Skeletal System Flashcards
The somite that the skeletal system starts from
Medial Ventral Somite
What is the structure that is on either side of the somite?
Paraxial Mesoderm
What are the two parts that the somites divide into?
Dermamyotome and Sclerotome
What forms from the Dermamyotome?
Dermatome and Myotome nerves
What forms from the Sclerotome?
Skeleton
What is the dividing somite made up of?
Mesenchyme
What develops from Mesenchyme?
Bone and Cartilage
What are the two kinds of bone growth/ossification?
Inter-carilagenous (intermembrounous) and Endochondral
What allows the bones to grow rapidly as the fetus grows?
The Cartilage state of developing bones
What to the vascularization point cells become?
Osteoblasts
What is the function of osteoblasts?
Deposit osteiod tissue that will become ossification centers
What is deposited at the ossification centers?
Bone matirx
What do spicules become?
Lamellae
What to the lamelle develop around and what do they form?
Blood vessels, Develop osteons
What to the spicules grow to become?
Trabecullae
What are the two types of development for the skull?
Neurocranium and splanchnocranuim
What is the Nuerocranium?
The bone that forms from mesenchyme that surrounds the brain
What are the two kinds of neurocranium development?
Neurochondrocranium and neuromembranocranium
Where does the neurochondocranium develop? When does it start ossification?
The base of the neurocranium. Starts at about 8 weks
What develops from the neurochondrocranium at 6 weeks
- two pairs of nasels
- one pair of prechonreals/trabecula
- one pair of orbitals
- one pair of temborals
- one single hypophysial
- one single parachonral
- one pair of otics
- for single occipitals
What is formed from the neuormembranocranium and how is it formed?
the sides and the roof of the neurocranium. formed by intramembranous ossification
What are the subdivisions that are formed from the neuromembranocranium?
- Two Frontals
- Two parietals
- one vomer
- two nasels
- two lacrimals
what are the large fibrous areas of the skull formed from the neuromembranocranium?
Fontanelles or soft spots
The fetal life bones are separated by connective tissue membranes known as what?
Sutures
The largest fontanelle and when it closes
Anterior fonenelle. closes by the end of the second year
Which two fontanelles are closed at about the 2nd or 3rd month after birth?
Posterior and Anterolateral
When does the posteriolateral fonetanelle close?
by the end of the first year after birth
T/F: The fetal skull can undergo changes during the birth process due to the softness of the fontanelles and sutures.
True
Waht are some of the characteristics of the fetal skull
- bones are very thin
- very large in proportion to the body
- hard for baby to hold the head up when first born
What are the three arches of the splanchondrocranium?
Visceral, Pharyngeal, and Bracheal arches
How many arches have and how many do we start with?
have 5, start with 6
What forms from the 1st arch?
Palate and Maxilla, Meckl’s cartilage, Incus and Malleus
Forms from the 2nd arch?
States, Cranial 1/2 of the hyoid bone, lesser horn
forms from the 3rd arch?
caudal 1/2 of the hyoid bone, greater horn
forms from the 4th and 6th arches?
cartilage of the layranx
What structure is eventually replaced by the vertebral column?
Notocord
What does the vertebral column form from?
somite mesenchyme scerotome
When does chondrification begin to appear?
in the 7th week of development
What does intersegmental development give the vertebra?
muscle attachment and nerve emergence
When do the vertebral arches unite to form the spinous process?
3rd month AFTER BIRTH
When does ossification of the vertebra begin?
9 weeks of development
all ossification centers are present int eh fetus at the 5th month except…
Sacral and coccyx region
How many ossification centers does each vertebra have and where are they in development?
- One in the centrum (body) and one at each half of the vertebral arch
How many ossification centers are in the pubescent vertebra?
- one at tip of spinous process, one at the tip of each transverse process, and two of the rim of the epiphysical center
what does the sternum develop from?
Mesenchymal sternal bands (bars)
When does the upper and lower limbs first appear as buds?
upper-4th week
lower-5th week
Which way dose the upper limb rotate to allow the elbow to face posterior?
laterally
Which way does the lower limb rotate to allow the knee to face anterior?
medially
What is the first bone to ossify in the human body?
Clavicle
