Transitional epithelium

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Urothelium
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Transitional epithelium
Transitional epithelium
Transitional epithelium of the bladder, known as urothelium. The rounded surface of the apical cells is a distinguishing characteristic of this type of epithelium.
Details
SystemUrinary system
Identifiers
THH2.00.02.0.02033
Anatomical terms of microanatomy
This article is part of a series on
Epithelia
Squamous epithelial cell
Columnar epithelial cell
Cuboidal epithelial cell
Specialised epithelia
Other
transitional epithelium
Transitional epithelium animation, highlighting the epithelial layer, then underlying connective tissue. Contrast the messy appearance of the epithelial surface to other epithelial tissues.

Transitional epithelium is a type of

epithelial cells which can contract and expand in order to adapt to the degree of distension needed. Transitional epithelium lines the organs of the urinary system and is known here as urothelium (pl.: urothelia). The bladder
, for example, has a need for great distension.

Structure

The appearance of transitional epithelium differs according to its cell layer. Cells of the basal layer are

squamous
and irregular.

Cell layers

Transitional epithelium is made up of three types of cell layers: basal, intermediate, and superficial.

microvilli and a fibrillar mucous coat.[3]

The epithelium contains many intimate and delicate connections to neural and connective tissue. These connections allow for communication to tell the cells to expand or contract. The superficial layer of transitional epithelium is connected to the basal layer via cellular projections, such as intermediate filaments protruding from the cellular membrane. These structural elements cause the epithelium to allow distension; however, these also cause the tissue to be relatively fragile and, therefore, difficult to study. All cells touch the basement membrane.[citation needed]

Cell membrane

The urothelium is the most impermeable membrane in the mammalian body.

hemidesmosomes to attach the cells at the basement membrane.[5]

Function

The transitional epithelium cells stretch readily in order to accommodate fluctuation of volume of the liquid in an organ (the distal part of the urethra becomes non-keratinized stratified squamous epithelium in females; the part that lines the bottom of the tissue is called the basement membrane). Transitional epithelium also functions as a barrier between the lumen, or inside hollow space of the tract that it lines and the bloodstream. To help achieve this, the cells of transitional epithelium are connected by tight junctions, or virtually impenetrable junctions that seal together to the cellular membranes of neighboring cells. This barrier prevents re-absorption of toxic wastes and pathogens by the bloodstream.

Clinical significance

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

cigarette smoking leads to the concentration of carcinogens in the urine and is a leading cause of bladder cancer. Aristolochic acid, a compound found in plants of the family Aristolochiaceae, also causes DNA mutations and is a cause of liver, urothelial and bladder cancers.[9] Occupational exposure to certain chemicals is also a risk factor for bladder cancer. This can include aromatic amines (aniline dye), polycyclic aromatic hydrocarbons, and diesel engine exhaust.[10]

Carcinoma

Carcinoma is a type of cancer that occurs in epithelial cells. Transitional cell carcinoma is the leading type of bladder cancer, occurring in 9 out of 10 cases.[11] It is also the leading cause of cancer of the ureter, urethra, and urachus, and the second leading cause of cancer of the kidney. Transitional cell carcinoma can develop in two different ways. Should the transitional cell carcinoma grow toward the inner surface of the bladder via finger-like projections, it is known as papillary carcinoma. Otherwise, it is known as flat carcinoma.[11] Either form can transition from non-invasive to invasive by spreading into the muscle layers of the bladder. Transitional cell carcinoma is commonly multifocal, more than one tumor occurring at the time of diagnosis.

Transitional cell carcinoma can metastasize, or spread to other parts of the body via the surrounding tissues, the lymph system, and the bloodstream. It can spread to the tissues and fat surrounding the kidney, the fat surrounding the ureter, or, more progressively, lymph nodes and other organs, including bone. Common risk factors of transitional cell carcinoma include long-term misuse of pain medication, smoking, and exposure to chemicals used in the making of leather, plastic, textiles, and rubber.[12]

