Introduction

Dr. Sherif Fahmy

Dr. Sherif Fahmy

THE BEGINING

Dr. Sherif Fahmy

Gametogenesis• It is the process by which

mature gametes (Sperm or Ovum) are formed from primitive germ cells.

Dr. Sherif Fahmy

Aim of Gametogenesis

Production of mature male and female gametes with the following changes:Nucleus: reduction of diploid number (46 chromosomes) into haploid number (23 chromosomes).Cytoplasm: Increase in size in ova and markedly reduced in sperms.

Two Types of Divisions Occur During Gametogenesis

•1- Mitotic division.•2- Meiotic division.

MITOTIC DIVISION

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MEIOTIC DIVISION

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Where and when Sperm or Ovum

are formed?

Sperm Ovum

Where In seminepherou tubules and epididymis

In cortex of ovary and fallopian tube

When From puberety till old age.

From intra-uterine life then arrested and completed from puberty to menopause.

Gametogenesis

MALE GENITAL SYSTEM

Dr. Sherif Fahmy

Seminepherous tubules

Epididymis

FEMALE GENITAL SYSTEM

Dr. Sherif Fahmy

Ovary

Uterine tube

Uterus

Vagina

Source of Primitive Germ Cells

- Primitive germ cells appear at caudal part of yolk sac at the 2nd week.

- Then they migrate to reach developing gonads (testis in male & ovary in female) at the 5th week.

- In males: Primitive germ cells will fill and block seminephrous tubules in testis and named spermatogonia.

- In females: Primitive germ cells will be present in cortex of ovary and named oogonia.

Source of primordial germ cells

Spermatogenesis

Spermatogenesis• It is the process by which sperms are formed

from primitive germ cells.• Site: in seminephrous tubules in testis and epididymis.• Time: starting at puberty and continues till old age.

• Aim: 1- Reduction of diploid to haploid number of

chromosomes.2- Determination of sex of sperms.3- Giving the sperms the ability to move and fertilize

the ovum.

Stages of Spermatogenesis

•A- Spermatocytogenesis.•B- Spermiogenesis.

A- Spermato-cytogenesis

Stem spermatogonial cells(46 ch)

Sertoli cells

Spermatogonia A (46 ch)Spermatogonia B (46 ch)

Primary spermatocyte (46 ch)

Secondary spermatocytes (23 ch)

4 sperematids (23 ch)

SpermsSummary of spermatogenesis

Wall of seminephrous tubule

Ist meiotic

2nd meiotic

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B- Spermio-genesis

Spermatid

Sperm

Nucleus

Golgi apparatus

Mitochondria

Shedding of cytoplasm

Centriol

Axila filament

Acrosomal cap

Seminepherous tubules

Abnormal forms of sperms

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Oogenesis

FEMALE GENITAL SYSTEM

Dr. Sherif Fahmy

Ovary

Uterine tube

Uterus

Vagina

Oogenesis: It is a process by which mature ovum is formed from primitive germ cell (oogonium).Site: in cortex of ovary.Time: Starting in intrauterine life and then arrested till puberty when it continues till menopause.Aim: 1- Reduction of diploid to haploid number.2- Storage of cytoplasm.3- Contains only X-chromosome.

• Oogenesis passes into 3 stages:1- Before birth.2- At birth.3- From puberty to menopause (ovarian cycle).

Before Birth (Intrauterine life)At 3rd month:-Mitotic divisions of oogonia (46 ch,XX) to increase the number.At the 5th month: the count reaches 7 millions in both ovaries.Till birth:Then most of oogonia degenerate, reducing the count.-the remaining oogonia enlarge to form primary oocytes (46 ch,XX).-Each primary oocyte starts 1st meiotic division and arrested then becomes surrounded by follicular cells to form Primordial follicles.

Primary oocytes arrested in 1st meiotic division

Single layer of follicular cells

At birth ovaries contain only primordial follicles (primary oocytes arrested in 1st meiotic division) surrounded with a layer of follicular cells

At birth (In the cortex of ovary)

At Puberty

FSH & LHovarian cycle .

menstrual cycle.Esterogen & Progesterone

Pituitary Gland

Ovarian Cycle

Dr. Sherif Fahmy

Primordial folliclesPrimary

follicles Graafian follicle

Ovulation

Ovum (2dry oocyte arrested in 2nd meiotic division

Corona radiata

Corpus luteum

2dry follicle

Corpus albicans

Zona pellucida

OVARIAN & MENSTRUAL CYCLES

Dr. Sherif Fahmy

FSH

Follicular phase (14 days)

Effects of FSH• Formation of primary and

secondary follicles from the primordial follicles.

