Embryonic and Fetal Period (Exam 1) Flashcards
1
Q
When is the embryonic period
A
weeks 3-8
2
Q
How is the age of the embryo expressed in the beginning of the embryonic period
A
number of somites presented
3
Q
How is the size of embryo measured
A
crown rump length
4
Q
How is crown rump length measured
A
vertex of the skull to the caudal tip of the trunk
5
Q
During what period will organogenesis occur
A
embryonic
6
Q
What are the derivatives of the trilaminar embryo
A
ectoderm
mesoderm
endoderm
7
Q
What will the ectoderm go on to form
A
outside stuff and nerves
8
Q
What will the mesoderm form
A
bones, urinary, genitals, CT
9
Q
What will the endoderm go on to form
A
GI and organs
10
Q
What germ cell layer is epithelium derived from
A
All 3 layers
11
Q
What part of the epithelium is formed from the mesoderm
A
vascular endothelium
12
Q
What part of the epithelium is formed by the endoderm
A
epithelium of structures from yolk sac
13
Q
What part of the epithelium is formed by the ectoderm
A
epidermis and ependyma
14
Q
How are epithelial tumors derived from mesoderm named
A
Benign: angiomas
Malignant: sarcomas
15
Q
How are epithelial tumors derived from endoderm named
A
Benign: papilloma/adenoma
Malignant: carcinomas
16
Q
How are epithelial tumors derived from ectoderm named
A
Benign: papilloma/adenomas
Malignant: carcinomas
17
Q
What layers are connective tissue derived from
A
mesoderm for torso and limbs
neuroectoderm for head
18
Q
How are connective tissue tumors named:
A
Benign: lipoma, fibroma, chondroma, osteoma
Malignant: sarcomas
19
Q
What layer is muscle derived from
A
mesoderm
20
Q
How are muscle tumors named
A
Benign: myoma
Malignant: myosarcoma
21
Q
What layer is nerve derived from
A
neuroectoderm
22
Q
What germ layers are teratomas derived from
A
all three layers
ectoderm
endoderm
mesoderm
23
Q
What is neurulation
A
formation of the neural tube from the neural plate
24
Q
What forms the neural plate
A
ectoderm thickens
25
When does the neural plate begins to fold
day 20
26
When does the neural folds make first contact in the cranial end
Day 22
27
Fusion of the neural plate occurs in what direction
caudal and cranial directions
28
When does the cranial neuropore close
Day 24-25
29
When does the caudal neuropore close
Day 26-27
30
Fusion of the neural folds results in formation of what
the neural tube
31
What is a neuropore
temporary embryonic openings between neural canal and amniotic cavity
32
What layer is the neural tube derived from
ectoderm
33
What is secondary neurulation
invagination of surface ectoderm that forms the sacral and coccygeal spinal cord
34
What is formation of the sacral and coccygeal spinal cord associated with
tethered cord syndrome
35
What are neural crest cells
cells that migrate away from the ectoderm after neurulation, dissociate and migrate to the respective locations
36
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
```
37
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
```
38
List the layers of intraembryonic mesoderm formed on either side of the notochord
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
39
What is derived from the paraxial mesoderm
form the axial skeleton, the vast majority of skeletal muscle, and associated CT and dermis
40
What is derived from the intermediate mesoderm
the GU and genital system
41
What will the lateral plate mesoderm form
splits into two layers
42
What layer of mesoderm will form somites
paraxial mesoderm
43
How does the paraxial mesoderm form somites
forms somitomeres in a segmental fashion that will develop further into somites
44
When is the 1st somite formed
day 20
45
How many somites does embryo have in total
42-44
46
What occurs to the somites though
disappear at caudal end leaving 37 pairs
47
What do the first 7 somitomeres form
NOT somites. Rather structures in head and neck
48
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
49
Where do somites 5-12 form
in the cervical region
50
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
51
What do lumbar somites form
abdominal dermis, muscles, vertebrae, and structures of lower limb
52
What will somites differentiate into after the 4th week
dermatomyotomes and
| sclerotomes
53
What are dermatomyotomes
splits into dermatome and myotome
54
What is a dermatome
skin supplied by single spinal nerve
55
What is a myotome
muscle supplied by a single spinal nerve
56
What is sclerotome
area of bone or fascia supplied by a single nerve root
57
Where is vasculature derived from
mesoderm
58
What are the two stem cells of the mesoderm
hemangioblasts
| hemopoietic stem cells
59
What do hemangioblasts do
give rise to blood vessels
60
What do hemopoietic stem cells do
give rise to blood cell precursors
61
What are capillary hemangiomas
collections of blood vessels typically associated with the face
62
How common are capillary hemangiomas
10% of all pregnancies
63
What layer of the embryo contributes to the yolk sac
endoderm
64
What are the membranes that bind the primitive gut tubes at the ends
cloacal membrane
| buccopharyngeal
65
How is the cloaca formed
lateral folding of embryo incorporates allantois leading to cloaca formation
66
What is the vitelline duct
tube that provides nutrients to the midgut from the yolk sac during gestation
67
What type of folding leads to formation of primitive gut tube
longitudinal
68
What parts of the primitive gut tubes are formed from longitudinal folding
foregut, midgut, and hindgut all lined by endoderm
69
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
70
When is the fetal period
weeks 9-38 (or birth)
71
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
72
What are the methods of determining fetal age
expected date of confinement (EDC)
gestational age
last normal menstrual period
actual date of fertilization
73
What is the expected date of confinement
uses measures of CRL measurements and femur length to determine age
74
What is gestational age
age from the last mensturation (NOT conception)
75
What is LNMP age
measure gestation takes approximately 40 weeks
76
What is actual date of fertilization
with this measure gestation takes 38 weeks
77
What are the main highlights of the 1st trimester
all major systems developed
78
What are the main highlights of the 2nd trimester
external anatomy, many birth defects can be detected
79
What are the main highlights of the 3rd trimester
fetus becomes viable
80
Highlights of weeks 9-12
liver is major site of erythropoeisis
external genitals can be distinguished
81
What are the highlights of weeks 13-16
sites of ossification evident
eye movements
eyes facing forward
82
What are the highlights of weeks 17-20
primary oocytes formed
| testes start descending
83
What are the highlights of weeks 21-25
Surfactant begins to be secreted
| prevents alveoli in lungs from collapsing by relieving surface tension
84
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
85
When will formation of blood cells shift to bone marrow
After delivery
86
What are the highlights of 30-34
pupillary light reflex, fat still accumulating
87
What are the highlights of weeks 35-38
finishing period
final prep of tissues
important to transition to the outside world
88
During the first 12 weeks what is major site of blood cell production
yolk sac
89
What is the major organ of hemopoeisis
liver
90
WHen does the spleen start making blood cells
week 12
91
When does bone start making blood cells
by week 30
92
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
```
93
What layers are transversed in amniocentesis
Body wall
Faschia
Chorion: (syncytiotrophoblast, cytotrophoblast, mesoderm), amniotic sac
94
What is the presence of high levels of alpha-fetoprotein indicative of
body wall or neural tube defects
95
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
96
What is spina bifida
neural tube defect marked by congenital cleft of the spinal column
97
What does spina bifida show usually
protrusion of the meninges and sometimes the spinal cord
also note the tuft of hair on the back
98
What region do the neural tube folds first make contact
area of the four occipital somites and first cervical somite
99
What is secondary neurulation
invagination of surface ectoderm that forms the sacral and coccygeal spinal cord
100
When is secondary neurulation completed
by day 42
101
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
102
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
103
What is vasculogenesis
formation of new blood vessels
104
What is angiogenesis
sprouting from existing vessels
