17-00
FemaleReproductive
System17-00 Female Reproductive System

17 Female Reproductive System
Menu 1/2
17-00.

Female Reproductive System

17-19.

Stratum granulosum， theca folliculi interna and externa. Monkey， H-E stain， x 100.

17-01.

Scheme showing the female reproductive System.

17-20.

Corpus rubrum 1. General view. Human， H-E stain， x 1.3.

17-001. Ovary

17-21.

Corpus rubrum 2. Luteinization is less progressed. Human， H-E stain， x 25.

17-02.

Ovary and oviduct. General view. Monkey， H-E stain， x 1.2.

17-22.

Corpus rubrum 3. Luteinization is not progressed. Human， H-E stain， x 160.

17-03.

Overy Sagitall section， general view. Monkey， H-E stain， x 2.0.

17-23.

Corpus rubrum 4. Luteinization is progressed. Human， H-E stain， x 25.

17-04.

Ovary containing a large corpus luteum. Human， H-E stain， x 1.15.

17-24.

Corpus rubrum 5. Luteinization is progressed. Human， H-E stain， x 160.

17-05.

Cortex of ovary. Human， H-E attain， x 25.

17-25.

Corpus luteum graviditatum 1. General view. Human， H-E stain， x 1.3.

17-06.

Primordial egg follicles 1. Monkey，H-E stain，x 160.

17-26.

Corpus luteum graviditatum 2. General view. Human， H-E stain， x 10.

17-07.

Scheme showing the development of egg follicles and corpus luteum.

17-27.

Corpus luteum graviditatum 3. Lutein cells. Human， H-E stain， x 64.

17-08.

Primordial egg follicle 2. Human， H-E stain， x 250.

17-28.

Corpus luteum menstruationis 1. General view. Human， H-E stain， x 1.15.

17-09.

Young primary follicle 1. Human H-E stain， x 200.

17-29.

Corpus luteum menstruationis 2. Lutein cells 1. Human， H-E stain， x 25.

17-10.

Young primary follicle 2. Human， epon section， toluidinblue stain， x 160.

17-30.

Corpus luteum menstruationis 3. Lutein cells 2. Human， H-E stain， x 160.

17-11.

A little developed secondary follicle. Human， H-E stain， x 160

17-31.

Granulosa lutein cells. Monkey， H-E stain， x 160.

17-12.

Well developed primary follicle. Human， H-E stain， x 100.

17-32.

Corpus albicans 1. Human， H-E stain， x 4.0.

17-13.

Graafian follicle 1. Monkey， H-E stain， x 25.

17-33.

Corpus albicans 2. Human， Azan stain， x 25.

17-14.

Graafian follicle 2. Cumulus oophorus. Monkey， H-E stain， x 64.

17-34.

Atretic follicle. Human， H-E stain， x 80.

17-15.

Oocyte in the cumulus oophorus. Monkey， H-E stain， x 200.

17-35.

Ovary of a human embryo 1. General view. H-E stain， x 4.0.

17-16.

Small Graafian follicle 1. Human， M-G stain， x 40.

17-36.

Ovary of a human embryo 2. H-E stain， x 64.

17-17.

Small Graafian follicle 2. Human， M-G stain， x 100.

17-18.

Small Grafian follicle 3. Stratum granulosum， theca folliculi interna et externa. Human，
M-G stain， x 160.

17 Female Reproductive System
Menu 2/2
17-002. Oviduct17-52.

17-37.

Ostium abdominale tubae 1. General view. Monkey， H-E stain， x 2.0.

17-004. Vagina and Genitalia

17-38.

Ostium abdominale tubae 2. General view. Human， H-E stain，x 2.4.

17-53.

Anterior wall of vagina and urethra. Transverse section. Human， H-E stain， x 1.7.

17-39.

Oviduct， transverse section. Human， H-E stain， x 5.0.

17-54.

Epithelium of vagina. Human. H-E stain， x 64.

17-40.

Isthmus tubae， transverse section. Human， H-E stain， x 6.5.

17-55.

Clitoris， longitudinal section. Human， H-E stain， x 3.0.

17-41.

Epithelium of oviduct. Human， H-E stain， x 250.

17-56.

Genital corpuscle. Human， H-E stain， x 100.

17-003. Uterus

17-57.

Labium minus pudendi. Transverse section. H-E stain， x 4.0.

17-42.

Uterus， transverse section. General view. Monkey， H-E stain， x 1.7.

17-005. Placenta

17-43.

Scheme showing the interrelationship between ovary and endometrium.

17-58.

Scheme showing the development of placenta 1.

17-44.

Endometrium on day 3 of menstrual cycle. Human， H-E stain， x 10.

17-59.

Scheme showing the development ofplacenta.

17-45.

Endometrium on day 7 of menstrual cycle. Human， H-E stain， x 10.

17-60.

Placenta on day 51 of gestation 1. Human，H-E stain，x 1.5.

17-46.

Endometrium on day 14 of menstrual cycle. Human， H-E stain， x 10.

17-61.

Placenta on day 51 of gestation 2. Human，H-E stain，x 13.

17-47.

Endometrium on day 22 of menstrual cycle. Human， H-E stain， x 10.

17-62.

Placenta on day 51 of gestation 3. Transverse section of a villus. Human， H-E stain， x 200.

17-48.

Endometrium on day 28 of menstrual cycle. Human， H-E stain， x 10.

17-63.

Placenta after delivery 1. Human， H-E stain， x 25.

17-49.

Superficial portion of endometriom on day 22 of menstrual cycle. Human， H-E stain， x 25.

17-64.

Placenta after delivery 2. Human， H-E stain， x 64.

17-50.

Deeper portion of endometriom on day 22 of menstrual cycle. Human， H-E stain， x 64.

17-65.

Placenta after delivery 3. Human， H-E stain， x 400.

17-51.

Superficial portion of endometrium on day 28 of menstrual cycle. Human， H-E stain， x 25.

17-006. Mammary Gland

Cervical canal， longitudinal section. Human， H-E stain， x 1.2.

17-66.

Nipple and mammary glands， longitudinal section. Human， H-E stain， x 0.7.

17-67.

Nipple， longitudinal section. Human， H-E stain， x 4.0.

17-68.

Mammary gland 1. Resting stage. Human， H-E stain，x 25.

17-69.

Mammary gland at term 1. Human， H-E stain， x 2.5.

17-70.

Mammary gland at term 2. Human， H-E stain， x 25.

17-71.

Mammary gland at term 3. Human， H-E stain， x 100.

Ovarium

Ampulla tubae uterinae
UterusTuba uterina

Cavum uteri
Excavatio
vesicouterina

Excavatio
rectouterina

Peritoneum

Rectum

Vesica urinaria

Fornix vaginae
Ostium uteri

Symphysis pubica

VaginaUrethraMons pubis
Clitoris

Anus
Perineum

Labium majus pudendiLabium minus pudendi

Ostium vaginae
Ostium urethrae
externum

17-01 Scheme showing the female reproductive System.

17-001
Ovary
17-001 Ovary17-02 Ovary and oviduct. General view. Monkey， H-E stain， x 1.2.

17-03 Overy Sagitall section， general view. Monkey， H-E stain， x 2.0.

17-04 Ovary containing a large corpus luteum. Human， H-E stain， x 1.15.

17-05 Cortex of ovary. Human， H-E attain， x 25.

17-06 Primordial egg follicles 1. Monkey，H-E stain，x 160.

Primordial follicles
Germinal epithelium
Mesoovarium

Secondary follicles Cortex
Tunica albuginea
Graafian follicle
Graafian follicle justbefore ovulation
Cumulusoophorus
Atriumfolliculi

Bloodvessels
Corpusalbicans
Corpus luteum(fully developed)

PrimaryoocyteOvulation

MedullaCorpus luteum(early stage)
Coagulated blood

17-07 Scheme showing the development of egg follicles and corpus luteum.

