LESSON 3A/5: GAMETOGENESIS Flashcards by Miss Bambi

Phases of Gametogenesis

1.Origin of the germ cells and their migration to the gonads
2.Multiplication of the germ cells in the gonads through the process of mitosis
3. Reduction of the number of chromosomes by one-half by meiosis
4. Final stages of maturation and differentiation of the gametes into spermatozoa or ova

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: Frogs and invertebrates, __________ is recognized early in life as regions in the vegetal pole cytoplasm of the zygote or as specific cells during cleavage stage.

germplasm (Germ cells)

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: Germ-cell lineage can be traced through ________ (in cells near the vegetal pole) and into the __________________

cleavage and into the endodermal floor of the primitive gut.

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: Birds, Reptiles & Mammals, _________________ arise in the epiblast of early embryo.

Primordial germ cells (PGC)

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: In Birds, germinal crescent located beyond the ______________

head region of the embryo

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: In Mammals, posterior wall of the yolk sac near the region of the ______

allantois

How well did you know this?

Not at all

Perfectly

Origin of the Germ cells: Urodele Amphibians (salamanders), arise from _______________ form through the influence of _______________________ different from Anurans.

-embryonic mesoderm cells
-ventral endodermal yolk mass

How well did you know this?

Not at all

Perfectly

Regardless of origin: Primordial Germ Cell (PGC) is:

Recognizable due to large size and clear cytoplasm
Histochemical characteristics:
- high alkaline phosphatase activity
  (mammals)
- high glycogen content (birds)
- monoclonal Ab’s (birds & mammals)

How well did you know this?

Not at all

Perfectly

n vertebrates, PGC migrate to the gonads by two principal mechanisms:

They pass through the walls of blood vessels and enter the circulation. From the blood, penetrate the blood vessels and settle down in gonads. (birds and reptiles)
They reach the gonads by migration around the wall of the posterior gut and then through the dorsal mesentery ; guided by extracellular matrix molecules, laminin and fibronectin within the mesentery

How well did you know this?

Not at all

Perfectly

Primordial germ cell migration in the mouse

(A) On embryonic day 8, PGCs established in the posterior epiblast migrate into the definitive endoderm of the embryo. The photo shows four large PGCs (stained for alkaline phosphatase) in the hindgut of a mouse embryo.

(B) The PGCs migrate through the gut and, dorsally, into the genital ridges.

How well did you know this?

Not at all

Perfectly

Once settled in the gonads, PGC enter ______________ and increase their number by mitosis.

proliferative phase

How well did you know this?

Not at all

Perfectly

active germ cells mitotically in ♀

Oogonia

How well did you know this?

Not at all

Perfectly

active germ cells mitotically in ♂

Spermatogonia

How well did you know this?

Not at all

Perfectly

Pattern of mitotic activity of PGC in gonads _______ between ♂ and ♀

differs

How well did you know this?

Not at all

Perfectly

In human ♀, intense mitotic activity between ____________ mos. of pregnancy have ___ oogonia, then falls sharply due to atresia (natural degeneration)

-2nd – 5th mos
-7M oogonia

How well did you know this?

Not at all

Perfectly

Natural degeneration in human female after intense mitotic activity

Atresia

How well did you know this?

Not at all

Perfectly

By 7th month, most oogonia have entered _________ of 1st meiotic division becoming primary oocytes. (end of proliferative phase of oogenesis).

prophase

How well did you know this?

Not at all

Perfectly

In _________________, oogonia are capable of dividing throughout reproductive cycle

nonmammalian vertebrates

How well did you know this?

Not at all

Perfectly

In ________, mitosis continues in the gonad of early embryo but ceases during later days of pregnancy, only to resume after birth.

rodents

How well did you know this?

Not at all

Perfectly

In human ♂, beginning at _______, mitosis produces ________________that enter meiosis and this continues as long as the male is capable of reproduction

-puberty
-spermatocytes

How well did you know this?

Not at all

Perfectly

reproductive role of the human male

-to produce sperm
-deliver them to the vagina of the female

How well did you know this?

Not at all

Perfectly

The _______ deposits semen in the vagina during sexual intercourse

penis

How well did you know this?

Not at all

Perfectly

Accessory glands produce a fluid called _______ for carrying the sperm to the penis

semen

How well did you know this?

Not at all

Perfectly

The ________ produce sperm and the male sex hormone, _____________.

-testes
-testosterone

How well did you know this?

