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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


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


GAMETOGENESIS 3

5

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• 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


GAMETOGENESIS 4

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• 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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• 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.


GAMETOGENESIS 5

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FEMALE REPRODUCTIVE SYSTEM

• OVARY

GERM

INAL

EPI

THEL

IUM

TUNI

CA A

LBUG

INEA

CORT

EX

PRIMORDIAL FOLLICLES

10

FolliculogenesisFolliculogenesis


GAMETOGENESIS 6

11


• 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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• 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)


GAMETOGENESIS 7

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• 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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• 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 folliclemultilaminar 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


GAMETOGENESIS 8

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• OVARY OVARY H&E

PRIMORDIAL FOLLICLES

EARLY 1º

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Primordial FolliclePrimordial Follicle

Primary FolliclePrimary Follicle


GAMETOGENESIS 9

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Secondary FolliclesSecondary Follicles

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Tertiary FollicleTertiary Follicle


GAMETOGENESIS 10

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Graafian FolliclesGraafian Follicles

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Ovulatory Follicle


GAMETOGENESIS 11

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• OVARY

CORPUS LUTEUM

CORTEXMEDULLA

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• OVARY OVARY H&E

CORPUS ALBICANS

EARLY PRIMARY FOLLICLES

• OVARY

PRIMORDIAL FOLLICLE


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


GAMETOGENESIS 13

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• OVARIAN FOLLICLES

GRANULOSA (FOLLICULAR) CELLS

ZONA PELLUCIDA

OOCYTE

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Corona radiata


GAMETOGENESIS 14

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Zona Pellucida

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• OVARY

GERM

INAL

EPI

THEL

IUM

TUNI

CA A

LBUG

INEA


GAMETOGENESIS 15

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• OVARY

LATE PRIMARY FOLLICLEmultilaminar

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• OVARY

MATURE (GRAAFIAN) FOLLICLE

cumulus oophoruscorona radiatatheca interna and externa

zona pellucida

theca interna cells begin to produce androgens that are converted to estrogens


GAMETOGENESIS 16

SpermatogenesisSpermatogenesis

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SpermatogenesisSpermatogenesis


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


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


GAMETOGENESIS 19

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• The spermatogonia grow larger and become primary spermatocytes

• Notice their location: closer to the inside of the tubule

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• Primary spermatocytes undergo meiosis I to produce two secondary spermatocytes (haploid)


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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• Secondary spermatocytes undergo meiosis II to produce 2 spermatids (haploid)


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


GAMETOGENESIS 22

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• Spermatids are aided in their maturity process by Sertoli cells (nurse cells)

• This helps the cells to differentiate

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• Sperm cells eventually detach from the Sertoli cells and are carried out by fluid in the lumen of the seminiferous tubules


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)


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


GAMETOGENESIS 25

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Comparison ofComparison ofOogenesis and SpermatogenesisOogenesis and Spermatogenesis

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Thank YouThank You

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