Chapter 5. Anatomy and Embryology 부산백병원 산부인과 R3 강영미

Chapter 5. Anatomy and Embryology

부산백병원 산부인과R3 강영미

Pelvic Viscera

Embryonic development

Female urinary and genital tract Closely related, anatomically and embryologically Embryologic urinary system ; important inductive influe

nce on developing genital system Anomalies in one system are often mirrored by anomal

ies in another system

Embryonic development

Urinary system, internal reproductive organs and external genitalia Develop synchronously

at an early embryologic age(table 5.6)

Urinary system

Kidney, Renal collecting system, Ureters

Kidney, renal collecting system and ureters from longitudinal mass of mesoderm(nephrogenic cord)

Mesonephric(Wolffian) duct

Singular importance for the following reasons Grows caudally in developing embryo to open an excre

tory channel into the primitive cloaca and outside world

Serves as starting point for development of the metanephros which becomes definitive kidney

Differentiates into the sexual duct system in male Although regressing in female fetuses, inductive role i

n development of the paramesonephric or mullerian duct

Metanephros

Development of metanephros

그림 13-8

Bladder and Urethra

Cloaca

Genital system development

Genital system

In embryologic stage, early genital system Indistinguishable between two sexes Known as “ indifferent stage” of genital development Mesodermal epithelium, mesenchyme and primordial

germ cell

Internal reproductive organs

Primordial germ cells

1. Mullerian duct

Paramesonephric or mullerian ducts Form lateral to mesonephric ducts Grow caudally and then medially to fuse in midline Contact urogenital sinus in region of the post. urethra

at slight thickening known as sinusal tubercle

Male fetus

TDF Results in degeneration of gonadal cortex and differen

tiation of the medullary region of the gonad into Sertoli cells

Sertoli cells Secrete glycoprotein known as anti-mullerian hormone

(AMH) Cause regression of paramesonephric duct system in male e

mbryo Signal for differentiation of Leydig cells from the surrounding

mesenchyme

Male fetus

Leydig cells Produce testosterone,dihydrotestosterone with 5a-red

uctase Testosterone

Responsible for evolution of mesonephric duct system into vas deferens, epididymis, ejaculatory ducts and seminal vesicle

At puberty, leads to spermatogenesis and changes in primary and secondary sex characteristics

DHT Results in development of the male external genitalia and

prostate and bulbourethral glands

Female fetus

In the absence of TDF, medulla regresses and cortical sex cords break up into isolated cell clusters(primordial follicles)

in the absence of AMH & testosterone, Mesonephric duct system degenerates Then, paramesonephric duct system develops

Inf. fused portion Uterovaginal canal -> uterus and upper vagina

Cranial unfused portions Open into celomic cavity(future peritoneal cavity) Fallopian tubes

3. Accessory genital glands

Female accessory genital glands Develop as outgrowths from urethra(paraurethral or Sk

ene) and definitive urogenital sinus(greater vestibular or Bartholin)

Ovaries first develop in the thoracic region, but arrive in pelvis by complicated process of descent This descent by differential growth ; under the control

of a ligamentous cord called the gubernaculum

Genital system ; 3. Accessory genital glands Gubernaculum

External genitalia

Genital system abnormalities

Congenital defects in sexual development, usually arising from a variety of chromosomal abnormalities, tend to present clinically with ambiguous external genitalia

Known as intersex conditions or hermaphroditism Classified according to the histologic appearance of the g

onads

(1) True hermaphroditism

Individuals with true hermaphroditism Have both ovarian and testicular tissue

Most commonly as composite ovotestes Occasionally with an ovary on one side and a testis on the oth

er In the latter case, a fallopian tube and single uterine horn ma

y develop on the side with the ovary

∵ absence of local AMH Extremely rare condition

(2) Pseudohermaphroditism

In individuals with pseudohermaphroditism, Genetic sex indicates one gender External genitalia has characteristics of the other gend

er Caused either by abnormal levels of sex hormones or abn

ormalities in the sex hormone receptors

(2) Pseudohermaphroditism

Males with pseudohermaphroditism Genetic males with feminized external genitalia

Hypospadias(urethral opening on the ventral surface of the penis)

Incomplete fusion of the urogenital or labioscrotal folds ; m/c manifesting sx.

