Download Development of the Urogenital System

Urogenital system
陳建榮
http://web.nchu.edu.tw/pweb/users/chenjr/
Development of Urogenital System
Adrenal Glands
Kidneys
The development of the kidneys from the
pronephros to their ascent to the level of L1.
Reproductive System
The development of male and female genitalia from
the partitioning of the cloaca to the final differentiated
state.
Embryology of the urogenital system
-Urinary system
-Genital system
Urogenital ridge (intermediate mesoderm) along the
posterior abdominal wall
-- urinary system  nephrogenic cord生腎索
-- genital system  gonadal ridge生殖脊
Kidney develops first (functional; reproductive later)
Urinary system
Genital system
Normal Development of the Adrenal Glands
Formation of the adrenal cortex
The adrenal glands is derived from the intermediate
mesoderm. The adrenal glands have two developmentally distinct
parts: the medulla and the cortex.
Formation of the adrenal medulla
Development of zones of adrenal gland
球小帶
(Aldosterone )
束狀帶
(Glucocorticoids )
網狀帶
(DHEA)
6th weeks
Normal Development of the Adrenal Glands
Formation of the adrenal cortex
Formation of the adrenal medulla
Neural crest cells migrate into the center of this aggregate to
develop the adrenal medulla. The cells differentiate into sympathetic
nerve cells and show evidence of catecholamine production in
10th week of fetal life.
Development of zones of adrenal gland
Normal Development of the Adrenal Glands
Formation of the adrenal cortex
Formation of the adrenal medulla
Development of zones of adrenal gland
-During fetal period
-zona glomerulus球小帶
-zona fasciculata束狀帶
-3 years old
-zona reticularis網狀帶forms
-The fetal adrenal glands are larger than the fetal
kidney at four months. Even at birth they are relatively
quite large (about 20 times their relative size in the adult).
-After birth, the fetal cortex rapidly undergoes regression.
2
1
3
Congenital adrenal hyperplasia (CAH)
先天性腎上腺增生症
Normal Development of the Urinary System
Development of kidney
Early kidney development (pronephros)
Development of mesonephros
Development of metanephros
Ascent of the kidneys
Development of the Urinary Bladder
Normal Development of the Kidneys
Pronephros: 原腎(4th week, nonfunctional)
-mesenchymal cell aggregates in neck region of embryo, and soon transformed into
ligament
-pronephros attached to pronephric ducts原腎管
-promesonephric ducts used in next stage of kidney development, these ducts end in
the cloacal region caudal to the mesenchymal cell aggregates of the pronephros.
Mesonephros:
Metanephros:
Normal Development of the Kidneys
Pronephros: (4th week, nonfunctional)
Mesonephros: 中腎(functional)
-mesonephros begins development late in 4th week lie caudal to
pronephros
-mesonephros consists of glomeruli and mesonephric tubules中腎小管
which open into mesonephric duct, a continuation of the pronephric duct
mesonephric duct opens into cloaca
-mesonephros proper degenerates but tubules and ducts have derivatives in
adult males (tubules form ductuli efferentes輸出小管 and ducts form a
number of reproductive structures to be discussed later).
Metanephros:
Development of the Metanephros後腎:
-The ureteric bud forms from an outgrowth of the mesonephric duct near the
cloaca. The ureter, renal pelvis, major and minor calyces, collecting ducts
and collecting tubules are all formed from the ureteric bud.
-The metanephric mesenchyme forms from the caudal portion of the
intermediate mass, and it surrounds the end of the ureteric bud.
-As the kidney grows the ureteric bud forms finger-like projections.
-The first 4 generations of the projections form the major calyx, the next 2
generations form the minor calyces, and the remaining projections form the
straight and arched collecting tubules.
腎盂
Normal development of Nephrons
-The arched collecting tubules induce
growth of the surrounding mesenchyme,
which forms a tubule in the metanephric
mass後腎原基 of mesoderm.
-These tubules form the parts of the
nephron: glomerulus, Bowman's capsule,
convoluted tubule, loop of Henle.
-Formation of the nephrons of the
permanent kidney begins at 8th week.
-The metanephric vesicles elongate to form
tubules which directly contact the arched
collecting tubules.
-The metanephric tubules are lobulated and
remain this way until after birth.
