组织胚胎学课件组织胚胎学课件 中国医科大学 基础医学院 组胚 — 英文教学组

HUMAN HUMANEMBRYOLOGY Department of Histology and Embryology China Medical University China Medical University

Chapter 3 First Week of Development: Ovulation to Implantation Chapter 3 First Week of Development: Ovulation to Implantation

Ovarian Cycle At puberty, the female begins to undergo regular monthly cycles. These sexual cycles are controlled by the HPG (Hypothalamus-Pituitary-Gonad) axis. (Hypothalamus-Pituitary-Gonad) axis. GnRH, Gonadotropin, follicle-stimulating hormone (FSH) luteinizing hormone (LH) /ICSH

At the beginning of each ovarian cycle, 15 to 20 primary (preantral) follicles are stimulated to grow under the influence of FSH. At the beginning of each ovarian cycle, 15 to 20 primary (preantral) follicles are stimulated to grow under the influence of FSH. Under normal conditions, only one of these follicles reaches full maturity, and only one oocyte is discharged; the others degenerate and become atretic. Under normal conditions, only one of these follicles reaches full maturity, and only one oocyte is discharged; the others degenerate and become atretic. When a follicle becomes atretic, the oocyte and surrounding follicular cells degenerate and are replaced by connective tissue, forming the interstitial gland (corpus atreticum). When a follicle becomes atretic, the oocyte and surrounding follicular cells degenerate and are replaced by connective tissue, forming the interstitial gland (corpus atreticum).

Granulosa and thecal cells produce estrogens that (a) cause the uterine endometrium to enter the follicular or proliferative phase; Granulosa and thecal cells produce estrogens that (a) cause the uterine endometrium to enter the follicular or proliferative phase; (b) cause thinning of the cervical mucus to allow passage of sperm; (c) stimulate the pituitary gland to secrete LH.

At mid-cycle, there is an LH surge that (a) causes oocytes to complete meiosis I and initiate meiosis II; (b) stimulates production of progesterone by follicular stromal cells (luteinization); (c) causes follicular rupture and ovulation.

Ovulation

The process that the mature follicle ruptures and the secondary oocyte, zona pellucida, corona radiata and follicular fluid are released from the ovary is called ～. : Time: ovulation takes place at about the. middle of the cycle. Ovulation

after ovulation The fate of the secondary oocyte after ovulation Degeneration undergoes if no fertilization occurs.Degeneration undergoes if no fertilization occurs. If fertilization happens ， the second meiosis is finished, and the ovum forms.If fertilization happens ， the second meiosis is finished, and the ovum forms.

FATE 1 FATE 2

After ovulation, granulosa cells remaining in the wall of the ruptured follicle, together with cells from the theca interna, are vascularized by surrounding vessels. Under the influence of LH, these cells develop a yellowish pigment and change into luteal cells, which form the corpus luteum Corpus Luteum

GRANULOSA LUTEIN CELLS THECA LUTEIN CELLS

Cells of corpus luteum Granulosa lutein C ： progesterone and relaxin Theca lutein C ： estrogen Progesterone, together with estrogen, causes the uterine mucosa to enter the progestational or secretory stage in preparation for implantation of the embryo.

Fate of corpus luteum Corpus luteum of menstruation →corpus albicans Corpus luteum of menstruation →corpus albicans Corpus luteum of pregnancy →corpus albicans Corpus luteum of pregnancy →corpus albicans

Corpus albicans

Relation of fimbriae and ovary. Fimbriae collect the oocyte and sweep it into the uterine tube.

FertilizationFertilization --- Fertilization is the process in which the male and female gametes (sperm and ovum) unite to give rise to a zygote. ---place: in the ampulla of the uterine tube --- Fertilization is the process in which the male and female gametes (sperm and ovum) unite to give rise to a zygote. ---place: in the ampulla of the uterine tube

Conditions of fertilization: 1) maturation of oocyte 2) maturation of spermatozoa: 2-3 weeks in the ductus epididymis acquire some motility Conditions of fertilization: 1) maturation of oocyte 2) maturation of spermatozoa: 2-3 weeks in the ductus epididymis acquire some motility

decapacitation factor: exist in epididymis, to inhibit the release of acrosome enzymes capacitation factor: secreted by epi. cells of oviduct, capacity of releasing acrosome enzymes decapacitation factor: exist in epididymis, to inhibit the release of acrosome enzymes capacitation factor: secreted by epi. cells of oviduct, capacity of releasing acrosome enzymes capacitation of spermatozoa

