Year 3 - Reproduction > Embryology > Flashcards

Embryology Flashcards

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1
Q

What occurs during Week 3?

A

1) Gastrulation
2) Neurulation
3) Somite formation

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2
Q

What occurs between weeks 4-8?

A

Organogenetic period

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3
Q

What occurs week 9 onwards?

A

Organ maturation

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4
Q

What does the cloaca divide to form?

A

> The GI tract

> Anteriorly the urogenital sinus

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5
Q

What does the mesonephric duct drain into?

A

The urogenital sinus

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6
Q

What does the urogenital sinus form?

A

> Urinary bladder

> The caudal end forms the urethra

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7
Q

Types of kidney in week 5 embryo?

A

> Pronephros

> Mesonephros

> Metanephros (Uteric bud and metanephric mesoderm)

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8
Q

Where is the pronephros?

A

The cervical region

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9
Q

Where is the mesonephros?

A

The thoracolumbar region

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10
Q

Where is the metanephros?

A

Pelvic region

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11
Q

When does the genital (gonadal) ridge formation occur?

A

Week 5-6

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12
Q

What does the genital (gondola) ridge form from?

A

The mesonephros forms a long ovoid structure in association with thoracic and upper lumbar vertebrae.

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13
Q

Where do the germ cells migrate from?

A

From the yolk sac, via dorsal mesentery, and embed into primitive sex cords

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14
Q

If germ cells do not migrate what will occur?

A

No gonads

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15
Q

Epithelium of the mesonephros invaginate to form what? What does this become?

A

A tube, this tube becomes the para-mesonephric duct

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16
Q

What does the mesonephric duct (The Wolffian duct) develop into, in a male?

A

Mesonephric duct develops into epididymis, vas deferens, seminal vesicle

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17
Q

What does the paramesonephric duct (The Mullerian duct) develop into in males?

A

Paramesonephric duct degenerates

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18
Q

What does the urogenital sinus form in males?

A

Urogenital sinus forms bladder, urethra; and prostate

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19
Q

What is another name for the mesonephric duct?

A

The Wolffian duct

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20
Q

What is another name for the paramesonephric duct?

A

The Mullerian duct

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21
Q

What does the mesonephric duct (The Wolffian duct) develop into, in a female?

A

Mesonephric duct degenerates

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22
Q

What does the paramesonephric duct (The Mullerian duct) develop into in females?

A

Paramesonephric duct forms fallopian tube, uterus, cervix part of vagina

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23
Q

What does the urogenital sinus form in females?

A

Urogenital sinus forms bladder and lower part of vagina

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24
Q

How does the indifferent gonad know whether to develop into a testes or an ovary?

A

SRY encodes for a protein called TDF (testis determining factor)

