Flashcards in Reproductive Embryology Deck (51)
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1
Give a brief summary of development from 1-9 weeks
Week 1 and 2 - implantation and cell proliferation
Week 3 - gastrulation, neuralation and somite formation
Week 4-8 - organogenesis
Week 9 onwards - maturation of organ systems
2
How is reproductive organogenesis different fro normal embryology?
It extends beyond 8 weeks and even the post-natal period
3
Urinary recap:
What three sets of kidneys form during foetal development?
Pronephros
Mesonephros
Metanephros
4
Urinary recap:
Describe the location of each sets of kidneys and their functionality during development
Pronephros - cervical region - vestigial (not functional)
Mesonephros - thoracic-lumbar region - briefly functional
Metanephros - pelvic region (functional)
5
Urinary recap:
What is the predecessor structure to the metanephros?
Ureteric bud
6
What is the cloaca?
The terminal part of the foetal gut tube
7
The cloaca divides to outline what two cavities
Anteriorly: urogenital sinus
Posteriorly: rectum
8
Where does the cloaca drain?
Maternal systemic circulation
9
What duct drains into the urogenital sinus?
Mesonephric duct
10
What week does genital development begin?
5th-6th
11
What happens to the mesonephros to kick off genital development?
Long ovoid structure (mesonephric ridge develops) - the medial part of this becomes thickened into the genital/gonadal ridge
12
Describe the epithelium of the gonadal ridge; what structure does it form
Formed from intermediate mesoderm and forms the primary sex cords
13
What type of cells migrate into genital ridge to form the indifferent gonad?
Germ cells from the yolk sac (itself formed from outer lining of the blastocyst and therefore undifferentiated)
14
The epithelium of what structure invaginate to form a tube?
Mesonephros
15
What structure is formed from the invagination of the mesonephric duct?
Paramesonephric duct
16
What are the alternative names for the paramesonephric and mesonephric ducts?
PMN duct = Mullerian duct
MN duct = Wolffian duct
17
The PMN duct develops on what side of the gonads/MN duct
Lateral
18
The funnel shaped cranial end of the PMN duct opens into what cavity?
Peritoneal cavity
19
The PMN duct crosses the MN duct on what side and drains into the dorsal wall of what cavity?
Ventrally crosses the MN ducts and projects into the urogenital sinus
20
In males the gonads form what?
Testes
21
In males, what are the fates of the MN duct, PMN ducts and urogenital sinus
MN duct - epididymus, vas deferens and seminal vesicles
PMN duct - degenerates
Urogenital sinus - bladder, urethra and prostate
22
In females what do the gonads form?
Ovaries
23
In famles, what are the fates of the MN duct, PMN duct and the urogenital sinus?
MN duct - degenerates
PMN duct - fallopian tubes, uterus, cervix
Urogenital sinus - bladder and lower vagina
24
OSPE help:
If there is a pin in the interstitium of the testes, what is the answer?
Leydig cells (testosterone producing)
25
How does the indifferent gonad know to develop into testes?
Y chromosome SRY codes for TDF (testis determining factor)
26
What other sex determining functions does SRY code for?
Primordial supporting cells express SRY
Transforms them into Sertoli cells
S cells secrete MIS (Mullerian-inhibiting-substance) - further develops male genitalia
27
What are the functions of MIS?
Cause PMN duct to degenerate and transforms mesenchymal cells between sex cords into Leydig cells
28
What gestational week are gonads differentiated in the male foetus?
7th week
29
What is the action of TDF?
Stimulates primary sex cords which extend into the medulla and form seminiferous tubules branching into the rete testes
30
What are the rete testes?
The rete testis is an anastomosing network of delicate tubules located in the hilum of the testicle
31
Describe the change of epithelium in the developing testis
Surface epithelium (mesothelium) is lost when thick capsule forms (tunica albuginea)
32
What are the three male sex glands?
Seminal vesicles, prostate, external male genitalia
33
How are seminal vesicles formed?
Outgrowth from caudal end of the MN duct
34
How is the prostate formed?
Outgrowths from urethra from urogenital sinus
35
What substance causes the external male genitalia to be developed?
Formed under the influence of testosterone
36
How does female gonadal development differential from male development?
No Y chromosome, no SRY region therefore no TDF and gonads develop into ovaries
37
What are the two distinct phases of development of the ovaries?
Pre-natal and Pubertal
38
Outline the pre-natal ovaries development
Primary sex cords degenerate and primary germ cells remain
Secondary sex cords develop and are incorporated around the germ cells
Meiosis is arrested and waits for puberty
39
Approx how many follicles is a woman born with?
Approx. 2 million
40
What is the fate of many of a woman follicles before puberty?
Many become atretic
41
After puberty, what happens to these follicles?
Hormonal influences causes maturation of 12-15 of these follicles per 28 day cycle
42
How many of the stimulated follicles are ovulated?
One (normally)
43
Outline the development of the tubular components to the female reproductive system
Absence of testosterone causes degeneration fo MN and MN duct
PMN duct develop into female genital tract
44
What is the fate of the cranial end of the PMN duct?
Open funnel end becomes associated with the ovary
45
What is the fate of the caudal end of the PMN duct?
Otherwise known as the uterovaginal primoridium, becomes the uterus and superior part of the vagina
46
Outline the descent of the testes
Week 7 - T10 (diaphragm undescended)
Week 12 - level of deep inguinal ring (remains until 7th month)
Enters scrotum just prior to birth (39 weeks)
47
Outline the descent of the ovaries
Week 7 - T10
Week 12 - Broad ligament forms
Round ligament drawn through inguinal canal to attach to the labrum majorum
48
What is cryptorchidism?
Absence of testis in the scrotum
49
What are the causes of cryptorchidism?
1. Undescended
2. Ectopic
3. Retractile testes
4. Absent testes
50
What are the complications of cryptorchidism?
1. Infertility
2. Malignant transformation (germ cell tumours)
3. Testicular torsion
51
