Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Repro Phys > Sexual Differentiation And Disorders > Flashcards

Sexual Differentiation And Disorders Flashcards

1
Q

Mullerian duct

A

embryonic ducts developing into female internal internal genitalia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Wolffian duct

A

embryonic ducts developing into male internal internal genitalia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Sex determining region Y (SRY)

A

important transcription factor on Y chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Primordial germ cell

A

cells that develop into sperm or oocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Primitive sex cords

A

cells that develop into gonadal cells associated with germ cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Mesonephric cells

A

cells that develop into gonadal cells that produce androgens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

5-alpha reductase

A

enzyme involved in development of male external genitalia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Gonadal dysgenesis

A

sexual differentiation is incomplete, usually abnormal development of gonads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Sex reversal

A

phenotype does not match genotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Intersex

A

some components of both male and female or ambiguous genitalia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Sexual Determination

A

Genetically controlled process dependent on the ‘switch’ on the Y chromosome. Chromosomal determination of male or female. (Contiguous process and consists of several stages)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Sexual Differentiation (definition)

A

The process by which internal and external genitalia develop as male or female. (Contiguous process and consists of several stages)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Events in sex differentiation with foetal age

A 
Foetal age weeks
4 - Wolfian Duct development
4.5 - Genital ridge
5 - Primordial Germ Cell migration
6 - Mullerian Duct development
7 - Seminiferous tubules
8 - AMH made so Mullerian regress in male
8 - Leydig cells
9 - First signs of vagina
9 - First meiotic prophase in oogonia
10 - Begin masculinisation of external genitalia
10 - Prostatic buds
10 - Begin regression of Wolffian Duct in female
10 - Testis begins migration
12-14 - Penis developed
17 - First follicles
24 - Vagina developed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Gonadal Sex

A

SRY gene creates the testis.

Sex determining region Y (SRY) switches on briefly during 
embryo development (>week 7) to make the gonad into a 
testis.   In its absence an ovary is formed.

Testis develops cells that make 2 important hormones
which are anti-Mullerian hormone (AMH) and testosterone.

Products of the testis influence further gonadal and
phenotypic sexual development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Gonadal development

A

After fertilisation a pair of gonads develop which are BIPOTENTIAL.

Their precursor is derived from common somatic mesenchymal tissue precursors called the
genital ridge primordia (3½ - 4½ weeks) on posterior wall of lower thoracic lumbar region.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Genital ridge

A

3 waves of cells invade the genital ridge…
1. Primordial Germ Cells – become Sperm (male) or Oocytes (female).
2. Primitive Sex Cords – become Sertoli cells (male) or Granulosa cells
(female).
3. Mesonephric Cells – become blood vessels and Leydig cells (male) or
Theca cells (female).

17
Q

1 - Primordial Germ Cell Migration

A

An initially small cluster of cells in the epithelium of the yolk sac expands by mitosis at around 3 weeks.

They then migrate to the connective tissue of the hind gut, to the region of the developing kidney and on to the genital ridge – completed by 6 weeks.

18
Q

2 - Primitive sex cords (Sertoli/Granulosa)

A

Cells from the germinal epithelium that overlies the genital ridge mesenchyme migrate inwards as columns called the primitive sex cords.

Male
SRY expression
Penetrate medullary mesenchyme & surround primordial germ cells to form testis cords – precursor of seminiferous tubules.
Eventually become Sertoli Cells which express AMH.

Female
No SRY
Sex cords ill defined and do not penetrate deeply but instead condense in the cortex as small clusters around primordial germ cells – precursor of ovarian follicle
Eventually become Granulosa cells.

19
Q

3 – Mesonephric cells

A

These originate in the mesonephric primordium which are just lateral to the
genital ridges.

In males they act under the influence of pre-sertoli cells (which themselves
express SRY) to form…
• Vascular tissue
• Leydig cells (synthesize testosterone, do not express SRY)
• Basement membrane – contributing to formation of seminiferous
tubules and rete-testis

In females without the influence of SRY they form…
• Vascular tissue
• Theca cells

20
Q

Gonadal sex summary

A

Invading cells

Male
Primordial germ cells = Spermatozoa
Primitive sex cords = Sertoli cells (SRY, AMH)
Mesonephric cells = Leydig cells (Androgens)

Female
Primordial germ cells = Oocytes
Primitive sex cords = Granulosa cells
Mesonephric cells = Theca cells

21
Q

Internal Reproductive Organs

A

Mullerian ducts
• most important in female
• inhibited in the male by AMH

Wolffian ducts
• most important in the male stimulated by testosterone
• lack of stimulation by testosterone means regression in female

22
Q

Internal Sexual Differentiation

A 
gonad 
mesonephros 
mullerian duct 
wolffian duct
cloaca 
male =
epididymis
testis 
vas deferens
urinary bladder
seminal vesicle
prostate gland
female =
ovary 
oviduct
degenerating wolffian duct
uterus
urinary bladder
vagina
23
Q

5-α-reductase & External Differentiation

A

Testosterone is converted in the genital skin to the more potent androgen DHT
(dihydrotestosterone) by 5-a-reductase.

