1、1Urinary System Professional english of medicine2The Urinary System is a group of organs in the body concerned with filtering out excess fluid and other substances from the bloodstream.The principal function of the urinary system is to maintain the volume and composition of body fluids within normal
2、 limits.3One aspect of this function is to rid the body of waste products that accumulate as a result of cellular metabolism.4Other aspects of its function include regulating the concentrations of various electrolytes in the body fluids and maintaining normal pH of the blood.The urinary organs inclu
3、de the kidneys,ureters,bladder,and urethra.561.Functions of the Urinary System One of the major functions of the urinary system is the process of excretion,which is the process of eliminating waste products of metabolism and other materials that are of no use.7The urinary system maintains an appropr
4、iate fluid volume by regulating the amount of water that is excreted in the urine.1.Functions of the Urinary System 8Other aspects of its function include regulating the concentrations of various electrolytes in the body fluids and maintaining normal pH of the blood.9The kidneys are the most importa
5、nt excretory organ.The primary function of the kidneys are to maintain a stable internal environment(homeostasis)for optimal cell and tissue metabolism.10They do this by separating urea,mineral salts,toxins,and other waste products from the blood.They also do the job of conserving water,salts,and el
6、ectrolytes.11At least one kidney must function properly for life to be maintained.Six important roles of the kidneys are:12(1)Regulation of plasma ionic composition.Ions such as sodium,potassium,calcium,magnesium,chloride,bicarbonate,and phosphates are regulated by the amount that the kidney excrete
7、s.13(2)Regulation of plasma osmolarity.The kidneys regulate osmolarity because they have direct control over how many ions and how much water a person excretes.14(3)Regulation of plasma volume.The kidneys control plasma volume by controlling how much water a person excretes.The plasma volume has a d
8、irect effect on the total blood volume,which has a direct effect on your blood pressure.Salt(NaCl)will cause osmosis to happen;the diffusion of water into the blood.15(4)Regulation of plasma hydrogen ion concentration(pH).The kidneys partner up with the lungs and they together control the pH.16The k
9、idneys have a major role because they control the amount of bicarbonate excreted or held onto.The kidneys help maintain the blood pH mainly by excreting hydrogen ions and reabsorbing bicarbonate ions as needed.17(5)Removal of metabolic waste products and foreign substances from the plasma.One of the
10、 most important things the kidneys excrete is nitrogenous waste.18 About 50%of nitrogenous waste is urea,a by-product which is produced when protein is broken down by the body.Some of it is from ammonia,which is very toxic.The liver,however,quickly converts it to urea,a less harmful waste.Other nitr
11、ogenous wastes include uric acid and creatinine.19 (6)Secretion of Hormones.Renin is released by the kidneys.Renin leads to the secretion of aldosterone which is released from the adrenal cortex.Aldosterone promotes the kidneys to reabsorb the sodium ions.20 The kidneys also secrete erythropoietin,w
12、hich stimulates red blood cell production.The Vitamin D from the skin is also activated with help from the kidneys.212.Organs in the Urinary System2.1 KidneysThe kidneys are a pair of bean shaped,reddish brown organs about the size of your fist.It measures 10-12 cm long.22They are covered by the ren
13、al capsule,which is a tough capsule of fibrous connective tissue.Adhering to the surface of each kidney is two layers of fat to help cushion them.23There is a concaved side of the kidney that has a depression where a renal artery enters,and a renal vein and a ureter exit the kidney.The kidneys are l
14、ocated at the rear wall of the abdominal cavity just above the waistline,and are protected by the ribcage.They lie behind the peritoneum.24There are three major regions of the kidney,cortex,medulla and the renal pelvis.The outer,granulated layer is the renal cortex.The cortex stretches down in betwe
15、en a radially striated inner layer.25The inner radially striated layer is the renal medulla.This contains pyramid shaped tissue called the renal pyramids,separated by renal columns.FIGURE 2.Longitudinal section through the kidney showing its internal structure,and an enlarged diagram of a nephron.Th
16、ere are more than 1 million nephrons in each kidney.27Urine is formed in three steps:Filtration,Reabsorption,and Secretion.28(1).Filtration.Blood enters the afferent arteriole and flows into the glomerulus.Filterable blood components move toward the inside of the glomerulus while non-filterable bloo
17、d components bypass the filtration process by exiting through the efferent arteriole.29A few of the filterable blood components are water,nitrogenous waste,nutrients and salts.Nonfilterable blood components include formed elements such as blood cells and platelets along with plasma proteins.30The gl
18、omerular filtrate is not the same consistency as urine,as much of it is reabsorbed into the blood as the filtrate passes through the tubules of the nephron.FIGURE 3.A nephron and its blood supply.32(2)ReabsorptionWithin the peritubular capillary network,molecules and ions are reabsorbed back into th
