Urinary system
| Urinary system | |
|---|---|
 1.Human urinary system:2.Kidney,3.Renal pelvis,4.Ureter,5.Urinary bladder,6.Urethra.(Left side withfrontal section) 7.Adrenal gland Vessels:8.Renal arteryandvein,9.Inferior vena cava,10.Abdominal aorta,11.Common iliac arteryandvein Translucent:12.Liver,13.Large intestine,14.Pelvis | |
 | |
| Details | |
| Identifiers | |
| Latin | systema urinarium |
| MeSH | D014551 |
| TA98 | A08.0.00.000 |
| TA2 | 3357 |
| FMA | 7159 |
| Anatomical terminology | |
The humanurinary system,also known as theurinary tractorrenal system,consists of thekidneys,ureters,bladder,and theurethra.The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels ofelectrolytesandmetabolites,and regulateblood pH.The urinary tract is the body's drainage system for the eventual removal of urine.[1]The kidneys have an extensive blood supply via therenal arterieswhich leave the kidneys via therenal vein.Each kidney consists of functional units callednephrons.Followingfiltrationof blood and further processing, wastes (in the form ofurine) exit the kidney via the ureters, tubes made ofsmooth musclefibres that propel urine towards the urinary bladder, where it is stored and subsequently expelled through theurethraduringurination.The female and male urinary system are very similar, differing only in the length of the urethra.[2]
800–2,000 milliliters (mL) of urine are normally produced every day in a healthy human. This amount varies according to fluid intake and kidney function.
Structure
[edit] | This section'sfactual accuracy isdisputed.(March 2024) |
The urinary system refers to the structures that produce and transport urine to the point of excretion. In the human urinary system there are two kidneys that are located between the dorsal body wall and parietal peritoneum on both the left and right sides.
The formation of urine begins within the functional unit of the kidney, the nephrons. Urine then flows through the nephrons, through a system of converging tubules called collecting ducts. These collecting ducts then join together to form theminor calyces,followed by the major calyces that ultimately join the renal pelvis. From here, urine continues its flow from the renal pelvis into the ureter, transporting urine into the urinary bladder. The anatomy of the human urinary system differs between males and females at the level of the urinary bladder. In males, the urethra begins at the internal urethral orifice in the trigone of the bladder, continues through the external urethral orifice, and then becomes the prostatic, membranous, bulbar, and penile urethra. Urine exits the male urethra through theurinary meatusin theglans penis.The female urethra is much shorter, beginning at the bladder neck and terminating in thevulval vestibule.
Development
[edit]Microanatomy
[edit]Under microscopy, the urinary system is covered in a unique lining calledurothelium,a type oftransitional epithelium.Unlike theepitheliallining of most organs, transitional epithelium can flatten and distend. Urothelium covers most of the urinary system, including the renal pelvis, ureters, and bladder.
Function
[edit]The main functions of the urinary system and its components are to:
- Regulateblood volumeand composition (e.g.sodium,potassiumandcalcium)
- Regulateblood pressure.
- RegulatepHhomeostasisof the blood.
- Contributes to the production of red blood cells by thekidney.
- Helps synthesizecalcitriol(the active form ofVitamin D).
- Stores waste products (mainlyureaanduric acid) before it and other products are removed from the body.
Urine formation
[edit]Average urine production in adult humans is about 1–2litres(L) per day, depending on state of hydration, activity level, environmental factors, weight, and the individual's health. Producing too much or too little urine requires medical attention.Polyuriais a condition of excessive urine production (> 2.5 L/day). Conditions involving low output of urine areoliguria(< 400 mL/day) andanuria(< 100 mL/day).
The first step in urine formation is the filtration of blood in the kidneys. In a healthy human, the kidney receives between 12 and 30% ofcardiac output,but it averages about 20% or about 1.25 L/min.
The basic structural and functional unit of the kidney is thenephron.Its chief function is to regulate theconcentrationofwaterand soluble substances likesodiumby filtering theblood,reabsorbing what is needed and excreting the rest asurine.
In the first part of the nephron,Bowman's capsulefilters blood from thecirculatory systeminto the tubules. Hydrostatic and osmotic pressure gradients facilitate filtration across a semipermeable membrane. The filtrate includes water, small molecules, and ions that easily pass through the filtration membrane. However, larger molecules such asproteinsandblood cellsare prevented from passing through the filtration membrane. The amount of filtrate produced every minute is called theglomerular filtration rateor GFR and amounts to 180 litres per day. About 99% of this filtrate is reabsorbed as it passes through the nephron and the remaining 1% becomes urine.
The urinary system is regulated by theendocrine systembyhormonessuch asantidiuretic hormone,aldosterone,andparathyroid hormone.[3]
Regulation of concentration and volume
[edit]The urinary system is under influence of thecirculatory system,nervous system,andendocrine system.
Aldosteroneplays a central role in regulating blood pressure through its effects on the kidney. It acts on the distal tubules and collecting ducts of the nephron and increases reabsorption of sodium from the glomerular filtrate. Reabsorption of sodium results in retention of water, which increases blood pressure and blood volume. Antidiuretic hormone (ADH), is aneurohypophysial hormonefound in mostmammals.Its two primary functions are to retain water in the body andvasoconstriction.Vasopressin regulates the body'sretention of waterby increasing water reabsorption in the collecting ducts of the kidney nephron.[4]Vasopressin increases water permeability of the kidney's collecting duct and distal convoluted tubule by inducing translocation of aquaporin-CD water channels in the kidney nephron collecting duct plasma membrane.[5]
Urination
[edit]Urination, also sometimes referred to as micturition, is the ejection ofurinefrom theurinary bladderto the outside of the body. Urine is ejected through theurethrafrom thepenisorvulvainplacental mammalsand through thecloacain othervertebrates.In healthy humans (andmany other animals), the process of urination is under voluntary control. In infants, some elderly individuals, and those with neurological injury, urination may occur as an involuntaryreflex.Physiologically, micturition involves coordination between thecentral,autonomic,andsomatic nervous systems.Brain centers that regulate urination include thepontine micturition center,periaqueductal gray,and thecerebral cortex.
