Final Exam Flashcards
What is mesenchyme
Meshwork of loosely organized embryonic connective tissue
What is the dividing somite made up of and what does this give rise to
Mesodermal cells
Mesenchyme
What does condensation of mesenchyme give rise to
Formation of bone models
What are the 2 types of bone formation from the sclerotome
Cartilage bones
Membrane bones
Characteristic of cartilage bones
Replace provisional cartilage
Remaining bones of the body
face and cranial roof are membrane bones
Characteristics of membrane bones
Make up the face and cranial roof
Develop from skeletal mesenchyme
Why is the cartilage stage of bone development important
Cartilage bone can grow rapidly to match the growth of the fetus
During the 8th week of development mesenchyme condenses and forms
Chondrification centers
What is the most common type of cartilage that also makes up most of the embryonic skeleton
Hyaline
In intramembranous ossification where osteoid tissue is being deposited will become
Ossification centers
What is the neurochondrocranium
Cartilaginous base of the neurocranium and the skull
What is in the neurochondrocranium at 6 weeks
Two pairs of nasals
One pair of orbitals
One pair of temporals
What is the neuromembranocranium
Forms the sides and the roof of the neurocranium
What “bones” are in the neuromembranocranium
Two parietals
Two frontals
With the development of the neurochondrocranium there are large fibrous areas separating the bones of the skull known as
Fontanells and sutures
What are sutures
Connective tissue membranes separating the bones of the skull during fetal development
What are fontanells
Membrane covering the large fibrous areas at the angle of bones
Which fontanel is the largest and when does it close
Anterior
By the end of the second year
When do the posterior and anterolateral fontanels close
2-3 months
When does the posterolateral fontanel close
End of first year
What does the 1st visceral arch form
Palate and maxilla
Meckels cartilage
Incus and malleus
What does the 2nd visceral arch form
Stapes
Cranial half of the hyoid
Lesser horn
What does the 3rd visceral arch form
Caudal half of the hyoid
Greater horn
What do the 4th and 6th arches form
Cartilages of the larynx
no ossification occurs here
The vertebral column develops from
Somite mesenchyme sclerotome
The vertebral column develops caudal part______ packed area, cranial part_______ packed area
Densely (sclerotome proliferates)
Loosely
Intersegmental development give the vertebrae __________&__________
Muscle attachment
Nerve emergence
When does chondrification begin in the cranial vertebrae
7th week then continues down the lower levels
Describe the centrum of the vertebral development
- cartilaginous vertebrae
- replaces notochord
- chondrification centers
Describe the vertebral arches of the vertebral development
- on each side there is a medial growth around the neural tube
- one chondrification in each arch
When do the vertebral arches unite to form the spinous process
Not until after the 3 month after birth
When does the ossification of the vertebrae begin______, during the 5th month all ossification centers are present except for __________.
9 weeks
Sacral and coccyx regions
How many ossification centers are there in the vertebrae, where are they ?
3
One in the Centrum
One in each half of the vertebral arch
How many ossification Centers are there in the vertebrae at puberty, where are they
5
One at tip of spinous process
One at each tip of transverse process (2)
Two on the rim of the epiphyseal center
Mesenchymeal bands of the sternum are
Sternal bars
Durning the 6th week the sternum ______
Unites with the end of ribs to fuse with each other
Smaller cartilages anterior to the sternal bars fuse with the sternum making the
Manubrium
What bone ossifies before any other bone in the body
Clavicle
What is achondroplasia
Slow growth of cartilage and bone ossification
Characteristics of achondroplasia syndrome Growth Craniofacial Skeletal Muscle Etiology
- small stature
- megolacephaly (large face head)
- lumbar lordosis, short tubular bones, thoracolumbar kyphosis
- mild hypotonia
- autosomal dominant
What is cleidocranial dysostosis
- clavicle agenesis
- skull disorders
- jaw disorders
Spina bifida , occulta is
Limited to the skeletal components
Spina bifida, cystica is
Involvement of the meninges
Spina bifida ( cystica) involving the meninges only is called
Meningocoele
Spina bifida ( cystica) involving the meninges and spinal cord is called
meningomyelocoele
What is congenital scoliosis
- abnormal curvature of the spine
- you can have numerical variations, morphological variations, or both
What is craniostenosis
- premature closures of the sutures of the skull
- brain and eye deformities
What is oxycephaly
All sutures close prematurely ( symmetrical)
What is plagiocephaly
Happens when sutures close asymmetrically
What is scaphocephly
When sagital sutures close prematurely
What is acrocephaly (brachycephaly)
Coronal sutures are involved.
What are cervical ribs and what is the chance of having them
Rib attached to 7th cervical vertebrae
32% 1:500
What is the chance of having lumbar ribs
30%
1:500
What is amelia and what is the etiology
Absence of limbs
Environmental factors
What is phocomelia and what is the etiology
Absence or reduction of the proximal part of the limb
Environmental factors
What is sympodia and what is the etiology
Monopodia
Hypoplasia and fusion of the lower limbs
Spontaneous
What is dichiria and what is the etiology
Duplication of the distal parts of Limbs
Autosomal dominate
What is polydactyly and what is the etiology
Presence of extra digits
Autosomal dominate
What is syndactyly and what is the etiology
Fusion of the digits
Autosomal dominate
What is brachydactyly and what is the etiology
Shortness of digits
Autosomal dominate
What is Hyperphalangism and what is the etiology
Long digits with extra phalanges.
Autosomal dominate
What are the somite derivatives
Dermamyotome -Dermatome Skin -Myotome Muscles Sclerotome -Skeleton
What are Small dorsal division of the skeletal muscles
epimere or epiaxial
What is the large ventral division of the skeletal muscles
hypomere or hypaxial
What do epimers form
Extensor muscles of the vertebral column
Dorsal primary rami *
What do hypomers give rise to
Muscles of the limbs and body wall
Ventral primary rami *
What are 2 examples of muscle changes in directions
Migration of muscle - latissimus dorsi
Fusion of successive myotomes- rectus abdominis
What forms ligaments
Degeneration of myotomes
Ex tensor fascia lata