Embryology Flashcards
(137 cards)
1
Q
Important genes of embryology
A
- Sonic hedgehog gene
- Wnt-7 gene
- FGF gene
- Homeobox (Hox) gene
2
Q
embryology - Sonic hedgehog gene - location and function
A
Produced at base of limbs in zone of polarizing activity
Involved in patterning along AP axis and CNS delopment
3
Q
Sonic hedgehog gene - mutation –>
A
holoprosencephaly
4
Q
embryology - Wnt-7 gene - location
A
produced at apical ectodermal ridge (thickened ectodermal at distal end each devolving limb)
5
Q
embryology - Wnt-7 gene - function
A
necessary for proper organization along dorsal-ventral axis
6
Q
embryology - FGF gene - location and function
A
Produced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs
7
Q
embryology - Homeobox (Hox) genes - location and function
A
involvd in segmental organisation of embryo in craniocaudal direction –> Code for transcription factors
8
Q
embryology - Homeobox (Hox) genes - mutation
A
appendages in wrong location
9
Q
The Zone of Polarizing Activity (ZPA) is an
A
area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis
10
Q
early fetal development - fetalfertilization occurs at (when and where)
A
day 0 (within 1 day of ovulation) ampulla of the uterine tube (upper end of fallopian tube)
11
Q
early fetal development - fertilization - mechanism
A
sperm binds zona pellucida of the 2ry oocyte arrested in metaphasis of meiosis II –> triggers acrosome reaction (releasing of acrosomal enzymes (acrosin) that aids the sperm to penetrates the zona pellucida) –> cortical reaction (releasing of lysosomal enzymes that changes the oocyte cell membrane potential –> inactivates sperm receptor (polyspermy block)) fusion of both membranes
12
Q
early fetal development - zona pellucida??
A
the thick transparent membrane surrounding a mammalian ovum before implantation.
13
Q
early fetal development - fertilization - mechanism after the fusion of both membranes
A
sperm nuclear –> male pronucleus (and degeneration of tale and mitoch)
nucleus of the ovum –> female pronucleus
THE 2ry oocyte complets meiosis II –> mature ovum
–> Zyngamy
14
Q
early fetal development - Zyngamy?
A
term that describe the succesful completion of fertilization (zygote formation) –> male and female pronuclei fuse and the cytoplasmic machinery for proper cell division exists
15
Q
early fetal development -day of zygote formation
A
day 1
16
Q
early fetal development - zygote life span
A
few hours –> its existence terminates when first cleavage division occurs
17
Q
early fetal development - mechanism from zygote to morula
A
zygotes –> Cleavage (a series of mitotic divisions) –> blastula formation (consisting of cells called blastomeres) –> morula (a cluster of blastomeres 16-32)
18
Q
early fetal development - morula formation - day and location
A
day 4. Location: uterine tube - uterine cavity
19
Q
early fetal development - characteristics of cleavage in humans
A
- holoblastic (divide completely through their cytoplasm - tota)
- asymmetrical (the daughter cells are unequal in size)
- asynchronous (only one cell will divide at a time)
20
Q
early fetal development - blastocyst formation - mechanism/day/topographical anatomy
A
day 5: occurs when fluid secreted within the morula (blastocyst cavity)
inner cell mass are celled embryoblast (pluripotent cells) –> embryo
outer cell masses are called trophoblast –> placenta
21
Q
early fetal development - inner vs outer mass of blastocyst
A
inner cell mass are celled embryoblast (pluripotent cells) –> embryo
outer cell masses are celled trophoblast –> placenta
22
Q
early fetal development - step after blasotcyts formation - mechansim/time/location
A
Implantation (days 6-10): degeneration of zona pelludica –> blastocysts implants within the posterior superior wall of uterus (within the functional layer of the endometrium) –> trophoblast differentiates into cytotrophblast and syncytiotrophoblast
23
Q
trophoblast differentiates into
A
- cytotrophoblast
2. syncytiotrophoblast
24
Q
hCG secretion begins ….(and by)
A
around the time of implantation of blastocyst (within 1 week) by syncytiotrophoblast
25
early fetal development - within week 2 events?
