Podcast
Questions and Answers
What evolutionary process, described in the text, leads to the retention of juvenile characteristics in the adult form?
What evolutionary process, described in the text, leads to the retention of juvenile characteristics in the adult form?
Neoteny
What type of embryonic tissue do somites originate from?
What type of embryonic tissue do somites originate from?
Paraxial mesoderm
During the mesenchymatous stage of vertebral development, what three structures are formed from the migration of sclerotome cells?
During the mesenchymatous stage of vertebral development, what three structures are formed from the migration of sclerotome cells?
Perinotochordal sheath, neural arch, costal element
What is the main driver of vertebral segmentation?
What is the main driver of vertebral segmentation?
In relation to somites, where do the intervertebral discs form in the developing vertebral column?
In relation to somites, where do the intervertebral discs form in the developing vertebral column?
What specific type of cartilage forms the vertebral bodies during development?
What specific type of cartilage forms the vertebral bodies during development?
In relation to the somites, where do vertebral bodies form?
In relation to the somites, where do vertebral bodies form?
According to Von Baer's laws of embryology, which structure appears first: the notochord or the vertebral column?
According to Von Baer's laws of embryology, which structure appears first: the notochord or the vertebral column?
What is the primary function of the notochord in juvenile chordates?
What is the primary function of the notochord in juvenile chordates?
What is the origin of the intervertebral muscles, in relation to the somites?
What is the origin of the intervertebral muscles, in relation to the somites?
Name two key features that distinguish vertebrates from other chordates.
Name two key features that distinguish vertebrates from other chordates.
At what level of the vertebral column does the mixed spinal nerve exit?
At what level of the vertebral column does the mixed spinal nerve exit?
What is the notochordal remnant that is found within the developing intervertebral disc?
What is the notochordal remnant that is found within the developing intervertebral disc?
Besides the presence of a notochord, what are three other characteristics shared by all chordates?
Besides the presence of a notochord, what are three other characteristics shared by all chordates?
Describe the movement provided by segmented muscles acting on a notochord.
Describe the movement provided by segmented muscles acting on a notochord.
What is the fibrous circle that develops around the notochordal remnant?
What is the fibrous circle that develops around the notochordal remnant?
What happens to the notochord and tail when a juvenile chordate transitions to an adult form that is fixed to a substrate?
What happens to the notochord and tail when a juvenile chordate transitions to an adult form that is fixed to a substrate?
What condition can result from the failure of one of the paired cartilage centers to develop, causing vertebral asymmetry?
What condition can result from the failure of one of the paired cartilage centers to develop, causing vertebral asymmetry?
What are the three stages of morphological formation and growth during vertebral development?
What are the three stages of morphological formation and growth during vertebral development?
In the ossification stage, which primary ossification center is unpaired?
In the ossification stage, which primary ossification center is unpaired?
How does the presence of a notochord contribute to the development of the vertebral column?
How does the presence of a notochord contribute to the development of the vertebral column?
What is the primary function of Hox genes during embryonic development, as described in the context?
What is the primary function of Hox genes during embryonic development, as described in the context?
In the embryonic rodent study, what skeletal changes resulted from the loss of the Hox10 gene?
In the embryonic rodent study, what skeletal changes resulted from the loss of the Hox10 gene?
What are the two primary ossification centers in the vertebral column at birth?
What are the two primary ossification centers in the vertebral column at birth?
Besides the centrum and the neural arch, list three secondary ossification centers that appear at puberty in the vertebral column.
Besides the centrum and the neural arch, list three secondary ossification centers that appear at puberty in the vertebral column.
What is the structure called once the ring epiphysis closes in adulthood, and when does this typically occur?
What is the structure called once the ring epiphysis closes in adulthood, and when does this typically occur?
During vertebral development, what structure allows for the expansion of the spinal cord and further growth of the vertebral column?
During vertebral development, what structure allows for the expansion of the spinal cord and further growth of the vertebral column?
