Flashcards in 2017 Embryology Revision Deck (31):
1
Embryology week 1
Explain what happens during days 3, 5 and 6
Day 3: morula is formed
Day 5: blastocyst is formed, via a cavity and cell layer being formed
Day 6: implantation into the uterine lining
2
Embryology week 2
1. What 3 things happen on day 8?
2. What forms on day 9?
3. On day 13, what is there cavitation of and what does this form?
1. Syncytiotrophoblast invades the endometrium
Bilaminar disc is formed (epiblast and hypoblast)
Amniotic cavity is formed
2. Primary yolk sac
3. Cavitation of extraembryonic mesoderm
Forms chorionic cavity
3
Embryology week 3
Day 15
1. What happens?
2. What does this form?
3. Where does it extend from and to?
1. Indentation of ectoderm
2. Forms primitive streak
3. From primitive node to cloacal membrane
4
Embryology week 3 - days 14-19
What process occurs?
Gastrulation
5
Embryology week 3 - days 14-19 - gastrulation
1. Where do cells migrate from?
2. Where do they go?
3. What is formed?
1. Primitive streak
2. Between the epiblast and the hypoblast
3. Intraembryonic mesoderm
6
Embryology week 3 - days 14-19 - gastrulation
1. What does ectoderm become?
2. What does endoderm become?
3. What does mesoderm become?
1. Ectoderm: skin and neural tissue
2. Endoderm: epithelial lining of gut, respiratory and urinary systems
3. Mesoderm: muscle, bone, connective tissue, some organs and lining of body cavities
7
Embryology - somites
1. Days?
2. How do they appear?
3. Nervous supply spread?
1. Days 20-30
2. Appear sequentially
3. Each supplied by a single spinal nerve
8
Embryology- Neurulation
1. Days?
2. The notochord forms from what?
3. What does the notochord form within?
4. What does the notochord induce the formation of?
5. What does the notochord become?
1. Days 19-25
2. Primitive node cells
3. Mesoderm
4. Neural plate
5. Nucleus pulposus of IV discs
9
Embryology- neurulation
1. What is neurulation?
2. What is the simple 3 step process?
3. What closes on day 25?
4. What closes on day 27?
1. Formation of neural tube
2. Neural plate forms
Folds to form neural groove
Then neural tube forms
3. Cranial neuropore
4. Caudal neuropore
10
Embryology - neural crest cell migration
1. What happens to these cells?
2. Name 4 things that these cells are involved in
3. Name 3 things that can go wrong with defective migration
1. Re-differentiate into other cell types
2. Heart septation, face and skull connective tissues, GI tract ganglia and melanocytes
3. Malformed face, nervous system absences and cardiac/gut defects
11
Embryology - neural tube defects
What is spina bifida?
Defective neural tube closure and anomalies of the covering tissues
12
Embryology- limbs
1. Between which weeks?
2. Which appear first and how long before the other?
3. How are the digits formed?
1. Weeks 4-8
2. Upper limb buds 36 hours before lower
3. Programmed cell death
13
Embryology- folding
1. What are the 2 types of folding?
2. What causes the head to fold?
3. When does folding occur?
1. Lateral folding and cephalo-caudal folding
2. Rapid growth of brain and limited space available
3. Weeks 3-4
14
Embryology - lateral folding
What is drawn around the entire disc?
Amniotic cavity
15
Embryology
What is the intraembryonic coelom and what does it become?