A. embryoblast differentiates into 2 distinct layers: 1. epiblast (dorsal) 2. hypoblast (ventral) (together are known as bilaminar disc)
B. syncytiotrophoblast continues its growth into endometrium (to contact vessels and glands). It does not divide mitotically. The cytotrophoblast divide mitotically, adding to the growth (primary chorinionic villli protrude into the syncytiotrophoblast)
26
early fetal development - bilaminar disc function
1. epiblast --> amniotic fluid/also extraembryonic mesoderm
| 2. hypoblast --> migrate and line cytotrophoblast --> delimit a space --> yolk sac
27
early fetal development - trophoblast within week 2
syncytiotrophoblast continues its growth into endometrium (to contact vessels and glands). It does not divide mitotically. The cytotrophoblast divide mitotically, adding to the growth (primary chorinionic villli protrude into the syncytiotrophoblast)
28
Extraembryonic mesoderm
is a new layer of cells derived from epiblast:
1. Extraembryonic somatic mesoderm --> lines cytotrophoblast --> forms connecting stalk and covers anion
2. Extraembryonic visceral mesoderm --> covers yolk sac
29
early fetal development - week 3 - events
1. Gastrulation
| 2. notochord formation
30
Gastrulation - definition
is the process that establishes the 3 primary germ layers (ectoder,, mesoderm, endoderm), forming a trilaminar embryonic disc
31
Gastrulation - mechanism
cells from epiblast invaginate --> primitive streak in the midline of epiblast --> 1. endoderm 2. mesoderm
3. endoderm
32
mesoderm is found between the
ectoderm (upp) and the endoderm (down)
33
Notochord formation (and function)
arises from midline mesoderm --> induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
34
embryonuc period - when
weeks 3-8
35
All major organ systems begin to develop during the .... causing ...
embryonuc period (weeks 3-8) causing craniocaudal and lateral body folding
36
during the embryonic period, the basic segmentation of the human embryo in craniocaudal direction is controlled by
Homeobox (Hox) gene
37
early fetal development - Weeks 3-8 (embryonic period) events
1. neural tube formed by neuroectoderm and closes by week 4
| 2. organogenesis
38
early fetal development - week 4
1. heart begins to beat
| 2. upper and loweer limb buds begin to form
39
early fetal development - week 6
fetal cardiac activity visible by transvaginal ultasound
40
early fetal development - week 8
fetal movement starts
41
early fetal development - week 10
genitalia have male/female characteristics
42
early fetal development - heart begins to beat and viddible in tranvaginal ultrasound - when
beat --> week 4
| visible in US --> week 6
43
early fetal development - movement starts, genitalia have male/female characteristics , upper and lower limb buds begin to form - when
movement --> week 8
genitalia --> 10
limb buds --> week 4
44
early fetal development - when is extremely susceptible to teratogens
embryonic period (3-8 weeks)
45
Ectoderm is divided to
1. surface ectoderm
2. neuroectoderm
3. Neural crest
46
Surface ectoderm derivatives
1. epidermis
2. anenohypophysis (from Rathke pouch)
3. lens of eye
4. epithelial lining of oral cavity
5. sensory organs of ear
6. olfactory epithelium
7. anal canal below the pentinateline
8. parotid
9. sweet
10. mammary glands
47
neuroectoderm derivatives
1. Brain (neurohypophysis, CNS neuros, oligdendrocytes, astrocytes, ependymal cells, pineal gland)
2. retina
3. spinal cord
4. CN 2
5. Dilator and sphincter pupilae muscles
48
neural crest derivatives
PNS (dorsal root ganglia, cranial nerves, autonomic ganglia, Schwann cells), melanocytes, chromaffin cells off adrenal medulla, parafollicular (C) cells of thyroid, pia and arachnoid, bones of the skukk, odontoblasts, aorticopulmonary septum, endocardial cushions
49
mesoderm derivatives
1. muscle 2. bone 3. connective tissue
4. serous lining of body cavities (eg. peritoneum)
5. spleen (from foregut mesentery) 6. cardiovascular structures 7. lymphatics 8. blood 9. wall of gut tube
10. upper vagina 11. kidneys 12 adrenal cortex 13. dermis 14. testes 15 ovaries
