LEVEL 3 DIPLOMA IN AROMATHERAPY MODULE 18 KNOWLEDGE OF ANATOMY, PHYSIOLOGY & PATHOLOGY FOR COMPLEMENTARY THERAPIES THE URINARY SYSTEM COURSE MANUAL CHRISTINA LYNE christina@aromalyne.com
THE URINARY SYSTEM This system is the human body s waste disposal and filtration unit. Every hour the kidneys remove up to seven litres of liquid from blood. This liquid is filtered, and any useful substances are reabsorbed and returned to the blood. The remaining liquid is flushed out of the body removing potentially harmful waste substances that the cells need to dispose of. The functions of the Urinary System: 1. Distribution of intracellular and extracellular fluid. 2. Balance fluid intake with fluid output. 3. General electrolyte composition and balance. 4. Maintain ph values of the body s fluid systems. 5. Regulate blood pressure. The urinary system is made up of the following structures: 2 kidneys - manufacture and secrete urine 2 ureters - conveys urine from kidneys to bladder 1 bladder - stores urine 1 urethra - discharges urine
LOCATION OF THE KIDNEYS Aromalyne Training The kidneys lie on the posterior wall of the abdomen, above the pelvic bone, and on either side of the spine. The right kidney is situated slightly lower than the left because of the room that the liver requires on that side. Each kidney is approx. 11 cms long and is encapsulated in fat. MAIN FUNCTIONS OF THE KIDNEYS The kidneys do the major work of the urinary system. Regulation of blood cell production: they produce and secrete erythropoietin, the hormone that stimulates formation of red blood cells. Regulation of blood pressure: produces and secretes renin, an enzyme that helps control blood pressure and adjusts blood flow into and out of the kidneys. Excretion of wastes and foreign substances: enables excretion of waste products - substances that are no longer useful in the body. Regulation of blood volume: adjusting the volume of blood in the body by conserving or eliminating water. Vitamin D synthesis: the skin and the liver and the kidneys synthesise calcitriol, the active form of vitamin D. Regulation of blood ph: the kidneys help to maintain the normal blood ph. Regulation of glucose production: in an emergency the kidneys carry out a process called gluconeogenesis. This means that they can synthesise new glucose molecules if needed.
THE KIDNEY Aromalyne Training STRUCTURE OF THE KIDNEY Each kidney is enclosed in a fibrous renal capsule helping it to maintain its shape and to protect it against damage / trauma. This inner, deep layer is composed of a smooth, transparent fibrous membrane. The adipose capsule, consisting of a mass of fatty tissue, surrounds the renal capsule and serves as a protective cushion and holds the kidneys firmly in place. The renal fascia secures the kidneys to their surrounding structures and fixes them to the posterior abdominal wall. This fascia is made of a superficial layer of dense irregular connective tissue. The hilium or renal hilus is a deep fissure found on the concave medial border and this is where the ureter leaves the kidney. It is also where the blood and lymphatic vessels and nerves enter and exit the kidneys. The renal cortex - this is the outer part of the kidney consisting of a reddish-brown layer of tissue. The renal medulla - this is the innermost layer. Within the renal medulla are triangular structures called the renal pyramids. The renal pelvis urine passes from the kidney through a renal papilla at the apex of a pyramid into a minor calyx and then into a major calyx before passing through the renal pelvis. The ureter then carries the urine to the bladder.
MICROSCOPIC STRUCTURE OF THE KIDNEY NEPHRONS The functional unit of the kidney is the nephron. This is where filtering takes place. Nephrons Nephrons are largely responsible for removing the wastes from blood and regulating its fluid content. Each nephron consists of two portions: A renal corpuscle where blood plasma is filtered A renal tubule into which the filtered fluid passes The renal corpuscles of the nephron lie in the renal cortex. Each renal corpuscle has two parts: the glomerulus (capillary network) and the glomerular (Bowman s capsule), a double-walled epithelial cup that surrounds the glomerulus. Inside a glomerulus, high blood pressure forces fluid out through its capillary walls, and into the space inside the Bowman s capsule. This liquid is called glomerular filtrate. The walls of the glomerulus act like a filter and about seven litres of glomerular filtrate is produced every hour. The filtrate contains useful substances such as large amounts of water, glucose, vitamins, amino acids and mineral salts. The space in between the two walls is called the capsular space. The walls form a filtration membrane that permits the passage of water and solutes from the blood into the capsular space. From the renal corpuscle, the glomerular filtrate passes into the renal tubule. This tubule makes up the largest part of the nephron. It is made up of three sections. The first part is called the proximal convoluted tubule. Water and solutes pass
through this coiled tubule into the loop of Henle and from there into the distal convoluted tubule. The distal convoluted tubules of several nephrons empty into a single collecting duct. Collecting ducts then unite and converge until eventually, deep in the renal pyramid, there are only several hundred large papillary ducts, which drain into the minor calyces at the renal papilla. The collecting ducts and papillary ducts extend from the renal cortex through the renal medulla to the renal pelvis. URETER TUBES The function of the ureter tube is to carry urine to the bladder. The two ureters have muscular walls, and move the urine by peristalsis. Peristaltic waves occur every 10 seconds sending little spurts of urine into the bladder. The wall of the ureter is made up of three layers: The inner layer is a mucous membrane of transitional epithelium. Mucous prevents and protects the cells from coming into contact with urine. Transitional epithelium allows the walls of the ureters to stretch. The middle layer consists of smooth muscle fibres. Peristaltic contractions of this muscle