Stratum
granulosum

Corona radiata
Zona pellucida
NucleusFollicular epithelium

Nucleolus

Nucleus

Cytoplasm

17-08 Primordial egg follicle 2. Human， H-E stain， x 250.

17-09 Young primary follicle 1. Human H-E stain， x 200.

17-10 Young primary follicle 2. Human， epon section， toluidinblue stain， x 160.

17-11 A little developed secondary follicle. Human， H-E stain， x 160

17-12 Well developed primary follicle. Human， H-E stain， x 100.

17-13 Graafian follicle 1. Monkey， H-E stain， x 25.

17-14 Graafian follicle 2. Cumulus oophorus. Monkey， H-E stain， x 64.

17-15 Oocyte in the cumulus oophorus. Monkey， H-E stain， x 200.

17-16 Small Graafian follicle 1. Human， M-G stain， x 40.

AG

17-17 Small Graafian follicle 2. Human， M-G stain， x 100.

B

G

A

17-18 Small Grafian follicle 3. Stratum granulosum， theca folliculi interna
et externa. Human， M-G stain， x 160.

B

G

A
B

17-19 Stratum granulosum， theca folliculi interna and externa. Monkey， H-E stain， x 100.

17-20 Corpus rubrum 1. General view. Human， H-E stain， x 1.3.

17-21 Corpus rubrum 2. Luteinization is less progressed. Human， H-E stain， x 25.

17-22 Corpus rubrum 3. Luteinization is not progressed. Human， H-E stain， x 160.

17-23 Corpus rubrum 4. Luteinization is progressed. Human， H-E stain， x 25.

17-24 Corpus rubrum 5. Luteinization is progressed. Human， H-E stain， x 160.

17-25 Corpus luteum graviditatum 1. General view. Human， H-E stain， x 1.3.

17-26 Corpus luteum graviditatum 2. General view. Human， H-E stain， x 10.

17-27 Corpus luteum graviditatum 3. Lutein cells. Human， H-E stain， x 64.

17-28 Corpus luteum menstruationis 1. General view. Human， H-E stain， x 1.15.

17-29 Corpus luteum menstruationis 2. Lutein cells 1. Human， H-E stain， x 25.

AB

17-30 Corpus luteum menstruationis 3. Lutein cells 2. Human， H-E stain， x 160.

17-31 Granulosa lutein cells. Monkey， H-E stain， x 160.

C

C

C
C
17-32 Corpus albicans 1. Human， H-E stain， x 4.0.

C

17-33 Corpus albicans 2. Human， Azan stain， x 25.

17-34 Atretic follicle. Human， H-E stain， x 80.

17-35 Ovary of a human embryo 1. General view. H-E stain， x 4.0.

17-36 Ovary of a human embryo 2. H-E stain， x 64.

17-002
Oviduct
17-002 Oviduct17-37 Ostium abdominale tubae 1. General view. Monkey， H-E stain， x 2.0.

17-38 Ostium abdominale tubae 2. General view. Human， H-E stain， x 2.4.

17-39 Oviduct， transverse section. Human， H-E stain， x 5.0.

17-40 Isthmus tubae， transverse section. Human， H-E stain， x 6.5.

17-41 Epithelium of oviduct. Human， H-E stain， x 250.

17-003
Uterus17-003 Uterus

Cavum uteri

Endometrium
Myometrium
17-42 Uterus， transverse section. General view. Monkey， H-E stain， x 1.7.

Ripening of follicles

Ovulation

Corpus luteum(fully developed)

Degeneration of
corpus luteum

Death of egg

Veins
UterineglandsStr.
functionale

Bleeding
BleedingStr.
basaleMenstruation

Phase of regenerationand proliferation

Phase of secretion

17-43 Scheme showing the interrelationship between ovary and endometrium.

Phase ofischemia

Menstruation

17-44 Endometrium on day 3 of menstrual cycle. Human， H-E stain， x 10.

17-45 Endometrium on day 7 of menstrual cycle. Human， H-E stain， x 10.

17-46 Endometrium on day 14 of menstrual cycle. Human， H-E stain， x 10.

17-47 Endometrium on day 22 of menstrual cycle. Human， H-E stain， x 10.

17-48 Endometrium on day 28 of menstrual cycle. Human， H-E stain， x 10.

17-49 Superficial portion of endometriom on day 22 of menstrual cycle.
Human， H-E stain， x 25.

17-50 Deeper portion of endometriom on day 22 of menstrual cycle. Human， H-E stain， x 64.

17-51 Superficial portion of endometrium on day 28 of menstrual cycle. Human，
H-E stain， x 25.

17-52 Cervical canal， longitudinal section. Human， H-E stain， x 1.2.

17-004
Vagina and Genitalia
17-004 Vagina and Genitalia

17-53 Anterior wall of vagina and urethra. Transverse section. Human， H-E stain， x 1.7.

17-54 Epithelium of vagina. Human. H-E stain， x 64.

17-55 Clitoris， longitudinal section. Human， H-E stain， x 3.0.

17-56 Genital corpuscle. Human， H-E stain， x 100.

17-57 Labium minus pudendi. Transverse section. H-E stain， x 4.0.

17-005
Placenta
17-005 Placenta

Cytotrophoblast Blood vessels
in decidua
Syncytiotrophoblast

Marginal mesoderm

Intervillous space
Intervillous
space

Connecting stalk

AMN

Yolk sacmesoderm
YKS
Extraemblyoniccoelom

YKS: Yolk sac
AMN:Amniotic cavity

17-58 Scheme showing the development of placenta 1.

Extra-embryonicmesoderm

Epithelium of
endometrium

Blood vessel in decidua

Decidua

Cytotrophoblast
Syncytiotrophoblast
Intervillous blood space
Mesodermal core of villus
Marginal mesoderm
Decidua

Septum placentae

Blood vessels in decidua(maternal)
Cytotrophoblast
Syncytiotrophoblast
Embryonic
blood vessels
Stem villus

Chorionic plate
Epithelium of amnion
Stem villus Free villi Intervillous blood
Embryonic blood vessels
space

17-59 Scheme showing the development ofplacenta.

17-60 Placenta on day 51 of gestation 1. Human， H-E stain， x 1.5.

17-61 Placenta on day 51 of gestation 2. Human， H-E stain， x 13.

17-62 Placenta on day 51 of gestation 3. Transverse section of a villus. Human，
H-E stain， x 200.

17-63 Placenta after delivery 1. Human， H-E stain， x 25.

17-64 Placenta after delivery 2. Human， H-E stain， x 64.

17-65 Placenta after delivery 3. Human， H-E stain， x 400.

17-006
Mammary Gland
17-006 Mammary Gland17-66 Nipple and mammary glands， longitudinal section. Human， H-E stain， x 0.7.

Lactiferous sinus

Smooth muscles

17-67 Nipple， longitudinal section. Human， H-E stain， x 4.0.

17-68 Mammary gland 1. Resting stage. Human， H-E stain， x 25.

17-69 Mammary gland at term 1. Human， H-E stain， x 2.5.

17-70 Mammary gland at term 2. Human， H-E stain， x 25.

17-71 Mammary gland at term 3. Human， H-E stain， x 100.