16. Notochord
50
postnatal derivatives of Notochord
nucleus polposus of intervertebral disc
51
Mesodermal defects
```
mneomonic VACTERL
Vertebral defects
Anal atresia
Cardiac defects
Tracheo-Esophageal fistula
Renal defects
Limb defects (bone and muscle)
```
52
Endoderm derivatives
1. Gut tue epithelium (including anal canal above pectinate line)
2. most urethrea and lower vagina(urogenital sinus)
3. luminal epithelial derivtives (lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells
53
Neuroectoderm derivatives (except CNS)
1. retina
2. CN 2
3. Dilator and sphincter pupilae muscles
54
Neural crest derivatives (except PNS)
1. melanocytes
2. chromaffin cells off adrenal medulla
3. parafollicular (C) cells of thyroid
4. pia and arachnoid
5. bones of the skull, odontoblasts
6. aorticopulmonary septum
7. endocardial cushions
55
tumor from surface ectoderm (definition and histology
Craniopharyngioma: benign Rathke pouch tumor with colesterol crystals, calcifications
56
Types of errors in organ morphogenesis
1. agenesis 2. aplasia 3. hypoplasia 4. disruption
| 5. deformation 6. malformation 7. sequence
57
organ agenesis
abesnt organ due to absent primordial tissue
58
A primordium is defined as
an organ or tissue in its earliest recognizable stage of development
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organ Aplasia
absent organ despite presence of primordial tissue (Failure to attain size or function)
60
organ hypoplasia
incomplete organ development - primordial tissue present
61
organ aplasia vs hypolasia
similar but hypoplasia is less severe
62
organ disruption
2ry breakdown of previously normal tissue or structure (eg amniotic band syndrome)
63
organ deformation
extrinsic disruption --> occurs after embryonic period
64
organ malformation
intrinsic disruption --> occurs during embryonic period
65
organ sequence
abnormalities result from a single 1ry embryologic event (eg. oligohydramnioos --> Potter sequence)
66
is derivided from: adenohypophysis, gallbladder, spleen, bone, parafollicular C cells of thyroid, melanocytes, blood, mammary glands, parotid, kidneys
ectoderm: adenohypohysis, parotid, mamary glands
Neural crest: parafollicular C cells, melanocytes
mesoderm: spleen, bone, blood, kidneys
endoderm: gallbladder
67
lens and retina of eye, optic nerve are derived from
lens --> surface ectoderm
| optic nerve, retina --> neuroectoderm
68
thymus, parathyroid, thyroid and adrenals are derived from
chromaffin cells of adrenal medulla, parafollicular (C) cells --> neural crest
thyroid follicular cells, thymus, parathryoid --> endoderm
adrenal cortex --> mesoderm
69
skin is derived from
melanocytes --> neural crest
dermis --> mesoderm
epidermis --> Surface ectoderm
70
epithelial lining of oral cavity, sensory organs of ear and oflactory epithelium are derived from
surface ectoder
71
parotid, sweet parotid glands are derived from
surface ectoder
72
anal canal is derived from
above pectinate line --> endoderm
| below pectinate line --> ectoderm
73
bones, muscles and connective tissue are derived from
bones of skull --> neural crest
| connective tissue muscles, other bones --> mesoderm
74
aorticopulmonary septum is derived from
neural crest
75
cardiovascular structures, lymphatics, blood are derived from
all from mesoderm
| (except aorticopulmonary septum and endocardial cushions --> neural crest)
76
Endocardial cushions refer to
a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa
77
odontoblast are derived from
neural crest
78
pia and dura are derived from
neural crest
79
serous lining of bodies are derived from
mesoderm
80
GI is derived from
```
gut epithelium (including anal canal above pectinate line), liver, gallbladderm pancreas --> endoderm
spleen, gut wall --> mesoderm (foregut mesentery)
```
81
urogenital organs are derived from
upper vagina, kidneys, testes, ovaries --> mesoderm
| most of urethra, lower vagina, eustachian tube --> endoderm
82
vagina and lung are derived from
lungs --> endoderm
upper vagina --> mesoderm
lower vagina endoderm (urogenital sinus)
83
