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Jess Repro > Embryology > Flashcards

Embryology Flashcards

1
Q

When does structural vs functional development occur?

A

Structural - in utero

Functional - after birth

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2
Q

Where do primordial germ cells migrate in the third week?

A

Along the wall of the hindgut and dorsal mesentery to the genital ridge

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3
Q

What are the 3 sources of gonad development?

A
  1. Condensed mesenchyme (from the genital ridge)
  2. Colemeic epithelium
  3. Gonocytes aka primordial cells
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4
Q

Compare the mesonephric duct to the paramesonephric duct

A

Mesonephric duct/Wolff duct becomes the vas deferens and epididymis in males

Paramesonephric duct/Müller duct becomes the uterus and uterine tube in females

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5
Q

Compare the differences in gonadal development in males and females based on these features: gonadal chords, corticol chords, tunica albuginea

A

Males:

  • Gonadal chords develop and have germ cells within that form the forerunner for seminiferous tubules -> connect to rete testis -> leads to epididymis duct
  • NO cortical chords
  • Thick tunica albuginea

Females:

  • Gonadal chords degenerate
  • Cortical chords develop (and protrude inwards)
  • NO tunica albuginea
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6
Q

As the mesonephros regresses what do the tubules divide into in males and what is their function?

A

The tubules divide into epigenital and paragenital tubules…
Epigenital: join the rete testis and form an efferent ductule which converges into ductulli efferentes -> vas deferens -> urogenital sinus

Paragenital: form paradidymis and do not join the chords of rete testis

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7
Q

When does the gubernaculum become active and what does it do in males and females?

A

Activity begins at the 6th week…
Males: guides the testis down from the future abdomen to its root in the scrotum

Females: rooted in the labia and persists as the ovarian ligament and round ligament which connects the ovary to the uterus and stabilizes the uterus

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8
Q

What is left of the mesonephros in females?
List them in order of lateral -> medial

What can go wrong at any one of these places?

A

All of the mesonephros + duct disappears EXCEPT 3 small parts…

  1. Epoophoron
  2. Paraoophoron
  3. Gartner’s duct

All can become irritated, inflamed and form possible tumours

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9
Q

Where does the paramesonephric duct originate from? What structures does it open into superiorly and inferiorly?

A

The Hydatid of Morgani (hangs off the uterine tube)

Superiorly opens into the abdominal cavity and inferiorly makes contact with the cloaca

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10
Q

What is the tunica vaginalis and what forms it?

A

Tunica vaginalis is the pouch of serous membrane that covers the testes

As the testis descends they drag the peritoneal membrane with them… the peritoneal membrane eventually detaches from the peritoneum and forms the tunica vaginalis that protectively covers the testis

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11
Q

What happens if the testis never drop?

What is the name of this condition?

A

Body temp is too high for sperm production, the affected individual will be infertile

Cryptochordisim

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12
Q

What can happen if the peritoneal membrane never disconnects?

A

Can cause an accumulation of fluid, hernia, etc

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13
Q

What important prostatic and seminal vesicle development happens around week 11 and 13? What happens afterwards?

A

11: 5 cords of prostatic tissue develop lumina and acini
13: prostatic acini develop secretory activity

Mesenchyme surrounding the prostate develops smooth muscle and CT, eventually, epithelial structures grow out and enlarge as the prostate (producing fluid which combines to form semen)

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14
Q

What are skene’s glands? Where are they and where do they come from?
*include another name for them

A

Skene/paraurethral glands are glands located on the anterior wall of the vagina, they are the ‘female prostate’ and come from the urogenital sinus

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15
Q

What is the significance of the verumontanum?

A

Its a landmark of the prostatic urethra and has 3 openings:

  1. Prostatic utricle (representing the paramesonephric duct which does nothing in males)
  2. Two ejaculatory ducts on either side
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16
Q

What is the ultimate fate of the mesonephric duct?

A

It’s gradually absorbed into the wall of the urogenital sinus

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17
Q

How does cloacal partitioning occur?

A

The urorectal septum grows down dividing the urogenital sinus anteriorly and the anorectal canal posteriorly

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18
Q

What forms the genital tubercle component of external genitalia in males and females?

A

Males: penis
Females: clitoris

19
Q

What happens to the urethral folds in females and males, and which hormone is influential in males?

A

Females: folds around the urethra (parallel to the midline) and stays as labia minora

Males: Elongates and fuses to form spongy urethra and glans penis! *Influenced by dihydrotestosterone produced by the gonad (no fusion in females as their gonads do not produce this hormone)

20
Q

What happens to the labioscrotal folds in males and females?

A

Females: labia majora
Males: Scrotum

21
Q

Which portion of the urogenital sinus does the phallus arise from? What does the phallus arise from?

A

The phallic part, the phallus arises from the endoderm

22
Q

What is happening in phallus development around the 6-7th week and the 14th week, (and on which surface)?

A

6-7: the vertical urethral plate splits to form the urethral groove and urethral fold on the penis’ ventral surface

14: Urethral folds fuse to form the penile urethra

23
Q

What happens in hypospadias and epispadias? Which is more rare?

A

Hypospadias: The urethra opens on the ventral surface

Epispadias: rarer, urethra opens on the dorsal surface
*Both cases urine can dribble out

24
Q

Which hormones play a part in directing the differentiation of testis, internal (ducts) and external genitalia in males? Where is the genetic information that codes for this found?

A

The production of certain hormones is expressed in the SRY region of the Y chromosome:

  1. The mesonephric duct is supported by androgen secretions (testosterone)
  2. The paramesonephric duct degenerates as the testis secrete Mullerian inhibiting substance
25
Q

Define gametogenesis, how does it begin in each sex?

A

The formation of haploid cells begins with the colonizing of the primordial gland (the cortex in females and medulla in males). Germ cells then proliferate via mitosis, genetically reshuffle and reduce to haploid cells.

26
Q

What do female gamete germ cells initially form, are they haploid or diploid?

A

Become oogonia, diploid cells.

27
Q

What gives rise to the primordial germ cells embryologically?

A

The epiblast

28
Q

When is the max number of oogonia that will ever be produced reached and when do they begin meiosis?

A

These diploid cells proliferate until mid-gestation, most will die during gestation and the remainder (~2 million) are stimulated by surrounding cells to begin meiosis before birth

29
Q

How is a primary oocyte formed?

A

Before birth; meiosis stops at phase 1 prophase to form a primary oocyte

30
Q

What makes up a primordial follicle and how many does a female typically have?

A

A primordial follicle is formed by one primary oocyte + a single layer of surrounding granulosa cells

Each female is born with ~2million and can never produce more!

31
Q

Name the three phases of the menstrual cycle and when each of them occurs

A
  1. Preparatory: 1-12 days, this is the phase the follicles proliferate and there is transitioning from a primordial follicle to pre natural follicle
  2. Ovulation: 12-14 days (all other activated follicles begin to degenerate)
  3. Waiting: 14-28 days, luteal or secretory phase
32
Q

Which hormones trigger follicular growth? What hormone is secreted in response?

A

FSH and LH trigger follicular growth, in response, the theca interna secretes increasing amounts of estrogen

33
Q

What else is forming as the primordial follicle develops into a pre natural follicle in the follicular stage?
(name four things).

A
  1. The ZP forms
  2. The granulosa cell layers develop outside,
  3. Theca (internal and externa) forms
  4. The antrum forms; under hormonal influence granulosa cells accumulate antral fluid making spaces between the granulosa and the oocyte
34
Q

How and when does the secondary oocyte form? When is the division finally complete?

A

One mature graffian follicle becomes dominant and is destined for ovulation: just before ovulation meiosis II restarts and arrests at metaphase, forming a secondary oocyte. The second division doesn’t occur until fertilization!

35
Q

Why are polar bodies produced?

A

Telophase results in an unequal division of cytoplasm; resulting in one ovum and polar bodies

36
Q

What happens to the follicles in the ovulation phase?

A

All other activated follicles (that didn’t release an ovum) begin to degenerate: they first reorganize to form a corpus luteum

37
Q

Why is the corpus luteum an endocrine gland?

A

It grows under the influence of LH and secretes estrogen and progesterone

38
Q

When does the corpus luteum die and what does it then become?

A

Dies after 14 days if the pregnancy doesn’t occur, fills with scar tissue and becomes the corpus albicans

39
Q

Where do XY germ cells colonize? How do their divisions differ from XX germ cells?

A

They colonize the medulla, and unlike oocytes, their mitotic divisions produce equal daughter cells/spermatogonia (not polar bodies)

40
Q

What happens to the male gamete around puberty?

A

The cords hollow out to form seminiferous tubules, spermatogonia cluster around the basal membrane (since there is raw material always available to make sperm here), and spermatogenesis begins

41
Q

Describe the process of spermatogenesis (including how primary and secondary spermatocytes and spermatids are formed!)

A

At puberty, the spermatogonium develops into the primary spermatocytes: the 1st meiotic division results in two haploid secondary spermatocytes

Secondary spermatocytes: The 2nd meiotic division results in 4 haploid spermatids!
The future spermatids are also simultaneously moving towards the lumen

42
Q

What happens during spermiogenesis?

A

Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature, elongated spermatozoa. They are then released into the lumen of the seminiferous tubule

*further functional maturation happens as they pass down the tubule, through rete testis, ductulli efferentes, epididymis, ductus/vas deferens and female tract

43
Q

What composes semen?

A

50% of the secretions come from the seminal vesicle
20% of secretions come from the prostate
Sperm (comes out via vas deferens)
Secretions from bulbourethral glands

44
Q

What hormone stimulates the release of an ovum as ovulation begins?

A

The LH surge

Jess Repro (18 decks)

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