Embryology Flashcards
(109 cards)
1
Q
What is the conceptus called during weeks 1-2 of development?
A
Zygote
Morula
Blastocyst
2
Q
What are the major events that occur during weeks 1-2 of development?
A
Fertilization
Implantation
3
Q
What weeks do the embryonic period refer to?
A
Weeks 3-8
4
Q
What is the conceptus referred to during weeks 3-8?
A
Embryo
5
Q
What is the major event during weeks 3-8?
A
Organogenesis
6
Q
What do weeks 9-38 refer to?
A
Fetal period
7
Q
What is the conceptus named during weeks 9-38?
A
Fetus
8
Q
What major events occur during weeks 9-38?
A
Growth
Maturation
9
Q
Describe the control of development:
A
10
Q
Teratology:
A
Study of abnormal development
11
Q
Birth defect:
A
Birth defect = Congenital abnormality = Congenital anomaly = abnormality present at birth.
12
Q
Malformation:
A
Developmental structural abnormality arising in embryonic period (weeks 3-8).
13
Q
Deformation:
A
Developmental structural abnormality 2ndary to extrinsic disruption after embryonic period
14
Q
Sequence:
A
Multiple abnormalities all developing in a sequence
15
Q
Syndrome:
A
Multiple abnormalities developing in no known sequence
16
Q
What normally occurs during the pre-fertilization stage of development?
A
Normal development : Meiosis produces egg and sperm.
Abnormal development : Genetic abnormalities
- Example : Downs syndrome (Trisomy 21)
17
Q
Describe broad results of normal vs abnormal development during weeks 1 and 2:
A
Normal development of fertilized egg:
- Mitosis
- Move to uterus
- Begin implantation in uterine wall
Abnormal development :
- Not susceptible to teratogens.
- So, abnormal development is 2ndary to inherited.genetic abnormalites.
- ~40-50% of all conceptuses spontaneously abort (= miscarriage) during these weeks 2ndary to lethal genetic abnormalities.
18
Q
What is a miscarriage?
A
loss of an embryo or fetus before the 20th week of pregnancy (before it is viable).
19
Q
Broadly describe the results of normal vs. abnormal development during the embryonic period (weeks 3-8):
A
Normal development :
- Form organs (Organogenesis)
Abnormal development :
- Susceptible to all types of birth defect etiologies.
- This is the most vulnerable time for the embryo
- Major anomalies develop since development of a structure is disrupted when it is made of only a few cells. These now-abnormal cells then build an abnormal organ.
20
Q
Broadly describe the results of normal vs. abnormal development during the fetal period:
A
Normal development:
- Growth and maturation
Abnormal development:
- Susceptible to all types of birth defect etiologies.
- Minor anomalies develop since development of a structure is disrupted when it is already nearly fully formed.
21
Q
What direction does development occur in?
A
Cranial –> caudal
Proximal –> distal
22
Q
What are the conventional views of a developing conceptus?
A
23
Q
The placenta essentially functions as the ___, ___ and ____ for the fetus. Explain.
A
The placenta functions as the fetal lungs, kidneys and GI tract.
The placenta is a vascular structure formed by the embryo. In it maternal blood releases nutrients and O2 into the fetal blood, and fetal blood releases wastes into the maternal blood.
24
Q
Does fetal and maternal blood mix via the placenta?
A
No
25
Where does fetal urination occur?
Into the amniotic fluid
26
What does the fetus breathe?
Amniotic fluid
27
Where does the fetus defecate in utero?
The fetus does not defecate in utero
28
What occurs during Week 1 of development?
Fertilization
Cell division (mitosis)
Zygote → Morula → Blastocyst
Implantation in uterus
29
What occurs during week 2 of development?
-The inner cell mass forms 2 layers (bilayer)
* Epiblast --\> embryo
* Hypoblast --\> disappear
- Amniotic cavity appears.
- A primitive streak is formed
* forms in the epiblast
* Dorsal, caudal midline
30
Gastrulation:
Process of forming the 3 germ layers from the primitive streak.
Ectoderm, Mesoderm, Endoderm
31
Trilaminar embryo are formed from \_\_\_\_\_
the three germ layers
32
What is somite formation?
The formation of horizontal body segments
33
What is neurulation?
The formation of the nervous system
34
What 4 things occur during Week 3 of development?
Gastrulation
Trilaminar embryo
Somite formation
Neurulation
35
Mitosis of the epiblast occurs at the \_\_\_\_, resulting in the formation of new cells, which migrate under the _____ layer and form two new layers, the ___ and \_\_\_.