help to transport urine. The outer layer consists of areolar connective tissue containing blood vessels, lymphatic vessels and nerves that supply the ureters. BLADDER The bladder is an elastic bag at the base of the abdomen. It acts as a reservoir for urine. It continually receives urine from the two ureters that force it downwards into the sac via wavelike contractions. As it gradually fills with urine, it becomes more oval-shaped and once full it rises into the abdominal cavity. When 200-300mls of urine have accumulated, autonomic nerve fibres in the bladder wall which are sensitive to stretch are stimulated. Sensory nerve impulses are sent to the brain which results in the desire to pass water. This process is known as micturition. The mucous membrane of the urinary bladder contains transitional epithelium that allows it to stretch. Folds in the mucosa (rugae) are also present. The muscular layer of the bladder wall consists of three layers of smooth muscle called detrusor muscle. THE URETHRA Urine leaves the bladder through a tube called the urethra where it is then expelled from the body. Normally, the urethra is closed off by two circles of muscles, or sphincters. During urination, the internal sphincter dilates and the external sphincter relaxes. The muscular walls of the bladder and the abdominal cavity contract, while
the diaphragm lowers. These actions expel the urine out of the body. This process is known as urination. In women the urethra is about 4-5cm long and in men it is about 20cm long. THE FILTRATION PROCESS There are three stages in the formation of urine: 1. Simple filtration - blood enters the kidneys through the renal artery and flows at high pressure through the network of capillaries to produce glomerular filtrate. 2. Selective reabsorption - selective filtration then occurs. Essential nutrients contained within the filtrate such as glucose, sodium ions, amino acids, potassium, vitamin C and most of the water is reabsorbed here by active transport mechanisms back into the bloodstream. 3. Tubular secretion - a small amount of remaining water and waste products are passed to the collecting ducts to become urine. The urine then flows to a funnel-shaped receptacle called the renal pelvis. From here it flows into the ureter. COMPOSITION OF URINE The composition of urine varies widely, depending on the amount of waste substances to be excreted. The main substances in urine are: Water (96%) - when there is less water to be excreted, the urine is stronger. Urea (2%) - this is a waste product of amino-acid breakdown. The remaining 2% is made up of uric acid, creatinine, sodium, potassium, chlorides, sulphates, phosphates, ammonia, urobilinogen and oxalates. Waste products Creatinine and uric acid are waste products that are excreted by the kidneys. Creatinine is a product of muscle activity. Uric Acid is a product of nucleic acid metabolism. Urobilinogen is bile pigment derived from the breakdown of haemoglobin. Urea is a toxic waste product that is produced as a result of the liver being unable to store excess proteins. The extra proteins are broken down by the liver and become urea. This is why some people who have problems with their kidneys e.g. glomerulonephritis, are sometimes put on a low protein diet to reduce the kidneys load. Alcohol, steroids, certain medicines and drugs appear in urine if they are being taken.
Colour - Normal, healthy urine is a clear, pale yellow fluid. The amber/yellow colour is due to the presence of the pigment urobilin. Urine may become pink after eating beetroot or red sweets, or after taking certain medicines. Jaundice and other disorders of the liver can result in the excretion of bile pigments in the urine, making it a dark yellow or orange colour. Smell - Fresh urine normally has very little smell. When it becomes contaminated with bacteria, the urea in the urine is converted to ammonia, which gives a strong smell. Cystitis may cause the urine to have a strong, unpleasant smell. ph the normal ph of urine varies from 4.5-8 depending on diet. A high animal protein diet will produce a more acidic urine, whilst a vegetarian diet tends to produce a more alkaline urine. A healthy adult passes 1000 ml to 1500 ml per day. Urine production is decreased during sleep and exercise. THE IMPORTANCE OF OSMOSIS IN THE URINARY PROCESS Osmosis plays an important part in regulating the distribution of water and other substances between cells and blood. This process keeps water moving in and out of the body compartments. The body s fluids need to stay at the right level so that the cells do not shrink or swell up. Osmosis is a form of diffusion that takes place when two solutions of differing strengths or concentrations are separated by a differentially permeable membrane. This kind of membrane is widespread in the body - they surround all cells. They are selective, stopping large dissolved molecules (like proteins) passing through their walls, but allowing the passage of other substances such as water, salts, amino acids and simple sugars (such as glucose). To give an example on a cellular level; if there is too much water inside a cell and not enough outside, then the cell will expel water into the surrounding tissue fluid. Similarly, it works the other way; if there is not enough water inside a cell, the cell wall (or membrane) will draw water from the surrounding tissue fluid into the cell. The water molecules move through the cell membrane until the solutions either side of the cell are of equal strength. The pressure needed to stop all such movement is called osmotic pressure. THE RELATIONSHIP BETWEEN WATER BALANCE AND URINE OUTPUT The body gets most of its water from the food we eat and fluids that we drink. We lose water in several ways - the kidneys excrete urine, the lungs exhale water vapour, the skin evaporates water when we sweat and we excrete faeces. Women of reproductive age also lose body water through the menstrual flow. Different parts of the body must contain the right amount of water - it is important that the volume of fluid in each compartment remains at a constant. This is called fluid balance and is controlled by the kidneys.
