Excretion in Humans PDF

Y SYSTEMS THE BOD EXCRETION IN HUMANS EXCRETORY ORGANS AND THEIR EXCRETED PRODUCT  Excretory organ Substances that they excrete Origin of these substances Lungs Carbon...

Y SYSTEMS THE BOD EXCRETION IN HUMANS EXCRETORY ORGANS AND THEIR EXCRETED PRODUCT  Excretory organ Substances that they excrete Origin of these substances Lungs Carbon dioxide if formed as a product of cellular respiration Carbon dioxide and water vapour are excreted Excess water is formed as a product of cellular in exhaled air during breathing respiration as well as from the intake of fluids and food Excess water is formed as a product of cellular Kidneys and bladder respiration as well as from the intake of fluids and Urine. Urine consists of excess water, mineral food salts and nitrogenous waste e.g. urea and uric Urea is formed in the liver from deamination of acid. The bladder temporarily stores the urine excess amino acids. The urea is transported by the that was formed by the kidneys. Urine passes blood to the kidneys. out of the body when we urinate. Uric acid is the end product of metabolism of nucleic acids Liver Bile pigments are formed in the liver during breakdown of haemoglobin Bile pigments and urea Urea is formed in the liver from deamination of excess amino acids. The urea is transported by the blood to the kidneys. Excretory organ Substances that they excrete Origin of these substances Alimentary canal Bile pigments are formed in the liver during breakdown of haemoglobin. The bile pigments from Bile pigments the liver enters the alimentary canal and are excreted as bile salts in the faeces. Skin Sweat. Sweat consists of excess Excess water is formed as a product of cellular water, salts and a small amount of respiration as well as from the intake of fluids and urea. Sweat is excreted through food sweat glands in the skin. THE URINARY SYSTEM Structure of the different parts of the urinary system  TURE OF A KIDNEY STRUC The kidneys are dark-red bean shaped organs. In the middle of the concave side is an indentation, the hilum where the renal artery enters and the renal vein and ureter leave the kidney. The kidneys are protected against mechanical injuries by a layer of fat that surrounds the kidneys. Each kidney is surrounded by a connective tissue membrane, the renal capsule which protects the kidney. A reddish-brown region, called the cortex, can be found just under the renal capsule. The medulla is the inner region of the kidney and is lighter in colour and contains groups of tubes. Each group of tubes forms a pyramid which project into the renal pelvis.  RE OF A NEPHRON STRUCTU The main functions of the nephron are to filter the blood, regulate the waste, water and other important Each kidney is made up of about one million substances the body needs. microscopic structures called nephrons. Each nephron can be divided into 2 separate The nephrons are the structural and functional units sections i.e. the Malpighian body and the renal of the kidney. tubule. The structure of the Malpighian body  ALPIGHIAN BODY CTURE OF THE M STRU The Malpighian body consists of a cup-shape structure called the Bowman capsule and a network of blood capillary vessels called the glomerulus. The blood capillary vessels of the glomerulus are lined with a single layer of squamous epithelial cells with pores between the cells. The wider blood vessel that transports blood to the glomerulus is called the afferent arteriole. The narrower blood vessel that transports blood away from the glomerulus is called the efferent arteriole. The inner wall of the Bowman’s capsule consists of specialized cells called podocytes. The podocytes are cells with projections between which small openings, called the filtration slits occur.  HE RENAL TUBULE STRUCTURE OF T The renal artery that enters the kidney branches into smaller arteries. These smaller arteries eventually form the afferent arteriole. The efferent arteriole branches and forms the network of capillaries, the peritubular capillary network, which surrounds the renal tubule. The peritubular capillaries combine to form venules which eventually form the renal vein which transports deoxygenated blood to the heart.  HE RENAL TUBULE STRUCTURE OF T The renal tubule is a long convoluted tubule that consists of the proximal convoluted tubule, the loop of Henle and the distal convoluted tubule. The renal tubule is lined with a single layer of cuboidal epithelium. The distal convoluted tubules open into a collecting duct. A few collecting ducts converge and form the ducts of Bellini. The ducts of Bellini form the pyramids that open into the renal pelvis. FUNCTIONING OF THE KIDNEY  RE OF A NEPHRON STRUCTU  NG OF THE KIDNEY FUNCTIONI GLOMERULAR FILTRATION TUBULAR REABSORPTION TUBULAR EXCRETION https://www.youtube.com/watch?v=l128tW1H5a8  NG OF THE KIDNEY FUNCTIONI GLOMERULAR FILTRATION  ULAR FILTRATION GLOMER Glomerular filtration occurs in the Malpighian body. The blood in the glomerulus is under high pressure because of the wider afferent arteriole and the narrower efferent arteriole. The thin endothelium with pores which lines the blood capillaries of the glomerulus and the podocytes with filtration slits form an ultrafine filter through which the filterable substances in the blood are forced. Blood cells and plasma proteins are too large to filter and they remain in the blood of the capillaries.  