Embryology Flashcards
The bilaminar embryonic disc is converted into the trilaminar embryo during week _
The bilaminar embryonic disc is converted into the trilaminar embryo during week 3
What are the three layers of the trilaminar embryo?
- Ectoderm
- Mesoderm
- Endoderm
The central nervous system and the sensory organs are derived from _
The central nervous system and the sensory organs are derived from ectoderm
The epidermis of the skin and its appendages (nails, sweat glands, mammary glands, tooth enamel) is derived from _
The epidermis of the skin and its appendages (nails, sweat glands, mammary glands, tooth enamel) is derived from ectoderm
Neural crest cells are derived from _
Neural crest cells are derived from ectoderm
The neural crest cells give rise to _
The neural crest cells give rise to PNS, melanocytes, endocrine tissues, connective tissues in head and heart
Mesoderm gives rise to mainly _ and _
Mesoderm gives rise to mainly muscle and connective tissues (including blood)
* Therefore most organs come from mesoderm
_ layer derives the epithelial linings of respiratory, gastrointestinal, and urinary tracts
Endoderm layer derives the epithelial linings of respiratory, gastrointestinal, and urinary tracts
The epithelial portions of many glands and organs gets derived from _
The epithelial portions of many glands and organs gets derived from endoderm
Most of the body organs are formed from _ layer
Most of the body organs are formed from mesoderm
Gastrulation begins with the formation of the _ in the epiblast which eventually becomes the caudal end of embryo
Gastrulation begins with the formation of the primitive streak in the epiblast which eventually becomes the caudal end of embryo
The primitive streak of the epiblast eventually becomes the (caudal/cranial) end
The primitive streak of the epiblast eventually becomes the caudal end
The primitive node is at the (caudal/cranial) end of the embryo
The primitive node is at the cranial end of the embryo
The axial mesoderm –> _ + _
The axial mesoderm –> prechordal plate (forebrain) + notochord
Paraxial mesoderm will give rise to tissue blocks termined _ which give rise to dermis layer, skeletal muscle, etc
Paraxial mesoderm will give rise to tissue blocks termined somites which give rise to dermis layer, skeletal muscle, etc
* These form the “body wall” (dermis, skeletal muscle, bone, cartilage)
The differentiation of neural tissue from the ectoderm is dependent on induction signal received from the _
The differentiation of neural tissue from the ectoderm is dependent on induction signal received from the notochord
* The notochord induces underlying ectoderm to differentiate into neuroectoderm and form neural plate
The cells immediately adjacent to the notochord become columnar and form a distinctive neural plate which will become the _ and _
The cells immediately adjacent to the notochord become columnar and form a distinctive neural plate which will become the brain and spinal cord
Soon after neural plate formation, the neural folds approach one another in the midline and fuse to form the _
Soon after neural plate formation, the neural folds approach one another in the midline and fuse to form the neural tube
The fusion of the neural tube begins at somite _ in the cervical region and proceeds cranially and caudally
The fusion of the neural tube begins at fifth somite in the cervical region and proceeds cranially and caudally
If failure of the neural tube closure occurs in the cranial region the the defect is called _
If failure of the neural tube closure occurs in the cranial region the the defect is called anencephaly (most of the brain fails to form)
Neural crest cells are formed from _
Neural crest cells are formed from neurulation
* As the neural folds fuse, cells at their lateral borders lose adhesion and dissociate –> neural crest cells
Neural crest cells give rise to _
Neural crest cells give rise to:
* Sensory neurons
* Autonomic neurons (SNS, PNS)
* Neurological cells of PNS
* Melanocytes
* Adrenal medulla cells
* Connective tissues and bone of face/skull
The _ layer of the embryo forms the ventral surface of the embryo and the roof of the yolk sac
The endoderm layer of the embryo forms the ventral surface of the embryo and the roof of the yolk sac
What week does the primitive streak form?
What week does the primitive streak form? week 3
The nucleus pulposus comes from the _ structure
The nucleus pulposus comes from the notochord
The brain and spinal cord are derived from the _
The brain and spinal cord are derived from the neural plate
Organogenesis occurs during _ weeks
Organogenesis occurs during week 3-8 (embryonic period)
* This is when teratogen exposure leads to embryonic malformations
The ectoderm divides into two components the _ and _
The ectoderm divides into two components the surface ectoderm and neuroectoderm
* Ectoderm makes “beauty and brains”
The epidermis is derived from _
The epidermis is derived from surface ectoderm
* Ectoderm makes “beauty and brains”
The CNS and brain is derived from _
The CNS and brain is derived from neuroectoderm
The adenohypophysis is derived from _
The adenohypophysis is derived from surface ectoderm
Neural crest cells are a subset of _
Neural crest cells are a subset of ectoderm
PNS neurons, arachnoid mater, and pia mater are derived from _
PNS neurons, arachnoid mater, and pia mater are derived from neural crest cells (ectoderm)
The bones and connective tissue of the skull is derived from _
The bones and connective tissue of the skull is derived from neural crest cells (ectoderm)
Name the subcategories of mesoderm:
Name the subcategories of mesoderm:
Axial mesoderm
Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm
The notochord is derived from _
The notochord is derived from axial mesoderm
* Notochord –> nucleus pulposus
Vertebrae and ribs are derived from the _
Vertebrae and ribs are derived from the paraxial mesoderm
The lateral plate mesoderm later becomes:
The lateral plate mesoderm later becomes:
* Cardiovascular system
* Microglia
* Stem cells of hematopoietic origin
* Limbs
Neurulation begins during week _ of development
Neurulation begins during week 3 of development
The ectoderm thickens and the neural plate invaginates, forming the neural fold, neural crest, and neural groove; this happens under the influence of the _
The ectoderm thickens and the neural plate invaginates, forming the neural fold, neural crest, and neural groove; this happens under the influence of the notochord
What happens after invagination of the neural plate?
