The Urinary System

A+ NURSING TEAM

2012

The Urinary System Chapter 28

Pages 1065-1094

A . P L U S T E A M @ Y A H O O . C O M

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بيننا فيما تشاركية بطريقة المعرفة تيسير في منا واحد كل دور لتفعيل وسيلة إال هى ما

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: إلى يرمي

أفرقة بافي ألدوار تشاركي و استكمالي بدور جنب إل جنبا يعمل طالبي فريق تشكيل ➜ 1

كليتنا اتحاد و وجروبات

لتسهيل هادفة ةيتنظيم بطريقة تعليمية مواد من التمريض طالب يحتاجه ما كل نشر ➜ 2

األكاديمي المستوى رفع ثم ومن

The Urinary System

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Function of urinary system :

** kidney :

1- regulation of blood ionic composition .

2- regulation of blood PH .

3- regulation of blood volume : by conserving or eliminating water in urine .an increase in blood volume increase in blood pressure .

4- regulation of blood pressure : by secreting the enzyme renin, which help activates the rennin-angiotensin-aldesterone pathway .Increased renin causes an increase in blood pressure.

5- maintenance of blood osmolarity : close to 300 milliosmoles per liter (mosm/liter).

6- production of hermones : the kidneys produce two hermones .

*calcitriol , the active form of vitamin D , helps regulate calcium homeostasis.

*erythropoietin stimulates the production of red blood cells.

7- regulation of blood glucose level .

8- excretion of wastes and foreign substances.

**The ureters : Transport urine from the kidneys to the urinary bladder . **The urinary bladder: store urine. **The urethra : discharges urine from the body .

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* we take vitamin D from sunlight Inactive vitamin D in skin 25-hydroxycholecalciferol in liver 1, 25 dihydroxycholecalcferol in kidney by parathyroid hormone . * calcitriol active vitamin D Increase the absorption of Ca++ . * The kidney receive 20-25% of the resting cardiac output via the right and left renal arteries , the blood that goes to the kidneys for renal formation (filtration) .

* The blood flow through both kidneys , is about 1200 ml per minute .

-Internal anatomy of the kidneys : -Renal cortex -Renal medulla . -Renal column . -Renal pyramid in renal medulla -Renal sinus . -Renal papilla . -Renal capsule.

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The nephron : -nephrons are the functional units of the kidneys . -Each nephron consists of two parts : 1. renal corpuscle * glomerulus (capillary net work ) *glomerular (bowman’s) capsule. 2.renal tubule * proximal convoluted tubule. * loop of Henle ( the first part of Henle dips into the renal medulla , where it called the Descending limb of the loop of Henle .It then returns to the cortex as the Ascending limb of the loop of Henle . * distal convoluted tubule . *There are two types of Nephron : 1. Cortical Nephron : _ A bout 80-85 % of the nephrons are cortical nephron . _ They have short loop of Henle . _ There renal corpuscles lie in the outer portion of the renal cortex . *Flow of fluid through a cortical nephron : Glomerular (Bowman’s) capsule proximal convoluted tubule descending limb of the loop of Henle ascending limb of the loop of Henle distal convoluted tubule (drains into collecting duct ). 2. Juxta-medullary Nephron : _ A bout 15-20% of the nephrons are Juxta-medullary nephron . _ Their renal corpuscles lie deep in the cortex , close to medulla , and they have a long loop of Henle that extends into the deepest region of the medulla . _ Enable kidney to secrete very dilute or very concentrated urine.

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* One kidney has about 1 million nephrons , but a much smaller number of collecting ducts and even fewer papillary ducts . *Flow of fluid through A Juxtamedullary nephron : Glomerular (Bowman’s) capsule proximal convoluted tubule descending limb of the loop of Henle thin ascending limb of the loop of Henle thick ascending limp of the loop of Henle distal convoluted tubule (drains into collecting duct).

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-Overview of Renal physiology: To produce urine , nephrons and collecting ducts perform three basic processes :

1. Glomerular Filtration 2. Tubular reabsorption 3. Tubular secretion .

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-Glomerular Filtration : The fluid that enters the capsular space is called the

glomerular filtrate. The daily volume of glomerular filtrate in adults is 150 liter

in females and 180 liter in males . More than 99% of the glomerular filtrate returns to the

bloodstream via tubular reabsorption ,so only 1-2 liters are excreted as urine.

