Special Senses Flashcards
Q8: What flows through the scala media? Where is it produced?
Endolymph. Stria vascularis.
Q9: What disease is associated with overproduction/ineffective resorption of this fluid (endolymph)?
Ménière’s disease.
Q10: Which fluid flows through the membranous labyrinth/ducts and which through the bony labyrinth?
Endolymph and perilymph.
Q1: What do these glands secrete (accessory glands of the eyelid)?
what about the other glands of the eye
Tarsal glands (of Meibohm) and the sebaceous glands of the eyelashes produce a sebaceous secretion that retard the evaporation of tear.
The apocrine glands of the eyelids may produce pheromones and secretion to retard tear. In general, apocrine glands are involved in “emotional sweating”, as they respond to on to an increase in adrenaline levels induced by anxiety, stress, fear, sexual stimulation, and pain.
The eccrine glands produce sweat for thermoregulation.
The lacrimal glands , upper eyelid only, produce tear that contains antibacterial and anti UV agents.
Q2: What are the innervations and functions of these muscles in eyelid?
The orbicularis oculi muscle is a muscle of facial expression, innervated by the facial nerve, consisting of circularly-oriented skeletal muscle fibers overlying the tarsal plate.
The levator palpebrae superioris is a skeletal muscle (innervated by the occulomotor nerve). This muscle is not readily visible in your section, but you can see its dense connective tissue tendon running between the orbicularis oculi muscle and the tarsal plate. Follow the tendon away from the eyelashes, and you will see some of these longitudinally oriented skeletal muscles.
Superior tarsal muscle (of Müller) is smooth muscle (innervated by postganglionic sympathetic fibers from the superior cervical ganglion) that can be seen in this section just above the tendon of the levator palpebrae at the fornix. If you trace the course of the smooth muscle fibers, you’ll see that they follow the curvature of the conjunctiva and insert into the upper margin of the tarsal plate (near the lacrimal glands of Wolfring). As these two muscles are the only means by which the eyelids are held open, lesions affecting either the occulomotor nerve or sympathetic innervation (e.g. Horner’s syndrome) will result in a noticeable drooping of the eyelid, a condition known as ptosis.
Q3: What type of cells make up the mucous membrane of the palpebral conjunctiva?
Stratified columnar epithelium with goblet cells (sparse in this specimen) that contribute mucous secretions to the tear film. The conjunctiva continues along the interior surface of the eyelid and then makes a sharp turn at a region known as the “fornix” to reflect onto the surface of the eye where it then becomes continuous with the outer epithelium of the cornea.
where is the pupil
It is located in the center of the iris.
development origin of the eye
Neural ectodermal origin includes the optic nerve, pigment epithelium and retina.
The lens is derived from the ectoderm.
The sclera is derived from the mesoderm.
Q6: What types of glial cells would you find in the optic nerve? Can it regenerate after injury?
Oligodendrocytes. Oligodendrocytes do not support regeneration of nerves.
Q7: What is the photoreceptor:ganglion cell ratio at the fovea?
which cell layers moved ?
It is close to a 1:1 ratio of ganglion cells to photoreceptors, to allow for very fine discrimination of colors and details. Most cells of inner nuclear layer and the ganglion layer are moved to the margins of the fovea (to the macula) to allow for the light to enter the cone layer with little refractory distortion. The sparse nuclear layer is made of the remnants of the inner nuclear layer and the ganglion cell layer.
