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Gametogenesis :

Spermatogenesis dan oogenesis



The Epididymus

Figure 28.9



The Seminiferous Tubules



Sertoli Cells and Developing Spermatocyte



1) Spermatositogenesis

2) Meiosis

3) Spermiogenesis

Spermatozoa X dan Y



Morfologi abnormal dari spermatozoa



� Sperm produced in seminiferous tubules of testes;

� Testes are suspended in the scrotum; idealtemperature is 34 degrees C.

� Mature sperm are stored in the epididymis.

� Vas deferens is the tube from the epididymis tothe urethra; sperm become motile in vasdeferens

� Secretions are added to sperm in vas deferens.

� Semen is a mixture of sperm, prostaglandins,

alkaline buffers, sugars, water.



Sertoli Cells

� Extend from basal lamina to lumen

� Lots of microtubules and microfilaments: movement andpushing

� Most numerous seminiferous cell prior to puberty;number same after puberty

� Supporting cells of gonad; nourish and support cells

� Heat resistant; radiation resistant, Blood Testis Barrier � Protects developing germ cells from toxins

� Sets up immunological barrier: The zona occludenslocks antigens into testes and keeps antibodies to spermout

� Contains androgen binding protein or ABP (which bindstestosterone and acts as carrier)

� Memiliki fungsi fagositik



Figure 28.8

Spermiogenesis and Spermatozoon Structure



SPERM MATUR ATION

� Acrosomal vesicle - contains enzymes thatdigest proteins and complex sugars.

± Important for egg recognition

± Lyses outer covering of egg

� Flagellum ± whip-like structure that propelsthe sperm using ATP

± ATP is produced by the mitochrondria

± The enzyme dynein hydrolyzes ATP to releaseenergy

� Dynein is attached to the microtubules of theflagellum



The Modification of a Germ Cell to Form a

Mammalian Sperm



The Sperm Head

H ead: EM, LS × 14 000

AC = acrosome; PM = plasma membrane

From Wheater¶s Functional Histology, 4th

ed., 2000.

The head of a mature sperm, lengthwise, is approximately 1/20 the

diameter of a mature ovum.



The Sperm Neck

N eck (middle piece and principal piece): EM, LS × 17 000

Mi = mitrochondria; C = cytoplasm; F, Rn, Rb, & An = all parts of flagellum structure


ed., 2000.



� Typical ejaculate = 2-5 ml fluid

± Contains between 20 ± 100 million spermatozoa

per ml

� Seminal fluid

± A distinct ionic and nutritive glandular secretion

Contents of Semen



Male Reproductive System

seminalvesicle

prostate

gland

Cowper¶s

gland

secrete

seminal

fluid

Fruktosa, Protein dan

Prostaglandin

Asam sitrat, As Phospat

Lubrikasi uretra

(mukoprotein)



Figure 28.12

Hormonal Feedback and the Regulation of the Male

Reproductive Function



Synthesis of Androgens

* *

**

From Blood

* 3ß-hydroxysteroid dehydrogenase

**5-reductase

Protein kinase

Adenylate cyclase



O

CH3

CH3OH

Testosterone Dihydrotestosterone(DHT)

Converting Enzyme:

5-alpha-Reductase

O

CH3

CH3OH

H H

Finasteride



Hypophysectomy

- The testes shrink in size

- Sperm outpput declines

- Spermatogenesis arest at

the primary spermatocyte stage- Testosterone out falls

prostat and seminal vesicle regress

1. The Testosterone was involved in

the maintenance of spermatogenesis2. The secretion of Testosteron by the Leydig cells

was under the control of the pituitary



� Cholesterol serves as the substrate for

P5 biosynthesis in the Leydig cells.

� Testosterone is the principal steroid

produced by Leydig cells.

� Androstenedione and

dehyrdorepiandrosterone are alsoproduced but the physiological

potencies are very low.



� In some tissues, testosterone is

converted to either dihydrotestosterone(DHT) or E2 which are the biologically

active steroids in these tissues.

� Almost 100% of the testosterone in the

blood is bound to protein



Endocrine Control

� Testicular androgens exert negative feedbackat the level of the AP and the hypothalamus.

� Pituitary gonadotropin secretion in the male is

under a tonic regulatory control.

� Release of GnRH is coded, which may benecessary to prevent pituitary gonadotrophs

from becoming refractory to GnRH.

� In the adult male, there is a pulsatile release of LH about every 90 min, and the pattern varies

from day to day.



Inhibin

� Sertoli cells of the testes produce inhibin,

whos putative role is to control the secretion

of FSH.

� FSH secretion from cultured AP (Anterior Pituitary) cells is inhibited when AP cells are

cocultured with Sertoli cells.

� This is further substantiated by the fact that

prior exposure to inhibin suppresses the

elevation of FSH release following GnRH

administration.



Inhibin

� Other evidence suggests that inhibin alsosuppresses FSH at the hypothalamus.

