This document describes the anatomy of the extraocular muscles and accessory organs of the eye. It discusses the six extrinsic muscles that control eye movement, including the four rectus and two oblique muscles. It also describes the eyelids, eyelashes, lacrimal apparatus, and other protective structures around the eye. The document provides detailed information on the layers of the eyelids and functions of the tears, lacrimal glands, and associated drainage system.

1. ANATOMY OF THE EXTRAOCULAR
MUSCLES
OF THE EYE
PREPARED BY:
USHA RANI KANDULA,
ASSISTANT PROFESSOR,
DEPARTMENT OF ADULT HEALTH NURSING,
ARSI UNIVERSITY,ASELLA,ETHIOPIA,
SOUTH EAST AFRICA.

2. EXTRAOCULAR MUSCLES OF THE EYE
•The eyeballs are moved by six extrinsic muscles,
attached at one end to the eyeball and at the
other to the walls of the orbital cavity.

3. There are four straight (rectus) muscles and two
oblique muscles . They are:
• Medial Rectus
• Lateral Rectus
• Superior Rectus
• Inferior Rectus
• Superior Oblique
• Inferior Oblique.

4. •Movement of the eyes to look in a particular
direction is under voluntary control, but
coordination of movement, needed for
convergence and accommodation to near or
distant vision, is under autonomic
(involuntary) control.

5. •Movements of the eyes made by the action of
these muscles.

6. NERVE SUPPLY TO THE MUSCLES OF THE
EYE
•The oculomotor nerves supply the intrinsic
muscles of the iris and ciliary body.

7. ACCESSORY ORGANS OF THE EYE
•The eye is a delicate organ which is protected
by several structures:
• Eyebrows
• Eyelids and Eyelashes
• Lacrimal Apparatus.

8. THE EXTRINSIC MUSCLES OF THE
EYE.
•EYEBROWS
•These are two arched ridges of the
supraorbital margins of the frontal bone.

9. •Numerous hairs (eyebrows) project obliquely
from the surface of the skin.
•They protect the anterior aspect of the eyeball
from sweat, dust and other foreign bodies.

10. EYELIDS (PALPEBRAE)
•The eyelids are two movable folds of tissue
situated above and below the front of each eye.

11. •On their free edges there are short curved
hairs, the eyelashes.
•The layers of tissue which form the eyelids
are:

12. •A thin covering of skin
•• A thin sheet of loose (areolar) tissue
•• Two muscles — the orbicularis oculi and
levator palpebrae.

13. SUPERIORIS
•a thin sheet of dense connective tissue, the
tarsal plate, larger in the upper than in the
lower eyelid, which supports the other
structures.
• a lining of conjunctiva.

14. CONJUNCTIVA
•This is a fine transparent membrane which lines
the eyelids and the front of the eyeball.

15. •Where it lines the eyelids it consists of highly
vascular columnar epithelium.

16. •Corneal conjunctiva consists of less-vascular
stratified epithelium. When the eyelids are
closed the conjunctiva becomes a closed sac.

17. •It protects the delicate cornea and the front of
the eye.

18. •When eyedrops are administered they are
placed in the lower conjunctival sac.

19. •The medial and lateral angles of the eye where
the upper and lower lids come together are
called respectively the medial canthus and the
lateral canthus.

20. EYELID MARGINS
•Along the edges of the lids there are numerous
sebaceous glands,
•some with ducts opening into the hair follicles
of the eyelashes and some on to the eyelid
margins between the hairs.

21. •Tarsal glands (meibomian glands) are modified
sebaceous glands embedded in the tarsal plates
with ducts that open on to the inside of the
free margins of the eyelids.

22. •They secrete an oily material, spread over the
conjunctiva by blinking, which delays
evaporation of tears.

23. FUNCTIONS
•The eyelids and eyelashes protect the eye from
injury.

24. •Reflex closure of the lids occurs when the
conjunctiva or eyelashes are touched, when an
object comes close to the eye or when a bright
light shines into the eye — this is called the
conjunctival or corneal reflex.

25. •Blinking at about 3- to 7-second intervals
spreads tears and oily secretions over the
cornea, preventing drying.

26. •When the orbicularis oculi contracts, the eyes
close.
•When the levator palpebrae contract the
eyelids open.

27. LACRIMAL APPARATUS
•For each eye this consists of:
• 1 lacrimal gland and its ducts
• 2 lacrimal canaliculi
• 1 lacrimal sac
• 1 nasolacrimal duct.

28. •The lacrimal glands are exocrine glands situated
in recesses in the frontal bones on the lateral
aspect of each eye just behind the supraorbital
margin.

29. •Each gland is approximately the size and shape
of an almond, and is composed of secretory
epithelial cells.

30. •The glands secrete tears composed of water,
mineral salts, antibodies, and lysozyme, a
bactericidal enzyme.

31. •The tears leave the lacrimal gland by several
small ducts and pass over the front of the
eye under the lids towards the medial
canthus where they drain into the two
lacrimal canaliculi; the opening of each is
called the punctum.

32. •The two canaliculi lie one above the other,
separated by a small red body, the caruncle.

33. •The tears then drain into the lacrimal sac which
is the upper expanded end of the nasolacrimal
duct.

34. •This is a membranous canal approximately 2 cm
long, extending from the lower part of the
lacrimal sac to the nasal cavity, opening at the
level of the inferior concha.

35. • Normally the rate of secretion of tears keeps pace
with the rate of drainage.

36. • When a foreign body or other irritant enters the eye
the secretion of tears is greatly increased and the
conjunctival blood vessels dilate.

37. • Secretion of tears is also increased in emotional
states, e.g. crying.

38. FUNCTIONS
•The fluid that fills the conjunctival sac consists
of tears and the oily secretion of tarsal glands
and is spread over the cornea by blinking.

39. •The functions of this mixture of fluids include:
•washing away irritating materials, e.g. dust,
grit.

40. •The bacteriocidal enzyme lysozyme prevents
microbial infection.

41. •Its oiliness delays evaporation and prevents
drying of the conjunctiva.
•Nourishment of the cornea.

42. THANKING YOU