USMLE step 1 Review Anatomy of Reproductive System 2018

1. USMLE® Step I
Review Anatomy of
Reproductive System
TanatTabtieang, MD
Fellowship of the Royal College of Radiologists ofThailand
Lecturer, Department of Anatomy
Faculty of Medicine, Chulalongkorn University
Bangkok,Thailand
Tanat.T@chula.ac.th

2. Reproductive System
• Embryology of reproductive system
• Pelvis and perineum
• Male reproductive organs (Gross + Histology)
• Spermatogenesis
• Female reproductive organs (Gross + Histology)
• Folliculogenesis and ovulation

3. Embryology of reproductive system
• Paramesonephric (Müllerian) duct
– Female internal organs
– Fallopian tubes, uterus, and upper portion of
vagina (lower portion from urogenital sinus)
– Müllerian duct abnormalities: 1° amenorrhea in
females with fully developed 2° sexual
characteristics
• Mesonephric (Wolffian) duct
– Male internal organs (except prostate)
– Epididymis, ductus deferens, seminal vesicles,
and ejaculatory duct
• Gubernaculum
– Male: anchors testes within scrotum
– Female: ovarian ligament + round ligament of
uterus.

4. Embryology of reproductive system
• Female
– Mesonephric (Wolffian) duct degenerates
– Paramesonephric (Müllerian) duct develops
• Male
– Y-chromosome
• Sex-determinating region ofY-chromosome (SRY) gene →TDF
• 7th week of gestation
– Sertoli cells: secrete Mullerian inhibitory factor (MIF) → regression of Müllerian duct
– Leydig cells: secrete androgen → development of mesonephric (Wolffian) duct
No Sertoli cells or lack of MIF: develop
both male and female internal
genitalia and male external genitalia
5α-reductase deficiency:
inability to convert testosterone
into DHT:
male internal genitalia, ambiguous
external genitalia until puberty
(when ↑ testosterone levels cause
masculinization)

5. Embryology of reproductive system
Adult Female Indifferent Embryo Adult Male
Ovary, follicles,
rete ovarii Gonads
Testes, seminiferous
tubules,
rete testes
Uterine tubes, uterus,
cervix, and upper part of
vagina
Paramesonephric
(Müllerian) ducts
Appendix of testes
Duct of Gartner
Mesonephric
(Wolffian) ducts
Epididymis, ductus
deferens, seminal
vesicle, ejaculatory duct
Clitoris, bulb of vestibule Genital tubercle Glans and body of penis
Greater vestibular
(Bartholin) gland,
Urethral and paraurethral
glands (of Skene)
Urogenital sinus
Bulbourethral (Cowper)
glands,
Prostate gland
Labia minora Urogenital folds Ventral aspect of penis
Labia majora Labioscrotal swellings Scrotum
TDF
MIF
Testosterone
+
+
–
DHT
DHT
DHT
DHT
Estrogen
Estrogen
Estrogen
Estrogen

6. Embryology of reproductive system
• Congenital penile abnormalities
– Hypospadias (more common)
• Abnormal opening of penile urethra on
inferior (ventral) side of penis
• Failure of urethral folds to fuse.
– Epispadias
• Abnormal opening of penile urethra on
superior (dorsal) side of penis
• Fault positioning of genital tubercle

7. Disorders of sexual development
• Turner syndrome (45, XO)
– Short stature, ovarian dysgenesis (streak ovary), shield chest, bicuspid
aortic valve, preductal aortic coarctation, lymphatic defects (result in
webbed neck or cystic hygroma; lymphedema in feet, hands), horseshoe
kidney
– ↓ estrogen → ↑ LH,FSH
• Klinefelter syndrome (47, XXY)
– Testicular atrophy, eunuchoid body shape, tall, long extremities,
gynecomastia, female hair distribution.
– Dysgenesis of seminiferous tubules → ↓ inhibin → ↑ FSH.
– Abnormal Leydig cell function → ↓ testosterone → ↑ LH → ↑ estrogen
• True hermaphroditism (46,XX or 47,XXY)
– Ovotesticular disorder of sex development.
– Presence of both ovary and testicular tissuepresent (ovotestis)
– Ambiguous genitalia.

