Embryology Flashcards

1
Q

What are the 7 stages of embryology?

A
Pre-embryonic: 0-3 weeks 
Embryonic: 4-8 weeks
Foetal: 9-40 weeks
Post-natal
Childhood
Adolescence
Adulthood
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2
Q

What is produced in one cycle of spermatogenesis?

A

4 sperm

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3
Q

What is produced in one cycle of oogenesis?

A

1 ovum + 3 polar bodies

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4
Q

What is gametogenesis?

A

Biological process in which diploid or haploid cells undergo meiosis to form mature haploid gametes

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5
Q

Where are gametes formed?

A

Gonads e.g. testicles and ovaries

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6
Q

What are the 2 types of gametogenesis?

A

Spermatogenesis

Oogenesis

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7
Q

What is facilitation in terms of fertilisation?

A

Need for hundreds of sperm to surround the egg for fertilisation

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8
Q

Describe fertilisation

A

Sperm penetrates ovum, and the pro-nucleus of the sperm fuses with the pro-nucleus of the ovum to form a diploid cell called the zygote

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9
Q

What is a morula?

A

When zygote has split to become a 16 cell entity

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10
Q

Name a maternally inherited mitochondrial disease which causes blindness

A

Leber’s hereditary optic neuropathy

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11
Q

Describe a blastocyst

A

The blastocyst is a structure formed in the early development of mammals. It possesses an inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast

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12
Q

How long does the 1st cell division take?

A

36 hours

2nd - 24hr
3rd - 12 hours

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13
Q

What is an ectopic pregnancy?

A

When the embryo implants abnormally outside the womb, usually in the fallopian tubes. Can be dangerous, and usually due to abnormal cilia function

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14
Q

What are the signs of ectopic pregnancy?

A

Vaginal bleeding
Stomach pain
Pain in the tip of your shoulder

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15
Q

What is a chorion?

A

Outer membrane of embryo has a villi (chorionic villi) which is vital for implantation. Also forms part of the placenta later on, and secretes human chorionic gonadotrophin (HCG)

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16
Q

What is used to detect pregnancy in home tests?

A

Human chorionic gonadotrophin, released from the chorion to tell the ovaries to continue making oestrogen and progesterone

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17
Q

What is HCG?

A

Human chorionic gonadotrophin, released from the chorion to tell the ovaries to continue making oestrogen and progesterone to maintain the endometrium

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18
Q

What is the decider basalis?

A

Part of endometrium deep to the implanted conceptus, where the maternal side of the placenta is found

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19
Q

When is HCG released from the chorion?

A

first 12 weeks of pregnancy, then the placenta starts secreting

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20
Q

What two cavities are then formed following the formation of the bilaminar disc in the embryo?

A

Amniotic cavity - above epiblast (nearer placenta)

Yolk sac - below hypoblast

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21
Q

What is the function of the allantoic cavity?

A

Gas exchange and removal of liquid waste

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22
Q

what are the 3 main functions of the placenta?

A

foetal nutrition
transport of waste and gases
immune protection

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23
Q

Describe the texture of the foetal and maternal side of the placenta

A

Foetal - smooth

Maternal - rough, on decidua basalis

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24
Q

When does the placenta become fully mature?

