Embryonic and Fetal Period (Exam 1) Flashcards
When is the embryonic period
weeks 3-8
How is the age of the embryo expressed in the beginning of the embryonic period
number of somites presented
How is the size of embryo measured
crown rump length
How is crown rump length measured
vertex of the skull to the caudal tip of the trunk
During what period will organogenesis occur
embryonic
What are the derivatives of the trilaminar embryo
ectoderm
mesoderm
endoderm
What will the ectoderm go on to form
outside stuff and nerves
What will the mesoderm form
bones, urinary, genitals, CT
What will the endoderm go on to form
GI and organs
What germ cell layer is epithelium derived from
All 3 layers
What part of the epithelium is formed from the mesoderm
vascular endothelium
What part of the epithelium is formed by the endoderm
epithelium of structures from yolk sac
What part of the epithelium is formed by the ectoderm
epidermis and ependyma
How are epithelial tumors derived from mesoderm named
Benign: angiomas
Malignant: sarcomas
How are epithelial tumors derived from endoderm named
Benign: papilloma/adenoma
Malignant: carcinomas
How are epithelial tumors derived from ectoderm named
Benign: papilloma/adenomas
Malignant: carcinomas
What layers are connective tissue derived from
mesoderm for torso and limbs
neuroectoderm for head
How are connective tissue tumors named:
Benign: lipoma, fibroma, chondroma, osteoma
Malignant: sarcomas
What layer is muscle derived from
mesoderm
How are muscle tumors named
Benign: myoma
Malignant: myosarcoma
What layer is nerve derived from
neuroectoderm
What germ layers are teratomas derived from
all three layers
ectoderm
endoderm
mesoderm
What is neurulation
formation of the neural tube from the neural plate
What forms the neural plate
ectoderm thickens
When does the neural plate begins to fold
day 20
When does the neural folds make first contact in the cranial end
Day 22
Fusion of the neural plate occurs in what direction
caudal and cranial directions
When does the cranial neuropore close
Day 24-25
When does the caudal neuropore close
Day 26-27
Fusion of the neural folds results in formation of what
the neural tube
What is a neuropore
temporary embryonic openings between neural canal and amniotic cavity
What layer is the neural tube derived from
ectoderm
What is secondary neurulation
invagination of surface ectoderm that forms the sacral and coccygeal spinal cord
What is formation of the sacral and coccygeal spinal cord associated with
tethered cord syndrome
What are neural crest cells
cells that migrate away from the ectoderm after neurulation, dissociate and migrate to the respective locations
What are the neural crest derivatives
parasympathetic ganglia sensory ganglia autonomic and dorsal root ganglia CT around eye optic nerves muscles of the pupil and ciliary body mesenchyme of the head pia and arachnoid mater of the occipital region structures in the pharyngeal arches dermis, smooth muscle and fat of the face odontoblasts Schwann cells chromatin cells of the adrenal medulla neurosecretory cells of the heart and lungs
What will surface ectoderm give rise to
epidermis, hair, nails cutaneous and mammary glands anterior pituitary gland enamel of teeth internal ear lens of eye ectodermal placodes
List the layers of intraembryonic mesoderm formed on either side of the notochord
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
What is derived from the paraxial mesoderm
form the axial skeleton, the vast majority of skeletal muscle, and associated CT and dermis
What is derived from the intermediate mesoderm
the GU and genital system
What will the lateral plate mesoderm form
splits into two layers
What layer of mesoderm will form somites
paraxial mesoderm
How does the paraxial mesoderm form somites
forms somitomeres in a segmental fashion that will develop further into somites
When is the 1st somite formed
day 20
How many somites does embryo have in total
42-44
What occurs to the somites though
disappear at caudal end leaving 37 pairs
What do the first 7 somitomeres form
NOT somites. Rather structures in head and neck
What will the first 4 somites give rise to
development of occipital part of skull, the bones that form the nose, orbit and musculature of the tongue
Where do somites 5-12 form
in the cervical region
Where and what do somites 12-24 form
in the thoracic region to form thoracic vertebrae and musculature and bone of thoracic wall and abdominal wall
also forms structures of the upper limb
What do lumbar somites form
abdominal dermis, muscles, vertebrae, and structures of lower limb
What will somites differentiate into after the 4th week
dermatomyotomes and
sclerotomes
What are dermatomyotomes
splits into dermatome and myotome
What is a dermatome
skin supplied by single spinal nerve
What is a myotome
muscle supplied by a single spinal nerve
What is sclerotome
area of bone or fascia supplied by a single nerve root