What is the primary ossification stage and why is it the longest developmental stage in vertebral development?
What is the primary ossification stage and why is it the longest developmental stage in vertebral development?
What are the three primary ossification centers during vertebral development, and which one is unpaired?
What are the three primary ossification centers during vertebral development, and which one is unpaired?
Describe the role of the notochord in the development of block vertebra.
Describe the role of the notochord in the development of block vertebra.
Explain the relationship between notochordal cells and the formation of a butterfly vertebra.
Explain the relationship between notochordal cells and the formation of a butterfly vertebra.
What vertebral element forms the central portion of the vertebral bodies, and does it complete the whole body?
What vertebral element forms the central portion of the vertebral bodies, and does it complete the whole body?
Besides forming ribs in the thorax, what other structures or features can the costal elements contribute to in other regions of the vertebra?
Besides forming ribs in the thorax, what other structures or features can the costal elements contribute to in other regions of the vertebra?
Identify the two types of cartilage that are present during the osseous stage of development?
Identify the two types of cartilage that are present during the osseous stage of development?
In the embryonic rodent study, what specific vertebral element was affected by the loss of the Hox10 gene causing 'thoracic-isation' of lumbar vertebrae?
In the embryonic rodent study, what specific vertebral element was affected by the loss of the Hox10 gene causing 'thoracic-isation' of lumbar vertebrae?
Which of these vertebral elements contributes to the formation of both the vertebral body and the transverse processes?
Which of these vertebral elements contributes to the formation of both the vertebral body and the transverse processes?
During which stage of vertebral development do sclerotome cells migrate to form the vertebral body and the neural arch?
During which stage of vertebral development do sclerotome cells migrate to form the vertebral body and the neural arch?
Which of the following is NOT a primary ossification center that appears during vertebral column development at birth?
Which of the following is NOT a primary ossification center that appears during vertebral column development at birth?
How does the notochord contribute to the development of block vertebrae?
How does the notochord contribute to the development of block vertebrae?
What is the defining characteristic of the cartilaginous stage of vertebral development?
What is the defining characteristic of the cartilaginous stage of vertebral development?
Which of the following is NOT a feature that contributes to the formation of the vertebral body?
Which of the following is NOT a feature that contributes to the formation of the vertebral body?
What happens to the notochord during the transition from a juvenile chordate to an adult form that is fixed to a substrate?
What happens to the notochord during the transition from a juvenile chordate to an adult form that is fixed to a substrate?
What is the consequence of having too few notochordal cells during vertebral development?
What is the consequence of having too few notochordal cells during vertebral development?
What role do costal centers play in vertebral development?
What role do costal centers play in vertebral development?
What condition is characterized by the excess presence of notochordal cells?
What condition is characterized by the excess presence of notochordal cells?
During which phase does the failure of segmentation manifest morphologically?
During which phase does the failure of segmentation manifest morphologically?
How does excess nucleus pulposus in the intervertebral disc affect vertebral development?
How does excess nucleus pulposus in the intervertebral disc affect vertebral development?
What structural change occurs when there are too many notochordal cells?
What structural change occurs when there are too many notochordal cells?
What is the primary effect of block vertebra on mobility?
What is the primary effect of block vertebra on mobility?
In which vertebral condition will there be a lack of proper segmentation during development?
In which vertebral condition will there be a lack of proper segmentation during development?
Which of the following factors is related to insufficient notochordal cells?
Which of the following factors is related to insufficient notochordal cells?
What does the ossification process involve in terms of vertebral elements?
What does the ossification process involve in terms of vertebral elements?
During embryonic development, what is a possible outcome of failure of proper notochord cell function?
During embryonic development, what is a possible outcome of failure of proper notochord cell function?
What is the primary reason why the primary ossification stage is the longest in vertebral development?
What is the primary reason why the primary ossification stage is the longest in vertebral development?
What occurs when L5 and S1 vertebrae undergo improper development?
