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Gastrulation is
Process forming three germ layers ectoderm, mesoderm and endoderm
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Gastrulation has what three main steps
- (1) formation of the primitive streak on the surface of the epiblast
- (2) formation of the three germ layers
- (3) formation of the notochord
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Formation of the germ layers begins by
Epiblast cells migrate to the primitive streak, detach from the epiblast and slip under . 
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Notochord cells are considered to be what germ layer
Mesoderm
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The inward movement of the epiblast is called invagination and is regulated by
FGF (fibroblast growth factor)
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What eventually becomes the umbilical cord and then bladder
Allantois
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Formation of the Notochord (mesoderm)
Epiblasts move cranially towards the prechordal plate in the primitive pit. These cells form the notochord under the epiblast (3rd Week)
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Neurulation
- A cavity is formed on the surface of the ectoderm eventually becoming completely consumed
- Remnants of ectoderm left behind become neural creat cells
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BMP-4 has what effect on development
Causes ectoderm to form epidermis and mesoderm to form the lateral plate and intermediate mesoderm
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What inactivates BMP-4
Secretion of Noggin, Chordin
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Neural inducers (Noggin) cause what to develop
Forebrain and midbrain development
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High levels, and Low levels of BMP cause what to form
- High levels induce Epidermis formation
- Low levels induce Neural crest formation
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Inhibition of BMP causes
Neural plate induction (eventual neural tube)
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Closure of the cranial neuropore occurs at day
25-26, whereas closure of the caudal neuropore occurs at day 27-28
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Neurulation is completed when
The neuropores close
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Lens placode invaginates during 5th week to form
The lens of the eyes
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Otic vesicles will develop into structures for
Hearing and equilibrium
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What arises from the ectoderm
- 1) Central nervous system
- 2) Peripheral nervous system
- 3) Sensory epithelium of ear, eye and nose
- 4) Epidermis of the skin including hair, nails and mammary glands
- 5) The anterior portion of the Pituitary gland
- 6) Enamal of teeth
- 7) Derivatives of Neural crest cells
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Mesodermal Germ Layer by the 17th day, close at the midline forming
- a) Paraxial mesoderm
- b) Lateral plate mesoderm
- c) Intermediate mesoderm
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By 8th week,the intraembryonic cavity will give rise to the
Peritoneal, pleural and pericardial cavities.
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Thr lateral plate seperates into what layers
- Parietal (somatic) forms lateral and ventral body walls
- Visceral (splanchnic) forms wall of gut
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The myotome (paraxial mesoderm) of the somite will differentiate
Into muscles of the body
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The Sclerotome of the somite (paraxial mesoderm) will differentiate into
Vertebrae, skull, and ribs.
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The outer layer of somatic cells (paraxial mesoderm) will form the dermatome which will differentiate into
The dermis of the skin
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Intermediate mesoderm will form
Kidneys and gonads
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The Mesoderm forms
- 1) C.T., cartilage and bones (except in the head and neck region)
- 2) Striated, smooth and cardiac muscles
- 3) Blood and lymph vessels, blood cells, and heart
- 4) Kidneys
- 5) Gonads and ducts
- 6) Cortex of adrenal gland
- 7) Spleen
- 8) Serous membranes lining the body cavities
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The Endoderm forms
- 1) Epithelial lining of the gastrointestinal tract
- 2) Epithelial lining of the respiratory tract
- 3) Parenchyma of the tonsils, thyroid and parathyroid glands, thymus, liver and pancreas
- 4) Epithelial lining of the urinary bladder and most of the urethra
- 5) Epithelial lining of the tympanic cavity and auditory tube
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During the formation of the notocord, mesoderm is everywhere but
The Oropharyngeal (mouth) and cloacal (anus) membranes
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Which grows first, the head or the tail
Head (cephalocaudally)
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The buccopharyngeal membrane is where what forms
The mouth
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The Gi tract is derived from what layer
Endoderm
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The Central nervous system begins to develop when, and appears as what structure
It appears at the 3rd week as the neural plate
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During what weeks is the embryo most seceptible to malformation
Weeks 3-8
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A functional disturbance like mental retardation is most likely to occur during what time of development
At the 8th week on to birth
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The heart fuses from one tube and starts beating when
Day 21-22
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What is the growth factor triggering the growth of blood vessels and other vascular epithelium
veg-1 (Thats why you eat your veggies!)
