Cornea Flashcards

Explore corneal anatomy, including its five principal layers, cellular organization, transparency, innervation, and clinical landmarks.

Card 1 of 30Question

What is the cornea?

The transparent, avascular anterior portion of the fibrous tunic of the eyeball.

In This Section

1. What is the cornea?

The transparent, avascular anterior portion of the fibrous tunic of the eyeball.

2. What proportion of the outer fibrous coat of the eyeball is formed by the cornea?

Approximately the anterior one-sixth.

3. What is the junction between the cornea and sclera called?

The corneoscleral limbus.

4. What are the five principal layers of the cornea from anterior to posterior?

Epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium.

5. What type of epithelium covers the anterior surface of the cornea?

Nonkeratinized stratified squamous epithelium.

6. What is the primary function of the corneal epithelium?

To provide a protective barrier against pathogens, fluid entry, and mechanical injury.

7. Where are the stem cells responsible for corneal epithelial renewal located?

In the basal epithelial region of the corneoscleral limbus.

8. What is Bowman's layer?

An acellular, collagen-rich layer immediately beneath the corneal epithelial basement membrane.

9. Which corneal layer constitutes approximately 90% of corneal thickness?

The corneal stroma.

10. What are the principal structural components of the corneal stroma?

Regularly arranged collagen lamellae, keratocytes, and extracellular ground substance.

11. Which cells maintain the extracellular matrix of the corneal stroma?

Keratocytes.

12. Which collagen type predominates in the corneal stromal lamellae?

Type I collagen.

13. What is Descemet's membrane?

The specialized basement membrane of the corneal endothelium.

14. What type of cells form the corneal endothelium?

A single layer of predominantly hexagonal, flattened cells.

15. What is the main function of the corneal endothelium?

To regulate stromal hydration through barrier and active ion transport mechanisms.

16. Why does endothelial dysfunction cause corneal edema?

Impaired fluid transport allows excess water to accumulate in the corneal stroma.

17. What anatomical features contribute to corneal transparency?

Regular collagen organization, controlled stromal hydration, and absence of blood vessels.

18. How does the cornea receive oxygen under normal open-eye conditions?

Primarily by diffusion from atmospheric oxygen dissolved in the tear film.

19. What is the principal source of nutrients for the posterior cornea?

The aqueous humor of the anterior chamber.

20. Which cranial nerve provides sensory innervation to the cornea?

The trigeminal nerve (cranial nerve V), through its ophthalmic division (V1).

21. Which nerves directly carry most sensory fibers into the cornea?

The long ciliary nerves, branches of the nasociliary nerve.

22. Which nerve forms the afferent limb of the corneal reflex?

The ophthalmic division of the trigeminal nerve (V1).

23. Which nerve forms the efferent limb of the corneal blink reflex?

The facial nerve (cranial nerve VII), which activates the orbicularis oculi muscle.

24. What is the principal optical function of the cornea?

To refract incoming light, providing approximately two-thirds of the eye's total refractive power.

25. What is the approximate refractive power of the human cornea?

Approximately 43 diopters.

26. What is the approximate normal central corneal thickness in adults?

Approximately 540 micrometers, with normal individual variation.

27. How does the regenerative capacity of corneal endothelial cells differ from that of epithelial cells?

Human endothelial cells have very limited regenerative capacity in vivo, unlike epithelial cells.

28. What is the anatomical basis of keratoconus?

Progressive corneal thinning and protrusion that produce an irregular, cone-shaped corneal surface.

29. What is the anatomical defect in Fuchs endothelial corneal dystrophy?

Progressive dysfunction and loss of corneal endothelial cells, often with Descemet's membrane guttae.

30. What is the significance of the corneal limbus in aqueous humor drainage?

It borders the iridocorneal angle, where the trabecular meshwork and Schlemm's canal drain aqueous humor.