# Urinary system

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Anatomical system consisting of the kidneys, ureters, urinary bladder, and the urethra

Urinary system 1. Human urinary system: 2. Kidney, 3. Renal pelvis, 4. Ureter, 5. Urinary bladder, 6. Urethra. (Left side with frontal section) 7. Adrenal gland Vessels: 8. Renal artery and vein, 9. Inferior vena cava, 10. Abdominal aorta, 11. Common iliac artery and vein Translucent: 12. Liver, 13. Large intestine, 14. Pelvis Urinary system in the male. Urine flows from the kidneys via the ureters into the bladder where it is stored until it exits the body through the urethra (longer in males, shorter in females) during urination Details Identifiers Latin systema urinarium MeSH D014551 TA98 A08.0.00.000 TA2 3357 FMA 7159 Anatomical terminology [edit on Wikidata]

The **urinary system**, also known as the **urinary tract** or **renal system**, is a part of the [excretory system](/source/Excretory_system) of [vertebrates](/source/Vertebrate). In humans and [placental mammals](/source/Placentalia), it consists of the [kidneys](/source/Kidney_(vertebrates)), [ureters](/source/Ureters), [bladder](/source/Urinary_bladder), and the [urethra](/source/Urethra). The purpose of the urinary system is to eliminate [urine](/source/Urine) from the body, regulate blood volume and blood pressure, control levels of [electrolytes](/source/Electrolyte) and [metabolites](/source/Metabolite), and regulate [blood pH](/source/Acid%E2%80%93base_homeostasis).[1] The kidneys have an extensive blood supply via the [renal arteries](/source/Renal_artery) which leave the kidneys via the [renal vein](/source/Renal_vein). Each kidney consists of functional units called [nephrons](/source/Nephrons). Following [filtration](/source/Filtration) of blood and further processing, the [ureters](/source/Ureter) transport urine from the kidneys into the [urinary bladder](/source/Urinary_bladder). The female and male urinary system are very similar, differing only in the length of the [urethra](/source/Urethra), which transports urine from the bladder through the [penis](/source/Penis) or [vulva](/source/Vulva) during [urination](/source/Urination).[2]

Healthy humans normally produce 800–2,000 milliliters (mL) of urine every day. This amount varies according to fluid intake and kidney function.

## Structure

3D model of urinary system

The urinary system refers to the structures that produce and excrete urine. 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, which then join to form the [minor calyces](/source/Renal_calyx), followed by the major calyces that ultimately join the renal pelvis, followed by the ureters, which transport urine into the urinary bladder. The anatomy of the human urinary bladder and urethra differs between males and females. In males, the urethra begins at the internal urethral orifice in the trigone of the bladder, and then becomes the prostatic, membranous, bulbar, and penile urethra, and terminates at the [urinary meatus](/source/Urinary_meatus) in the [glans penis](/source/Glans_penis). The female urethra is much shorter, beginning at the bladder neck and terminating in the [vulval vestibule](/source/Vulval_vestibule).

### Development

Main article: [Development of the urinary system](/source/Development_of_the_urinary_system)

### Microanatomy

See also: [Urothelium](/source/Urothelium)

Under microscopy, the urinary system is covered in a unique lining called [urothelium](/source/Urothelium), a type of [transitional epithelium](/source/Transitional_epithelium). Unlike the [epithelial](/source/Epithelium) lining of most organs, transitional epithelium can flatten and distend. Urothelium covers most of the urinary system, including the renal pelvis, ureters, and bladder.

## Function

The main functions of the urinary system and its components are to:

- Regulate [blood volume](/source/Blood_volume) and composition (e.g. [sodium](/source/Sodium), [potassium](/source/Potassium) and [calcium](/source/Calcium))

- Regulate [blood pressure](/source/Blood_pressure).

- Regulate [pH](/source/PH) [homeostasis](/source/Homeostasis) of the blood.

- Contributes to the production of red blood cells by the [kidney](/source/Kidney).