Normal Development of the Urinary System
Development of kidney
Early kidney development (pronephros)
Development of mesonephros
Development of metanephros
Ascent of the kidneys
Development of the Urinary Bladder
Ascent of the kidneys
-During the 5th and 6th weeks of development, the
mature kidneys lie in the pelvis with their hila pointed
anteriorly.
-As the pelvis and abdomen grow, the kidneys slowly
move upward.
-By the 7th week, the hilum points medially and the
kidneys are located in the abdomen.
-As the embryo continues to grow in a caudal direction,
the kidneys come to lie in a retroperitoneal position at
the level of L1 by the 9th week of development.
Clinical problems
Accessory renal arteries
Renal agenesis
Bilateral renal agenesis
Malrotated kidney
Ectopic kidney
Duplication of urinary tract
Ectopic ureter
Duplication of urinary tract
Horseshoe kidney
Development of Urinary Bladder
-Cloaca (uro-rectal septum尿生殖隔)
-urogenital sinus泌尿生殖竇
-Anorectal canal肛門生殖管
-The uro-genital sinus may be divided into three
component parts.
-The cranial portion which is continuous with the
allantois and forms the bladder proper.
-The pelvic part of the sinus forms the prostatic
urethra and epithelium as well as the membranous
urethra and bulbo urethral glands in the male and
the membranous urethra and part of the vagina in
females.
-The caudal portion, or definitive uro-genital sinus,
forms the penile urethra in males and the vestibule
in females.
-The trigone portion is formed by the caudal
ends of the mesonephric ducts.
-The mesonephric ducts begin to become
incorporated into the wall of the bladder
dragging the ureters along with them.
-The mesonephric ducts enter the prostatic
part of the urethra.
-In females, the ducts then degenerate. In
males, the ducts form the origin of the
ejaculatory
ducts.
-The bladder is initially
continuous with the
allantois.
-Over time, the allantois
degenerates to form a
cord-like structure, the
urachus.
-The urachus goes from
the umbilicus to the apex
of the bladder and forms
the median umbilical
ligament which can be
seen in adults.
Clinical problems
Urachal anomalies
Extrophy of bladder膀胱外翻
Normal development of Reproductive System
Bipotential Phase
Early Development (pre-differentiation)
Partitioning of the Cloaca
Male Development
Development of the Testes
Development of External Genitalia
Female Development
Development of the Ovaries
Development of the Vagina
Development of External Genitalia
Summary of Derivatives of Embryonic Structures
• The chromosomal & genetic sex of an embryo
is determined at fertilization by the kind of
sperm that fertilizes the ovum.
• Male & female characteristics begin to
develop at the 7th week.
• The early genital system in the two sexes are
similar  the initial period of genital
development is called indifferent stage of
sexual development.
Early Genital System Development
-Early in the 4th week, the primordial germ cells may be seen in the endoderm
around the allantois.
-These germ cells migrate under the coelomic epithelium, around the gut to
the dorsal mesentery.
Regulation of germ cell
migration
有無不孕症 可能娘胎就決定
2015-06-05 02:48:35 聯合報 記者陳皓嬿、黃筱雅、陳雨鑫／綜
合報導
Indifferent Gonads
• It is the Initial stage in 5th week  thickened area of
mesothelium develops on the medial side of the
mesonephros  proliferation  form a bulge on the
medial side (Gonadal (genital) ridge).
• Primary sex cord初級性索 ( fingerlike epithelial cords)
 grow into the underlying mesenchyme.
• The indifferent gonad consists of an external cortex
and internal medulla
• In femalethe cortex of indifferent gonads form
the ovary & the medulla regress.
• In male the medulla  form the testis & cortex
regress except for vestigial remnants. (SRY)
Development of the Gonads
(Testes & Ovary)
 The gonads (testes & ovary) are derived
from 3 sources:
1) The mesodermal epithelium lining the posterior
abdominal wall.
2) The underlying mesenchyme.
3) The primordial germ cells.
Nephorgenic cord:
-Mesonephric duct
-epidydimis; ductus deferen
-Paramesonephric duct
-uterine tube; uterus
Partitioning of Cloaca
Internal structure
-The caudal end of the hindgut is lined with endoderm and is known as
the cloaca泄殖腔.
