Development of Genitalia Flashcards

1
Q

Describe the composition and function of the Coelomic Epithelium (mesothelium).

A
  • Outer Somatic Mesoderm lining the Urogenital (gondal) Ridge
  • Gives rise to PRIMARY SEX cords
  • Sex cords will becomes the Cortex and Medulla of the Gonads
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2
Q

Where are the Primordial Germ Cells (giving rise to oocyte and sperm) located?

A

Allantois and Yolk Sac

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3
Q

Which structures in the developing embryo are going to form the internal genitalia of males and females?

A

Males: Mesonephric Duct
Females: Paramesonephric Duct

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4
Q

Which germ layer are the Sertoli Cells and Leydig Cells coming from?

A

Sertoli Cells: Coelomic Epithelium

Leydig Cells: Intermediate Mesoderm

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5
Q

Which germ layer are the Follicle cells and Thecal cells coming from?

A

Follicle Cell: Coelomic Epithelium

Thecal Cell: Intermediate Mesoderm

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6
Q

Where do the Primordial Germ Cells come from?

A

Epiblast during 2nd week

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7
Q

Why are the Primordial Germ Cells located in the Yolk Sac and Allantois during the 4th week of embryogenesis?

A

They need to be as far away from the differentiation signals as possible so they can remain as a stem cell!

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8
Q

Where is the oocyte in meiosis during Ovulation and Fertilization?

A

Ovulation: Meiosis I
Fertilization: Meiosis II

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9
Q

Describe the Central and Secondary events involved in sex determination.

A

Central: Differentiation of the Testes
Secondary: Production of humoral factors by gonads

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10
Q

Which DNA binding protein is going to turn on production of the male genitalia?

A

Sex Determining Region Y (SRY) Gene

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11
Q

Describe what happens to sex development when SRY is present vs. when it is absent.

A

PRESENT: Intermediate mesoderm develops into Leydig Cells, produces Testosterone and allows Mesonephric Ducts to persist.
- Coelomic Epithelium develops into Sertoli Cells, they produce Anti-Mullerian Hormone, and cause the degeneration of the Paramesonephric Ducts.

ABSENT: Intermediate Mesoderm develops into Thecal Cells, does not produce Testosterone, and Mesonephric Ducts will degenerate.
- Coelomic Epithelium develps into Follical cells, does not produce Anto-Mullerian Hormone, Paramesonephric Ducts will persist!

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12
Q

Describe the Phenotype of an individual who is XY but does not have enough Anti-Mullerian Hormone.

A
  • Development of both Female and Male Internal Genitalia

- Development of External Male Genitalia

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13
Q

Describe the Phenotype of an individual who is XY but has a deficiency in 5a-reductase.

A
  • Ambiguous External Male Genitalia (Until Puberty)

- Internal Male Genitalia

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14
Q

Describe the Ovotesticular Disorder of Sexual Development.

A
  • Have both Testicular and Ovarian Tissue and an ovotestis

- Phenotype can be male or female, but External Genitalia is ambiguous

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15
Q

Describe the 46, XX Disorder of Sexual Development.

A
  • Caused by exposure of female fetus to excessive androgens (Congenital Adrenal Hyperplasia)
  • Ovaries are present, but EXTERNAL genitalia is masculinized
  • Clitoral hypertrophy, partial fusion of labia majora, and persistent urogenital sinus
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16
Q

Describe the 46, XY Disorder of Sexual Development.

A
  • Caused by inadequate production of Testosterone and/or AMH or due to androgen insenitivity syndrome
  • Testicular development is normal or messed up and may have persistent paramesonephric ducts
  • External Genitalia are Female or Ambiguous
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17
Q

Describe the things that are happening to the gonads during the 5th week of development.

A
  • Gonadal Ridge appears on medial side of mesonephros

- Primary Sex Cords in the medulla (Coelomic Epithelium) will persist in Males and Degenerate in Females.

18
Q

Describe the things that are happening to the gonads during the 6th week of development.

A
  • Primordial Germ cells invade the gonadal ridges by the 6th week and migrate along the Dorsal Mesentery
  • Secondary Sex Cords in the Cortex will come in (Coelomic Epithelium)
19
Q

Describe the Development of the Testis.

A
  • Primary Sex Cords are going to Persist
  • They become Seminiferous cords and Sertoli Cells
  • Connective Tissue is going to become Leydig Cells and the Tunica albuginea
20
Q

Describe the Develop of the Ovary

A
  • First wave of Coelomic Epithelium comes into the Medulla and degenerates
  • Secondary Sex Cords in the cortex are going to rise to Primordial Follicles and Granulosa Cells
  • Intermediate Mesoderm that is present will become the Thecal Cells
  • Active mitosis of oogonia occurs during fetal life producing the primordial follicles
21
Q

Which structures are going to come from the Mesonephric Duct? (4)

A
  1. Epididymis
  2. Ductus Deferens
  3. Seminal Vesicle
  4. Ejaculatory Duct
22
Q

Which structures are going to come from the Mesonephric Tubules? (2)

A
  1. Efferent Ducts

2. Rete Testis

23
Q

What is the remnant of the Paramesonephric Duct in males?