8. Disorders of sexual development
• Female pseudohermaphroditism (46, XX)
– Ovaries present (no testes),Virilized or ambiguous external genitalia
– Excessive exposure to androgenic steroids during early gestation
(M/C: congenital adrenal hyperplasia (CAH) or exogenous androgens
during pregnancy
• Male pseudohermaphroditism (46, XY)
– Testes present (no ovary), Female or ambiguous external genitalia
– Androgen insensitivity syndrome (testicular feminization)
• Mutation of androgen receptor gene
• Normal-appearing female; female external genitalia with rudimentary vagina
Absent uterus and uterine tube
• Develops testes (often found in labia majora)
– 5α-reductase deficiency
• Inability to convert testosterone to DHT
• Underdevelopment of the penis and emission of sperm (microphallus,
hypospadias, and bifid scrotum) and prostate.
• At puberty, when ↑ testosterone:DHT → virilization of external genitalia

9. Pelvis and perineum
Pelvic diaphragm
• Muscular floor of the pelvis, separates the pelvic cavity from the
perineum
• = Levator ani + coccygeus muscle
Levator ani = Iliococcygeus + Pubococcygeus + Puborectalis muscles

10. Perineum
• Anal triangle
• Urogenital triangle
– Superficial perineal pouch
– Deep perineal pouch

11. Perineum
Superficial perineal pouch Deep perineal pouch
• Crura of penis or clitoris
• Bulb of penis (in the male)
• Bulbs of vestibule (in the female)
• Ischiocavernosus muscle
• Bulbospongiosus muscle
• Superficial transverse perineal m.
• Greater vestibular (Bartholin)
gland (in female only)
• Sphincter urethrae muscle
• Membranous urethra (male),
proximal urethra (female)
• Deep transverse perineal muscle
• Bulbourethral (Cowper) gland (in
the male only)
Superficial perineal pouch Deep perineal pouch♂ ♀
♂ ♀

12. Perineum
• Prolapse of pelvic viscera
– Disruption or perineal body
– Loss support of the pelvic viscera, linking
muscles that extend across the pelvic
outlet
– Prolapse of the uterus and vagina
(through the vaginal orifice)
– Cystocele: prolapse of the bladder
(through the urethra)
– Enterocele, Rectocele: prolapse of bowel
and rectum
• Pudendal nerve block
– Relieve perineal pain during childbirth
– Pudendal nerve crosses the lateral aspect
of the sacrospinous ligament, near its
attachment to the ischial spine.

13. Pudendal
nerve (S2-4)
Inferior rectal
nerve
(in ischiorectal
fossa)
Perineal nerve
(in UG triangle)
Dorsal nerve of
penis/clitoris
(in deep perineal
pouch)
Pudendal canal
Pudendal nerve

15. Male reproductive organs
Seminiferous tubules → Epididymis
→Vas deferens → Ejaculatory ducts
→ Urethra → Penis

16. Superficial perineal fascia
• Superficial fatty layer << cont'
with Camper fascia
• Membranous layer (Colles
fascia) << cont' with Scarpa
fascia & Dartos fascia
Deep perineal (Gallaudet) fascia
<< cont' with deep fascia of penis
(Buck‘s fascia)

17. Rupture of Urethra in Males
• Rupture membranous urethra
– Fractures of the pelvic girdle
– Extravasation of urine and blood into
the deep perineal pouch
– Pass superiorly through the urogenital
hiatus → extraperitoneal around the
prostate and bladder
• Rupture spongy urethra
– Injury to the bulb of the penis
– Extravasation of urine from the urethra
→ superficial perineal space
– Pass through scrotum, penis, anterior
abdominal wall in the plane deep to
Scarpa fascia.

18. Male reproductive organs
• Undescended testes (cryptorchidism)
– Testes fail to descend into the scrotum.
– May be found in the abdominal cavity or in the inguinal canal
• Hydrocele of the testes
– Small patency of the processus vaginalis
remains → peritoneal fluid can flow into
the processus vaginalis
• Male sterilization
– Vasectomy
– Ligate and excise part of vas deferens
through an incision in the superior part
of the scrotum

19. Male reproductive organs
• Benign prostatic hyperplasia (BPH)
– Men > 50 years of age
– Enlargement of transitional zone
(periurethral or lateral & middle
lobes) of prostate gland, compress
urethra
– Frequent urination, nocturia,
difficult start and stop stream of
urine, dysuria, urinary retention, UTI,
↑ PSA
• Prostatic adenocarcinoma
– Men > 50 years of age
– Posterior lobe (peripheral zone)
– Hard nodule, asymmetry, ↑ PSA
• Prostatitis
– Dysuria, frequency, urgency

20. Gonadal blood supplies and drainage
• Venous drainage
– Left ovary/testis → Left gonadal vein → left renal vein → IVC.
– Right ovary/testis → right gonadal vein → IVC
• Lymphatic drainage
– Ovaries/testes → para-aortic lymph nodes.
– Distal vagina/vulva/scrotum → superficial inguinal nodes.
– Proximal vagina/uterus → obturator, external iliac and hypogastric nodes
• Arterial supplies
– Testes/ovaries
• Testicular/ovarian arteries from abdominal aorta
– Vulva/penis/scrotum
• Femoral artery → external pudendal artery
• Internal pudendal artery → perineal artery