17-00 Female Reproductive System
•
•
•
•
•

•
•

The female reproductive system consists of ovary， oviduct， uterus， vagina， and genitalia. These are all developmentally
incomplete until gonadotrophic hormones of the pituitary gland initiate puberty. The placenta during the pregnancy， andmammary glands are included in the reproductive organs.
The female reproductive system undergoes the cyclic changes under the control of the gonadotrophic hormones secreted by
the anterior lobe of the hypophysis. Cyclic changes of endometrium consists of proliferative phase， secretory phase，premenstrual phase and menstrual phase.
Proliferative phase: endometrium 1～４mm thick; glands straight and narrow; mitosis numerous in all layers; no coiled arteries
in upper third.
Secretory phase: endometrium 4～6 mm thick; glands wide， sinuous， and sacculated; epithelial cells tall with surface blebs:
superficial stroma edematous; mitosis confined to coiled arteries which extend to near the surface.
Premenstrual phase; endometrium 4～5 mm thick; lumen of glands wide and irregular in outline; arteries highly coiled: stroma
relatively dense and infiltrated with leuco- cytes.
Menstrual phase: endometrium 0.5～3 mm thick and denuded of surface epithelium; glands collapsed and short; extravasatedblood in a dense superficial stroma; arteries short and relatively straight.
Neurons in the hypothalamus release gonadotrophin-releasing-hormones ( GnRH ) that control the release of gonadotrophins( FSH and LH ) by the anterior pituitary. Secreting of follicle- stimulating hormone ( FSH ) stimulates growth of follicles in theovary. The developing follicles， in turn， secrete estradiol that stimulates endometrial growth and different- iation during theproliferative phase of the menstrual cycle. Estradiol reaching its peak level as midcycle approaches acts back on the
hypothalamus ， resulting a pulse of GnRH which results in a midcycle surge of lutei- nizing hormone ( LH ) that triggers
ovulation and transformation of the collapsed follicle into a corpus luteum.Secretion of progesteron by the corpus luteum， inthe secretory phase of the cycle， induces further change in the endometrium， preparing it for implantation and nutarition of
the blastocyst developing from the fertilized ovum during transport through the oviduct. If the cycle is anovulatory， or theovum is not fertilized， the endometrium breaks down after about two weeks， followed by menstruation

17-01 Scheme showing the female reproductive System.

•

This is to show a sagittal section of the female reproductive organs and their relation- ship to the bladder， urethra and rectum.

17-001 Ovary•

The ovary is the organ which stores the eggs ( ova ) and does not produce them. The human ovary is a thumb-top-sized，slightly flattened organ and is suspended from the ligamentum latum uteri by a peritonear fold called mesoovarium.

17-02 Ovary and oviduct. General view. Monkey， H-E stain， x 1.2.
•••

This figure shows the longitudinal ( sagittal ) sections of the ovary and the abdominal end of the oviduct， called the infundibulum.
The ovary is enclosed by the peritoneum and suspended with it from the broad ligament of the uterus. This portion of theperitoneum is called mesoovarium. The ovary consists of cortex， thick superficial dense layer， and medulla， axially locating
loose connective tissue. In the cortex there are numerous egg follicles of various sizes， whereas in the medulla many bloodvessels， entering and leaving the organ.
The oviduct expands at abdominal end forming a funnel-shaped opening， called the infundibulum. Its margins turn over ending
with fringe-like processes， the fimbriae.

17-03 Overy Sagitall section， general view. Monkey， H-E stain， x 2.0.
•

This is a longitudinal section of a macaque ovary， showing the medulla occupying its axial portion and the cortex containing
numerous follicles of various sizes and a large corpus luteum.

17-04 Ovary containing a large corpus luteum. Human， H-E stain， x 1.15.

•

This is a human ovary on day 22 of menstrual cycle， containing a large corpus luteum. Contrary to the macaque ovary， only a
few follicles are encountered in the human ovary. Left to the antral follicle there is a corpus albicans.

17-05 Cortex of ovary. Human， H-E attain， x 25.

••

The surface of the ovary is covered by a simple cuboidal or squamous epithelium， which had been erroneously called germinal
epithelium， because it had been believed that the female germinal cells， oocytes， originate from this epithelium. Beneath this isan avascular layer of connective tissue， the tunica albuginea， being much thinner than that of the testis. Further inward is the
thick cortex consisting of fibroblast-like cells that arrange very densely in a meshwork of thin collagen fibers. In the middle a
primary follicle is evidently seen， higher magnification of which is shown in 17-09.
Contrary to the macaque ovary， in the human ovary only a few follicles are seen. Com- pare with 17-02， 17-03 and 17-06.

17-06 Primordial egg follicles 1. Monkey，H-E stain，x 160.

•

These are the primordial egg follicles observed in the macaque ovary. They consist of large round oocytes， 25～30μm in
diameter， containing each a spherical nucleus， and surrounded by simple squamous follicular epithelial cells. They areembedded among the stromal cells densely arranging randomly.

17-07 Scheme showing the development of egg follicles and corpus luteum.

•

This figure shows the cyclic changes repeating in the adult human ovary， starting from the primordial egg follicle， its maturation，
the ovulation， the formation of the corpus luteum and its degeneration ( these are depicted clock-wise from the upper left
corner to the lower left ). This changes are repeating with a cycle of about 28 days.

17-08 Primordial egg follicle 2. Human， H-E stain， x 250.

••

The primordial germ cells originated from the endoderm of the hindgut migrate to the anlage of the ovary and proliferate there
during the embryonic life producing numerous oogonia. At birth the proliferation has ceased and the number of the oogonia are
estimated about 2 x 106 in each ovary. These oogonia advance on the prophase of the first meiotic division where they arearrested in the dictyate stage; that means they are already the primary oocytes in early stage. They stay for a long time in thisquiescent condition. They are surrounded by a simple squamous epithelium forming the primordial follicles and locate in the
superficial layer of the cortex， very densely arranged among the stromal cells.
This figure shows a human ovum surrounded by a simple squamous epithelium forming the primordial ( egg ) follicle. This isembedded among the randomly arranged stromal cells.

17-09 Young primary follicle 1. Human H-E stain， x 200.

••

The development or maturation of the primordial follicle begins under the control of the gonadotrophic hormones secreted by thepituitary gland. The oocyte grows larger and follicular cells become first cuboidal then proliferate to form two or three layers ofcells， that are called the granulosa cells， and the follicle itself is encircled by a distinct basal membrane. These follicles arecalled the primary follicles.
This figure shows a young primary follicle consisting of a large round oocyte surrounded by a layer of simple cuboidal cells.
Around the follicle encircles a distinct thin basement membrane ( arrow )， and further outside the stromal cells arrange
concentrically to form a theca folliculi.

17-10 Young primary follicle 2. Human， epon section， toluidinblue
stain， x 160.
•

This is also a young primary follicle; the oocyte is large and contain a large spherical nucleus. The surrounding granulose cells are
now arranged in two or three layers. Between the oocyte and granulosa cells there is a distinct limiting membrane， that is thezona pellucida ( double arrows ) and around the granulosa cells is a thin basement membrane ( arrow ). Further outside theformation of the theca folliculi is indistinct.

17-11 A little developed secondary follicle. Human， H-E stain， x 160•••

Concurrently with the development of the follicle， the stromal cells surrounding the follicle become closely packed around thefollicle to form a concentric layers， called the theca folliculi.
As these changes progress developed follicles dislocate into the deeper layer of the cortex. Numerous primordial follicles follow
in turn to develop.
This figure shows a developed primary follicle consisting of an oocyte about 60μm in diameter and granulosa cells of 3～4
layers. The zona pellucida is now thick and stained deep red with eosin. The basement membrane of the granulosa cells is also
distinct and surrounded by a theca folliculi consisting of concentrically arranged stromal cells.

17-12 Well developed primary follicle. Human， H-E stain， x 100.

