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Phase 2: Reproduction, Nephrology and Urology > Lecture 2: Development of the reproductive tract > Flashcards

Lecture 2: Development of the reproductive tract Flashcards

1
Q

The urinary and genital system is closely associatedly, particularly in males. Which part of the urogenital system is shared (urine and sperm both)?

A

Urethra

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2
Q

The urogenital tract originates from which embryological structure?

A

Intermediate mesoderm

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3
Q

In kidney development, there are three slightly overlapping kidney structures that are formed during development.

Name the three structures?

A

Pronephros

Mesonephros

Metanephros

(s before t)

**NOTE remember this development occurs on the other side of the embryo too (as there are two kidneys that develop)**

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4
Q

Describe the formation of the pronephros?

A
  • At the beginning of the 4th week of development, the pronephros is represented by 7-10 solid cell groups, thickened mesoderm.
  • These solid cell groups are located in the cervical region
  • By the end of the 4th week the pronephric system has regressed.
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5
Q

What is the functional capacity of the pronephros?

A

Rudimentary and nonfunctional

Regresses before more caudale kidney systems form

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6
Q

Where is the location of the pronephros?

A

Cervical region

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7
Q

Describe the formation of the mesonephros?

A
  • Derived from intermediate mesoderm from the upper thoracic to upper lumbar segments.
  • During the regression of the pronephric system (end of week 4), the first excretory tubules of the mesonephros appear.
  • Solid rod of mesoderm begins to form
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8
Q

The sequence of the formation of the kidney systems goes from which end to which end of the embryo?

A

Cranial to caudal

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9
Q

What is the functional capacity of the mesonephros?

A

Has the capacitiy to be functional for a short time during the early fetal period however regresses

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10
Q

The metonephros is known as the what?

A

Definitive kidney

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11
Q

What week does the metanephros appear?

A

Week 5 of development

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12
Q

How long does it take for the metanephros to become fully functioning kidneys

A

Takes 6 weeks

Overall, about week 11 of development

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13
Q

The metanephros is formed from which two structures?

A
  1. Ureteric bud
  2. Metanephric cap
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14
Q

The ureteric bud is an outgrowth of the?

A

Mesonephric duct

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15
Q

Name these kidney structures?

A
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16
Q

Name these parts of these embryological structures?

A
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17
Q

Define the cloaca?

A

Common chamber for the hindgut and urinary systems

Important in waste removal, including the kidneys

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18
Q

The ureteric bud is going to develop into which structure(s) of the permanent kidney?

A

The collecting system

Allows urine drainage from the developing kidneys

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19
Q

The metanephric cap is going to develop into which structure(s) of the permanent kidney?

A

Excretory units

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20
Q

Urine production begins for form when?

A

In early gestration

Remember the kidneys are fully formed by week 11/12

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21
Q

The anterior portion of the cloaca forms?

A

The urogenital sinus i.e. the bladder

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22
Q

The posterior portion of the cloaca forms?

A

The anus

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23
Q

What happens to the cloaca during the 4 to 7th week of development?

A

The cloaca divides into the urogenital sinus (anteriorly) and the anal canal (posteriorly).

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24
Q

What is the function of the urorectal spetum?

A

This is a layer of mesoderm between the anterior and posterior parts of the cloacal.

It divides cloaca (into anterior and posterior) by fusion with cloacal membrane

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25
Q

Name these parts that are a involved in the division of the cloaca?

A
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26
Q

What does the bladder form from?

A

The urogenital sinus and caudal parts of the mesonephric duct

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27
Q

What is the function of the allantois?

A

Not really functionally important in humans

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28
Q

Describe the process of the division of the cloaca?

A

The urorectal septum begins to form in the hindgut.

The septum grows forwards towards the cloacal membrane.

The urorectal septum and cloacal membrane will fuse creating two distinct openings of the cloaca.

Anterior: the opening to the bladder.

Posterior: the opening to the rectum

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29
Q

The bladder is formed from which embryological structure?

