EMBRYOLOGY
-studies human development, that begins at fertilisation, roughly 14 days from last normal period.
-process begins whe sperm penetrates an oocyte= zygote, first week
-embryonic period: first 8 weeks.
-fetal period: begins at week 9.
-most visible advances from week 3 to 8
Reproductive Organs:
Produce and transport germ cells (gametes) from gonads to site of fertilisation (uterine tubes – ampulla)
-vagina: excretory passage, sexual intercourse, inferior part of the birth canal
-uterus: pear-shaped, 2 parts:
- Body: superior 2/3
- Cervix: cylindrical inferior third
Uterus: wall of the body consists of 3 layers:
- Perimetrium: thin external peritoneal layer
- Myometrium: thick, smooth muscle layer
- Endometrium: internal layer composed of:
- Compact layer: densely packed connective tissue around the neck of uterine gland.
- Spongy layer: highly vascularised connective tissue, containing dilated uterine glands
- Basal layer containing blind end of uterine glands
Gametogenesis
-formation of germ cells, spermatogenesis and oogenesis
-sperms and oocytes are highly specialised germ cells (23 ch)
Spermatogenesis:
-primordial germ cells PGC derive from epiblast (blastoderm).
-remain dormant from week 6 of embryo development until puberty
-Primordial sperms (spermatogonia) remain dormant in seminiferous tubules of testis
-after puberty: increase in number with mitosis, sperms grow and change= primary spermatogenesis
-each primary spermatocyte undergoes a meiotic division= 2 haploid secondary spermatocytes, half the size of the
primary
-second meiotic division= spermatica, half size
-when it is complete, sperms enter the lumen of seminiferous tubules.
-move to epididymis (there stored and become functionally mature)
-spermatogenesis take 2 months
-continues through all reproductive life
Primordial Germ Cells reside in Yolk Sac: cells that give rise to gametes in M and F are in the yolk sac during 4 to 6
weeks (extraembryonic mb).
-Primordial germ cells lineage: germ line (cells that form gametes)
-mature sperm cell:
-acrosome: contains enzymes that facilitate sperm penetration of zona pellucida
-move from seminiferous tubules to epidydimus
-at puberty, testosterone secretion stimulates development of sex characteristics, triggers growth of testes,
maturation of seminiferous tubules, spermatogenesis.
-Sertoli cells differentiate into seminiferous tubules.
-dormant PGCs resume development, divide several times by mitosis, differentiate into spermatogonia
-spermatogonia are under the basement membrane surrounding seminiferous tubules.
-adiacent Sertoli cells are interconnected by tight junctions= helps establish blood-testis Barrie’s (testes in immune
privilege) —> developing spermatogonia residue within an immune site during development
,-anterior 2/3 of head covered by acrosome, cap-like organelle containing enzymes that facilitate sperm penetration
during fertilisation.
-tail provides motility, consists of 3 parts:
- Middle piece: contains mitochondria, fuel tail movements. HOX genes
- Principal piece
- End piece
Capacitation: terminal step of functional maturation
-changes in the acrosome to prepare it to release enzymes (zona pellucida penetration – shell of glycoprotein around
oocyte).
-takes place in female genital tract (requires contact with oviduct)
-spermatozoa in vitro fertilisation is artificially capacitated.
-spermatozoa with defective acrosome is injected in oocyte
-media of calcium ions, bicarbonate, serum albumin to help process in vitro
Oogenesis:.
-fetal period: oogonia proliferate by mitosis and enlarge= primary oocytes
-at birth all primary oocytes completed prophase of first meiotic division, uniti puberty
-before ovulation, a primary oocyte completes the first meiotic division
-unequal cytoplasm division (polar body, soon degenerates)
-secondary oocyte receives most of of the cytoplasm
-at ovulation, nucleus of secondary oocyte begins second meiotic division.
-if there’s fertilisation, second meiotic division is completed and a II polar body is formed
-secondary oocyte visible by eye
-2.000.000 primary oocytes are present in ovaries of neonate
-most regress during childhood, by puberty 40.000 remain
-400 oocytes mature into secondary oocytes and reach ovulation—> 32 year of ovulation, 50 years menopause
-2 kind of sperms: 22 autosomes + X or Y (only one oocyte) —> sex determination
-after PGC enter the genital ridge they stop migration and undergo 2 or 3 mitosis and enter pre-meiotic stage.