teratogens effects according to period
before week 3 --> all-or-none
3-8 weeks (embryonic period - most suscpetible)
after 8 weeks --> growth and function affected
84
Antibiotics to avoid in pregnancy (and why)
1. Sulfonamides --> Kernicterus
2. Amniglycosides --> Ototoxicity
3. Fluoroquinolones --> Cartilage damage
4. macrolides --> embryotoxic
5. tetracyclines --> DIscolored teeth, inhibiton of growth
6. Chloramphenicol --> Gray babe syndrome
7. Griseofluvin --> teratogenic
8. Ribavirin (antiviral)
85
drugs and substance that affect pregnancy (beside antibiotics) (14)
1. ACE inhibitors 2. Alkylating agents 3. Antiepileptics
4. Diethylstibestrol 5. Folate antagonists
6. Isotretinoin 7. Lithium 8. Methimazol
9. Thalidomide 10. Warfarin 11. Alcohol 12. Cocaine
14. Smoking (nicotine, CO) 15. others factors
86
Other factors that affect fetus
1. iodine (lack or excess)
2. Maternal diabetes
3. Methylmercury
4. Vitamin A excess
5. X-rays
87
Leading cause of low body weight in in developed countries
smoking
88
Leading cause of intellectual disability in USA
Fetal alcohol syndrome
89
Fetal alcohol syndrome - Most severe form
1. heart-lung fistulas
| 2. holoprosnecephaly
90
Dizygotic (fraternal) twins arise from .... (explain)
2 eggs that are sperated by 2 different sperm (2 zygotes) and will have 2 separate amniotic sacs and 2 separate placenta (chorions)
(DICHORIRIONIC DIAMNIOTIC)
91
Dizygotic (fraternal) twins - mechanism - how many eggs, sperms, zygotes, amniatic sacs and placenta
all 2
| DICHORIRIONIC DIAMNIOTIC
92
Monozygotic (identical) twins arise ....(explain)
from 1 ferilized egg (1 egg + 1 sperm) that splits ine early pregnancy. The timing of cleavage determines chorionicity (number of chorions) and amnionicity (number of amnions)
93
Monozygotic (identical) twins - types of process (and proportions)
1. Dichorionic diamniotic (25%)
2. Monochorionic diamniotic (75%)
3. Monochorionic monoamnitotic (rare)
4. Monochorionic monoamniotic (conjoint - rare)
94
Monozygotic (identical) twins - types of process and mechanism (and proportions)
1. Dichorionic diamniotic - if cleavage before morula formation (0-4 days) (25%)
2. Monochorionic diamniotic - if cleavage after morla formation and before blastocyst (4-8 days) (75%)
3. Monochorionic monoamnitotic - if cleavage after blastocyst formation and before bilaminar embryonic disc formation (8-12 days) (rare)
4. Monochorionic monoamniotic if cleavage or axis duplication after bilaminar embryonic disc formation (> 13days) (conjoint - rare)
95
Placenta is formed when
the embryo invades the endometrium of the uterus and when the trophoblast forms villous chorion
96
villous chorion formation goes through stages
primary, secondary, teriary chorionic villi
97
Placenta components are divided to
1. fetal component
| 2. maternal component
98
Placenta - fetal component (and area)
1. cytotrophoblast (inner layer of chorionic villi)
| 2. syncytiotrophoblast (outer layer of chorionic villi)
99
Synctitiotrohoblast - function
synthesize and secretes hormones --> hCG
100
hCG secretion begins ....(and by)/ structure/functiom
```
around the time of implantation of blastocyst (within 1 week) by syncytiotrophoblast
structure: stracturally similar to LH
function --> stimulates corpus luteum to secrete progesterone during first trimester
```
101
Synctitiotrohoblast - special characteristic
lacks MHC I expression --> low chance of attack by maternal immune system
102
Placenta - maternal component
Decidua basalis
103
Placenta - decidua basalis derived from/function
endometrium (between blastocysts and myometrium)
| maternal blood in lacunae
104
substance from maternal circulation to fetal circulation
O2, H20, elctrolytes, nutritiens, hormones, IgG, drugs, viruses
105
microbes that pass from materan to fetal circulation
viruses
106
substance from fetal circulation to maternal lcirculation
CO2, H20, urea, hormones, wasted products
107
chorionic plate
the part of the fetal placenta that gives rise to chorionic villi, which attach to the uterus during the early stage of formation of the placenta.
