- Describe the gross anatomy of the spinal cord and identify its regional variations.
- Identify the level and gray and white matter regions of the spinal cord on the cross-sectional images.
- Identify the anatomical features of the vertebrae and sacrum.
- Identify the bones of the thoracic cage and their anatomical features.
- Identify and describe the function of the muscles of the back and abdominal wall.
Terms to Know
Spinal Cord Gross Anatomy
Muscles of the Trunk Wall
Bones of the Thoracic Cavity
In this lab, you will be examining the spinal cord, vertebral column, bones of the thoracic cage, and the abdominal wall. The spinal cord serves as the connection between our peripheral nervous system and the brain. The central region of gray matter is primarily composed of cell bodies and unmyelinated axons. The outer region of white matter is composed mainly of myelinated axons ascending, carrying sensory information, to the brain, or descending, carrying motor information, from the brain to the target tissues.
The vertebral column supports the body’s weight and helps transmit forces between the upper and lower extremities. The muscles of the abdominal wall act on the vertebral column to create movements such as lateral bending, rotation, flexion, and extension at the trunk. These muscles are also constantly working to stabilize the trunk and vertebral column both with movement and at rest. The bones of the thoracic cage connect directly or indirectly to the thoracic vertebrae and together form a protective “cage” around the thoracic and some abdominal organs.
This is the first lab during which we will examine human cadaveric tissue. In this lab, you will examine spinal cord. You will also view abdominal wall musculature on a cadaver. Please be respectful and appreciative of the gift our donors have given. Handle the tissue with great care!!! Be very gentle when moving the tissue to examine the various structures.
Now explore the bones of the thoracic cage. Under Systems and Skeletal System Views, click on 9. Thoracic Cage.
Today you will be able to view some of the structures of the trunk wall on the cadaver. The cadaver will be in the prone position, so only posterior and a portion of the lateral structures will be visible in this lab. In lab 3, the cadaver will be in the supine position, and you will be able to view the other structures of the trunk wall at that time.
Observe the erector spinae muscles. These muscles are deep to the latissimus dorsi and trapezius muscles. Spinalis is relatively thin and medial, closest to the spine. Longissimus is the longest of the erector spinae muscles. Iliocostalis is the most lateral of the three erector spinae muscles and runs from the iliac crest of the pelvis to the ribs (costals). When these muscles contract bilaterally, they extend the spine and help to maintain upright posture against gravity. Unilateral contraction contributes to lateral flexion. You can also observe the external oblique running anteriorly on the lateral aspect of the abdominal wall. This muscle rotates the trunk to the opposite side and assists with lateral flexion.
If you have time, try carefully arranging the vertebrae in anatomical order from superior to inferior. First, separate the vertebrae into the appropriate groups by examining them and observing their unique features. Try to make your first attempt without looking at the atlas. Do not worry about having each vertebra in the exact spot it belongs. For example, you won’t be able to distinguish T9 from T10. Just do your best to put them in the correct order based on shape and size.
Lab Activity 6: Ribs & Sternum
Using the bones and the standing articulated skeleton, examine the true, false, & floating ribs. Also, observe the costal cartilage connecting the sternum and ribs. This is best seen on the standing skeleton.
Examine the following bony landmarks:
- Articular facet of the transverse process (on the thoracic vertebrae)
- Xiphoid process (may not be present in the set of bones)
- Suprasternal notch
- Clavicular notch
- Sternal Angle
These structures may be difficult to identify on the isolated sternum. Try to palpate these structures on your own sternum. At the superior aspect, palpate the suprasternal notch. As you move about two inches inferiorly, you can feel the sternal angle, where the manubrium meets the body. Just lateral to the sternal notch, you can palpate the sternoclavicular joint and sternoclavicular notch, where the sternum articulates with the clavicle (collarbone).
Take a rib and two adjacent thoracic vertebrae & examine the articulations of these three bones. Notice how the superior demifacet of the inferior vertebrae & inferior demifacet of the superior vertebrae form one full facet articulating with the rib head. Notice the costal facet on the transverse processes of the thoracic vertebrae.
Lab Activity 7: Radiology of the Vertebral column, thoracic cage, and spinal cord
View the slideshow on the computers identifying the anatomy of the vertebral column, thoracic cage, and spinal cord in radiology images. The unlabeled images are also provided on canvas as a study tool.