Where is vasculature derived from
mesoderm
What are the two stem cells of the mesoderm
hemangioblasts
hemopoietic stem cells
What do hemangioblasts do
give rise to blood vessels
What do hemopoietic stem cells do
give rise to blood cell precursors
What are capillary hemangiomas
collections of blood vessels typically associated with the face
How common are capillary hemangiomas
10% of all pregnancies
What layer of the embryo contributes to the yolk sac
endoderm
What are the membranes that bind the primitive gut tubes at the ends
cloacal membrane
buccopharyngeal
How is the cloaca formed
lateral folding of embryo incorporates allantois leading to cloaca formation
What is the vitelline duct
tube that provides nutrients to the midgut from the yolk sac during gestation
What type of folding leads to formation of primitive gut tube
longitudinal
What parts of the primitive gut tubes are formed from longitudinal folding
foregut, midgut, and hindgut all lined by endoderm
What are the derivatives of endoderm apart from epithelial lining of the GI tract and allantois
eptithelium of respiratory tract, bladder, urethra, tympanic cavity, and auditory tube
parenchyma of the thyroid, parathyroid, liver, and pancreas
stroma (supportive CT) of the tonsils and thymus
When is the fetal period
weeks 9-38 (or birth)
What are characteristics of the fetal period
external form of developing human, presence of major organ systems
rapid growth and further development of organ systems
fetus becomes viable during this period
What are the methods of determining fetal age
expected date of confinement (EDC)
gestational age
last normal menstrual period
actual date of fertilization
What is the expected date of confinement
uses measures of CRL measurements and femur length to determine age
What is gestational age
age from the last mensturation (NOT conception)
What is LNMP age
measure gestation takes approximately 40 weeks
What is actual date of fertilization
with this measure gestation takes 38 weeks
What are the main highlights of the 1st trimester
all major systems developed
What are the main highlights of the 2nd trimester
external anatomy, many birth defects can be detected
What are the main highlights of the 3rd trimester
fetus becomes viable
Highlights of weeks 9-12
liver is major site of erythropoeisis
external genitals can be distinguished
What are the highlights of weeks 13-16
sites of ossification evident
eye movements
eyes facing forward
What are the highlights of weeks 17-20
primary oocytes formed
testes start descending
What are the highlights of weeks 21-25
Surfactant begins to be secreted
prevents alveoli in lungs from collapsing by relieving surface tension
What are the highlights of weeks 26-29
Lungs can now breath
CNS can control breathing and temp
Spleen is still making blood cells, formation starts shifting to bone marrow
When will formation of blood cells shift to bone marrow
After delivery
What are the highlights of 30-34
pupillary light reflex, fat still accumulating
What are the highlights of weeks 35-38
finishing period
final prep of tissues
important to transition to the outside world
During the first 12 weeks what is major site of blood cell production
yolk sac
What is the major organ of hemopoeisis
liver
WHen does the spleen start making blood cells
week 12
When does bone start making blood cells
by week 30
What are possible reasons to perform amniocentesis
if mother has past downs child mother is of advanced age parents carry chromosomal abnormalities parents are x-linked carriers history of neural tube defects parents have inborn errors of metabolisms
What layers are transversed in amniocentesis
Body wall
Faschia
Chorion: (syncytiotrophoblast, cytotrophoblast, mesoderm), amniotic sac
What is the presence of high levels of alpha-fetoprotein indicative of
body wall or neural tube defects
What is the presence of low levels of Alpha fetoprotein in maternal serum indicative of
depressed in the maternal serum in Down syndrome and Trisomy 18
What is spina bifida
neural tube defect marked by congenital cleft of the spinal column
What does spina bifida show usually
protrusion of the meninges and sometimes the spinal cord
also note the tuft of hair on the back
What region do the neural tube folds first make contact
area of the four occipital somites and first cervical somite
What is secondary neurulation
invagination of surface ectoderm that forms the sacral and coccygeal spinal cord
When is secondary neurulation completed
by day 42
Somites give rise to most of what
axial skeleton
voluntary muscles of the neck, body wall and limbs, and to part of the dermis of the neck and trunk
The first 4 somites contribute to what
development of occipital part of the skull, the bones that form the nose, orbit, and musculature of the tongue
What is vasculogenesis
formation of new blood vessels
What is angiogenesis
sprouting from existing vessels
