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Description : This presentation describes complete anatomy and physiology of urinary system consisting of kidney, ureters, urinary bladder and urethra.

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Published on : Jul 07, 2020 | Views : 5394 | Downloads : 32

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URINARY SYSTEM Gladys Kalpana M. Pharm 1
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INTRODUCTION The functions of the urinary system is To eliminate waste from the body To regulate blood volume and blood pressure To regulate levels of body fluids, electrolytes and metabolites To regulate blood pH. To remove waste products and medicines from the body. To release hormones to control blood pressure. To release a hormone to control red blood cell production. To help with bone health by controlling calcium and phosphorus. Gladys Kalpana M. Pharm 2
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Functions – contd… The kidney and urinary systems help the body to get rid of liquid waste called urea. They also help to keep chemicals (such as potassium and sodium) and water in balance. Urea is produced when foods containing protein (such as meat, poultry, and certain vegetables) are broken down in the body. Urea is carried in the blood to the kidneys. This is where it is removed, along with water and other wastes in the form of urine. Gladys Kalpana M. Pharm 3
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Functions – contd… They control blood pressure and produce the hormone erythropoietin. This hormone controls red blood cell production in the bone marrow. The kidneys also control the acid-base balance and conserve fluids. Gladys Kalpana M. Pharm 4
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The urinary system is the main excretory system and consists of the following structures: 2 kidneys, which secrete urine. 2ureters that convey the urine from the kidneys to the urinary bladder. the urinary bladder, which collects and stores urine. the urethra through which urine leaves the body. Gladys Kalpana M. Pharm 5 Anatomy of urinary system
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KIDNEYS Kidneys are bean-shaped organs, about 11 cm long, 6 cm wide, 3 cm thick and weigh 150 g. They are embedded in, and held in position by, a mass of fat. A sheath of fibrous connective tissue, the renal fascia, encloses the kidney and the renal fat. lie on the posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum and below the diaphragm. The right kidney is usually slightly lower than the left, probably because of the considerable space occupied by the liver. Gladys Kalpana M. Pharm 9
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The kidneys produce urine that contains metabolic waste products, including the nitrogenous compounds urea and uric acid, excess ions and some drugs. The main functions of the kidneys are: formation of urine, maintaining water, electrolyte and acid–base balance excretion of waste products production and secretion of erythropoietin, the hormone that stimulates formation of red blood cells production and secretion of renin, an important enzyme in the control of blood pressure. Urine is stored in the bladder and excreted by the process of micturition. Gladys Kalpana M. Pharm 10
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Anatomy of kidney An outer fibrous capsule, surrounding the kidney the cortex, a reddish-brown layer of tissue immediately below the capsule and outside the renal pyramids the medulla, the innermost layer, consisting of pale conical-shaped striations, the renal pyramids. It contains 1–2 million functional units, called as nephrons, and a much smaller number of collecting ducts. The collecting ducts are supported by connective tissue, containing blood vessels, nerves and lymph vessels. Gladys Kalpana M. Pharm 11
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Anatomy of kidney The kidneys are made up by three external layers, which include the renal fascia (the outermost layer), the perirenal fat capsule, and lastly, the innermost layer, the renal capsule, which then surround the space of the renal cortex. There are three major regions of the kidney: Renal cortex Renal medulla Renal pelvis The renal cortex is a space between the medulla and the outer capsule. The renal medulla contains the majority of the length of nephrons, the main functional component of the kidney that filters fluid from blood. The renal pelvis connects the kidney with the circulatory and nervous systems from the rest of the body. Gladys Kalpana M. Pharm 12
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Renal Cortex The kidneys are surrounded by a renal cortex, a layer of tissue that is also covered by renal fascia (connective tissue) and the renal capsule. The renal cortex is granular tissue due to the presence of nephrons—the functional unit of the kidney—that are located deeper within the kidney, within the renal pyramids of the medulla. The cortex provides a space for arterioles and venules from the renal artery and vein, as well as the glomerular capillaries, to perfuse the nephrons of the kidney. Erythropotein, a hormone necessary for the synthesis of new red blood cells, is also produced in the renal cortex. Gladys Kalpana M. Pharm 13