Cavity within mesoderm
Becomes body cavity
16
Embryology- teratogenesis
1. Define teratogenesis
2. When is the embryo at risk of a structural abnormality and why?
3. When is the embryo at risk of a functional abnormality?
4. What happens before week 3?
1. Abnormality induced in developing embryo by harmful, foreign substances
2. Weeks 3-8 because this is when cell division, organogenesis and midline union takes place
3. Week 8 onwards
4. Embryo will self-abort
17
Embryology- teratogens
Name 5 common teratogens and give 1 outcome for each
1. Alcohol: fetal alcohol syndrome
2. Vitamin A: cleft palate
3. Maternal diabetes: heart and neural tube defects
4. Rubella: deafness
5. X-rays: spina bifida
18
Embryology - teratogens
Name 5 basic mechanisms of teratogens
1. Mutations in DNA
2. Interruption of DNA/RNA synthesis
3. Failure of normal cell to cell interactions
4. Interfering with cell differentiation
5. Chromosomal abnormalities
19
Embryology- lungs
1. When does the respiratory diverticulum first develop and what is it an outgrowth of?
2. Its an out pouching of what?
3. What does the trachea, bud grow into at 4-5 weeks?
4. Which septum forms next?
5. How many bronchial buds form on the right and how many form on the left?
1. 4 weeks: outgrowth of foregut
2. Outpouching of endoderm
3. Splachnopleuric mesoderm
4. Tracheo-oesophageal septum
5. Right = 3
Left = 2
20
Embryology- lung bud division
1. What are the 4 main divisions of the lung bud and what does each one produce?
2. What happens at 6 months that allows the air spaces to inflate?
1. Primary - main bronchi
Secondary - lobar bronchi
Segmental bronchi
Intrasegmental bronchi
2. Surfactant produced
21
Embryology- What are the steps of heart development and when does it start?
Mid week 3
Cardiogenic mesoderm develops
Cords of angioblastic cells
Forms 2 primitive heart tubes on either side
When the embryo folds, the tubes fuse
22
Embryology- heart
1. What turns the heart tube 180 degrees?
2. When does the heart grow into (and get completely surrounded by) pericardium?
3. What are the 2 pericardial sinus's?
4. With regards to the heart tubes, what happens at 20 days, 21 days and 23 days?
1. Longitudinal folding
2. Week 4
3. Transverse pericardial sinus and oblique pericardial sinus
4. 20 days: paired heart tubes
21 days: fusion
23 days: large single heart tube
23
Embryology- Primitive heart tube
1. What 2 things are at the venous end?
2. What 1 thing is at the arterial end?
3. Name the 5 sections of the primitive heart tube from the venous end to the arterial end
1. Right horn and left horn
2. Aortic sac
3. Sinus venosus
Atrium
Ventricle
Bulbis cordis
Truncus arteriosus
24
Embryology- primitive heart tube
What do the following things become:
1. Sinus venosus?
2. Atrium?
3. Ventricle?
4. Bulbis cordis?
5. Truncus arteriosus?
1. Sinus venosus = smooth wall of RA
2. Atrium = rough wall of RA and LA
3. Ventricle = rough part of LV
4. Bulbus cordis = rough part of RV and outflow tracts for RV and LV
5. Truncus arteriosus = roots of aorta and pulmonary trunk
25
Embryology- septum in heart tube
Explain what the following changes into once the septum separates the heart tube:
Right horn and left horn
Sinus venosus
Atrium
Ventricle
Bulbus cordis
Truncus arteriosus
Vena cavae and coronary sinus
Sinus venosus
RA and LA
RV and LV
R outflow tract and L outflow tract
Pulmonary trunk and aorta
26
Embryology- folding heart tube
1. At 22 days how does the growing bulbis cordis move?
2. At 24 days how does the heart shift?
1. Infero-anteriorly
2. Postero-superiorly
27
Embryology - AV canal
Explain how the AV canal is partially seperated
AV canal enlarges
Swelling in endocardial cushions grow ventrally and dorsally
Meet in the middle to partially separate the AV canal
28
Embryology- atrial septation
Explain the 4 stages of atrial septation and give the time frame they occur within
Weeks 4-5
1. Septum primum forms with ostium primum at the bottom
2. Ostium secondum forms on a part at the top
3. Spetum secondum is formed
4. Causes a foramen ovale to be formed (R-L shunt in utero)
29
Embryology- ventricular septation
1. When does it occur?
2. What 3 things is the septum made of?
3. Which direction does the muscle section go in and where is it incomplete?
4. What completes this region?
1. Week 5-7
2. Muscle, membrane and endocardial cushion
3. Muscle goes towards endocardial cushion and is incomplete in the cranial region
4. Bulbar ridges growing down
30
Embryology- Tetralogy of Fallot
1. What are the 4 things involved in the tetralogy of fallot?
2. What do they cause?
1. Pulmonary stenosis
RV hypertrophy
Over-riding aorta
VSD
2. Cyanosis (deoxygenated blood entering arterial circulation) and Tet spell
31