••

The granulosa cells proliferate rapidly and when the follicles are about 200 μm in diameter and the granulosa cells surround theoocyte with 6～10 rows， a clear fluid begins to accumulate in inter-cellular spaces among the granulosa cells. As it increases inamount， these spaces become confluent， forming a single crescentic cavity， called antral cavity， and the fluid， liquor folliculi.
The oocyte itself is surrounded by several layers of granulosa cells and locates at one side of the follicle. This portion protrudes
into the antral cavity and is called the cumulus oophorus. These follicles are called the secondary follicles or antral follicles.
This figure shows a well developed primary follicle. Among the granulosa cells， consisting of 5 to 6 rows， appear theintercellular spaces. The zona pellucida encircling the oocyte is thick and conspicuous and the basement membrane between the
granulosea cells and theca folliculi is also evident.

17-13 Graafian follicle 1. Monkey， H-E stain， x 25.

•

This is a Graafian follicle found in a macaque ovary. The oocyte is now about 100 μm in diameter and locates in the cumulus
oophorus. The antral cavity is large and lined by a layer consisting of 5～10 rows of granulosa cells， called stratum granulosum.

17-14 Graafian follicle 2. Cumulus oophorus. Monkey， H-E stain， x 64.

•

This is higher magnification of the cumulus oophorus in 17-13. The oocyte is circle- round about 100 μm in diameter andencircled by a thick distinct zona pellucida. The spherical nucleus containing a conspicuous nucleolus is located beneath the cellsurface. Granulosa cells directly surrounding the zona pellucida are lined in a regular radiating arrangement， that are called
corona radiata

17-15 Oocyte in the cumulus oophorus. Monkey，
H-E stain， x 200.
•

The circle-round oocyte about 100μm in diameter is encircled by a thick zona pellucida， stained homogeneously deep red，
which in turn surrounded by radially arranged granulosa cells， i.e. the corona radiata. The spherical nucleus is located immediatly
beneath the oolemma and shows the later stage of the first meiotic prophase.

17-16 Small Graafian follicle 1. Human， M-G stain， x 40.

•

This is a small human Graafian follicle with conspicuous theca folliculi interna. In this specimen collagen fibers in the stroma areevident because they appear blue.

17-17 Small Graafian follicle 2. Human， M-G stain， x 100.

•Higher magnification of 17-16 showing the cumulus oophorus， theca folliculi interna and externa. In the oocyte the nucleus isout of this section. The arrangement of the corona radiate is somewhat disordered. Around the base of the cumulus thinbasement membrane is evidently seen. Outside to the basement membrane developed the theca folliculi consisting of two layers
i.e. theca folliculi interna and externa.. The theca folliculi interna (A) is composed of stocky fusiform cells with abundantcytoplasm that acquire soon features of steroid-secreting cells and numerous blood capillaries. The theca folliculi externa (B)consists of slender fusiform stromal cells， densely arranged concentrically， and connective tissue fibers. G is the cumulus
oophorus consisting of granulosa cells.

17-18 Small Grafian follicle 3. Stratum granulosum， theca folliculi interna
et externa. Human， M-G stain， x 160.
•

Higher magnification of 17-17. The left one third of this figure is occupied by the stratum granulosum ( G )， whose basal cells
attach to the distinct basement membrane， very alike with the columnar epithelium but another cells above to them arepolyhedral or star-shaped and connected together with thin processes. The central one third， right to the basement membrane，is the theca folliculi interna ( A )， consisting of stocky rounded cells with abundant clear cytoplasm and numerous blood
capillaries. The right one third of this figure is occupied by the theca externa ( B )， consisting of densely arranged spindleshaped long stromal cells and connective tissue fibers. Boundary between these two layers is not quite clear， because thecaexterna supplies new cells to the theca interna， that secrete soon the theca-lutein-hormone， estrogen.

17-19 Stratum granulosum， theca folliculi interna and externa. Monkey，
H-E stain， x 100.
•

•

•

•

This figure shows the stratum granulosum， theca folliculi interna and theca folliculi externa from top to down. The stratum
granulosum， surrounding the follicular cavity， stands on the basement membrane and consists of 8～12 rows of granulosa cells.
It seems to be a pseudostratified columnar epithelium but in fact the cells have not epithelial union to each other. The thecafolliculi interna is composed of stocky cells with abundant cytoplasm and a large round nucleus and numerous blood capillaries.
The theca folliculi externa consists of densely concentrically arranged spindle-shaped stromal cells. The undermost portion ofthis figure occupies the stroma ovarii.
In the second half of the follicular phase of the cycle， the majority of the cohort of follicles that have developed to the antral
stage begin to undergo atresia， but the domin- ant follicle goes on. There is no further enlargement of its oocyte， which has
already reach a diameter of 100μｍ， but the follicle as a whole continues to grow over the next 2 weeks with its granulosa cells， increasing enormously. Thus， a follicle that was only 2 mm on day 1 of the cycle comes to measure 15～20 mm in diameter at
the time of ovulation on day 14.
The mature follicle is a large vesicle which occupies the full thickness of the cortex and bulges 1 cm or more above the surfaceof the ovary. The thinning of its wall is due to rearrangements of its cells during the terminal phase of its growth. Accompanying
these changes， there is a coalescence of fluid-filled intercellular spaces among the cells at the base of the cumulus oophorus.
This results in detachment of the oocyte， its corona radiata and a few adherent granulose cells， which then float free in theliquor folliculi.
The first indication of impending ovulation is the appearance of a pale oval area on the bulging outer pole of the follicle， called
stigma. The change in color is due to local cessation of blood flow in the capillaries of the theca interna. Discontinuities in thegerminal epithelium and the connective tissue of the tunica albuginea soon appear， and the thin stigma bulges outward， forminga clear vesicle. Within a minute or two after its formation， the vesicle ruptures and the ovum and its adherent cumulus cells
pass through the opening， followed by a small gush of follicular fluid. This is the ovulation.

17-20 Corpus rubrum 1. General view. Human， H-E stain， x 1.3.

••

This is an ovary on day 16 in menstrual cycle. In its right half a large corpus rubrum is encountered.
After ovulation and discharge of the liquor folliculi， the wall of the follicle collapses and becomes deeply folded. The basal lamina
that formerly separated the granulosa from the theca interna breaks down. At the same time bleeding from the capillaries of thetheca interna into the intercellular spaces among the granulosa cells and antral cavity takes place， so that the folded granulosa， as a whole， appears deep red. This is called the corpus rubrum. The cells of the granulosa layer and those of the thecainterna undergo striking cytological changes rapidly; they hypertrophy， accumulate lipid droplets， and become plump palestaining lutein cells.

17-21 Corpus rubrum 2. Luteinization is less progressed. Human， H-E
stain， x 25.
••

Higher magnification of a portion of 17-20， where the luteinization is less progressed.
The undermost zone of this figure， appearing deep red， is filled by the erythrocytes， extravasated from the capillaries. Thezone upper to this zone consists of cells of pale-staining plump cells undergoing the changes to the lutein cells. The uppermost
zone， surrounding the antral cavity， is composed of cells of deep violet staining cytoplasm; they are in the first step of theluteinization.

17-22 Corpus rubrum 3. Luteinization is not progressed. Human， H-E
stain， x 160.
•

The left one third of this figure is the theca interna， in which cells have undergone the luteinization; their cytoplasm is plump
and pale-stained. The right two thirds of the figure is the stratum granulosum， where luteinization is less progressed; in thelower left portion cells are somewhat enlarged and pale-stained but the majority of cells are still slender and their cytoplasm
stains deep violet. Their nuclei are elliptic in shape and stain dark violet. They are now beginning to undergo changes into thelutein cells. Among the theca cells as well as gramulosa cells there are a lot of erythrocytes.

17-23 Corpus rubrum 4. Luteinization is progressed.
Human， H-E stain， x 25.
•

Higher magnification of a portion of 17-20， where the luteinization is progressed. In the middle an undulating thick layer of the
granulosa lutein cells traverses. Beneath this layer surrounds a red layer filled by erythrocytes and above， the antral cavity， isalso filled by erythrocytes.