Transitional cell carcinoma patients have a variety of treatment options. These include nephroureterectomy, or the removal of kidney, ureter, and bladder cuff, and segmental resection of the ureter. This is an option only when the cancer is superficial and infects only the bottom third of the ureter. The procedure entails removing the segment of cancerous ureter and reattaching the end.[12] Patients with advanced bladder cancer or disease, also often look to bladder reconstruction as a treatment. Current methods of bladder reconstruction include the use of gastrointestinal tissue. However, while this method is effective in improving the function of the bladder, it can actually increases the risk of cancer, and can cause other complications, such as infections, urinary stones, and electrolyte imbalance. Therefore, other methods loom in the future. For example, current research paves the way for use of pluripotent stem cells to derive urothelium, as they are highly and indefinitely proliferative in vitro (i.e. outside of the body).[4]

Interstitial cystitis

Interstitial cystitis (IC) a type of painful bladder syndrome is a chronic disease of the bladder that causes feelings of pressure and pain in the bladder among other symptoms which can range from mild to severe. Urinary frequency and urgency are the most common symptoms associated with the disease.[13] The exact causes of IC/BPS are unknown, but there is evidence of an association between increased permeability of the urothelium and IC. Since the purpose of the urothelium is to act as a highly resistant barrier, the loss of this function has serious clinical implications. Many patients with IC have exhibited a loss of umbrella cells.[14]

Urothelial lesions

Gallery

  • Types of epithelium
    Types of epithelium
  • Schematic view of transitional epithelium
    Schematic view of transitional epithelium
  • Vertical section of bladder wall.
    Vertical section of bladder wall.
  • Transverse section of ureter.
    Transverse section of ureter.

See also

List of distinct cell types in the adult human body

References

  1. ^ a b Sapkota, Anupama (2020-09-28). "Transitional epithelium- definition, structure, functions, examples". Microbe Notes. Retrieved 2021-10-17.
  2. ^ Marieb, E., & Hoehn, K. (2013). Human anatomy & physiology (9th ed., pp. 122-124). Boston: Pearson.
  3. ^ a b Monis, B., & Zambrano, D. (1968). Ultrastructure of transitional epithelium of man. Zeitschrift für Zellforschung und Microscopical Anatomie, 87(1), 101-117.
  4. ^ a b c d Osborn, S. L., & Kurzrock, E. A. (2015). Production of Urothelium from Pluripotent Stem Cells for Regenerative Applications. Current Urology Reports, 16(1), 1+. Retrieved from http://go.galegroup.com/ps/i.do?id=GALE%7CA390522720&v=2.1&u=clemsonu_main&it=r&p=AONE&sw=w&asid=bf6961c15c9b9523113dee93fd8df89c
  5. ^ a b c Hicks, R. (1965). The Fine Structure Of The Transitional Epithelium Of Rat Ureter. The Journal of Cell Biology, 26(1), 25-48. Retrieved November 25, 2014, from http://jcb.rupress.org/content/26/1/25.abstract
  6. PMID 4155089
    .
  7. ^ Hicks, R. (1966). THE FUNCTION OF THE GOLGI COMPLEX IN TRANSITIONAL EPITHELIUM: Synthesis of the Thick Cell Membrane. The Journal of Cell Biology, 30(3), 623-643. Retrieved November 25, 2014, from http://jcb.rupress.org/content/30/3/623.abstract
  8. ^ a b c Firth, J. A., & Hicks, R. M. (1973). Interspecies variation in the fine structure and enzyme cytochemistry of mammalian transitional epithelium. Journal of Anatomy, 116(Pt 1), 31–43.
  9. PMID 26015808.{{cite journal}}: CS1 maint: DOI inactive as of March 2024 (link
    )
  10. ^ "Bladder cancer risk factors". Cancer Research UK. Retrieved 27 July 2014.
  11. ^ a b American Cancer Society. (2014). Bladder cancer. Retrieved November 25, 2014, from http://www.cancer.org/cancer/bladdercancer/detailedguide/bladder-cancer-what-is-bladder-cancer Archived 2016-12-01 at the Wayback Machine
  12. ^ a b Transitional Cell Cancer. (2012, April 13). Retrieved December 14, 2014, from https://my.clevelandclinic.org/health/diseases_conditions/hic_Transitional_Cell_Cancer_of_Renal_Pelvis_and_Ureter
  13. ^ "What is Interstitial Cystitis(IC)/Bladder Pain Syndrome? - Urology Care Foundation". www.urologyhealth.org. Retrieved 2021-07-12.
  14. PMID 26751576
    .

Bibliography

External links
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