Male Reproductive System 6.6 & 11.4

Essential Idea: Sexual reproduction involves the development and fusion of haploid gametes 11.4 Sexual Reproduction Understandings: Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis, and differentiation   Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm Fertilization in animals can be internal or external Fertilization involves mechanisms that prevent polyspermy Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy HCG stimulates the ovary to secrete progesterone during early pregnancy The placenta facilitates the exchange of materials between mother and fetus Birth is mediated by positive feedback involving estrogen and oxytocin Applications: The average 38 week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development of the young at birth for other mammals Skills: Annotate a diagram of seminiferous tubule and ovary to show the stages of gametogenesis Annotate a diagram of a mature sperm and egg to indicate functions

Embryonic development into male/female A. Embryos identical until about 8 weeks - The same embryonic structures give rise to ovaries and testes, clitoris and penis B. Females – genes on 2 X chromosomes interact to produce high estrogen and progesterone levels -> female reproductive structures C. Males – genes on Y chromosome responsible for testosterone production and testes development

II. Male Reproductive System

A. Spermatogenesis – starts at puberty and continues for life Seminiferous tubules of testes

Arise from spermatogonia (germinal epithelial cells) near outer edge of seminiferous tubules a. Undergo mitosis to replenish supply of spermatogonia b. Undergo meiosis to produce spermatozoa (millions/day) – stimulated by follicle stimulating hormone (produced by pituitary)

Daughter cells must mature into fully motile spermatozoa a. Sertoli cells – provide nutrients for developing sperm b. Leydig cells – leutinizing hormone from pituitary stimulates production of testosterone c. Move closer to the center of the seminiferous tubule as they develop d. Move to epididymis to finish maturation

Mature sperm a. Acrosome – contains hydrolytic enzymes to help get into egg b. Mitochondria – produce ATP for swimming c. Flagellum – tail for swimming

Production of semen a. Mature sperm moves from epididymis to vas deferens b. As it moves through vas deferens, fluid is added i. Seminal vesicle adds 70% of fluid - high in fructose (sugar) to provide energy ii. Prostate adds alkaline fluid – to help neutralize low pH in vagina

Hormones involved Leutinizing hormone (LH) - stimulates Leydig cells in testes to produce testosterone Follicle Stimulating Hormone (FSH) - along with testosterone, stimulates meiosis of spermatogonia