Developmental Zoology Lecture _ Gametogenesis: Spermatogenesis and Oogenesis

Gametogenesis

the process of forming gametes whereby a haploid cell (n) is formed from a diploid cell (2n) through meiosis and cell differentiation

spermatogenesis

formation of sperm cell

oogenesis

formation of egg cell

haploid (1n) gametes

reproduction in vertebrates is by sexual means involving _____________

ovum/ova

mature female reproductive cell

spermatozoa/spermatozoon

mature motile male sex cell

meiosis

spermatogenesis and oogenesis arise through ___________

meiosis

cell division where each daughter cell receives ½ genetic material from original cell

primordial germ cells (pgcs) ; extraembryonic endoderm (yolk sac)

derived from ______________________ later migrate to gonads during embryonic development (Oogonia/Spermatogonia)

oogonia (p1) ; spermatogonia (p1) ; primary oocyte (2×2N)

1st step in gametogenesis is pairing and doubling of chromosomes in ______________ in females or in _________________ in males; followed by growth as ____________

1st meiotic division produces two 2×1N cells (secondaary oocytes)

2nd step in gametogenesis is __________________

2nd meiotic division produces four haploid cells (spermatids, ova)

3rd step in gametogenesis is ___________________________

4 sperm cells ; spermatids ; spermatozoa

In spermatogenesis, all ___________ produced are viable; ________ mature and differentiate to form functional ___________

1 ; polar bodies

in oogenesis, only ___ of 4 cells produced is viable; others become abortive as ___________________ (only small amount of cytoplasm) that later degenerate

spermatogonia

mitotic germ cells in the testis are known as ___________

stem cells ; progenitor cells

some spermatogonia are _____________ that can produce more of themselves and also produce ________________, which divide a number of times before differentiation into sperm

primary spermatocyte

after the last mitotic division, the male germ cell is known as a __________________

secondary spermatocytes ; four spermatids ; motile spermatozoa

meiosis is equal, the first division yielding ___________________ and the second division yielding ______________, which mature to become ___________________

spermatogenesis

the complex, continuous process of male gamete (sperm) production, transforming diploid germ cells into haploid spermatozoa within the seminiferous tubules of the testis

spermiogenesis

the transformation of spherical, non-motile spermatids into elongated motile spermatozoa ( sperm cells) through structural remodeling

spermiation

the final stage of spermatogenesis where mature spermatids ae released from Sertoli cells into the lumen of seminiferous tubules

puberty

maturation of sperms begins at ________________

seminiferous tubules

sperms are produced in long, coiled ________________ in the testes; spaces between the tubules contain testosterone-secreting cells

spermatogonia

diploid male germ cells (________________) line the tubule's inner wall

primary spermatocytes

spermatogonia divide repeatedly by mitosis and differentiate to become ____________________

spermatids

meiosis of primary spermatocytes produces immature sperm (____________)

interstitial cells (leydig)

testicular cells that lie in the spaces outside the seminiferous tubules responsible for the production of testosterone and androgen via LH stimulation

sertoli cells

testicular cells that are inside the tubules support and provide nutrients developing sperm and create the blood-testis barrier. Regulated by FSH

basal lamina

layer of extracellular matrix secreted by the epithelial cells

tunica albuginea

the fibrous envelope that extends the length of the corpora cavernosa penis (containing erectile tissue) and corpus spongiosum penis (containing the male urethra)

rete testis ; mediastinum testis

network of delicate tubules located in the hilium of the testicle (_________________) that carries sperm from the seminiferous tubules to the efferent ducts

epidydymis

highly convoluted duct behind the testis, along which sperm passes to the vas deferens

lamina propia

serves several functions in these membranes, from holding the epithelial cells together to allowing the passage of blood vessels and nutrients

contain nucleus with DNA (genetic function) and acrosomal cap

the head of sperm have two functions

acrosomal cap

contains enzymes that allows sperm to break down membranes around egg and fertilize egg

tail

flagellum that provides motility

midpiece

between head and tail contains mitochondria that provide ATP to fuel swimming

golgi phase, cap phase, acrosome phase, and maturation phase

4 steps in spermiogenesis: spermatid phase

golgi phase

proacrosomal granules-scrosomal vesicle

sperm tail

axonemal complex

cap phase

formation of the acrosomal cap

acrosome phase ; flagellum development

manchette (________________) ; condensed nucleus

maturation phase

residual body is pinched off and phagocytized by sertoli cells

oogenesis

the process of formation of eggs

oogonia

following sex determination to female, the germ cells become ___________, which continue mitotic division for a period

oocyte ; primary oocyte ; secondary oocyte

after the final mitotic division, the germ cell becomes known as an ___________. It is called a ___________ until completion of the first meiotic division, and a _____________ until completion of the second meiotic division

unfertilized egg or ovum

after the second meiotic division, the secondary oocyte will be known as an ______________________

before birth

maturation of oocyte begins ________________

oogenesis

primordial germ cells that arrive in the gonad of female embryo, will differentiate into oogonia

oogonia then mitosis then meiosis then prophase I

oogenesis

puberty

maturation of oocyte continues at ______________

oocyte meturation inhibitor (omi)

near the time of birth, all 1 oocytes enter diplotene stage and do not finish meiosis I until puberty is reached, because of _____________

a pool of growing follicles

at puberty, ____________________ is established

15-20

how many follicles are selected from the pool and differentiate into 3 stages

follicular growth ; vitellogenic oocyte

the period after onset of meiosis from the time when prefollicle cells envelop the oocyte to the end of ______________ growth

ovarian follicle

the basic unit of female gametogenesis composed of spheroid aggregation of cells found in the ovary

follicles ; granulosa cells ; basal lamina

are compromised of an oocyte surrounded by monolayer of _____________ overlain by basement membrane (______________) and then a pripheral layer of theca cells and associated connective tissue and vasculature

zona granulosa, zona pellucida, corona radiata, and antrum

structural components of a developing ovarian follicle

zona granulosa

consists of layers of follicular cells surrounding the oocyte that nurture it and produce hormone

zona pellucida (zp)

a thick, glycoprotein, acellular membrane directly surrounding the oocyte, crucial for sperm binding

corona radiata

inner layer of follicle cells that surround and nourishes the oocyte

antrum

fluid-filled cavity that supports the maturation of the oocyte

mature graafian follicle

fluid amount increases, ovum pushed to one side, surrounded by cumulus oophorus, external follicle surrounded by theca interna and theca externa, increased intra follicular pressure, follicle ruptures, ovulation, and secondary oocyte in prophase stage

follicular phase, ovulation phase, and luteal phase

oogenesis/ovulation/ovarian cycle

ovarian maturation

the series of events beginning with fully yolk (post-vitellogenic) oocytes encapsulated in their follicles and culminating with the ovulation of fertilized eggs

vitellogenesis

the stage of oocyte characterized by the formation of yolk proteins and their accumulation in the ooplasm

yolk

the content of the ooplasm of the egg, which serves as the nutrient source for the developing embryo

proteins, carbohydrates, lipids, vitamins, minerals, and ions

yolk may include

yolk

contains nucleic acids encoding proteins essential for oogenesis and embryonic development

gonadal dysgenesis

abnormal embryonic gonadal development

pure or complete gonadal dysgenesis ; swyer syndrome

46, XY pure gonadal dysgenesis or (_________________)

46, XX gonadal dysgenesis

true hermaphroditism

ovotesticular or?

turner syndrome

45,X0

turner syndrome

chromosomal aneuploidy

genetic factors

mutations in genes like SRY (sex determining region Y) and WT1 (Wilms tumor 1)