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词条 Conjunctiva
释义

  1. Structure

     Blood supply  Nerve supply  Microanatomy 

  2. Function

  3. Clinical significance

  4. Bulbar conjunctival microvasculature

      Vessel morphology    Blood oxygen dynamics    Blood vessel imaging methods    Vasodilation  

  5. See also

  6. Additional images

  7. References

  8. External links

{{Infobox anatomy
| Name = Conjunctiva
| Latin = tunica conjunctiva
| Greek =
| Image = Gray883.png
| Caption = The upper half of a sagittal section through the front of the eyeball. (Label for 'Conjunctiva' visible at center-left)
| Width =
| Image2 = Gray869.png
| Caption2 = Horizontal section of the eyeball. (Conjunctiva labeled at upper left)
| Precursor =
| part_of = Eye
| System =
| Artery = lacrimal artery, anterior ciliary arteries
| Vein =
| Nerve = supratrochlear nerve
| Lymph =
}}

The conjunctiva is a tissue that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of unkeratinized, stratified squamous epithelium with goblet cells, and stratified columnar epithelium. The conjunctiva is highly vascularised, with many microvessels easily accessible for imaging studies.

Structure

The conjunctiva is typically divided into three parts:

Part Area
Palpebral or tarsal conjunctiva Lines the eyelids
Bulbar or ocular conjunctiva Covers the eyeball, over the anterior sclera: This region of the conjunctiva is tightly bound to the underlying sclera by Tenon's capsule and moves with the eyeball movements. The average thickness of the bulbar conjuntival membrane is 33 microns.[1]
Fornix conjunctiva Forms the junction between the bulbar and palpebral conjunctivas: It is loose and flexible, allowing the free movement of the lids and eyeball.[2]

Blood supply

Blood to the bulbar conjunctiva is primarily derived from the ophthalmic artery. The blood supply to the palpebral conjunctiva (the eyelid) is derived from the external carotid artery. However, the circulations of the bulbar conjunctiva and palpebral conjunctiva are linked, so both bulbar conjunctival and palpebral conjunctival vessels are supplied by both the ophthalmic artery and the external carotid artery, to varying extents.[3]

Nerve supply

Sensory innervation of the conjunctiva is divided into four parts:[4]

Area Nerve
Superior
  • Supraorbital nerve
  • Supratrochlear nerve
  • Infratrochlear nerve
Inferior Infraorbital nerve
Lateral Lacrimal nerve (with contribution from zygomaticofacial nerve)
Circumcorneal Long ciliary nerves

Microanatomy

The conjunctiva consists of unkeratinized, both stratified squamous and stratified columnar epithelium, with interspersed goblet cells.[5] The epithelial layer contains blood vessels, fibrous tissue, and lymphatic channels.[5] Accessory lacrimal glands in the conjunctiva constantly produce the aqueous portion of tears.[5] Additional cells present in the conjunctival epithelium include melanocytes, T and B cell lymphocytes.[5]

Function

The conjunctiva helps lubricate the eye by producing mucus and tears, although a smaller volume of tears than the lacrimal gland.[6]

It also contributes to immune surveillance and helps to prevent the entrance of microbes into the eye.

Clinical significance

{{Further|List of eye diseases and disorders}}

Disorders of the conjunctiva and cornea are common sources of eye complaints, in particular because the surface of the eye is exposed to various external influences and is especially susceptible to trauma, infections, chemical irritation, allergic reactions, and dryness.

  • The conjunctival microvascular hemodynamics are affected by diabetic retinopathy (DR), hence can be useful for DR diagnosis and monitoring,[7] and discriminating stages of DR.[8]
  • Type II diabetes is associated with conjunctival hypoxia,[9] increased average blood vessel diameter, and capillary loss.[10][11][12]
  • Sickle-cell anemia is associated with blood vessel sludging, altered blood flow and blood vessel diameter, and capillary micro-haemorrhages.[13][14][15]
  • Hypertension is associated with an increase in the tortuosity of bulbar conjunctival blood vessels and capillary and arteriole loss.[16][17]
  • Carotid artery occlusion is associated with slower conjunctival blood flow and apparent capillary loss.[3]
  • With age, the conjunctiva can stretch and loosen from the underlying sclera, leading to the formation of conjunctival folds, a condition known as conjunctivochalasis.[18][19]
  • The conjunctiva can be affected by tumors which can be benign, pre-malignant or malignant.[20]
  • Leptospirosis, an infection with Leptospira, can cause conjunctival suffusion, which is characterized by chemosis, and redness without exudates.

