Words For Monday: Hystricognathi, Scuiridae and Myomorpha; Chalazion, Hordeolum and Sty

Last week in the comparative anatomy class we looked at a South American porcupine skeleton. These animals belong to the rodent infraorder hystricognathi, which also includes guinea pigs. In hystricognathi, part of the masseter muscle passes through the infraorbital foramen. Bizarre, I know.

And Scuiridae is a family of rodents that includes squirrels. So instead of remarking that someone is acting squirrely, one could say a person is 'scuiridy.' Of course, no one would have the faintest clue what you were talking about. Except me.

Myomorphs are a suborder of rodents that contains mice, rats, hamsters and gerbils among others. Their medial masseter muscle passes through the eye socket. I am not entirely sure how this is different than hystricognathi, but I think it is because the entire masseter muscle passes through the infraorbital formaen. At any rate, it is unique among mammals according to Wikipedia.

Meanwhile, in ruminant anatomy we learned that the dental arcades are called 'anisognathous' because they do not wear evenly, creating sharp point on the outer upper and inner lower teeth. I believe horses also have anisognathous dental arcades as they get their teeth 'floated' too.

Among other tidbits contained in my notes in this section is this: "Tongue is considered an 'organ meat' and is offered as a dressed organ at the time of butchering." I know some Native Americans prized buffalo tongue and next time some is available at the Ithaca Farmer's Market I plan to try it.

Ruminants have a groove running across their tongue (horizontally, not longitudinally!) partway down the tongue, the fossa linguae, that is the junction of the apex and torus of the tongue. I will be sure to locate the fossa linguae when I get my hands on some buffalo tongue.

Tomorrow we are studying and dissecting the ruminant eye. I really like the eye.

I've learned from reading my notes that the limbus is the junction of the scleral and corneal components of fibrous tunic of the eye. And that the space between the palpebral and bulbar conjunctiva is the conjunctival sac. My notes give this interesting tidbit: "Grazing and browsing animals are subject to foreign bodies lodging in the conjunctival sac. Excessive tearing, blepharospasm or discharges may result."

The next paragraph continues: "Small openings are associated with the margins of the upper and lower eyelids. These are the openings of the tarsal glands that secrete an oily substance that contributes to the tear film [helps prevent evaporation of the tear film]. Small sebaceous and sweat glands are associated with the eyelashes and unicellular mucous glands line the palpebral conjunctiva. Any of these glands may become inflamed and/or blocked. The resulting swellings are called a chalazion if they involve the tarsal glands and a hordeolum, or sty, if they involve the lid margin."

In human medicine a chalazion is also called a meibomian gland lipogranuloma apparently. Kind of makes sense since in human med the tarsal gland is the meibomian gland.
Got to love human med, where everything is named after someone. According to Wikipedia, a stye or hordeolum is "an infection of the sebaceous glands of Zeis at the base of the eyelashes or an infection of the apocrine sweat glands of Moll."

Apparently styes are smaller and less likely to cause lasting damage. One frequent cause of chalazia in people (not cows!) is not properly removing eye makeup which then gathers in the tarsal gland and leads to the formation of a cyst. There are times when I am glad that I don't wear makeup!

So many new words every day now. It's enough to make one's head spin.