What occurs when L5 and S1 vertebrae undergo improper development?
Study Notes
Vertebral Column: Development & Congenital Disease
- Goal: Relate stages of vertebral development to developmental errors and clinical manifestations.
- Outcomes:
- Describe notochord development and its role in vertebral development.
- Describe vertebral development from somite origin, segmentation, and morphological stages (mesenchymal, cartilaginous, and osseous).
- Identify congenital malformations, their origins, and relation to vertebral development age.
- Define vertebral elements, their differences in regions, and correlation to Hox gene expression.
- Describe vertebral column growth.
- Outline:
- Rise of vertebrates
- Stages of vertebral development and developmental errors
- Vertebral elements
- Growth of the vertebral column
Chordates & Vertebrates
- Chordates have a notochord, hollow dorsal nerve tube, pharynx, ventral heart, and a tail extending beyond the anus.
- Vertebrates have a vertebral column, paired sense organs, and thyroid/pituitary glands.
- Vertebral column development is dictated by notochord signals.
- Von Baer's Laws of embryology state general features appear first.
- Chordates and vertebrates have a varied evolutionary origin.
Vertebrates: Those Who Refused to Grow Up
- Juvenile chordates have characteristics like a head, spinal cord, and a tail extending beyond the anus.
- Notochord acts as a supportive rod for muscle attachment, enabling alternating side-to-side movement.
- Notochord and tail are lost when the creature settles and matures.
- Neotony is the evolutionary process where juvenile characteristics persist in adulthood.
- Metamorphosis is absent in neotenic species.
- Vertebral development is a 3-step process (mesenchymal, cartilaginous, and osseous).
Mesenchymal Stage (4-6 weeks)
- Somites are paraxial mesoderm.
- Sclerotome cells from somites migrate to different locations: perinotochordal sheath, neural arch, and costal elements.
- Blood vessels form between somites, aiding sclerotome and somitomere nutrition.
- Vertebral segmentation is controlled by gene expression and blood supply.
- Each vertebra is formed from components of two adjacent somites (intersegmental).
- Somite migration patterns define future vertebral structures.
Cartilaginous Stage (6-9 weeks)
- Mesenchyme is replaced by hyaline cartilage.
- Paired primary centers of chondrification develop into the centrum, neural arches, and costal elements.
- Intervertebral discs form along the notochordal region.
- Fibrocartilage forms the annulus fibrosus.
- Notochordal remnants contribute to the nucleus pulposus, forming part of the IVD.
Osseous Stage (8-10 weeks GA – 6-8 years)
- Primary ossification centers (centrum, neural arches, and costal elements) emerge.
- Bone growth occurs, but cartilage growth plates remain until ~6-8 years.
- Neurocentral and interlaminar cartilage is part of the primary ossification, allowing for vertebral growth.
- Costal centers can form ribs, or fuse with the rest of the vertebrae
Problems & Developmental Anomalies
- Block vertebrae: Insufficient notochordal cells can lead to ossification issues and IVD formation failures.
- Butterfly vertebrae: Excessive notochordal cells can delay centrum ossification, causing skeletal abnormalities.
Vertebral Elements
- Centrum: Central part of vertebral bodies, not the whole body.
- Neural arch: Dorsal arch surrounding the spinal cord, with zygapophyseal joints and mammillary processes aiding lateral body support.
- Costal elements: Form ribs in the thoracic region, or different structures in other areas
Growth of the Vertebral Column
- Vertebral bodies continue to grow in the pre-adolescence, puberty, and late adolescent stages. This growth is facilitated by cartilage endplates, continuing even after primary ossification centers are in place.
- Cartilage growth plates separate centers of ossification until ~6-8 years.
- Secondary ossification centers emerge in spinous processes, transverse processes, and ring epiphysis during puberty.
- Epiphyses (growth plates) close in adulthood, but surface remodeling continues, affecting spinal shape, not height. Vertebral growth continues even after puberty, dictated by the ring apophysis.
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