Bulbar conjunctival microvasculature

Vessel morphology

The bulbar conjunctival microvasculature contains arterioles, meta-arterioles, venules, capillaries, and communicating vessels. Vessel morphology varies greatly between subjects and even between regions of the individual eyes. In some subjects, arterioles and venules can be seen to run parallel with each other. Paired arterioles are generally smaller than corresponding venules.[21] The average bulbar conjunctival vessel has been reported to be 15.1 microns, which reflects the high number of small capillaries, which are typically <10 nano meters in diameter.[22]

Blood oxygen dynamics

The bulbar conjunctival microvasculature is in close proximity to ambient air, thus oxygen diffusion from ambient air strongly influences their blood oxygen saturation. Because of oxygen diffusion, hypoxic bulbar conjunctival vessels will rapidly reoxygenate (in under 10 seconds) when exposed to ambient air (i.e. when the eyelid is open). Closing the eyelid stops this oxygen diffusion by placing a barrier between the bulbar conjunctival microvessels and ambient air.[23]

Blood vessel imaging methods

The bulbar conjunctival microvessels are typically imaged with a high-magnification slit lamp with green filters.[24][25][26] With such high-magnification imaging systems, it is possible to see groups of individual red blood cells flowing in vivo.[24] Fundus cameras may also be used for low-magnification wide field-of-view imaging of the bulbar conjunctival microvasculature. Modified fundus cameras have been used to measure conjunctival blood flow [27] and to measure blood oxygen saturation.[23] Fluorescein angiography has been used to study the blood flow of the bulbar conjunctiva and to differentiate the bulbar conjunctival and episcleral microcirculation.[28][29][30]

Vasodilation

The bulbar conjunctival microvasculature is known to dilate in response to several stimuli and external conditions, including allergens (e.g. pollen),[31] temperature,[32] time-of-day,[32] contact-lens wear,[12] and acute mild hypoxia.[23] Bulbar conjunctival vasodilation has also been shown to correlate changes in emotional state.[33]

Type 2 diabetes is associated with an increase in average bulbar conjunctival vessel diameter and capillary loss.[10][11] Sickle-cell anemia is associated with altered average vessel diameter.[13]

See also

  • Conjunctivochalasis
  • Dry eye
  • Pinguecula
  • Pterygium
  • Rougine
  • Subconjunctival hemorrhage
  • Diabetes
  • Sickle-cell disease
  • Slit lamp