- Males: PGCs arrest at week 6 (genital ridge has male meiosis inhibitor produced by Sertoli cells)
- Females: PGCs enter meiotic prophase as primary oocytes at month 5
Ovarian Cycle: development of mature follicle, followed by ruptures and oocyte expelling for fertilisation
Ovarian Follicles:
Before puberty, all follicles of the ovarian cortex are in primordial follicle stage.
-pulsation release of GnRH from hypothalamus results in pulsatile release of gonadotropins: FSH and LH
-follicular development culminates in release of a single oocyte.
-ovarian follicles: primary oocyte + associated follicular cells
4 differentiation stages of follicular development from Primordial follicles:
- Unilaminar
- Multilaminar primary follicles
- Secondary/antral follicles
- Graafian/mature follicles
, Development of primordial and primary follicels is indipendent of FSH,
-differentiation and proliferation of follicular cells triggered by uncharacterised local factors secreted by ovary cells.
-secondary and later follicles are under FSH influence.
Primary Follicles:
-grows about 100/150 microm in diameter with an enlarged nucleus.
-follicular cells become cuboidal – unilaminar primary follicle
-follicular cells proliferate and stratify= several layers around primary oocyte= Multilaminar primary follicle
-follicular cells are now referred as granulosa cells.
-theca interna cells produce androstenedione, male sex hormone= enters granulosa cells, converted by aromatase
into estrogen/estradiol.
-amorphous substance/zona pellucida appears, separating oocyte from follicular cells.
-stromatolites/granulosa cells form theca interna: richly vascularised cellular layer, and theca externa: fibrous
connective tissue.
Secondary Follicles:
-like primary follicles, but there’s accumulation of liquor folliculi among granulosa cells
-continued proliferation of granulosa cells of 2 nd depends on FSH release by basophil cells of anterior pituitary.
-during ovulation, surge in LH production from basophil cells allows discharge of mature oocyte, ready for
fertilisation
-follicle undergoes atresia, granulosa cells change to granulosa lutein and theca lutein:form corpus luteum (produces
progesterone).
-angiogenic factor *
Ovulation:
Follicular cells divide actively forming an antrum, contains follicular fluid= follicle can now be called 2 nd
-primary oocyte surrounded by follicular cells, corona radiata, that project into enlarged antrum.
-follicle continues to enlarge= forms bulge on surface of ovary
-small, oval, a vascular spot, the stigma, appears on the bulge
-before ovulation, secondary oocyte and some cells of the cumulus oophorus detach from the interior of the
distended follicle.
-expelled secondary oocyte is surrounded by zona pellucida, acellular glycoprotein coat + layers of follicular cells=
corona radiata and cumulus oophorus
-hour 20: ch are lined in metaphase (2 nd oocyte and first polar body)
-secondary oocyte begins meiotic division, 3 hours before ovulation its arrested at 2 nd meiotic metaphase
-ovulation. 24-36 hours after surge of LH (result of signalling molecules from granulosa cells)
-surge elicited by high estrogen level in blood
-causes stigma to rupture, expelling secondary oocyte with follicular fluid
-plasmids and MMPs appear to control over stigma rupture
Corpus Luteum;
-under LH influence, walls of follicle develop into endocrine glandular structure=corpus luteum (secretes primary
progesterone and some estrogen)
-if oocyte is fertilised, c.l. Enlarges= corpus luteum of pregnancy, increases its hormone production.
-degeneration of corpus luteum is prevented by human chorionic gonadotropin hCG.
-oocyte isn’t fertilised: corpus luteum degenerates 10-12 days after ovulation.
-degenerated corpus luteum is transformed into white scar tissue in ovary= corpus albicans
-oocytes are fertilised within 12 hours of ovulation, after 24 hours they cant anymore and they degrade.
-sperms generally don’t survive 24 hours in female genital tract.
-sperms are captured in the folds of the cervix mucosa and released into cervical canal, pass though uterus body and
into uterine tubes.