-At the end of the cloaca, the there is a cloacal membrane泄殖膜 which
separates the endoderm from the surface ectoderm.
-The uro-rectal septum泌尿直腸膈 migrates caudally to divide
the cloaca into dorsal and ventral aspects.
-On the ventral side, attaching to the allantois is the primitive urogenital sinus泌尿生殖竇. The primitive ano-rectal canal肛門直腸管
lies dorsally.
-As the division is completed, at 7th weeks, the cloacal membrane
is also divided into uro-genital membrane泌尿生殖膜and anal
membrane肛門直腸膜.
Urogenital sinus
Ano-rectal canal
Partitioning of Cloaca
External structure
-As the urogenital septum is migrating caudally, the intermediate
masses are also proliferating.
-These mesodermal masses form a genital tubercle生殖結節 at
the ventral tip of the cloacal membrane.
-Labioscrotal swellings陰唇陰囊隆起 and urogenital folds泌尿生
殖褶develop shortly thereafter on each side of the cloacal
membrane.
-When the urogenital septum reaches the cloacal membrane,
dividing it into anal membrane and urogenital membrane.
-The embryo is still in its bipotential phase at this point and has
the potential to develop either male or female external genitalia.
Normal development of Reproductive System
Bipotential Phase
Early Development (pre-differentiation)
Partitioning of the Cloaca
Male Development
Development of the Testes
Development of External Genitalia
Female Development
Development of the Ovaries
Development of the Vagina
Development of External Genitalia
Summary of Derivatives of Embryonic Structures
Development of Testes
-Embryos which contain the Y chromosome have a specific gene known as
SRY(sex-determining region Y gene, testis-determining factor, TDF ).
-SRY is expressed in the mesenchyme and cause a cascade of events leading to
the formation of internal male organs.
-The first step in the development of the testes is the formation of the tunica
albuginea白膜, a layer of fibrous connective tissue which separates the sex cords
(seminiferous cords精索) from the surface epithelium.
-Within the tunica albuginea, the seminiferous cords are separated from one
another by mesenchyme.
-The mesenchyme  Leydig cells.
7th week
-Leydig cells produce testosterone to promot the mesonephric duct.
-The renal corpuscle is degenerating, which allows the tubules of the
mesonephros to hook up to the rete testis睪丸網  ductuli efferentes輸出管.
-These tubules are continuous with the mesonephric duct, which is now
known as the epididymis副睪.
-The seminiferous cords are solid (i.e. no lumen) until puberty
but they are made up of a large number of Sertoli cells, a highly
proliferative cell which secretes antimullerian hormone (AMH).
-AMH inhibits the paramesonephric ducts副中腎管 which then
degenerate around the 9th week of development.
-The seminiferous cords remain solid until puberty at which
time a lumen develops and they become the seminiferous
tubules.
Development of Genital Ducts
•
Both male & female embryos have 2 pairs of
genital ducts:
1) The mesonephric (wolffian) ducts中腎管 
important in the development of the male
reproductive system.
2) The paramesonephric ( mullerian) ducts副中腎
管  important in female reproductive system.
• In indifferent stage of the genital system  the
male & female genital ducts are present.
The Mesonephric ducts中腎管
• These ducts drain urine from the mesonephric kidney.
• Also, under the influence of testosterone, the proximal
part of each mesonephric duct become convoluted to
form the epididymis.
• Müllerian inhibiting substance (AMH/MIS) causes
the paramesonephric ducts to disappear by epithelial
mesenchymal transformed.
• The remainder of mesonephric duct forms the ductus
deferens輸精管 & ejaculatory duct射精管.
• In Female  the mesonephric ducts are completely
disappear, only a few non-functional remnant persist.
• Prostate前列腺: multiple endodermal
outgrowths arise from the prostatic part of the
urethra & grow into the surrounding
mesenchyme.
• Bulbourethral glands尿道球腺: pea-sized
structures develop from paired outgrowths
form the spongy part of the urethra. The
secretions of these glands contribute to the
semen.
Development of Male External Genitalia
-Testosterone  male external genitalia
-Genital tubercle生殖結節  penis
-Urogenital folds泌尿生殖褶  urethral groove尿道溝.