� Granulosa cells from the ovarian folliclesecrete inhibin that acts directly on AP cellcultures derived from the male or female.

� Administration of anti-inhibin antisera to ratsof either sex causes an elevation in serumFSH, LH remains unchanged.



Prolactin

� Hypox of male rats results in a loss of testicular LH receptors, but administration of FSH or LH does not, re-establish testicular LH receptors.

� Inhibition of FSH and LH secretion by anti-GnRH or by E2 or T trt does not result in aloss of testicular LH receptors.

� Inhibiton of Prl secretion results in adecrease in testicular LH receptors.



1) Dynein arms attached to A microtubule ³walk´

along the B microtubule

2) ³Walking´ dynein generates the force

3) Since microtubules are cross linked to each other

instead of sliding they bend



OOGENESIS



Perkembangan folikel



Figure 28.16

The Ovarian Cycle



The Ovarian Follicle of Mammals



Maturasi Oosit in vitro

Immature oocyte

Mature oocyte

(36 jam setelah kultur in vitro)



The OvumGraafian follicle Az an × 75

� F A = follicular antrum

� CR = corona radiata

� O2 = secondary oocyte

� ZG = zona granulosa

� TI = theca interna

� The oocyte is released along

with the corona radiata.� Notice the clear ring just around

the ovum (arrow tip): this is the

zona pellucida.


ed., 2000.



Figure 28.16

The Ovarian Cycle



ROS : Reactive Oxygen Spesies



ZP1, ZP2 and ZP 3 : Glycoprotein

ZP3 :-Bound to the head of mouse sperm

-83 kDa

- Initiates the acrosome reaction



Menstrual Cycle



Seleksi Folikel Dominan



Sperm Cell Movement



� Trisomy 21 (Down¶s Syndrome)



� Klinefelter Syndrome (XXY)



� Turner Syndrome (XO)



� XYY males



Figure 2.

Estimatedbirthincidence of maternallyderived

trisomy 21.

Oogenesis versus



Oogenesis versus

Spermatogenisis



Meiosis I (four phases)Meiosis I (four phases)

�� Cell divisionCell division that reduces the chromosomechromosome

number by oneone--half.half.

�� four phasesfour phases:a.a. prophase Iprophase I

b.b. metaphase Imetaphase I

c.c. anaphase Ianaphase I

d.d. telophase Itelophase I



Meiosis I : the reduction division

Prophase I(early)

(diploid)

Prophase I(late)

(diploid)

Metaphase I(diploid)

Anaphase I(diploid)

Telophase I(diploid)

NucleusSpindle

fibersNuclear

envelope



Prophase IProphase I

�� Longest and most complex phase (90%)Longest and most complex phase (90%) Tahap paling penting

�� ChromosomesChromosomes condense

kondensasi benang-benang k r omatin

sebelum kondensasi disebut sebagai f aseleptotene

�� SynapsisSynapsis occurs: homologous chromosomeshomologous chromosomes cometogether to form a tetradtetrad. selama fase zygotene

�� TetradTetrad is two chromosomeschromosomes or four chromatidschromatids(sister and nonsister chromatids pachytene



Homologous ChromosomesHomologous Chromosomes

� Pair of chromosomeschromosomes (maternalmaternal and paternalpaternal) that are

similar in shape and size.

� Homologous pairs (tetrads)(tetrads) carry genes controlling

the same inherited traits.

� Each locuslocus (position of a gene)(position of a gene) is in the same

position on homologues.

� Humans have 23 pairs of homologous chromosomeshomologous chromosomes..

a. 22 pairs of autosomesautosomes

b. 01 pair of sex chromosomessex chromosomes



Prophase IProphase I -- SynapsisSynapsis

Homologous chromosomes

sister chromatids sister chromatids

Tetrad



Homologous ChromosomesHomologous Chromosomes

Paternal Maternal

eye color

locus

eye color

locus

hair color

locushair color

locus



Crossing Over Crossing Over

�� Crossing over (variation)Crossing over (variation) may occur between

nonsister chromatidschromatids at the chiasmatachiasmata.

�� Crossing over Crossing over : segments of nonsister

chromatidschromatids break and reattach to the other

chromatidchromatid.

�� Chiasmata (chiasma)Chiasmata (chiasma) are the sites of crossingcrossingover over .



Crossing Over Crossing Over -- variationvariation

nonsister chromatids

chiasmata: site

of crossing over variation

Tetrad



Recombination (crossing over)

� Occurs in prophase of meiosis I

� Generates diversity

Letters denote genes

Case denotes alleles

�Creates chromosomes with new combinations of alleles for genes A to F.

A

B

C

D

E

F

a

b

c

d

e

f

c

d

e

f

A

B

a

b

C

D

E

F



Sex ChromosomesSex Chromosomes

XX chromosome - female XY chromosome - male

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