Urogenital system embryology

Question 1

Which structure gives rise to the urinary system?

Where does it develop from?

Answer 1

nephrogenic cord

develops from urogenital ridge (intermediate mesoderm)

Question 2

1 - 5

Another name for #4.

Answer 2

1) liver primordium
2) pronephros
3) nephrogenic cord
4) mesonephric duct (WOLFFIAN)
5) mesonephric tubules

Question 3

6 - 11

Answer 3

6) ureteric bud
7) cloaca
8) allantois
9) omphalomesenteric duct
10) mesonephros
11) metanephros

Question 4

1 - 5

Another name for #5.

Answer 4

1) intraembryonic coelom
2) extraembryonic coelom
3) yolk sac
4) midgut
5) mesonephric duct (WOLFFIAN)

Question 5

6 - 11

Answer 5

6) nephrogenic cord
7) urogenital ridge
8) dorsal aorta
9) notochord
10) neural tube
11) dev. spinal ganglion

Question 6

What are the 3 primordial kidney sets?

Give some brief information.

In which segments of the vertebral column are they located?

Answer 6

pronephroi C6 - Th2

• transitory, non-functional
• pronephric duct opens into cloaca

mesonephroi Th2 - L3

• functional, interim kidneys
• consist of glomeruli + mesonephric tubules
• pronephric duct becomes mesonephric duct

metaneprohoi L3 - L5

• delevop from ureteric bud + metanephrogenic blastema
• form adult kidneys, ureter

Question 7

How do kidneys/ureters develop?

Acronym?

Answer 7

• *P** M Se B Bl
• *U** T Ne A

1. Pronephroi + pronephric duct develop
2. Mesonephroi develop, take over pronephric duct
3. urine Secretion starts into amnion as nephrons are developed
4. ureteric Bud develops from mesonephric duct
5. metanephrogenic Blastema develops from caudal part of nephrogenic cord
6. stalk of ureteric bud becomes Ureter
7. collecting Tubules form from ureteric bud
8. Nephrons develop from ureteric bud + metanephrogenic blastema
9. Ascent of kidneys

Question 8

1 - 5

Another name for #1.

Answer 8

1) mesonephric duct (WOLFFIAN)
2) stalk of ureteric bud
3) ureteric bud
4) metanephrogenic blastema
5) ureter

Question 9

6 - 10

Answer 9

6) major calyx
7) renal pelvis
8) minor calyx
9) ureter
10) lobe of kidney

Question 10

11 - 13

What do #11 eventually form?

Answer 10

11) mesenchymal cell clusters → metanephric vesicles
12) straight collecting tubule
13) arched collecting tubule

Question 11

1 - 5

Another name for #4.

Which structures are eventually formed by #5?

Answer 11

4, #5 could also be mesonephric …, but here we are talking abt the development of

1) dorsal aorta
2) urogenital ridge
3) metanephric vesicle
4) mesonephric duct (WOLFFIAN)
5) metanephric tubule → prox./dist. convoluted tubule + loop of HENLE

nephrons in the permanent kidney,
thus metanephros

Question 12

6 - 10

Answer 12

6) afferent glomerular vessel
7) glomerulus
8) dev. Bowman’s capsule
9) afferent + efferent glomerular vessels
10) primordium of gonad (testis/ovary)

_{#4, #5 could also be mesonephric …, but here we are talking abt the development of nephrons in the permanent kidney, thus metanephros}

Question 13

What happens to the lobes of the kidney (cf. development of permanent kidney)?

Answer 13

disappear at age 1

Question 14

What is reciprocal induction?

Answer 14

ureteric bud induces development of nephrons from metanephrogenic blatesma

metanephrogenic blatesma induces branching of ureteric bud

Question 15

What is the reason for the ascent of the kidneys?

When does it stop?

What are its consequences?

Answer 15

caudal growth of embryos body → ascent → stops when kidneys come in contact with suprarenal glands

​consequences:

• hilum comes to lie in final position
• initially supplied by a. iliaca communis
• finally supplied by aorta pars abdominalis

Question 16

How does the urinary bladder develop?

Answer 16

1. allantois constricts → urachus
2. vesical part of urogenital sinus enlarges
3. mesonephric ducts (ureters) are incorporated as trigonum vesicae

Question 17

What is the remnant of the urachus?

Answer 17

lig. umbilicale medianum

Question 18

1 - 5

Another name for #5.