Mitosis of the epiblast occurs at the **primitive streak**, resulting in the formation of new cells, which migrate under the **epiblast** layer and form two new layers, the **mesoderm** and **endoderm**.
36
What structures arise from the ectoderm?
outer layer of skin (epidermis) and teeth (enamel), nervous system
37
What structures arise from the mesoderm?
muscle (all types), bone, connective tissues, blood and blood vessels, deeper layer of skin (dermis)
38
What structures arise from the endoderm?
Epithelial lining of GI and respiratory tracts
39
Mesenchyme:
Aggregates of undifferentiated cells (mostly from mesoderm)
40
Somites:
horizonal body segments (trunk, limb) composed of skin, muscle, bone, connective tissue
(color schemes in pictures are different)
41
Horizontal body segments form from _____ during somite formation.
Horizontal body segments form from **mesoderm (paraxial)** during somite formation.
More somites are added at the caudal end.
42
In their horizontal territory, each somite divides into (3):
Dermatome → skin dermis
Myotome → muscle
Sclerotome → bone
43
What occurs during week 4 of development?
Organogenesis
* Folding : Longitudinal, Transverse
* Germ layer differentiation
* Pharyngeal arches
* Heart forms and begins beating
* 4 limbs begin developing
44
Week 4 begins with a ___ embryo. Folding creates a ___ trunk and moves the heart into the \_\_\_\_\_.
Week 4 begins with a **flat** embryo. Folding creates a **3D** trunk and moves the heart into the **newly formed thorax**.
45
During longitudinal folding, the cranial and caudal ends fold \_\_\_\_\_, which moves the heart from cranial into the new thorax.
Transforms the conceptus from a flat embryo to a \_\_\_-shaped embryo.
During longitudinal folding, the cranial and caudal ends fold **ventrally**, which moves the heart from cranial into the new thorax.
Transforms the conceptus from a flat embryo to a **C**-shaped embryo.
46
During ____ folding, the lateral sides of the embryo fold ventrally until they meed and fuse in the ventral/anterior midline.
During **transverse** folding, the lateral sides of the embryo fold ventrally until they meed and fuse in the ventral/anterior midline.
47
Transverse folding creates body cavities (called \_\_\_) and the \_\_\_\_.
Transverse folding creates body cavities (called **coelom**) and the **GI tract**.
48
At the beginning of Week \_\_\_, most major organ systems are present but rudimentary. During these weeks there is continued development of structures → fairly mature by end of Week 8.
Week 5
49
Major congenital abnormalities are most likely to arise during developmental weeks ___________ to \_\_\_\_\_\_\_\_\_\_\_
Major congenital abnormalities are most likely to arise during developmental **weeks 3 to 8**
50
The inner cell mass gives rise to the \_\_\_\_\_\_\_\_, whereas the trophoblast gives rise to the ________ .
The inner cell mass gives rise to the **fetus**, whereas the trophoblast gives rise to the **placenta**.
51
Growth and maturation of organs is the major event during developmental weeks __________ to __________ .
Growth and maturation of organs is the major event during developmental **weeks 9 to 38**
52
Implantation of the conceptus into the uterus begins during developmental week _________ .
Implantation of the conceptus into the uterus begins during developmental **week** **1.**
53
Formation of the GI tract takes place by _______ folding during developmental week \_\_\_\_\_\_\_\_.
Formation of the GI tract takes place by **transverse** folding during developmental **week 3.**
54
Match the week of development in column A with a structure/process in column B:
## Footnote
**Column A Column B**
Week 2 Gastrulation
Week 4 Implantation
Week 1 Longitudinal folding
Week 3 Bilaminar conceptus
Week 1 - Implantation
Week 2 - Bilaminar conceptus
Week 3 - Gastrulation
Week 4 - Longitudinal folding
55
Categorize this list of structures as deriving from either mesoderm, ectoderm, or endoderm:
* Bone
* Lining of GI tract
* Muscle
* Nervous system
* Blood
* Epidermis
* Skin dermis
* Lining of respiratory tract
Mesoderm:
* Muscle
* Blood
* Bone
* Skin dermis
Ectoderm:
* Nervous system
* Epidermis
Endoderm:
* Lining of GI tract
* Lining of respiratory tract
56
What key things occur in week 4 of development in regards to cardiac development?
