Anatomy and Physiology Marieb’s Human Anatomy and Physiology Ninth Edition Marieb w Hoehn Chapter 27 Male Reproductive System Lecture 18 Part 1: Overview and Primary Sex Organs Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1] Slides 16 – 38; 50 min [Lecture 2] 118 min (38 slides plus review of course Web sites and syllabus)

Warning! The video and narration in this presentation concerns the Male Reproductive System and uses explicit graphics and terminology dealing with this subject matter. Some material may not be suitable for younger viewers. Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1] Slides 16 – 38; 50 min [Lecture 2] 118 min (38 slides plus review of course Web sites and syllabus)

Male Reproductive System There are three main functions of the male reproductive system Produce and maintain sex cells (sperm) Transport sperm and supplemental fluids to the female reproductive tract Secrete male sex hormones Sex organs can be divided into Primary sex organs (gonads) = testes (sperm, hormones) Accessory (secondary) sex organs = internal and external reproductive organs In order for sexual reproduction to take place, we need: 1) mobile cells, 2) cells that are nutrient laden. These two things are impractical to combine into one cell, so males have sperm (DNA with propellers!!), and females have large, nutrient-laden eggs as their sex cells (gametes).

Male Reproductive System Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Testis → Epididymis → Vas (ductus) deferens → Ejaculatory duct → Urethra

Male Reproductive Organs posterior view Figure from: Hole’s Human A&P, 12th edition, 2010

Descent of Testes Figure from: Hole’s Human A&P, 12th edition, 2010 Descent begins 1-2 months before birth under the influence of testosterone Descent is necessary for sperm production Failure of testes to descend = cryptorchidism

Structure of the Testis Figure from: Hole’s Human A&P, 12th edition, 2010 Surrounded by the tunica albuginea – a tough, white, fibrous capsule that encloses each testicle Septa divide each testicle into about 250 lobules Each lobule contains 1-4 highly coiled seminiferous tubules that give rise to sperm Interstitial cells (of Leydig) lie in between seminiferous tubules and secrete male sex hormones Rete Testis

Review of Mitosis and Meiosis Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Major differences between mitosis and meiosis: 1) mitosis produces identical daughter cells, meiosis produces cells with recombined DNA; 2) daughter cells in mitosis have a diploid number of chromosomes whereas in meiosis gametes contain the haploid chromosome number; 3) two daughter cells are produced as a result of mitosis, whereas four cells are produced after meiosis. Mitosis – production of two identical diploid daughter cells Meiosis – production of four genetically varied, haploid gametes

Chromosome Crossing Over Figure from: Hole’s Human A&P, 12th edition, 2010 mixes up traits different colors represent the fact that one homologous chromosome comes from the individual’s father (paternal) and one from the mother (maternal) Tetrad the genetic information in sperm cells and egg cells varies from cell to cell

Seminiferous Tubules and Sperm Maturation Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 It takes about 75 days for a spermatogonium to become mature spermatazoon. Spermatogonium = stem cell

Spermatogenesis Spermatogonium (2n) Primary spermatocyte (2n) Know the order of events below! Spermatogonium (2n) Primary spermatocyte (2n) Meiosis I Secondary spermatocyte (n) Meiosis II Spermatid (n) Spermiogenesis Spermatozoan (n)

Formation of Sperm Cells Figure from: Hole’s Human A&P, 12th edition, 2010 Supporting cells are sustentacular cells They: are important in regulating and supporting spermatogenesis help maintain the blood-testis barrier

Structure of a Sperm Cell Figure from: Hole’s Human A&P, 12th edition, 2010 Only flagellum in human body Mitochondria Young men produce about 300,000 sperm per MINUTE, or about 4 million sperm cells per day. Enzymes used to penetrate the egg during fertilization

Review Spermatogenesis Spermatozoa Spermatogonia, 1o spermatocyte, 2o spermatocyte, spermatid, spermatozoan Is a result of meiotic division Under the control of FSH Is guided and regulated by sustentacular cells Produces 4 haploid gametes (spermatozoa) Spermatozoa Head, midpiece, and tail Acrosomal cap – enzymes use for fertilization Non-motile when produced – must undergo capacitation