- The neural fold becomes the neural tube
- The neural crest becomes crest cells
These separate from the ectoderm
The neural tube becomes the (CNS/PNS) while the neural crest becomes the (CNS/PNS)
The neural tube becomes the CNS while the neural crest becomes the PNS
The cranial and caudal neuropores close at the end of week _
The cranial and caudal neuropores close at the end of week 4
Dorsal root ganglia and autonomic ganglia are derived from _
Dorsal root ganglia and autonomic ganglia are derived from neural crest cells
Neural tube closure begins in the _
Neural tube closure begins in the midline
* Moves caudally and cranially
Once the neural tube has formed, it induces the surrounding vertebrae to form, from [somite]
Once the neural tube has formed, it induces the surrounding vertebrae to form, from sclerotome
* Neural tube defects can occur if this doesn’t happen normally
The neural tube wall is composed of _ , while the neural tube lumen will become the _
The neural tube wall is composed of neurons, glial cells , while the neural tube lumen will become the ventricles (brain) and central canal (spinal cord)
The neural tube wall forms (3) layers: superficial to deep
- Marginal
- Mantle: aka intermediate
- Ventricular
The marginal layer of the neural tube wall becomes the _
The marginal layer of the neural tube wall becomes the white matter (axon clusters)
The mantle layer of the neural tube wall becomes the _
The mantle layer of the neural tube wall becomes the gray matter (neuronal cell bodies)
The ventricular layer of the neural tube wall becomes the _
The ventricular layer of the neural tube wall becomes the ependyma (lining the ventricles) –> primary source of CSF production
[Layer of neural tube] divides into the alar and basal plates
Intermediate (mantle) layer divides into the alar and basal plates
* Recall this is the gray matter
The alar plate forms at the (dorsal/ventral) side and becomes the _
The alar plate forms at the dorsal side and becomes the dorsal horn
* The dorsal horn has sensory/afferent function
The basal plate forms at the (dorsal/ventral) side and becomes the _
The basal plate forms at the ventral side and becomes the ventral horn
* Ventral horn has motor/efferent function
In the brainstem, the 4th ventricle widens and pushes the (alar/basal) plate laterally and the (alar/basal) plate remains medial
In the brainstem, the 4th ventricle widens and pushes the alar plate laterally and the basal plate remains medial
* Alar –> lateral –> sensory CN nuclei
* Basal –> medial –> motor CN nuclei
The neural tube eventually forms the brain from [3 primary vesicles]
The neural tube eventually forms the brain from 3 primary vesicles:
1. Forebrain (prosencephalon)
2. Midbrain (mesencephalon)
3. Hindbrain (rhombencephalon)
Name the 5 secondary vesicles
- Telencephalon (F)
- Diencephalon (F)
- Mesencephalon (M)
- Metencephalon (H)
- Myelencephalon (H)
Telencephalon becomes the _
Telencephalon becomes the cerebral hemispheres
Diencephalon becomes the _
Diencephalon becomes the thalamus, etc
Mesencephalon becomes the _
Mesencephalon becomes the midbrain
Metencephalon becomes the _
Metencephalon becomes the pons, cerebellum
Myelencephalon becomes the _
Myelencephalon becomes the medulla
Why do many large interior structures grow into a C shape?
