EMBRYOLOGY, RADIOLOGY, AND HISTOLOGY SUMMARY

4th week

When do germ cells migrate to genital ridges?

6th week

When do germ cells reach the genital ridges?

8th week

When do Leydig cells produce testosterone?

4th month

When do urethral folds close to form the penile urethra?

3rd-4th months

When does the prostate gland develop from the urogenital sinus?

28th-33rd week

When do testes descend through the inguinal canal and reach the scrotum?

64 days

What is the total duration of spermatogenesis?

40-100 million/mL

What is a normal sperm concentration in ejaculate?

Less than 20 million/mL

What sperm count usually indicates infertility?

2-5 mL

What is the typical volume of human ejaculate?

Less than 1.5 ml

What is the testicular volume for Tanner stage I (prepubertal)?

Between 1.6 and 6 ml

What is the testicular volume for Tanner stage II?

Between 6 and 12 ml

What is the testicular volume for Tanner stage III?

Between 12 and 20 ml

What is the testicular volume for Tanner stage IV?

Greater than or equal to 20 ml

What is the testicular volume for Tanner stage V (adult)?

What is the cutoff value for normal pre-menopausal ovary size on ultrasound?

What is the cutoff value for normal post-menopausal ovary size on ultrasound?

Up to 3 cm

What is the approximate size of a dominant follicle in the ovary?

5 weeks AOG

When is the gestational sac first visible on transvaginal ultrasound?

5.5 weeks AOG

When does the yolk sac become visible on ultrasound?

6 weeks AOG

When does the fetal pole/embryo become visible on ultrasound?

3 mm

What is the CRL at 6.0 weeks AOG?

6 mm

What is the CRL at 6.5 weeks AOG?

10 mm

What is the CRL at 7.0 weeks AOG?

13 mm

What is the CRL at 7.5 weeks AOG?

Ideally 2 cm or greater

What is the ideal distance between the edge of the placenta and the internal cervical os?

5-25 cm

What is the normal range for Amniotic Fluid Index (AFI)?

< 5 cm

What AFI value indicates oligohydramnios?

\> 25 cm

What AFI value indicates polyhydramnios?

1-4 mm

What is the endometrial thickness on days 1-4 of the menstrual cycle?

5-7 mm

What is the endometrial thickness on days 5-13 (early proliferative stage)?

What is the endometrial thickness on days 14-16 (late proliferative stage)?

≤ 16 mm

What is the endometrial thickness on days 16-28 (secretory phase)?

1-2.5 mm

What is the diameter of the intramural part of the fallopian tube?

5-8 mm diameter; 6-8 cm length

What are the diameter and length of the ampulla part of the fallopian tubes?

8-9 cm

What is the approximate length of the vagina?

97%

What percentage of male newborns have testes present in the scrotum before birth?

What is the approximate size of the bulbourethral glands?

Secrete mucus, located on the medial surface of the labia minora

What is the function and location of Bartholin's glands?

Blockage of the gland

What is the cause of a Bartholin gland cyst?

Homologous to bulbourethral glands in males

To what structures are the Bartholin glands homologous?

Remnant of mesonephric tubules

What is the epoophoron?

Remnant of mesonephric duct

What is the Gartner duct?

Dominant antral follicle, close to the surface of the ovary, releases egg cell during ovulation

What is the Graafian follicle?

Placental grading system

What is the Grannum classification?

A chromosomal disorder in males in which there is an extra X chromosome

What is Klinefelter Syndrome?

Located in the interstitium of the testes, secrete testosterone

Where are Leydig cells located, and what is their function?

Mucus-secreting glands around the urethral opening

What are Littre glands?

Paramesonephric duct

What is the Morgagni, Hydatid of?

Embryonic structure

What is the Müllerian Duct?

Present in testicular Leydig cell tumors

Where are Crystals of Reinke found?

In the female urethra, homologues of the prostatic glands

What are Skene's Glands?

Scale of physical development during puberty based on external primary and secondary sex characteristics

What is the Tanner Scale?

Embryonic structure

What is the Wolffian Duct?

