The Urinary System

By: April DatuAngelique Delarazan

General Functions The urinary system performs the vital

functions of removing the organic wastes products generated by cells throughout the

body. Its other essential functions are: • Regulating blood volume and blood pressure.• Regulating plasma concentrations of ions.• Helping to stabilize blood pH.

• Conserving valuable nutrients.

Major Structures

•Kidney - Inside the Kidney - Nephron - Basic Principles of Urine Production

•Urter •Urinary bladder•Urethra

Kidney•The kidney is the organ functioning in the regulation of wastes and the maintenance of normal fluid and electrolyte balance.• It is located about two inches above the body's midline just below and behind the liver in the upper abdomen and behind the lower ribs.• About one-quarter (750-1,000 pints daily) of the blood which is output by the heart is sent to the body's "filter treatment plant", where it is purified by the kidneys and circulated on to the rest of the body. It receives about 120 pints of blood per hour, even if other body systems are shorted.

Inside the Kidney

Renal capsule: thin membranous sheath that covers the outer surface of each kidney; capsule is composed of tough fibres, chiefly collagen and elastin (fibrous proteins), that help to support the kidney mass and protect the vital tissue from injury

Renal arteries: one of the pair of large blood vessels that branch off from the abdominal aorta and enter into each kidney

Renal veins: veins that accompany renal arteries

Renal cortex: the outer portion of the kidney between the renal capsule and the renal medullaMedulla: the innermost

part of the kidney; contains the structures of the nephrons responsible for maintaining the salt and water balance of the bloodRenal sinus: a cavity within the kidney which is occupied by the renal pelvis, renal calyces, blood vessels, nerves and fat

Renal pyramids: the conical tissues composing the medullary substance of the kidney

Renal columns: inward extensions of the cortical substance of the kidney between contiguous renal pyramids

Interlobar arteries: branches of the segmental arteries of the kidney; runs between the renal lobes and give rise to the arcuate arteriesInterlobar veins: veins

that parallel the interlobular arteries; drains the peritubular capillary plexus, and empty into the arcuate veins of the kidney

Interlobular arteries: branches of the interlobar arteries of the kidney passing outward through the cortex and supplying the glomeruli.

Interlobular veins: veins that arise as tributaries of the portal vein between the hepatic lobules

Arcuate arteries: curved arteries of the kidney

Arcuate veins: veins that receive blood from interlobular veins of kidney and rectal

Minor calyx: the cup-shaped dilation of the intrarenal ureter; the space into which a single papilla of a multiple-lobed kidney protrudesMajor calyx: a fusion of

minor calyxes

Renal papilla: The apex of a renal pyramid, projecting into a calyx

Renal pelvis: enlarged upper end of the ureter; shaped somewhat like a funnel that is curved to one side

Hilum: depression on the medial border of the kidney through which pass the segmental renal vessels and renal nerves and where the apex of the renal pelvis occurs

Nephron: functional unit of the kidney, in which waste products are filtered from the blood and urine is produced; consists of a system of tubules in close association with a network of blood vessels

Nephrons Process:

1. The nephron begins at the renal corpuscle, a chamber that contains a capillary network, or the glomerulus. Blood arrives at the glomerulus by the way of an afferent arteriole and departs in an efferent artiole.2. In the renal corpuscle, blood pressure forces fluid and dissolved solutes out of the glomerular capillaries and into the surrounding capsular space. This process is called filtration, which produces a protein-free solution known as a filtrate.

3. From the renal corpuscle, the filtrate enters the renal tubule, which consists of the proximal convoluted tubule (PCT), the loop of Henle, and the distal convoluted tubule (DCT). As the filtrate travels along the tubule, its composition changes, and it is then called tubular fluid.4. Each nephron empties into a collecting duct, the start of the collecting system. The collecting duct leaves the cortex and descends into the medulla, carrying tubular fluid from many nephrons toward a papillary duct that delivers the fluid, now called urine into the calyces on to the pelvis.

Basic Principles of Urine Production

The primary purpose of urine production is to maintain homeostasis by regulating the volume and compositing of the blood. This process involves the excretion of waste products.

• Urea. Urea is the most abundant organic waste.

• Creatinine. Creatinine is generated in skeletal muscle tissue through the breakdown of creatine phosphate, a high-energy compound that plays an important role in muscle contraction.

• Uric acid. Uric acid is produced during the breakdown and recycling of RNA.

Basic Principles of Urine Production (continued)

In the process of doing so, the kidneys ensure that the excreted urine does not contain organic substrates present in blood plasma. To accomplish these goals, the kidneys perform three distinct processes: • Filtration. In filtration,

blood pressure forces water across the filtration membrane in the renal corpuscle. Solute molecules small enough to pass through the membrane are carried into the filtrate by the surrounding molecules.

• Reabsorption. Reabsorption is the removal of water and solute molecules from the filtrate and their reentry into the circulation at the peritubular capillaries.

• Secretion. Secretion is the transport of solutes out of the peritubular capillaries, across the tubular epithelium, and into the filtrate. This process is necessary because filtration does not force all of the dissolved materials out of the blood.

Ureter • Ureters are two uterine tubes that carry urine from the kidneys to the bladder. • Each

ureter is about ten to twelve inches long.• Urine flows down partly by gravity, but mainly by waves of contractions which pass several times per minute through the muscle layers of the urethral walls.

