As long as you are alive, your body will constantly metabolize organic molecules and produce waste products. If you can not get rid of these metabolic waste products, they will accumulate to toxic levels and poison your body. The urinary system is very important because it perform the essential function of getting rid of these metabolic wastes. Main Structures of the Urinary System
The main structures that make up the urinary system are two kidneys (contains nephrons), two ureters, one bladder, one urethra, arteries and veins. The Ureter connects the kidney to the bladder. The bladder is storage for urine. Urine is excreted to the outside of the body through the urethra. Kidney
The kidneys are two bean-shaped organs located outside the peritoneum at the posterior of the upper abdomen. The kidneys are located one on each side of the vertebral columns and are protected by the ribs and a layer of fat. The renal artery, renal vein and ureter connect to the kidney at the indented media border called the hilus. Besides Urine Formation, the kidney has the following functions: 1. Plays a major role in regulating blood volume because it controls the amount of water to be excreted and the amount of water to be reabsorbed. 2. Regulates electrolytes in the blood by controlling the secretion and reabsorption of sodium and potassium ions. 3. Regulates the pH of the blood by controlling the secretion and reabsorption of hydrogen ions. When more hydrogen ions are excreted from the blood, it renders the blood less acidic (more alkaline). But if more hydrogen ions are retained in the blood, this renders the blood more acidic (less alkaline). 4. Regulates blood pressure by regulating to amount of water excreted and the amount of water reabsorbed back into the blood. When the kidneys excrete less water and reabsorb more water, the blood volume will increase. An increase blood volume will lead to an increase blood pressure. On the other hand if the kidneys excrete more water and reabsorb less water, the blood volume will reduce. This will lead to reduced blood pressure.
5. Plays a role in the regulation of red blood cell production. When the number of red blood cells decreases, the level of oxygen in the blood will also decrease. This causes the kidney to secrete a substance called erythropoietin. Erythropoietin travels to the bone marrow and causes it to produce more red blood cells. When enough red blood cells have been produced, this process is shut down via a negative feedback mechanism
Structure of the Nephron
There are more than a million nephrons packed in the renal cortex of the kidney. The nephron is made up of the glomerulus and a system of tubes. The glomerulus is a network of intertwined capillaries mass. The glomerulus is enclose is a cup-shaped structure called the bowman’s capsule. The space between the bowman’s capsule and the glomerulus is called the bowman’s space. Fluid is filtered from the capillaries and the filtrate is collected into the bowman’s space through the glomerular filtration membrane. The fluid that is filtered is known as filtrate. The glomerular filtration membrane allows only elements that are small enough to pass through. The filtrate then moves through the system of tubes where elements are added (secretion from the blood) or removed (reabsorption back into the blood). From the glomerulus, the filtrate passes through 4 segments of the nephron: Proximal convoluted tubule: reabsorption of nutrients and substances that the body needs Loop of henle: thin-lobed structure that controls the concentration of the urine Distal convoluted tubule: regulates sodium, potassium and pH Collecting duct: regulates water and sodium reabsorption.
How the Nephron Works in Urine Formation
The nephron is the functional unit of the kidney. It does the job of the urinary system. The primary function of the nephron is to remove waste products from the body before they build up to toxic levels. The...
Please join StudyMode to read the full document