ULAR FILTRATION GLOMER The part of the blood that filters into the Bowman’s capsule is known as the glomerular filtrate. The glomerular filtrate contains useful substances: water, amino acids, glucose, vitamins, mineral salts waste products e.g. urea, uric acid and creatinine.  IGHIAN BODY FOR IONS OF TH E MALP ADAPTAT FILTRATION The afferent arteriole is wider than the efferent arteriole, which causes a high blood pressure in the glomerulus, promoting filtration. The capillary network of the glomerulus has a large surface area, which increases the efficiency of filtration. The Bowman's capsule is cup-shaped, which provides a large surface for effective filtration. The endothelial layer of the glomerular capillaries and the podocyte layer of the Bowman's capsule form an ultrafine filter through which substances are filtered. The endothelial layer has pores that only allow smaller parts of the blood to filter through. The podocytes have filtration slits that only allow smaller parts of the blood to filter through.  NG OF THE KIDNEY FUNCTIONI TUBULAR REABSORPTION  R REABSORPTION TUBULA Useful substances that pass through the glomerular membrane during filtration must now be reabsorbed and returned to the bloodstream. The filtrate leaves the Bowman’s capsule and enters the proximal convoluted tubule. As the filtrate moves through the proximal convoluted tubule all the glucose, amino acids and water-soluble vitamins are actively reabsorbed into the peritubular capillary blood vessels Mineral salts e.g. sodium ions and fat-soluble vitamins are also actively reabsorbed as they are needed by the body. Most of the water is passively reabsorbed through osmosis into the peritubular capillaries.  R REABSORPTION TUBULA The filtrate enters the loop of Henle. An increased sodium concentration in the medulla of the kidney creates a water potential gradient which lead to the passive osmosis of water. The descending loop of Henle is permeable to water and water is passively reabsorbed by osmosis. Sodium ions are actively pumped out of the ascending loop of Henle into the tissue fluid of the medulla (sodium pump) and chloride ions follow passively. The ascending loop of Henle is impermeable to water. As the filtrate moves through the distal convoluted tubule further reabsorption of useful substances takes place. From the distal convoluted tubule, the filtrate moves to the collecting duct  NG OF THE KIDNEY FUNCTIONI TUBULAR EXCRETION  CRETION TUBULAR EX Substances are secreted from the blood in the surrounding peritubular capillaries through the epithelium of the renal tubule and added to the filtrate. This process occurs in the proximal and distal convoluted tubules. Hydrogen ions, potassium ions, creatinine, urea, drugs and other foreign substances are actively added to the filtrate. The secretion of hydrogen ions from the blood into the tubules occurs when the pH of the blood becomes too low. The excess hydrogen ions are therefore removed from the blood and the pH of the blood increases.  CRETION TUBULAR EX When the pH of the blood increases, fewer hydrogen ions are secreted from the blood into the tubules but more bicarbonate ions are secreted from the tubules into the blood. Bicarbonate ions increase the pH of the blood. The filtrate now moves into the collecting ducts and is called urine. Urine consists of: Water Inorganic salts Metabolic wastes Foreign substances  NG OF THE KIDNEY FUNCTIONI GLOMERULAR FILTRATION TUBULAR REABSORPTION TUBULAR EXCRETION https://www.youtube.com/watch?v=l128tW1H5a8 HOMEOSTATIC CONTROL  N BY THE KIDNEYS TATIC REGULATIO HOMEOS The human body has the ability to maintain a stable internal environment – this is homeostasis. It is important that the body’s temperature is kept within a narrow range of around 37°C. The pH of the body fluids needs to be regulated and the composition of these fluids need to be kept within certain limits for effective metabolism. The kidney is involved in 3 homeostatic mechanisms: the regulation of pH of the blood (as discussed) the regulation of water levels (osmoregulation) the regulation of salt levels in the blood  STATIC CONTROL HOMEO REGULATION OF THE WATER CONTENT OF THE BLOOD  ENT OF THE BLOOD THE WATER CONT REGULATION OF The part of the brain that controls the water balance