3 )quality and quantity of spermatozoa: normal: 3-4 ml, 100,000,000/ml, abnormal: <1.5 ml; or <10,000,000/ml; abnormal sperm >30%; mobility < 70% 4) meeting of sperm and ovum sperm: <4 days ovum: < 2 days 3 )quality and quantity of spermatozoa: normal: 3-4 ml, 100,000,000/ml, abnormal: <1.5 ml; or <10,000,000/ml; abnormal sperm >30%; mobility < 70% 4) meeting of sperm and ovum sperm: <4 days ovum: < 2 days

processes of fertilization: 1) acrosome reaction: A. hyaluronic acidase: dissolve corona radiata B. interact with ZP3(receptor glycoprotein, exist in zona pellucida) molecules, release acrosin: dissolve zona pellucida then some spermatozoa enter perivitelline space processes of fertilization: 1) acrosome reaction: A. hyaluronic acidase: dissolve corona radiata B. interact with ZP3(receptor glycoprotein, exist in zona pellucida) molecules, release acrosin: dissolve zona pellucida then some spermatozoa enter perivitelline space

2) only one spermatozoon fuse with membrane of the ovum: nucleus enter cytoplasm of the ovum cortical reaction: cortical granules (located in cytoplasm of ovum) are released into perivitelline space, and cause zona reaction: change of ZP3 molecules in zona pellucide 2) only one spermatozoon fuse with membrane of the ovum: nucleus enter cytoplasm of the ovum cortical reaction: cortical granules (located in cytoplasm of ovum) are released into perivitelline space, and cause zona reaction: change of ZP3 molecules in zona pellucide

3) formation of zygote (fertilized ovum) A. secondary meiosis complete: form second polar body B. male pronucleus fuse with female pronucleus to restore 2N chromosomes

significance of fertilization: 1) a new life begin(initiation of cleavage) 2) restoration of the diploid number of chromosomes 3) determination of the sex of the new individual: ovum(22+X) + X-bearing spermatozoon = girl ovum(22+X) + Y-bearing spermatozoon = boy significance of fertilization: 1) a new life begin(initiation of cleavage) 2) restoration of the diploid number of chromosomes 3) determination of the sex of the new individual: ovum(22+X) + X-bearing spermatozoon = girl ovum(22+X) + Y-bearing spermatozoon = boy

Blastocyst formation and implantation

2-cell stage8-cell stage4-cell stage morula Early blastocystLate blastocyst

1) cleavage and blastocyst formation ① cleavage: mitosis of the zygote ---blastomere: cells from cleavage 30h: 2 cells 40h: 4 cells 72h: cells – morula formation 1) cleavage and blastocyst formation ① cleavage: mitosis of the zygote ---blastomere: cells from cleavage 30h: 2 cells 40h: 4 cells 72h: cells – morula formation

② formation of blastocyst: by 5 th day, blastomere reach to 107, small space appear between them blastocoele: filled with liquid trophoblast inner cell mass (embryoblast ) polar trophoblast ② formation of blastocyst: by 5 th day, blastomere reach to 107, small space appear between them blastocoele: filled with liquid trophoblast inner cell mass (embryoblast ) polar trophoblast inner cell mass blastocoele trophoblast Zona pellucida Polar trophoblast Early blastocyst late blastocyst

2) Implantation definition: the process in which the blastocyst is embedded in endometrium of the uterus time: begin on the 5 th –6 th day; finish on the 11 th –12 th day place: fundus and body of uterus 2) Implantation definition: the process in which the blastocyst is embedded in endometrium of the uterus time: begin on the 5 th –6 th day; finish on the 11 th –12 th day place: fundus and body of uterus

process: zona pellucide disappear → polar trophoblast touch the endometrium→secrete proteolytase →dissolve the endothelium → embedded into endometrium →coagulation plug seal the space

* trophoblast become into two layers when blastocyst is embedding into endometrium syncytiotrophoblast cytotrophoblast * trophoblast become into two layers when blastocyst is embedding into endometrium syncytiotrophoblast cytotrophoblast endometrium Columnar epithelium

A 7.5-day human blastocyst, partially embedded in the endometrial stroma. The trophoblast consists of an inner layer with mononuclear cells, the cytotrophoblast, and an outer layer without distinct cell boundaries, the syncytiotrophoblast. The embryoblast is formed by the ectoderm and endoderm. The amniotic cavity appears as a small cleft. ectoderm endoderm

decidual response of endometrium stroma cell → predecidual cell → decidual cell (cell become larger and rich in glycogen and lipid droplets) decidual response of endometrium stroma cell → predecidual cell → decidual cell (cell become larger and rich in glycogen and lipid droplets)

endometrium →decidua: decidua basalis decidua capsularis decidua parietalis Conditions of implantation: - endometrium is in secretory phase - morula reach the cavity of uterus on time - zona pellucide disappears in time endometrium →decidua: decidua basalis decidua capsularis decidua parietalis Conditions of implantation: - endometrium is in secretory phase - morula reach the cavity of uterus on time - zona pellucide disappears in time

Relationship between the embryo and the endometrium Decidua capsularis embryo vagina cervix Uterine cavity Decidua parietalis Decidua basalis

Question s 1.What is ovulation ？ 2.What is corpus luteum? Classification and its fate? 3.What’s fertilization? Describe the time, position, process and significance of the fertilization. process and significance of the fertilization. 4.Describe the cleavage and formation of blastocyst. 5.Describe the definition, time and place of implantation. 6.Classification of trophoblast. 7.Classification of decidua. 8.Preview further development of embryo.