Lack of fusion of paramesonephric ducts

What causes duplication of the uterus?

Extreme form of lack of paramesonephric duct fusion

What is uterus didelphys?

Least severe form of lack of paramesonephric duct fusion

What is uterus arcuatus?

Common anomaly, two horns entering a common vagina

What is uterus bicornis?

Insufficient androgen stimulation

What causes Micropenis?

Splitting of the genital tubercle

What causes Bifid/Double penis?

Atypical appearance; large clitoris or small penis

What is Ambiguous genitalia?

Characteristics of both sexes

What are Hermaphrodites?

Most common cause of sexual ambiguity

What is Congenital adrenal hyperplasia (CAH)?

Lack of androgen receptors or tissue response

What is Androgen insensitivity syndrome (AIS)?

Vagina present, but short/poorly developed

What is Complete androgen insensitivity (CAIS)?

Inability to convert dihydrotestosterone (DHT)

What is 5-alpha-reductase deficiency (5-ARD)?

(XXY) Most common sex chromosome disorder; Nondisjunction of XX homologues

What is Klinefelter syndrome?

(X0) Gonadal dysgenesis, short stature, other anomalies

What is Turner syndrome?

Open passageway allows intestinal loops into scrotum

What causes Congenital inguinal hernia?

Irregular obliteration of passageway, fluid-filled cysts

What causes Hydrocele?

Undescended testes, decreased androgen production

What is Cryptorchidism?

Nodular hyperplasia, centrally situated glands, urinary obstruction

What is Benign Prostatic Hyperplasia (BPH)?

Arises from peripheral glands, may be palpable during digital rectal exam

What is Prostatic Carcinoma?

Blocked duct in Bartholin gland can cause cyst or abscess

What is Bartholin Gland Cyst?

Presence of nodular outpouchings along the fallopian tube

What is Salpingitis Isthmica Nodosa?

Buildup of fluid inside the fallopian tube due to blockage

What is Hydrosalpinx?

Poor arterial inflow or excessive venous leakage in corpora cavernosa/spongiosum

What causes Erectile Dysfunction/Vasculogenic Impotence?

Low cuboidal germinal epithelium

What type of epithelium is found in the ovary?

Simple columnar epithelium

What type of epithelium is found in the oviduct (fallopian tube)?

Cuboidal epithelium

What type of epithelium is found in the tubuli recti & rete testis?

Columnar ciliated alternating with cuboidal non-ciliated

What type of epithelium is found in the ductuli efferentes?

Pseudostratified columnar epithelium

What type of epithelium is found in the epididymis?

Pseudostratified columnar epithelium

What type of epithelium is found in the ductus deferens?

Non-ciliated pseudostratified columnar or cuboidal epithelium

What type of epithelium is found in the seminal vesicle?

Simple cuboidal, columnar, or pseudostratified columnar epithelium

What type of epithelium is found in the prostate gland?

Simple tall cuboidal or columnar epithelium

What type of epithelium is found in the bulbourethral glands?

Tall columnar epithelial cells (endocervical canal)

What type of epithelium is found in the uterine cervix?

Simple columnar epithelium

What type of epithelium is found in the endometrium?

Non-keratinizing stratified squamous epithelium

What type of epithelium is found in the vagina?

Non-keratinizing stratified squamous epithelium

What type of epithelium is found in the vulva?

Cuboidal to transitional epithelium

What type of epithelium is found in the Bartholin Glands?

Endothelium-lined vascular spaces

What is the epithelium of the penile urethra?

Week 3

When does external genitalia development begin?

Mesenchymal cells

Which cells migrate to the cloacal membrane to form cloacal folds?

Genital tubercle

What do cloacal folds fuse to form cranially?

Urethral folds

What do cloacal folds divide into caudally?

Genital swellings

What develops on either side of the urethral folds?

Week 4

When do germ cells migrate from the endoderm lining of the yolk sac to the genital ridges?

Week 6

When do germ cells reach the genital ridges?

Week 8

When do Leydig cells begin producing testosterone?