A

The cranial part of the urogenital sinus

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30
Q

When do the gonads acquire male or female morphological characteristics?

A

Week 7

Until this point males and females are indistinguishable

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31
Q

How is the Y chromocome the key sexyal dimorphism?

A

As it has a unique gene called SRY (sex-determing region on Y).

This gene encodes for a transcription factor that inititates a cascade of downstream genes that determine the fate of the rudimentary sexual organs

32
Q

If SRY gene is present, which sex will develop?

A

Male

SRY encodes the testis-determining factor

33
Q

If SRY gene is absent, which sex will develop?

A

Female

34
Q

In the indifferent stage of the gonad development. Which two ducts are formed around week 5-6?

A
  • The paramesonephric ducts
    • Also known as Mullerian duct
  • The mesonephric ducts
    • Also known as Wolffian duct
    • Lateral to the paramesoenphric duct
35
Q

Name these two ducts that are formed in the indifferent stage of gonad development?

A
36
Q

The Mullerian and Wolffian ducts are formed around Week 5-6, which are essential in the development of the gonads.

Which duct has an essential role in the development of the male reproductive system?

A

Mesonephric (Wolffian) ducts

37
Q

The Mullerian and Wolffian ducts are formed around Week 5-6, which are essential in the development of the gonads.

Which duct has an essential role in the development of the female reproductive system?

A

Paramesonephric (Mullerian) ducts

38
Q

What happens to the Wolffian ducts in females?

A

The mesonephric duct (aka the Wolffian ducts) almost completely disappear in females.

Leaves a few non-functional remnants

39
Q

What happens to the Mullerian ducts in males?

A

The paramesonephric (Mullerian) ducts degenerates in males under the influence of anti-mullerian hormone

40
Q

Which hormone causes the degeneration of the paramesonephric (Mullerian) ducts in males? and what produces it?

A

Anti-Mullerian hormone

Produced by the Sertoli cells in the testis

41
Q

What hormone drives the development of the mesonephric (Wolffian) ducts in males?

A

Testosterone

42
Q

What are the functions of the mesonephric (Wolffian) ducts?

A

In males only

Drains urine from the mesonephric kidney

Role in the formation of the male reproductive tract

43
Q

What are the functions of the paramesonephric (Mullerian) ducts?

A

In females only

Does not drain urine (remember only males have this spared duct (urine and sperm).

Role in the development of the female reproductive tract

44
Q

When the mesonephron regresses, what does the mesonephric duct (Wolffian) develop into?

A

The mesonephric duct forms the ductus deferens and ejaculatory duct under the infleunce of testosterone.

45
Q

What drives the regress of the mesonephric ducts in the females?

A

Absence of testosterone

46
Q

What drives the regress of the paramesonephric ducts in the males?

A

Anti-mullerian hormone

47
Q

What happens to the paramesonephric ducts (Mullerian) once they have developed?

A

They form funnel-shaped cranial ends which open up into the peritoneal cavity.

The Mullerian ducts migrate caudally (downwards) towards the pelvic region.

In the pelvic region, the mullerian ducts approach each other in the midline and fuse.

This forms the uterine tubes, uterus and superior vagina.

48
Q

The paramesonephic ducts (Mullerian) develop into which structures of the female reproductive tract?

A

Uterine tubes

Uterus

Superior portion of the vagina

49
Q

In what week does sex determinate begin in the embryo?

A

Week 7

Until then they are indifferent

50
Q

The gonads appear initiailly as a pair of longitudinal ridges. Name these two ridges?

A

Gonadal ridges

Urogential ridges

**indifferent to the sex**

51
Q

At what week of development is the genital ridges appear?

A

Week 5

52
Q

At what week does the germ cells appear in the genital ridges?

A

Week 6

53
Q

Describe the journey the germ cells must take to get to the genital ridges?

A

Primoridal germ cells originate in the epiblast, they migrate through the primitive streak and reside in the endoderm cells in the wall of the yolk sac.

