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BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 1
2
GametogenesisGametogenesis
• Occurs in the gonads (ovaries and testes)• Meiosis that results in the production of
gametes (haploid) from germ cells (diploid cells)
• Spermatogenesis and Oogenesis
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 2
OogenesisOogenesisand Folliculogenesisand Folliculogenesis
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Oogenesis and Folliculogenesis: WhereOogenesis and Folliculogenesis: Where
• After embryonic production of primary oocytes, egg development is determined by hormone levels during various cycles, beginning with puberty
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 3
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Oogenesis and Folliculogenesis: WhereOogenesis and Folliculogenesis: Where
• Occurs in the ovaries—results in the production of 1 egg (and 3 polar bodies)
• Begins when the female is an embryo—all primary oocytes form before birth and remain “frozen” in this stage indefinitely– Spans all of pre-reproductive & reproductive
life
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 4
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Oogenesis and Folliculogenesis: WhereOogenesis and Folliculogenesis: Where
• Each month after puberty, one primary oocyte completes Meiosis I and begins Meiosis II
• Meiosis II is completed only afterfertilization occurs.
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Oogenesis and Folliculogenesis: WhereOogenesis and Folliculogenesis: Where
• Characterized by unequal division of cytoplasm.
• Why does it make sense for this to happen?– Allows for more nutrients to be available to the
egg in case fertilization occurs.
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 5
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
GERM
INAL
EPI
THEL
IUM
TUNI
CA A
LBUG
INEA
CORT
EX
PRIMORDIAL FOLLICLES
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FolliculogenesisFolliculogenesis
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 6
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
- thin connective tissue capsule underlying germinal epithelium
TUNICA ALBUGINEA
GERMINAL EPITHELIUM
CORTEX- surrounds the medulla and
contains maturing follicles
MEDULLA- central connective tissue
containing vascular supply and nervous innervation
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FEMALE REPRODUCTIVE SYSTEM
• OVARY3 to 5 million OOGONIA differentiate into PRIMARY OOCYTES during early development
OOCYTES becomes surrounded by squamous (follicular) cells to become PRIMORDIAL FOLLICLES
most PRIMORDIAL FOLLICLES undergo atresialeaving 400,000 at birth
oocytes at birth arrested at Meiosis I (prophase)
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 7
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FEMALE REPRODUCTIVE SYSTEM
• OVARYTHREE STAGES OF OVARIAN FOLLICLES CAN BE IDENTIFIED FOLLOWING PUBERTY:(each follicle contains one oocyte)
(1) PRIMORDIAL FOLLICLES- very prevalent; located in the periphery
of the cortex- a single layer of squamous follicular
cells surround the oocyte
(2) GROWING FOLLICLES- three recognizable stages:(a) early primary follicle(b) late primary follicle(c) secondary (antral) follicle
(3) MATURE (GRAAFIAN) FOLLICLES- follicle reaches maximum size
OOGE
NESI
S
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FEMALE REPRODUCTIVE SYSTEM
• OVARIAN FOLLICLES
(1) PRIMORDIAL FOLLICLES(2) GROWING FOLLICLES
(a) early primary follicle- follicular cells still unilaminar but now are cuboidal in appearance- oocyte begins to enlarge
(b) late primary follicle- multilaminar follicular layer; cells now termed granulosa cells- zona pellucida appears; gel-like substance rich in GAGs - surrounding stromal cells differentiate into theca
interna and theca externa(b) secondary (antral) follicle
- cavities appear between granulosa cells forming an antrum- follicle continues to grow - formation of cumulus oophorus and corona radiata
(3) MATURE (GRAAFIAN) FOLLICLES
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 8
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FEMALE REPRODUCTIVE SYSTEM
• OVARY OVARY H&E
PRIMORDIAL FOLLICLES
EARLY 1º
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Primordial FolliclePrimordial Follicle
Primary FolliclePrimary Follicle
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 9
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Secondary FolliclesSecondary Follicles
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Tertiary FollicleTertiary Follicle
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 10
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Graafian FolliclesGraafian Follicles
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Ovulatory Follicle
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 11
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
CORPUS LUTEUM
CORTEXMEDULLA
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FEMALE REPRODUCTIVE SYSTEM
• OVARY OVARY H&E
CORPUS ALBICANS
EARLY PRIMARY FOLLICLES
• OVARY
PRIMORDIAL FOLLICLE
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 12
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OocytesOocytes
Bovine cumulus-oocyte complex (COC) with compact layers of cumulus cells at the beginning of in vitro maturation