- Helps synthesize [calcitriol](/source/Calcitriol) (the active form of [Vitamin D](/source/Vitamin_D)).

- Stores waste products (mainly [urea](/source/Urea) and [uric acid](/source/Uric_acid)) before it and other products are removed from the body.

### Urine formation

Average urine production in adult humans is about 1–2 [litres](/source/Litres) (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. [Polyuria](/source/Polyuria) is a condition of excessive urine production (> 2.5 L/day). Conditions involving low output of urine are [oliguria](/source/Oliguria) (< 400 mL/day) and [anuria](/source/Anuria) (< 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% of [cardiac output](/source/Cardiac_output), but it averages about 20% or about 1.25 L/min.

The basic structural and functional unit of the kidney is the [nephron](/source/Nephron). Its chief function is to regulate the [concentration](/source/Concentration) of [water](/source/Water) and soluble substances like [sodium](/source/Sodium_salt) by filtering the [blood](/source/Blood), reabsorbing what is needed and excreting the rest as [urine](/source/Urine).

In the first part of the nephron, [Bowman's capsule](/source/Bowman's_capsule) filters blood from the [circulatory system](/source/Circulatory_system) into 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 as [proteins](/source/Proteins) and [blood cells](/source/Blood_cell) are prevented from passing through the filtration membrane. The amount of filtrate produced every minute is called the [glomerular filtration rate](/source/Glomerular_filtration_rate) or 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 the [endocrine system](/source/Endocrine_system) by [hormones](/source/Hormone) such as [antidiuretic hormone](/source/Antidiuretic_hormone), [aldosterone](/source/Aldosterone), and [parathyroid hormone](/source/Parathyroid_hormone).[3]

#### Regulation of concentration and volume

The urinary system is under influence of the [circulatory system](/source/Circulatory_system), [nervous system](/source/Nervous_system), and [endocrine system](/source/Endocrine_system).

[Aldosterone](/source/Aldosterone) plays 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 a [neurohypophysial hormone](/source/Neurohypophysial_hormone) found in most [mammals](/source/Mammals). Its two primary functions are to retain water in the body and [vasoconstriction](/source/Vasoconstriction). Vasopressin regulates the body's [retention of water](/source/Water_retention_(medicine)) by 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

Main article: [Urination](/source/Urination)

Urination, also sometimes referred to as micturition, is the ejection of [urine](/source/Urine) from the [urinary bladder](/source/Urinary_bladder) to the outside of the body. Urine is ejected through the [urethra](/source/Urethra) from the [penis](/source/Penis) or [vulva](/source/Vulva) in [placental mammals](/source/Placentalia) and through the [cloaca](/source/Cloaca) in other [vertebrates](/source/Vertebrate). In healthy humans (and [many other animals](/source/Urination#Animals)), the process of urination is under voluntary control. In infants, some elderly individuals, and those with neurological injury, urination may occur as an involuntary [reflex](/source/Reflex). Physiologically, micturition involves coordination between the [central](/source/Central_nervous_system), [autonomic](/source/Autonomic_nervous_system), and [somatic nervous systems](/source/Somatic_nervous_system). Brain centers that regulate urination include the [pontine micturition center](/source/Pontine_micturition_center), [periaqueductal gray](/source/Periaqueductal_gray), and the [cerebral cortex](/source/Cerebral_cortex).

## Clinical significance

Main article: [Urologic disease](/source/Urologic_disease)

Further information: [Urinary tract infection](/source/Urinary_tract_infection)

[Urologic disease](/source/Urologic_disease) can involve congenital or acquired dysfunction of the urinary system. As an example, [urinary tract obstruction](/source/Urinary_tract_obstruction) is a urologic disease that can cause [urinary retention](/source/Urinary_retention).

Diseases of the kidney tissue are normally treated by [nephrologists](/source/Nephrologist), while diseases of the urinary tract are treated by [urologists](/source/Urologist). [Gynecologists](/source/Gynecology) may also treat female urinary incontinence.

