Physiology of Urinary System PDF

Physiology of Urinary system Urinary System: The system that makes urine and removes waste products from the body by a process called excretion. Excretion: is the process by which the unwanted substances and metabolic wastes are eliminated from the body. The urinary system...

Physiology of Urinary system Urinary System: The system that makes urine and removes waste products from the body by a process called excretion. Excretion: is the process by which the unwanted substances and metabolic wastes are eliminated from the body. The urinary system includes: 1. A pair of kidneys 2. Ureters 3. Urinary bladder 4. Urethra The urinary system is divided into two parts: The upper urinary system includes the A-Kidneys , B- Ureters. The lower urinary system includes the A-Bladder , B- Urethra. Kidneys: The kidneys are two reddish-brown bean-shaped organs ,They are located on the left and right in the retroperitoneal space, the right kidney is slightly lower than left due to the space occupied by liver, The kidney is surrounded by tough fibrous tissue call renal capsule provides protection for the soft tissue inside. The kidney is divided into major structures: A-the outer renal cortex B-The inner renal medulla C-The renal pelvis Inside the kidneys, there are several pyramid-shaped lobes located in the outer renal cortex and an inner renal medulla. Nephrons flow between these sections. Each nephron includes a filter, called the glomerulus, and a tubule. The glomerulus filters blood, which enters the kidneys through the renal arteries and leaves through the renal veins. The renal pelvis leads to the ureter on the outside of the kidney. The Nephron: Each kidney consists of about one million nephrons. The nephron is made up of a glomerulus and its tubule, The tubule is Peritubular Capillaries Efferent arteriole Bowman's Capsule and glomerulus Afferent arteriole is made up of a number of sections, the proximal tubule, the medullary loop (loop of Henle), and the distal tubule which finally empties into the collecting duct. The Functions of the Kidney 1. Regulation of the water and electrolyte content of the body. 2. Retention of substances vital to the body such as protein and glucose 3. Maintenance of acid/base balance. 4. Excretion of waste products, water soluble toxic substances and drugs. 5. Endocrine functions Renal Blood Supply Blood vessels of kidneys are highly specialized to facilitate the functions of nephrons in the formation of urine. The kidney is normally received about 20% of the cardiac output. Approximately 99% of the blood flow goes to the cortex and 1% to the medulla. The cortex is the outer part of the kidney containing most of the nephrons. The medulla is the inner part of the kidney and contains the specialized nephrons Processes of Urine Formation The kidneys filter unwanted substances from the blood and produce urine to excrete them, there are three steps to form of urine: 1-Glomerular filtration 2-Tubular Reabsorption 3-Tubular Secretion  When blood passes through glomerular capillaries, the plasma is filtered into the Bowman capsule. This process is called glomerular filtration, Filtrate from Bowman capsule passes through the tubular portion of the nephron, and while passing through the tubule, the filtrate undergoes various changes both in quality and in quantity so that many wanted substances like glucose, amino acids, water, and electrolytes are reabsorbed from the tubules. This process is called tubular reabsorption and, some unwanted substances are secreted into the tubule from peritubular blood vessels. This process is called tubular secretion Among these three processes filtration is the function of the glomerulus. Reabsorption and secretion are the functions of tubular portion of the nephron. Glomerular Filtration: is the process by which the blood is filtered while passing through the glomerular capillaries by a filtration membrane. It is the first process of urine formation. Glomerular filtration rate (GFR) is defined as the total quantity of filtrate formed in all the nephrons of both the kidneys in the given unit of time. Ureters The ureters are approximately 30 cm long. The muscular layer of the ureter create the peristaltic contractions to move the urine into the bladder. In attachment with the bladder it creates a one-way valve (a physiological sphincter rather than an anatomical sphincter) that allows urine into the bladder but prevents reflux of urine. Bladder The urinary bladder collects urine from both ureters. The bladder lies anterior to the uterus in females, The bladder is partially retroperitoneal (outside the peritoneal cavity). Urethra The urethra is a tubular organ that transport urine from the bladder to the outside of the body for disposal. The urethra is held closed by the urethral sphincter, a muscular structure that helps keep urine in the bladder until voiding can occur. Physical characteristics of urine include: 1-Color: Typically yellow-amber, but varies according to recent diet and the concentration of the urine. Drinking more water generally tends to reduce the concentration of urine, and therefore causes it to have a lighter color. Dark urine may indicate dehydration. Red urine indicates red blood cells within the urine, a sign of kidney damage and disease. 2-Smell: The smell of urine may provide health information. For example, the urine of diabetics may have a sweet or fruity odor due to the presence of ketones (organic molecules of a particular structure) or glucose. Generally fresh urine has a mild smell but aged urine has a stronger odor similar to that of ammonia. 3-The pH : normal urine is generally in the range 4.6 – 8,. For example, high protein diets result in more acidic urine, but vegetarian diets generally result in more alkaline urine. 4-Volume : 1,000 to 1,500 mL/day. Examination of urine (Urinalysis) Urinalysis is a test of urine. It's used to detect and manage a wide range of disorders, such as urinary tract infections, kidney disease, and diabetes. Urinalysis is done by: 1. Physical examination. 2. Microscopic examination. 3. Chemical analysis.