• It enters the bladder through a tunnel in the bladder wall, which is angled to prevent the urine from running back into the ureter when the bladder contracts.

Urinary Bladder • It’s a muscular, distensible sac that stores urine prior to micturition.• The bladder is a hollow and expandable organ located in the pelvic girdle. Although the shape of the bladder is spherical, its shape is altered by the pressures of surrounding organs.

• When it is empty, the inner walls of the bladder form folds. But as the bladder fills with urine, the walls become smoother.

Urethra

• The urethra is a tube that conveys urine from the urinary bladder to the outside of the body. • Its wall is lined with mucous membranes and contains a relatively thick layer of smooth muscle tissue. It also contains numerous mucous glands, called "urethral glands," that secrete mucus into the urethral canal.

How It Works1. Urea is carried in the bloodstream to the kidneys.

2. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.

3. From the kidneys, urine travels down two thin tubes called ureters to the bladder. Muscles in the ureter walls constantly tighten and relax to force urine downward away from the kidneys.

4. The urinary bladder swells into a round shape when it is full and gets smaller when empty.

5. Circular muscles called sphincters help keep urine from leaking. The sphincter muscles close tightly like a rubber band around the opening of the bladder into the urethra.6. Nerves in the bladder tell you when it is time to urinate. The

sensation to urinate becomes stronger as the bladder continues to fill and reaches its limit. At that point, nerves from the bladder send a message to the brain that the bladder is full, and the urge to empty the bladder intensifies.

Cystinuria• Basic Description• Symptoms• Cause• Diagnosis• Prognosis• Treatment• Prevention

Basic Description

• Cystinuria is an inherited genetic disorder of the transport of an amino acid called cystine resulting in cystinuria, an excess of cystine in the urine, and the formation of cystine stones.• Cystinuria is one of the

more common genetic disorders. Its overall prevalence is about 1 in 7,000 in the population. Cystinuria is the most common defect known in the transport of an amino acid.

Symptoms • Renal colic is an intense, cramping pain due to stones in the urinary tract.

• Pain usually located in the flank or the side of the mid back and radiates to the groin, due to kidney pain.

• Sweating, nausea, and vomiting are common.

• Blood may be visible in the urine because the stone has irritated the ureter. Sometimes, if the stone causes complete obstruction, no blood may be found in the urine because it cannot get past the stone.

CausesThere is no consensus as to why kidney stones form.

• Heredity: The predisposition to high levels of calcium in the urine may be passed on from generation to generation. Some rare hereditary diseases also predispose some people to form kidney stones.

• Geographical Region: There are regional "stone belts," of increased risk of stone formation. The hot climate and poor fluid intake may cause people to be relatively dehydrated, with their urine becoming more concentrated and allowing chemicals to come in closer contact to form the nidus.

• Diet: Diet may or may not be an issue. If a person is susceptible to forming stones, then foods high in calcium may increase the risk. If not diet will not change that risk.

Diagnosis• A urinalysis may detect blood in the urine. It is also done to look for evidence of infection, a complication of kidney stone disease.

• Computerized tomography (CT) scanning of the abdomen without oral or intravenous contrast dye is the most commonly used diagnostic test.

• Ultrasound is another way of looking for kidney stones and obstruction.

• Patients who already have the diagnosis of a kidney stone, plain abdominal X-rays may be used to track its movement down the ureter toward the bladder.

Prognosis

• Cystinuria is a chronic, lifelong condition. Stones commonly return. However, the condition rarely results in kidney failure, and it does not affect other organs.

“As many as 50% of patients who have had surgical treatment for a kidney stone will have another stone within five years if no medicines are used to treat this condition.”

— Dominic De Bellis, PhD

Treatment • Ketorolac (Toradol), an injectable anti-inflammatory drug, and narcotics may be used for pain control, with the goal being to relieve suffering and not necessarily to make the patient pain free.

• If the stone is high up in the ureter, near the kidney, and is large, using lithotripsy, or shock wave therapy (EWSL), can be considered to break the stone up into fragments to allow the smaller pieces to pass into the bladder.

• Ureteroscopy is when instruments are threaded into the ureter and a stent, a thin hollow tube, is placed through the urethra, past the bladder, and into the ureter to bypass the obstructing stone.

Prevention • The risk of forming a stone can be minimized by avoiding dehydration. Keeping the urine dilute will not allow the chemical crystals to come out of solution and form the nidus of a stone. • Making certain

that the urine remains clear and not concentrated will help minimize stone formation.

• Medication may be prescribed for certain types of stones, and compliance with taking the medication is a must to reduce the risk of future episodes.

Bibliography • Martini, Frederic H., and Bartholomew, Edwin F.. Essentials of Anatomy & Physiology. 4th Ed. San Fransico, CA: Pearson Education, Inc., 2007. • Campbell, Neil A., Reece, Jane B.. AP* Edition Biology. 8th Ed. San Fransico, CA: Pearson Benjamin Cummings, 2008.

• “Your Urinary System and How It Works”. Niddk. August 2007. ‹http://www.aresearchguide.com/12biblio.html#c›

• “Uriniary System”. Innerbody. 1993-2010. ‹http://www.innerbody.com/image/urinov.html ›

• “Cystinuria”. Medicinenet. 1996-2010.‹ http://www.medicinenet.com/cystinuria/article.htm› • “Cystinura”. Wrong Diagnosis. 2010.‹http://www.wrongdiagnosis.com/c/cystinuria/intro.htm›

The End

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