Additional images

References

1. ^{{Cite journal|last=Efron|first=Nathan|last2=Al-Dossari|first2=Munira|last3=Pritchard|first3=Nicola|date=2009-05-01|title=In vivo confocal microscopy of the bulbar conjunctiva|journal=Clinical & Experimental Ophthalmology|volume=37|issue=4|pages=335–344|doi=10.1111/j.1442-9071.2009.02065.x|issn=1442-9071|pmid=19594558}}
2. ^Eye, human Encyclopædia Britannica
3. ^1 {{Cite journal|last=PAVLOU AT|last2=WOLFF HG|date=1959-07-01|title=THe bulbar conjunctival vessels in occlusion of the internal carotid artery|journal=Archives of Internal Medicine|volume=104|issue=1|pages=53–60|doi=10.1001/archinte.1959.00270070055007|issn=0888-2479}}
4. ^{{cite web|url=http://www.nda.ox.ac.uk/wfsa/html/u06/u06_b06.htm |title=Table 1: Summary of sensory nerve supply |accessdate=July 31, 2016 |deadurl=yes |archiveurl=https://web.archive.org/web/20130214055618/http://www.nda.ox.ac.uk/wfsa/html/u06/u06_b06.htm |archivedate=February 14, 2013 }}
5. ^1 2 3 {{cite book|last=Goldman|first=Lee|title=Goldman's Cecil Medicine|publisher=Elsevier Saunders|location=Philadelphia|isbn=978-1437727883|page=2426|edition=24th}}
6. ^London Place Eye Center (2003). Conjunctivitis. Retrieved July 25, 2004.
7. ^{{cite journal|last1=Khansari|first1=Maziyar M.|last2=Wanek|first2=Justin|last3=Tan|first3=Michael|last4=Joslin|first4=Charlotte E.|last5=Kresovich|first5=Jacob K.|last6=Camardo|first6=Nicole|last7=Blair|first7=Norman P.|last8=Shahidi|first8=Mahnaz|title=Assessment of Conjunctival Microvascular Hemodynamics in Stages of Diabetic Microvasculopathy|journal=Scientific Reports|date=7 April 2017|volume=7|pages=45916|doi=10.1038/srep45916|pmid=28387229|pmc=5384077}}
8. ^{{cite journal|last1=Khansari|first1=Maziyar M.|last2=O’Neill|first2=William|last3=Penn|first3=Richard|last4=Chau|first4=Felix|last5=Blair|first5=Norman P.|last6=Shahidi|first6=Mahnaz|title=Automated fine structure image analysis method for discrimination of diabetic retinopathy stage using conjunctival microvasculature images|journal=Biomedical Optics Express|date=1 July 2016|volume=7|issue=7|pages=2597–2606|doi=10.1364/BOE.7.002597|pmid=27446692|pmc=4948616|language=EN|issn=2156-7085}}
9. ^{{Cite journal|last=Isenberg|first=S. J.|last2=McRee|first2=W. E.|last3=Jedrzynski|first3=M. S.|date=1986-10-01|title=Conjunctival hypoxia in diabetes mellitus|journal=Investigative Ophthalmology & Visual Science|volume=27|issue=10|pages=1512–1515|issn=0146-0404|pmid=3759367}}
10. ^1 {{Cite journal|last=Fenton|first=B. M.|last2=Zweifach|first2=B. W.|last3=Worthen|first3=D. M.|date=1979-09-01|title=Quantitative morphometry of conjunctival microcirculation in diabetes mellitus|journal=Microvascular Research|volume=18|issue=2|pages=153–166|issn=0026-2862|pmid=491983|doi=10.1016/0026-2862(79)90025-6}}
11. ^1 {{Cite journal|last=Ditzel|first=Jørn|date=1967-01-12|title=The in Vivo Reactions of the Small Blood Vessels to Diabetes Mellitus|journal=Acta Medica Scandinavica|language=en|volume=182|issue=S476|pages=123–134|doi=10.1111/j.0954-6820.1967.tb12691.x|issn=0954-6820}}
12. ^1 {{Cite journal|last=Cheung|first=A. T.|last2=Ramanujam|first2=S.|last3=Greer|first3=D. A.|last4=Kumagai|first4=L. F.|last5=Aoki|first5=T. T.|date=2001-10-01|title=Microvascular abnormalities in the bulbar conjunctiva of patients with type 2 diabetes mellitus|journal=Endocrine Practice|volume=7|issue=5|pages=358–363|doi=10.4158/EP.7.5.358|issn=1530-891X|pmid=11585371}}