_{the yellow indicated ureter should actually be purple since it derives from the Wolffian duct}

Answer 18

1) vesical part of UG sinus
2) pelvic part of UG sinus
3) phallic part of UG sinus
4) urogenital sinus
5) mesonephric duct (WOLFFIAN)

Question 19

6 - 10

_{the yellow indicated ureter should actually be purple since it derives from the Wolffian duct}

Answer 19

6) ureteric bud
7) urorectal septum
8) cloacal membrane
9) rectum
10) genital tubercle

Question 20

11 - 15

_{the yellow indicated ureter should actually be purple since it derives from the Wolffian duct}

Answer 20

11) urachus
12) kidney
13) uterine tube
14) ovary
15) vas deferens

Question 21

16 - 20

_{the yellow indicated ureter should actually be purple since it derives from the Wolffian duct}

Answer 21

16) testis
17) vagina
18) clitoris
19) penis
20) spongy urethra

Question 22

21 - 23

_{the yellow indicated ureter should actually be purple since it derives from the Wolffian duct}

Answer 22

21) urethra
22) urinary bladder
23) uterus

Question 23

How does the location of the urinary bladder change after birth?

Answer 23

orginally in the abdomen → enters greater pelvis (∽ 6y) → enters lesser pelvis (∽ puberty)

Question 24

Where does the urethra develop from?

Differentiate btw male/female.

Answer 24

• female: entire epithelium of urethra from urogenital sinus
• male: epithelium of urethra from urogenital sinus btw urethral folds
  BUT: in glans from surface ectoderm

⇒ both: conn. tissue/mm. from surr. splanchnic mesenchyme

explains transition of urothelium to pseudostrat. col. to str. squ. non-ker. (only in males!!)

Question 25

#1 - 6 Where does #1 originate from? Another name for #5 and #6.

Answer 25

1) primordial germ cells (originate from dorsal mesentery) 2) gut tube 3) gonadal ridge 4) mesonephric tubule 5) mesonephric duct (**WOLFFIAN**) 6) paramesonephric duct (**MÜLLERIAN**) _{here #4 could NOT be meta... instead of meso..., because the development of the gonadal ridge is restricted to the region where the mesonephros grows}

Question 26

#7 - 12

Answer 26

7) aorta 8) dorsal mesentery 9) urogenital ridge 10) gonadal cord 11) medulla of gonad 12) cortex of gonad

Question 27

How do indifferent gonads develop? When do they start to differentiate into testes/ovaries? What does it mean?

Answer 27

indifferent until end of week 6 = **identical in appearance** (both sexes) 1. growing mesonephros produces **gonadal ridge** in urogenital ridge 2. **gonadal cords** grow → cortex/medulla of gonad 3. **primordial germ cells** from dorsal mes. migrate + are incorporated into gonadal cords 4. _in week 7:_ sexual differentiation depends on * **testis-determining factor TDF** → male * **no TDF** → female

Question 28

#1 - 5 Another name for #3 and #4.

Answer 28

1) gut tube 2) mesonephric vesicle 3) mesonephric tube (**WOLFFIAN**) 4) paramesonephric tube (**MÜLLERIAN**) 5) primordial germ cells

Question 29

#6 - 10

Answer 29

6) seminiferous cords 7) mesorchium 8) rete testis 9) septum of testis 10) tunica albuginea

Question 30

List the hormones and cells that are responsible for masculine differentiation (besides TDF).

Answer 30

**human chorionic gonadotropin hCG** induces * _LEYDIG cells → **testosterone​**_⇒ stimulate WOLFFIAN duct to form male genital ducts * _Sertoli cells → **anti-müllerian hormone (AMH)**_ ⇒ stimulates MÜLLERIAN ducts to regress

Question 31

How do testes develop?

Answer 31

_all events induced by TDF_ 1. gonadal cords (now seminiferous cords) pinch off to form **rete testis** 2. **tunica albuginea** forms 3. testis seperate from degenerating mesonephros → suspended by **mesorchium** 4. seminiferous cords become **seminiferous tubules** * mesenchyme btw tubules → **Leydig cells** * seminiferous tubules → **Sertoli cells** 5. surface epithelium of testes flattens → **tunica vaginalis testis** 6. rete testis and mesonephric tubules fuse → **efferent ductules**

Question 32

#1 - 6 Another name for #5.

Answer 32

1) gut tube 2) cortical cords 3) former gonadal cords 4) rete ovarii 5) paramesonephric duct (**MÜLLERIAN**) 6) mesovarium

Question 33

#7 - 12 Another name for #9 and #12.

Answer 33

7) surface epithelium 8) prim. germ cells 9) mesonephric duct (**WOLFFIAN**) + vesicle 10) degenerating rete ovarii 11) uterine tube 12) prim. ovarian follicles (= **oogonia**)

Question 34

How do the ovaries develop?

Answer 34

_all events induced by absence of TDF_ 1. ovary seperate degenerating mesonephros → suspended by **mesovarium** 2. gonadal cords seperate → **rete ovarii** 3. **cortical cords** form from mesothelium of peritoneum 4. **primordial germ cells** incorporated into cortical cords 5. cortical cords containing a germ cell break up → form primordial follicle (= **oogonium**) → active mitosis of oogonia → become primary oocytes after birth 6. surface epithelium flattens → forms **tunica albuginea** that seperates follicles from cortex

Question 35

Where do the MÜLLERIAN ducts develop from? Which transitional structures are formed by them in females?