19、e blood.Sodium chloride reabsorbed into the system increases the osmolarity of blood in comparison to the glomerular filtrate.33This reabsorption process allows water to pass from the glomerular filtrate back into the circulatory system.34Glucose and various amino acids also are reabsorbed into the
20、circulatory system.These nutrients have carrier molecules that claim the glomerular molecule and release it back into the circulatory system.35If all of the carrier molecules are used up,excess glucose or amino acids are set free into the urine.36(3)Secretion Some substances are removed from blood t
21、hrough the peritubular capillary network into the distal convoluted tubule or collecting duct.These substances are hydrogen ions,creatinine,and drugs.372.2 UretersThe ureters are two tubes that drain urine from the kidneys to the bladder.Each ureter is a muscular tube about 25 cm long.Muscles in the
22、 walls of the ureters send the urine in small spurts into the bladder.38After the urine enters the bladder from the ureters,small folds in the bladder mucosa act like valves preventing backward flow of the urine.2.2 Ureters392.3 Urinary BladderThe urinary bladder is a hollow,muscular and distensible
23、 or elastic organ that sits on the pelvic floor.distensible：capable of being distended;able to stretch and expand 402.3 Urinary BladderThe urinary bladder can hold approximately 500 to 530 ml of urine,however the desire to micturate is usually experienced when it contains about 150 to 200 ml.412.3 U
24、rinary BladderWhen the bladder fills with urine,stretch receptors send nerve impulses to the spinal cord,which then sends a reflex nerve impulse back to the sphincter at the neck of the bladder,causing it to relax and allow the flow of urine into the urethra.422.3 Urinary Bladder The ureters enter t
25、he bladder diagonally from its dorsolateral floor in an area called the trigone.The trigone is a triangular shaped area on the posteroinferior wall of the bladder.FIGURE 4.Interior of the urinary bladder,shown in a male subject.44The urethra exits at the lowest point of the triangle of the trigone.T
26、he urine in the bladder also helps regulate body temperature.2.3 Urinary Bladder 452.4 UrethraThe urethra is a muscular tube that connects the bladder with the outside of the body.The function of the urethra is to remove urine from the body.46The urethral sphincter is a collective name for the muscl
27、es used to control the flow of urine from the urinary bladder.These muscles surround the urethra,so that when they contract,the urethra is closed.2.4 Urethra473.DiureticsA diuretic is any drug that elevates the rate of bodily urine excretion(diuresis).Diuretics also decrease the extracellular fluid(
28、ECF)volume,and are primarily used to produce a negative extracellular fluid balance.483.DiureticsCaffeine and alcohol are all weak diuretics.In medicine,diuretics are used to treat heart failure,liver cirrhosis,hypertension and certain kidney diseases.493.DiureticsDiuretics alleviate the symptoms of
29、 these diseases by causing sodium and water loss through the urine.50As urine is produced by the kidney,sodium and water which cause edema related to the disease move into the blood to replace the volume lost as urine,thereby reducing the pathological edema.51The antihypertensive actions of some diu
30、retics(thiazides and loop diuretics in particular)are independent of their diuretic effect.52That is,the reduction in blood pressure is not due to decreased blood volume resulting from increased urine production,but occurs through other mechanisms and at lower doses than that required to produce diu
31、resis.53Indapamide has a larger therapeutic window for hypertension(without pronounced diuresis)than most other diuretics.54 Chemically,diuretics are a diverse group of compounds that either stimulate or inhibit various hormones that naturally occur in the body to regulate urine production by the ki
32、dneys.Alcohol produces diuresis through modulation of the vasopressin system.Roots for the KidneyROOT MEANING ren/o kidney nephr/o kidney glomerul/o glomerulus pyel/o renal pelvis Cali-calic-calyx 561.near(para-)the kidney:pararenal2.above(supra-)the kidney:suprarenal3.between the kidneys：interrenal
33、4.around the kidneys:perirenal5.behind(post-)the kidney:postrenalUse the root ren/o to write a word 57Use the root nephr/o to write a word 6.inflammation of the kidney：nephritis7.any disease of the kidney：nephropathy8.softening of the kidney：nephromalacia9.surgical removal of the kidney：nephrectomy1
34、0.study of the kidney：nephrology 58Roots for the Urinary Tract(Except the Kidney)ROOT MEANING ur/o urine,urinary tracturin/o urine ureter/o ureter cyst/o Urinary bladder vesic/o Urinary bladder urethr/o urethra 59Use the root ur/o to write a word 1.radiography of the urinary tract:urography2.a urina
35、ry calculus(stone)：urolith3.study of the urinary tract：urology4.presence of urinary waste products in the blood(-emia)：uremia60Use-uria to write a word 5.presence of proteins in the urine：proteinuria6.lack of urine：anuria7.formation of excess(poly-)urine：polyuria8.painful or difficult urination：dysu
36、ria619.presence of pus in the urine：pyuria10.presence of cells in the urine：cyturia11.presence of blood(hemat/o)in the urine：hematuria12.urination during the night(noct/i)：nocturiaUse-uria to write a word 62write a word13.inflammation of the urethra：urethritis14.a ureteral calculus：ureterolith15.surgical fixation of the urinary bladder：cystopexy 6316.an instrument for examining the inside of the bladder：cystoscope 17.in front of(pre-)the bladder：prevesical write a word
