmolarity. The volume of water and sodium can determine how much volume is needed either make the fluid more dilute or more concentrated in order to regulate the osmolarity. When the body has a lack of water present because of dehydration, the body will try to save as much as water possible while keep the amount of sodium lower to make it more balance. The osmolarity of this is therefore increased. ADH is a peptide hormone released from the hypothalamus which regulates and controls the osmolarity such as by reducing the amount of sodium concentration in the body and try to increase water reabsorption in the kidneys. The part kidney called the distal nephron helps to also regulate the presence of sodium by reabsorbing sodium back. This technique is caused by another hormone called aldosterone. The adrenal cortex uses sensory to detect the osmolarity of the plasma. If the osmolarity concentration is more higher than it is needed to be, the secretion of this hormone is therefore inhibited. This is caused by the decrease of aldosterone making less sodium getting reabsorbed in the distal tubule. ADH is used to save water by make sodium less present. This as a reaction affects the aldosterone to make the osmolarity decrease. When there is low blood pressure detected in the kidneys, responses are indicated to save the volume and to make the pressure of the blood increase again. Renin, which is another peptide hormone indicates this change causes another reaction of making angiotensin II which makes the adrenal cortex make more aldosterone. https://mcb.berkeley.edu/courses/mcb135e/kidneyfluid.htmlD1) Explain how the body maintains the correct acid-base balanceThe body fluids in the body has to be regulated by for example homeostasis or chemical changes. The concentration of the acid or base in the body can change and cause harm to the body if the concentration is too high or low. Acids have a higher concentration of Hydrogen ions while alkaline substances contains a lower amount of Hydrogen ions. The kidney is an example of how they have to stabilize the right amount of pH by absorbing or releasing the acids. Buffer systems helps to allow neutralization to occur to the acid and base. Bicarbonate:The bicarbonate buffer system, is involved to help regulate the pH level of the blood. A buffer is made up of a weak base and a stronger base. The carbonic acid is a weak acid. Carbonate is created when the water had been reacted with carbon dioxide when being catalyzed. Carbon dioxide is present since this compound is a waste product from respiration. H2CO3 is formed by the enzyme carbonic anhydrase. The bicarbonate ions is moved to the carbonic acid which creates equilibrium. Therefore, the acidic blood will become weaker by the process of neutralization with the ions given from the bicarbonate. This reduces the amount of ions present lowering the pH. Ammonia:The use of ammonia is used in the collecting tubules and in the tubular lumen of the kidney. The ammonia (NH3) causes the hydrogen ion to buffer in the collecting tubule cells. Then the ammonia diffuses through the tubular lumen. Ammonia reacts with the hydrogen ion present and secreted which later forms NH4+. When the NH4+ had been released out, more HCO3 is created and then later gets moved to the bloodstream by being created in the tubule cells.Hydrogen phosphate:The phosphate buffer is similar to the carbonate buffer. This contains monohydrogen phosphate ions as the base and dihydrogen phosphate ions which is acid. If the fluid is more acidic than normal, then the fluid will become neutralised by the monohydrogen phosphate ion which is the base.