A

18-20 weeks

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25
What is gastrulation?
Formation of the germ layers
26
What is neurulation?
Formation of neural tube
27
Where is the primitive streak found?
Midline of epiblast by the dipping in of cells
28
When is the axis of the embryo determined?
After formation of primitive streak: - head end = above epiblast - tail end = below hypoblast
29
What forms the 3 germ layers?
Migration of epiblast cells which displace hypoblast cells, forms trilaminar disc
30
What are the 3 germ layers?
Ectoderm - hair, nails, epidermis Mesoderm - muscle, bone, connective tissue, fat Endoderm - internal organs e.g. lungs
31
What forms the notochord?
Migration of cells from primitive streak into midline, which encourages the formation of the neural tube from the ectoderm
32
Describe neurulation
Notochord induces ectodermal cells in the midline to invaginate down into the midline and form a neural tube/plate, which is located above the notochord
33
What effect does the neural tube have on the mesoderm?
Stimulates mesoderm to thicken, and separate into 3 parts: - paraxial mesoderm (closest to tube) - intermediate mesoderm - lateral plate mesoderm
34
What does the lateral plate mesoderm split into?
Somatic and splanchnic mesoderm, which forms the body cavity and coverings
35
What does the intermediate mesoderm become later on?
Urogenital system (kidneys and reproductive tract)
36
What does the paraxial mesoderm split into?
Somites, which each splits into: - dermatome: dermis - myotome: skeletal muscle - sclerotome: bones - syndetome: cartilage and tendons
37
How many pairs of somites are there?
43 pairs
38
When does the heart start to beat?
24 days
39
What is the cavity between the somatic and splanchnic mesoderm of the lateral plate mesoderm?
Intraembryonic coelom
40
Describe the teratogenic effects of thalidomide
Phocomelia
41
Which enantiomer of thalidomide is harmful?
S-enantiomer
42
List some environmental teratogens
Drugs Alcohol/tobacco Infectious agents e.g. rubella Other: radiation
43
When during pregnancy are teratogens most likely to kill foetus?
week 1-2
44
When during pregnancy are teratogens likely to cause great damage to organs/systems?
week 3-8
45
What does the risk imposed by a teratogen depend on?
Time of exposure Dose Genetic susceptibility
46
When does the respiratory system start to form?
4th week, respiratory diverticulum appears on day 26
47
What does the respiratory primordial (lung bud) grow from?
Ventral wall of foregut, median outgrowth called the laryngotracheal groove (diverticulum)
48
What forms between the growing oesophagus and trachea, before completely separating them?
Oesophagotracheal septum
49
What results from the incomplete separation of the trachea and oesophagus?
Tracheoesophageal fistula and atresia of the oesophagus
50
What is atresia?
When an orifice or passage in the body is abnormally closed or absent
51
What forms the visceral lung pleura?
Splanchnic mesoderm
52
What forms the parietal lung pleura?
Somatic mesoderm
53
What are the 3 main stages in lung differentiation?
Embryonic - primordial buds out of the foregut Foetal: - Pseudoglandular: cells become gland like - Canalicular: elongate into canals - Saccular: canals widen into sacs - alveolar: sacs bud into alveoli Postnatal - continuation of alveolar budding
54
When do vascular connections and pneumocyte cell types develop?
foetal period
55
When is the alveolar stage of foetal lung development?
32 weeks - 8 years old
56
When is the canalicular stage of foetal lung development?
17-27 weeks
57
When is the saccular stage of foetal lung development?
27-40 weeks
58
What are some congenital lung conditions?
ARDS Accessory lobes Agenesis of the lung Azygos lobe
59
What 4 embryonic components make up the diaphragm?
Septus transversum - central tendon Pleuroperitoneal membranes - prim. diap. Dorsal mesentery of the diaphragm - medial portion and crura Muscular ingrowth of lateral thoracic body walls - peripheral diaphragm
60
Which somites is the septum transverse found alongside?
C3-C5 (phrenic nerves)
61
What are the 3 main congenital abnormalities of the diaphragm?
Failure of complete closure Herniation Pulmonary hypoplasia
62
What are the 3 types of congenital hernia?
Posterolateral (Bochdalek) Anterior (Morgagni) Central
63
What type of hernia is not congenital?
Hiatal hernia
64
What are the three main sites of hiatal hernia?
Descending aorta T12 Oesophagus T10 Vena cava T8
65
What are the two types of oesophageal hernia?
``` Sliding hiatus hernia - slides out Paraesophageal hernia ("rolling") - rolls out ```