TDF makes the indifferent gonad develop into a testis

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25
Other than allowing the development of the testes what does SRY encode for?
Sertoli cells
26
What is the role of the Sertoli cells (male)?
Sertoli cells recreate Mullerian inhibiting substance (MIS): 1) Paramesonephric duct degenerates. Therefore no development of fallopian tube, uterus, cervix part of vagina. 2) MIS transforms mesenchymal cells between cords to form Leydig cells --> Testosterone --> External genitalia
27
What is the role of the Leydig cells?
By 8 weeks gestation, Leydig cells produce testosterone which stimulate the differentiation of male external genital development and mesonephric ducts
28
Where do the seminal vesicles (male) develop from?
Outgrowth from caudal end of mesonephric duct
29
Where does the prostate develop from?
Outgrowth(s) from urethra, from urogenital sinus
30
Why does a female not develop testes?
They do not have the SRY of TDF regions
31
How many follicle at birth?
Around 2 million primordial follicles
32
After puberty, hormonal influences stimulation of how many follicles per month?
12-15 follicles per 28 day cycle Only one follicle (normally) reaches maturity and ovulation
33
In females, what does the absence of testosterone lead to?
Degeneration of mesonephros and mesonephric duct The paramesonephric ducts develop to give rise to female genital tract
34
What does the cranial end of paramesonephric duct become in females?
The ovaries
35
What does the caudal end of paramesonephric duct become in females?
Become uterus and superior part of the vagina
36
What does the inferior part of the vagina develop from?
The urogenital sinus
37
Where do the gonads initially form?
Within the lumber region
38
At week 7 where are the gonads/testes located?
Level of T10
39
At week 7 where are the gonads/ovaries located?
Level of T10
40
At week 12 where are the gonads/ovaries located?
Broad ligament
41
At week 12 where are the gonads/testes located?
Level of deep inguinal ring (remains until 7th month)
42
When do the testes enter the scrotum?
Just prior to birth 39 weeks
43
What happens to the gonads/ovaries before birth?
Round ligament drawn through inguinal canal to attach to labrum majorum
44
For the descent of the gonads in males what needs to be present?
The formation of the larger inguinal canal in males
45
For the descent of the gonads in females what needs to be present?
In the female – the presence of the round ligament and its passage through the inguinal canal
46
What is cryptorchidism?
Absence of testes in scrotum (cryptorchidism)
47
Types of cryptorchidism?
1) Undescended 2) Ectopic 3) Retractile testes 4) Absent testes
48
Complications of cryptorchidism?
1) Infertility 2) Malignant transformation (Germ cell tumours) 3) Testicular torsion
49
How is cryptorchidism managed?
Orchiopexy
50
In Cryptorchidism where can the testes be located?
1) Abdomen 2) Inguinal canal 3) Internal inguinal ring 4) External inguinal ring 5) Prescrotal (prepubic) region
51
Remnants of the mesonephric duct - cranial excretory tubule in the mesovarium?
Epoophoron
52
Remnants of the mesonephric duct - caudal excretory tubule in the mesovarium?
Paroophoron
53
Remnants of the mesonephric duct - small caudal portion in the wall of the uterus of vagina?
Gartner's cyst
54
Types of anomalies of the female reproductive tract?
1) Complete duplication 2) Separate uterus 3) Bicornuate uterus (Partially separated, deep) 4) Arcuate uterus (Partially separated, shallow)
55
What is the ratio of babies being born with birth defects?
1 in 46 babies (2.2% of babies)
56
Within England and Wales which birth defect has a higher incidence than other European countries?
Spina bifida - 1 in 1000 babies
57
What are the most common birth anomalies?
Congenital heart defects > 1 in 1000 babies > Can require major surgery > 6% babies will die before their 1st birthday
58
What is a teratogen?
1) A class of drug used for inflammatory conditions 2) Drug or other substance which can result in birth defect 3) Fetal anomaly associated with short or absent limbs 4) A congential ovarian cyst which can contain any type human tissue
59
What can a teratogen lead to?
May lead to structural or functional abnormality or even in utero death: 1) Death 2) Learning difficulties 3) Sensory deficient 4) Structural abnormalities 5) Cancer 6) IUGR or growth defects 7) Neurodevelopmental / behavioural dysfunction 8) Developmental delay
60
Teratogens within the 1st trimester?
> Structural defects when organogenesis is occurring | > Greatest risk between week 3 and 11.
61
When exposed to teratogens after which week are functional or growth defects more likely to occur?
After 12 weeks of gestation
62
What increases the risk of Fetal Alcohol syndrome?
Binge drinking = When an individual drinks five or more units of alcohol on one occasion Regular binge drinking, around conception and in early pregnancy, is particularly harmful.
63
What is the classic triad for congenital rubella syndrome?
1) Sensorineural deafness 2) Eye abnormalities—especially retinopathy, cataract and microphthalmia 3) Congenital heart disease—especially pulmonary artery stenosis and patent ductus arteriosus.
64
What does Varicella lead to?
> Limb hypoplasia > Skin scarring > Eye defects
65
In which trimester does Varicella pose the highest risk?
Greatest risk 2nd trimester
66
When do cardiac defects occur during pregnancy?
Very early in pregnancy
67
What does warfarin use in pregnancy increase the risk of?
Cardiac defects
68
What can cause cardiac defects?
> Drugs e.g. Warfarin > Infections > Genetic
69
Who requires preconception counselling to reduce risk of anomalies?
``` > Epilepsy > Diabetes > Woman on anticoagulants > Woman with congenital anomalies > Antihypertensives ```
70
Why do we advise folic acid use?
To reduce the risk of a neural tube defect
Year 3 - Reproduction
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