Histology Of Cornea

HISTOLOGY OF CORNEA

Q. 1

Kayser Fleischer ring is found in which layer of cornea ?

 A

Bowman’s membrane

 B

Substantia propria

 C

Descemet’s membrane

 D

Endothelium

Q. 1

Kayser Fleischer ring is found in which layer of cornea ?

 A

Bowman’s membrane

 B

Substantia propria

 C

Descemet’s membrane

 D

Endothelium

Ans. C

Explanation:

Ans. Descemet’s membrane


Q. 2

Metabolically most active layer of cornea is:

 A

Endothelium

 B

Stroma

 C

Descemets membrane

 D

Epithelium

Q. 2

Metabolically most active layer of cornea is:

 A

Endothelium

 B

Stroma

 C

Descemets membrane

 D

Epithelium

Ans. D

Explanation:

Ans. Epithelium


Q. 3

Corneal epithelium is composed of:

 A

Stratified keratinized epithelium

 B

Stratified non-keratinized epithelium

 C

Columnar epithelium

 D

Pseudostratified epithelium

Q. 3

Corneal epithelium is composed of:

 A

Stratified keratinized epithelium

 B

Stratified non-keratinized epithelium

 C

Columnar epithelium

 D

Pseudostratified epithelium

Ans. B

Explanation:

Ans. Stratified non-keratinized epithelium


Q. 4

Keratic precipitates are on which layer of cornea:

 A

Epithelium

 B

Endothelium

 C

Stroma

 D

Bowman’s membrane

Q. 4

Keratic precipitates are on which layer of cornea:

 A

Epithelium

 B

Endothelium

 C

Stroma

 D

Bowman’s membrane

Ans. B

Explanation:

Ans. Endothelium


Q. 5

Normal endothelial cell density [per mm square] in cornea to maintain transparency is:               

September 2007

 A

300

 B

400

 C

500

 D

600

Q. 5

Normal endothelial cell density [per mm square] in cornea to maintain transparency is:               

September 2007

 A

300

 B

400

 C

500

 D

600

Ans. C

Explanation:

Ans. C: 500

The corneal endothelium is embryologically derived from the neural crest. The postnatal total endothelial cellularity of the cornea (approximately 300,000 cells per cornea) is achieved as early as the second trimester of gestation. Thereafter the endothelial cell density (but not the absolute number of cells) rapidly declines in direct proportion to the areal growth of the fetal cornea, achieving a final adult density of approximately 500 cells/mm2.


Q. 6

Stroma of cornea develops from ‑

 A

Neural ectoderm

 B

Surface ectoderm

 C

Mesoderm

 D

Neural crest

Q. 6

Stroma of cornea develops from ‑

 A

Neural ectoderm

 B

Surface ectoderm

 C

Mesoderm

 D

Neural crest

Ans. C

Explanation:

Corneal epithelium develops from Surface ectoderm.

Corneal stroma develops from Mesoderm.


Q. 7

Type of collagen present in cornea ‑

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Q. 7

Type of collagen present in cornea ‑

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Ans. A

Explanation:

Ans. is ‘a’ i.e., Type I


Q. 8

Density of cells in adult corneal endothelium ‑

 A

2000 cells/mm2

 B

3000 cells/mm2

 C

4000 cells/mm2

 D

5000 cells/mm2

Q. 8

Density of cells in adult corneal endothelium ‑

 A

2000 cells/mm2

 B

3000 cells/mm2

 C

4000 cells/mm2

 D

5000 cells/mm2

Ans. B

Explanation:

Ans. is ‘b’ i.e., 3000 cells/mm2

The cell density of corneal endothelium is around 3000 cells/mm2 in young adults, which decreases with the advancing age.


Q. 9

Schwalbe’s line is the peripheral limit of which layer of cornea?

 A

Bowman’s layer

 B

Stroma

 C

Descemet’s layer

 D

Endothelium

Q. 9

Schwalbe’s line is the peripheral limit of which layer of cornea?

 A

Bowman’s layer

 B

Stroma

 C

Descemet’s layer

 D

Endothelium

Ans. C

Explanation:

Ans. is `c’ i.e., Descemet’s layer

Histology of cornea

The cornea has five distinct layers (from superficial to deep) :‑

1) Epithelium :- It is the outermost part of cornea and is composed of stratified squamous non-keratinized epithelial cells.

