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BS - Reproductive System > Development of the Gonads > Flashcards

Development of the Gonads Flashcards

1
Q

What is established during gastrulation?

A

The primitive streak develops and establishes a right and left side of the developing embryo

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2
Q

What happen during craniocaudal embryonic folding?

A

The cranial and caudal end of the embryo come into closer proximity due to the weight of the amniotic fluid pushing them closer together

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3
Q

What happens during lateral embryonic folding?

A

The 2 lateral edges of the embryonic disc come into closer proximity and fuse together in the midline

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4
Q

What is the exception of areas that fuse during lateral embryonic folding?

A

The lateral edges fuse everywhere except at the level of the midgut

This is at the level of the vitelline duct - which connects to the yolk sac

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5
Q

Which gonad is involved in determining genetic sex?

A

The sperm

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6
Q

What is meant by the indifferent stage of development?

A

The developing gonad is the same in males and females for the first 7 weeks

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7
Q

When does genetic determination of sex occur?

A

At fertilisation

Sex is determined by whether the sperm carries an X or a Y chromosome

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8
Q

What is the precise component of the Y chromosome that determines sex?

A

The SRY gene of the Y-chromosome

This initiates production of testis-determining factor (TDF)

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9
Q

What happens at fertilisation when there is no Y chromosome?

A

There is no SRY region

This means that no TDF is produced and an ovary develops

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10
Q

What is the reproductive system derived from?

A

Intermediate mesoderm

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11
Q

What will the intermediate mesoderm go on to form?

A

The intermediate mesoderm forms the urogenital ridge

The gonads develop from the genital ridge of the urogenital ridge

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12
Q

What else is formed from the urogenital ridge?

A

The urogenital ridge goes on to form the urinary system and the reproductive system

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13
Q

During which weeks of development is the indifferent gonad present?

A

Weeks 5-6

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14
Q

What happens to the indifferent gonad as the epithelium covering the urogenital ridge begins to proliferate?

A

The epithelium of the genital ridge proliferates and thickens

It encroaches into the underlying mesenchyme to form primitive sex cords

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15
Q

What are primitive sex cords?

A

The proliferations of epithelium that project into the mesenchyme

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16
Q

What happens during week 6 of development?

A

The primordial germ cells migrate from the yolk sac to the genital ridge

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17
Q

How do the primordial germ cells arrive at the genital ridge?

A

They migrate through the yolk sac and the dorsal mesentery

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18
Q

Developmentally, how can the indifferent gonad be split into 2 distinct regions?

A
  1. outer cortex

2. inner medulla

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19
Q

What determines the fate of the medullary and cortical regions?

A

Whether the medulla or the cortical region is developed depends on whether TDF is present

Developing the medulla = testes

Developing the cortex = ovaries

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20
Q

What information is contained within the primordial germ cells?

A

The genetic information that determines whether a male or female will develop

44+XX or 44+XY

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21
Q

If there is a Y chromosome and SRY gene present, what will and won’t develop?

A
  1. primitive sex cords (medullary cords) continue to develop further
  2. the tunica albuginea will develop
  3. no cortical cords will develop
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22
Q

If there is an X chromosome present, and no SRY gene, what will and won’t develop?

A
  1. the medullary cords regress and cortical cords develop

2. the tunica albuginea does not develop

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23
Q

What happens to the primordial germ cells?

A

The medullary (primitive sex cords) invest the primordial germ cells

They are invested by the somatic support cells within the cords

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24
Q

Under the influence of TDF, what happens to the primitive sex cords?

A

The primitive sex cords continue to develop into medullary (testis) cords

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25
Q

What do the medullary (testis) cords dorm as they go further in to the medulla?

A

Going further into the medulla, the cords begin to break up and form rete testis

The testis cords develop to form C-shaped tubules called seminiferous tubules

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26
Q

What is the tunica albuginea?

A

It is the connective tissue that develops around the testes

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27
Q

What happens to the seminiferous tubules during puberty?

A

They are solid cords up until puberty

A surge of hormones causes them to canalise and the male can make mature sperm

28
Q

What happens to the primitive sex cords if there is no TDF?

A

The medullary cords regress and they are broken down into small pieces

29
Q

What produces the cortical cords in the ovary?

Where do they develop?

A

The surface epithelium continues to proliferate to produce cortical cords

These develop within the cortex of the developing gonad

30
Q

What is the role of the cortical cords?

A

They invest the primordial germ cells

They split and surround the oocytes

31
Q

What do the somatic support cells form in the ovary?

