Presentation on theme: "HUMAN EXCRETORY SYSTEM The role of liver in excretion: 1.Detoxification: The liver removes harmful substances such as bacteria, certain drugs and hormones."— Presentation transcript:
HUMAN EXCRETORY SYSTEM The role of liver in excretion: 1.Detoxification: The liver removes harmful substances such as bacteria, certain drugs and hormones from blood. Within the liver these substances are changed into inactive or less poisonous forms. It detoxifies the blood. 2.Excretion of bile 3.Formation of urea: Amino acids are the breakdown products of proteins. Because excess amino acids cannot be stored in the body, they are broken down in the liver. The parts of the amino acids are changed into other substances. From each amino acid, the amino group (NH 2 ) is changed into ammonia (NH 3 ). The reminder of the amino acid molecule is either changed into pyruvic acid and used as an energy source in cellular respiration. Or it is changed glycogen or fat for storage.
HOC C NH 2 O H R Growth and repair synthesis excess HOC C NH 2 O H R NH 3 (ammonia) urea amino acid carbon skeleton use as energy source or converted to glycogen or fat Formation of Urea
The urinary system is made up of: Kidneys UretersBladder Urethra are the organs that produce urine urine passes from each kidney through a tube called ureter urine is stored here during urination, the stored urine travels from the bladder to the outside of the body through urethra
Kidney Structure The kidneys are important for 2 reasons: They remove the wastes of cellular metabolism from the blood They regulate the concentrations of the substances found in the body fluids
Kidney Structure The kidney has 3 parts: the outer part is the cortex (kabuk) the middle part is the medulla (öz) the inner region is the pelvis (havuzcuk)
Kidney Structure Blood is filtered in the cortex. The medulla is made up of tubes called collecting ducts. These ducts carry the filtered substances (filtrate) to the pelvis. Pelvis is the cavity connected to the ureter. Urine formed from the filtrate drains from the pelvis into the ureter.
Nephron is the functional unit of kidneys. Each kidney has about 1.25 millions of nephrons. A nephron is composed of: Malpighi body + proximal + loop of Henle + distal + collecting tubule tubule duct Malpighi body = glomerulus + Bowman’s capsule
Nephrons The glomerulus is a group of capillaries that form a tight ball. It is surrounded by a double-walled, cup-shaped structure which is called Bowman’s capsule. From the blood in the glomerulus, substances are filtered into Bowman’s capsule. The filtrate exits Bowman’s capsule through the renal tubule, a long tubule that empties into a collecting duct. The middle section of the renal tubule forms a long loop called the loop of Henle which extends into the medulla.
The collecting duct which receives the filtrate from many nephrons, leads from the medulla into the pelvis. Blood enters the kidneys through the renal artery, and leaves the kidneys through the renal pelvis. Each nephron has one arteriole that carries blood from the renal artery to the nephron. The arteriole branches to form the renal capillaries that make up the glomerulus. Before leaving Bowman’s capsule, the capillaries join together into a single arteriole. The new arteriole subdivides into a second capillary network that surrounds the renal tubule. The capillaries then merge again, this time to form a venule. This pattern of blood flow around the nephron is unusual because there are two sets of capillaries, rather than one between the arteries and veins. Nephrons
Urine Formation FiltrationReabsorption Both useful substances and wastes are removed from the blood. Some of the useful substances reenter the blood to be used by the body. Filtration: - takes place in the glomeruli and Bowman’s capsule - the blood that enters a glomerulus is under pressure Net filtration = blood – plasma protein + Bowman’s capsule pressure pressure osmotic pressure pressure = 70mmHg - (32mmHg + 14mmHg) = 24 mmHg
GLOMERULAR CAPILLARIESSYSTEMIC CAPILLARIES Since they are found between two arteries (arterioles), blood pressure remains along the capillaries. Since they are found between the arteries and veins blood pressure drops as blood passes from the arteries to the veins. Blood pressure is about 70mmHg.Blood pressure is 35 mmHg at the arteriole end and 15 mmHg at the venule end. The wall of the glomerular capillaries is covered with capillary endothelium and Bowman’capsule endothelium. These layers prevent exit of the blood cells and blood proteins from the glomerular capillaries and make the glomerular capillaries resist to high blood pressure. The wall of the blood capillaries is covered with a single layer of endothelium. This layer cannot prevent the passage of blood proteins and white blood cells out of the blood. They are more permeable because they have high amounts of pores. The blood pressure is higher than the osmotic pressure of the plasma proteins in the glomerular capillaries so glomerular capillaries make only filtration. At the arteriole end filtration, at the venule end reabsorption occurs.
Urine Formation FILTRATION: Filtration takes place in the glomeruli and Bowman’s capsules. The blood that enters a glomerulus is under pressure Net filtration pressure=(blood pressure –(protein osmotic pressure+ Bowman’s capsule pressure)) Net filtration pressure= (70mm-Hg – (32mm-Hg + 14 mm- Hg)) = 24 mm-Hg The pressure forces the filtrate, which includes water, urea, glucose, amino acids, and various salts through the thin walls of the glomerulus into Bowman’s capsule. *Blood cells and blood proteins are too large to pass through the walls of the glomerulus. They remain in the blood. The filtrate that enters the Bowman’s capsule is like blood plasma, but it does not contain blood proteins.