17-24 Corpus rubrum 5. Luteinization is progressed.
Human， H-E stain， x 160.
•

The right three fourths of this figure is occupied by the granulosa lutein cells， that are thick ovoid in shape and of pale-staining
cytoplasm. Their nuclei are round and lightly stained. Cells with basophilic cytoplasm are here a few. The left one fourth of the
figure is the theca interna; cells are less numerous but they are already luteinized. In this portion， spaces among these cells arealso filled by innumerable erythrocytes.

17-25 Corpus luteum graviditatum 1. General view. Human， H-E stain，
x 1.3.
•

This is a human corpus luteum of the third month of pregnancy， which is fully developed and occupies almost whole interior of
the ovary.

17-26 Corpus luteum graviditatum 2. General view. Human， H-E
stain， x 10.
•

This is the fully developed corpus luteum of pregnancy. The granulosa lutein cells constitute the highly folded thick layer， around( beneath ) which surrounds a thin layer of theca lutein cells. At top left is a residue of the antral cavity filled by loose
connective tissue.

17-27 Corpus luteum graviditatum 3. Lutein cells. Human， H-E stain，
x 64.
•

The right three fourths of this figure is occupied by the granulosa lutein cells， plump ovoid in shape， up to 50μｍ in diameter，and containing a round nucleus. Contrary to them， cells occupying the left one fourth of the figure， theca lutein cells， aremuch smaller， only 15 ～ 20μm in diameter， round and somewhat loosely arranged. Among these cells capillaries and small
veins are numerously observed.

17-28 Corpus luteum menstruationis 1. General view. Human， H-E
stain， x 1.15.
•

This is a human ovary on day 22 of the menstrual cycle. The corpus luteum is very large， occupying about the half of the wholeovary and consists of highly folded thick layer of the granulosa lutein cells which encloses the residue of the antral cavity.

17-29 Corpus luteum menstruationis 2. Lutein cells 1. Human， H-E stain， x 25.

•

This is a low power view of layers of the granulosa lutein cells (A) and theca lutein cells (B). The residue of the antral cavity is
now filled by very loose connective tissue.

17-30 Corpus luteum menstruationis 3. Lutein cells 2. Human， H-E
stain， x 160.
•

This is a high power view of the granulosa lutein cells ( A ) and theca lutein cells ( B ). Among the theca lutein cells a capillary or
small vein is conspicuous ( arrow ).

17-31 Granulosa lutein cells. Monkey， H-E stain， x 160.

•

The granulosa lutein cells contain a lot of lipid droplets but they are all dissolved during the preparatory procedures using alcoholand xylene. Therefore in the usual histological specimens the lipid droplets in the lutein cell are not perceived. This specimen wasmade by frozen section method so that the lipid droplets are well preserved and their yellowish hue is evident.

17-32 Corpus albicans 1. Human， H-E stain， x 4.0.

••

If the ovulated ovum is not fertilized， the corpus luteum begins to regress after 9 or 10 days. The lutein cells undergo autolysis
and the region is invaded by macrophages that phagocytize the cellular debris. A pale-staining hyaline scar， called corpus
albicans， is left at the site， and this may persists in the ovary for many months.
In this figure several corpora alvicanta ( C ) are seen.

17-33 Corpus albicans 2. Human， Azan stain， x 25.

•

This is a portion of a corpus albicans. The hyaline substance of the corpus albicans stains light blue with aniline blue whereas thecollagen fibers in the stroma ovary， the left one fifth of the figure， stains deep blue.

17-34 Atretic follicle. Human， H-E stain， x 80.

•

In the normal ovary there are numerous degenerating follicles. Atresia of follicles may begin at any stage of their development.
This is an atretic follicle found in a human ovary. The ovum is shrunk and deformed; arrangement of follicular cells is loosen anddispersed， among that two Call-Exner bodies are seen ( arrows ). The theca folliculi surrounding the follicle is also degenerated.

17-35 Ovary of a human embryo 1. General view. H-E stain， x 4.0.

•

This is a general view of a human embryonic ovary， which consists of thick cortex containing numerous primordial follicles.

17-36 Ovary of a human embryo 2. H-E stain， x 64.

•

The primordial follicles fill the cortex of ovary. Each follicle consists of an oogonium， a large round cell， and surrounding simple
squamous follicular cells. The spaces among them are loosely filled by stroma cells.

17-002 Oviduct••

The oviduct is a long tubular organ， 10 ～15 cm in length， which accepts the ovum ovulated from the ovary and transport it
until the uterine cavity. It starts at the lateral corner of the fundus uteri， runs laterally in the upper free border of the broad
ligament of the uterus， and opens at the distal end into the peritoneal cavity， with a funnel-shaped expand， called
infundibulum. Its abdominal margins are drawn out into numerous fringe-like processes， the fimbriae. The expanded intermediate
portion proximal to the infundibulum is called the ampulla and the thin tubular portion near the uterus is the isthmus.
The wall of the oviduct consists of mucous membrane， muscle layer， and serosa. The mucous membrane projects numerous
folds into the lumen; they are in the infundibulum especially tall and repeatedly branch and anastomose so that the lumen
becomes labyrinthine. The muscle layer consists of roughly inner longitudinal， intermediate circular， and outer longitudinalsmooth muscle fibers. These muscle fibers contract rhythmically and cause peristaltic movements of the oviduct， by which theovum is transported into the uterine cavity. The serosa is the peritoneum itself.

17-37 Ostium abdominale tubae 1. General view. Monkey， H-E stain， x 2.0.

•

This is the longitudinal section of the infundibulum and fimbriae of a macaque oviduct. The abdominal margins of the infundibulum
turn over and its mucous membrane makes numerous fringe-like processes， fimbriae， that flatter in the peritoneal cavity.

17-38 Ostium abdominale tubae 2. General view. Human， H-E stain， x 2.4.

•

This is the longitudinal section of the infundibulum and fimbriae of a human oviduct. The fimbriae are here less numerous andmuch thinner than those of 17-37.

17-39 Oviduct， transverse section. Human， H-E stain， x 5.0.

•This is the transverse section of the ampulla of a human oviduct. The mucous membrane protrudes into the lumen forming
numerous folds， short and long， that branch repeatedly， so that the lumen appears as labyrinth.

17-40 Isthmus tubae， transverse section. Human， H-E stain， x 6.5.

•

This is the transverse section of the isthmus of a human oviduct. The lumen is here narrow and folds of mucosa are low andless numerous; the muscle layer is relatively thick.

17-41 Epithelium of oviduct. Human， H-E stain， x 250.

••

The epithelium of the oviduct consists of simple columnar cells of two kinds. The one are tall columnar cells with prominent cilia，that flutter actively and cause a flow toward the uterus， by which the ovulated ovum is swallowed into the oviduct and conveyed
through it toward the uterus. The others are tall secretory cells without cilia， intermingled among the former. The mucous
membrane of the oviduct is under the influence of the hormones secreted from ovary and undergoes the cyclic changes.
This figure shows the epithelium of a human oviduct on day 22 in the menstrual cycle. The differences between the two kinds ofepithelial cells are evident. The terminal bar of the ciliated cells is conspicuous.

17-003 Uterus•

The uterus is a pear-shaped organ with a thick muscular wall， about 7 cm long， 4 cm across at its widest， and 2.5 cm thick. It
is slightly flattened and normally tipped forward. The peritoneum covering its dorsal and ventral surfaces continues from the sideof the organ to the wall of the pelvis， forming two leaves of the broad ligaments which support the organ. The rounded upper
portion is called the fundus and lower to this follow the body， corpus uteri， and further cervix uteri. The axial portion of theorgan occupies a flattened cavity， cavum uteri， triangular in outline， which continues with its two upper corners with thelumina of the oviducts and with its lower corner with the cervical canal opening into the vagina.