Not at all

Perfectly

Sperm Structures:

1. Head (Nucleus, Acrosome, Centriole) 2. Neck 3. Middle Piece (Mitochondrion in spiral shape) 4. Tail (Plasma Membrane)

reproductive roles of the human female

-produce eggs -nourish, carry, and protect the developing embryo -nourish the infant for a time after it is born.

The testes contains tiny tubes called

Seminiferous tubules

The human female reproductive system consists of:

-Two ovaries -two uterine tubes/oviduct -The uterus -The vagina -External genitalia

The _______________ contained in the paired breasts produce milk for the newborn baby.

mammary glands

The uterine tubes have ________ lining

Cilia lining

___________ is the production of gametes

Gametogenesis

the formation of sperm, is continuous and prolificative

Spermatogenesis

Hundreds of millions of sperm are produced per day; each sperm takes about __ weeks to develop

7 weeks

Where does the production of sperm occur?

Seminiferous tubules

Sperm: What was produced after the first mitotic division (2n) from primordial germ cell in embryo?

Spermatogonial stem cell (2n)

Sperm: the spermatogonial stem cell undergo further mitosis and produce?

Spermatogonium (2n)

Spermatogonium produces _______ as the last product of mitotic division.

Primary Spermatocyte (2n)

The primary spermatocyte undergo meiosis I and produce _________ which are now________.

-Secondary spermatocyte - 2 haploid cells

Secondary Spermatocyte undergo meiosis II and produces ____________

Early Spermatid (4 haploid cells)

The early spermatid undergoes _________ to finally became sperm cells

Differentiation

Complete division (product) of Sperm formation

Primordial Germ Cell ---> (mitosis)---> Spermatogonial stem Cell (2n) --> Spermatogonium (2n)---> Primary Spermatocyte (2n) ---> (Meiosis) ---> M1: Secondary oocyte (n) ---> M2: Early spermatid ---> (Differentiation) ---> Sperm Cells

Testes contain __________ coiled seminiferous tubules

one to three

A prolonged process of developing mature egg

Oogenesis

____________ form in the female embryo but do not complete their development until years or decades later

Immature eggs

In embryo: The primordial germ cell undergoes mitotic division and form _______ during oogenesis

Oogonium (2n)

In embryo: The oogonium undergo further mitosis and produce ____________

Primary oocyte (present at birth), arrested in prophase of meiosis I

Starting at Puberty: The primary oocyte completes the meiosis I and produce a _________ and ______

-first polar body -Secondary oocyte, arrested at metaphase of meiosis II

The meiosis II is stimulated by _________

sperm

During Meiosis II, the end result is ____ and ____

-1 ovum (egg cell) -3 polar bodies

Complete Division (product) of Egg cell formation (Fertilization)

[In Embryo] Primordial germ Cell ---> (mitosis) ---> Oogonium (2n) ---> Primary Oocyte [Arrested in Prophase of Meiosis 1 (M1)] ---> [ Starting at Puberty] First Polar Body & Secondary Oocyte (n) [ arrested at metaphase of Meiosis II (M2)] ---> (Interruption of Sperm, Stimulates the completion of M2) ---> 1 Ovum and 3 Polar bodies (Ovum is fertilized)

Mature sperms are _______ than spermatogonia

smaller

Mature ova are _____ than oogonia

larger

During the spermatogenesis, the _________ contributes to the nutrition of the cell.

Sertoli cells

During oogenesis, Eggs take up large quantities of materials produced by _____

liver

Spermatogenesis: Energy source

-Rely on seminal fluid as energy source -Little or no RNA synthesis occurs

Oogenesis: Energy source

-Egg stores both energy sources and precursors of proteins and nucleic acids -Egg produces and stores up much RNA

Human reproduction is coordinated by hormones from

-hypothalamus, -anterior pituitary, -gonads

_________________ is secreted by the hypothalamus and directs the release of FSH (follicle-stimulating hormone) and LH (luteinizing hormone) from the anterior pituitary

Gonadotropin-releasing hormone (GnRH)

_______ regulate processes in the gonads and the production of sex hormones

Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH)

main sex hormones

steroid hormones

main androgen

Testosterone

Estrogens consist of mainly

estradiol and progesterone

Sex hormones serve many functions in addition to gamete production, including __________ and ________________________

-sexual behavior -the development of primary and secondary sex characteristics

_____ promotes the activity of Sertoli cells

Follicle-stimulating hormone (FSH )

nourish developing sperm

Sertoli cells

____ regulates Leydig cells

Luteinizing hormone (LH)

secrete testosterone and other androgens, which in turn promote spermatogenesis

Leydig cells

Testosterone regulates the production of GnRH, FSH, and LH through _______________

negative feedback mechanisms

Sertoli cells secrete the hormone ______

inhibin

Inhibin do what?