DHT binds to the testosterone receptor, but is more potent than testosterone .

DHT causes differentiation of the male external genitalia:• Clitoral area enlarges into penis
• Labia fuse and become ruggated to form scrotum
• Prostate forms

24
Q

External Differentiation

A

male and female picture

25
Q

Sex Differentiation Summary

A

undiff gonad

1) XY SRY- Testis
Sertoli cells: AMH - Regression of mullerian ducts
Leydig cells: Testosterone - Differentiation and growth
growth of Wolffian duct structures seminal vesicles and vas deferens.
Genital skin: Testosterone = DHT - Fusion of labial scrotal folds growth of phallus and prostate.

2) XX Ovary
Mullerian ducts differentiate
and grow into uterine tubes,
uterus and upper 1/3 of vagina.
Regression of Wolffian ducts due to lack of androgens.
Lack of androgen leads to vagina, labia & clitoris.

26
Q

Disorders of Sexual Differentiation

A

Gonadal dysgenesis - Sexual differentiation is incomplete. Usually missing SRY in male, or
partial or complete deletion of second X in female. Also used as a general description of
abnormal development of the gonads.

Sex reversal - Phenotype does not match genotype, ie may be male genotypically but
externally look like a female.

Intersex - Have some components of both tracts or have ambiguous genitalia. Sex of infant
difficult to determine.

Patients prefer to be known as someone with a ‘disorder of sexual differentiation’ or DSD.
Terms such as ‘pseudohermaphrodite’ and, ‘testicular feminisation’ are now obsolete.

27
Q

Gonadal dysgenesis - 1

A

What happens if in an XY individual…Testosterone is made but has no effect.

Androgen insensitivity syndrome (AIS)

Testes form and make AMH so Mullerian ducts regress.
No differentiation of Wolffian ducts
No external male genitalia

28
Q

Androgen insensitivity syndrome (AIS)

A

Complete AIS - incidence 1:20,000
Appear completely female at birth and assigned female gender despite being XY.
Have undescended testes.

Diagnosis?
Usually present with primary amenorrhoea. Lack of body hair is a clue.
Ultrasound scan and karyotype with male levels of androgens.
Never responded to androgen so appear and often feel female.

Partial AIS - incidence unknown as is probably a spectrum
Present with varying degrees of penile and scrotal development from ambiguous
genitalia to large clitoris.
Surgery was universal but now fortunately considered optional or at least best
delayed. Decisions made on potential. Very difficult for parents.

29
Q

Gonadal dysgenesis - 2

A

What happens if in an XY individual…Testosterone is made but not DHT?

5-α-reductase deficiency
Testes form and make AMH so Mullerian ducts regress.
Wolffian ducts develop
No external male genitals.

30
Q

5-α-reductase deficiency

A

Incidence varies enormously as autosomal recessive and can depend on inter-related
marriage.

Testes form, AMH acts, testosterone acts.
Internal structures form.
External structures do not develop.

May appear mainly female or may have ambiguous genitalia
The degree of the enzyme block varies and so therefore does the presentation.

What happens at puberty?
Need to assess potential as high testosterone level which will occur at adrenarche
and puberty may induce virilisation.

31
Q

Gonadal dysgenesis - 3

A

What happens if… 45 XO

Turner syndrome

32
Q

Turner syndrome

A

Turner syndrome: 1:3000

XO have failure of ovarian function.

‘Streak’ ovaries = ovarian dysgenesis - illustrates that we need 2 X’s for
ovarian development.

Uterus and tubes are present but small, other defects in growth and
development.

May be fertile…many have mosaicism.

Hormone support of bones and uterus

33
Q

Gonadal dysgenesis - 4

A

What happens if XX female is exposed to high levels of androgens
in utero?
Congenital adrenal hyperplasia

34
Q

Steroidogenesis
Adrenal Cortex
Pathway Block

A

diagrams

Failure to synthesise
cortisol has what
effect?

35
Q

Hypothalamic Pituitary Adrenal Axisj

A

Corticotropin releasing hormone
Stimulates pituitary to secrete ACTH.
Stimulates rapid uptake of cholesterol into the adrenal cortex.
Upregulates cholesterol side-chain cleavage enzyme (P450scc).
Increases glucocorticoid secretion.

Hypothalamus
CRH
Pituitary
ACTH
Adrenal glands
36
Q

Reduced Feedback

A

diagram

37
Q

Congenital adrenal hyperplasia (CAH)

A

No SRY so no testes and no AMH.
Mullerian ducts remain.
Masculinised external genitalia, but androgen levels not usually high enough to fully rescue Wolffian ducts.

Congenital adrenal hyperplasia: 1:15,000.

Completeness of the block varies.

If enzyme absent then children may be wrongly gender assigned at birth,
or may have ambiguous genitalia.

Also in CAH we need to be aware of possibility of ‘salt-wasting’ due to
lack of aldosterone, this can be lethal.

Often require treatment with glucocorticoids to correct feedback.

Repro Phys (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions