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

A

testis

23
Q

Fate of ambisexual paramesonephros ducts (mullerian ducts)

A

regresses

24
Q

Fate of ambisexual mesonephros ducts (Wolffian ducts)

A
  • efferent ducts
  • epididymus
  • ductus deferens
25
Q

Fate of ambisexual urogenital sinus

A
  • urethra
  • accessory sex glands
26
Q

4 major steps of the descent of the testes

A
  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
Q

2 abnormalities of testicular descent

A
  1. cryptorchidism
  2. inguinal herniation
28
Q

Cryptorchidism

A
  • 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
Q

Inguinal Herniation

A
  • portion of the gut (intestine) passes through the inguinal canal and enters the scrotal vaginal cavity