2) Bowman’s membrane : – It is not a true membrane but simply a condensed superficial part of stroma. Once destroyed, it does not regenerate.

3) Stroma (Substantia propria) : – This layer constitutes most of the cornea (90% of thickness). It consists of collagen fibrils (lamellae) embedded in hydrated matrix of proteoglycans.

4) Descemet’s membrane : – This layer bounds the stroma posteriorly. In the periphery it appears to end at the anterior limit of trabecular meshwork as Schwable’s ring.

5)  Endothelium : – It is a single layer of flat polygnonal cells. The endothelial cells contain ‘active-pump’ mechanism and is the most important layer in maintaining the transparency of cornea.


Q. 10

Precipitates shown in photograph are found in …….. layer of Cornea 

 A

Epithelium

 B

Endothelium 

 C

Stroma

 D

 Bowman’s membrane

Q. 10

Precipitates shown in photograph are found in …….. layer of Cornea 

 A

Epithelium

 B

Endothelium 

 C

Stroma

 D

 Bowman’s membrane

Ans. B

Explanation:

Endothelium (Precipitates shown: Keratic precipitates)

Keratic precipitates (KPs)

KPs are proteinaceous cellular deposits occurring at the back of cornea (corneal endothelial deposits). Keratic precipitates are formed by the aggregation of polymorphonuclear cells, lymphocytes, and epitheloid cells.


Q. 11

Corneal stroma is derived from 

 A

Paraxial mesoderm

 B

Intermediate mesoderm

 C

Lateral plate mesoderm

 D

Ectoderm

Q. 11

Corneal stroma is derived from 

 A

Paraxial mesoderm

 B

Intermediate mesoderm

 C

Lateral plate mesoderm

 D

Ectoderm

Ans. C

Explanation:

Ans. is ‘c’ i.e., Lateral plate mesoderm

  • Corneal stroma develops from lateral plate mesoderm (somatopleuric mesoderm).

Derivatives of mesoderm

  • Mesoderm is divided into three parts :‑

1. Paraxial mesoderm : It is organized into somites which in turn gives rise to :‑

  • Sclerotomes : Form axial skeleton including vertebrae, and parts of neurocranium.
  • Myotomes : Form all voluntary (skeletal) muscles of head, trunk and limbs.
  • Dermatomes : Form dermis of skin, especially over dorsal regions.

2. Intermediate mesoderm : It gives rise to major portion of urogeninal system :‑

  1. Urinary organs : Kidney, ureters, trigone of bladder, posterior wall female urethra, posterior wall of upper half of prostatic part of male urethra, inner glandular zone of prostate.
  2. Reproductive organs : Gonads (testis and ovary), epididymis, ducts deferens, seminal vesicle, ejaculatory duct, uterus, uterine tube and upper part of vagina.

3. Lateral plate mesoderm : It forms :‑

   1.Somatopleuric mesoderm (parietal layer)

  • All connective tissues including specialized connective tissues like bone, cartilage, adipose tissue
  • Superficial and deep fascia
  • Ligaments, tendons, aponeurosis
  • Parietal pleura, parietal peritoneum and tunica vaginalis of testis
  • Dura-mater
  • Lid muscles, extraocular muscles
  • Sclera, choroid, vitreous
  • Corneal stroma, iris and ciliary body (except epithelium)

   2. Splanchnopleuric mesoderm (visceral layer)

  • Smooth muscle and connective tissue of respiratory tract, gut, blood vessels and heart
  • Adrenal cortex
  • Mesothelium (visceral layer) of pleural, peritoneal and pericardeal cavities
  • Mesenchyme surrounding pericardial coelom gives rise to myocardium and serous pericardiun
  • Spleen and lymph nodes

   3.  Spetum transversum

  • Diaphragm
  • Fibrous pericardium

   4.  Angiogenic mesoderm

  • Endocardium of heart
  • Endothelium of blood and lymphatic vessels
  • Microglia, tissue macrophages
  • Circulating blood cells

Q. 12

Reis-Buckler dystrophy affects which layer of cornea 

 A

Epithelium

 B

Stroma

 C

Bowman’s membrane

 D

Endothelium

Q. 12

Reis-Buckler dystrophy affects which layer of cornea 

 A

Epithelium

 B

Stroma

 C

Bowman’s membrane

 D

Endothelium

Ans. C

Explanation:

Ans. is ‘c’ i.e., Bowman’s membrane



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