Welcome to the VH Dissector, and to the beginning of your journey in the gross anatomy lab. The VH Dissector is a powerful tool to explore anatomy outside of lab. You can create and bookmark your own dissections, and there will also be modules like this one throughout the year to supplement your labs.
Remove the skin to visualize the structures underneath. In the lab, you will see subcutaneous fat and fascia (connective tissue coverings), but the VH dissector takes us directly to the muscular layer.
These anatomical terms will come up again and again throughout your Human Structure and Function courses, and throughout your career as a physician. Use this module to familiarize yourself with these convenient and universal ways to discuss the human body.
We will now explore the cross-sectional views of the VH dissector. There are three boxes in the cross-section panel. The top is a transverse plane, the middle is a sagittal plane, and the bottom is a coronal plane. The transverse plane is especially useful because many CT scans show this view.
Highlight the Latissimus dorsi muscle and observe that the highlight shows in both the main dissection panel and in the transverse section. Try moving the cross-sections around to see if you can find this muscle in the coronal and sagittal sections!
Here is an example of how to show this structure in all three cross-sections. Notice that moving one cross section affects the others. The lines in each cross-seciton panel can help you orient yourself to the other planes of section.
Now that you have familiarized yourself with the planes of section, focus on the diaphragm which separates the thoracic cavity from the abdominal cavity. Recall that it is formed from contributions from the following mesoderm sources:
Septum transversum (ST-purple) - the part ventral to the gut tube
Visceral mesoderm around the gut tube (pink) - the medial aspects close to the esophageal opening
Pleuroperitoneal membrane (PPM-orange): part that fills in the pericardioperitoneal canals
Parietal mesoderm of body wall (red): forms perimeter of the diaphragm.
bw = body wall
Note: The image above is 180 degrees rotated from the similar image in your IL. Its orientation matches that of the VH dissector cross-section. Use this as a reference as you follow the steps below.
Examine the diaphragm in each of the cross-sectional planes. Grab the sagittal cross-section and watch the coronal cross-section follow as you move the sagittal image up and down. Also observe the transverse cross-section when you release the mouse. Now move the coronal cross-section from side to side as you observe the axial cross-section follow. Also observe the sagittal cross-section when you release the mouse. Do this until you get the sense that the diaphragm is a domed structure with two peaks.
Visualize the structures that pass between the thorax and abdomen.
Aorta: most posterior and inferior
Esophagus
Superior vena Cava: most superior and anterior
This is a prosection showing contents of the dorsal body cavity including the cranial cavity and vertebral canal.
Recall that somites are blocks of mesoderm located on either side of the neural tube in the developing vertebrate embryo. Somites develop uni-directionally in a cranial to caudal direction and are pivotal in the establishment of the body plan as they eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae.
Determine the pathway of developing blood vessels that will supply cells of somite
Blood vessels provide a migratory “scaffold” for the motoneurons to extend towards the developing myotome/skeletal muscles of the trunk and (eventually) limbs.
Use the VH Dissector to view the results of this process of segmented development:
Correlate what you see to the figure from your Embryology IL:
In the reconstructed VH dissector body it is not possible to see the layers of skin and fascia, but it is well visualized in the sectional anatomy. One place where the division between superficial and deep fascia can be appreciated is in the thigh.
Here the transverse and coronal planes have been overlaid on the 3D reconstruction.
Zoom in on the sectional views. Note that two structures have been highlighted. The iliotibial tract (deep fascia of the thigh) in purple and the tensor fascia lata muscle (a muscle that pulls on the iliotibial tract) in pink.
Use the middle pane (sagittal section) to move the coronal plane anterior and posterior, and the transverse plane superior and inferior. This will help you appreciate how the deep fascia envelops the muscles of the thigh, and is especially thick laterally.
The skin and the superficial fascia (hypodermis) can be seen superficial to the deep fascia.
More and more research is demonstrating the important role of fascia in musculoskeletal health. Although the process of dissection allows you to appreciate the extent of the fascia, it necessarily must be destroyed in order to separate out and reveal the nerves, vessels, muscles and organs being studied.
The VH dissector cross-sections can be used to visualize this fascia and appreciate its contributions to the compartmentalization of and connectivity between organs.
VH Dissector steps modified for Drexel Dissector by Haviva Goldman, PhD, Dr. Noel Goodstadt, DPT and Sophie Geagan (MD student) from original website activity created by Jeffrey Fahl, MD, Kyle Petersen, PhD, Richard Drake, PhD, Alesha Petitt, MA, Claira Ralston, MS and Kim Price, MA and modified by Jeffrey Fahl, MD, Michael Smith, PhD, Albany Medical College.