They migrate along the dorsal mesentery of the hindgut arriving at the primitive gonads at the beginning of week 5.

They invade the genital ridges in week 6.

54
Q

The primoridal germ cells have a ___ infleunce on the development of the gonads.

A

Inductive- i.e. can interfere with the development of the gonads.

This is because if they fail to reach the ridges, the gonads do not develope

55
Q

What happens to the gonads if the primoridal germ cells do not reach the genital ridges?

A

The gonads do not develop

56
Q

Where does the primordial germ cells originate?

A

Yolk sac

Reside amongst endoderm cells

57
Q

Why does the primoridal germ cells move out of the embryo into the yok sac?

A

To protect them from the signals that occur in the embryo

58
Q

What does the primordial germ cells form once they have arrived in the gential ridges?

A

they form the primitive sex cords

irregularly shaped cord-like structures

59
Q

Describe the development process of the primitive sex cords in males?

A

SRY gene encodes the testis-determining factor

The tesis-determining factor causes the primitive sex cords to continue to proliferate and pentrate deep into the medulla.

The forms the testis or medullary cords

60
Q

What is the function of the SRY gene?

A

Sex determining region of Y chromosome

Encodes for the testis-determining factor

The testis-determining factor acts on somatic cells causing the proliferation of the sex cords.

61
Q

Towards the hilum of the gland, what happens to the primitive sex cords?

A

Cords break up into a network of cell strands that develop into the tubules

62
Q

The testis cords become horseshaped in week 4. They are now composed of Sertoli cells and Leydig cells lie between the testis cords.

What does the sertoli cells produce?

A

anti-Mullerian hormone

63
Q

The testis cords become horseshaped in week 4. They are now composed of Sertoli cells and Leydig cells lie between the testis cords.

What does the Leydig cells produce?

A

Testosterone

64
Q

The testis cords become horseshaped in week 4. The testis cords are now composed of what cells?

A

Sertoli cells

65
Q

The testis cords become horseshaped in week 4. Which cells lie between the testis cords?

A

Leydig cells

66
Q

The testis cords remain ___ until puberty

A

Solid

67
Q

What happens to the testis cords at puberty?

A

The testis cords acquire a lumen, thus forming the seminferous tubules.

68
Q

Once the seminiferous tubules are formed, describe which structures join?

A

Once the seminferious tubules are formed they join the rete testis tubules.

The rete testis tubules join the ductuli efferentes

69
Q

Which two structures link to form the ductus deferens?

A

Rete testis

Efferent ductules

70
Q

If Wnt 4 protein is present, which sex will develop?

A

Female

71
Q

What is the function of Wnt 4?

A

Ovary determining gene

Active signal required for female reproductive development

72
Q

Once the primordial germ cells reach the genital ridge. Describe what happens next in females?

A

The surface epithelium continues to proliferate.

The primordial germ cells begin to divide (via mitosis) forming a pool of oocytes. After which they enter a state of meiotic arrest.

73
Q

Outline the development of the external genitalia?

A

In week three of development, mesenchyme cells migrate around the cloacal membrane forming a pair of cloacal folds

From cranial to cloacal membrane, the folds unite to form the genital tuberlce.

Caudally, the folds are subdivided inot urethral folds (anteriorly) and anal folds (posteriorly).

74
Q

The genital swellings become visible of each side of which strucutre?

A

Urethral folds

75
Q

Describe the clinical condition hypospadias?

A
  • Fusion of the urethrals folds is complete resulting in an abnormal openings of the urethra occuring along the inferior aspect of the penis.
  • Varies in severity with 70% being mild
  • Treatment: surgical correction to allow urination while standing. Around the 12 month of age
76
Q

Describe the clinical coniditon uterus bicornis?

A
  • Characterised by the uterus having two horns entering a common vagina
  • A result of the lack of fusion of the paramesonephric (mullerian) ducts.
  • Only the upper areas of the uterus are involved.

Phase 2: Reproduction, Nephrology and Urology (25 decks)

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