21. Testis and spermatogenesis
• Tunica albuginea: dense fibrous capsule
• Seminiferous tubule
– Spermatogenic cells
– Sertoli cells: tall columnar epith. Cell
• Support, protect, provide nutrition, blood-testis barrier
• Secrete antigen-binding protein, inhibin, MIF
• Leydig cells: synthesize testosterone
n, haploid
n, haploid
Mitosis
Through blood-testis barrier
2n, diploid

22. Histology of male reproductive organs
Organs Characteristics
Rete testis • Simple cuboidal or low columnar with single cilia and few short
microvilli
Efferent ductules • Pseudostratified columnar with cilia & microvilli
• Thin band of smooth muscle
Epididymis • Pseudostratified columnar epithelium with stereocilia (tall microvilli)
Vas deferens • Pseudostratified columnar epithelium with stereocilia (tall microvilli)
• Thick layer of smooth muscle
Seminal vesicles • Folded mucosa, pseudostratified columnar epithelium
• Produce a secretion rich in spermatozoa-activating substances
Prostate gland • Branched tubuloalveolar glands
• Pseudostratified columnar glandular epithelium and numerous
secretory granules
• Produce secretion include acid phosphatase, citric acid, fibrinolysin,
and other proteins

23. Female reproductive organs

24. Ligaments Connection
Suspensory
ligament of the
ovaries
Ovaries to lateral
pelvic wall
• Contains ovarian vessels
• Ligate vessels during oophorectomy
Cardinal ligament Cervix to side wall of pelvis • Contains uterine vessels
• Ureter coarse under uterine vessels
• Ureter at risk of injury during ligation in
hysterectomy.
Round ligament
of the uterus
Uterine fundus to labia majora • Derivative of gubernaculum
• Travels through inguinal canal
Broad ligament Uterus, fallopian tubes, and
ovaries to pelvic side wall
• Mesosalpinx, mesometrium, and
mesovarium
Ovarian ligament Ovary to
lateral uterus
• Derivative of gubernaculum.

25. Histology of female reproductive organs
Organs Characteristics
Ovary, outer surface • Simple cuboidal epithelium (germinal epithelium covering surface
of ovary)
Fallopian tube • Simple columnar epithelium, many ciliated cells, a few secretory
(peg) cells
• Numerous longitudinal mucosal folds (most in ampulla)
• Ectopic pregnancy: M/C at wall of ampulla
Uterus • Endometrium: functional layer and basal layer
• Simple columnar epithelium with long tubular glands
• Myometrium: bundles of smooth muscle fibers
Endocervix • Simple columnar epithelium
Ectocervix • Stratified squamous epithelium, nonkeratinized
Transformation zone • Squamocolumnar junction (most common area for cervical cancer)
Vagina • Stratified squamous epithelium, nonkeratinized
• No gland

26. Ovary, folliculogenesis and ovulation
arrest in prophase I
arrest in metaphase II
2n, diploid
n, haploid
Complete meiosis I
prior to ovulation
Birth
At puberty
Oogonium: Mitosis
Begin meiosis I
during fetus
Primary follicle
Growing follicle
Resume meiosis II
after fertilization
Ovulation
Primodial follicle
2n, diploid

27. Menstrual cycle
• Proliferative (follicular) phase (day 5-14)
– Estrogen (mature follicle)
– Uterine endometrium proliferates
– Epithelium proliferates, reconstitute glands
– Stroma secrete collagen & ground substance
– Gland: narrow lumen, straight
• Ovulation (day 15)
– LH surge
– Cervical mucous increased and thinned
• Secretory (luteal) phase (day 15-28)
– Progesterone & estrogen (corpus luteum)
– Gland enlarge, corkscrew shape + lumen
dilated with secretory product
– Lengthen artery + coil
• Menstrual phase (day 1-4)
– Arterial contract → ischemia
– Disruption of surface
– Rupture of blood vessels

28. References
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guide. NewYork: McGraw-Hill Medical, 2014.
• Moore, Keith L., Arthur F. Dalley, and A. M. R. Agur. Clinically
oriented anatomy. Philadelphia: Wolters Kluwer Health/Lippincott
Williams & Wilkins, 2014.
• White, James, and David Seiden. USMLE® step 1 lecture notes 2016
: anatomy. NewYork: Kaplan Medical, 2016.
• Netter, Frank H. Atlas of human anatomy. Philadelphia, PA:
Saunders/Elsevier, 2014.
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