Dr Maha AlSedik Objectives Anatomy physiology of the

Dr. Maha Al-Sedik

Objectives: Ø Anatomy, physiology of the renal system. Ø Patient Assessment.

Anatomy and Physiology

The Urinary System �Paired kidneys �A ureter for each kidney �Urinary bladder �Urethra

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Functions of the kidney Removal of excess water and electrolytes Removal of excess toxins and metabolites Control of RBCs production and blood pressure through production of hormones

Main Functions of Urinary System �Removal of nitrogenous wastes from blood eg. urea, uric acid and creatinine. �Produces erythropoietin, which regulates RBC production. �Removal of excess water and electrolytes.

Kidneys Ø Located in the retroperitoneal space. Ø Lateral surface is convex Ø Medial surface is concave Ø Hilus is cleft: vessels, ureters and nerves enter and leave Ø Adrenal glands lie superior to each kidney

Ø Ureters transport urine from the kidneys to the bladder. Ø One fourth of the body’s systemic cardiac output flows through the kidney each minute.

Nephrons Ø In the cortex. Ø Structural and functional units in the kidney that form urine. Ø Each kidney in the human contains about 1 million nephrons, each capable of forming urine. Ø The kidney cannot regenerate new nephrons. Therefore, with renal injury, disease, or normal aging, there is a gradual decrease in nephron number.

Each nephron contains : q A tuft of glomerular capillaries called the glomerulus, through which large amounts of fluid are filtered from the blood. q A long tubule in which the filtered fluid is converted into urine on its way to the pelvis of the kidney.

v The substance is freely filtered but is also partly reabsorbed from the tubules back into the blood. v For each substance in the plasma, a particular combination of filtration, reabsorption, and secretion occurs. v The rate at which the substance is excreted in the urine depends on the relative rates of these three basic renal processes.

v Most substances that must be cleared from the blood, especially the end products of metabolism such as urea, creatinine, uric acid, and urates, are poorly reabsorbed and are excreted in large amounts in the urine.

Filtration Glomeruli • Reabsorption Proximal and loop of henle • secretion Distal tubule •

The rates at which different substances are excreted in the urine represent the sum of three renal processes, (1) glomerular filtration, (2) reabsorption of substances from the renal tubules into the blood (3) secretion of substances from the blood into the renal tubules.

Urinary excretion rate = Filtration rate - Reabsorption rate + Secretion rate

B A D C E F

Answer A: proximal tubule. B: Bowman capsule. C: Glomerulus. D: Distal tubule. E: Loop of Henle. F: Collecting duct.

Urine collecting ducts calyces renal pelvis ureters Urinary bladder

Ureters v the ureters are tubes made of smooth muscle fibers that propel urine from the kidneys to the urinary bladder. v In the adult, the ureters are usually 25 - 30 cm long.

Urinary Bladder �Collapses when empty �Expands when full. �The brain controls the urge to void. �External urinary sphincter remains contracted until conditions are favorable

Urethra �Part of the lower urinary tract. �Expels urine. �Male urethra is divided into three regions.