Posts Tagged ‘Skull’

Anterior Disection of the orbital cavity

Anterior Dissection of orbital cavity

Moving onto the anatomy side, here is an Anterior dissection of the right eye. Unlike the ears where I started with the smallest bones and worked out. I wanted to start with the eye, from the outside and work inwards. After doing my sketch of my left eye, this seemed the next logical step.

Its a bit of a creepy image as well, which is always a good thing. A bit of a bombardment of new labels to learn, and I was going to write some of them down for you. But, when looking them up I have come across two excellent images relating to the muscles of the eye (obliques and rectus) which I am going to draw next. It also going to tie back to my drawing of the cranial nerves. so watch this space.

The drawing itself, is a bit elongated in my opinion. I think this might be slightly down to how I was copying it , with it being rested on my knee. I also tried a new sketch pad which I got from Rymans. Its called “The artist A4 sketchpad 180gsm” . It might be good for ink, as the paper is quite solid, but I had a real hard time blending on this. You can probably see, not even zooming in, that the blending is quite harsh.

Unlike the cheap boldmere sketching pad, in which I turned its downfalls to my advantage, I cant see this pad being used for much more than doodling. Save your money.

Related Posts:

• Posterior View of the Cranial Nerves
• Anterolateral View Of The Inner Ear
• Surface of the Iris

Megaloceros Giganteus #2

I had one mission in mind when I went to the Leeds City museum, and that was to have another go at drawing the Megaloceros. My orginal sketch from February 2009 is here

It’s interesting rereading the commentary from where I drew it first time round. Where last time I was concerned about proportions, this time  I was far more concerned about the light. The lighting in the room is extremely unnatural – not that you expect to see giant skeletal Megalocerous running around in daylight of course.

The museum lights do throw shadows, which in turn effect the shape of the skull which I found distracting when trying to define the shape. I do feel, I have done far more justice to his jaw this time around, though I do feel I have cheated him on his teeth.

Also of note, where I mentioned in my drawing of the cranial nerves about the cheap pad I used that was extremely smudgy. I actually deliberately used this pad for this drawing, to use that “smudginess” to my advantage.

Related Posts:

• Megaloceros giganteus
• Speed Sketch #5
• Posterior View of the Cranial Nerves

Posterior View of the Cranial Nerves

Posterior View Of Cranial Nerves

Moving away from the ear, my next few posts will be about eyes, but I wanted to first give an idea about the space in which all the aforementioned occupy. In my anatomy books,there are several cross section drawings, of things such as the right tympanic cavity, which is where the middle ears sits and I have got to take my hat off to those folks who do medical illustrations, as I do not feel confident in my ability at the moment to attempt to even do a straight copy of one of these illustrations.

What I did go for in the end was this drawing of the cranial nerves, and as you can see its extremley busy, but trust me, it is tame in comparison to the thympanic cavity. The moment you start adding nerves, muscles, bone it starts getting extremely crowded.

To give you more idea on where we are inside the head, I would suggest you take a look at my Pterygopalatine fossa sketch. We are behind this and I hope its clear in my picture here, that you can see where the skull is, and can picture how that continues to curve round to the pterygopalatine fossa, and of course there is the ear on the right.

Now, take a look at the size of the Incus, compared to a american cent  and take note on my drawing, where I have marked the Mastoid air cells. Everything I have drawn to date with the ear, takes place just above the this and goes from the outer ear, and just past the Sigmoid sinus. Many diagrams of the middle ear will show the Sigmoid sinus on.  Its also interesting to note, if you get an ear infection, those mastoid air cells can get infected, which you really don’t want.  I mention this, to indicate how everything around here is connected.  I hope this description has given you a better picture.

As for the drawing, usual culprit of pencils but new sketchbook, which has shown, shall we say- somewhat interesting characteristics. The sketchbook is by Boldmere, is a 130gsm and cost the grand sum of 99p. It does seem to have the magic ability to blunt any pencil on contact, which has made defining the lines in the drawing somewhat troublesome. The second interesting property it displays, is as regular readers will know, I take great care to avoid finger grease and keep hand contact to a minimum. Even by doing this, I managed to have a hand that was black along one side.

The paper really doesn’t take the graphite that well,its almost like charcoal in some senses, and most of the time during drawing this, I was afraid I was going to end up with a page of black smudge. Thankfully it was bluetac to the rescue.

I have been pondering whether to do a post on the joys I have been finding in using bluetac, but instead I will head you over to this excellent tutorial on the subject by Mike Sibley

Related Posts:

• Anterolateral View Of The Inner Ear
• Anterior Disection of the orbital cavity
• The Ossicles

Anterolateral View Of The Inner Ear

Anterolateral View of the Inner Ear

To finish off the ear (for now!) Here is the Inner ear. You can break the ear down into two main functional parts. There is the Vesitbule which is dedicated to balance, and the Chochlea which is dedicated to hearing.

If we go back to the middle ear for a second, sound waves there have been converted into mechanical vibrations which have then come to the inner ear where the Cochlea then propagates these signals as waves in fluid and membranes and finally transduces them to nerve impulses which are transmitted to the brain. If you have an engineering type chum, ask them about the challenge of converting sound waves into fluid waves and you will get an idea of the complexity of what is going on and thats even before mentioning nerve pulses.

The Vestibule works in conjunction with your sight is responsible for the senses of balance and motion. It uses fluid and tiny hair cells, to get information about attitude, rotation and linear motion of the head, which it converts into pulses and sends to the brain.

Moving onto the drawing, you can see in the top left hand corner a quick rundown of the pencils I used. I’m not entirely happy with the sketch, mainly I think I need a bit of a better reference on the actual surface.

Of interest, I did take some photos of the drawing as I went along, you can see them in the fotki album here (they will be on the last page) and I have added some notes in the photo descriptions. These pictures are also on my flickr stream which you can find from  my previous post.

Related Posts:

• Posterior View of the Cranial Nerves
• The Ossicles
• Ossicles – Incus

The Ossicles

Anterior View of the Ossicles

After sketching all the individual bones, here are all three of them together in situ, but what do they do ? These three small bones (the hammer. The Anvil & Stirrup) carry sound waves from the ear drum to the Cochlea and its a nice bit of mechanics.

First of all, sound waves hit the tympanic membrane (AKA as the Ear Drum) , the vibrations are then carried through the Malleus, Incus and finally the stapes which then takes these vibrations  to the inner ear.   They effectively act as a lever and give a mechanical advantage, by not just the lever effect, but also my reducing the area of force. If the sound waves went direct from the ear drum to the inner ear, they would be a lot  weaker – Its a nice bit of design.

There are also  muscles attached to the ossicles which can control the extent of movement which is believed to protect the inner ear from loud noises. Interestingly  in Bats, these muscles are highly developed and seem to be crucial in their sonar and echolocation senses.

So there you have it  ladies and gentlemen, the Ossicles. As for the drawing itself, I’m not too happy with it. Not just because I used my old pad after the luxury of using the heavier a5 pad, but because  after mentioning last week about looking at other areas when it comes to shading, I started all guns in on the Malleus with a 6B which didn’t really give us much room for shading darker areas afterwards. Thankfully the HB came to the rescue on the Tymponic cavity, but my original intention was to have that darker and the ossicles lighter.

Related Posts:

• Ossicles – Incus
• Ossicles – Malleus
• Ossicles – Stapes