The Human Urinary System PDF

The Human Urinary System Excretion Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrate (human), this is primarily carried out by the kidney, lung and skin. M Amr ElMissiry 2...

The Human Urinary System Excretion Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrate (human), this is primarily carried out by the kidney, lung and skin. M Amr ElMissiry 2 The urinary system consists of: The upper urinary tract, consists of pair of kidneys, renal pelvis, and ureters. These structures responsible for urine formation. The lower urinary tract consists of urinary bladder, urethra, and support structures. These structures provide urine storage and elimination. M Amr ElMissiry 3 M Amr ElMissiry 4 The functions of the kidneys The major functions of the kidneys are to: Maintains the body’s pH Reabsorption of nutrients Regulates blood pressure Excretion of wastes from the body Removal of excess fluid from the body Secret hormones that help in the production of red blood cell, acid regulation M Amr ElMissiry 5 The Kidney The kidney consists of: The outer cortex renal pyramids The inner medulla The renal capsule and fat cushion, diaphragm, and ribs, offer protection and absorb shock. M Amr ElMissiry 6 M Amr ElMissiry 7 M Amr ElMissiry 8 Structural function of kidney Nephron Nephron is the functional unite of kidney. (1-1.5 million unites, each 3-5 cm) Nephron consists of: The renal corpuscle Bowman's capsule Glomerulus (Blood vessels) The renal tubules Proximal convoluted tube, Loop of Henle, Distal convoluted tube, the collecting duct M Amr ElMissiry 9 Function of the nephrons Glomerular filtration Tubular reabsorption Tubular excretion M Amr ElMissiry 10 M Amr ElMissiry 11 Blood supply to the nephron Arterial Supply Left and right renal arteries, arise directly from the abdominal aorta. The right renal artery is longer, and crosses the vena cava posteriorly. The renal artery enters the kidney via the renal hilum. Venous Drainage Left and right renal veins, directed to the vena cava. The left renal vein is longer, and travels anteriorly to the abdominal aorta. M Amr ElMissiry 12 M Amr ElMissiry 13 Blood supply to the nephron The nephron receives its blood supply from an afferent arteriole, and exits the glomerulus through an efferent arteriole. M Amr ElMissiry 14 Blood supply of the kidney M Amr ElMissiry 15 Ureters The ureter is a long, tubular organ. approximate length of 24 to 30 cm. The left ureter slightly longer than the right ureter. The ureter terminates into the posterior base of the bladder. M Amr ElMissiry 16 The urinary bladder The urinary bladder is a hollow, muscular organ. It stores approximately 300 to 600 mL in the healthy adult M Amr ElMissiry 17 The urethra The urethra is the final pathway for the elimination of urine from the body. The tube through which urine leaves the body. It empties urine from the bladder M Amr ElMissiry 18 Physiology of Urine Formation Urine formation in human body is mainly carried out in three phases namely: Glomerular filtration Reabsorption Secretion M Amr ElMissiry 19 1- Glomerular Filtration (ultrafiltration) This process occurs across the two layers: The epithelium of Bowman’s capsule, The endothelium of glomerular blood vessels, Blood pressure forces water, dissolved substances, and small molecules like waste products and ions out of the Glomerulus and into the Bowmen’s Capsule, forming a filtrate. Glomerular filtration allows all diffusible materials to pass from the blood into the nephron. Nonfilterable components, such as cells and serum albumins, proteins will exit via the efferent arteriole. M Amr ElMissiry 20 Tubular Reabsorption The filtrate passes through a series of renal tubules, where essential (useful) substances such as glucose, amino acids, and water are selectively reabsorbed back into the bloodstream. This ensures that these valuable substances are not lost in the urine. M Amr ElMissiry 21 Secretion Certain waste products, drugs, and excess ions that are not effectively filtered in the Glomerulus are actively secreted into the renal tubules. This further removes unwanted substances from the blood and adds them to the filtrate, which eventually becomes urine. Movement of hydrogen ions is one means by which the pH of body fluids is balanced. M Amr ElMissiry 22  Concentration: As the filtrate moves through the renal tubules and the Loop of Henle, water and solute are further reabsorbed, concentrating the urine and helping to conserve water in the body. Collection and Storage: The concentrated urine is collected by the collecting duct, which leads to the renal pelvis. From the renal pelvis, urine travels through the ureter to the urinary bladder for temporary storage. Elimination: When the urinary bladder is full, nerve signals trigger the urge to urinate. The bladder contracts and the urine is expelled through the urethra and out of the body. M Amr ElMissiry 23 M Amr ElMissiry 24 Concentration of the Urine The amount of water that is eliminated with the urine is regulated by a complex mechanism within the nephron that is influenced by antidiuretic hormone (ADH), a hormone released from the posterior pituitary gland. M Amr ElMissiry 25  Urine composition 95% water 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted. M Amr ElMissiry 26 Urologic disease Urologic diseases or conditions include: Urinary tract infections, Kidney stones, Bladder control problems, Prostate problems, M Amr ElMissiry 27