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Renal Medulla The medulla is the inner region of the parenchyma of the kidney. The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are triangle structures that contain a dense network of nephrons. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman’s capsule. It surrounds a tuft of capillaries called the glomerulus that carries blood from the renal arteries into the nephron, where plasma is filtered through the capsule. After entering the capsule, the filtered fluid flows along the proximal convoluted tubule to the loop of Henle and then to the distal convoluted tubule and the collecting ducts, which flow into the ureter. Each of the different components of the nephrons are selectively permeable to different molecules, and enable the complex regulation of water and ion concentrations in the body. Gladys Kalpana M. Pharm 15
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Renal Pelvis The renal pelvis contains the hilium. The hilum is the concave part of the bean-shape where blood vessels and nerves enter and exit the kidney; it is also the point of exit for the ureters—the urine-bearing tubes that exit the kidney and empty into the urinary bladder. The renal pelvis connects the kidney to the rest of the body. Gladys Kalpana M. Pharm 16
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Functions of the kidney Formation of urine Water balance and urine output Electrolyte balance pH balance Gladys Kalpana M. Pharm 18
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Formation of Urine The kidneys form urine, which passes to the bladder for storage prior to excretion. Waste products of protein metabolism are excreted, water and electrolyte levels are controlled and pH (acid–base balance) is maintained by excretion of hydrogen ions. There are three processes involved in the formation of urine: Glomerular filtration selective reabsorption Tubular secretion. Gladys Kalpana M. Pharm 19
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The Nephron The nephron is a tubule closed at one end that joins a collecting duct at the other end. Nephron consists of Bowman's capsule Glomerular filtration apparatus Proximal convoluted tubule Medullary loop (loop of Henle) Distal convoluted tubule, leading into a collecting duct. Gladys Kalpana M. Pharm 20
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Glomerular filtration This takes place through the semipermeable walls of the glomerulus and glomerular capsule. Water and other small molecules readily pass through, although some are reabsorbed later. Blood cells, plasma proteins and other large molecules are too large to filter through and therefore remain in the capillaries. Filtration takes place because there is a difference between the blood pressure in the glomerulus and the pressure of the filtrate in the glomerular capsule. Gladys Kalpana M. Pharm 22
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The volume of filtrate formed by both kidneys each minute is called the glomerular filtration rate (GFR). In a healthy adult the GFR is about 125 mL/min, i.e. 180 litres of filtrate are formed each day by the two kidneys. Autoregulation. Renal blood flow, and therefore glomerular filtration, is protected by a mechanism called autoregulation. renal blood flow is maintained at a constant pressure across a wide range of systolic blood pressures (from around 80–200 mmHg). Gladys Kalpana M. Pharm 24
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Selective Reabsorption Most reabsorption from the filtrate back into the blood takes place in the proximal convoluted tubule. It consists of microvilli which increases surface area of absorption. Many substances are reabsorbed here, including some water, electrolytes such as sodium and chloride, and organic nutrients such as glucose. The main function of the collecting ducts is to reabsorb as much water as the body needs. Gladys Kalpana M. Pharm 25
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Hormones that influence selective reabsorption Parathyroid hormone. Secreted by the parathyroid glands and together with calcitonin from the thyroid gland regulates the reabsorption of calcium and phosphate from the distal collecting tubules, so that normal blood levels are maintained. Increases the blood calcium level and calcitonin lowers it. Antidiuretic hormone (ADH). secreted by the posterior pituitary. Increases the permeability of the distal convoluted tubules and collecting tubules, increasing water reabsorption. Secretion of ADH is controlled by a negative feedback system. Gladys Kalpana M. Pharm 26
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Hormones that influence selective reabsorption Aldosterone. Secreted by the adrenal cortex, this hormone increases the reabsorption of sodium and water, and the excretion of potassium. Secretion is regulated through a negative feedback system. Atrial natriuretic peptide, ANP. Secreted by the atria of the heart in response to stretching of the atrial wall when blood volume is increased. Decreases reabsorption of sodium and water from the proximal convoluted tubules and collecting ducts. Secretion of ANP is also regulated by a negative feedback system. Gladys Kalpana M. Pharm 27
