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Home , Cumulus oophorus, Epoophoron, Myometrium, Ovarian ligament

MD-22 II.

56-3100

HUMAN FEMALE REPRODUCTIVE SYSTEM SET

BOBBITT I:~ 1-'- LABORATORIES

BURLINGTON, ",ORT", CAROLINA

Carolina Biological Supply Company

Main Office Powell laboratories Division Burlington, N. C. 27215 Gladstone, Oregon 97027

Printed in U.S.A. © 1968 Carolina Biological Supply Company Dorsocranial Fig.l

Ventrocaudal

Fig.3 II

56-3100 to 56-3120 Human Development

The female reproductive system includes the , the fallo­ pian tubes, the , the , and the external genital organs. The uterus in its most usual position is turned forward so that the fundus is directed ventrally toward the . In this position the fallo­ pian tubes lie anteriorly and the ovaries are on the upper surface of the broad . Figs. 1 and 2 show these structures from the upper (dorsocranial) and lower (ventrocaudal) aspects. The entire system lies in an invagination of the and is thus not within the . The heavy lines around the uterus in Fig. 3 represent the peri­ toneum. The most usual representation of the system shows a frontal section through the uterus, , and fallopian tubes. To obtain such a section the uterus must be reflected along the line shown in Fig. 3.

The paired ovaries are the source of all of the eggs produced by the mature female. These occur in the cortex of the ovary and are in an undeveloped form called the primary germ cell. There are some 400,000 of these in the ovary at puberty and the supply is exhausted at about 50 years of age. Many of these potential eggs do not develop fully but are lost.

The first phases in the development of the egg occur before birth. Small masses of cells appear in the as it develops. The cell masses, called primordial follicles, each consist of a central germ cell (oogonium) surrounded by a single layer of flattened epithelial cells. From the third month to birth the germ cells undergo a maturation peri­ od during which they enlarge and their nuclei begin the first meiotic di­ vision. They are called primary at this time and measure about 40 mu in diameter. No further changes occur until puberty.

In the mature individual, several of the primary follicles undergo maturation every 28 days, though usually only one reaches full maturity.' This maturation consists of a proliferation of the epithelial cells and a two-fold increase in the size of the germ cell. A heavy membrane, the , appears around the germ cell (), As the epithelium (granulosa) continues to proliferate, it becomes several cells thick and small pockets of fluid appear between the cells. These fluid -filled spaces move together into the center of the cell mass to form a single pocket, the antrum. The oocyte lies to one side of the antrum and is surrounded by a mass of granulosa cells called the .

3

", fi~~'Mis,.,--- P o l a r body I

--,~~_Cytoplasm

'!tI14~~+-p.~--Nucieus Vitelline membrane

T he sur rounding ovar ian ti s sue bec om es mo dified to form a she ath or the ca which will di fferentiate int o two lay ers, the inter nal and exter ­ nal th ecae. T he follicle enlarges until it forms a distinct bulge on the surface of the ovary. T he surface of the follicle the n thin s down until it r up tur es, releasing the oocyte. A layer of follicular cells, the co rona ra­ di ata , su r r ounds the free oocy te (Fig. 4). T he oocyte is car ried through the ab domina l orifice of the fa llopian tube by c iliary actio n. The fi rst m e iotic division i s now completed with th e extrusion of th e fi r s t polar body, and the c ell be c ome s a secondary oocyte . The second m ei oti c di­ vision is initiated im mediately . T his div ision is co mpleted after e ntry of the spe r m and usually occurs as the cell is car ried through th e ovi ­ duc t.

T he second m eioti c division r esults in a haploid egg and a second pol ar body . At thi s time the egg m easure s abou t 130 mu in diameter . The sper m head i s mo dified to bec ome the male pronucleu s , which then unite s with the fe male nucleu s. With th is fusion, the zygote i s formed.