A

The somatic support cells invest the primordial germ cells and form follicular cells

32
Q

what is the role of the follicular cells?

A

They signal back to the primordial germ cell and cause them to undergo the first stage of meiosis

This forms a primary oocyte

33
Q

What happens to a female at puberty?

A

Hormones allow the primary oocytes to mature and ovulation begins

34
Q

Whereabouts in the body do the male and female gonads develop?

A

The gonads develop on the posterior abdominal wall

This is where the genital ridge is

35
Q

What pulls the testes towards the anterior abdominal wall?

When does this occur?

A

The extraabdominal gubernaculum shortens and pulls the testes towards the AAW

This happens during week 7-12

36
Q

Where does the gubernaculum pull the testes to?

A

The deep inguinal ring

They remain here from the 3rd-7th month

37
Q

What is the inguinal canal formed from?

A

The processus vaginalis

This is an invagination of the parietal peritoneum

38
Q

What happens to the testes after the 7th month?

A

The gubernaculum begins shortening again to pull the testes through the inguinal canal

39
Q

What is the gubernaculum?

A

It is a tendinous cord that attaches to the inferior pole of the gonad

It initially extends out and attaches to the pelvis

40
Q

What else helps to aid the movement of the testes through the inguinal canal?

A

The abdominal organs as they increase the intraabdominal pressure

41
Q

When do the testes reach the scrotum?

A

By the 9th month of development

42
Q

What is the purpose of the processus vaginalis?

A

it makes the road through which the testis are pulled through

43
Q

What happens to the processus vaginalis after birth?

A

Within the 1st year, the processus vaginalis obliterates leaving a remnant around the testes

This is the tunica vaginalis

44
Q

What happens if the processus vaginalis fails to close off during the first year?

A

This can lead to a hernia as other structures can pass through the patent processus vaginalis

45
Q

What must the testes pass through as they descend?

A

As the testes descend through the abdominal wall, they must pass through the 3 muscular layers and the relevant fascia

46
Q

What do the testes pick up as they pass through the deep inguinal ring?

A

As they pass through the inguinal canal they are accompanied by a part of the peritoneal lining of the abdominal cavity

This is the processus vaginalis

47
Q

What is the external spermatic fascia formed from?

A

External oblique muscle

48
Q

What is the cremasteric fascia formed from?

A

Internal oblique muscle

49
Q

What is the internal spermatic fascia formed from?

A

Transversalis fascia

50
Q

What is the cremasteric reflex?

A

If you touch the inner aspect of the thigh, the cremasteric muscle contracts and pulls the testes towards the thigh

51
Q

What is the cremasteric reflex controlled by?

A

The genitofemoral nerve

As the testes pass through the fascia, it takes some of the muscle fibres with it

52
Q

What happens in patent processus vaginalis?

A

Parts of the processus vaginalis may remain unfused leaving small cysts

53
Q

What happens if the cysts begin to produce fluid?

A

They swell and form fluid-filled cysts

This is a hydrocele

54
Q

What happens if the processus vaginalis remains completely patent to the abdominal cavity?

A

INdirect inguinal hernia

This occurs when the intestine protrude through the inguinal canal

55
Q

How can a hydrocele be distinguished from other solid tissues (e.g. tumour/hernia)?

A

Through transillumination

Light will pass through the hydrocele but the solid tissue wou;ld block light

56
Q

How are hydroceles treated?

A

They are benign but may cause discomfort

They are removed surgically

57
Q

How many people are affected by cryptorchidism?

A

1-4% of births

Most spontaneously correct by 3 months of age

58
Q

What is a cryptorchidism?

A

The testes become stuck along their path of descent

This is usually in the high scrotal region

59
Q

What happens in the cases of cryptorchidism that do not correct themselves?

A

Those that remain undescended are corrected surgically at 4-6 minutes

60
Q

What is cryptorchidism associated with?

A

an increased risk of testicular cancer and infertility

61
Q

What happens to the gubernaculum during descent of the ovaries?

A

It passes through the inguinal canal and inserts onto the labia majora

62
Q

Where to the ovaries descend to?

A

The level of the pelvic brim

63
Q

What does the gubernaculum form in a female adult?

A

The ovarian ligament proper and the round ligament of the uterus

64
Q

In a male, what will the somatic support cells change to become?

A

Sertoli cells

These invest primordial germ cells migrating from the yolk sac

65
Q

What will the sertoli cells and the primordial germ cells form?

A

Testes cords

The testes cords then develop into seminiferous tubules

BS - Reproductive System (12 decks)

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