Embryology

Question 1

What are the 7 stages of embryology?

Answer 1

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

Question 2

What is produced in one cycle of spermatogenesis?

Answer 2

4 sperm

Question 3

What is produced in one cycle of oogenesis?

Answer 3

1 ovum + 3 polar bodies

Question 4

What is gametogenesis?

Answer 4

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

Question 5

Where are gametes formed?

Answer 5

Gonads e.g. testicles and ovaries

Question 6

What are the 2 types of gametogenesis?

Answer 6

Spermatogenesis

Oogenesis

Question 7

What is facilitation in terms of fertilisation?

Answer 7

Need for hundreds of sperm to surround the egg for fertilisation

Question 8

Describe fertilisation

Answer 8

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

Question 9

What is a morula?

Answer 9

When zygote has split to become a 16 cell entity

Question 10

Name a maternally inherited mitochondrial disease which causes blindness

Answer 10

Leber’s hereditary optic neuropathy

Question 11

Describe a blastocyst

Answer 11

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

Question 12

How long does the 1st cell division take?

Answer 12

36 hours

2nd - 24hr
3rd - 12 hours

Question 13

What is an ectopic pregnancy?

Answer 13

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

Question 14

What are the signs of ectopic pregnancy?

Answer 14

Vaginal bleeding
Stomach pain
Pain in the tip of your shoulder

Question 15

What is a chorion?

Answer 15

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)

Question 16

What is used to detect pregnancy in home tests?

Answer 16

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

Question 17

What is HCG?

Answer 17

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

Question 18

What is the decider basalis?

Answer 18

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

Question 19

When is HCG released from the chorion?

Answer 19

first 12 weeks of pregnancy, then the placenta starts secreting

Question 20

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

Answer 20

Amniotic cavity - above epiblast (nearer placenta)

Yolk sac - below hypoblast

Question 21

What is the function of the allantoic cavity?

Answer 21

Gas exchange and removal of liquid waste

Question 22

what are the 3 main functions of the placenta?

Answer 22

foetal nutrition
transport of waste and gases
immune protection

Question 23

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

Answer 23

Foetal - smooth

Maternal - rough, on decidua basalis

Question 24

When does the placenta become fully mature?

Answer 24

18-20 weeks

Question 25

What is gastrulation?

Answer 25

Formation of the germ layers

Question 26

What is neurulation?

Answer 26

Formation of neural tube

Question 27

Where is the primitive streak found?

Answer 27

Midline of epiblast by the dipping in of cells

Question 28

When is the axis of the embryo determined?

Answer 28

After formation of primitive streak: - head end = above epiblast - tail end = below hypoblast

Question 29

What forms the 3 germ layers?

Answer 29

Migration of epiblast cells which displace hypoblast cells, forms trilaminar disc

Question 30

What are the 3 germ layers?

Answer 30

Ectoderm - hair, nails, epidermis Mesoderm - muscle, bone, connective tissue, fat Endoderm - internal organs e.g. lungs

Question 31

What forms the notochord?

Answer 31

Migration of cells from primitive streak into midline, which encourages the formation of the neural tube from the ectoderm

Question 32

Describe neurulation

Answer 32

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

Question 33

What effect does the neural tube have on the mesoderm?

Answer 33

Stimulates mesoderm to thicken, and separate into 3 parts: - paraxial mesoderm (closest to tube) - intermediate mesoderm - lateral plate mesoderm

Question 34

What does the lateral plate mesoderm split into?

Answer 34

Somatic and splanchnic mesoderm, which forms the body cavity and coverings

Question 35

What does the intermediate mesoderm become later on?

Answer 35

Urogenital system (kidneys and reproductive tract)

Question 36

What does the paraxial mesoderm split into?

Answer 36

Somites, which each splits into: - dermatome: dermis - myotome: skeletal muscle - sclerotome: bones - syndetome: cartilage and tendons

Question 37

How many pairs of somites are there?

Answer 37

43 pairs

Question 38

When does the heart start to beat?

Answer 38

24 days

Question 39

What is the cavity between the somatic and splanchnic mesoderm of the lateral plate mesoderm?

Answer 39

Intraembryonic coelom

Question 40

Describe the teratogenic effects of thalidomide

Answer 40

Phocomelia

Question 41

Which enantiomer of thalidomide is harmful?

Answer 41

S-enantiomer

Question 42

List some environmental teratogens

Answer 42

Drugs Alcohol/tobacco Infectious agents e.g. rubella Other: radiation

Question 43

When during pregnancy are teratogens most likely to kill foetus?

Answer 43

week 1-2

Question 44

When during pregnancy are teratogens likely to cause great damage to organs/systems?

Answer 44

week 3-8

Question 45

What does the risk imposed by a teratogen depend on?

Answer 45

Time of exposure Dose Genetic susceptibility

Question 46

When does the respiratory system start to form?

Answer 46

4th week, respiratory diverticulum appears on day 26

Question 47

What does the respiratory primordial (lung bud) grow from?

Answer 47

Ventral wall of foregut, median outgrowth called the laryngotracheal groove (diverticulum)

Question 48

What forms between the growing oesophagus and trachea, before completely separating them?

Answer 48

Oesophagotracheal septum

Question 49

What results from the incomplete separation of the trachea and oesophagus?

Answer 49

Tracheoesophageal fistula and atresia of the oesophagus

Question 50

What is atresia?

Answer 50

When an orifice or passage in the body is abnormally closed or absent

Question 51

What forms the visceral lung pleura?

Answer 51

Splanchnic mesoderm

Question 52

What forms the parietal lung pleura?

Answer 52

Somatic mesoderm

Question 53

What are the 3 main stages in lung differentiation?

Answer 53

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

Question 54

When do vascular connections and pneumocyte cell types develop?

Answer 54

foetal period

Question 55

When is the alveolar stage of foetal lung development?

Answer 55

32 weeks - 8 years old

Question 56

When is the canalicular stage of foetal lung development?

Answer 56

17-27 weeks

Question 57

When is the saccular stage of foetal lung development?

Answer 57

27-40 weeks

Question 58

What are some congenital lung conditions?

Answer 58

ARDS Accessory lobes Agenesis of the lung Azygos lobe

Question 59

What 4 embryonic components make up the diaphragm?

Answer 59

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

Question 60

Which somites is the septum transverse found alongside?

Answer 60

C3-C5 (phrenic nerves)

Question 61

What are the 3 main congenital abnormalities of the diaphragm?

Answer 61

Failure of complete closure Herniation Pulmonary hypoplasia

Question 62

What are the 3 types of congenital hernia?

Answer 62

Posterolateral (Bochdalek) Anterior (Morgagni) Central

Question 63

What type of hernia is not congenital?

Answer 63

Hiatal hernia

Question 64

What are the three main sites of hiatal hernia?

Answer 64

Descending aorta T12 Oesophagus T10 Vena cava T8

Question 65

What are the two types of oesophageal hernia?

Answer 65

``` Sliding hiatus hernia - slides out Paraesophageal hernia ("rolling") - rolls out ```