S3 L1 Development of the Reproductive Tracts Flashcards
Recap of the process of: fertilisation to blastocyst
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Recap: Stages of development before birth
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Recap: Gastrulation and folding
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Recap: Three key layers lead to the structures and symptoms of the body
- State the three layers and their ‘sub-layers’, state what’s included in their sub-layers
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Development of the uro-genital and GI tracts
- this is all linked
- GI: 3 sections of the primitive gut tube, the most caudal section develops the c_____, this becomes the u_________ ______
Don’t look at this Q picture until read answer side of card
cloaca (common opening, responsible for the anal and urogenital openings)
This becomes the urogenital sinus (common opening for the reproductive and urinary systems)
Overview:
How do we make a reproductive system?
- What is the chromosomal sex determined by?
- When do you start seeing differences between M and F?
- What is the period of genital development called before the sexes have a different development?
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What’s the key trigger in sexual dimorphism (i.e. become M and F)
- think about a particular protein…
- What happens to this protein…
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Recognise the similarities and differences between the two systems (M and F)
1a. First initial step: Same in M and F
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1b. Primordial germ cells
- Carry which genes?
- Where do they move from and too?
- What does this occur?
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- Development of the gonad
- three sources
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- Development of primitive sex cords
- How do these develop?
(still at the indifferent stage)
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Males - have a Mesonephric duct
Females - have a paramesonephric duct
Summary:
- Male and females
- How it goes from indifferent gonad, specific M and F
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- Next step of what happens in the male
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- Next step of what happens in the female
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Comparison of male and female gonad development
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Summary: Molecular and hormonal drivers of gonad differentiation
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- *The Internal genitalia - indifferent stage a pair of ducts**
- Two types of ducts
- *Summary of male: Development of the internal reproductive ducts**
- Male, include: Hormone produced, ducts,…
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Male: The fate of the ducts
- what does this fate depend on?
- two hormones produced, and what does this mean?
Mesonephric duct development:
- What is this first?
- Drains into what…?
- The structure mentioned in the second point, becomes what…?
Final step for the mesonephric duct:
- Mesonephric duct is maintained by…
- Converted into….
- Where does it go?
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- *Summary of female: Development of the internal reproductive ducts**
- Female, include: Hormone produced, ducts,…
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Female: The fate of the ducts
- what does this fate depend on?
- two hormones produced, and what does this mean?
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Paramesonephric duct development
- more detail above the caudal and cranial end of the duct
- diagram showing what happens to develop the ‘canal’ and opening
Summary of the development of the ductal systems
•Mesonephric duct functions in both male and female embryos as duct of
embryonic kidney
•Paramesonephric (Mullerian) ducts appear in both
•Mesonephric duct ceases to be of use to the urinary system and will
degenerate unless testis-derived testosterone is present
•Paramesonephric duct regresses in the presence of testis-derived MIH
- *External genitalia:**
- indifferent stage…
- basic components
External genitalia - Male
- What happens in males to these ‘basic components’
- Influenced by which hormone?
External genitalia - Female
- What happens to the ‘basic components’
Comparative external structures of M and F
(Recap)
Descent of the gonad - testes
Descent of the gonad - ovary
- How does the ovary descend?
- What prevents further descent?
(look at last week - much more indepth notes)
Summary: Deveopment of the reproductive tract mind map, include -
- Gonad
- the 2 hormones and then what this means for each gonad (4 sections)
Turner’s syndrome:
- genotype
- what does this lead too? including signs and symptoms
In females, the absence of one X chromosome in Turner’s syndrome (45X0)
will lead to degeneration of the ovaries.
– This is an example of gonadal dysgenesis, oocytes are absent, and the
ovaries appear as streak gonads. Individuals are phenotypically female but may
have a variety of chromosomal complements, including XY.
– Patients with Turner syndrome also have gonadal dysgenesis. They have a
45,X karyotype and short stature, high-arched palate, webbed neck, shield-like
chest, cardiac and renal anomalies, and inverted nipples
Klinefelter syndrome
- Genotype
- What does this lead to?
–Klinefelter syndrome, with a karyotype of 47,XXY (or other variants, e.g.,
XXXY), is the most common sex chromosome disorder, occurring with a
frequency of 1 per 1000 males. Patients may have decreased fertility, small
testes, and decreased testosterone levels. Gynecomastia (enlarged breasts) are
present in approximately 33% of affected individuals.
Congenital adrenal hyperplasia:
- Genotype
- What happens? cause
Individuals with 46,XX (Disorders of Sexual Development) are females that have been
exposed to excessive amounts of androgenic compounds that masculinize the external
genitalia causing them to be ambiguous.
•Congenital adrenal hyperplasia (CAH) is the most common cause of ambiguous
genitalia
•Individuals are genetically female (46,XX), but excessive androstenedione produced by the adrenal glands results in masculinization of the external genitalia.
1. 21-hydroxylase enzyme deficiency, inherited as an autosomal recessive trait that results in a mineralocorticoid deficiency and an increase in androgenic compounds.
2. deficiency of 11-β-hydroxylase that causes similar biochemical effects and, therefore, similar effects on the external genitalia (as above)
3. deficiency of 17-α-hydroxylase that results in a decrease in prenatal and pubertal sex steroids. Females have normal internal and external anatomy, but at puberty, neither the adrenal glands nor the ovaries produce sex steroids. Consequently, there is no breast development or growth of pubic hair.
Androgen insensitivity syndrome (AIS)
- 46 XY disorder
- Sexual ambiguity in males is often due to androgen insensitivity syndrome (AIS).
- In these individuals there is a lack of androgen receptors or failure of tissues to respond to receptor–dihydrotestosterone complexes. Consequently, androgens produced by the testes are ineffective in inducing differentiation of male genitalia. Because these patients have testes and MIS is present, the paramesonephric system is suppressed, and uterine tubes and uterus are absent.
Both mesonephric and paranephric side is affected
5-α-Reductase deficiency (5-ARD)
Causes ambiguous genitalia in males and is due to an inability to convert testosterone to dihydrotestosterone because of a lack of the reductase enzyme. Without dihydrotestosterone, external genitalia do not develop normally and may appear male but be underdeveloped with hypospadias, or they may appear to be female with clitoromegaly.
