Question
The structure marked by an arrow in the picture below contains which of the following collagen type?
A. Colagen I.
B. Collagen II.
C. Collagen III.
D. Collagen IV.
Show Answer
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Correct Answer » B Explanation |
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Ans:B. Collagen II.
The structure marked by an arrow in the picture above represents Vitreous humor and it contains collagen type II.
Vitreous humour
- It is a transparent, colorless, gelatinous mass that fills the space in the eye between the lens and the retina.
- Produced by cells in the non-pigmented portion of the ciliary body.
- Biochemical Properties:
- It is composed mostly of phagocytes, which remove unwanted cellular debris in the visual field, and hyalocytes.
- The vitreous humour contains no blood vessels, and 98–99% of its volume is water .
- In addition to water, the vitreous consists of salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibrils with glycosaminoglycan, hyaluronan, opticin, and a wide array of proteins.
- It has a refractive index of 1.336.
- Clinical Significance:
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- Unlike the fluid in the frontal parts of the eye (aqueous humour) which is continuously replenished, the gel in the vitreous chamber is stagnant. Therefore, if blood, cells or other byproducts of inflammation get into the vitreous, they will remain there unless removed surgically.These are known as floaters.
- The metabolic exchange and equilibration between systemic circulation and vitreous humour is so slow that vitreous humour is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted or metabolized from the general circulation.
- Vitreous humor is strongly recommended as a body fluid for determination of ethanol in postmortem toxicology to help establish whether the deceased had consumed ethanol before death.
- Forensic Significance:
- After death, the vitreous resists putrifaction longer than other body fluids. The vitreous potassium concentration rises so predictably within the hours, days and weeks after death, that vitreous potassium levels are frequently used to estimate the time-of-death