Cleavage i s init iated by the divi sion of the zygo te into two unequal bl a stom er e s. The large r of the two cells soon divide s again , r esulting in a three-celled em bryo. Rep eat e d irregular divi sions give rise to a solid m a s s of cells called the m orula. A cavity appears in the ce nter of this cell m a s s a nd in cre a se s in s ize until the em bryo r e semble s a hollow ball. F our t o five days af ter fe r tilizatio n the embryo (bla stocyst) con­ s ists of an outer shell of cells, the cho r io n, surrounding an inner cell mass, the embryoblast, and a large liquid -filled cavity, th e blastoc oele (Fi g. 5). As these divi sions take pla ce, the embryo migrate s from the

4~~~~~~~~~~~EmbrYOblast V, Endoderm

Trophoblast

4 uterine tubule into the uterus and enl arges to abo ut 200 mu in diamete r. Implantation occurs at ab out 7 -1 / 2 day s afte r fertiliz ation.

T he ute r in e epith elium di s s olves away at th e point at whi ch the bl a stocyst touches it and the embryo sinks into the s uperfic ial layers of the . The blastocyst be com e s or iented so that th e inner cell mas s is toward the uterus . T he wall of the embryo fa cing the uterus be­ com e s thickened and differentiates int o two ti s su e l ay er s. The deeper l ayer, th e s yntrophobla st, is in contact with the ut erus. It has no cell wall s a nd s hows little mitotic activity. T he out e r layer , the cytotropho ­ blast, is cellular ancl i s m itotically very active. These two ti s su e layers m ak e up the chorion of the em bryo.

.- ... -­ .. ...

== :-"","::...:.:.o;; Ifl:i! ~ ':7- - A mnio n 1lt\-:...... ,.c:..o:!lOi~,:-,.,.- E m b r y o n i c d isc

~-+~-E n d o de r m -iI'''f--Mesod er m

Ao',;~- 'Cy tot r o p h o b las t '; ...... :"',J Synt rophoblast

:~~".;@""",,_~~:~; ..;o-'

i\. small s pace , the a mnio tic cav ity , appears in the inner cell m a s s . The po rtion of the cell m a s s ext er nal to the cav ity is th e em bryonic di sc. i\. lo osely or ganized m a s s of cells exter nal to th e em bryonic disc is the e ndode r m . The cells of the endoderm pr oliferate rapidly, spreading away from th e disc to line the ca vity of the bl a stocyst. This cavity is now the primary yolk sa c . The portion of th e bl a stocoel e external to the y olk sac becomes loo sel y fi lled with primary m e soderm (Fig . 6) . By th is time (about ]2 clay s) the bla stoc yst, which is about 1 mm in di amet er, ha s been com ple te ly covered over by r egenerating t issue of the ut erine epi ­ thelium . T he are a of penetration is m arked by a mass of tissue debris c alled th e op erculum.

Spaces or lacunae now begin to appear in the synt r ophoblast of the embryo. Many of th e se spaces are I'ilIed with maternal bl ood, sup­ plied from s m all s piral arter ies in the endom etrium of t he uterus. TI1e trophobla stic tis sues rapidly increase in extent, eve ntually completel y s ur round ing the e mbryo. TI1e cytotrophobla st forms numerous projec­ ti ons ext ending towar d the maternal tis sue. The se ar e c overed with s yn­ trophobla stic ti.ssue and fo r m the prim ary villi. The se villi enlar ge, ac ­ quire a m e senchymal core and Circul a tory tissue, a nd u sually give r ise to many secondary br anches ( Fig. 7) . At the tips of s ome of the s e villi , the cy t otrophoblastic cells multiply to form columns whi ch per fo r ate the synt r ophoblast and r each the maternal tissue. Such villi s erve to attach

5 F;g. 7 Q ~ ~ 7; -:- ~' IJ .... --- basali s i,;:::;:f;?~::: :'; · · \ ...:

'. ;:. 'i=;{ C yl rophobla sl

m,.cl¥ .",,---Mesoderm

th e securely to th e ut erine tissues. T he inte r vi llou s spaces are com pletely line d w ith sy ntrophobla s tic tissue. At ab out th ree weeks th e blastocy st i s appr oxim a te ly 8 111m in diameter. Within th e chorion, th e primary m e sode rm ha s di sappeared except fo r the body stalk and ha s left a n exococl ornic cavity. T he embryo lies between the cavities of the qmninn and th e volk sac.