The kidneys form about 180 liters of filtrate in a 24-hour period. However, only about liter of urine is actually produced by the kidneys in 24 hours. In a minute, 125 ml filtrate is formed. If blood pressure of renal artery is higher than 180mm-Hg or lower than 80 mm-Hg, human body loses its auto control. Urine Formation
REABSORBTION AND TUBULAR SECRETION:REABSORBTION AND TUBULAR After the filtrate has left Bowman’s capsule, reabsorption occurs in the renal tubule. It is the process of reabsorption that reduces the volume of filtrate and returns various important substances to the blood for homeostasis. During filtration 125 ml of fluid passes into the Bowman’s capsule in one minute. 124 ml of this fluid is reabsorbed into the blood. Reabsorption occurs by osmosis, diffusion and active transport. Every substance in the blood has a threshold level. If the amount of a substance in the blood is over the threshold level, it is not reabsorbed through the tubules of nephron, instead it is excreted with urine. (For example: in a healthy person’s blood for each 100 ml of blood there is 180 mg of glucose. If the amount of glucose is increased in the blood, glucose is observed in the urine )
I. IN PROXIMAL TUBULEI. IN PROXIMAL Most of the filtrate, (about 80%) that has passed from the Bowman’s capsule is reabsorbed by active and passive transport in the proximal tubule. From the filtrate glucose, amino acids, vitamins, various ions (Na +, K +, Ca +2, Mg +2, HCO 3 -, PO 4 -3,SO 4 -2 ), urea, and uric acids are reabsorbed. Na+ is reabsorbed by active transport. Cl- is reabsorbed by diffusion. H 2 O is reabsorbed by osmosis. Creatinin is not reabsorbed. Glucose, amino acids and K + are reabsorbed by active transport. Some excess and foreign substances (creatinin, penicillin, H +, NH 3 ) are taken from the blood by proximal tubule cells and secreted into filtrate.
Urine Formation II. LOOP of HENLEII. LOOP of The filtrate is concentrated in the loop of Henle. Descending loop is permeable to water but impermeable to salt (NaCl) - Water is reabsorbed by osmosis at the descending loop - The filtrate becomes hypertonic Ascending loop is permeable to salt (NaCl) but impermeable to water. - NaCl is reabsorbed by diffusion at the lower (thinner) part but NaCl is reabsorbed by active transport at the upper (thicker) part. - The filtrate becomes hypotonic
Urine Formation III. DISTAL TUBULEIII. DISTAL Once the filtrate is in the distal tubule, its composition is determined. Distal tubule is impermeable to urea. Re-absorption of water takes place under the control of ADH (vasopressin) according to body’s water requirement. Re-absorption of Na + and secretion of K + take place under the control of aldosteron according to body’s requirement. Reabsorption of Cl - by passive transport follows the reabsorption of Na+ by active transport. Reabsorption of Ca +2 takes place under the control of parathormone according to the body’s requirement. Distal tubule regulates the blood pH (7.4) -When pH of blood drops, through the cells of distal tubule, reabsorption HCO 3 -, and secretion of H + increase with NH 3 - When pH of blood increases, through the cells of distal tubule, reabsorption of HCO 3 -, and secretion of H+are decreased.
Urine Formation IV. COLLECTING DUCTIV. COLLECTING Urine is concentrated in the collecting duct. The lower part of the collecting duct is permeable to urea. By diffusion, urea passes in to the tissue fluid of medulla, and with NaCl it increases the osmotic pressure of the medium (hypertonic medium). With this change, water is reabsorbed (under the control of ADH) and urine is concentrated. Healthy adult people produce 1500ml urine per day. Urine consists of (95-96%) water, remaining is urea, uric acid, creatinin, and mineral salts. A healthy person’s urine does not contain blood cells, plasma proteins, glucose, and amino acids. pH of urine is between pH of urine changes according to physiological conditions and nutrition of the person.
Urine Formation TUBULAR SECRETIONTUBULAR Not all materials are subjected to the filtering and selective-reabsorbtion strategy. Some larger molecules, such as penicillin, by pass the pores of the glomerulus’s and are actively removed from the blood in the second bed of capillaries adjacent to the tubules. This tubular secretion supplements glomerular excretion and increases the efficiency of the overall excretory regulation of blood composition. Tubular secretion is actually a misnomer since it is the second bed of capillaries, not the tubules, that does not the secreting.
EXCRETION IN PLANTS
Gas Exchange: In green plants, not all metabolic wastes are excreted; some are used by the plants. This is true to some extent for oxygen and carbondioxide. Plants carry on cellular respiration both day and night. Oxygen, which is needed for cellular respiration, is a by product of photosynthesis. During the day, when photosynthesis is occuring, some of the oxygen produced is used for cellular respiration. The rest diffuses out of the plant through the stomates of the leaves. Carbondioxide, which is an end product of cellular respiration, is used in photosynthesis. Thus, during the day, the carbondioxide produced by cellular respiration is used in photosynthesis. At night, when there is no light reactions of photosynthesis going on, carbondioxide is excreted through the stomates and lenticels.
EXCRETION IN PLANTS Nitrogenous and Other Wastes: Nitrogenous, or nitrogen containing, wastes are normally excreted by animals, but may be used by plants. When, for example, there are excess amino acids, the amino group (NH 2 ) is removed, and the nitrogen is used in the synthesis of other compounds required by the plants. Other wastes may be stored within vacuoles in in certain cells, either in solution or as crytals. Spinach, for example, stores oxalic acid crytals in the vacuoles of its leaf cells. Actively dividing meristematic cells grow away from their waste materials. The wastes are simply left behind in the cells produced by these tissues.