Midterm 2 - Lecture 14 Flashcards

1
Q

Embryonic origin of organs/systems from the ectoderm

A
  1. reproductive tract
    - penis
  2. nervous system
    - hypothalamus
    - anterior and posterior pituitary
  3. oral cavity
  4. nasal cavity
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2
Q

Embryonic origin of organs and systems from the mesoderm

A
  1. reproductive system
    - gonads (testes)
    - epididymus, ductus deferens, accessory sex glands
  2. urinary system
  3. skeletal system
  4. blood vessels
  5. muscle
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3
Q

Embryonic origin of organs and systems from the endoderm

A
  1. digestive system
  2. respiratory system
  3. glandular systems
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4
Q

Embryonic development of the reproductive system

A
  1. Development of hypothalamic-hypophyseal system
  2. migration of primordial germ cells from the yolk sac
  3. sex cords develop in gonad and mesonephric renal system regresses
  4. sexual differentiation - sex evident from structures
  5. development of male ducts, organs and testes
  6. testicular descent into the scrotum
  7. masculinization/defeminization of hypothalamus
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5
Q

Where is the posterior lobe of the pituitary derived from?

A

infundibulum

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6
Q

Where is the anterior lobe of the pituitary derived from?

A

Rathke’s pouch

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7
Q

Does the male hypothalamus contain a surge center?

A

NO! only a tonic center

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8
Q

What does it mean by the male hypothalamus is “defeminized” during embryonic development?

A
  • surge center does not develop
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9
Q

What interaction plays an important role in not defeminizing the female hypothalamus?

A
  • interaction of Estradiol with the “carrier-protein” alpha-fetoprotein
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10
Q

How is the hypothalamus defeminized in males?

A
  • fetal testis produces Testosterone
  • T4 interacts with alpha-fetoprotein and is able to cross the blood brain barrier
  • aromatase then converts T4 into E2 and the surge center does not develop
    *it is actually the estradiol that defeminizes the surge center; but only T4 can cross the barrier
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11
Q

Timeline of male hypothalamus defeminization

A
  • process initiated when fetal testes starts to produce T4 (mid-late period of the 1st trimester)
  • complete defeminization requires postnatal exposure to T4
    *bull calves castrated at or near birth retain some surge center fxn and produce GnRH surges
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12
Q

What does the reproductive system develop in close proximity and at the same time as?

A
  • the renal system
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13
Q

What are the three embryonic renal systems?

A
  1. pronephros
  2. mesonephros
  3. metanephros
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14
Q

Pronephros

A
  • most primitive for of kidney found in the developing embryo
  • limited fxn and eventually degenerates
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15
Q

Mesonephros

A
  • fxnl kidneys of early mammalian embryo
  • eventually regresses and gives way to the metanephros
  • remnants of the mesonephros system remain and become portions of the repro tract
  • Mesonephric ducts (Wolffian ducts) contribute to male tract; paramesonephric ducts regress
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16
Q

Metanephros

A
  • final renal system that will eventually become the fxning kidneys in the adult animal
17
Q

Sex determining factors

A
  1. Testis determining factor (TDF)
  2. Testes develop
  3. Sertoli cells secrete anti-mullerian hormone (AMH)
  4. AMH causes degeneration of paramesonephric duct AND leydig cells to differentiate
  5. Testosterone ——-> development of male duct system
  6. Dihydrotestosterone ————-> development of penis, scrotum, and accessory sex glands
18
Q

Steroid pathway starting at progesterone

A
  • progesterone to T4
    a. 5alpha-reductase produces dihydrotesterone
    b. aromatase produces E2
19
Q

2 abnormalities of sexual differentiation

A
  1. gonadal dysgenesis
  2. male hermaphrodism
20
Q

Gonadal dysgenesis

A
  • incomplete development of testes
  • Ex. XXY Male (Klinefelter’s Syndrome) = malformation of seminiferous tubules; extremely low sperm production
21
Q

Male hermaphrodism

A
  • T4 deficiency or T4 insensitivity = testes present but incomplete ducts and/or external genitalia
  • 5alpha reductase deficiency = unable to convert T4 to dihydrotestosterone; tests and ducts present but with feminized external genitalia
22
Q

Fate of ambisexual undifferentiated gonad

23
Q

Fate of ambisexual paramesonephros ducts (mullerian ducts)

24
Q

Fate of ambisexual mesonephros ducts (Wolffian ducts)

A
  • efferent ducts
  • epididymus
  • ductus deferens
25
Fate of ambisexual urogenital sinus
- urethra - accessory sex glands
26
4 major steps of the descent of the testes
1. peritoneum in the inguinal regional and testicular gubernaculum join (testicular anchor) 2. growth and elongation of the fetal body away from the testes - as the body elongates the testes remain stationary in the lower abdomen 3. rapid growth of the gubernaculum in the scrotal region - as gubernaculum expands laterally it shortens and pulls testis through the inguinal canal - gubernaculum expansion creates the scrotal cavity 4. shrinkage of the gubernaculum within the scrotum - gubernaculum regresses to a small knot attaching the testis to the bottom of the scrotum - the cavity btw the visceral and parental tunics forms creating the scrotal vaginal cavity
27
2 abnormalities of testicular descent
1. cryptorchidism 2. inguinal herniation
28
Cryptorchidism
- failure of the testis or testes to descend out of the body cavity into the scrotum - bilateral cryptorchidism = infertility - unilateral cryptorchidism = reduced fertility - still displays normal male behaviour; T4 production not impacted
29
Inguinal Herniation
- portion of the gut (intestine) passes through the inguinal canal and enters the scrotal vaginal cavity