*Filtration membrane: 1- fenestration (pore) of glomerular endothelial cell. 2- the basal lamina 3- slit membrane between pedicles.

*Net filtration pressure: -Glomerular filtration depends on three main pressures. 1. Glomerular blood hydrostatic pressure (GBHP) : * Is the blood pressure in glomerular capillaries. * GBHP is about 55 mmHg . * It promotes filtration .

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2. Capsular hydrostatic pressure (CHP) : * Exerted against the filtration membrane by fluid already in the capsular space and renal tubule . *CHP opposes filtration . * CHP is about 15 mmHg. 3. Blood colloid osmotic pressure (BCOP) : * Apposes filtration . * (BCOP) in glomerular capillaries is 30 mmHg. **Net Filtration Pressure (NFP) = GBHP – CHP – BCOP (NFP)= 55mmHg – 15 mmHg – 30 mmHg =10 mmHg . Thus, a pressure of only 10 mmHg causes a normal amount of blood plasma (minus plasma proteins) to filter from the glomerulus into the capsular space .

Glomerular Filtration Rate :

- The amount of filtrate formed in all the renal corpuscles of both kidneys each minute is the Glomerular Filtration Rate.

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**Three mechanisms control GFR : 1. Renal autoregulation . 2. Neural regulation . 3. Hermonal regulation .

1. Renal Autoregulation of GFR : * Tubuloglomerular feedback , Juxta Medullary apparatu–NaCl sensors An increase in GFR increase NaCl in JGA send impulse to afferent and efferent arteriole constriction decrease in blood flow decrease in GFR . ** Increase in Nitric Oxide (NO) vasodilation increase in GFR. ** Macula densa cells of the juxtaglomerular apparatus provid negative feedback regulation of glomerular filtration rate.

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2. Neural Regulation of GFR : -The kidneys are supplied by Sympathetic Atonomic nervous system vasoconstriction of afferent and efferent arteriole decrease in blood flow decrease in GFR. 3. Hormonal Regulation of GFR : -Two hormones contribute to regulation of GFR . * Angiotensin II : is a very potent vasoconstrictor that narrows both afferent and efferent arterioles and reduces renal blood flow decreasing GFR . * Atrial natriuretic peptide (ANP) : that secrete by cells in the atria of the heart .(ANP) increase the capillary surface area available for filtration increase GFR . *Tubular Reabsorption And Tubular Secretion: -Reabsorption Routes : *Paracellular reabsorption the substance being reabsorbed from the fluid in the tubule lumen between adjacent tubule . *Transcellular reabsorption substance being reabsorbed from the fluid in the tubule lumen through an individual tubule cell. *Apical membrane contacts the tubular fluid and the basolateral membrane contact ininterstitial fluid.

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**Transport Mechanisms :

1. Primary active transport : hydrolysis of ATP , used the pump such as the sodium – potassium pump

2. Secondary active transport :the energy stored in an ion’s electrochemical gradient ,rather than hydrolysis of ATP .

3. Transport maximum . 4. Obligatory water reabsorption : this type of water

reabsorption occurs in the proximal convoluted tubule and the descending limp of the loop of Henle because these segments of the nephron are always permeable to water ,(90% of water).

5. Facultative water reabsorption : reabsorption of the final 10% of the water , occurs mainly in the collecting duct ,regulated by (ADH) .

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* Reabsorption and Secretion in the Proximal Convoluted Tubule : -Obligatory , isotonic, 300milliosmoles per liter. **The reabsorption of the filtered water, Na and K in the proximal convoluted tubule = 65% exception : glucose + amino acid are reabsorbed completely 100% in the proximal convoluted tubule (saturate transport maximam –second active transport). **Secondary transport need ATP not directly . -Na-glucose sympoter( the same direction) in the apical membrane of a cell in the PCT. -In another secondary active transport process, the Na/H antiporters carry filtered Na down its concentration gradient into a PCT cell as H is moved from the cytosol into the lumen , causing Na to be reabsorbed into blood and H to be secreted into tubular fluid. **The enzyme carbonic anhydrase (CA) catalyzes the reaction of CO2 with Water (H2O) to form carbonic acid (H2CO3) which then dissociates into H+ and HCO3- * CO2+H2O H2CO3 H + HCO3- *

