The Urinary System - Anatomy & Function

The urinary system ( ur/o, urin/o ) has two major functions: the excretion of harmful waste products and the regulation of homeostasis. Let us take a look at the **structures **of the urinary system. Kidneys (nephr/o, ren/o) The kidneys filter the blood to remove wastes and excess water and salts...

The urinary system ( ur/o, urin/o ) has two major functions: the excretion of harmful waste products and the regulation of homeostasis. Let us take a look at the **structures **of the urinary system. Kidneys (nephr/o, ren/o) The kidneys filter the blood to remove wastes and excess water and salts. There are two kidneys which are located on either side of the spine, outside the peritoneum (**retroperitoneal**) in the lumbar region. This system also secretes substances such as renin, which raises blood pressure to maintain circulation through the kidney, and erythropoietin, which stimulates red blood cell production. The system also secretes a form of vitamin D called calciferol. Urine Formation The **nephron **is the functional unit of the kidney. The approximately one million nephrons in each kidney filter the blood and concentrate the waste into urine. There are three parts to a nephron, the glomerulus, the glomerular (Bowman) capsule, and the renal tubule. 1. Glomerular filtration a. albuminuria 2. Tubular reabsorption 3. Tubular secretion Urine formation is an important process in ridding the body of any metabolic wastes and toxins via the kidneys. The glomerus is responsible for filtering blood and water so that it can pass out of the capillaries and into the Bowman capsule. Proteins and blood cells should not appear in the urine because the walls of the glomeruli prevent those large substances from filtering through. Reabsorption ensures that the body retains essential substances such as sugar or salt. Secretion is the final process of some substances being secreted from the bloodstream and into the renal tubule. Urine is 95% water and 5% waste (urea, creatinine) salts, acids, and drugs. Urea is one of those wastes that can become toxic if it accumulates instead of being properly excreted. Ureters (ureter/o) The ureters carry urine from the renal pelvis of each kidney to the urinary bladder. Ureters are approximately 25--30 cm long. Peristalsis is used to move urine downward. Urinary Bladder (cyst/o, vesic/o) The bladder, a hollow, muscular organ that acts as a reservoir for urine, is located in the anterior portion of the pelvic cavity. As the bladder fills with urine from the ureters, the walls stretch and receptors send a message to the brain which creates the urge to micturate. Urethra (urethr/o) This structure carries urine from the bladder to the urinary meatus. In females, the urethra conveys only urine and is approximately 3--4 cm long. In males, the urethra carries both urine and semen and is approximately 17--20 cm long. The beginning of the male urethra is surrounded by the prostate gland. The shortened length of the urethra in females makes it more difficult for women to flush out bacteria. Females are statistically more prone to contracting urinary tract infections (UTI). **Combining Form** **Meaning** -------------------- ----------------- Nephr/o; Ren/o Kidney Pyel/o Renal pelvis Ureter/o Ureter Cyst/o; Vesic/o Bladder Urethr/o Urethra Ur/o; urin/o Urine **Combining Form** **Meaning** Meat/o Meatus; opening Peritone/o Peritoneum Glomerul/o Glomerulus Cortic/o Cortex Medull/o Medulla Albumin/o Albumin **Prefix / Suffix** **Meaning** --------------------- ---------------------------- A-; An- Not; without Retro- Behind -uria Urination, urine condition -logist One who studies -al; -ar; -ic; -ary Pertaining to