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82 Cards in this Set

  • Front
  • Back
Paraxial mesoderm forms a series of tissue blocks on either side of the neural tube. What are these called? x2.
1. Somatomeres in head
2. Somites from occipital region caudally
Lateral plate mesoderm splits into what layers? x2
1. Somatic layers
2. Splanchnic layers
Somites develop into what? x2
1. Sclerotome
2. Dermomyotome
Sclerotome gives rise to what?
Mesenchyme which become fibroblasts, osteoblasts, and chondroblasts.
Dermomyotome develops into what?
Skin and muscles.
Neural crest cells form what?
1. Ganglia
2. Schwann cells
3. Contributes to development of musculoskeletal system.
What cells contributes to the development of musculoskeletal system.
Neural Crest Cells.
The two parts of the skull.
1. Neurocranium - around the brain
2. Viscerocranium - forms face
Membranous bones of the neurocranium are developed from what?
Neural crest cells and paraxial mesoderm.
What are the two parts of the neurocranium?
1. Membranous portion
2. Cartilaginous portion (chondrocranium)
Describe what the membranous portion of the neurocranium is.
Flat bones of cranial vault
Condrocranium (or cartilaginous portion of neurocranium) formed from what?
SEPARATE cartilages derived from neural crest and paraxial mesoderm.
Describe what the cartilaginous portion of the neurocranium forms into.
Forms base of skull
Cartilaginous portion of the neurocranium is also known as what?
Viscerocranium forms what?
Viscerocranium is formed from what embryonic cells? x3
1. Neural Crest
2. Somites/Somitomeres
3. Lateral Plate
Anterior portion of skull is from what?
Neural crest cells
Posterior portion of skull is from what?
Paraxial mesoderm
What is a major target for teratogens?
Neural crest cells
Palpation of what gives info if ossification of skull is normal or whether intercranial pressure is normal.
Anterior Fontanelle during first few years.
What is a fontanelle?
Wide areas where more than two bones meet.
Where can you find the most prominent fontanelle?
Anterior fontanelle
What are sutures?
Where two bones meet narrow seems of connective tissue
How is the base of the skull formed?
When cartilages fuse and ossify.
The viscerocranium is formed mainly from what two things?
1st and 2nd pharyngeal arches.
Which pharyngeal arch and process is associated with the dorsal portion?
1st arch and maxillary process
Which pharyngeal arch and process is associated with the ventral portion?
1st arch and mandibular process
The first pharyngeal arch give rise to what in the dorsal portion? x3
1. Maxilla
2. Zygoma
3. Temporal
The second pharyngeal arch (with contributions from 2st arch) give rise to what?
1. Incus
2. Malleus
3. Stapes
The first pharyngeal arch contains what.......which will give rise to what in the ventral portion?

MECKEL's cartilage

around with


which gives rise to

Why is the face small compared to the neurocranium?
Due to absence of sinus, teeth, and small bones.
Define cranioschisis.
Cranial vault fails to form


there are small defects in the skull
1. Cranioschisis

2. Anencephaly

3. Vault fails to form and brain tissue exposed to amniotic fluid.
What type of condition is this?

What is this condition?

How did this happen?

Meningocele or Meningoencephalocele

Small defects through which meninges or meninges with brain herniate.
What type of condition is this?

What is this condition?

How did this happen?
Define craniosynostosis.
Caused by premature closure of one or more sutures.
What are some examples of craniosynostosis? x3
1. Scaphocephaly
2. Acrocephaly
3. Plagiocephaly


Premature closure of saggital sutures.