Fig.8

The embryo, as it deve lops ove r th e ne xt few weeks, grows into the s ac of the amnion. This tu rns th e yolk s ac s o th at it lies along the body s ta lk (Fig. 8). By th e e nd of th e fi r st month, the em br yo and its m embranes form a di stinct bul ge on the inner uterine sur face . This em­ bryo is s till covered wit h endome trium (de c idua capsular i s) on the lum en s ide a nd i s surrounded by a villou s c horion. During the second month t he decidua capsularis begins to become t hin a nd the villi of the chorion in thi s a rea bec om e dispersed and degenerate . The villi in the area of the a ttachment to th e uterus becom e strongly de veloped and, by the m id ­ dle of the third month, the placental di sc i s c om pletely formed. The am­ nion has now expanded to fuse wit h the chorion laeve a nd to line the body s talk (umbilica l cord) . T he yolk sac lies in t he vestige of the exocoelom in the cord .

T he early embryo consists of a two-layered disc, the dorsal ec ­ toderm (toward t he a m nionic cavity) a nd the ventral endoderm (toward 6 the yolk sac). The body stalk is attached to the posterior end 01 the em ­ bryonic disc. In the posterior porticn of the embryo

Continued cell proliferation in the area of the primitive pit re­ sults in the displacement of the pit caudally. New lengthw i se folds

As the neural tube closes, the branchial bars begin to form and the heart becomes clearly Visible. As the embryo reaches 3.5 mm, the ventral flexure has become extreme. Three branchial bars are visible and a tail is fully formed. There are now about 29 somite s. The arm buds appear at this time and the leg buds appear two day slater. Shortly thereafter a fourth branchial bar develops. The vesicle of the eye lens now begins to indent and the olfactory pit appears. At 32 days the em­ bryo has reached a length of 8 mm, both appendage buds are formed, and both the optic and otic vesicles are in evidence.

Fig.9 (i) lmm ~ 2.5mm V3.5mm mm 30mm Q7mm ~.•.. 12 18 days 21 days 26 days W D 4i weeks 5 weeks

8 weeks

The appendage buds elongate and show regional segmentation, dif­ ferentiation occurring in the arm bud first. The head becomes relative­ ly much larger than the trunk and the branchial bars are less evident, By about the 40th day (22 mm) the embryo has fingers and toes apparent and eyelids begin to show. During the next two weeks the formation of the head with distinct features is completed. The embryo is about 30 mrn long at this time, the tail is completely gone, and the basic form of the

7 organism has been attained. This is generally considered to be the end of the embryonic period and the beginning of fetal life. The latter is characterized by development of structures which already exist in the embryo. Fig. 9 shows the relative size of the embryo at the ages re­ viewed above.

Suggested References

Davies, Jack. 1963. Human developmental anatomy. The Ronald Press Company, New York.

Arey, Leslie B. 1946. Developmental anatomy. W. B. Saunders Com­ pany, Philadelphia.

Witschi, Emil. 1956. Development of vertebrates. W. B. Saunders Com­ pany, Philadelphia.

Williams, P. L. and C. P. Wendell-Smith. 1966. J. B. Lippincott Com­ pany, Philadelphia.

Patten, B. M. 1953. Human . 2nd ed. The Blakiston Divi­ sion, McGraw-Hill Book Co., Inc., New York.

Models in this Series

Female reproductive system Pregnant uterus - -28 days Pregnant uterus - -56 days Sperm and fertilization Cleavage Implantation site- -12 days Placentation- -18 days Embryonic membranes - -42 days Embryonic membranes - -56 days Hemisection of term placenta Section of placental villus Embryo- -18 days Embryo- -21 days Embryo- -26 days Embryo- -32 days Embryo, dissected- -26 days Embryo, dissected - -32 days