17-42 Uterus， transverse section. General view. Monkey， H-E stain， x 1.7.

•••

This is a transverse section of the body of a macaque uterus. In the middle is the uterine cavity， cavum uteri， which issurrounded concentrically by the mucous membrane， endometrium， thick muscle layer， myometrium， and thin peritoneum，
peri- metrium， which is very thin and not perceivable at this magnification. The peritoneum， covering the dorsal and ventral
surfaces of the organ becomes at the sides two leaves of the broad ligament， ligamentum latum uteri， which continues to thewall of the pelvis and acts as a support of the organ. Through the broad ligament blood vessels， lymphatics and nerves enterand leave the organ.
The endometrium undergoes cyclic changes under the control of hormones secreted by ovary， that will be discussed later.
The myometrium is the thick layers of smooth muscle fibers that interlace in all directions and as a whole， acts to drive out the
fetus at delivery.

17-43 Scheme showing the interrelationship between ovary andendometrium.
••

The mucous membrane of the uterus， endometrium， undergoes the cyclic changes under the control of the hormones secretedby the ovarium. This scheme shows the interrelationship between the ovary and endometrium.
In a normal menstrual cycle， the endometrium goes through a cobtinuous sequence of histological changes， which are divided
into three stages: the proliferative， the secretory and the menstrual phages. The proliferative phase coincides with the secretionof the estrogen by the growing follicles. The secretory phase is the period during which a functional corpus luteum is secretingprogesteron. The menstrual phase is a period of degeneration associated with a rapid decline in stimulation of the endometriumby ovarian hormones.

17-44 Endometrium on day 3 of menstrual cycle. Human， H-E stain， x 10.

••

This is the endometrium on day 3 of the menstrual cycle. Except for the basalmost thin layer， the stratum basale， all thesuperficial layers of the endometrium， the stratum functionale， were lost and now the surface of it is the wound. In theremaining basal layer only a few sections of the uterine glands are seen.
Compare the figures 17-44 ～17-48 to understand the menstrual changes of the human endometrium， at the same
magnification; all of them are operation materials.

17-45 Endometrium on day 7 of menstrual cycle. Human， H-E stain， x 10.

•

This is the endometrium on day 7 of the menstrual cycle. The superficial wound is restored and the epithelium covers thesurface， and above the basal layer the func- tional layer is newly formed， in which longitudinal sections of the uterine glands
with spiral course are seen. The stroma cells among the uterine glands are arranged loose. In the basal layer the stroma isdensely invaded by the leucocytes.

17-46 Endometrium on day 14 of menstrual cycle. Human， H-E stain， x 10.

•

This is the endometrium on day 14 of the menstrual cycle. The functional layer is quite thick but its structure is relatively loose.
The lumina of the uterine glands， moderately coiled， widen and begin to secretion. The stroma among the uterine glands is not
so rich in blood vessels. The ovulation may occur on this day.

17-47 Endometrium on day 22 of menstrual cycle. Human， H-E stain， x 10.

••

This is the endometriim on day 22 of the menstrual cycle. The thickness of it reaches at maximum， about 5 mm. The uterine
glands are lengthened， becoming tortuous and showing lateral sacculations that give them a relatively large lumen of irregularoutline. In the basal zone the glands remain slender and their lumina show smoose contour. Among the widened stroma there are
numerous blood and lymph vessels. The spiral arteries extend into the stroma near the surface. Numerous veins of straightcourse toward the basal layer are seen in the stroma between the glands. Lymphatics of large caliber are also numerously seen.
In the superficial portion the stroma cells proliferate and take on an epithelioid appearance and become concentrated to form thestratum compactum， distinct from a stratum spongiosum in the lower portion where the stroma cells do not undergo thiscytological change and interspaces among them are widened and filled by fluid exuded from the blood vessels resulting in theedematous appearance. In the most basal portion the stroma is invaded by a lot of leucocytes densely.

17-48 Endometrium on day 28 of menstrual cycle. Human， H-E stain， x 10.

•

•

•

This is the human endometrium on day 28 of the menstrual cycle， showing the condition directly before the onset of
menstruation. In the superficial portion， stroma cells become plump and densely packed without the intercellular spaces，
showing the condition of decidualization. Lower to this zone， in the stratum spongiosum the intercellular spaces of stroma cells
open but edematous condition is not distinct and glands collapsed. At the lowermost zone， indicated with an arrow， the stroma
is loosen and ischemic and here breaking off of the zona functionalis will occurs. In the stratum basale the gland are short andslender and the stroma is invaded by innumerable leucocytes.
If the ovulated ovum is not fertilized， marked vascular changes occur in the endometrium about two weeks after ovulation. The
endometrium is blanched for hours at a time， owing to constriction of the spiral arteries that deprives the zona functionalis ofoxygenated blood. The endometrium stains more deeply and appears more cellular because it has lost much of its interstitial
fluid. The glands cease to secrete and the stroma is invaded by large numbers of leucocytes. After about 2 days of intermittent
interruption of blood flow to the upper two-thirds of the endometrium， constriction of the spiral arteries becomes continuous，
resulting in ischemia of the zona functionalis， while blood continues to flow in the zona basalis. Necrotic changes in the zonafunc- tionalis progress. Hours later， the constricted arteries reopen， permitting blood to flow through vessels that have beendamaged by ischemia. Vessel walls rupture and blood escapes into the stroma and soon breaks out into the uterine lumen.
Clumps of blood-soaked necrotic endometrium break away leaving the torn ends of glands and open ends of blood vessels
exposed at a new surface. Blood continues to ooze from the open ends of veins， contributing to the menstrual flow. Normallythis blood does not clot. By the third or fourth day of menstruation， the entire functionalis has sloughed off.
The zona basalis of the endometrium remains intact and viable， and before menstrual flow has entirely ceased， epithelial cells
begin to proliferate and migrate from the open ends of the glands to restore a surface epithelium. New blood vessels sprout fromthose at the base and the stroma cells proliferate and secrete the fibrous and amorphous com- ponents of an abundant
extracellular matrix. With the onset of these regenerative activities， the proliferative phase of new cycle begins.

17-49 Superficial portion of endometriom on day 22 of menstrual cycle.
Human， H-E stain， x 25.
•

In the superficial portion the stroma cells proliferate and take on an epithelioid appearance and become concentrated to form thestratum compactum. This change is called the decidualization. This figure shows its beginning condition. In the lower half of thisfigure shows the stroma edematous appearance. The glands are highly tortuous and their lumina show lateral sacculation withirregular outline.

17-50 Deeper portion of endometriom on day 22 of menstrual cycle. Human，
H-E stain， x 64.
•

This figure shows the edematous stroma containing a spiral artery and a straight vein. The stromal cells are here stellate in form
and unite each other with long processes. Intercellular spaces are wide and filled by fluid exuded from the bluud vessels， that isedema. In the left there is a spiral artery goes upward through the edematous stroma， in the right is a vein， which runs straightfrom top downward.

17-51 Superficial portion of endometrium on day 28 of menstrual cycle.
Human， H-E stain， x 25.
•

This is the superficial portion of human endometrium on day 28 of the menstrual cycle in which the stroma cells are enlarged anddensely packed without intercellular spaces and the decidualization of the endometrium is accomplished. In the lower half of thisfigure intercellular spaces are narrow and ischemic.

17-52 Cervical canal， longitudinal section. Human， H-E stain， x 1.2.