Folding - longitudinal and transverse
Heart forms and begins beating
57
Conceptus begins week 4 as a ____ embryo
flat
58
\_\_\_\_\_ folding moves the heart into the newly formed thorax during week 4.
Longitudinal
59
Longitudinal folding moves the ____ into the newly formed thorax during week 4.
heart
60
Longitudinal folding moves the heart into the newly formed ____ during week 4.
thorax
61
\_\_\_\_\_\_ folding creates a 3-D trunk. This brings the right and left sides together in ventral midline.
Transverse
62
Transverse folding creates a \_\_\_\_. This brings the right and left sides together in ventral midline.
3-D trunk
63
Transverse folding creates a 3-D trunk. This brings the right and left sides together in _____ midline.
ventral
64
Describe the steps of development of blood-carrying vessels:
Mitosis of mesoderm cells (called angioblasts) --\> clusters everywhere
Lumens develop
Vessel walls create blood cells. Later, blood cells arise in liver, spleen and bone marrow.
Fusion of neighbor vessels, to form network of interconnected vessels.
65
What layers do vessels form in?
All layers (mesoderm,
66
By week \_\_\_, the embryo is already large enough to need heart and vessels to carry blood everywhere. The heart pumps blood to the ___ and ____ via arteries and veins.
By week **4**, the embryo is already large enough to need heart and vessels to carry blood everywhere. The heart pumps blood to the **body** and **placenta** via arteries and veins.
67
The entire process of heart development takes ___ weeks.
5.5 weeks
68
The heart starts as a right and left \_\_\_\_, called \_\_\_\_.
The heart starts as a right and left **blood vessel**, called **cords**.
69
The ____ is the most cranial structure of the early embryo
heart
70
Transverse folding during week ___ brings the 2 cords together in anterior midline, which fuse and create one heart \_\_\_. It develops all 3 layers. (\_\_\_\_, \_\_\_\_\_, and \_\_\_\_\_)
Transverse folding during week **4** brings the 2 cords together in anterior midline, which fuse and create one heart **tube**. It develops all 3 layers. (**myocardium**, **epicardium**, and **endocardium**)
71
The heart tube begins to beat on day \_\_\_\_.
22 or 23
72
What is the order of blood flow through the heart tube?
Sinus venosus --\> atrium --\> ventricle --\> bulbus cordis --\> truncus arteriosus
The heart tube is a single, straight tube (no right and left divisions inside yet).
It is subdivided into the regions above.
73
The sinus venosus will become \_\_\_.
part of the right and left atria
74
The bulbous cordis becomes \_\_\_\_\_.
part of the right and left ventricles
75
the truncus arteriosus becomes \_\_\_.
The aorta and pulmonary trunk
76
What are the 5 structures important for atrial subdivision?
2 sequential septa; 3 sequential openings:
Septum primum
Foramen primum
Foramen secundum
Septum secundum
Foramen ovale
(always need a hole in the wall between the atria)
77
The septum primum grows from the ___ to the \_\_\_\_.
endocardial cushion
78
The first hole formed during atrial subdivision is called WHAT?
The foramen primum
79
A second septum, called the ______ grows to the ____ of the first (septum primum), from the roof to the endocardial cushion during atrial subdivision.
A second septum, called the **septum secundum** grows to the **right** of the first (septum primum), from the roof to the endocardial cushion during atrial subdivision.
80
What is the name of the hole formed in the septum secundum?
Foramen ovale
81
Describe the 6 steps of the formation of 5 structures during atrial subdivision:
1. **Septum primum** grows from roof to endocardial cushion. (1,2,3)
2. Always need a hole. 1st is named **Foramen primum**. It disappears. (2,3,4)
3. Holes form in the septum. (3)
4. Coalesce to form 1 hole. Named **Foramen secundum**. (4)
5. A second septum grows on the right side of the first, from roof to endocardial cushion. Named **Septum secundum**. (5,6)
6. This septum has a hole, named **Foramen ovale**. This septum covers the Foramen secundum. (6)
82
Describe the blood flow through the heart after the completion of atrial subdivision:
Blood flows from the right atrium --\> foramen ovale --\> foramen secundum --\> left atrium.
This occurs due to pressure differences in the atria.
83
The Septum ___ is pushed to the left and acts as an open valve of the foramen \_\_\_.
The Septum **primum** is pushed to the left and acts as an open valve of the foramen **ovale**.
84
(Ventricle subdivision) The interventricular _____ grows from the floor to the endocardial cushion, closing the interventricular \_\_\_\_\_\_.
