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The urethra is a hollowed tubular organ through which urine is expelled from the body. This structure extends from the bladder to the external opening, allowing urine to be released.
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The ureters are retroperitoneal tubes located on either side of the vertebral column. They are responsible for transporting urine from each kidney to the urinary bladder. These tubes have thick walls and are approximately 25-30 cm long. Their diameter is around 10 mm at the renal pelvis, gradually narrowing to 1 mm as the ureter obliquely enters the posterior bladder wall through the ureteric orifices. The shape of these orifices is slit-like, which helps to prevent urine backflow toward the...
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Anatomy of the Genitourinary System II: Bladder and Urethra01:19

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The lower urinary system consists of the urinary bladder and urethra, which are essential in storing and expelling urine from the body. Together with the internal and external sphincters, these structures work together to regulate urination effectively.Anatomy of the BladderThe urinary bladder is a muscular, stretchable organ behind the pubic bone and in front of the rectum. In females, the bladder is positioned anterior to the vagina and inferior to the uterus, while in males, it is located...
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Urodynamic Studies: Uroflowmetry01:19

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Uroflowmetry is a non-invasive urodynamic test designed to measure various aspects of urination, including volume, flow rate, and the time to void. This test is crucial for diagnosing and assessing conditions such as bladder outlet obstruction, bladder dysfunction, incomplete bladder emptying, incontinence, and urinary tract blockages caused by benign prostatic hyperplasia (BPH) and urethral strictures.Pre-Test Instructions:Before a uroflowmetry test, patients are typically advised to drink...
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Urinary Bladder01:23

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The urinary bladder is a hollow, muscular sac that temporarily stores urine before it is expelled from the body. It can hold approximately 600 mL of urine prior to micturition. The bladder is retroperitoneal and located behind the pubic symphysis in the pelvic floor.
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The upper urinary system comprises two kidneys and two ureters, which are crucial in filtering blood and forming urine.KidneysLocation and Structure:The kidneys are two bean-shaped organs positioned behind the peritoneum on either side of the spine.Kidneys are between the 12th thoracic (T12) and the 3rd lumbar (L3) vertebrae.The position of the liver causes the right kidney to sit slightly lower than the left.Protective Layers:Each kidney is enveloped in a tough, fibrous membrane called the...
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Related Experiment Video

Updated: Jul 30, 2025

Ultrasonography of the Adult Male Urinary Tract for Urinary Functional Testing
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Urinary flow through urethras with a rough lumen.

Patricia J Yang1,2, Tony G Chen1,3, Sarah B Bracher1,4

  • 1George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.

Neurourology and Urodynamics
|May 16, 2023
PubMed
Summary
This summary is machine-generated.

Urethral roughness in mammals can decrease urine flow speed by up to 25%. Optimal urine flow occurs when urethra length is at least 25 times its diameter, with longer lengths not increasing speed.

Keywords:
major lossroughnessurethra

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Area of Science:

  • Biomedical Engineering
  • Urology
  • Comparative Anatomy

Background:

  • Understanding urinary flow dynamics is crucial for diagnosing and treating lower urinary tract symptoms.
  • Previous research has primarily focused on urethral diameter, with less attention paid to lumen roughness and its impact on flow.
  • Mammalian urethras exhibit variations in length and surface topography that may influence urine expulsion efficiency.

Purpose of the Study:

  • To investigate the quantitative impact of urethral lumen roughness and length on urinary flow speed.
  • To develop a predictive mathematical model for urine flow based on urethral geometry.
  • To compare flow dynamics in artificial urethra mimics with natural observations.

Main Methods:

  • Micro-computed tomography scans were used to characterize lumen roughness and dimensions in rabbit, cat, and pig urethras.
  • Three-dimensional-printed urethra mimics with controlled roughness and length were fabricated for flow experiments.
  • A mathematical model was developed to correlate geometric parameters with observed flow speeds.

Main Results:

  • Updated relationships between body mass and urethral length/diameter were established, incorporating new measurements.
  • The interplay between urethral lumen diameter and roughness along the urethra was quantified for multiple species.
  • Flow experiments demonstrated that urethral roughness reduces flow speed by up to 25% compared to smooth surfaces.

Conclusions:

  • Mammalian urethral lumen roughness significantly impedes urine flow speed.
  • Optimal urine flow efficiency is achieved when urethral length is approximately 25 times its diameter.
  • Despite artificial mimics showing faster flow than natural observations, further research is needed to fully elucidate urethral flow resistance mechanisms.