13. ^1 {{Cite journal|last=Fink|first=A I|date=1968-01-01|title=Vascular changes in the bulbar conjunctiva associated with sickle-cell disease: some observations on fine structure.|journal=Transactions of the American Ophthalmological Society|volume=66|pages=788–826|issn=0065-9533|pmc=1310317|pmid=5720854}}
14. ^{{Cite journal|last=Isenberg|first=S. J.|last2=McRee|first2=W. E.|last3=Jedrzynski|first3=M. S.|last4=Gange|first4=S. N.|last5=Gange|first5=S. L.|date=1987-01-01|title=Effects of sickle cell anemia on conjunctival oxygen tension and temperature|journal=Archives of Internal Medicine|volume=147|issue=1|pages=67–69|issn=0003-9926|pmid=3800533|doi=10.1001/archinte.147.1.67}}
15. ^{{Cite journal|last=Wanek|first=Justin|last2=Gaynes|first2=Bruce|last3=Lim|first3=Jennifer I.|last4=Molokie|first4=Robert|last5=Shahidi|first5=Mahnaz|date=2013-08-01|title=Human bulbar conjunctival hemodynamics in hemoglobin SS and SC disease|journal=American Journal of Hematology|language=en|volume=88|issue=8|pages=661–664|doi=10.1002/ajh.23475|issn=1096-8652|pmc=4040222|pmid=23657867}}
16. ^{{Cite journal|last=Harper|first=Robert N.|last2=Moore|first2=Michael A.|last3=Marr|first3=Melissa C.|last4=Watts|first4=L. Earl|last5=Hutchins|first5=Phillip M.|date=1978-11-01|title=Arteriolar rarefaction in the conjunctiva of human essential hypertensives|url=http://www.sciencedirect.com/science/article/pii/0026286278900705|journal=Microvascular Research|volume=16|issue=3|pages=369–372|doi=10.1016/0026-2862(78)90070-5}}
17. ^{{Cite journal|last=Lee|first=R. E.|date=1955-08-01|title=Anatomical and physiological aspects of the capillary bed in the bulbar conjunctiva of man in health and disease|journal=Angiology|volume=6|issue=4|pages=369–382|issn=0003-3197|pmid=13275744|doi=10.1177/000331975500600408}}
18. ^{{cite web|url=http://www.medilexicon.com/medicaldictionary.php?t=19916|title=Conjunctivochalasis - Medical Definition|date=|publisher=Medilexicon.com|accessdate=2012-11-13}}
19. ^WL Hughes Conjunctivochalasis. American Journal of Ophthalmology 1942
20. ^{{Cite journal|last2=Varde|first2=M.|year=2009|title=Ocular surface tumors|journal=Oman Journal of Ophthalmology|volume=2|issue=1|pages=1–2|doi=10.4103/0974-620X.48414|pmc=3018098|pmid=21234216|last1=Biswas|first1=J.}}
21. ^{{Cite journal|last=Meighan|first=S. Spence|date=1956-09-01|title=Blood Vessels of the Bulbar Conjunctiva|journal=The British Journal of Ophthalmology|volume=40|issue=9|pages=513–526|issn=0007-1161|pmc=1324675|pmid=13364178|doi=10.1136/bjo.40.9.513}}
22. ^{{Cite journal|last=Shahidi|first=M.|last2=Wanek|first2=J.|last3=Gaynes|first3=B.|last4=Wu|first4=T.|date=2010-03-01|title=Quantitative Assessment of Conjunctival Microvascular Circulation of the Human Eye|journal=Microvascular Research|volume=79|issue=2|pages=109–113|doi=10.1016/j.mvr.2009.12.003|issn=0026-2862|pmc=3253734|pmid=20053367}}
23. ^1 2 {{Cite journal|last=MacKenzie|first=L. E.|last2=Choudhary|first2=T. R.|last3=McNaught|first3=A. I.|last4=Harvey|first4=A. R.|date=2016-06-15|title=In vivo oximetry of human bulbar conjunctival and episcleral microvasculature using snapshot multispectral imaging|journal=Experimental Eye Research|volume=149|pages=48–58|doi=10.1016/j.exer.2016.06.008|issn=1096-0007|pmid=27317046}}
24. ^1 {{Cite journal|last=van Zijderveld|first=Rogier|last2=Ince|first2=Can|last3=Schlingemann|first3=Reinier O.|date=2014-05-01|title=Orthogonal polarization spectral imaging of conjunctival microcirculation|journal=Graefe's Archive for Clinical and Experimental Ophthalmology = Albrecht von Graefes Archiv für Klinische und Experimentelle Ophthalmologie|volume=252|issue=5|pages=773–779|doi=10.1007/s00417-014-2603-9|issn=1435-702X|pmid=24627137}}