-The urogenital folds fuse together on the ventral side of the developing penis,
enclosing what will now become the spongy urethra.
-The foreskin is formed in the
12th week of development.
-A septum of ectoderm moves
inward around the edges of the
penis and then breaks down,
leaving a thin layer of skin
surrounding the penis.
-During this time, the penis is
also developing its corpus
cavernosa and spongiosa from
proliferating mesenchyme within
the genital tubercle.
Clinical problems
Glandular hypospadia
Normal development of Reproductive System
Bipotential Phase
Early Development (pre-differentiation)
Partitioning of the Cloaca
Male Development
Development of the Testes
Development of External Genitalia
Female Development
Development of the Ovaries
Development of the Vagina
Development of External Genitalia
Summary of Derivatives of Embryonic Structures
Development of the Ovaries
-In the absence of SRY/TDF, the primary sex cords are not nearly so welldeveloped as in the male embryo.
-The cortex is much better developed and it forms secondary sex cords that
extend from the surface epithelium to the mesenchyme.
Development of the Vagina
-The paramesonephric ducts develop in the female because of a lack of antimullerian hormone (AMH).
-These paramesonephric ducts form the majority of the female reproductive tract.
-The fallopian tubes develop from the upper unfused portions of the ducts while the
lower fused portion of the ducts forms a uterovaginal primordium which gives rise to
the uterus and vagina.
-The sinovaginal bulbs竇陰道球 form when the uterovaginal primordium子宮陰道原基
contacts the urogenital sinus.
子宮陰道原基
竇陰道球
Clinical problems
Clinical problems
Pseudohermaphrodite假性陰陽人 caused by CAH
Development of Female External Genitalia
Clinical problems
Congenital anomalies of hymen
Vagina ends blindly
Androgen insensitivity syndrome
Pseudohermaphrodite假性陰陽人 caused by androgen insensitivity
Descent of gonads
Descent of the testis
-Gubernaculum引帶
-Proper lig. of testis睪丸固有韌帶
-Lig. of tail of epididymis副睪尾韌帶
-The testis descends through the inguinal canal into the scrotum at the time of birth.
-The testis is then covered by a layer of peritoneum, the visceral layer of the tunica vaginalis
-The remainder of the peritoneal sac forms the parietal layer of the tunica vaginalis鞘膜.
-The canal connecting the lumen of the vaginal process鞘突 with the peritoneal cavity is
obliterated at birth or shortly thereafter.
Descent of the ovary
-The ovaries also descend to their position in the true pelvis.
-Gubernaculum
-ovarian ligament 卵巢固有韌帶
-round ligament of the uterus子宮圓韌帶 (extending to the labia majora).
Clinical problems
Possible site of cryptorchid and ectopic testies
Failure of closure of the processus vaginalis
Reproductive System
Bipotential Phase
Early Development (pre-differentiation)
Partitioning of the Cloaca
Male Development
Development of the Testes
Development of External Genitalia
Female Development
Development of the Ovaries
Development of the Vagina
Development of External Genitalia
Summary of Derivatives of Embryonic Structures
Male
Female
Embryonic Structure
Indifferent gonad
Cortex
Male
Female
ovary
Adult testis
Equivalents of Embryonic Structures
seminiferous tubules
ovarian follicles
Medulla
rete testis
rete ovarii
Gubernaculum
gubernaculum testis
ovarian and round ligament of
uterus
Mesonephric tubules
ductuli efferentes
epoophoron, paroophoron
Mesonephric Duct
appendix of epididymus, duct
of epididymus, ductus deferens,
ureter, calices and collecting
tubules, ejaculatory duct and
seminal vesicles
appendix vesiculosa, duct of
epoophoron, duct of Gartner,
ureter, pelvis, calices and
collecting tubules
Paramesonephric Duct
appendix of testis
hydatid of Morgagni, uterine
tube, uterus
Urogenital Sinus
urinary bladder, urethra,
urinary bladder, urethra,
prostatic utricle, prostate gland vagina, urethral, paraurethral
and bulbourethral glands
and greater vestibular glands
Sinus tubercle
seminal colliculus
hymen
Phallus
penis
clitoris
Urogenital folds
ventral aspect of penis
labia minora
Labioscrotal swellings
Scrotum
labia majora