BSC2086 1st Edition Lecture 23 Outline of Last Lecture I II III IV V Renal Physiology Aldosterone and ADH Glomerular Filtration Reabsorption and Secretion Transport Storage and Elimination of Urine Outline of Current Lecture I Introduction to the reproductive system II Structures of the reproductive system III Male reproductive functions I Introduction to the reproductive system a Reproductive system is the only system not essential to life b Structures i Gonads organs that make gametes and hormones ii Ducts receive and transport gametes iii Accessory glands secrete fluids into the ducts iv External genitalia collective name for perineal structure Structures of Reproductive System a Male VS Females i Functionally different ii Secrete hormones play big roles in the maintenance of normal sexual function iii Make and store reproductive cells 1 Combine to form new people 2 Female makes on gamete per month a Retains and nurtures zygote 3 Male makes large amounts of gametes a Makes billion sperm per day b Male Reproductive System i Testes male gonads 1 Secrete androgens or male sex hormones 2 Make male gametes known as spermatozoa or sperm II III ii Accessory organs 1 Secrete fluids into the ejaculatory ducts and the urethra 2 Seminal glands vesicles 3 Prostate gland 4 Bulbo urethral glands Male Reproductive Functions a External genitalia i Penis 1 Erectile organ that houses the distal portion of the urethra ii Scrotum 1 Encloses the testes 2 Made of 2 chambers or scrotal cavities a Each chamber houses one testis 3 Raphe raised thickening in scrotal surface a Marks the partition between the 2 scrotal chambers b Dartos muscle i Layer of smooth muscle in the dermis of the scrotum ii Characteristic wrinkling of the scrotal surface is caused by resting muscle tone 1 Also elevates testes c Cremaster Muscle i Layer of skeletal muscle deeper than the dermis ii Can contract or relax scrotum 1 Relax moves away from pelvic cavity causing a decrease in temperature 2 Contract moves towards pelvic cavity causing a rise in temperature a Occurs with temperature regulation or sexual arousal 3 Normal sperm development in the testes requires a temperature that s 1 1 degrees Celsius or 2 degrees Fahrenheit lower than normal body temperature d Spermatic Cords i Extended between the abdominopelvic cavity and testes ii Made of layers of fascia and muscle iii Encloses 1 Ductus deferens 2 Blood vessels 3 Nerves 4 Lymphatic vessels of testes iv They pass through the scrotum through the inguinal cavity 1 Ways of passage between abdominal musculature 2 Forms during development as the testes descend into the scrotum 3 Cryptorchidism testes don t enter into the scrotum a If they remain in the abdominopelvic cavity the elevated temperature will cause infertility or even testicular cancer e Male inguinal hernias i Protrusions of visceral tissues into the inguinal canal ii Weak point in the abdominal wall caused by spermatic cord iii Only common in males due to 1 Abdominal wall is almost intact in females 2 Female inguinal canals are very small a They contains ilioinguinal nerves and round ligaments of the uterus f Histology of testes i Subdivided into lobules by septa ii Lobules have about 800 slender and tightly coiled seminiferous tubules 1 Make sperm 2 About mile of tightly coiled seminiferous tubules in each testes a Make loop connected to rete testis b Rete testis network of passageways connected to epididymis iii Connected tissue capsules surround the seminiferous tubules 1 Blood vessels and large interstitial cells known as Leydig cells are found in that space a Make androgens which are the dominant male sex hormones i Testosterone is most important androgen g Meiosis i Special form of cell division only seen in producing gametes 1 Spermatozoa in males 2 Oocytes in females ii Gametes have 23 chromosomes half of the normal amount iii Zygote made of 46 chromosomes a fusion of the male and female gametes iv Occurs in seminiferous tubules in males 1 Begins with primary spermatocytes and produces spermatids 2 Spermatids undifferentiated male gametes v Meiosis I 1 Reductional division because chromosome amount goes from 46 to 23 2 Prophase I a Chromosomes condense b Synapsis tetrad made from combination of maternal and paternal chromosomes i The exchange of genetic material which increases genetic variation in the offspring occurs known as crossing over 3 Metaphase I a Tetrads line up at metaphase plate 4 Anaphase I a Maternal and paternal chromosomes separate b Tetrads split c Components from mother and father distributed randomly to the daughter cell 5 Telophase I a Ends with formation of 2 daughter cells each with a unique combination of chromosomes b Both cells have 23 chromosomes with 2 chromatids each i Not the same as diploid cell 6 Interphase a Separates meiosis I and meiosis II b Very short DNA not replicated vi Meiosis II 1 Equational division chromosome number not changed 2 Proceeds through prophase and metaphase II 3 Anaphase II a Duplicate chromatids separate 4 Telophase II a Yields 4 cells each with 23 chromosomes b Cytoplasm may not be distributed evenly h Spermatogenesis i Process of sperm production 1 Starts at outermost cell layer in the seminiferous tubules 2 Continues towards the lumen of the seminiferous tubules ii Cells 1 Spermatogonia stem cells divide by mitosis to make 2 daughter cells each with the same information a One stays as spermatogonium b Second differentiates into primary spermatocyte 2 Primary spermatocyte starts meiosis and makes 2 secondary spermatocytes a Formed be end of meiosis I b These cells don t have same genetic information 3 Secondary spermatocytes go through meiosis and make spermatids or immature gametes by end of telophase II 4 Spermatids differentiate and mature into spermatozoa 5 Spermatozoa will lose contact with the wall of seminiferous tubule and enter the fluid in the lumen of seminiferous tubule iii Spermiogenesis is the final step of spermatogenesis 1 Each spermatid matures into one spermatozoon or sperm a They are attached to cytoplasm of nurse cells 2 At the spermiation a spermatozoon a Loses attachment to the nurse cell and enters the lumen of the seminiferous tubule 3 Spermatogonial division to spermiation takes about 9 weeks i Contents of seminiferous tubules i Stem cells or spermatogonia ii Spermatocytes at various stages of meiosis iii Immature stem cells or spermatids iv Spermatozoa v Large nurse cells 1 Aka Sustentacular cells or Sertoli cells 2
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