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The urothelium is the tissue
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
 layer that lines much of the urinary tract, including the renal pelvis
Renal pelvis

The renal pelvis is the funnel-like dilated proximal part of the ureter in the kidney.It is the point of convergence of two or three major calyces....
, the ureter
Ureter

In human anatomy, the ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually long....
s, the bladder
Urinary bladder

In anatomy, the urinary bladder is a solid, muscle, and distensible organ that sits on the pelvic floor in mammals. It is the organ that collects urine excreted by the kidneys prior to disposal by urination....
, and parts of the urethra
Urethra

In anatomy, the urethra is a tube which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes to pass urine to the outside, and also a reproductive function in the male, as a passage for semen....
.

helium is the most specialized epithelium
Epithelium

In biology and medicine, epithelium is a Biological tissue composed of cell s that line the cavities and surfaces of structures throughout the body....
 and plays important and conflicting roles: the urothelium must act as a permeability barrier -- protecting underlying tissues against noxious urine
Urine

Urine is a liquid waste product of the body secreted by the kidneys by a process of filtration from blood called urination and excreted through the urethra....
 components — while also stretching to accommodate urine pressures.

helium is a tissue layer of approximately 3-5 cell layers, accompanied by a thick layer of protective glycoprotein
Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
 plaques at its luminal
Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine. By extension, a lumen can also be the inside space of a cellular component or structure, such as the endoplasmic reticulum....
 (apical) surface, and is classified as transitional epithelium.






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Encyclopedia


The urothelium is the tissue
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
 layer that lines much of the urinary tract, including the renal pelvis
Renal pelvis

The renal pelvis is the funnel-like dilated proximal part of the ureter in the kidney.It is the point of convergence of two or three major calyces....
, the ureter
Ureter

In human anatomy, the ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually long....
s, the bladder
Urinary bladder

In anatomy, the urinary bladder is a solid, muscle, and distensible organ that sits on the pelvic floor in mammals. It is the organ that collects urine excreted by the kidneys prior to disposal by urination....
, and parts of the urethra
Urethra

In anatomy, the urethra is a tube which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes to pass urine to the outside, and also a reproductive function in the male, as a passage for semen....
.

Functions

Urothelium is the most specialized epithelium
Epithelium

In biology and medicine, epithelium is a Biological tissue composed of cell s that line the cavities and surfaces of structures throughout the body....
 and plays important and conflicting roles: the urothelium must act as a permeability barrier -- protecting underlying tissues against noxious urine
Urine

Urine is a liquid waste product of the body secreted by the kidneys by a process of filtration from blood called urination and excreted through the urethra....
 components — while also stretching to accommodate urine pressures.

Structure

Urothelium is a tissue layer of approximately 3-5 cell layers, accompanied by a thick layer of protective glycoprotein
Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
 plaques at its luminal
Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine. By extension, a lumen can also be the inside space of a cellular component or structure, such as the endoplasmic reticulum....
 (apical) surface, and is classified as transitional epithelium. Epithelia are tissue layers that line interior and exterior body surfaces:

  • skin
  • mucosal linings of the mouth/lung/digestive and reproductive tracts
  • lining of ducts in prostate and breast


Multi-layered epithelia are typically structured with specialized, mature cells at the surface, whereas less mature "basal
Basal

Basal is a term with several scientific meanings:*A Basal is one which forms an outgroup to a larger clade. As such the term is relative.*Basal refers to a type of insulin dosing....
" cells occupy the base of the epithelium. The mature surface cells are continually sloughed off and are replaced by a supply of newly maturing cells. The basal cell layer contains tissue-specific stem cells that are capable of cell division for the lifetime of the animal and thereby generate the pool of maturing cells that maintains tissue homeostasis. Because of this continual epithelial renewal process, chemotherapeutic drugs that interfere with cell division can cause complications of deteriorating epithelia (e.g., oral sores).

Pathology

Epithelia are sites of specific diseases.

  • Cancer
    Cancer

    Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
    s that originate in epithelial cells are termed carcinomas, and they are characterized as having lost the mature, differentiated morphology and molecular patterns of the normal tissue. Infectious diseases also afflict epithelia where diverse microbes (viruses, bacteria, fungi) have surface structures that bind specific features of particular epithelial cells (e.g., influenza
    Influenza

    Influenza, commonly known as the flu, is an infectious disease that affects birds and mammals caused by RNA viruses of the biological family Orthomyxoviridae ....
     virus binds repiratory epithelium). Genetic defects can also inhibit normal epithelial integrity, such as defects in intercellular adhesion molecules that result in blistering diseases.


  • The second most common infectious disease is urinary tract infection
    Urinary tract infection

    A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Although urine contains a variety of fluids, salts, and waste products, it usually does not have bacteria in it....
     (UTI). UTIs afflict approximately half of all women during their lifetime, and about 25% of these women will suffer recurrent UTIs. The majority of these infections are due to uropathogenic Escherichia coli
    Escherichia coli

    'Escherichia coli' , is a Gram negative bacterium that is commonly found in the lower gastrointestinal tract of warm-blooded animals. Most E....
     bacteria (commonly known as E. coli). However, UTIs can also develop in healthcare settings and such infections are caused by a greater frequency of non-E. coli bacteria.


  • One unusual condition which affects the urothelium is interstitial cystitis
    Interstitial cystitis

    Interstitial cystitis is a urinary bladder disease of unknown cause characterised by urinary frequency , urgency, pressure and/or pain in the bladder and/or pelvis....
     (IC), a condition with symptoms similar to UTI (frequency, urgency, pressure and/or pain). Urine culture, however, is negative. During hydrodistention of the bladder, small petechial hemorrhages (aka glomerulations) are frequently found throughout the bladder. Larger "Hunner's Ulcers", known for their characteristic waterfall bleeding effect, represent larger areas of bladder wall thinning and/or trauma. The cause of IC is currently unknown though some suggest that it could be genetic, the result of traumatic injury (aka chemical exposure), infection, autoimmune disease, etc. Researcher Susan Keay (University of Maryland) has found an unusual protein in the urine of IC patients which appears to interfere with healing, known as an Antiproliferative Factor. Research efforts into IC are focused on the urothelium, including newly discovered signaling molecules which suggest that the urothelium is far more than a barrier, as well as how the urothelium interacts with proximal nerves and smooth muscle.


  • Urothelium is susceptible to carcinoma. Because the bladder is in contact with urine for extended periods, chemicals that become concentrated in the urine can cause Bladder cancer
    Bladder cancer

    Bladder cancer refers to any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder....
    . For example, cigarette smoking leads to the concentration of carcinogens in the urine and is a leading cause of bladder cancer. Occupational exposure to certain chemicals is also a risk factor for bladder cancer.


External links

  • [https://courses.stu.qmul.ac.uk/smd/kb/microanatomy/humandev/answers/9a.htm Histology at qmul.ac.uk]