Females with pseudohermaphroditism Genetic females with virilized external genitalia

Clitoral hypertrophy Some degree of fusion of the urogenital or labioscrotal folds

Genital Structures

Vagina

Hollow fibromuscular tube extending from the vulvar vestibule to the uterus In dorsal lithotomy, directed posteriorly toward the sac

rum In upright position, almost horizontal Spaces between the cervix and vagina ; ant, post, and

lateral vaginal fornices Post. vaginal wall ; about 3 cm longer than the a

nt. wall ∵ vagina is attached at a higher point posteriorly than ant

eriorly

Vagina

Post. vaginal wall ; separated from post. cul-de-sac and peritoneal cavity by the vaginal wall and peritoneum

This proximity ; clinically useful Culdocentesis

Intraperitoneal hemorrhage, pus, other intraabdominal fluid Posterior colpotomy

As an adjunct to laparoscopic excision of adnexal masses

Cervix

Endocervical canal About 2-3cm in length, opens proximally into the endometrial cavi

ty at the internal os In early childhood, during pregnancy, or with oral contraceptive use,

Columnar epithelium may extend from the endocervical canal onto the exocervix -> eversion or ectopy

Cervical mucus production Under hormonal influence Around the time of ovulation - profuse, clear, thin In the postovulatory phase of the cycle ; scant and thick mucus

Corpus

At birth, cervix and corpus are about equal in size In adult women, corpus has grown to 2-3 times

the size of the cervix Position ; flexion and version

Flexion - angle between the long axis of the uterine corpus and cervix

Version - angel of the junction of the uterus with the upper vagina

Corpus

Divided into several different regions ; Isthmus or lower uterine segment

The area where the endocervical canal opens into the endometrial cavity

Uterine cornu On each side of the upper uterine body, funnel-shaped area r

eceives the insertion of the fallopian tubes Fundus

Uterus above this area(cornu)

Fallopian tubes

Fallopian tubes and ovaries ; referred to as the adnexa Vary in length from 7 to 12 cm Function

Ovum pickup Provision of physical environment for conception Transport and nourishment of the fertilized ovum

Fallopian tubes

Divided into several regions ; Interstitial

Narrowest portion of the tube, lies within the uterine wall and forms the tubal ostia at the endometrial cavity

Isthmus Narrow segment closest to the uterine wall

Ampulla Larger diameter segment lateral to the isthmus

Fimbria(infundibulum) Funnel-shaped abdominal ostia of the tubes

Ovaries

Paired gonadal structures that lie suspended between the plevic wall and the uterus by the infundibulopelvic ligament laterally and uteroovarian ligament medially

Varies in size with measurements up to 5*3*3cm Consists of a cortex and medulla

Cortex - specialized stroma and follicles Medulla - primarily of fibromuscular tissue and blood vessels

Urinary tract

Ureters

25cm in length Totally retroperitoneal in location Pathway of lower half of each ureter

Traverses the pelvis after crossing the common iliac vessels at their bifurcation, just medial to the ovarian vessels

Descends into the pelvis adherent to the peritoneum of the lateral pelvic wall and the medial leaf of the broad ligament

Enter the bladder base anterior to the upper vagina, traveling obliquely through the bladder wall

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Bladder

divided into two areas ; Base of the bladder

Consists of the urinary trigone posteriorly and a thickened area of detrusor anteriorly

Trigone - two ureteral orifices and opening of the urethra into the bladder

Receives a-adrenergic sympathetic innervation Is the area responsible for maintaining continence

Dome of the bladder Parasympathetic innervation Is responsible for micturition

Urethra

Female urethra ; about 3 to 4 cm in length Extends from the bladder to the vestibule, traveling just a

nterior to the vagina Lined by nonkeratinized squamous epithelium that is res

ponsive to estrogen stimulation Contains as inner longitudinal layer and outer circular lay

er

Abdominal Wall

Abdominal wall

1. Skin 2. Muscles

Five muscles and their aponeuroses(fig 5.16)

3. Fascia ; (1) Superficial fascia

Consists of two layers Camper fascia

Most superficial layer, which contains a variable amount of fat Scarpa fascia

Deeper membranous layer continuous in the perineum with colles fascia(superficial perineal fascia) and with deep fascia of the thigh(fascia lata)

3. Fascia ; (2) Rectus sheath

Aponeuroses of the external and internal oblique and the transversus abdominis

; Combine to form a sheath for the rectus abdominis and pyramidalis, fusing medially in the midline at the linea alba and laterally at the semilunar line(fig 5.16)

3. Fascia ; (3) Transversalis fascia and endopelvic fascia Firm membranous sheet on the internal surface of the tra

nsversus abdominis muscle Like peritoneum, divided into a parietal and a visceral co

mponent Transversalis fascia

Continues along blood vessels and other structures leaving and entering the abdominopelvic cavity

Contributes to the formation of the visceral (endopelvic) pelvic fascia

Pelvic fascia Invests the pelvic organs and attaches them to the pelvic side

walls, thereby playing a critical role in pelvic support

Perineum

Situated at the lower end of the trunk between the buttocks

Its bony boundaries Lower margin of the pubic symphysis anteriorly Tip of the coccyx posteriorly Ischial tuberosities laterally

Diamond shape of the perineum Divided by imaginary line joining the ischial tuberositie

s immediately in front of the anus, at the level of the perineal body, into an ant. urogenital and a post. anal triangle(fig 5.18)