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-Passive reabsorption of Cl-,K+,Ca++,Mg++, urea, and water in the second half of the proximal convoluted tubule . Electrochemical gradients promote passive reabsorbtion of solutes via both paracellular and transcellular routes. **Reabsorption in the loop of Henle : *The apical membrane of cells in the thick ascending limb of the loop of henle have Na+,K+,2Cl-symporters. -Na+ actively transported into interstitial fluid -Cl- move through leakage channals are present in the basolateral membrane . -K+ leakage channals are present in the apical membrane. *Although about 15% of the filtered water is reabsorbed in the descending limb of the loop of Henle , little or no water is reabsorbed in the ascending limb.

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**Reabsorption in the Early Distal Convoluted Tubule : -Reabsorption of Na+ and Cl occurs by means of Na+-Cl- symporters in the apical membrane.-The early DCT also is a major site where parathyroid Hermone (PTH) stimulates reabsorption of Ca++. **Reabsorption and secretion in the Late Distal Convoluted Tubule And Collecting Duct : -Recall that two different types of cells * principal cells *and intercalated cells are present at the late or terminal part of the distal convoluted tubule and throughout the collecting duct . -The principal cells reabsorb Na+ by Na+ leakage , and secrete K+ by K+ leakage. -The intercalated cells reabsorb K+ and HCO3- , and secrete H+. **Homonal Regulation Of Tubular Reabsorption and Tubular Secretion :

1. Renin-Angiotensin-Aldesterone System:

-When blood volume and blood pressure decrease the wall of afferent and efferent arterioles are stretched less the juxtaglomerular cell secrete the enzyme Renin into the blood Renin convert Angiotensin to Angiotensin I Angiotensin I convert to Angiotensin II by Angiotensin Converting Enzyme (ACE) which is active form of the hormone Angiotensin II * decrease the glomerular filtration rate by causing vasoconstriction of the afferent arterioles .

* It enhances reabsorption of Na+ , Cl- , and water in the (PCT) by stimulating the activity of Na+/H+ antiporters.

* It stimulates the adrenal cortex to release (Aldosteron) hormone that stimulates the principal cells in the collecting ducts to

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reabsorb more Na+ and Cl- and secrete more K+ Increases blood volume .

2. Antidiuretic Hormon (ADH or Vasopression) :

- Is released by the posterior pituitary.

- Increasing the water permeability of principal cells in the last part of (DCT) and collecting duct.

**Negative Feedback Regulation of Facultative Water Reabsorption by ADH : Some stimulus disrupts homeostasis by

Increasing Osmolarity of plasma and interstitial fluid .

Receptor / Osmoreceptor in hypothalamus .

Input – nerve impulses to control center / hypothalamus and posterior pituitary .

Output – Increase release of ADH Effectors ; *principal cells become more permeable to water , which increase facultative water reabsorption .

Decrease in plasma osmolarity .

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3. Atrial Natriuretic Peptide : Increase in blood volume Promote release of atrial natriuretic peptide (ANP) from the heart It can inhibit reabsorbtion of Na+ and water in the PCT and collecting duct and also it suppresses the secretion of aldosteron and ADH Increase the excretion of Na+ in urine and increase urine output (diuresis) which decreases blood pressure .

2. Parathyroid Hormon : Decrease in level of Ca++ in the blood Stimulates the parathyroid glands to release Parathyroid Hormon (PTH) PTH stimulates cells in the early DCT to reabsorb more Ca++ into the blood . ** Clearance : amount of plasma that gets cleard of substance per minute . - Inulin ( not natural substance ) * free filtered * not reabsorption * and not secreated urine . **Clearance = U * Volume / plasma . - Glucose ( completely reabsorbed or is not filtered ) Clearance of Glucose = zero

- Partially reabsorbed Clearance less than GFR . - K+ (completely secreted ) Clearance more than GFR

*Clearance of Creatinin = ~ GFR - Creatinin used to make kidney test . - Renal plasma flow: the amount of plasma that passes through the kidneys in one minute = 650ml/min. :لالستفسار هذه صفحة الفزيق http://www.facebook.com/aplust.nursing

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