•

The cervix uteri is a cylindrical portion which is continuous with the uterine body， above， and protrudes into the vagina as
portio vaginalis， below. The axial portion of it penetrates the cervical canal， which opens above into the uterine cavity andbelow into the vagina through the external os. The canal is lined by a mucosa with a highly irregular surface with numerous ridges
or folds called the plicae palmatae. The mucosa of the cervix does not undergo cyclic changes. The wall of the cervix iscomposed mainly of dense connective tissue containing a small numbers of smooth muscle fibers.

17-004 Vagina and Genitalia

17-53 Anterior wall of vagina and urethra. Transverse section. Human，
H-E stain， x 1.7.
•

The vagina is a flattened tube， 8～9 cm in length， 2～3 cm in width， extending from the uterine cervix to the vestibulum of thefemale external genitaria， and has the anterior and posterior walls. Anterior to the vigina runs the female urethra from theurinary bladder to the vestibulum along the midline， causing a slight rise of the anterior wall of the vagina into the lumen， called
urethral carina.

17-54 Epithelium of vagina. Human. H-E stain， x 64.

••

The wall of vagina consists of the mucosa， the muscular coat， and adventitial connective tissue. The mucosa consists of astratified squamous epithelium and underlying lamina propria. The epithelium is 150～200μm in thickness and composed ofseveral to ten rows of cells， whose cytoplasm is filled with glycogen and stains deep violet. The superficial cells are continuously
shed into the lumen and glycogen from the desquamated cells is rich substrate for certain members of the bacterial flora， which
break it down to lactic acid， lowering the pH of the vagina.
This figure shows the vaginal epithelium attaching to a distinct basement membrane. The epithelial cells are polyhedral in shapeand their cytoplasm stains deep violet. The superficial cells containing the nucleus are desquamated successively.

17-55 Clitoris， longitudinal section. Human， H-E stain， x 3.0.

•

This is a horizontal longitudinal section of a human clitoris， which corresponds to the dorsal portion of the penis in the male. It
consists of connective tissue core and covering thin skin. In the core there are paired rudimentary corpora cavernosa. The skinis thin but numerous papillae are encountered. Beneath the skin a genital corpuscleis seen.

17-56 Genital corpuscle. Human， H-E stain， x 100.

•

This is a genital corpuscle found in the clitoris ( 17-55 ). In the subcutaneous connec- tive tissue of the clitoris is rich in nerve
endings. One of them is the genital corpuscle， which is a round corpuscle consisting of nerve endings and Schwann cells andencircled by connective tissue capsule.

17-57 Labium minus pudendi. Transverse section. H-E stain， x 4.0.

•

The labia minora pudenda are thin folds of skin flanking the vestibulum vaginae. This figure shows a labium minus pudenda
transversely sectioned. The epidermis is relative- ly thick and cells of its germinal layer contain much melanin granules. The
connective tissue core contains numerous blood vessels and nerves. The labia minora have no hairs but there are numerous
small sebaceous glands

17-005 Placenta (1/2)••

Directly after the ovulation fertilization takes place in the infundibulum of the oviduct. The fertilized ovum， zygote， is conveyed
toward the uterus through the oviduct by the flow caused by fluttering of the epithelial cilia and also by peristaltic movement of
the musculature of the oviduct. During the conveyance zygote divides once about a day repeatedly， forming a small sphericalmass of cells called the morula. It arrives at the uterine lumen on about the fourth or fifth day as the blastcyst， consisting of
numerous cells with a central cavity in its interior. On about the sixth day after fertilization the zona pellucida is loosen anddisappears， and the blastcyste attaches to the surface of the secretory endometrium. The endometrium responds by transformation of its fusiform or stellate stromal cells into large， polyhedral， pale-staining decidual cells. They contain large stores ofglycogen and lipid in their cytoplasm， with that they prepare a favorable milieu for nutrition of the early embryo.
At this time there is a cluster of cells at one pole of the blastcyst， called the inner cell mass， which is destined to form theembryo proper， whereas the remainder of the hollow sphere consists of trophoblast cells， that will form the placenta. The
blastcyst attaches to the endometrium at the pole of the inner cell mass and begins to invade into the endo- metrium. The
trophoblast cells proliferate rapidly and give rise to an inner layer of cytotrophoblast， composed of separate cells， and a thickouter layer， the syncytiotro- phoblast， which is a continuous multinucleate layer of cytoplasm， in which no cell boundaries are
discernible. The cytotrophoblast proliferates actively and continuously forms new cells that fuse with， and are incorporated into，
the growing syncytio- trophoblast.

17-005 Placenta (2/2)

•

•

•

The syncytiotrophoblast actively erodes the endometrium， enabling the blastocyst， as a whole， to sink deeper into it. By the
11th day， the blastocyst is entirely within the endometrium， and surrounded by thick syncytiotrophoblast. This course iscalled the implantation. The discontinuity created in the surface of the endometrium is covered by cellular debris in a fibrin
clot until the epithelium regenerates over the implantation site.
As the expanding layer of syncytiotrophoblast around the blastocyst continues to invade the surrounding endometrium，appears in it a labyrinthine system of intercom- municating lacunae filled with blood liberated from blood vessels in theendometrium eroded. This blood is the initial source of nourishment for the embryo， and its liberation from endometrial
vessels is the first step toward establishment the utero-placental circulation on which the growth of the fetus will later
depend.
At 11 days postovulation， the embryo proper is a bilaminar disc consisting of a thick plate of columnar epitheliar cells， theectoderm， and a thinner layer of squamous or cuboidal cells， endoderm. The ectodermal plate is continuous at its margins
with a layer of squamous cells that enclose a small amniotic cavity. The endoderm is continuous at its margins with a sheet ofcells that encloses the yolk sac. A wide space， exocoelom， between these derivatives of the inner-cell mass and thetrophoblastic sell is traversed by thin strands of extraembryonic mesenchyme. The broad peripheral zone of the trophoblast ishenceforth called the chorion.

17-58 Scheme showing the development of placenta 1.

••

From the 11th to the 16th day， the products of conception， embryo， continue to enlarge at the expense of the surrounding
endometrium. Erosion of endometrial blood vessels becomes more extensive with many communications forming between theendometrial venous sinuses and the lacunae within the syncytiotrophoblast. From the 15th day onward， cords of trophoblast
grow outward from the trophoblastic shell to the opposite wall forming the primary chorionic villi. These are soon invaded at theirbase by mesenchyme that advances to their tips， converting the primary villi into secondary chorionic villi， consisting of anouter layer of syncytiotrophoblast and an inner layer of cytotrophoblast around a core of mesenchyme. They are bathed inmaternal blood that flows sluggishly through a system of intercommunicating vascular channels that collectivrly form theintervillous space. The cytotrophoblast beneath the syncytio- trophoblast of each secondary villus advances and reaches the
opposite wall and pentrates the syncytiotrophoblast， and spreads laterally over the syncytiotrophoblast， coalescing with similar
outgrowth from neighbaring villi to form a continuous tropho- blastic shell， which is interrupted only at site of communication ofmaternal blood vessels with the intervillous space.
This scheme shows the conditions of products of conception at this stage. The secondary chorionic villi consist of mesenchymal
core， surrounding cytotrophoblast， and superficial syncytiotrophoblast being bathed in the maternal blood. They are called stem
villi， later. They stand on the basal surface of the intervillous blood spsce and continuous with the trophoblast of another side，i.e. decidual surface of the intervillous blood spaces.

