Embryology And Fertilisation

Question 1

Why is semen alkaline?

Answer 1

Neutralises acidic vaginal fluid

Question 2

Approx how many sperm are left by the infundibulum?

Answer 2

1000

Question 3

What kills off the sperm

Answer 3

Stuck in vaginal mucus
Lost in cervix
Absorbed by white blood cells
(Contraception)

Question 4

Why do sperm rub against the tube walls

Answer 4

Removal of the glycoprotein coat of the acrosome.
Called capacitation

Question 5

What is the acrosome

Answer 5

Cap like structure around sperms nucleus

Question 6

What does the sperm secrete after capacitation

Answer 6

Hyaluronidase

Question 7

What does hyaluronidase do

Answer 7

Breaks down hyaluronic acid (such as the layer that protects the egg)

Question 8

What is the Corona radiata

Answer 8

Layer of follicular cells around the egg

Question 9

What is the zona pellucida

Answer 9

Extracellular matrix of glycoproteins

Question 10

What are the stages of the acrosomal reaction

Answer 10

1. Release of acrosin from the sperm
2. Creation of actin anchors from the sperm that anchors and binds ZP3 proteins.leading to fusion of sperm and egg plasma layers - SPERM BINDING

Question 11

What is the cortical reaction

Answer 11

Rise in internal egg calcium leads to fusion of granules with the egg cell membrane

Question 12

What does the cortical reaction create

Answer 12

The hyaline layer

Question 13

What does the hyaline layer do

Answer 13

Prevents more than one sperm from fertilising the egg

Question 14

What happens inside the egg while the hyaline layer is being created

Answer 14

Meiosis II - creation of the 23 chromosome female pronucleus

Question 15

What happens to the male and female pro nucleii

Answer 15

Dissolve the nucleus envelope and mitotic spindle weaves the chromosomes into complimentary pairs

Question 16

What is the moment the zygote is formed called

Answer 16

Syngamy (single cell!)

Question 17

Name the two outer layers of the egg

Answer 17

Corona radiata and zona pellucida

Question 18

Where is the most likely place for fertilisation to take place?

Answer 18

Ampullary region of the fallopian tube

Question 19

How many hours after fertilization has the zygote hit the 4 cell stage

Answer 19

40 hours

Question 20

How many hours after fertilization has a zygote hit two cells

Answer 20

30 hours

Question 21

What process in the zygote separates inner cells from outer cells in the blastocyte?

Answer 21

Compaction

Question 22

What is the mullerian duct system responsible for the development of?

Answer 22

Uterus, cervix and upper two thirds of the vagina

Question 23

What is a 16 cell blastocyst called

Answer 23

Morula (mulberry shaped)

Question 24

What is the outside layer of the blastocyst called

Answer 24

Trophoblast

Question 25

Embryoblast become what

Answer 25

Fetus

Question 26

What cells invade the uterine wall at implantation

Answer 26

Syncytiotrophoblast

Question 27

How many cells has a zygote at 3 days after fertilization

Answer 27

12-16

Question 28

What structure secretes hCG in early pregnancy

Answer 28

Syncytiotrophoblast

Question 29

A failure of cortication results in what?

Answer 29

Polyspermia

Question 30

On day 8 what layer does the blastocyst attach to?

Answer 30

Decidua basalis

Question 31

Name the segments of the trophoblast

Answer 31

Cytotrophoblast (mono nucleus) Syncytiotrophoblast (many nucleii)

Question 32

Explain the decidual reaction

Answer 32

High progesterone enlarges decidual cells and coats them in a sugar rich, fatty fluid. Initially only occurs at decidua basalis, but eventually spreads throughout all of the decidua

Question 33

What develops around day 14 outside the blastocyte

Answer 33

Primary villi start to grow, forming lacunae (empty spaces) and encouraging growth of blood vessels into the lacunae (this eventually creates a large pool of blood, the junctional zone)

Question 34

What happens around day 14 inside the blastocyst

Answer 34

Formation of the bilaminar embryonic disc

Question 35

What is found within the yolk sac

Answer 35

Vitelline fluid

Question 36

What cells line the outside of the yolk sac

Answer 36

Hypoblasts

Question 37

What is the initial stages of the embryos germ layers?