Clinical significance
[edit]Urologic diseasecan involve congenital or acquired dysfunction of the urinary system. As an example,urinary tract obstructionis a urologic disease that can causeurinary retention.
Diseases of the kidney tissue are normally treated bynephrologists,while diseases of the urinary tract are treated byurologists.Gynecologistsmay also treat female urinary incontinence.
Diseases of other bodily systems also have a direct effect on urogenital function. For instance, it has been shown thatproteinreleased by the kidneys indiabetes mellitussensitizes the kidney to the damaging effects ofhypertension.[6]
Diabetesalso can have a direct effect inurinationdue toperipheral neuropathies,which occur in some individuals with poorly controlled blood sugar levels.[7]
Urinary incontinencecan result from a weakening of thepelvic floormuscles caused by factors such aspregnancy,childbirth,aging,and beingoverweight.Findings recent systematic reviews demonstrate that behavioral therapy generally results in improved urinary incontinence outcomes, especially forstressandurgeUI, than medications alone.[8][9]Pelvic floor exercises known asKegel exercisescan help in this condition by strengthening the pelvic floor. There can also be underlying medical reasons for urinary incontinence which are often treatable. In children, the condition is calledenuresis.
Some cancers also target the urinary system, includingbladder cancer,kidney cancer,ureteral cancer,andurethral cancer.Due to the role and location of these organs, treatment is often complicated.[citation needed]
History
[edit]Kidney stoneshave been identified and recorded about as long as written historical records exist.[10]The urinary tract including the ureters, as well as their function to drain urine from the kidneys, has been described byGalenin the second century AD.[11]
The first to examine the ureter through an internal approach, called ureteroscopy, rather than surgery wasHampton Youngin 1929.[10]This was improved on byVF Marshallwho is the first published use of a flexibleendoscopebased onfiber optics,which occurred in 1964.[10]The insertion of a drainage tube into therenal pelvis,bypassing the ureters and urinary tract, callednephrostomy,was first described in 1941. Such an approach differed greatly from theopen surgicalapproaches within the urinary system employed during the preceding two millennia.[10]
See also
[edit]References
[edit]- ^"The Urinary Tract & How It Works | NIDDK".National Institute of Diabetes and Digestive and Kidney Diseases.
- ^C. Dugdale, David (16 September 2011)."Female urinary tract".MedLine Plus Medical Encyclopedia.
- ^Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993).Human Biology and Health.Englewood Cliffs, New Jersey, USA: Prentice Hall.ISBN0-13-981176-1.
- ^Caldwell HK, Young WS III, Lajtha A, Lim R (2006)."Oxytocin and Vasopressin: Genetics and Behavioral Implications"(PDF).Handbook of Neurochemistry and Molecular Neurobiology: Neuroactive Proteins and Peptides(3rd ed.). Berlin: Springer. pp. 573–607.ISBN0-387-30348-0.
- ^Nielsen S, Chou CL, Marples D, Christensen EI, Kishore BK, Knepper MA (February 1995)."Vasopressin increases water permeability of kidney collecting duct by inducing translocation of aquaporin-CD water channels to plasma membrane".Proc. Natl. Acad. Sci. U.S.A.92(4): 1013–7.Bibcode:1995PNAS...92.1013N.doi:10.1073/pnas.92.4.1013.PMC42627.PMID7532304.
- ^Baba, T; Murabayashi, S; Tomiyama, T; Takebe, K (1990)."Uncontrolled hypertension is associated with a rapid progression of nephropathy in type 2 diabetic patients with proteinuria and preserved renal function".The Tohoku Journal of Experimental Medicine.161(4): 311–8.doi:10.1620/tjem.161.311.PMID2256104.
- ^"Peripheral Neuropathy".Patient UK.Retrieved2014-03-20.
- ^Balk, Ethan; Adam, Gaelen P.; Kimmel, Hannah; Rofeberg, Valerie; Saeed, Iman; Jeppson, Peter; Trikalinos, Thomas (2018-08-08)."Nonsurgical Treatments for Urinary Incontinence in Women: A Systematic Review Update".doi:10.23970/ahrqepccer212(inactive 2024-04-03).S2CID80659370.
{{cite journal}}:Cite journal requires|journal=(help)CS1 maint: DOI inactive as of April 2024 (link) - ^Balk, Ethan M.; Rofeberg, Valerie N.; Adam, Gaelen P.; Kimmel, Hannah J.; Trikalinos, Thomas A.; Jeppson, Peter C. (2019-04-02)."Pharmacologic and Nonpharmacologic Treatments for Urinary Incontinence in Women: A Systematic Review and Network Meta-analysis of Clinical Outcomes".Annals of Internal Medicine.170(7): 465–479.doi:10.7326/M18-3227.ISSN0003-4819.PMID30884526.S2CID83458685.
- ^abcdTefekli, Ahmet; Cezayirli, Fatin (2013)."The History of Urinary Stones: In Parallel with Civilization".The Scientific World Journal.2013:423964.doi:10.1155/2013/423964.PMC3856162.PMID24348156.
- ^Nahon, I; Waddington, G; Dorey, G; Adams, R (2011). "The history of urologic surgery: from reeds to robotics".Urologic Nursing.31(3): 173–80.doi:10.7257/1053-816X.2011.31.3.173.PMID21805756.
External links
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