17-59 Scheme showing the development ofplacenta. (1/2)

•
•
•

•

•

①：End of the 4th week.
②：end of the 4th month.
Figure ① shows a portion of the stem villi and inetervillous blood spaces. The base of each stem villus stands on the marginal
mesoderm ( mesenchyme )， from which the mesenchymal core enters into the villus. This core is enveloped by thecytotrophoblast and syncytiotrophoblast. From the surface of the villus numerous side branches pro- trude into the intervillous
blood spaces. In the mesenchyme of marginal mesoderm and core of each villus appear capillary vessels which are continuouswith blood vessels of the fetus.
Figure ② shows a more developed condition of the placenta. The stem villi grow longer， widening the distance between thechorionic plate and decidua. The branches of the stem villi branch repeatedly resulting in innumerable free ending small branches
that fill the enlarged intervillous blood spaces. Capillaries in the mesenchymal core progress distalward and reach the tip of eachbranch， directly beneath the syncytio- trophoblast. Thus the exchange of nutrient substances in the maternal blood and waste
in the embryonic blood takes place efficiently through the enormously wide surface of the chorionic villi.
As the stem villi grow higher， the decidual tissue between two stem villi is left behind and protrudes into the intervillous space
as a septar plate covered by the syncytio- trophoblst and cytotrophoblast. This is called the septum placentae.

17-59 Scheme showing the development ofplacenta. (2/2)
•

•
•

•

During the development of embryo， the decidua differentiates into three portions: ① decidua between the embryo andmyometrium， decidua basalis， which elaborates later the maternal portion of the definitive placenta. ② decidua between theembryo and uterine cavity， decidua capsularis， which covers the embryo. ③ decidua lining the remainder of the uterus，
decidua vera.
As the embryo grows larger， decidua capuslalis covering the embryo bulges highly into the uterine lumen making this narrowerand finally attachs to the decidua vera of the opposite wall of the uterus resulting in the obliteration of the uterine cavity.
Up to the end of the eighth week of gestation， the vlli are equally numerous around the entire circumference of the chorion. As
pregnancy advances， villi associated with the decidua basalis rapidly increase in number and length， whereas those associatedwith the decidua capsularis degenerate， so that by the third month this surface of the chorion is smooth and relatively
avascular. Henceforth， this region is called the chorion leave， whereas in the portion associated with the decidua basalis villi
develop highly and this portion is called the chorion frondosum. This discoid basal area of the chorion goes on to form the fetal
portion of the definitive placenta
By four and half months， the uterine lumen is largely obliterated， the decidua capsu- laris is no longer present and the chorion
leave has fused with the decidua vera on the opposite side of the uterine lumen. In the subsequent development of the placenta，
there is a steady increase in number and length of the villi of the chorion frondosum and an expansion of the intervillous space.

17-60 Placenta on day 51 of gestation 1. Human，
H-E stain， x 1.5.
•

This is a human placenta on day 51 of gestation， from the chorionic plate ( lower edge ) to the decidua ( upper thick violet
tissue ). From the chorionic plate stand numer- ous stem villi toward the decidua but their branches in the intervillous spsce arestill not so many.

17-61 Placenta on day 51 of gestation 2. Human，
H-E stain， x 13.
•

Higher magnification of the chorionic plate and stem villi of 17-60. In the chorionic plate and stem villi the fetal blood vessels are
seen. The stem villi are quite thick but their free branches are not so numerous. The surface of chorionic plate and that of stem
villi are throughout covered by the syncytiotrophoblast.

17-62 Placenta on day 51 of gestation 3. Transverse section of a villus.
Human， H-E stain， x 200.
•

Higher magnification of 17-60. This is a transverse section of a villus. The surface of the villus is covered by thesyncytiotrophoblast， consisting of numerous dark nuclei and deep violet staining cytoplasm， which has conspicuous microvilli
but devoids entirely cell boundary. Directly beneath it underlies the cytotrophoblast composed of separate cells. They are roundin shape and their cytoplasm is clear ( arrows ). The core of the villus consists of very loose connective tissue， mesenchym，
containing small numbers of stellate cells， among which two fetal capillaries containing each one nucleated primitive erythroblast
are seen. Around the villus is the intervillous blood space in which maternal erytrocytes are recognized.

17-63 Placenta after delivery 1. Human， H-E stain， x 25.

•

This figure shows a stem villus and innumerable sections of free villi， filling the intervillous blood space. In the stem villus large
and small blood vessels of fetus are seen. The surface of the stem villus and of small villi are all covered by a thin layer ofsyncytiotrophoblast stained deep violet.

17-64 Placenta after delivery 2. Human， H-E stain， x 64.

•

Higher magnification of 17-63. The large and small sections of chorionic villi are shown. They are all enclosed by a thin layer ofsyncytiotrophblast. As the development of the placenta progresses the cytotrophoblast divides very actively to supply the new
cellular components to the syncytiotrophoblast which covers the growing branches， but in the later term of gestation， where
growth of the placenta is slowed down， division of cytotrophoblast becomes less active and the cells that performed the final
division coalesce into the syncytiotrophoblast and disappear. In the placenta after delivery the cytotrophoblast-cells are seldom
encountered beneath the syncytiotrophoblast. Arrows indicate the cytotrophoblast-cell.

17-65 Placenta after delivery 3. Human， H-E stain， x 400.

•

This is a higher magnification of a section of a villus. The surface of this villus is covered by a layer of the syncytiotrophoblast
consisting of deep violet stained cytoplasm and dark blue stained elongated nuclei. On the surface of the cytoplasm microvilli areconspicuously observed. Beneath the syncytiotrophoblast two cytotrophoblast-cells having a round and clear cytoplasm and alarge moderately stained nucleus are recognized ( long arrows ). Several fetal capillaries attach directly to the syncytiotrophoblast ( short arrows ); this is a favorable condition for the efficient exchange of nutrient substances in the maternal blood
and waste in the fetal blood.

17-006 Mammary Gland•

The mammary glands are paired gland located on the thorax. They provide for the nourishment of the offspring. In the female theglands undergo extensive structural changes associated with puberty， pregnancy， and menopause. They reach their greatest
development in about the 20th year， and atrophic changes appear by the 40th year and become marked after menopause.

17-66 Nipple and mammary glands， longitudinal section. Human，
H-E stain， x 0.7.
•

This is a general view of a longitudinal section of a human resting mammary gland. The mammary gland is a compound tubuloalveolar gland consisting of 20～30 lobes drained by the same number of ductus lactiferi that open on the tip of the nipple.

17-67 Nipple， longitudinal section. Human， H-E stain， x 4.0.

•

This is the tip of the nipple. Several lactiferous ducts penetrate longitudinally through the nipple. Around each duct encircle
numerous smooth muscle fiber bundles. Shortly before opening each duct is slightly dilated to form a lactiferous sinus.

17-68 Mammary gland 1. Resting stage. Human， H-E stain， x 25.

•

This is a lobe of the resting mammary gland. Each lactiferous duct divides at its distal end several times into branches with blindends and remains in this condition during the resting period. The epithelium of the distal portion of the duct consists of twolayers of the low cuboidal cells. Each lobe is surrounded by a small amount of connective tissue.separately.

17-69 Mammary gland at term 1. Human， H-E stain， x 2.5.

••

This is a human mammary gland at term. Each lobe is fully developed and encircled separately by the connective tissue. The
connective tissue capsule enclosed the whole glands does not exist.
Since the beginning of the pregnancy there is a rapid growth in length and branching of the duct system and proliferation ofalveoli. This growth of the epithelial components of the gland takes place at the expense of the adipose tissue of the mamma.

17-70 Mammary gland at term 2. Human， H-E stain， x 25.

•

Higher magnification of 17-69. The distended lumen of alveoli is lined by a simple coboidal epithelium consisting of cells with clear
cytoplasm. Spaces between the alveoli are densely filled by capillaries containing erythrocytes.

17-71 Mammary gland at term 3. Human， H-E stain， x 100.

•Higher magnification of 17-70. The lumina of alveoli are distended and lined by simple cuboidal cells with clear cytoplasm anddeep stained round nucleus. Around the alveoli there are dense capillary network filled by erythrcytes.