Answer 35

_develop from mesothelium lateral to mesonephroi_ open from peritoneal cavity into future pelvic region *_in females:_* fuse caudally → form **uterovaginal primordium** → produces **sinus tubercle** on urogenital sinus

Question 36

How do epididymis and its accompanied structures develop?

Answer 36

* _distal end of Wolffian duct_ * **appendix edididymis** * convolutes → **epididymis** * **vas deferens** when invested w/ sm. m. * **ductus ejaculatorius** * _mesonephric tubules_ (originally from metan. blastema) * **efferent tubules** * **paradidymis**

Question 37

Where does the uterus develop from?

Answer 37

**uterovaginal primordium +** surr. **splanchnic mesenchyme** (→ endometrial stroma + myometrium)

Question 38

Which structures form lig. latum? Which other structures are formed during that proc.?

Answer 38

_fusion of MÜLLERIAN ducts_ → lig. latum + mesenchyme proliferates → **parametrium**

Question 39

Where do accessory sex glands in males and females develop from?

Answer 39

_mostly derived from endoderm of UG sinus at parts of urethra_ **_male:_** * prost. part of urethra **→ prostate** * spongy part of urethra → **Cowper gll.** * **BUT:** Wolffian duct → **gl. vesiculosa** **​_females:_** * **urethral + paraurethral gll.** * **maj. vestibular gll.**

Question 40

How does the vagina develop?

Answer 40

1. sinus tubercle forms laterally **sinovaginal bulbs** 2. sinovaginal bulbs fuse → **vaginal plate** 3. central parts break down → **lumen** → **hymen** develops as only remnant of sinus tubercle

Question 41

Describe the indifferent part of the development of external genetalia.

Answer 41

_mesenchyme produces **genital tubercle**_ * *→ labioscrotal folds** (lateral) * *→ urethral folds** (medial), surround UG sinus

Question 42

How do the male external genetalia develop?

Answer 42

1. as genital tubercle elongates → phallus 2. urethral folds approach each other → **spongy urethra** 3. at glans penis ectodermal ingrowth meets spongy urethra → **external urethral orifice** formed 4. ectoderm around glans → **preputium** 5. **corpora cav./spong.** formed by mesenchyme 6. **labioscrotal folds** fuse → scrotum + raphe scroti

Question 43

How do the female external genetalia develop?

Answer 43

1. instead of phallus **clitoris** formed from genital tubercle 2. **urethral folds** * fuse posteriorly → frenulum of labia majora * unfused → labia minora 3. **labioscrotal folds** * fuse post./ant. → labial commissurae + mons pubis * unfused → labia majora

Question 44

What is the gubernaculum, what does it do and what are its derivatives?

Answer 44

**outgrowth from caudal pole of gonad into labioscrotal folds** → forms path for processus vaginalis → inguinal canal _derivatives:_ * *in males:* gubernaculum testis * *in females:* lig. ovarii prop., lig. teres uteri

Question 45

What are the deep and superficial inguinal ring?

Answer 45

openings produced by gubernaculum * *deep:* in **transversalis fascia** * *superficial:* in **external oblique aponeurosis**

Question 46

What are causes and consequences of the descent of the testes?

Answer 46

_causes:_ * growing pelvis + deg. mesonephroi * increased intraabdominal pressure due to growing abd. viscera _consequences:_ * **ureter crossing w/ ductus deferens** * **course of test. vessels** * **coats of testes**

Question 47

In what way does the descent of the ovaries differ from that of testes?

Answer 47

**do not pass from pelvis to enter inguinal canal** ​proc. vaginalis disappears, _BUT_ sometimes persistent as **canal of NUCK**

Question 48

What are the derivatives of the Wolffian duct in males?

Answer 48

* appendix + duct of epididymis * ductus deferens * ejaculatory duct + seminal gland _in both:_ * ureter + trigonum vesicae * renal pelvis, calices + collecting tubules

Question 49

What are the derivatives of the Wolffian duct in females?

Answer 49

* appendix vesiculosa * duct of epophoron * longitudinal duct; Gartner duct _in both:_ * ureter + trigonum vesicae * renal pelvis, calices + collecting tubules

Question 50

What are the derivatives of the Müllerian duct in males?

Answer 50

* appendix of **testis**

Question 51

What are the derivatives of the Müllerian duct in females?

Answer 51

* hydatid of Morgangni (= paratubal cyst at infundibulum of uterine tube) * uterine tube * uterus

Question 52

What are the derivatives of the mesonephric tubules in males/females?

Answer 52

_male:_ * efferent ductules of testis * paradidymis _female:_ * epoophoron (like paraophoron, but more cranial) * paraophoron (btw ovary + uterus)