(Ventricle subdivision) The interventricular **septum** grows from the floor to the endocardial cushion, closing the interventricular **foramen**.
85
Most mistakes during ventricle subdivision occur near the \_\_\_\_\_\_\_\_.
endocardial cushion
86
The atrioventricular valves arise from the \_\_\_\_\_\_.
endocardial cushion
87
The truncus arteriosus subdivides into the ____ and the \_\_\_\_\_.
The truncus arteriosus subdivides into the **aorta** and the **pulmonary trunk/artery**.
88
The ____ subdivides into the aorta and the pulmonary trunk/artery.
The **truncus arteriosus** subdivides into the aorta and the pulmonary trunk/artery.
89
The division of the truncus arteriosus into the aorta and the pulmonary trunk/artery requires forming a ______ and requires ______ to achieve the final positions.
The division of the truncus arteriosus into the aorta and the pulmonary trunk/artery requires forming a **longitudinal septum** and requires **twisting** to achieve the final positions.
90
What are the two key differences between prenatal vs. postnatal circulations?
Prenatal: The fetus is attached to the vascular structure, the **placenta**, where gases, nutrients and wastes are exchanged with the maternal blood.
Prenatal: The **fetus** **does not use its lungs** for breathing, so they don’t need much blood.
91
What are the 6 structures necessary uniquely for in-utero circulation?
2 arteries: **Umbilical arteries** (iliac artery → placenta)
1 vein: **Umbilical vein** (placenta → Inf. Vena cava)
3 shunts:
* **Ductus venosus** to help umbilical vein bypass liver
* **Oval foramen** between heart atria to bypass pulmonary circulation. Blood flows right atrium → left atrium (right-to-left shunt)
* **Ductus arteriosus** between pulmonary artery and aorta to bypass pulmonary circulation. Blood flows pulmonary artery → aorta (right–to left shunt)
92
What is the purpose of the ductus venosus?
Helps the umbilical vein bypass the liver
93
What is the purpose of the oval foramen?
Allows blood to flow through the right atrium into the left atrium (right to left shunt) to bypass the pulmonary circulation.
Most IVC blood passes through foramen → LA → LV → aorta → upper body
Most SVC blood passes RA → RV → pulm.artery
94
What is the function of the ductus arteriosus?
Located between the pulmonary artery and aorta to bypass pulmonary circulation. The blood flows through the pulmonary artery → aorta (right–to left shunt).
95
What is the remnant of the umbilican vein called?
Ligamentum teres
96
What are the remnants of the umbilical arteries called?
Medial umbilical ligaments
97
What is the remnant of the ductus venosus?
Ligamentum venosum
| (Closes at birth, premanent by 1 week)
98
What is the remnant of the oval foramen?
**Oval fossa**
(Closes at birth by septum primum valve; permanent by ~5 years)
99
What is the remnant of the ductus arteriosus?
**Ligamentum arteriosum**
Constricts by 10 hours. Closes by 24 hours.
Permanent by 1-2 months.
Can close clinically with Indomethacin, or keep open with prostaglandins E1 and E2.
100
The ductus arteriosus can be clinically kep open with \_\_\_\_.
Prostaglandins E1 and E2
101
The ductus arteriosus can be clinically closed with \_\_\_\_\_.
Indomethacin
102
The germ layer named _____ gives rise to the heart, arteries, and veins
mesoderm
103
The normal shunting of blood in the pre-natal heart moves blood from _____ atrium to ____ atrium through holes named _______ and ______ and \_\_\_\_\_\_\_.
The normal shunting of blood in the pre-natal heart moves blood from **right** atrium to **left** atrium through holes named **foramen primum** and **foramen secundum** and **foramen ovale.**
104
The structure in the embryonic heart to which the interatrial and interventricular septa both attach is the \_\_\_\_\_\_\_\_.
The structure in the embryonic heart to which the interatrial and interventricular septa both attach is the **endocardial cushion.**
105
The heart tube starts to beat during Week ___ of development.
The heart tube starts to beat during **Week 4** of development.
106
The truncus arteriosus gives rise to two major arteries named _____ and \_\_\_\_.
The truncus arteriosus gives rise to two major arteries named **pulmonary trunk/artery** and **aorta**.
107
Put this list of structures in the order in which blood flows through them:
Bulbus cordis, Atrium, Truncus arteriosus, Sinus venosus, Ventricle
Sinus venosus→ Atrium → Ventricle → Bulbus cordis → Truncus arteriosus
108
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