Premature closure of coronal sutures.
1. Craniosynostosis

2. Plagiocephaly

3. Premature closure of coronal and lamboid suture on one side.
Achondroplasia affects primarily what part of body?
Long bone.
At end of 4th week, limb buds consist of what? from where? covered by what?
1. Core of Mesenchyme
2. From somatic layer of lateral plate mesoderm
3. Cuboidal ectoderm
In limb buds at the 5th week, ectoderm at distal end forms what?
Apical ectoderm ridge.
Describe the development of cartilage and muscle in limbs.
Development in a proximal to distal direction.
Upper limb rotates how?
Laterally 90 degrees
With upper limb rotation, describe the position of the extensor muscles and thumb.
Lateral & Posterior surface


Thumb lateral
Describe lower limb rotation.
Medial rotation of 90 degrees.
With lower limb rotation, describe the position of the extensors and big toe.
Anterior surface


Big toe medial
What is a joint interzone?
Where joints formed where cartilage development inhibited.
How are joint cavities created?
Cell death.
How does joint capsules form?
Surrounding tissue of joint cavity forms it.
Describe finger and toes formation.
Cell death separates the apical ectodermal ridges into five parts.
Embryo called a fetus when?
At beginning of 9th week.
How many epiphyseal plates in long bones? small bones (e.g. - phalanges)? or irregular bones (e.g. - vertebrate)?
1. At each end
2. Only at one end of extremity
3. One or more primary centers & several secondary centers.
Define amelia.
Complete absence of one or more limbs.
Define Meromelia
Partial absence of limb
Phocomelia defined.
Hands and feet attached to trunk by irregular bones.
Micromelia defined.
All segments of limbs present but abnormally short.
Ectrodactyly defined
Absence of digit
Syndactyly defined
Fusion of digits or toes.
Describe lobster claw formation.
Abnormal cleft in 2nd and 4th MCP

Absent 3rd MCP & phalanges

Thumb & index fused

4th and 5th digit fused
Describe clubfoot.
Sole of foot turned inward.

Foot adducted.

Plantar flexed.
Clubfoot occurs primarily in which gender?
Amniotic bands may cause what in limb defects?
Ring constriction & amputation of limbs or digits
Congenital hip dislocations occur primarily in which gender.
Describe the formation of the vertebrae.
Sclerotomes surround the notocord and spinal cord.

Caudal half of a sclerotome binds to the subjacent cephalic half of another sclerotome.

This forms precartilaginous vertebral body.
Describe the role of myotomes in vertebral formation.
Myotomes bridge the intervertebral discs, allowing the spine to have movement ability.
Describe Klippel-Feil anomaly.
Pts have fewer Cervical vertebrae. Other vertebrae are fused or abnormal in shape.

Usually associated with other abnormalities.
Describe spina bifida.
Cleft vertebra usually in bony arch
Describe scoliosis
Lateral curving of spine

Resulting from two successive vertebrae fusing asymmetrically

or half a vertebrae missing.
Describe rib formation
Develop from costal processes of thoracic vertebrae,

from sclerotome portion of paraxial mesoderm
Describe sternum formation
Develops from somatic mesoderm in ventral body wall as two sternal bands which fuse.
What is unique about clavicle formation.
Only postcranial bone that develops in mesenchyme instead of cartilage.
Skeletal muscle develop from what embryonic cells?
Paraxial mesoderm (somites & somatomere)
Myotomes form what two muscle forming regions?
Epimere and Hypomere
Describe epimere innervation.
Innervated by dorsal primary rami.
Describe hypomere innervation
Innvervated by ventral primary rami.
What is the association with nerves and muscle segments?
Nerves will remain with original muscle segment throughout its migration
Skeletal myoblast precursor cells fuse forming what?
Long multinucleated fibers.
Describe Prune-belly syndrome.
Absence of abdominal musculature, usually associated with malformation of bladder.
Cardiac muscles develop from what embryonic tissue?
Splanchnic mesoderm surrounding endothelial heart tube.
Cardiac myoblasts adhere to one another and develop into what?
Intercalated discs.

Some cells form Purkinje fibers.
Common partial or complete absence of muscles occur in what muscles? x3
1. Pectoralis major
2. Palmaris longus
3. Abdominal (prune-belly)