reduces FSH secretion from the anterior pituitary

Aids sperm maturation; increasing testosterone production

Follicle-stimulating hormone (FSH)

Controls pituitary secretion

Gonadotropin-releasing hormone(GnRH)

Stimulate testosterone secretion

Luteinizing Hormone (LH)

-Increase sperm production -stimulate development of male primary and secondary sexual characteristics -Inhibit LH secretion

Testosterone

Source of FSH and LH

Pituitary Gland

Source of GnRH

Hypothalamus

Source of Inhibin

Sustentacular cells in testes/ Ovaries

Source of Testosterone

Interstitial cells in testes

Prior to ovulation, the _______ thickens with blood vessels in preparation for embryo implantation

endometrium

If an embryo does not implant in the endometrium, the endometrium is shed in a process called _______

Menstruation

two cycles of female reproduction

-Menstrual Cycle (Uterine Cycle) -Ovarian Cycle

Menstrual Cycle (Uterine Cycle)

Changes in the uterus

ovarian cycle

Changes in the ovaries

The pattern of hormone secretion is intricately related to the cyclical release of a ___________from the ovary.

secondary oocyte

-Stimulates thickening of uterine wall -maturation of oocyte -development of female sexual characteristics -inhibits PSH secretion -Increases LH secretion

Estrogen (estradiol)

Source of estrogen (estradiol)

Ovarian Follicle; Corpus Luteum

-Causes immature oocyte and follicle to develop -increases estrogen secretion -stimute new gamete formation -development of uterine wall after menstruation

Follicle-stimulating hormone

-Prevents corpus luteum from disintegrating -Stimulates corpus luteum to secrete estrogen and progesterone

Human chrionic gonadotrophin (hCG)

Sources of hCG

Embryonic membrane and placenta

-Stimulate further development of oocyte and follicle -stimulate ovulation -increase progesterone secretion -aids in development of corpus luteum

Luteinizing Hormone (LH)

Stimulate uterine contractions during labor and milk release during nursing

Oxytocin

Sources of Oxytocin

Pituitary Gland

Promotes milk secretion by mammary gland after childbirth

Prolactin

Sources of Prolactin

Pituitary Gland

Stimulates the thickening of uterine wall

Progesterone

Sources of Progesterone

Corpus Luteum (temporary organ)

-Increases flexibility of pubic symphysis during pregnancy -help dilate uterine cervix during labor delivery

Relaxin

Sources of Relaxin

Placenta and Ovaries

The sequential release of GnRH then FSH and LH stimulates __________________

follicle growth

Follicle growth and an increase in the hormone estradiol characterize the _____________________

follicular phase of the ovarian cycle

The follicular phase ends at __________, and the ___________ is released

-ovulation -secondary oocyte

Thickening of the endometrium (uterine cycle) during the proliferative phase coordinates with the __________

follicular phase (ovarian cycle)

Secretion of nutrients during the secretory phase (ovarian cycle) coordinates with the _________

luteal phase (uterine cycle)

Shedding of the endometrium during the menstrual flow phase coordinates with the growth of _________

new ovarian follicles

In the luteal phase, following ovulation, the ____________ left behind is stimulated to transform into a corpus luteum

follicular tissue

secretes progesterone and estradiol, which exert negative feedback on the hypothalamus and pituitary

corpus luteum

-Follicular matures in the ovary -menstruation -Endometrium rebuilds

Follicular Phase

Ovary Releases secondary oocyte

Ovulation phase

-Corpus luteum forms -Endometrium thickens and become glandular

Luteal Phase

Duration of Follicular phase

1-5 days

Duration of Ovulation

6-14 days

Duration of Luteal Phase

15-28 days

During the luteal phase, the___________________ is inhibited.

development of an additional oocyte

The hypothalamus is inhibited by

Combination of estradiol and progesterone

Hypothalamus if stimulated by

High levels of estradiol

Anterior pituitary gland is inhibited by

Low levels of estradiol

A ________ begins if no embryo implants in the endometrium

new cycle

Cells of the uterine lining can sometimes migrate to an abnormal, or _______ , location

ectopic

Swelling of these cells in the uterine lining in response to hormone stimulation results in a disorder called __________

endometriosis

the cessation of ovulation and menstruation

Menopause

After about ________ cycles, human females undergo menopause

500 cycles

-The endometrium is reabsorbed by the uterus -Sexual receptivity is limited to a “heat” period -The length and frequency vary from species to species

Estrous Cycle

LESSON 3A/5: GAMETOGENESIS Flashcards

(122 cards)