Wednesday, September 26, 2012

Skull puzzle

The folks at Visible Body are offering a FREE mini eBook that clearly illustrates and summarizes the 22 bones of the skull. 

This handy little gem will help you get started studying the bones of skull and provide a valuable addition to your set of  study resources.  The three dimensional views of the skull will help give you a deeper understanding of the structure of the skull.

It also gives you an introduction to Visible Body's computer-based anatomy study tools.

Check it out at

Wednesday, September 12, 2012

Blood viscosity and peripheral resistance

Learning about all the factors that affect blood flow can be daunting.  One of the tough things about it is trying to visualize how all the factors influence blood flow.

One factor affecting blood flow is peripheral resistance.  This is the resistance to blood flow in the peripheral vessels . . . the arterioles.

What kinds of things can cause blood to "resist" flowing as freely as possible?  Well, one factor is the viscosity of blood.  One way to think of viscosity is "thickness" of a fluid.  What makes blood thick?  One factor is how concentrated the red blood cells (RBCs) are in each drop of blood.  Is is often expressed as the PCV (packed cell volume) or hematocrit of blood.  The more blood cells there are in a drop of blood, the thicker--or more viscous--the blood is.  And the more it resists flow.

An analogy we can use to visualize this rather abstract concept is any of the classic TV commercials once used by Heinz to promote their ketchup.  Heinz claimed that their ketchup is better than other brands because it has more tomatoes per bottle of ketchup.  And that, presumably, can be demonstrated by the comparative thickness of their ketchup.  In other words, Heinz ketchup is more viscous than some other brands of ketchup.

As the commmercial below demonstrates, the extra thickness  or viscosity of Heinz ketchup means that it will flow at an incredibly slow rate.

So to summarize this analogy:
  • More tomatoes per bottle of ketchup make the ketchup thicker, or more viscous. The higher the viscosity of ketchup, the more it resists flow and thus the slower it will flow out  the narrow neck of a tipped bottle.
  • Likewise, more RBCs per drop of blood make the blood thicker, or more viscous.  The higher the viscosity of blood, the more it resists flow.  This resistance can be significant where the blood vessels narrow at the peripheral vessels called arterioles.

Wednesday, September 5, 2012

Planes of the body

In a previous post, I addressed that initial struggle with anatomical terminology when beginning a course in anatomy & physiology.  In this post, I'll pick up with another early--but essential--set of concepts: planes of the body.

As with any concept of A&P, one shortcut to understanding is to connect the concept to something simple that you already know about.  Let's see how that could work with anatomical body planes.

For planes of the body, think of them as ways you could slice the body if you had a big giant saw like illusionists use to saw people in half.

If you saw a person so that there is a top part and bottom part of their body, then you’ve cut along a TRANSVERSE or HORIZONTAL plane.  Either term can be used. They both mean the same thing.  It doesn’t have to be equal top and bottom halves . . . ANY separation of top and bottom is a cut along a transverse plane.

If you saw a person into left and right pieces, you are sawing along a SAGITTAL plane.  The word sagittal literally means “relating to an arrow” used in archery.  So imagine shooting an arrow into an apple that is sitting on top of my head . . . and then imagine the apple falling apart into a left and right piece as the arrow slices through it.  That’s a sagittal cut . . . a cut along a sagittal plane.

If the sagittal plane is exactly in the middle, dividing the body along its midline into equal left and right halves, we call that plane a MIDSAGITTAL plane.  If instead the plane is off to one side or another, splitting the body into unequal pieces, it’s simply called a SAGITTAL plan.

If you saw a person into front and back pieces, you are cutting along a FRONTAL plane or CORONAL plane. 

Again, seeing this visually is a good idea. 
  • First, study the images of body planes in your A&P textbook and lab manual. If you are using one of my textbooks or manuals, you can find a handy diagram  of the planes of the body just inside the front or back cover.    By looking at many different diagrams, you'll get a better understanding of the essential concept of body planes . . . as well as plenty of practice.
  • Try constructing a three-dimensional "paper doll" model that resembles the diagram shown here.  Or any kind of simple, hands-on model.  Such activities may seem like a childish project, but it engages many parts of your brain and thus strengthens your learning . . . and your memory.
  • Here's a great YouTube video outlining the concept of body planes:

  • You may find this FREE mini-course to be helpful.  It's called simply Anatomical Directions and it's provided as a free service from Insight Medical Academy. It requires a free registration to use the course, so be sure to register before trying to access the course.  Here's a brief video explaining how the free course works.