spermatogenesis and oogenesis

Spermatogenesis and Oogenesis

Pgs. 984-985 (Campbell)

Spermatogenesis

• Production of sperm – Continuous and prolific– Each ejaculation contains ~100-650 million

sperm

• Occurs in the testes – Seminiferous tubules

What happens is …

• Spermatogonia (stem cells that give rise to sperm) are located at the periphery of each seminiferous tubule – Spermatogonia are diploid

• Developing sperm move toward the central opening (lumen) of the tubule as they undergo meiosis and differentiation

• 4 cells result– Develop into mature sperm – Haploid

Pg. 985 Campbell Page 985 Campbell

The structure of sperm

Campbell

Oogenesis

• The development of ova – Mature, unfertilized eggs cells– Happens in the ovary

• Oogonia (stem cells that give rise to ova)– Multiply and begin meiosis– STOPS at prophase 1– At this phase, the cells are called primary oocytes – Remain in this phase until the onset of puberty, when

they are activated by hormones• Activated by LH and FSH

What happens next ...

• Beginning at puberty, FSH periodically stimulates a follicle to grow and induces its primary oocyte to complete meiosis 1 and start meiosis 2

• Meiosis then STOPS again– The secondary oocyte, released during ovulation,

does not continue meiosis right away– Penetration of the egg cell by sperm triggers the

completion of meiosis– Then meiosis is complete– LH stimulates the completion of meiosis

Campbell

Growing follicle

Major difference #1

• 1. unevenness in the mitotic division/cytokinesis of oogenesis– Almost all the cytoplasm 1 daughter cell

(secondary oocyte) – 3 polar bodies which degenerate

– Spermatogenesis = four mature sperm

Major difference #2

The cells that produce sperm continue to divide by mitosis throughout life (males)

Not the case for women

*born with all the primary oocytes

Major difference #3

• Oogenesis has long resting periods

• Sperm is produced in an uninterrupted sequence

Exit Slip • On the slip of paper, write a proper heading and

title it Exit Slip 4/14/09• Answer the following questions in complete

sentences:– 1. When (during the menstrual cycle) does the

production of the hormones FSH and LH peak? – 2. Arrange the following organs in the correct

sequence for the travel of sperm: epididymis, testis, urethra, vas deferenes

– 3. List one function/role for the following hormones:• Testosterone• Estrogen• FSH