Lab 11: Special Senses and PNS

During the lab period (complete in order):

1. Lecture on selected special senses (eye and ear).
2. Cow eye dissection (Lab Manual, pp. 368-369):
   • Get a pair of lab goggles from the cabinet. (Just in case!)
   • When you get your eye, you’ll notice that the part of the eye that you recognize as an eye may be sitting on top of a mound of connective tissue and fat.
   • Make sure that you have a pair of scissors with long blades.
     • There are two types of scissors.
     • I’ll try to remember to separate out the good ones from the not-so-good ones before we begin.
   • Take the pointed blade and jab it into the sclera.
     • This will require a good deal of force and usually makes some unfortunate noises.
     • Once you get the tip in, cut a circular path through the sclera. - Separate the two halves of the eye.
     • The thick jelly-like liquid inside is the vitreous humor.
     • Note the yellowish lens.
       • The lens gets very tough during preservation.
       • Remove the lens to see the following structures beneath and around it:
         • iris
         • pupil
         • cornea
         • ciliary body
     • On the posterior half of the eye:
       • Note the iridescent color of the tapetum lucidum.
         • This is the structure responsible for the ability of animal eyes to glow at night.
         • It is part of the choroid.
         • Humans don’t have this structure.
       • Carefully peel back the tapetum lucidum and the retina.
         • Note the location where the optic nerve meets the retina.
         • This is the optic disc (blind spot).
   • Sadly, the eyes don’t keep well once they’ve been opened, so it’s best to toss them in the biohazard box in the back room.
   • When you clean up:
     • Wash and dry the dissection pans. Leave by the sink.
     • Wash and dry the dissection tools. Return them to the tray.
3. Models
   • Identify the following structures on the eye models in the lab (Lab Manual Fig. 24.3, p. 366):
     • sclera
     • cornea
     • iris
     • pupil
     • ciliary body
     • retina
     • optic disc
     • lens
     • anterior and posterior chambers (segments)
     • extrinsic eye muscles (Lab Manual Fig. 24.2, p. 365)
   • Identify the following structures on the ear models in the lab (Lab Manual Fig. 25.2, p. 384):
     • auricle
     • external auditory canal (a.k.a. external acoustic canal)
     • tympanic membrane
     • ossicles: (Note: The functional model (the one with the liquid inside) shows the ossicles nicely.)
       • malleus
       • incus
       • stapes
     • oval window
     • inner ear structures:
       • vestibule
       • semicircular canals
       • cochlea
     • pharyngotympanic (auditory) tube
4. Identify the following on the model of the spinal cord:
   • gray matter
   • white matter
   • central canal
   • dorsal root
   • ventral root
   • dorsal root ganglion
   • spinal nerves

Next lab: Lab Exam 2

1. Make sure you sign up for a time.
2. Study Martini Fig. 13-11 and be able to identify the six spinal nerves illustrated.
3. Make your final touches to your Histology Notebook.
   • It is due no later than the day of Lab Exam 2 – absolutely no exceptions!
   • It will be graded using the Grading Rubric.
   • You will get it back at the final exam.