CHAPTER 19: REPRODUCTIVE SYSTEMS 19.1 INTRODUCTION • Produce and nurture sex cells. • Transport them to sites of fertilization. • Male sex cells: sperm • Female sex cells: eggs/oocytes • Sex cells: haploid 23 chromosomes • Secrete hormones that develop and maintain sex characteristics and regulation of reproductive physiology.
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CHAPTER 19: REPRODUCTIVE SYSTEMS 19.1 INTRODUCTION Produce and nurture sex cells. Transport them to sites of fertilization. Male sex cells: sperm Female.
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CHAPTER 19: REPRODUCTIVE SYSTEMS19.1 INTRODUCTION• Produce and nurture sex cells.• Transport them to sites of fertilization.• Male sex cells: sperm• Female sex cells: eggs/oocytes• Sex cells: haploid 23 chromosomes• Secrete hormones that develop and maintain
sex characteristics and regulation of reproductive physiology.
19.2 ORGANS OF THE MALE REPRODUCTIVE SYSTEM
• Gonad/testes: primary sex organs; where sperm cells and male sex hormones form.
• Accessory sex organs: internal and external reproductive organs.
TESTES• Ovoid structures about 5 centimeters in length
and 3 centimeters in diameter.• Both testes are within the cavity of the saclike
scrotum.STRUCTURE OF THE TESTES• Tough, white, fibrous capsule encloses each
testis.• Posterior border, the connective tissue thickens
and extends into the testis, forming thin septa that divide the testis into 250 lobules.
• Each lobule contains one to four highly coiled, convoluted seminiferous tubules. (70 cm. long uncoiled)
• Unite posteriorly and unite to form a network of channels.
• Channels give rise to several ducts that join a tube called the epididymis.
• Epididymis coils on the outer surface of the testis and continues to become the vas deferens. Pg. 492
• Spermatogenic cells: specialized stratified epithelium that give rise to sperm cells, lines the seminiferous tubules.
• Interstitial cells (cells of Leydig): lie in the spaces between the seminiferous tubules; produce and secrete male sex hormones.
• Epithelial cells could give rise to testicular cancer.
• Symptoms: first painless testis enlargement or a scrotal mass that attaches to a testis.
FORMATION OF SPERM CELLS• Sertoli cells (supporting cells) and
spermatogenic cells: cells of the epithelium of the seminiferous tubules.
• Supporting cells provide a scaffolding for the spermatogenic cells, and also nourish and regulate them.
• Males produce sperm cells continually throughout their reproductive lives.
• Sperm cells collect in the lumen of each seminiferous tubule.
• Then pass to the epididymis, where they accumulate and mature.
• A mature sperm cell is a tiny, tadpole-shaped structure about 0.06mm long.
• Flattened head, cylindrical midpiece (body), and an elongated tail.
• Head: nucleus and, compacted chromatin, protrusion at its anterior end, called the acrosome, contains enzymes that help the sperm cell penetrate an egg cell during fertilization.
• Midpiece of a sperm cell has a central, filamentous core and many mitochondria in a spiral.
• Tail (flagellum) • Mitochondria provide ATP for the tail’s lashing
movement.
SPERMATOGENESIS• Formation of sperm cells.• In a male embryo, spermatogenic cells are
undifferentiated, called spermatogonia.• Contains 46 chromosomes in its nucleus.• During embryonic development, hormones
stimulate spermatogonia to undergo mitosis and some of them enlarge to become primary spermatocytes.
• Supporting cells help sustain the developing sperm cells.
PUBERTY• Primary spermatocytes then reproduce by a
special type of cell division call meiosis.• Different combination in each sperm.• Haploid
• Each primary spermatocyte divides to form two secondary spermatocytes.
• Each of these cells divide into two spermatids.• Spermatids mature into sperm cells.