Eye (Oculus / Ophthalmos)

Multiple Choice Questions (MCQs)

1. What is the main function of the eye? a) To regulate blood circulation
   b) To function as a biological optical instrument
   c) To support the skeletal system
   d) To assist in digestion
   Answer: b) To function as a biological optical instrument
2. What is the optic axis angle in horses?
   a) 20º
   b) 35º
   c) 40º
   d) 50º
   Answer: c) 40º
3. Which species has an incomplete bony orbit completed by an orbital ligament?
   a) Horse
   b) Ox
   c) Dog
   d) Sheep
   Answer: c) Dog
4. What is the function of the levator palpebrae superioris muscle?
   a) Moves lower eyelid
   b) Moves upper eyelid
   c) Constricts the pupil
   d) Moves the eyeball laterally
   Answer: b) Moves upper eyelid
5. Which cartilage type is found in the third eyelid of horses?
   a) Hyaline
   b) Elastic
   c) Fibrocartilage
   d) Osseous
   Answer: b) Elastic
6. What is the primary function of the lacrimal apparatus?
   a) To supply blood to the eye
   b) To control eyelid movement
   c) To produce and drain tears
   d) To regulate light entry
   Answer: c) To produce and drain tears
7. Which cranial nerve supplies the superior oblique muscle of the eye?
   a) Oculomotor (CN III)
   b) Trochlear (CN IV)
   c) Abducent (CN VI)
   d) Facial (CN VII)
   Answer: b) Trochlear (CN IV)
8. What is the function of the periorbita?
   a) Secretes tears
   b) Forms the retina
   c) Encloses and supports the eyeball
   d) Controls extra-ocular muscles
   Answer: c) Encloses and supports the eyeball
9. Which of the following is NOT a part of the external fibrous tunic?
   a) Cornea
   b) Sclera
   c) Choroid
   d) None of the above
   Answer: c) Choroid
10. What type of gland is found in the lacrimal apparatus of pigs?
    a) Serous
    b) Mucous
    c) Mixed seromucous
    d) Endocrine
    Answer: b) Mucous

Fill in the Blanks

1. The __________ is the space between the eyelids when they are open.
   Answer: palpebral fissure
2. The optic axis angle in pigs is __________ degrees.
   Answer: 35º
3. The fibrous sheath enclosing the eyeball and its associated structures is called __________.
   Answer: periorbita
4. The __________ tunic of the eye consists of the retina and optic nerve.
   Answer: internal nervous
5. The trochlea is a pulley system associated with the __________ muscle.
   Answer: superior oblique

True or False

1. Herbivores have laterally positioned eyes to enhance depth perception.
   Answer: False
2. The retractor bulbi muscle functions to retract the eyeball.
   Answer: True
3. The third eyelid contains a Harderian gland in all species.
   Answer: False
4. The lacrimal gland is responsible for producing tear fluid.
   Answer: True
5. The levator anguli oculi medialis muscle is absent in oxen.
   Answer: True

Subjective Questions

1. Explain the differences in eye position between carnivores and herbivores and their functional significance.
   Answer: Carnivores have forward-facing eyes, allowing for binocular vision, which enhances depth perception and aids in hunting. Herbivores have laterally positioned eyes, increasing their field of view to detect predators, though this sacrifices depth perception.
2. Describe the structure and function of the conjunctiva and its role in eye protection.
   Answer: The conjunctiva is a mucous membrane covering the internal surface of the eyelids (palpebral conjunctiva) and the anterior part of the eyeball (bulbar conjunctiva). It forms the conjunctival sac, which helps lubricate and protect the eye from dust, debris, and infections.