Primordial Follicle Primary FolliclePrimary oocyte arrested in 1st meiotic division

Single layer of follicular cells Multiple layer of follicular

cells

FSH

Primary Follicle Secondary Follicle

SpacesDeveloping thecal sheath

Developing zona pellucida

FSH

Growing 2dry follicle Secondary Follicle

Primary oocyte arrested in 1st meiotic division Zona

pellucida

Granulosa cells

Crescentic follicular antrum

Theca interna Theca

externa

FSH

Secondary Follicle Graafian Follicle

Follicular antrum

Primary oocyte arrested in 1st meiotic division

Secondary oocyte arrested in 2nd meiotic division.

LHFSH

Effects of LH• 1- Formaton of Graafian follicle.• 2- Ovulation.• 3- Formation of corpus luteum.

Graafian FollicleTheca externa

Theca interna

Stratum granulosum

Follicular antrum

Cumulus oophorus

Zona pellucida

Secondary oocyte arrested in 2nd meiotic division

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Fate of Graafian follicleTwo important events occur to the Graafian follicle:1- Ovulation.2- Formation of corpus luteum.

1- Ovulation

Steps of Ovulation LH from pituitary will produce the following changes:1- Inceases size of 2dry follicle to form Graafian follicle.2- Stimulate collagenase enzyme.3- Stimulate prostaglandins.4- Complete 1st meiotic division of primary oocyte to form 2dry oocyte (23 ch) and 1st polar body and start 2nd meiotic division.5- Ovulation.6- Formation of corpus luteum inside the ovary from the ruptured Graafian follicle.

OVULATION

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Ovulation by Electron Microscope

Dr. Sherif Fahmy

Dr. Sherif Fahmy

2- Corpus luteum

CORPUS LUTEUM

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Corpus albicans

Corpus Luteum• It is the lutenized Graafian follicle under the effect of

lutenizing hormone (L.H.). This occurs in the second half of ovarian cycle (luteal phase). Yellow pigments are deposited in granulosa and theca interna cells.

• Corpus luteum produces progesterone hormone which is responsible for secretory phase of uterine cycle.

• - Fate of corpus luteum:– No fertilization, it lives for 10 days and the transformed into

fibrous tissue called corpus albicans and stop secreting progesterone.

– With fertilization, it stays till the 4th month to keep endometrium intact.

Dr. Sherif Fahmy

Differences between divisions in spermatogenesis and

oogenesis

Ovarian Cycle• 1- Follicular phase : Graafian follicle is formed from

primary follicle under the effect of F.S.H. hormone. Growing follicle in this phase secretes estrogen hormone. (from 1st day to 13th day)

• 2- Ovulation: rupture of Graffian follicle and release of 2dty oocyte arrested in 2nd meiotic division. It is surrounded by corona radiata and zona pellucida, under effect of L.H. It occurs at 14th day .

• 3- Luteal phase: Yellow coloration of ruptured Graffian follicle (under effect of L.H. ) to form Corpus luteum. It secretes progesterone and small amount of estrogen (from day 15 – 28).

Dr. Sherif Fahmy

Ovarian Cycle

Dr. Sherif Fahmy

Primordial folliclesPrimary

follicles Graafian follicle

Ovulation

Ovum

Corona radiata

Corpus luteum

2dry follicle

Corpus luteum

OVARIAN & MENSTRUAL CYCLES

Dr. Sherif Fahmy

Uterine (menstrual) Cycle

Esterogen

Progesterone & esterogen

EsterogenProgesterone and few esterogen

Layers of Endometrium• 1- Superficial layer

(compact): It contains neck of glands.

• 2- Middle layer (Spongy): Edematous layer that contains body of the glands.

• 3- Basal layer: Thin layer that contains fundi of glands. Responsible for regeneration. It is not lost during menstruation.

Phases of Uterine cycle• 1- Menstrual phase (menstruation): -

1st day of the cycle is the 1st day of menstruation.-It is completed within 3 to 4 days.-There is loss of non-clotted blood, glands, blood vessels and endometrial cells (compact and spongy layers of endometrium).-It occurs due to spasm of endometrial arteriols as a result of degeneration of corpus luteum and drop in level of progesterone. Dr. Sherif Fahmy

• 2- Proliferative phase: • Other names are: follicular,

estrogenic or post-menstrual.• Endometrium restores its loses and

its thickness becomes 4 mms.• Glands become longer but straight.• This phase is under effect of

estrogen.• It lasts for 10 days. Dr. Sherif Fahmy

• 3- Secretory phase:• -Other names are luteal phase, progestational

or premenstrual.• -Blood vessels and glands become spiral.• -Endometrium becomes differentiated into

superficial compact, middle spongy & basal layers

• -This phase is under effect of progesterone and small amount of estrogen produced by corpus luteum.

• -It lasts for 14 days.Dr. Sherif Fahmy