Form and Function

I have a passing interest in graphic and web design and just could not look at that plain blogger template anymore. One pre-made template featuring Johnny Depp in Pirates of the Caribbean had its obvious charms, but I settled on (hopefully more scholarly) flowers.

Going through the bones of the skull (zygomatic bone, parietal bone, sphenoid bone...) I'm starting to feel like Harlan Pepper in Best in Show, recounting his childhood talent of naming "every nut that there was" - " Peanut. Hazelnut. Cashew nut. Macadamia nut".

Why should what is mostly one solid mass have so many freaking bones, anyway? Oh right, to protect our mushy brains. I'll take that excuse under consideration.

Every time we learn new information, the opportunity arises to see our usual world in a new way. I've had a few experiences cast in a fresh light since taking this class and have a short list of items that will tell you "You Know You're in A&P When...". I only have 3 items in the list so far, but hopefully I can add on as the semester progresses.

You Know You're in A&P When...

...Your new favorite words are lambdoid and phalanges.
...You correct your doctor when she holds her hands over the wrong side of her body when gesturing toward the liver.
...You specifically curse your eccrine glands as your sweaty foot slides across your yoga mat yet again.

I had to laugh when we were assigned an entry on "anatomy in art" because I found this when searching for anatomical images weeks ago:

My search brought up this art exhibit summary on boingboing.net:

"This Korean art exhibition explores the fictional anatomy of cartoon characters, with elaborate faked-up skeletons for Looney Toons characters, anatomical drawings of Mickey and friends, and many other artifacts from the study of toon anatomy."

Despite a history with both vertebrate biology and, you know, childhood, it took me a minute to be sure that that the imagined skeleton seen here is indeed that of Bugs Bunny. Here's a link to more of the show.

As a doula I've seen a lot of benefit from the use of Transcutaneous Electrical Nerve Stimulation (TENS) for decreasing the intensity of labor pain. A TENS unit is a small battery-powered system that sends a mild electrical current along lead wires to sticky electrode pads that are placed on the body on either side of the mid-sagittal plane in the area that is experiencing pain. The electrical stimulation runs between the electrodes creating a buzzing feeling in the skin and, if turned up to higher levels, some involuntary muscle contraction. I've long understood that the stimulation works based on the "Gate Control Theory of Pain" by competing with pain reception in the brain, but decided to go digging for the details on how and why this theory explains the benefit of TENS use.

I found these lovely diagrams on Wikipedia and managed to decipher the explanation sufficiently (would have probably been easier to do after neuro A & P but oh well) to satisfy my curiosity, and I am including the explanation as follows.


Part One: No Competing Stimulus
In this diagram, stimulus (represented by the lightening bolt) is carried along a C fiber (which is specialized for pain reception) and arrives at the projection neuron which then passes the message along unimpeded toward the brain, resulting in the experience of the sensation of pain.

Part Two: With Competing Stimulus
Pain stimulus is carried along the C fiber to the projection neuron. At the same time, non-painful stimulus (in this example the buzzing sensation generated by the TENS) is carried by a A β fiber to both the projection neuron and an inhibitory interneuron. Firing of the inhibitory interneuron inhibits firing of the projection neuron, and no stimulus signal is sent to the brain, essentially closing the "gate" by which pain signals were being sent and thereby reducing the overall experience of pain. Presumably not all inhibitory interneurons are being fired by the competing stimulus and some sensation of pain is still experienced.

I'm not really able to duplicate my Venn diagram from class, but here is a list of the similarities and differences we came up with for ET and CT.

Similarities
Both include protection as one of their functions
Each has at least some origin in the mesoderm
Each has a nonliving component (basal lamina for ET, ground substance and fibers for CT)

Epithelial Tissue
Innervated
Avascular
Originates in all 3 embryonic layers
Functions: secretion, absorption, filtration, excretion, sensory reception
Cells are tightly packed and closely bound
Polar due to apical and basal surfaces
Highly regenerative

Connective Tissue
Only some types innervated
Varying degrees of vascularity
Originates entirely in the mesoderm (mesenchyme)
Functions: binding, support, insulation
Some cells are sparsely distributed and unbound
Non-polar
Highly, moderately, or poorly regenerative

I believe I understand all the concepts presented in class content so far with the main challenge being the sheer quantity of information to remember. I swear I have a mental block or some sort of profound aptitude problem relating to chemistry but the review went off pretty smoothly, so fingers crossed for that portion of the exam. I've started review of the anatomical names and body cavities from Chapter 1 and at the moment am working my way through the study guide for Chapter 4 while tissues are still fresh in my mind.

A belated posting of my muddiest point from last week's class on Tuesday. I actually shared confusion on the same question that was raised in class on filtration as a form on passive diffusion. I'm pretty sure I got it cleared up with the drawing that went on the board. A fluid can be moved through a membrane at the location where the vessel that holds it moves from a smaller to a larger diameter because of the increased pressure applied to the fluid in the narrower portion of the tube. If that's not correct then I'm still muddied...