Animal Reproduction

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Eggs contain stored nutrients and are much larger.

Oogenesis is development of mature oocytes (eggs) and can take many years .

Slide 40

Oogenesis

Ovary

In embryo

Primordial germ cell

Mitotic divisions

Oogonium

Mitotic divisions

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

First polar body

Completion of meiosis I and onset of meiosis II

Secondary oocyte, arrested at metaphase of meiosis II

Ovulation, sperm entry

Completion of meiosis II

Second polar body

Fertilized egg

Primary oocyte within follicle

Growing follicle

Mature follicle

Ruptured follicle

Ovulated secondary oocyte

Corpus luteum

Degenerating corpus luteum

2n

2n

n

n

n

n

Slide 41

Spermatogenesis differs from oogenesis:

In oogenesis, one egg forms from each cycle of meiosis; in spermatogenesis four sperm form from each cycle of meiosis.

Oogenesis ceases later in life in females; spermatogenesis continues throughout the adult life of males.

Oogenesis has long interruptions; spermatogenesis produces sperm from precursor cells in a continuous sequence.

Spermatogenesis vs. Oogenesis

Slide 42

The interplay of tropic and sex hormones regulates mammalian reproduction

Human reproduction is coordinated by hormones from the hypothalamus, anterior pituitary, and gonads.

Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary.

FSH and LH regulate processes in the gonads and the production of sex hormones.

Slide 43

The sex hormones are androgens, estrogens, and progesterone.

Sex hormones regulate:

The development of primary sex characteristics during embryogenesis

The development of secondary sex characteristics at puberty

Sexual behavior and sex drive.

Slide 44

Hormonal Control of the Male Reproductive System

FSH promotes the activity of Sertoli cells, which nourish developing sperm and are located within the seminiferous tubules.

LH regulates Leydig cells, which secrete testosterone and other androgen hormones, which in turn promote spermatogenesis.

Slide 45

Hormonal control in the Male

Hypothalamus

GnRH

FSH

Anterior pituitary

Sertoli cells

Leydig cells

Inhibin

Spermatogenesis

Testosterone

Testis

LH

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