Fertilisation:
-studies human development, that begins at fertilisation, roughly 14 days from last normal period.
-process begins whe sperm penetrates an oocyte= zygote, first week
-embryonic period: first 8 weeks.
-fetal period: begins at week 9.
-most visible advances from week 3 to 8
Reproductive Organs:
Produce and transport germ cells (gametes) from gonads to site of fertilisation (uterine tubes – ampulla)
-vagina: excretory passage, sexual intercourse, inferior part of the birth canal
-uterus: pear-shaped, 2 parts:
- Body: superior 2/3
- Cervix: cylindrical inferior third
Uterus: wall of the body consists of 3 layers:
- Perimetrium: thin external peritoneal layer
- Myometrium: thick, smooth muscle layer
- Endometrium: internal layer composed of:
- Compact layer: densely packed connective tissue around the neck of uterine gland.
- Spongy layer: highly vascularised connective tissue, containing dilated uterine glands
- Basal layer containing blind end of uterine glands
Gametogenesis
-formation of germ cells, spermatogenesis and oogenesis
-sperms and oocytes are highly specialised germ cells (23 ch)
Spermatogenesis:
-primordial germ cells PGC derive from epiblast (blastoderm).
-remain dormant from week 6 of embryo development until puberty
-Primordial sperms (spermatogonia) remain dormant in seminiferous tubules of testis
-after puberty: increase in number with mitosis, sperms grow and change= primary spermatogenesis
-each primary spermatocyte undergoes a meiotic division= 2 haploid secondary spermatocytes, half the size of the
primary
-second meiotic division= spermatica, half size
-when it is complete, sperms enter the lumen of seminiferous tubules.
-move to epididymis (there stored and become functionally mature)
-spermatogenesis take 2 months
-continues through all reproductive life
Primordial Germ Cells reside in Yolk Sac: cells that give rise to gametes in M and F are in the yolk sac during 4 to 6
weeks (extraembryonic mb).
-Primordial germ cells lineage: germ line (cells that form gametes)
-mature sperm cell:
-acrosome: contains enzymes that facilitate sperm penetration of zona pellucida
-move from seminiferous tubules to epidydimus
-at puberty, testosterone secretion stimulates development of sex characteristics, triggers growth of testes,
maturation of seminiferous tubules, spermatogenesis.
-Sertoli cells differentiate into seminiferous tubules.
-dormant PGCs resume development, divide several times by mitosis, differentiate into spermatogonia
-spermatogonia are under the basement membrane surrounding seminiferous tubules.
-adiacent Sertoli cells are interconnected by tight junctions= helps establish blood-testis Barrie’s (testes in immune
privilege) —> developing spermatogonia residue within an immune site during development
,-anterior 2/3 of head covered by acrosome, cap-like organelle containing enzymes that facilitate sperm penetration
during fertilisation.
-tail provides motility, consists of 3 parts:
- Middle piece: contains mitochondria, fuel tail movements. HOX genes
- Principal piece
- End piece
Capacitation: terminal step of functional maturation
-changes in the acrosome to prepare it to release enzymes (zona pellucida penetration – shell of glycoprotein around
oocyte).
-takes place in female genital tract (requires contact with oviduct)
-spermatozoa in vitro fertilisation is artificially capacitated.
-spermatozoa with defective acrosome is injected in oocyte
-media of calcium ions, bicarbonate, serum albumin to help process in vitro
Oogenesis:.
-fetal period: oogonia proliferate by mitosis and enlarge= primary oocytes
-at birth all primary oocytes completed prophase of first meiotic division, uniti puberty
-before ovulation, a primary oocyte completes the first meiotic division
-unequal cytoplasm division (polar body, soon degenerates)
-secondary oocyte receives most of of the cytoplasm
-at ovulation, nucleus of secondary oocyte begins second meiotic division.
-if there’s fertilisation, second meiotic division is completed and a II polar body is formed
-secondary oocyte visible by eye
-2.000.000 primary oocytes are present in ovaries of neonate
-most regress during childhood, by puberty 40.000 remain
-400 oocytes mature into secondary oocytes and reach ovulation—> 32 year of ovulation, 50 years menopause
-2 kind of sperms: 22 autosomes + X or Y (only one oocyte) —> sex determination
-after PGC enter the genital ridge they stop migration and undergo 2 or 3 mitosis and enter pre-meiotic stage.