As cell number increases, in order to fit into the skull the cerebrum bends and forms into a C shape
* Many internal structures do the same- lateral ventricles, caudate nucleus, corpus callosum
Weeks _ are most vulnerable for neural tube defects or mental retardation
Weeks 3-16 are most vulnerable for neural tube defects or mental retardation
The basic abnormality of NTD is a defect of the overlying _
The basic abnormality of NTD is a defect of the overlying bone
* There may or may not be an abnormality of underlying neural tissue
NTD can be caused by a maternal [deficiency]
NTD can be caused by a maternal folic acid (B9) deficiency
NTD are often detected by [protein abnormality]
NTD are often detected by increased aFP in maternal blood (and amniotic fluid)
* Also picked up via ultrasound
* Increased acetylcholinesterase is confirmatory
A tuft of hair at the lower back is pathognomonic for _
A tuft of hair at the lower back is pathognomonic for spina bifida occulta
_ is a form of spina bifida cystica which often involves no functional impairments
Meningocele is a form of spina bifida cystica which often involves no functional impairments
* Only an outpouching of meninges (no neural tissue)
_ is a form of spina bifida cystica which often involves paralysis below the lesion, bowel/urinary dysfunction, and hydrocephalus
Myelomeningocele is a form of spina bifida cystica which often involves paralysis below the lesion, bowel/urinary dysfunction, and hydrocephalus
* Herniation of the meninges and neural tissue
_ is a form of spina bifida cystica that involves loss of function below the lesion and often develops with anencephaly
Rachischsis is a form of spina bifida cystica that involves loss of function below the lesion and often develops with anencephaly
_ is a cranial nerve tube defect in which the meninges (+/-) brain may herniate
Cranium bifidum is a cranial nerve tube defect in which the meninges (+/-) brain may herniate
Cranium bifidum is a defect of [bone]
Cranium bifidum is a defect of occipital bone
What is the spectrum of severity of cranial NTD?
Cranial meningocele
Meningoencephalocele
Anencephaly
_ can occur if the cranial neuropore does NOT fuse during week 4
Anencephaly can occur if the cranial neuropore does NOT fuse during week 4
* No neural tube forms in the cranial region
* No cerebrum forms, no skull, no skin
* Polyhydramnios (no swallowing center in brain)
_ is associated with midline facial defects that range from hypotelorism to cyclopia
Holoprosencephaly is associated with midline facial defects that range from hypotelorism to cyclopia
Holoprosencephaly is associated with environmental exposure like _ , or genetic mutations like _ , chromosomal abnormalities like _
Holoprosencephaly is associated with environmental exposure like fetal alcohol syndrome , or genetic mutations like homeobox gene , chromosomal abnormalities like trisomy 13
Name 3 common genetic mutations associated with holoprosencephaly
Name 3 common genetic mutations associated with holoprosencephaly
1. Six3 homeobox gene
2. SHH gene
3. ZIC2 gene
_ is a failure of separation of the forebrain into two cerebral hemispheres
Holoprosencephaly is a failure of separation of the forebrain into two cerebral hemispheres
_ is a rare, gene-linked brain malformation characterized by the absence of normal folds in the cerebral cortex
Lissencephaly is a rare, gene-linked brain malformation characterized by the absence of normal folds in the cerebral cortex; associated with microcephaly
* The word means “smooth brain”
Non-communicating hydrocephalus means _
Non-communicating hydrocephalus means obstruction to CSF flow
* The ventricles are not communicating with the subarachnoid space
Communicating hydrocephalus means _
Communicating hydrocephalus means there’s an imbalance between CSF production and reabsorption (without obstruction)
The most common cause of hydrocephalus is _
The most common cause of hydrocephalus is stenosis of the cerebral aqueduct
_ is a type of congenital brain abnormality where the lower part of the brain, the cerebellar tonsils, extends into the upper spinal canal
Chiari type I is a type of congenital brain abnormality where the lower part of the brain, the cerebellar tonsils, extends into the upper spinal canal
In chiari type I, the cerebellar tonsil herniates downward through the _
In chiari type I, the cerebellar tonsil herniates downward through the foramen magnum
(Chiari I/ II) is strongly associated with syringomyelia
Chiari type I is strongly associated with syringomyelia
* Fluid-filled cavity or cyst forms within the spinal cord
Chiari type II involves _
Chiari type II involves herniation of the vermis and downward displacement of the brainstem
* Essentially a more severe form of type I
Chiari type II is almost always associated with _ and accompanied by _
Chiari type II is almost always associated with lumbosacral myelomeningocele and accompanied by hydrocephalus (> 80% of cases)
Vermal agenesis is called _ syndrome
Vermal agenesis is called Dandy walker syndrome
* Also will see dilated fourth ventricle, hydrocephalus
The alar plate is regulated/induced by _
The alar plate is regulated/induced by bone morphogenic protein (BMP)
The basal plate is regulated/induced by _
The basal plate is regulated/induced by sonic hedgehog gene (SHH)
The lateral ventricle is a derivative of [secondary vesicle]
The lateral ventricle is a derivative of telencephalon
The third ventricle is a derivative of [secondary vesicle]
The third ventricle is a derivative of diencephalon
The cerebral aqueduct is a derivative of [secondary vesicle]
The cerebral aqueduct is a derivative of mesencephalon
The upper part of the fourth ventricle is a derivative of [secondary vesicle] while the lower part is from [secondary vesicle]
The upper part of the fourth ventricle is a derivative of metencephalon while the lower part is from myelencephalon
Microglia is derived from [embryonic layer]
Microglia is derived from mesoderm
Spina bifida occulta will have _ aFP levels
Spina bifida occulta will have normal aFP levels
(True/False) Dura is intact in spina bifida occulta
True; dura is intact; there is failure of the caudal neuropore to close but no herniation
Holoprosencephaly: MRI shows monoventricle + fusion of basal ganglia
