Lab 2 navigation
Sacrum
■Sacrum (5 fused vertebrae)
■Promontory
■Alae (singular is Ala = “wing”). There are two of these, on either side of the promontory
■Anterior and posterior sacral foramina
■Sacral canal
■Sacral hiatus
■Coccyx (4 vertebrae fused into 1-2 pieces)
Figure 2.7. Sacrum and coccyx, anterior view. From Gilroy, Atlas of Anatomy, 2nd ed., Illustrator: Karl Wesker, ©2018 Thieme Medical Publishers, Inc. All rights reserved.
Figure 2.8. Sacrum and coccyx, posterior view. From Gilroy, Atlas of Anatomy, 2nd ed., Illustrator: Karl Wesker, ©2018 Thieme Medical Publishers, Inc. All rights reserved.
Joints of the Vertebral Bodies
Study these on an isolated cadaver vertebral column specimen.
■Adjacent vertebral bodies are joined together by intervertebral discs—producing an intervertebral joint. Each of these joints is technically known as a symphysis. An IV disc also joins L-5 to the sacrum.
Question
What is the definition of a symphysis? Hint: it is defined by its cartilage.
IV joints firmly unite the vertebral bodies and prevent them from moving on one another. They also function to absorb and dissipate forces transmitted along the vertebral column.
Each IV disc has two parts:
■Annulus fibrosis: Composed of rings of fibrocartilage
■Nucleus pulposus: The super-hydrated gelatinous core of the disc
Figure 2.9.
Question
Do you recall the embryonic origin of the nucleus pulposus?
Also, locate these features on the spine specimen:
■Intervertebral foramina: These transmit spinal nerves
■Dura mater
■Epidural space
Question
What is a herniated disc? In which direction do disc herniations usually occur? Why? What is the neurological danger?
Joints of the Vertebral Arches
■Zygapophyseal (facet) joints: Articulations between superior and inferior articular processes of adjacent vertebrae. These are plane joints that allow gliding movements. Locate these on the skeleton in lab.
Degenerative changes in facet joints are common sources of back pain.
Note
Although only a small amount of movement is possible at an individual facet joint—together, the joints allow flexion, extension, lateral bending, and rotation of the vertebral column.
Craniovertebral Joints
■Atlanto-occipital joint: The articulation between C-1 and the skull (condyles of the occipital bone).
■Atlanto–axial joint: The articulation between C-1 and C-2.
Question
These joints facilitate movements of the head on the spine. What are these? [Don’t shake your head—you got this!]
Ligaments of the Vertebral Column
Study these on an isolated lumbar spine cadaveric specimen.
Ligaments of the vertebral column
Two longitudinal ligaments run vertically along the anterior and posterior aspects of the vertebral bodies—from skull to sacrum.
■Anterior longitudinal ligament: Limits spine extension (prevents hyperextension) and anterior movement of IV discs
■Posterior longitudinal ligament: Limits spine flexion and posterior movement of the IV discs.
Another ligament is segmental and runs between the laminae of adjacent vertebrae.
■Ligamentum flavum: best seen within the vertebral canal. They contain an abundance of elastic fibers—this gives the ligament a yellow color (thus the name!). They limit flexion of the spine and provide recoil to return the spine to vertical after it has been flexed.
Figure 2.10. Netter, Atlas of Human Anatomy, 7th ed., Plate 168.
Figure 2.11. Netter, Atlas of Human Anatomy, 7th ed., Plate 168.