Diseases of other bodily systems also have a direct effect on urogenital function. For instance, it has been shown that [protein](/source/Protein) released by the kidneys in [diabetes mellitus](/source/Diabetes_mellitus) sensitizes the kidney to the damaging effects of [hypertension](/source/Hypertension).[6]

[Diabetes](/source/Diabetes) also can have a direct effect in [urination](/source/Urination) due to [peripheral neuropathies](/source/Peripheral_neuropathy), which occur in some individuals with poorly controlled blood sugar levels.[7]

[Urinary incontinence](/source/Urinary_incontinence) can result from a weakening of the [pelvic floor](/source/Pelvic_floor) muscles caused by factors such as [pregnancy](/source/Pregnancy), [childbirth](/source/Childbirth), [aging](/source/Ageing), and being [overweight](/source/Overweight). Findings recent systematic reviews demonstrate that behavioral therapy generally results in improved urinary incontinence outcomes, especially for [stress](/source/Stress_incontinence) and [urge](/source/Urge_incontinence) UI, than medications alone.[8][9] Pelvic floor exercises known as [Kegel exercises](/source/Kegel_exercise) can 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 called [enuresis](/source/Enuresis).

Some cancers also target the urinary system, including [bladder cancer](/source/Bladder_cancer), [kidney cancer](/source/Kidney_cancer), [ureteral cancer](/source/Ureteral_cancer), and [urethral cancer](/source/Urethral_cancer). Due to the role and location of these organs, treatment is often complicated.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

## History

[Kidney stones](/source/Kidney_stones) have 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 by [Galen](/source/Galen) in the second century AD.[11]

The first to examine the ureter through an internal approach, called ureteroscopy, rather than surgery was [Hampton Young](https://en.wikipedia.org/w/index.php?title=Hampton_Young&action=edit&redlink=1) in 1929.[10] This was improved on by [VF Marshall](https://en.wikipedia.org/w/index.php?title=VF_Marshall&action=edit&redlink=1) who is the first published use of a flexible [endoscope](/source/Endoscope) based on [fiber optics](/source/Fiber_optics), which occurred in 1964.[10] The insertion of a drainage tube into the [renal pelvis](/source/Renal_pelvis), bypassing the ureters and urinary tract, called [nephrostomy](/source/Nephrostomy), was first described in 1941. Such an approach differed greatly from the [open surgical](/source/Open_surgery) approaches within the urinary system employed during the preceding two millennia.[10]

## See also

- [Excretory system](/source/Excretory_system)

- [Major systems of the human body](/source/Major_systems_of_the_human_body)

## References

1. **[^](#cite_ref-NIH_1-0)** ["The Urinary Tract & How It Works | NIDDK"](https://www.niddk.nih.gov/health-information/urologic-diseases/urinary-tract-how-it-works). *National Institute of Diabetes and Digestive and Kidney Diseases*.

1. **[^](#cite_ref-2)** C. Dugdale, David (16 September 2011). ["Female urinary tract"](https://www.medlineplus.gov/ency/imagepages/1122.htm). *MedLine Plus Medical Encyclopedia*.

1. **[^](#cite_ref-3)** Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993). [*Human Biology and Health*](https://archive.org/details/humanbiologyheal00scho). Englewood Cliffs, New Jersey, USA: Prentice Hall. [ISBN](/source/ISBN_(identifier)) [0-13-981176-1](https://en.wikipedia.org/wiki/Special:BookSources/0-13-981176-1).

1. **[^](#cite_ref-isbn0-387-30348-0_4-0)** Caldwell HK, Young WS III, Lajtha A, Lim R (2006). ["Oxytocin and Vasopressin: Genetics and Behavioral Implications"](https://web.archive.org/web/20110504131252/http://refworks.springer.com/mrw/fileadmin/pdf/Neurochemistry/0387303480C25.PDF) (PDF). *Handbook of Neurochemistry and Molecular Neurobiology: Neuroactive Proteins and Peptides* (3rd ed.). Berlin: Springer. pp. 573–607. [ISBN](/source/ISBN_(identifier)) [0-387-30348-0](https://en.wikipedia.org/wiki/Special:BookSources/0-387-30348-0). Archived from [the original](http://refworks.springer.com/mrw/fileadmin/pdf/Neurochemistry/0387303480C25.PDF) (PDF) on 2011-05-04. Retrieved 2013-03-06.