A

Prostatic Utricle (Remnant of the Vagina)

24
Q

Which structures are going to be formed from the Cranial and Caudal Paramesonephric Ducts?

A

Cranial: Uterine Tubes
Caudal: Uterovaginal Primordium

25
Q

When the Paramesonephric Ducts come down, fuse and project into the urogenital sinus, which structure is formed?

A

Sinus Tubercle

26
Q

What are the names of the structures that are part of the Remnant of the Mesonephric Ducts in Females?

A

Epoophoron and Paroophoron (Located in the Mesosalpinx)

27
Q

What is a Gartner’s cyst?

A

Remnants of the mesonephric ducts that are on the Lateral Sides of the Vagina

28
Q

Describe the formation of the Sinovaginal Bulbs.

A
  • The Sinovaginal Bulbs are endodermal outgrowths
  • They extend from the Urogenital Sinus to the Uterovaginal Plate
  • The Sinovaginal Bulbs fuse to form the Vaginal Plate
29
Q

Describe the purpose of the Vaginal Plate.

A

Epithelium that will grown and then later break down (apoptosis), forming the lumen of the vagina.

30
Q

Describe the Hymen.

A

The Hymen is going to be the an Endodermal derivative that forms a membrane at the Distal Opening of the Vagina.

31
Q

What is the composition of the Vagina in terms of embryonic origin?

A

Distal 2/3 = Endoderm (from the Urogenital Sinus)

Proximal 1/3 = Caudal Paramesonephric Duct

32
Q

Describe how the following Uterus Abnormalities occur:

  1. Uterus Didelphys
  2. Uterus arcuatus
  3. Uterus Bicornis
  4. Uterus Bicornis unicollis 1 rudementary horn
  5. Cervical Atresia
  6. Vaginal Atresia
A

1-3. Varying forms of Paramesonephric Ducts not fusing properly

  1. Degeneration of One of the paramesonephric ducts
  2. Degeneration of the most Caudal Portion of the Paramesonephric Ducts
  3. Sinus Tubercle Never FORMED!
33
Q

Which part of the Urogenital Sinus are the Prostate and Bulbourethral glands derived from?

A
  • Prostate: Pelvic Part of Urogenital Sinus (Endoderm)

- Bulbourethral Glands: Phallic Part of Urogenital Sinus (Endoderm)

34
Q

Which germ layer is the smooth muscle and connective tissue supplying the prostate and bulbourethral glands coming from?

A

Splanchnic Mesoderm

35
Q

Describe the formation of the External Male Genitalia.

A
  • Under the Influence of DHT
  • Genital Tubercle is going to elongate and give rise to the Glans Penis
  • Urethral Folds: Lateral Walls of urethra, Spongy Urethra, and Penile Raphe
  • Labioscrotal Swellings: Scrotum
36
Q

Describe the formation of the External Female Genitalia.

A
  • Under the Influence of Estrogen
  • Genital Tubercle becomes the Glans Clitoris
  • Urethral Folds: Frenulum of Labia Minora
  • Labioscrotal Swellings: Labium Majus and Mons Pubis
37
Q

Which germ layers are the Spongy Urethra and Navicular Fossa derived from?

A
  • Spongy Urethra: Endoderm

- Naicular Fossa: Surface Ectoderm

38
Q

Describe what happens during Hypospadias.

A
  • Opening of the Urethra is on the Ventral Side of the Penis
  • Glanular Hypospadius: Problem with the folding of Surface Ectoderm located in the Glans Penis
  • Penile Hypospadius: LACK of fusion with the Urethral Folds
  • Penoscrotal Hypospadius: Problem with fusion of the Labioscrotal Swellings
39
Q

Describe what happens during Epispadias.

A
  • Improper location of Genital Tubercles to the cloacal membrane (Opening of urethra is on DORSAL side of the penis)
  • Normally happens in conjunction with Ectopic Vesicae (Protrusion of the Bladder due to a defect in the Abdominal wall)
40
Q

Describe the different embryonic derivatives of the ligaments associated with the Ovary and Uterus. (4)

A
  1. Suspensory L.: Mesoderm, contains OVARIAN a.
  2. Ovarian L.: Cranial part of Gubernaculum
  3. Round L.: Caudal part of Gubernaculum
  4. Broad L.: Fusion of paramesonephric ducts brings along a peritoneal fold
    - Separates Pelvic Cavity
    - Rectouterine Pouch
    - Vesicouterine Pouch