Question

:What causes Horner's syndrome in animals, leading to miosis, ptosis, and enophthalmos in the eye?

A) Parasympathetic innervation
B) Trigeminal nerve damage
C) Oculomotor nerve injury
D) Defective sympathetic innervation

Answer 1

Horner's syndrome in animals is caused by defective sympathetic innervation, which can lead to symptoms such as miosis, ptosis, and enophthalmos. A tumor in the thoracic cavity can impact these functions due to its anatomical relationship with the sympathetic nervous system's pathway.

Step-by-step explanation:

Horner's syndrome in animals is caused by defective sympathetic innervation. This condition can lead to miosis (pupillary constriction), ptosis (drooping of the eyelid), and enophthalmos (sunken eyeballs). A tumor in the thoracic cavity could affect these autonomic functions because the sympathetic nervous system's pathway originates in the lateral horns of the spinal cord at the thoracic and lumbar levels, then travels over the apex of the lung and up to the superior cervical ganglion, before reaching the eye. Damage along this pathway can disrupt the normal sympathetic input that controls eye functions such as pupil dilation, which is normally driven by the neurotransmitter norepinephrine. This lack of sympathetic input results in the classic triad of symptoms seen in Horner's syndrome.