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Tubular secretion Filtration occurs as blood flows through the glomerulus. Substances not required and foreign materials, e.g. drugs including penicillin and aspirin, may not be entirely filtered out of the blood because of the short time it remains in the glomerulus. Such substances are cleared by secretion from the peritubular capillaries into the filtrate within the convoluted tubules. Tubular secretion of hydrogen ions (H+) is important in maintaining normal blood pH. Gladys Kalpana M. Pharm 28
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Composition of urine Urine is clear and amber in colour due to the presence of urobilin, a bile pigment altered in the intestine, reabsorbed then excreted by the kidneys. The specific gravity is between 1020 and 1030, and the pH is around 6 (normal range 4.5–8). A healthy adult passes from 1000 to 1500 mL per day. The volume of urine produced and the specific gravity vary according to fluid intake and the amount of solute excreted. Gladys Kalpana M. Pharm 30
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The composition of urine are Water Urea Uric acid Creatinine Ammonia Sodium Potassium Chlorides Phosphates Sulphates oxalates Gladys Kalpana M. Pharm 31
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Electrolyte balance the balance between water and electrolyte concentration is done by Sodium and potassium balance by Renin–angiotensin–aldosterone system. Calcium balance Regulation of calcium levels is maintained by secretion of parathyroid hormone and calcitonin Gladys Kalpana M. Pharm 32
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pH balance In order to maintain normal blood pH (acid–base balance), the proximal convoluted tubules secrete hydrogen ions into the filtrate where they combine with buffers (p. 25): bicarbonate, forming carbonic acid (H+ + HCO- 3 H 2CO) ammonia, forming ammonium ions (H+ +NH3 NH +4 ) hydrogen phosphate, forming dihydrogen phosphate (H + + HPO32- H2 PO3- Gladys Kalpana M. Pharm 33
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Carbonic acid is converted to carbon dioxide (CO2) and water (H2O), and the CO2 is reabsorbed, maintaining the buffering capacity of the blood. Hydrogen ions are excreted in the urine as ammonium salts and hydrogen phosphate. Gladys Kalpana M. Pharm 34
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Ureters Ureters carry urine from the kidneys to the urinary bladder. They are about 25–30 cm long with a diameter of approximately 3 mm. The ureter is continuous with the funnel-shaped renal pelvis. As urine accumulates and the pressure in the bladder rises, the ureters are compressed and the openings into the bladder are occluded. This prevents backflow (reflux) of urine into the ureters (towards the kidneys) as the bladder fills and also during micturition, when pressure increases as the muscular bladder wall contracts. Gladys Kalpana M. Pharm 35
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The walls of the ureters consist of three layers of tissue: an outer covering of fibrous tissue, continuous with the fibrous capsule of the kidney a middle muscular layer consisting of interlacing smooth muscle fibres that form a functional unit round the ureter and an additional outer longitudinal layer in the lower third an inner layer, the mucosa, composed of transitional epithelium Gladys Kalpana M. Pharm 36
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Urinary bladder The bladder is roughly pear shaped, but becomes more balloon shaped as it fills with urine. The posterior surface is the base. The bladder opens into the urethra at its lowest point, the neck. the outer layer of loose connective tissue, containing blood and lymphatic vessels and nerves, covered on the upper surface by the peritoneum the middle layer, consisting of interlacing smooth muscle fibres and elastic tissue loosely arranged in three layers. This is called the detrusor muscle. And when it contracts, it empties the bladder. the inner mucosa, composed of transitional epithelium that readily permits distension of the bladder as it fills. The total capacity is rarely more than about 600 mL. Gladys Kalpana M. Pharm 38
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The three orifices in the bladder wall form a triangle or trigone. The internal urethral sphincter, a thickening of the urethral smooth muscle layer in the upper part of the urethra, controls outflow of urine from the bladder. This sphincter is not under voluntary control. Gladys Kalpana M. Pharm 40
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Urethra The urethra is a thin, fibromuscular tube that begins at the lower opening of the bladder and extends through the pelvic and urogenital diaphragms to the outside of the body, called the external urethral orifice. The urethra also connects the to the ductus deferens in males, for the ejaculation of sperm. There is a sphincter at the upper end of the urethra, which serves to close the passage and keep the urine inside the bladder. As the passage needs to traverse the length of the penis, it is significantly longer in males than females. It is approximately 4 cm in length for females, whereas it is about 20 cm in the male body. Gladys Kalpana M. Pharm 41
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Urethra The male urethra consists of three parts: Prostatic part descends through the prostate and can dilate to change significantly in size Membranous part exists between the prostate and the beginning of the penis and is the section targeted if a catheter needs to be inserted Spongy part traverses the penis to end at the external urethral orifice Gladys Kalpana M. Pharm 42
