Back 3/3 Flashcards
Ectoderm gave rise to ….
The central nervous system
The endoderm gave rise to …..
lining of gut, respiratory and urogenital tracks
Mesoderm gave rise to….
muscles, bones, connective tissue and fat
Ectoderm also forms the ____
Epidermis
these tubes come into existence at a time when the embryo is made of three flat sheets of cells - the ____ ______
Trilaminar Embryo
The _____ signals the ectoderm to fold in upon itself to form a _____ _____.
Notochord. Neural groove
When the notochord signals the ectoderm to fold in upon itself to form a neural groove. What is this process called?
Neurulation
Label:
-Notochord
- Intraembryonic coelom
- Neural Groove
- Neural Crest
- Somite
Label:
2-Notochord
3- Intraembryonic coelom
5- Neural Groove
4- Neural Crest
1- Somite
What level does the Blue represent?
Red?
Yellow?
Blue= Ectoderm
Red= mesoderm
Yellow= endoderm
The neural groove folds to become the ____ ______, which will give rise to the entire _____.
Neural Tube, CNS
Name the 3 components of the Central Nervous System.
- Brain
- Brainstem
- Spinal Cord
A second set of ectoderm cells also move into the mesoderm called ___ ____ _____, which migrate throughout the body
Neural crest cells
Mesoderm close to the neural tube forms _____.
Somites
Somites form ______, ______ and ______ of the body wall.
muscles, bones and dermis
Somites develop on either side of the _______ and ______.
Neural Tube and notochord
How many occipital somites are there?
4
Somites have the same number of spinal nerves. Cervical = 8
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccygeal = 2-3
Each somite breaks into 3 functionally different parts. Name them
- Sclerotome
- Myotome
- Dermatome
The sclerotomes gives rise to …..
Vertebrae and axial bone
Identify:
- Sclerotome
- Neural Tube
- Dermatome
- Myotome
2- Sclerotome
1- Neural Tube
3- Dermatome
4- Myotome
Posterior horn develops into _____
Sensory Neurons
Anterior horn develops what kind of neurons.
Motor neurons
The neural crest cells develop into….
Posterior Root Ganglia
Neurons in the spinal cord’s anterior horn send axons to ______
Skeletal muscles
Sensory axons from the posterior root ganglia (neural crest) extend laterally towards _______
dermatomes
Sensory axons from the posterior root ganglia (neural crest) extend medially to reach the …..
posterior horn of spinal cord.
Sensory neurons travel to dermatomes by following ______ that have reached the corresponding _____
motor axons, myotomes
When nerves become compressed, usually ______ precede ______. Why?
Sensory signs precede motor signs.
Because the sensory axons are on the outside of the nerve
Anterior horn axons form from _____
myotome
Posterior root ganglion axons form from …
Dermatome and posterior horn
_______ split in half as fissures (of von Ebner) develop so axons can pass
Sclerotomes
Sclerotome remnants fuse with their neighbors to become ______
Vertebrae
_____ and the ______ will remain at the site of the fissures.
Intervertebral discs and intervertebral foramina
Sclerotome mesenchyme surrounds the _____ & _____, forming a loose model of the vertebrae and ribs
neural tube and notochord
______ form in the sclerotome and start to replace it with cartilage in the 6th week.
Chondrification centers
In the 7th week, _____ begins replacing cartilage
bone
______ form in the vertebral body (centrum), pedicles, and lamina.
Primary ossification centers
Ossification is not complete until after adolescence when _____ in _____ fuse to the rest of the vertebra
secondary centers of ossification, transverse and spinous processes (and annular epiphyses)
______ are the last part of the vertebrae to ossify
Spinous processes
_____ occurs when ossification fails or the spinous process does not form at all.
Spina Bifida
Spina Bifida is due to the presence of what protein in maternal blood?
Alpha-fetoprotein
_______is failure of the neural arch, specifically the spinous process, to ossify. The defect is not large and is sometimes marked by a tuft of dense hair.
Spina bifida occulta
______ occurs when meninges and CSF herniate through the hole left by the failed neural arch
Meningocele
______ is the same as a meningocele with added herniation of the spinal cord and/or roots
Meningomyelocele
_______ is failure of the neural tube to fold properly. Neural arch cannot form.
Rachischisis
Abnormalities in Hox gene expression may cause ______ of the S1 vertebrae or ______ of the L5 vertebrae
lumbarization
sacralization
In adults, the spinal cords ends at what level?
Approximately L1
In embryos, the spinal cord ends at approximately what level?
It doesnt, spinal cord runs the full length of the vertebral canal
At 6 months of gestation, the spinal cords ascends to approximately what level?
approx. S1
A spinal cord of a newborn extends to approx. what level?
Approx. L2-L3
Motor neurons in the _____ of the spinal cord innervate muscles from the ______ as well as other areas of mesoderm
anterior horn, somites (myotome)
The ______ splits to form true back muscles innervated by ______.
myotome, posterior rami
The ______ also forms the muscles of the trunk and limbs, innervated by ________.
myotome, anterior rami
______ travel more or less directly into the muscles and skin that they innervate.
Posterior rami
Anterior rami form complex plexi before reaching their target muscles. Why? What muscles do they become?
Their associated myotomes migrate and pulling the nerves behind.
Muscles of the neck, thorax, abdomen, pelvis, limbs, orbit, and tongue.
What is it called when muscle fail to develop during embryonic formation?
Muscle agenesis
Name the syndrome where the abdominal muscles fail to develop?
Prune Belly Syndrome
What gene is responsible for double muscling?
Myostatin
_____ & ________ regions migrate into the upper limb bud
Myotomes and dermatomes from C4-T2 regions
_____ & ______ migrate into the lower limb bud.
Myotomes and dermatomes from L4-S3
Dorsal/posterior muscle mass lead to _____
Extensors
Ventral/anterior muscle mass lead to _____
Flexors
Where do limb bones come from?
lateral mesoderm
Describe the general trend of overall Morphology of limbs
Flipper-like upper limb bud -> Hand plate forms -> Digital rays appear in hand plate -> Apoptosis in the interdigital areas that carves out the digits -> Upper limbs bend at the elbow, fingers are short and webbed -> Fingers and toes are distinct and separated
Programmed cell death is called ….
Apoptosis
Define syndactyly
The webbing between the fingers does not completely go away
Name the condition where the tail segment may rescind early or fail to form, this may result in fusion of the rear limb buds
Sirenomelia
***
The dorsal muscle masses make extensor muscles in both upper and lower limbs but the extensors of a mature upper limb are on the posterior side while the extensors of the lower limb are on the anterior side. Why?
Due to fetal positioning in the uterus?????
The outgrowth of the limb buds are initiated and maintained by the…
AER, Apical Epidermal Ridge
What signal is produced in the AER?
FGF8- Fibroblast Growth Factor 8
Define Amelia
without a limb
Define meromelia
The partial absence of at least one limb
Define Phocomelia, what was it caused by?
hands and feet are attached the the trunk, thalidomide (anti-nausea drug)
Name the molecular marker signal protein for medio-lateral patterning.
Sonic Hedgehog (Shh)
Define Polydactyly
More than 5 fingers/toes on one extremity
A herniated disc effects the level above/below?
Below
What artery feeds the horns?
Sulcal artery
Lumbar triangle is generally considered weaker or stronger?
Weaker
What artery feeds the spinal cord?
Greater anterior segmental medullary artery
Define ipsalateral
For a Left muscle contraction, rotate and lean left
Define Contralateral
The opposite side of what you are asking, example: Transversospinalis muscle group