8 Female Reproductive System 1. Fundus of uterus 2. Corpus of uterus 3. Internal os 4. Endocervical canal 5. External os 6. 7. Endometrium 8. 9. Fornix of vagina 10. Vagina 11. , isthmus 12. Fallopian tube, ampulla 13. Plicae, ampullary endosalpinx 14. Fallopian tube, abdominal orifice 15. Fimbria 16. Ovary 17. 18. 19. 20. Ovarian vessels 21. Morgagni' s hydatid 22. Broad ligament 23. Mackenrodt's ligament (cardinal) 24. Pouch of Douglas 25. Sacrouterine ligament 26. Placenta

Ovogenesis, Fertilization, Cleavage A. Oocyte I. Primary follicle II. Growing follicle III. Graafian follicle B. Ovum C. Sperm 27. Head 28. Body 29. Tail D. Fertilization E. Pronuclei F. First cleavage division G. Two cell H. Eight cell I. Morula J. Blastocyst (4 days) K. Blastocyst (7 days) Placentation, Embryonic Membranes

30. 31. 32. Blood vessels 33. Decidua basalis 34. Syntrophoblast 35. 36. Lacuna 37. Primary mesoderm 38. Yolk sac 39. Operculum 40. Amniotic cavity 41. Exocoelom 42. Body stalk 43. Spiral arteriole 44. Venous sinus 45. Intervillous space 46. Villus 47. Amnion 48. Chorion 49. Umbilical cord 50. Chorion frondosum 51. Chorion laeve 52. Decidua parietalis 53. Decidua capsularis 54. Vein 55. Artery 56. Fetal side 57. Maternal side 58. Villus 59. Margin

Embryo -- External

60. Primitive streak 61. Prochordal plate 62. Head process 63. Notochordal canal 64. Allantoic diverticulum 65. Forebrain 66. Cardiac region 67. Otic placode 68. Somite 69. Neural tube 70. Neural fold 71. Neural groove 10 -. _ " .._..-._..

72 . T ail fold 73. Yolk stalk 74 . Midbra in r egion 75. Hindbr ain region 76. Opt ic bulge 77 . Ot ic bulge 78 . Vi sc er al arch 79. Hepatic r egion 80. T ail 81. Na sal pi t 82. Me s onephric r egio n

Embr yo --Inter nal

i. Forebra in 2. Midbr a in 3. Hindbr ain 4. Spinal c or d 0. Optic ve sicle 6. Otic ve sicle 7. Ma ndibular ar ch 8. Hyoid arch 9. L ung b ud 10. E sop hag us 11. Stom ach 12. Gut 13. L ive r 14. Me s onephros 15. Somite s ] 6. Lef t ventricle ]7. Left au ricle ] 8. Cloaca

] ] Correlated Teaching Aids

A few of the materials which may be used in conjunction with these models are listed below. These items correlate closely with the models and would make a complete teaching unit. Additional materials and prices may be found in our current catalogue.

Preserved Materials

P 1936a - P 1936b Pig embryo in membranes P 2000 - P 2020 Pig embryo cleared and stained for bone study P 3095 Monkey uterus (simplex uterus) P 1845 Rabbit uterus (discoid placenta)

Slides

E 3000 - E 3090 Pig embryos (serial, sagittal, and cross sections) Embryology Set #16 Demonstrates gametogenesis Embryology Set #18 Mammalian ovary H 3930 - H 3945 Rat or mouse placenta (fetal membrane)

Review Sheets

58-3100 Human Development 1. Egg Maturation 58-3102 Human Development 2. Fertilization and Cleavage 58- 3104 Human Development 3. Implantation 58-3106 Human Development 4. Placentation 58-3108 Human Development 5. Fetal Membranes 58-3138 Human Development. 3.5-mm Embryo 58-3140 Human Development. 7-mm Embryo 58-6770 Bone Development 1. Embryonic 58-6772 Bone Development 2. Fetal 58-6774 Bone Development 3. Fetal 58-6776 Human Fetal Skull 58-6800 Human Fetal Circulation

Transparencies

Set No. 82 Mammalian Ovary Set No. 86 Human Fetal Development Set No. 95 Early Pig Development Set No. 100 10 -rnrn Pig Embryo

MD258268 12