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Micturition Normal urination or emptying (voiding) of bladder is called as micturition. Micturition occurs in the following stages: Urine is made in the kidneys Urine is stored in the bladder The sphincter muscles relax The bladder muscle (detrusor) contracts The bladder is emptied through the urethra and urine is removed from the body. Gladys Kalpana M. Pharm 45
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Micturition In infants, accumulation of urine in the bladder activates stretch receptors in the bladder wall generating sensory (afferent) impulses that are transmitted to the spinal cord, where a spinal reflex is initiated. This stimulates involuntary contraction of the detrusor muscle and relaxation of the internal urethral sphincter, and expels urine from the bladder – this is micturition or voiding of urine. When bladder control is established, the micturition reflex is still stimulated but sensory impulses also pass upwards to the brain and there is awareness of the need to pass urine as the bladder fills (around 300–400 mL in adults). Gladys Kalpana M. Pharm 46
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RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM The renin-angiotensin-aldosterone system (RAAS) plays an important role in regulating blood volume and systemic vascular resistance, which together influence cardiac output and arterial pressure. As the name implies, there are three important components to this system: 1) renin, 2) angiotensin, and 3) aldosterone. Renin, which is released primarily by the kidneys, stimulates the formation of angiotensin in blood and tissues, which in turn stimulates the release of aldosterone from the adrenal cortex. Gladys Kalpana M. Pharm 47
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Renin is a proteolytic enzyme that is released into the circulation by the kidneys. Its release is stimulated by: sympathetic nerve activation (acting through β1-adrenoceptors) renal artery hypotension (caused by systemic hypotension or renal artery stenosis) decreased sodium delivery to the distal tubules of the kidney. Gladys Kalpana M. Pharm 48
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When renin is released into the blood, it acts upon a circulating substrate, angiotensinogen, that undergoes proteolytic cleavage to form the angiotensin I. Vascular endothelium, particularly in the lungs, has an enzyme, angiotensin converting enzyme (ACE), that cleaves off two amino acids to form the angiotensin II (AII), although many other tissues in the body (heart, brain, vascular) also can form AII. Gladys Kalpana M. Pharm 49
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Constricts blood vessels thereby increasing systemic vascular resistance and arterial pressure Stimulates sodium transport (reabsorption) at several renal tubular sites, thereby increasing sodium and water retention by the body. Acts on the adrenal cortex to release aldosterone, which in turn acts on the kidneys to increase sodium and fluid retention Stimulates the release of vasopressin (antidiuretic hormone, ADH) from the posterior pituitary, which increases fluid retention by the kidneys Stimulates thirst centers within the brain. Facilitates norepinephrine release from sympathetic nerve endings and inhibits norepinephrine re-uptake by nerve endings, thereby enhancing sympathetic adrenergic function Stimulates cardiac hypertrophy and vascular hypertrophy Gladys Kalpana M. Pharm 50
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When renal blood flow is reduced or blood sodium levels fall, the enzyme renin is secreted by kidney cells. Renin converts the plasma protein angiotensinogen, produced by the liver, to angiotensin 1. Angiotensin converting enzyme (ACE), formed in small quantities in the lungs, proximal kidney tubules and other tissues, converts angiotensin 1 to angiotensin 2, which stimulates secretion of aldosterone. Angiotensin 2 causes vasoconstriction and increases blood pressure closing the negative feedback loop. Gladys Kalpana M. Pharm 51
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Diseases of kidney Glomerulonephritis: Inflammatory conditions of glomerulus Haematuria, asymptomatic proteinuria, acute nephritis and nephrotic syndrome. Gladys Kalpana M. Pharm 53
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Nephrotic syndrome: Group of symptoms that affect kidney such as marked proteinuria, hypoalbuminemia, generalized oedema, hyperlipidemia. Gladys Kalpana M. Pharm 54
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Diabetic nephropathy: Progressive damage of glomeruli, proteinuria and nephrotic syndrome Ascending infection leading to acute pyelonephritis atheroma of the renal arteries and their branches leading to renal ischaemia and hypertension Chronic renal failure Gladys Kalpana M. Pharm 55
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Hypertension: Hypertension can be the cause or the result of renal disease. Essential and secondary hypertension both affect the kidneys when renal blood vessel damage causes ischaemia. The reduced blood flow stimulates the renin–angiotensin–aldosterone system, raising the blood pressure still further. Gladys Kalpana M. Pharm 56