- Males: PGCs arrest at week 6 (genital ridge has male meiosis inhibitor produced by Sertoli cells)
- Females: PGCs enter meiotic prophase as primary oocytes at month 5
Ovarian Cycle: development of mature follicle, followed by ruptures and oocyte expelling for fertilisation
Ovarian Follicles:
Before puberty, all follicles of the ovarian cortex are in primordial follicle stage.
-pulsation release of GnRH from hypothalamus results in pulsatile release of gonadotropins: FSH and LH
-follicular development culminates in release of a single oocyte.
-ovarian follicles: primary oocyte + associated follicular cells
4 differentiation stages of follicular development from Primordial follicles:
- Unilaminar
- Multilaminar primary follicles
- Secondary/antral follicles
- Graafian/mature follicles
, Development of primordial and primary follicels is indipendent of FSH,
-differentiation and proliferation of follicular cells triggered by uncharacterised local factors secreted by ovary cells.
-secondary and later follicles are under FSH influence.
Primary Follicles:
-grows about 100/150 microm in diameter with an enlarged nucleus.
-follicular cells become cuboidal – unilaminar primary follicle
-follicular cells proliferate and stratify= several layers around primary oocyte= Multilaminar primary follicle
-follicular cells are now referred as granulosa cells.
-theca interna cells produce androstenedione, male sex hormone= enters granulosa cells, converted by aromatase
into estrogen/estradiol.
-amorphous substance/zona pellucida appears, separating oocyte from follicular cells.
-stromatolites/granulosa cells form theca interna: richly vascularised cellular layer, and theca externa: fibrous
connective tissue.
Secondary Follicles:
-like primary follicles, but there’s accumulation of liquor folliculi among granulosa cells
-continued proliferation of granulosa cells of 2 nd depends on FSH release by basophil cells of anterior pituitary.
-during ovulation, surge in LH production from basophil cells allows discharge of mature oocyte, ready for
fertilisation
-follicle undergoes atresia, granulosa cells change to granulosa lutein and theca lutein:form corpus luteum (produces
progesterone).
-angiogenic factor *
Ovulation:
Follicular cells divide actively forming an antrum, contains follicular fluid= follicle can now be called 2 nd
-primary oocyte surrounded by follicular cells, corona radiata, that project into enlarged antrum.
-follicle continues to enlarge= forms bulge on surface of ovary
-small, oval, a vascular spot, the stigma, appears on the bulge
-before ovulation, secondary oocyte and some cells of the cumulus oophorus detach from the interior of the
distended follicle.
-expelled secondary oocyte is surrounded by zona pellucida, acellular glycoprotein coat + layers of follicular cells=
corona radiata and cumulus oophorus
-hour 20: ch are lined in metaphase (2 nd oocyte and first polar body)
-secondary oocyte begins meiotic division, 3 hours before ovulation its arrested at 2 nd meiotic metaphase
-ovulation. 24-36 hours after surge of LH (result of signalling molecules from granulosa cells)
-surge elicited by high estrogen level in blood
-causes stigma to rupture, expelling secondary oocyte with follicular fluid
-plasmids and MMPs appear to control over stigma rupture
Corpus Luteum;
-under LH influence, walls of follicle develop into endocrine glandular structure=corpus luteum (secretes primary
progesterone and some estrogen)
-if oocyte is fertilised, c.l. Enlarges= corpus luteum of pregnancy, increases its hormone production.
-degeneration of corpus luteum is prevented by human chorionic gonadotropin hCG.
-oocyte isn’t fertilised: corpus luteum degenerates 10-12 days after ovulation.
-degenerated corpus luteum is transformed into white scar tissue in ovary= corpus albicans
-oocytes are fertilised within 12 hours of ovulation, after 24 hours they cant anymore and they degrade.
-sperms generally don’t survive 24 hours in female genital tract.
-sperms are captured in the folds of the cervix mucosa and released into cervical canal, pass though uterus body and
into uterine tubes.
Fertilisation:
