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SUGER Physiology > Puberty and Embryology of Genitalia > Flashcards

Puberty and Embryology of Genitalia Flashcards

1
Q

Which partner determines fetal sex?

A

The male. Sperm can either be 23x or 23y, whereas ovum can only contribute an X chromosome.
Male = 23XY
Female = 23XX

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2
Q

Which gene switches on testicular development?

A

SRY.

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3
Q

What is an oocyte?

A

A female gameteocyte. An egg develops by meiosis from an oocyte.

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4
Q

List the advantages of meiosis.

A
  1. Two meiotic divisions prevent polyploidy
  2. Key step in germ cell differentiation
  3. Increases chromosomal combinations and genetic variability
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5
Q

When do the sex organs start forming?

A

After 6 weeks. Before this, the gonads are identical in both males and females.

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6
Q

In females, how many of the two X chromosomes are functional?

A

Only one. The other condenses to form sex chromatin/Barr Body.

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7
Q

Embryologically, where are male and female gonads derived from?

A

Urogenital ridge

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8
Q

In the presence of the SRY gene, which cells do the gonads differentiate into?

A

Sertoli cells and Leydig cells

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9
Q

What do Sertoli cells release and what does the substance do?

A

They release MIF = Mullerian inhibiting factor

Causes Mullerian ducts to regress

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10
Q

What do Leydig cells release and what does the substance do?

A

They release testosterone.

Leads to development of Wolffian ducts.

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11
Q

What do the Wolffian ducts form?

A
  1. Epididymis
    2, Vas deferens
  2. Seminal vesicles
  3. Ejaculatory duct
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12
Q

What does dihydrotestosterone lead to the development of?

A
  1. Penis
  2. Scrotum
  3. Prostate
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13
Q

In the absence of MIF, what do the Mullerian ducts form?

A

Ovaries
Uterus
Fallopian tubes

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14
Q

In the absence of testosterone, what forms?

A

Wolffian duct degenerates.

Vagina and external genitalia form.

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15
Q

What are germ cells?

A

Cells that develop into sperm or ova i.e. gametes.

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16
Q

Where do germ cells originate from?

A

Yolk sac of hind gut

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17
Q

What occurs in the first stage of germ cells developing into gametes?

A

Mitosis.

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18
Q

When does mitosis of germ cells occur in males?

A

Male puberty, continues through life

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19
Q

When does mitosis of germ cells occur in females?

A

During fetal development

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20
Q

What is the second stage of gametogenesis?

A

Meiosis

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21
Q

How many chromosomes do gametes have?

A

23 (NOT 46)

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22
Q

When does the second meiotic division occur in males?

A

Continuously after puberty.

23
Q

When does the second meiotic division occur in females?

A

After fertilisation of a secondary oocyte by a sperm.

24
Q

Where does meiosis occur in males?

A

Seminiferous tubules

25
Q

Where does meiosis occur in females?

A

Ovaries

26
Q

Which hormone levels increase during puberty?

A

GnRH, GHRH, FSH, LH, growth hormone

27
Q

What is puberty influenced by?

A

Nutrition, insulin, socio-cultural, genetics, exercise

28
Q

What is the function of the blood testes barrier (sertoli cell barrier)?

A

Prevents the movement of chemicals from the blood into the lumen of the seminiferous tubule.
Barrier ensures proper conditions for germ cell development.

29
Q

How do the sertoli cells form a barrier?

A

Adjacent sertoli cells are joined by tight junctions

30
Q

What are undifferentiated male germ cells called?

A

Spermatogonia

31
Q

Which 2 types of daughter cell do spermatogonia form at puberty?

A

Type A: Remain outside blood-testis barrier. Produce more daughter cells until death.

Type B: Differentiate into primary spermatocytes

32
Q

Once primary spermatocytes have passed through the blood-testes barrier, how do they develop?

A

Meiosis 1: 2 secondary spermatocytes

Meiosis 2: 4 spermatids

33
Q

What is spermiogenesis?

A

The transformation of spermatids to spermatozoa.

34
Q

What is the tail of sperm made of?

A

Flagellum - propels sperm

35
Q

What is found at the tip of the sperm?

A

Acrosome - a protein filled vesicle containing enzymes to penetrate the egg

36
Q

What is semen made up of?

A

Seminal vesicle fluid (60%) and sperm (10%) .

37
Q

Summarise the path of sperm to outside.

A
  1. Seminiferous tubule
  2. Rete testis
  3. Efferent ducts
  4. Epididymis
  5. Vas deferens
  6. Ejaculatory duct
  7. Urethra
  8. Penile urethra
38
Q

Briefly summarise the male gonadal axis.

A
  1. Hypothalamus secretes GnRH
  2. GnRH binds to receptors in the anterior pituitary gland
  3. LH and FSH are released and travel to the testicles
  4. LH stimulates Leydig cells to produce testosterone
  5. FSH stimulates sertoli cells to produce ABG (keeps testosterone within seminiferous tubules) and inhibin (supports spermatogenesis)
  6. Increased levels of testosterone and inhibin cause negative feedback
  7. Results in decreased production of LH and FSH
  8. Results in decreased production of testosterone and inhibin
39
Q

How many eggs do the ovaries contain at birth?

A

2-4 million. No new eggs are made after birth

40
Q

What are undifferentiated female germ cells called?

A

Oogonia

41
Q

What do ooginia develop into via mitosis?

A

Primary oocytes

42
Q

When do primary oocytes undergo meiosis 1?

A

In-utero before 12 weeks

43
Q

When does meiotic arrest 1 occur?

A

At metaphase 1 until PUBERTY

44
Q

What is formed after meiosis 1?

A
  1. A secondary oocyte with all the cytoplasm

2. a first polar body that is very small and non functional

45
Q

What occurs during meiosis 2?

A

Secondary oocyte develops into ovum.

46
Q

When does meiotic arrest 2 occur?

A

At metaphase 2 until FERTILISATION

47
Q

What is formed after meiosis 2?

A
  1. An ovum with all the cytoplasm

2. Second polar body that is very small and non functional

48
Q

Give three main differences between spematogenesis and oogenesis.

A
  1. 1 spermatocyte gives 4 spermatozoa whereas 1 oocyte gives 1 ovum
  2. In males, both maturations occur in testis. In females, one occurs in ovaries, the other in fallopian tube after fertilisation
  3. Continuous process in males, disjointed process in females
49
Q

Briefly summarise the female gonadal axis.

A
  1. Hypothalamus secretes GnRH
  2. GnRH binds to receptors in the anterior pituitary gland
  3. LH and FSH are released and travel to ovaries
  4. LH stimulates production of oestrogen
  5. FSH stimulates production of inhibin
  6. Increased levels of oestrogen and inhibin leads to negative feedback
  7. Leads to decreased production of GnRH, Lh and FSH
  8. Results in decreased production of oestrogen and inhibin
50
Q

What are the first signs of puberty in males and females?

A

Males: Testicular enlargement
Females: Breast development

51
Q

Which hormone produced in the hypothalamus is necessary for normal spermatogenesis?

A

GnRH

52
Q

What is contained within the inguinal canal in males?

A

Ilia-inguinal nerve

Spermatic cord

53
Q

What is contained within the inguinal canal in females?

A

Ilia-inguinal nerve

Round ligament

54
Q

What is contained within the spermatic cord?

A
  1. Vas deferens
  2. Cremasteric artery, testicular artery, artery of the Vas deferens (same names for veins)
  3. Genital branch of gentifemoral nerve
  4. Lymphatic vessels

SUGER Physiology (11 decks)

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