108
Chorionic villi are
villi that sprout from the chorion to provide maximum contact area with maternal blood.
109
fetal circulation - blood entering fetus through ...
| PO2 and saturation
umbilical vein (O2 rich)
30mmHg
80%
110
fetal circulation - 3 important shunts and puprose
1. ductus venosous --> umbilical vein to IVC (bypass hepatic circulation)
2. foramen ovale --> RA to LA
3. ductus arteriosus --> main pulmonary artery to descending aorta
111
physiologic closure of foramen ovale
at birth, infants take a breath--> decreased resistance in pulmonary vasculature --> increased LA pressure vs RA pressure --> foramen ovale closes
112
fetal circulation - 3 important shunts and their postnatal derivatives
1. ductus venosous --> ligamentum venosum
2. foramen ovale --> fossa ovalis
3. ductus arteriosus --> ligamentum arteriosum
113
hCG detection (when)
maternal blood at 1 week
| maternal urine at 2 week (home test)
114
umbilical cord - definiton
conduit between the developing embryo or fetus and the placenta
115
umbilical cord - structure (and contains)
two arteries (the umbilical arteries) and one vein (the umbilical vein), allantoic duct, buried within Wharton's jelly, surrounded by amnitotic epithelium (cord lining membrane)
116
umbilical vein drains into IVC via
liver or via ductus venosus
117
umbilical arteries return deoxygenated blood from .... to .....
fetal internal iliac arteries to placenta
118
umblical vein + umbilical arteries - postnatal derivatives
umblical vein --> Ligamentum teres hepatis (Round ligament)
| umbilical arteries --> medial umbilical ligaments
119
Umbilical arteries and vein are derived from
allantois
120
allanotis urachus correlation
urachus is part of allantoic duct between bladder and umbilicus
121
allantois (-->urachus) - postnatal derivatives
Median umbilical ligament
122
Single umbilical artery (2 vessel cord) is associated with
congenital and chromosomal anomalies
123
Urachus - everything
in 3rd week the yolk sac forms the allantois --> extentds into urogenital sinus --> Allantois becomes the urachus, a duct between fetal bladder and umbilicus
124
urachus?
a duct between fetal bladder and umbilicus
125
pathology associated with urachus
1. patent urachus
2. urachal cyst
3. Vesicourachal diverticulum
126
patent urachus - mechanism
total failure of to obliterate --> urine discharge from umbilicus
127
urachal cyst - mechanism
partial failure of to obliterate --> fluid-filled cavity lined with uroepithelium, between umbilivus and bladder
128
urachal cyst - complications
1. infections
| 2. adenocarcinoma
129
Vesicourachal diverticulum - mechanism
slight failure of urachus to obliterated --> outpouching of bladder
130
not a neural structure derived from neuroectoderm
dilator and sphincter papilae muscles
131
vitelline duct - AKA/definition
omphalomesenteric duct
| long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus
132
fate of vitelline duct
obliteration at 7 weeks
133
disease associated with vitelline duct
1. vitelline fistula
2. Meckel diverticulim
3. omphalomesenteric cysts
134
vitelline fistulla - presentation
meconium discharge
135
Meckel diverticulum the rule of 6 2s
```
2 times as likely in males
2 inches long
2 feet from ileocecal valce
2% of population
present in first 2 yeras of life
may have 2 types of epithelial (gastric/pancreatic)
```
136
meckel diverticulum - mechanism presentation
1. melena (or hematochezia) 2. RLQ pain 3. intussusception 4. volvulus
5. obstruction near terminal ileum (mimics appendicitis)
MC asymptomatic
137
twinning - dizygotic (fraternal) vs monozygotic according to frequency
dizygotic (fraternal) --> 2/3
| monozygotic --> 1/3