The minimum urinary output is about 50mls per day. If it rises above this, it is then controlled mainly by anti diuretic hormone (ADH) which is released into the bloodstream by the pituitary gland. Sensory nerve cells in the hypothalamus detect changes in the osmotic pressure of the blood, stimulating the pituitary gland to release ADH. As blood becomes more concentrated, ADH output is increased and as a result, water reabsorption is increased, reducing the blood osmotic pressure and ADH output. In diabetes mellitus, when the blood glucose level is too high, then excess water is excreted with excess glucose. This polyuria may lead to dehydration despite increased production of ADH but is usually accompanied by acute thirst and increased water intake. The daily output of urine varies. Hot weather or a hot room will cause the body to sweat more, thereby reducing the amount of urine expelled. This is because the body has too little water, so the kidneys reabsorb as much as they can from the glomerular filtrate. As a result, only small amounts of concentrated urine are produced. Similarly, cold weather or drinking large amounts of water can increase the amount of urine produced. We sweat less. More urine is produced and it is more dilute. Eating too much salt will raise blood pressure, more urine is produced and thirst will increase. RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM Kidneys respond directly to changes in blood pressure. If blood pressure increases, the kidneys increase their excretion of salt and water, so that blood volume decreases and blood pressure returns to normal. If blood pressure decreases, the kidneys decrease their secretion of salt and water, so that blood volume increases and blood pressure returns to normal. The kidneys can increase blood pressure by secreting the enzyme renin. Renin is a hormone produced by special cells within the kidney. Released by the kidney in response to diminished blood flow, renin acts to raise blood pressure and restore normal blood flow. Renin also activates the blood pressure altering abilities of angiotensin. The renin-angiotensin-aldosterone system is a group of related hormones that act together to regulate blood pressure. It is called a system because each part influences the other parts and all are necessary for the whole to function correctly. Almost all long-term blood pressure adjustments are the responsibility of the kidneys and the renin-angiotensin-aldosterone system.
How does the system work? Aromalyne Training When blood pressure drops for any reason, special cells in the kidney detect the change and release renin into the blood stream. Renin converts the plasma protein angiotensin (produced in the liver) into angiotensin I. A molecule called angiotensin converting enzyme (ACE), formed in small quantities in the lungs, then converts angiotensin I into angiotensin II. Angiotensin II is a powerful hormone and can act directly on blood vessels to cause blood pressure increases. It also stimulates the release of the hormone aldosterone from the adrenal cortex and the antidiuretic hormone (vasopressin) from the pituitary gland. Aldosterone is a very powerful vasoconstrictor. It causes the kidneys to retain both sodium and water, and to excrete potassium. The sodium causes water to be retained, thus increasing blood volume and blood pressure. Why should we be aware of this? Damaged kidneys continuously produce excess renin, therefore this series of reactions happens relentlessly, resulting in blood pressure rising continuously. There is a common link between raised blood pressure and kidney disease. What is the relationship between the Urinary System and the Circulatory System? The circulatory system's function is to deliver oxygen and nutrients to the cells and also deliver waste products to the kidney for excretion. The blood contains both nutrients like glucose, amino acids and metabolic waste products like urea and creatinine. The blood passes through the kidney to be filtered in the glomerulus, then the nutrients are reabsorbed and waste products are left to pass into the collecting duct to form urine for excretion. Also, the circulatory system and the urinary system, along with the respiratory system, share the role of regulating acid base balance of the body. What is the relationship between the Urinary System and the Endocrine System? The main way the endocrine system affects the excretory system is in controlling the amount of water released with urine. The endocrine system releases a series of hormones to cause the kidneys to resorb water from the urine when blood water levels are low. What is the relationship between the Urinary System and the Skeletal System? The kidneys are involved in calcium homestasis. When plasma calcium is low the parathyroid glands signal the kidneys to increase calcium reabsorption, & also trigger the release of calcium from the bones. When plasma calcium is high, the kidneys excrete more calcium. The kidney also produces the hormone erythropoietin, which stimulates the bone marrow to create red blood cells.
What is the relationship between the Urinary System and the Integumentary System? They interact in the regulation of water balance. When you perspire a lot and lose water through the skin, then the kidneys react to conserve water and produce less urine.