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What is angiogenesis
New vessels arising from existing vessels
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What is vasculogenesis
Vessels arising from blood islands
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What forms the oral cavity
Stomodeum
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Each myotome and dermatome retains its
Innervation from its segment of origination no matter where they migrate
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Somites can be used by doctors to determine
How far along the embryo has developed (time wise)
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Sacrococcygeal teratoma is
(Tumor in the sacro coccygeal area) a tumor that arises from remnants of the primitive streak which normally degenerates and disappears
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Sirenomelia
- Loss of mesoderm in the lumbar sacral region due to the malformaion of the lower limbs
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When does the notochord begin to appear
3rd week
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By the end of the third week the neural folds begin to raise and join where
5th Somite
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Neural Tube defect of failure to close in cranial region
Anencephaly
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Gastroschisis
- Newborn infant with undeveloped anterior abdominal wall
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The CNS is derived soley of what cells
Neural Tube
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The PNS is derived of soley what cells
Nueral crest cells
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The cloacal membrane (ectoderm and endoderm) ruptures on week, forming
7 to form an opening of the anus.
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The oropharygeal membrane (composed of ectoderm and endoderm) ruptures in what week to form what
Week 4 to form an opening of the foregut that communicates with the amniotic fluid.
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Microglia is made from
Monocytes in the bone marrow
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Neuroblasts and glialblasts
- Pre neurons
- Pre glial cells
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Schwann cells are dervived from
Neural Crest cells
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The mantle forms what in the spinal cord
Dorsal sensory horn
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Alar plate is in the pre spinal cord where
Dorsal end
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The basal plate in the prespinal cord is located
Ventrally
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SHH is released from what, to induce what
Notochord to induce the ventral side formation
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Nerve fibers from the CNS don't become myelinated till when
The first year of postnatal life
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What are the five sections of the neural tube from top to bottom
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
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What does the telencephalon end up as
Cerebral hemispheres
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What does the Diencephalon end up as
Thalamus, Optic cup, Pituitary gland, Hypothalamus, pineal gland
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What does the mesencephalon end up forming
The aquaduct of the brain
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What does the metencephalon end up forming
Pons and Cerebellum
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What does the Myelencephalon end up forming
The medulla
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What is unique about the Pyramid of medulla
This is where the crossing over of the nerves from one hemisphere to the other takes place
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The colliculus is derived from
Alar plate
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The hippocampus controls what functions
Smell and long term memory
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The superior colliculus receives info from
The eyes
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The inferior colliculus receives info from
The ears
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The pineal gland is derived from
Diencephalon
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Rathke's pouch, what comes from
Pituitary gland
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Pharyngeal hypophusis is when
A small portion of Ranthke's pouch perists in the roof of the pharyx
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Foramen of monro is
A channel that connects the third ventricle with the lateral ventricles
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The olfactory bulbs are dervived from
Telencephalon
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The sympathetic nervous system originates from
Neural crest
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What cavity fills the telencephalon and the Diencephalon
Forebrain
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The mesencephalon has what cavity in it
Midbrain
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What cavity fills the Metencephalon and the Myelencephalon spaces
Hindbrain
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Where is regeneration of the nerves possible and where is it not
It happens in the PNS not in the CNS
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What are the three stages of regeneration
Chromatolysis, Anterograde, Regeneration
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What happens in Chromatolyisis
The amount of Nissl bodies is decreased
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What is the importance of schwann cells in regeneration
They recruit macrophages to clear the way for a new axon to be made, and create a canal for budding axons to travel
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