1. **[^](#cite_ref-pmid7532304_5-0)** 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"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC42627). *Proc. Natl. Acad. Sci. U.S.A*. **92** (4): 1013–7. [Bibcode](/source/Bibcode_(identifier)):[1995PNAS...92.1013N](https://ui.adsabs.harvard.edu/abs/1995PNAS...92.1013N). [doi](/source/Doi_(identifier)):[10.1073/pnas.92.4.1013](https://doi.org/10.1073%2Fpnas.92.4.1013). [PMC](/source/PMC_(identifier)) [42627](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC42627). [PMID](/source/PMID_(identifier)) [7532304](https://pubmed.ncbi.nlm.nih.gov/7532304).

1. **[^](#cite_ref-6)** 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"](https://doi.org/10.1620%2Ftjem.161.311). *The Tohoku Journal of Experimental Medicine*. **161** (4): 311–8. [doi](/source/Doi_(identifier)):[10.1620/tjem.161.311](https://doi.org/10.1620%2Ftjem.161.311). [PMID](/source/PMID_(identifier)) [2256104](https://pubmed.ncbi.nlm.nih.gov/2256104).

1. **[^](#cite_ref-7)** ["Peripheral Neuropathy"](https://www.patient.info/health/peripheral-neuropathy). Patient UK. Retrieved 2014-03-20.

1. **[^](#cite_ref-8)** 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"](https://effectivehealthcare.ahrq.gov/topics/urinary-incontinence-update/final-report-2018). [doi](/source/Doi_(identifier)):[10.23970/ahrqepccer212](https://doi.org/10.23970%2Fahrqepccer212). [S2CID](/source/S2CID_(identifier)) [80659370](https://api.semanticscholar.org/CorpusID:80659370). {{[cite journal](https://en.wikipedia.org/wiki/Template:Cite_journal)}}: Cite journal requires |journal= ([help](https://en.wikipedia.org/wiki/Help:CS1_errors#missing_periodical))[*[permanent dead link](https://en.wikipedia.org/wiki/Wikipedia:Link_rot)*]

1. **[^](#cite_ref-9)** 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"](http://annals.org/article.aspx?doi=10.7326/M18-3227). *Annals of Internal Medicine*. **170** (7): 465–479. [doi](/source/Doi_(identifier)):[10.7326/M18-3227](https://doi.org/10.7326%2FM18-3227). [ISSN](/source/ISSN_(identifier)) [0003-4819](https://search.worldcat.org/issn/0003-4819). [PMID](/source/PMID_(identifier)) [30884526](https://pubmed.ncbi.nlm.nih.gov/30884526). [S2CID](/source/S2CID_(identifier)) [83458685](https://api.semanticscholar.org/CorpusID:83458685).

1. ^ [***a***](#cite_ref-Tefekli2013_10-0) [***b***](#cite_ref-Tefekli2013_10-1) [***c***](#cite_ref-Tefekli2013_10-2) [***d***](#cite_ref-Tefekli2013_10-3) Tefekli, Ahmet; Cezayirli, Fatin (2013). ["The History of Urinary Stones: In Parallel with Civilization"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856162). *The Scientific World Journal*. **2013** 423964. [doi](/source/Doi_(identifier)):[10.1155/2013/423964](https://doi.org/10.1155%2F2013%2F423964). [PMC](/source/PMC_(identifier)) [3856162](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856162). [PMID](/source/PMID_(identifier)) [24348156](https://pubmed.ncbi.nlm.nih.gov/24348156).

