Developmental Anatomy Flashcards
What are 3 important landmarks at 18 days?
- Mesdorm thickens to form paraxial mesoderm
- Coelomic spaces arise
- Notochord induces neural plate development
When does:
- First somite arise
- last somite?
- 20 days
- 30 days
Describe the difference between dermomyotome and sclerotome?
What about their relative location on paraxial mesoderm?
- Dermotome - dermis
- Myotome - muscles
- Sclerotome - skeleton
Sclerotome is deep to myotome, which is deep to dermotome
Name 2 different types of bone formation and how they differ
- Endochondral
- involves cartilagineous precursor to bone
- Mesenchyme -> cartilage -> bone
- Intermembranous
- No cartilage precursor
- Mesenchyme -> bone
How are joints formed?
-
Interzoneal Mesenchyme differentiates based on what type of joint it is forming
- Fibrous
- Synovial
- Cells will undergo apoptosis to form the joint cavity
What are the 5 key points to know in axial skelton formation (think, how do you go from somites to a spinal column)
ABIVM
A better inside voice, man!
- A - annulus fibrosis forms from dense cranial cells
- B - vertebral body forms from lower scelerotome
- IV - notochord forms the nucleus pulposis in IV disc (chordoma if not degenerate)
- M - myotome is at level of IV disc and stretches across 2 adjacent vertebrae
What does the neurocentral joint form?
What are some important landmarks
- Neurocentral joint is a joint between the vertebral body and vertebral arch halves
- On dorsal side, vertebral arch halves are separated by cartilaginous spinous processes (not a joint)
- 5 weeks - mesenchymal vertebrae (centrum, costal processes, and vertebral forament)
- forms a neural arch around developing spinal cord
- 6 weeks - cartilaginous precursor
- 7 weeks - 3 ossification centers = 3 bony parts
- You have “3 bony parts” until birth, which begin to ossify further in early years
What are 3 anomalies of axial skeletal development
- Spina Bifida
- Congenital hemivertebra - can lead to scoliosis
- Accesssory lumbar or cervical ribs - can cause Thoracic Outlet Syndrome
How does the sternum develop?
The 2 sternal bands become sternal plates and fuse cranial to caudal
Anomalies (often associated with mutation of homeobox genes responsible for spatial arrangement of body’s segments)
Name 2 sternal anomalies and their underlying causes
- Associated with mutations in homeobox genes
- Pigeon Chest
- Overgrowth of ribs causes sternum to protrude forward
- Cleft Sternum
- Incomplete fusion of sternal plates in the midline
- Funnel chest - sunken in sternum
- defect of the diaphragm that forms a small central tendon which pulls chest inward
- Ectopia Cardis (worst prognosis)
What type of bone formation is involved in the appendicular skeleton? And what are some important landmarks?
- Endochondral Bone formation
- cartilagenous precursor before bone
- 5 weeks - mesenchymal condensations
- 6 weeks - chondrified
- 8 weeks - ossification begins
What 4 sources do limb tissues come from? And name the important components of each source?
- Lateral Plate Mesoderm
- Skeleton
- Tendons
- Ligaments
- Vasculature
- Somites
- Musculature
- Neural Crest
- Schwann cells
- DRG
- Sensory Axons
- Neural Tube
- Motor Axons
When do the limbs develo? How do the limbs rotate to anatomic position in utero?
- Limb buds appear at 4th - 5th week; upper limb seen first, which give rise to digits around the 6th - 7th week
- Upper limb rotates 90 degrees LATERALLY so that it is in the anatomic position
- Lower limb rotates 90 degrees MEDIALLY to be in anatomic position
What is the difference between epaxial and hypaxial muscle?
- Epaxial division (dpimere) - givs rise to deep back muscles (dorsal rami)
- Hypaxial (hypomere) - gives rise to muscles in limb and body wall ( VENTRAL Rami)
- Striated muscles of the trunk develop from myotomes (in contrast to smooth and cardiac muscle which develops from splanchnic mesoderm
Where does smootha nd cardiac muscle come from?
Splanchnic mesoderm forms smooth and cardiac muscle
What germ layer do muscles develop from?
MESODERM (except those of the optic cup)
Where do mammary glands develop from?
Priomordial mammary glands invades the mesenchyme and forms glandular buds (called the “mammary ridge)
What does the 4th aortic arch turn into?
What pathology can result from improprer obliteration of the 4th arch?
- Left portion = connects aortic sac with descending aorta (ie forms part of arch of aorta)
- Right portion = forms proximal portion of Right Subclavian A.
- You form a DOUBLE aortic arch if caudal portion of 4th aortic arch fails to obliterate
Describe the bovine heart abnormality. Is it pathological?
Bovine heart = Brachiocephalic trunk gives rise to RSCA, Right common carotid AND Left common carotid
This is opposed to the left common carotid branching normally off the aortic arch.
Describe a double aortic arch, and the underlying embryological pathology
Caudal portion of right dorsal aorta never obliterates and the right and left dorsal aorta remain tethered
- Caudal Right dorsal aorta normally involutes to form R. SCA
What causes a right aortic arch formation?
The caudal portion of the left involutes, creating a right sided aortic arch
Describe a retroesophageal RSCA?
- The entire right dorsal aorta involutes and right arch of the aorta is BEHIND the trachea and esophagus