in the body is called the hypothalamus. The hypothalamus controls the release of a hormone called ADH (anti-diuretic hormone) The hormone ADH is secreted by the hypophysis (pituitary gland), which is an endocrine gland at the base of the brain ADH affects the water permeability of the walls of the distal convoluted tubule and collecting duct of the nephron If the walls are permeable then more water passes out of the distal convoluted tubule into the blood and water is conserved in the body. If the walls are impermeable then very few water is retained in the body and it passes out of the kidneys in the form of urine. When the blood has more water than normal e.g. on a cold day when a person does not sweat a lot or takes in a lot of fluids The hypothalamus is stimulated and sends impulses to the hypophysis to secrete less or stop secreting the hormone ADH Less ADH/no ADH is transported in the blood to the kidneys The collecting ducts and distal convoluted tubules of the kidney become less permeable to water Less water is re-absorbed and passed to the surrounding blood vessels More water is excreted in the urine The urine is less concentrated (more diluted) The water content in the blood decreases and returns to normal When the blood has less water than normal e.g. on a warm day when a person sweats a lot or takes in very little fluid The hypothalamus is stimulated and sends impulses to the hypophysis to secrete more of the hormone ADH ADH is transported in the blood to the kidneys The collecting ducts and distal convoluted tubules of the kidney become more permeable to water More water is re-absorbed and passed to the surrounding blood vessels Less water is excreted in the urine The urine is more concentrated The water content in the blood increases and returns to normal  STATIC CONTROL HOMEO REGULATION OF THE SALT CONCENTRATION  When the salt level in the blood increases Receptor cells in the afferent and efferent arterioles of the kidney detects the high salt/sodium ion level The adrenal gland is stimulated to stop secreting aldosterone/to secrete less aldosterone The re-absorption of sodium ions from the renal tubules in the kidney into the blood vessels decreases The sodium ion concentration in the blood decreases and returns to normal  When the salt level in the blood decreases Receptor cells in the afferent and efferent arterioles of the kidney detects the low salt/sodium ion level The adrenal gland is stimulated to secrete more aldosterone The re-absorption of sodium ions from the renal tubules in the kidney into the blood vessels increases The sodium ion concentration in the blood increases and returns to normal KIDNEY DISEASES  Disease Effect on the kidneys Kidney stones Hard calcium granules that form in the pelvic region of the kidney. Caused by a diet high in protein, sugars and coca cola, dehydration and / or inherited conditions. Symptoms include severe back pain and blood in the urine Renal failure Caused by the abuse of pain medication and illegal drugs. Acute and Chronic renal failure This disease is common in Africa, South America and Asia. It is caused by a parasitic Bilharzia infection flatworm, Schistosoma, which is found in rivers and dams. The worm larvae which are hosted by snails in the water, attach to the skin of a human. They travel in the blood stream and then release their eggs. These eggs damage the kidneys, ureters and the bladder. The infected person will pass blood in the urine, have a fever and rashes, will be tired and often anaemic. Bilharzia can be prevented by avoiding infected water and treatment to ease the symptoms are available.  O NIC AND ACUTE ATM EN T FO R C HR DIALYSIS TRE KID N EY FA ILU RE Dialysis involves a process where a patient’s blood is passed through a filtration system and returned to the body. Certain hospitals in South Africa have dialysis centres and patients have to book a time because of the demand for these machines. Dialysis is an expensive treatment and is scarce in the public health hospitals. https://www.youtube.com/watch?v=9KZHowze7lg  RANSPLANTS KIDNEY T A patient with both kidneys seriously damaged could be considered for a kidney transplant. A donor donates one of their kidneys to the patient with kidney failure (the recipient). A person would be a suitable donor if he or she has the same blood group (A, B, AB or O) as the intended recipient, and if they have a very close tissue match. The ideal donor would be a blood relative of the patient. The recipient might reject the donated kidney and is given immunosuppressive drugs to reduce the chances of organ rejection. These drugs can have bad side-effects and there is often a shortage of organ donors. There are legal and ethical aspects of organ donation that need to be considered by donors and recipients in South Africa.  Y SYSTEMS THE BOD QUESTIONS