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The urethra is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra connects to the urinary meatus above the vagina, whereas in marsupials, the female's urethra empties into the urogenital sinus.
The urinary bladder, or simply bladder, is a hollow muscular organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In the human the bladder is a hollow distensible organ that sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra. The typical human bladder will hold between 300 and 500 ml before the urge to empty occurs, but can hold considerably more.
The prostate is both an accessory gland of the male reproductive system and a muscle driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physiologically. Anatomically, the prostate is found below the bladder, with the urethra passing through it. It is described in gross anatomy as consisting of lobes, and in microanatomy by zone. It is surrounded by an elastic, fibromuscular capsule and contains glandular tissue as well as connective tissue.
In urinary catheterization a latex, polyurethane, or silicone tube known as a urinary catheter is inserted into the bladder through the urethra. Catheterization allows urine to drain from the bladder for collection. It may also be used to inject liquids used for treatment or diagnosis of bladder conditions. A clinician, often a nurse, usually performs the procedure, but self-catheterization is also possible. A catheter may be in place for long periods of time or removed after each use.
A bladder stone is a stone found in the urinary bladder.
Retrograde ejaculation occurs when semen which would be ejaculated via the urethra is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation, sealing the bladder which besides inhibiting the release of urine also prevents a reflux of seminal fluids into the male bladder during ejaculation. The semen is forced to exit via the urethra, the path of least resistance. When the bladder sphincter does not function properly, retrograde ejaculation may occur. It can also be induced deliberately by a male as a primitive form of male birth control or as part of certain alternative medicine practices. The retrograde-ejaculated semen, which goes into the bladder, is excreted with the next urination.
The seminal vesicles, are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.
The ejaculatory ducts are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra at the seminal colliculus. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the urinary meatus.
Dysuria refers to painful or difficult urination.
Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladder control, mild lower abdominal pain, and a weak urine stream. Those with long-term problems are at risk of urinary tract infections.
Transurethral resection of the prostate is a urological operation. It is used to treat benign prostatic hyperplasia (BPH). As the name indicates, it is performed by visualising the prostate through the urethra and removing tissue by electrocautery or sharp dissection. It has been the standard treatment for BPH for many years, but recently alternative, minimally invasive techniques have become available. This procedure is done with spinal or general anaesthetic. A triple lumen catheter is inserted through the urethra to irrigate and drain the bladder after the surgical procedure is complete. Outcome is considered excellent for 80–90% of BPH patients. The procedure carries minimal risk for erectile dysfunction, moderate risk for bleeding, and a large risk for retrograde ejaculation.
The external sphincter muscle of male urethra, also sphincter urethrae membranaceae, sphincter urethrae externus, surrounds the whole length of the membranous urethra, and is enclosed in the fascia of the urogenital diaphragm.
Radical retropubic prostatectomy is a surgical procedure in which the prostate gland is removed through an incision in the abdomen. It is most often used to treat individuals who have early prostate cancer. Radical retropubic prostatectomy can be performed under general, spinal, or epidural anesthesia and requires blood transfusion less than one-fifth of the time. Radical retropubic prostatectomy is associated with complications such as urinary incontinence and impotence, but these outcomes are related to a combination of individual patient anatomy, surgical technique, and the experience and skill of the surgeon.
Posterior urethral valve (PUV) disorder is an obstructive developmental anomaly in the urethra and genitourinary system of male newborns. A posterior urethral valve is an obstructing membrane in the posterior male urethra as a result of abnormal in utero development. It is the most common cause of bladder outlet obstruction in male newborns. The disorder varies in degree, with mild cases presenting late due to milder symptoms. More severe cases can have renal and respiratory failure from lung underdevelopment as result of low amniotic fluid volumes, requiring intensive care and close monitoring. It occurs in about one in 8,000 babies.
The prostatic urethra, the widest and most dilatable part of the urethra canal, is about 3 cm long.
The membranous urethra or intermediate part of male urethra is the shortest, least dilatable, and, with the exception of the urinary meatus, the narrowest part of the urethra.
The urethral crest is an anatomical feature present in the urinary system of both males and females.
The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.
If medical treatment is not effective, surgery may need to be performed for benign prostatic hyperplasia.
The monotremes represent the order of extant mammals most distantly related to humans. The platypus is indigenous to eastern Australia; the short-beaked echidna is indigenous to Australia and Papua New Guinea; whereas the long-beaked echidna is restricted to Papua New Guinea and Irian Jaya. Since monotremes exhibit characteristics common with both reptiles and therian mammals, they are of great interest for the study of mammalian evolution.
References
- ↑ Moore K.L. & Dalley A.F. (2006) "Clinically Oriented Anatomy" Fifth Edition, Lippincott, Williams & Wilkins p402
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