BSC2086 A P II Final Exam Study Guide Lesson 21 Lesson 21 The Reproductive System Part I Introduction to the Reproductive System Reproductive System o ONLY system that is NOT essential to the life of the individual o Reproductive Structures Gonads Organs that produce gametes hormones Ducts Receive transport gametes Accessory Glands Secrete fluids into ducts External Genitalia Perineal structures Male Female Reproductive Systems o Are functionally different o Secrete hormones that play major roles in the maintenance of normal o Produce store specialized reproductive cells that combine to form new sexual function individuals Female produces one 1 gamete per month Retains nurtures zygote formed after fertilization Male produces large quantities of gametes Produces billion sperm per day Male Reproductive System Testes Male gonads o Secrete male sex hormones androgens o Produce male gametes spermatozoa sperm Accessory Organs Secrete fluids into ejaculatory ducts urethra o Seminal glands vesicles o Prostate gland o Bulbo urethral glands External Genitalia o Penis Erectile organ containing distal portion of urethra o Scrotum Encloses testes Has two chambers scrotal cavities Each testis lies in a separate scrotal chamber Raphe Raised thickening in scrotal surface Marks partition of two scrotal chambers Dartos Muscle Layer of smooth muscle in the dermis of scrotum Resting muscle tone causes characteristic wrinkling of scrotal surface elevates testes Cremaster Muscle Layer of skeletal muscle deep to dermis that can contact or relax to move the scrotum Contraction tenses scrotum pulls testes closer to body o Occurs during temperature regulation sexual arousal o Normal sperm development in testes requires temperatures 1 1 C 2 F lower than body temperature Spermatic Cords Extend between abdominopelvic cavity testes 1 BSC2086 A P II Final Exam Study Guide Lesson 21 o Consist of layers of fascia muscle o Enclose ductus deferens blood vessels nerves lymphatic vessels of o Pass into the scrotum through the inguinal canal passageways through testes abdominal musculature Form during development as testes descend into scrotum Cryptorchidism Testes do not descend into scrotum remain in abdomen May cause sterility testicular cancer o The cells in the testes are exposed to a higher temperature begin dying off o 10 experience testicular cancer Male Inguinal Hernias Protrusions of visceral tissues into inguinal canal Spermatic cord causes weak point in abdominal wall Common in males not in females because o Abdominal wall is nearly intact in females o Female inguinal canals are very small Contains ilioinguinal nerves round ligaments Histology of the Testes o Septa subdivide testis into lobules of uterus Lobules Contain about 800 slender tightly coiled seminiferous Seminiferous Tubules Produce sperm Each testis contains 1 2 of tightly coiled seminiferous tubules tubules o Form a loop connected to rete testis network of passageways that connects to the epididymis 2 BSC2086 A P II Final Exam Study Guide Lesson 21 Connective Tissue Capsules surround seminiferous tubules o Within those spaces there are Blood vessels Interstitial Cells Leydig Cells Large cells that produce androgens dominant male sex hormones Testosterone most important androgen Meiosis Meiosis is a special form of cell division involved only in production of gametes o Spermatozoa in males o Oocytes in females Gametes contain 23 chromosomes half the normal amount 46 Fusion of male female gametes produces zygote with 46 chromosomes Occurs at seminiferous tubules in males o Begins with primary spermatocytes o Produces spermatids undifferentiated male gametes Meiosis I Reductional division number of chromosomes is halved from 46 23 o Prophase I Chromosomes condense Synapsis Maternal paternal chromosomes come together to form a tetrad Crossing Over Exchange of genetic material that increases genetic variation among offspring o Metaphase I o Anaphase I Tetrads line up along metaphase plate Maternal paternal chromosomes separate Each tetrad splits Maternal paternal components are randomly distributed to the daughter cell o Telophase I Ends with formation of two 2 daughter cells with unique combinations of chromosomes 3 BSC2086 A P II Final Exam Study Guide Lesson 21 Both cells contain 23 chromosomes with two 2 chromatids each Interphase separates meiosis I meiosis II Not the same as a diploid cell Very brief DNA is NOT replicated Meiosis II Equational division chromosome number is not changed o Prophase II o Metaphase II o Anaphase II o Telophase II Duplicate chromatids separate Yields four 4 cells Each contains 23 chromosomes Cytoplasm may not be distributed evenly Male Reproductive Function Spermatogenesis The process of sperm production o Begins at outermost cell layer in seminiferous tubules o Proceeds toward lumen of seminiferous tubules o Spermatogonia Stem Cells Divide by mitosis to produce two 2 daughter cells Both daughter cells have identical info One remains as a spermatogonium Second differentiates into primary spermatocyte o Primary Spermatocyte Begins meiosis creates two secondary spermatocytes Secondary spermatocytes formed by the end of meiosis I Do NOT have the same genetic information o Secondary Spermatocytes Undergo meiosis II and form spermatids by the end of telophase II 4 BSC2086 A P II Final Exam Study Guide Lesson 21 o Spermatids Immature gametes that will differentiate mature into spermatozoa o Spermatozoa Mature gametes Lose contact with wall of seminiferous tubule Enter fluid in lumen of seminiferous tubules o Spermiogenesis Last step of spermatogenesis Each spermatid matures into one spermatozoon sperm Attached to cytoplasm of nurse cells At spermiation Spermatozoon loses attachment to nurse cell enters lumen of seminiferous tubule o Spermatogonial division to spermiation takes 9 weeks 5 BSC2086 A P II Final Exam Study Guide Lesson 21 Contents of Seminiferous Tubules o Spermatogonia stem cell o Spermatocytes at various stages of meiosis o Spermatids immature sperm cell o Spermatozoa o Nurse Cells Sustentacular Cells Sertoli Cells Large cells attached to tubular capsule Extend to lumen between other types of cells Five 5 Major Functions of Nurse Cells Maintain blood testis barrier uses tight junctions to isolate seminiferous tubules o Fluid inside produced by nurse cells Different composition than interstitial fluid Prevents immune cells from detecting attacking spermatozoa Support mitosis meiosis stimulates
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