Answer 37

Epiblast

Question 38

What lines the amniotic cavity

Answer 38

Epiblast cells

Question 39

What do extraembryonic mesoderm cells do

Answer 39

Line the outside of the cytotrophoblast and create space for the chorionic cavity

Question 40

What does the embryoblast become

Answer 40

Epiblast and hypoblast

Question 41

In what direction does the primitive groove form

Answer 41

Caudal to cranial

Question 42

What makes up the primitive streak

Answer 42

Primitive groove Primitive pit Primitive node

Question 43

Name the layers of the trilaminar disc

Answer 43

Endoderm Mesoderm Extoderm

Question 44

What are the two bilaminar areas in the trilaminar membrane

Answer 44

Oropharyngeal membrane (mouth) Cloacal membrane (anus and genitourinary tracts)

Question 45

What does the notochord do

Answer 45

Transient solid rod Influences embryo folding Secretes sonic hedgehog (diffuses out and allows cells to know where they are in 3 dimensional space

Question 46

What does the mesoderm differentiate into on day 20

Answer 46

Paraxial, intermediate, lateral

Question 47

Explain neurulation

Answer 47

Neural plate - neural groove (with neural folds) - neural tube (between mesoderm and ectoderm)

Question 48

What happens in the junctionional zone at the end of week 3?

Answer 48

Secondary villi grow into the primary villi, creating the fetal contribution to the placenta and the villous capillary system

Question 49

What does gastrulation do

Answer 49

Gives the embryo it's specific head to tail and front to back orientation

Question 50

What is the movement of epiblast cells towards the primitive streak called

Answer 50

Invagination

Question 51

What are the trophoblastic primary villi composed of

Answer 51

Cytotrophoblastic core covered by syncytiotrophoblast

Question 52

What is the first step of gastrulation

Answer 52

Formation of the primitive streak

Question 53

What is the source of germ layers during gastrulation

Answer 53

Epiblast

Question 54

What does the exocoeleomic membrane derived from

Answer 54

Hypoblasts

Question 55

How long does spermatogenesis take

Answer 55

74+4 days

Question 56

Where does the diaphragm originate from

Answer 56

Septum transversum of the fourth pharyngeal arch

Question 57

What is the origin of the renal tubules

Answer 57

Metanephric blastema

Question 58

What stimulates the mesonephric ducts

Answer 58

Androgens

Question 59

What stimulates the paramesonephric ducts

Answer 59

Oestrogen

Question 60

What causes regression of the paramesonephric ducts

Answer 60

Mullerian inhibiting substance

Question 61

What do the paramesonephric ducts become in men

Answer 61

Appendix testes

Question 62

What does the wolffian ducts become in females

Answer 62

Atrophy to Gartner's duct, suspensory ligaments of the ovary

Question 63

What does the ectoderm become?

Answer 63

EXOSKELETON - skin, eye lens, external auditory meatus, adrenal medulla, nerve systems, appendages

Question 64

What does the mesoderm become

Answer 64

SKELE and MUSCLES dermis, urogenital ( kidney, repro), bone, muscle, vascular, lymph and spleen, adrenal cortex

Question 65

what does endoderm become

Answer 65

INNER = ORGANS eustachion tube, middle ear, GI tract, liver, endocrine bits, resp system, bladder

Question 66

What is the notochord from

Answer 66

mesoderm

Question 67

what does lateral mesoderm become

Answer 67

skeletal limbs

Question 68

what does intermediate mesoderm become

Answer 68

urogenital system

Question 69

what does paraxial mesoderm become

Answer 69

axial skeleton (somites become vertebral colum)