1. **[^](#cite_ref-Nahon2011_11-0)** 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](/source/Doi_(identifier)):[10.7257/1053-816X.2011.31.3.173](https://doi.org/10.7257%2F1053-816X.2011.31.3.173). [PMID](/source/PMID_(identifier)) [21805756](https://pubmed.ncbi.nlm.nih.gov/21805756).

## External links

The Wikibook *[Human Physiology](https://en.wikibooks.org/wiki/Human_Physiology)* has a page on the topic of: ***[The Urinary System](https://en.wikibooks.org/wiki/Human_Physiology/The_Urinary_System)***

The Wikibook *[Anatomy and Physiology of Animals](https://en.wikibooks.org/wiki/Anatomy_and_Physiology_of_Animals)* has a page on the topic of: ***[Urinary System](https://en.wikibooks.org/wiki/Anatomy_and_Physiology_of_Animals/Urinary_System)***

[Library resources](https://en.wikipedia.org/wiki/Wikipedia:The_Wikipedia_Library) about
 **Urinary system**

- [Resources in your library](https://ftl.toolforge.org/cgi-bin/ftl?st=wp&su=Urinary+system)

v t e Anatomy of the urinary system Kidneys Layers Fascia Capsule Cortex column Medulla pyramids medullary interstitium Sinus Lobe Cortical lobule Medullary ray Nephron Circulation Arteries Renal artery segmental interlobar arcuate interlobular afferent Veins Renal vein Peritubular capillaries Vasa recta arcuate interlobar efferent Nephron Renal corpuscle Glomerulus Bowman's capsule Glomerular basement membrane Podocyte Filtration slits Mesangium Intraglomerular mesangial cell Renal tubule Proximal convoluted tubule Loop of Henle Descending Thin ascending Thick ascending Distal convoluted tubule Collecting duct system Connecting tubule Papillary duct Tubular fluid Renal papilla Minor calyx Major calyx Renal pelvis Juxtaglomerular apparatus Macula densa Juxtaglomerular cells Mesangium Extraglomerular mesangial cell Ureters Ureteropelvic junction Bladder Circulation Vesical arteries Vesical veins Vaginal artery (female) Detrusor muscle Median umbilical ligament Trigone Urethra Internal urethral orifice Urethral sphincters External male female Internal Male urethra pre-prostatic prostatic intermediate spongy navicular fossa Lacunae of Morgagni urethral gland Urinary meatus

v t e Human systems and organs Musculoskeletal system Skeletal system Bone Carpus Collar bone (clavicle) Thigh bone (femur) Fibula Humerus Mandible Metacarpus Metatarsus Ossicles Patella Phalanges Radius Skull Tarsus Tibia Ulna Rib Vertebra Pelvis Sternum Cartilage Joints Fibrous joint Cartilaginous joint Synovial joint Muscular system Muscle Tendon Diaphragm Circulatory system Cardiovascular system peripheral Artery Vein Lymphatic vessel Heart Lymphatic system primary Bone marrow Thymus secondary Spleen Lymph node CNS equivalent Glymphatic system Nervous system Brain Spinal cord Nerve Sensory system Ear Eye Somatic system Tissue Integumentary system Skin Subcutaneous tissue Breast Mammary gland Haematopoietic and immune systems Myeloid Myeloid immune system Lymphoid Lymphoid immune system Respiratory system Upper Nose Nasopharynx Larynx Lower Trachea Bronchus Lung Digestive system Mouth Salivary gland Tongue Lip Tooth upper GI Oropharynx Laryngopharynx Esophagus Stomach lower GI Small intestine Appendix Colon Rectum Anus accessory Liver Biliary tract Pancreas Urinary system Genitourinary system Kidney Ureter Bladder Urethra Reproductive system Male Scrotum Penis Prostate Testicle Seminal vesicle Female Uterus Vagina Vulva Ovary Placenta Endocrine system Pituitary Pineal Thyroid Parathyroid Adrenal Islets of Langerhans

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