25. ^{{Cite journal|last=Maziyar M Khansari|title=Automated fine structure image analysis method for discrimination of diabetic retinopathy stage using conjunctival microvasculature images|url=https://www.osapublishing.org/boe/abstract.cfm?uri=boe-7-7-2597|journal=Biomedical Optics Express|volume=7}}
26. ^{{Cite journal|title=Automated assessment of hemodynamics in the conjunctival microvasculature network|url=http://ieeexplore.ieee.org/document/7293213/?arnumber=7293213&tag=1|journal=IEEE Transactions on Medical Imaging|volume=35|issue=2|pages=605–11|doi=10.1109/TMI.2015.2486619|pmid=26452274|pmc=4821773|year=2015|last1=m Khansari|first1=Maziyar|last2=Wanek|first2=Justin|last3=e Felder|first3=Anthony|last4=Camardo|first4=Nicole|last5=Shahidi|first5=Mahnaz}}
27. ^{{Cite journal|last=Jiang|first=Hong|last2=Ye|first2=Yufeng|last3=DeBuc|first3=Delia Cabrera|last4=Lam|first4=Byron L|last5=Rundek|first5=Tatjana|last6=Tao|first6=Aizhu|last7=Shao|first7=Yilei|last8=Wang|first8=Jianhua|date=2013-01-01|title=Human conjunctival microvasculature assessed with a retinal function imager (RFI)|journal=Microvascular Research|volume=85|pages=134–137|doi=10.1016/j.mvr.2012.10.003|issn=0026-2862|pmc=3534915|pmid=23084966}}
28. ^{{Cite journal|last=Meyer|first=P. A.|date=1988-01-01|title=Patterns of blood flow in episcleral vessels studied by low-dose fluorescein videoangiography|journal=Eye (London, England)|volume=2|pages=533–546|doi=10.1038/eye.1988.104|issn=0950-222X|pmid=3256492|issue=5}}
29. ^{{Cite journal|last=Ormerod|first=L. D.|last2=Fariza|first2=E.|last3=Webb|first3=R. H.|date=1995-01-01|title=Dynamics of external ocular blood flow studied by scanning angiographic microscopy|journal=Eye (London, England)|volume=9|pages=605–614|doi=10.1038/eye.1995.148|issn=0950-222X|pmid=8543081|issue=5}}
30. ^{{Cite journal|last=Meyer|first=P. A.|last2=Watson|first2=P. G.|date=1987-01-01|title=Low dose fluorescein angiography of the conjunctiva and episclera.|url=http://bjo.bmj.com/content/71/1/2|journal=British Journal of Ophthalmology|language=en|volume=71|issue=1|pages=2–10|doi=10.1136/bjo.71.1.2|issn=1468-2079|pmid=3814565|pmc=1041073}}
31. ^{{Cite journal|last=Hvoarak|first=Friedrich|last2=Berger|first2=Uwe|last3=Menapace|first3=Reinhard|last4=Schuster|first4=Norbert|date=1996|title=Quantification of conjunctival vascular reaction by digital imaging|url=http://www.sciencedirect.com/science/article/pii/S0091674996700817|journal=Journal of Allergy and Clinical Immunology|volume=98|issue=3|doi=10.1016/S0091-6749(96)70081-7|pmid=|accessdate=July 31, 2016|via=Elsevier Science Direct|pages=495–500}}
32. ^1 {{Cite journal|last=Duench|first=Stephanie|last2=Simpson|first2=Trefford|last3=Jones|first3=Lyndon W.|last4=Flanagan|first4=John G.|last5=Fonn|first5=Desmond|date=2007-06-01|title=Assessment of variation in bulbar conjunctival redness, temperature, and blood flow|journal=Optometry and Vision Science|volume=84|issue=6|pages=511–516|doi=10.1097/OPX.0b013e318073c304|issn=1040-5488|pmid=17568321}}
33. ^{{Cite journal|last=Provine|first=Robert R.|last2=Nave-Blodgett|first2=Jessica|last3=Cabrera|first3=Marcello O.|date=2013-11-01|title=The Emotional Eye: Red Sclera as a Uniquely Human Cue of Emotion|journal=Ethology|language=en|volume=119|issue=11|pages=993–998|doi=10.1111/eth.12144|issn=1439-0310}}

External links

  • Medicinenet.com (1999). Conjunctiva. Retrieved July 25, 2004.
  • {{LoyolaMedEd|medicine/pulmonar/images/anatomy/eyeli.jpg}}
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1 : Human eye anatomy
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