Bovine cumulus-oocyte complex (COC) with expanded layers of cumulus cells after 24h of in vitro maturation
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Cumulus oophorusCumulus oophorus
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 13
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FEMALE REPRODUCTIVE SYSTEM
• OVARIAN FOLLICLES
GRANULOSA (FOLLICULAR) CELLS
ZONA PELLUCIDA
OOCYTE
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Corona radiata
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 14
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Zona Pellucida
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
GERM
INAL
EPI
THEL
IUM
TUNI
CA A
LBUG
INEA
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 15
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
LATE PRIMARY FOLLICLEmultilaminar
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FEMALE REPRODUCTIVE SYSTEM
• OVARY
MATURE (GRAAFIAN) FOLLICLE
cumulus oophoruscorona radiatatheca interna and externa
zona pellucida
theca interna cells begin to produce androgens that are converted to estrogens
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 16
SpermatogenesisSpermatogenesis
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SpermatogenesisSpermatogenesis
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 17
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Spermatogenesis: WhereSpermatogenesis: Where• Happens in
seminiferous tubules, which make up each testicle
• Mature in the epididymis and gain motility
• Produced constantly after puberty
• Takes 65 to 70 days
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 18
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Spermatogenesis: HowSpermatogenesis: How
• Diploid spermatogonia are located on outer wall of seminiferous tubules
• These increase in number via mitosis
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Spermatocytogenesis (Mitosis)Spermatocytogenesis (Mitosis)Step 1Step 1
• Spermatogonia (Stem cells) form Primary Spermatocytes
• Involves 6 Mitotic Divisions• Primary Spermatocytes are still Diploid• Testosterone driven
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 19
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Spermatogenesis: HowSpermatogenesis: How
• The spermatogonia grow larger and become primary spermatocytes
• Notice their location: closer to the inside of the tubule
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Spermatogenesis: HowSpermatogenesis: How
• Primary spermatocytes undergo meiosis I to produce two secondary spermatocytes (haploid)
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 20
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Meiotic Divisions (Two)Meiotic Divisions (Two)Step 2Step 2
® Reduction in chromosome number from Diploid to Haploid
23Humans
32Horses
27Sheep
30Cattle/goats
Chromosome No. Haploid
Species
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Spermatogenesis: HowSpermatogenesis: How
• Secondary spermatocytes undergo meiosis II to produce 2 spermatids (haploid)
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 21
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Spermiogenesis (Maturation)Spermiogenesis (Maturation)Step 3Step 3
• Metamorphosis of Spermatid into sperm• No divisions involved• Changes are primarily in cytoplasm• FSH driven – Sertoli – Nurse cell
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Spermiogenesis: Spermatids to SpermSpermiogenesis: Spermatids to Sperm
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 22
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Spermatogenesis: HowSpermatogenesis: How
• Spermatids are aided in their maturity process by Sertoli cells (nurse cells)
• This helps the cells to differentiate
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Spermatogenesis: HowSpermatogenesis: How
• Sperm cells eventually detach from the Sertoli cells and are carried out by fluid in the lumen of the seminiferous tubules
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 23
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Sperm cell: structureSperm cell: structure
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Sperm cell: structureSperm cell: structure
• The midpiece contains lots of mitochondria—why?– Sperms have a long journey → they need a lot
of energy (hence the need for lots of mitochondria)
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 24
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Stages in SpermatogenesisStages in Spermatogenesis
Spermatogonia
Primary Spermatocyte
Secondary Spermatocyte
Spermatid
60 days total Sperm+ 10 days to travel through Epididymus
29 days
15 days Mitosis
15 days Meiosis I
1 day Meiosis II
60 ch; n = 1
30 ch; n = 256
n = 128
60 ch; n = 64
30 ch; n = 256
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EpididymusEpididymus
•• Day 60 Day 60 –– TestesTestes® Spermatozoa (sperm) are immature® Has Cytoplasmic Droplet® Located in the Testes
•• Day 70 Day 70 –– EpididymusEpididymus® Spermatozoa (sperm) are now mature® Cytoplasmic Droplet removed® Sperm are motile® Stored in tail of Epididymus
BIOLOGI - ACHADIAH RACHMAWATI
GAMETOGENESIS 25
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Comparison ofComparison ofOogenesis and SpermatogenesisOogenesis and Spermatogenesis
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Thank YouThank You