Critical Thinking in Physiology: Posterior
You have practiced tracing, and some exercises on controlling your pencil and also shading types
For each session you will be given tasks to improve three elements of your critical thinking;
- Knowledge of cardiac anatomy
Copying grids onto paper (especially if you don’t have a printer or its broken)
Using shapes and negative spaces to define the shape
Working on your shading and tonal ranges using a variety of different pencils
Content assembly to create a study page
Label the posterior side of the heart- including dots
There is a lot of emphasis on your drawing skills this week and also the creation of study pages; what are they and how do you make a good one.
Posterior STRUCTURE- gross anatomy
Using an HB pencil
Make lightweight preparatory sketching marks first to plot the basic dimensions, these marks can be removed later.
Think about the basic shapes within the subject that you are trying to portray by identifying simple geometric shapes. Take some measurements of the subject, such as height and width.
How do you go about drawing something accurately without a tracing?
Tips for accurate drawing
When drawing make sure that your drawing makes sense, for example: the pulmonary vein should seem like it sits over the inferior vena cava. When looking at the coronary circulation, the vessels should be connected with no gaps.
One thing that looking at the heart structure does tell you is how compacted everything is. Nothing sticks out or is obtrusive on the anterior or posterior surfaces. The image in this session has been fixed in formaldehyde and is not ‘fresh’
Observe: (For dissections)
- From a real dissection: Measure: the height, width and widest point of the heart and vessels
- Identify the various shapes you see in front of you e.g. oval, rectangle round
- Identify large structures you can see
- From a picture with a grid: As for live dissection but after measuring height and width draw a box to contain the heart
- Alternatively transpose the outside perimeter of your grid onto your own paper, ensuring the scale is an easy one to translate i.e: a grid of 4×4 can be 4cm2, 8cm2 or 16cm2
- Draw faint lines that show the various structures and their places within the grid check that it is correct
- Draw the outer margin paying careful attention to any shapes you see and paying attention to negative spaces
- Do not feel that you need to draw every structure just yet, this will look un-natural, instead draw just those things that are obvious to the naked eye.
Images of grids and negative spaces
Reference image to copy
Use the images here with and without grids to help you draw accurate representations of the image
- The best way to measure the height and width of a subject is to use either a transparent ruler held next to the subject, you can also use calipers also the simple method for estimating proportion can be done is using your thumb held against your pencil. Hold the pencil vertically at arms length and close one eye, use your thumb on the pencil to gauge the height and width move the pencil around to find and observe the angles
- Alternatively- place a grid or marker against the image on your computer- so that you can transpose the lines to scale.
- Try to think about the subject sitting within a more formal shape (into either rectangular, triangular or square shapes. so that what you are looking at fits
- When drawing always begin by lightly plotting in the shape that the subject sits within (into either rectangular, triangular or square shapes.
- Make light pencil marks initially.
Use your pencil and thumb to judge the angles of the subject and any curves.
- If there are overlapping features, draw the subject in the initial sketches as though all parts are transparent, this is called a ‘skeleton drawing’ which enables you to see how parts are connected and reduces the possibility of alignment errors with overlaps.
- So far we have discussed drawing ‘only what you see’ so this might seem a little contradictory at first but in this case you are simply drawing all of the overlying parts. This approach will help you to gain a better understanding of the perspective and achieve better connections and continuation between vessels and chambers of the heart and you will have the peace of mind of know that your drawing makes sense!
- All too often potentially good work is ruined by misaligned lines
Light and shade is one of the most important areas of drawing (Chiaroscuro). The way that the light falls on a subject creates volume.
When the colour images of the hearts are made black and white, notice where the light source is.
You then notice that it isn’t just black and white but various shades of grey (a range of tonal values).
Therefore, before moving on to further shading (tonal drawing and form) spend some time observing and understanding what creates different shades and shadows (tonal values) in a subject. In order to understand these we need to think about the form (shape) and the way that it interacts with a light source.
These can be broken down into :
Highlights, which is where the light catches the subject most dramatically and the effect bleaches out tone, we can often leave this area white when shading.
Mid tones are all light to medium grey tones and cover a large area.
Dark tones- which are on the shade side of the subjects and this creates form shadows, which are dark grey. When a subject is lit in this way you can usually see some reflected light too. Reflected light is the light that bounces off other nearby
surfaces onto your subject, it is always darker than the highlight but is lighter than the most shaded areas of the subject. In this case it sits beneath the form shadow.
Start to look at your images in this way.
Start with a light shade and create a foundation (2H).
Leave the whitest parts without any pencil
Progressively use darker and darker shades until you get to a 6B.
Checkout this link to a previous video where I examined the posterior structure
Hopefully after a bit of work you should have identified through observation alone those gross anatomical structures
The big ones are covered in dots and you many not know all of them …..
1.Auricle on left atrium
2. Coronary Sinus in posterior atrioventricular groove
3 Great Cardiac vein and anterior intraventricular branch
4. Great Cardiac vein and circumflex branch of coronary artery
5. Inferior left pulmonary vein
6. Inferior right pulmonary vein
7. Inferior vena cava
8. Left Atrium
9. Left Pulmonary Artery
10. Left Ventricle
11. Middle Cardiac vein
12 Posterior Vein of left ventricle
13. Right atrium
14. Right Pulmonary Artery
15. Right Ventricle
16. Superior Left Pulmonary vein
17. Superior right pulmonary vein
18. Superior vena cava
Creating a study page
The purpose of a study page is as follows:
- A study page is simply a collection of drawings illustrating the component parts of our organ with some written notes about it. It is your visual annotated research which deconstructs the organ. The purpose is to ensure that you fully understand your subject before undertaking a full tonal study of it.
- A study page is also where you work out your approach to a final drawing, e. g. tonal technique and grades of pencil. It can contain small sections of finished drawings and line drawings. It doesn’t need to be perfect but is a place to work out ‘how to draw’ your subject.
Here are some points to consider when creating your study
Research Once you have selected the major viewpoint of your organ (this week its posterior) , you can start to collate reference material, look in books and online to see what you can find out about the posterior side of heart. Identify any structures that are visible, and also any interesting facts, learn about the story of the heart- (who first discovered what went where?). Make notes and rough sketches initially.
Take photographs produce a photographic reference library, black and white photographs are particularly useful for pencil work because they can help you to identify the tonal differences across the organ. Creating reference material in this way is good practice and can be referred to for your final piece. It is advisable to keep photographic reference in a folder on your computer or on a drive.
Observation – is the key to success keep using text books
Measuring and identifying characteristics
–If you have a your heart specimen in front of you (ie during the dissection class) take measurements of it, identifying the basic shapes and characteristics. A few points to consider
Lenth from apex to aorta. Width of heart. Length of aorta, and other major vessels the length and shape of vessels
Draw– use a combination of line and tone, and a range of pencil grades to allow you to achieve the correct tonal values. If you created a tonal strip, you can use this to identify tone
Positioning & composition– Understand the key morphological features understanding of these components will help you to identify the best positioning for your final composition. Look at the lines, curves and shapes – does it make a good clear illustration? Ideally, drawings should be made from different positions, such as front, side and back. Remember that the final composition (lesson 5/6) needs to be accurate, balanced and aesthetically pleasing, so creating a good balance between these requirements is important.
Clarity – Always ensure that definition between parts is clear and that there are no areas of uncertainty.
Lighting and Tonal Values Light your subject well, and keep the lighting consistent in in all parts drawn when shading.
Review.When you have finished your initial studies, sit back and think about whether you have everything that you would need to produce a finished drawing. is anything missing?
Reflecting on your Progress
Please answer the following questions:
At this point you should reflect on your progress. Are there any specific areas of the exercises that you found difficult or overly challenging?
Is there any help or resources that would have liked to help you with these exercises, or are the resources provided satisfactory?
You should now have a complete page, tracings, and annotations with notes. Do remember to date it. When you have done so, upload a PDF or photo of your work into the forum AND email to me
Enter your work here
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Critical Thinking in Physiology:Cardiac anatomy
For the next session on the interior of the heart (right ventricle) click here