Question 70

what does the neural crest (ectoderm) become

Answer 70

cranial bones

Question 71

What are the parts of the pharangeal apparatus

Answer 71

Arches (mesoderm) Pouches (endoderm) clefts (ectoderm)

Question 72

Pharangeal arch 1 =

Answer 72

CN V (trigeminal) - muscles of mastication

Question 73

Pharangeal arch 2 =

Answer 73

CN IIV (facial) - muscles of facial expression

Question 74

pharangeal arch 3 =

Answer 74

CN IX (glossopharangeal) - swallowing (stylopharangeus) + hyhoid bone

Question 75

pharangeal arch 4 + 6=

Answer 75

CN X - Vagus nerve, (voice box,) larynx musces, some swallow`

Question 76

pharangeal pouch 1 =

Answer 76

eustachion tube

Question 77

Pharangeal pouch 2

Answer 77

palentine tonsil

Question 78

pharangeal pouch 3

Answer 78

inferior parathyroid + thymus

Question 79

pharangeal pouch 4 + 6

Answer 79

superior parathyroid, ultimobranchial body

Question 80

Pharangeal arch 1

Answer 80

maxillary arches

Question 81

Pharangeal arch 2

Answer 81

regresses

Question 82

pharangeal arch 3

Answer 82

internal and common carotids

Question 83

pharangeal arch 4

Answer 83

L = aorta arch R = subclavian

Question 84

Pharangeal arch 6

Answer 84

pulmonary arteries, L forms ductus arteriosus

Question 85

when does fetal heart start beating

Answer 85

day 22

Question 86

What is the allantois

Answer 86

connects yolk sac to hind-gut (endoderm). becomes median umbilical ligament.

Question 87

what produces HCG

Answer 87

syncytotrophoblast

Question 88

which fetal cells connect to maternal cells/blood

Answer 88

syncytotrophoblast

Question 89

What is another word for paraxial mesoderm

Answer 89

Splanchnic mesoderm

Question 90

What is another name for parietal mesoderm

Answer 90

Visceral mesoderm

Question 91

When does the neural tube close

Answer 91

Day 25 head end day 28 tail end

Question 92

What forms the somites

Answer 92

Paraxial mesoderm

Question 93

What connects the yolk sac to the midgut

Answer 93

Vitteline duc

Question 94

Where is the mesentery from

Answer 94

Mesoderm

Question 95

What does the septum transversum become when it meets the pleuroperitoneal fold?

Answer 95

Diaphragm

Question 96

What happens if there is a failure of the septum transversum and ventral pleuroperitoneal fold to meet

Answer 96

Congenital diaphragmatic hernia

Question 97

What does the buccopharangeal membrane break down to become

Answer 97

Stomodeum

Question 98

Where does the respiratory diverticulum form from

Answer 98

The endoderm of the foregut

Question 99

Where do the ventral and dorsal pancreatic buds form

Answer 99

The fore gut endoderm

Question 100

What grows down to divide the cloaca

Answer 100

Urogenital septum

Question 101

When does the superior mesenteric artery form?

Answer 101

Week 5

Question 102

Where does the gut go as it forms?

Answer 102

Between weeks 6 + 10 lengthen and twist out into the umbilical cord. Then from week 10 return. If not, omphalos.

Question 103

What happens if the vitiline duct doesn't disappear?

Answer 103

Meckel's diverticulum

Question 104

Where is Meckel's diverticulum

Answer 104

50cm back from ceacum, on the illeum.

Question 105

What is liver made of

Answer 105

Mix of mesoderm and endoderm. Most of billiary tree is endoderm Special fetal blood making cells are mesoderm

Question 106

What does the liver divide the ventral mesogastrium into

Answer 106

Falciform ligament, + lesser omentum

Question 107

What does the dorsal mesogastrium become

Answer 107

Greater omentum (4x mesoderm layers)

Question 108

What makes up the muscles and cartilage of the chest wall

Answer 108

Splanchnic mesoderm

Question 109

What cavity do lungs grow into

Answer 109

Intraembryonic cavity