NURS6210 Physiology II - Male Reproduction Lecture Slides (PDF)

Master of Nursing Science (Pre-registration) Programme (2024-25) Year 1 Term 2 NURS6210 Physiology II 生理學 二 Reproduction: Male production Jan 10, 2025 (Friday) 1130 to 1215...

Master of Nursing Science (Pre-registration) Programme (2024-25) Year 1 Term 2 NURS6210 Physiology II 生理學 二 Reproduction: Male production Jan 10, 2025 (Friday) 1130 to 1215 Ying LAU (劉 櫻) PhD, MN, BN(Hons), BSc, RN, RM, FAAN Professor Email: [email protected] Professor Lau Ying CUHK 2025 1 Intended Learning Objectives: At the end of this lecture, students should be able to: understand hypothalamic-pituitary-testicular axis and feedback control describe the testis and spermatogenesis understand testicular steroidogenesis and conversion of testosterone (T) understand hormonal support (high intratesticular testosterone, T/follicle Stimulating Hormone, FSH) and attainment of lower testis temperature for normal spermatogenesis understand androgenic and anabolic effects of testosterone Professor Lau Ying CUHK 2025 2 Intended Learning Objectives: At the end of this lecture, students should be able to: understand hypothalamic-pituitary-testicular axis and feedback control describe the testis and spermatogenesis understand testicular steroidogenesis and conversion of testosterone (T) understand hormonal support (high intratesticular testosterone, T/follicle Stimulating Hormone, FSH) and attainment of lower testis temperature for normal spermatogenesis understand androgenic and anabolic effects of testosterone Professor Lau Ying CUHK 2025 3 What are hormones? Chemical substances secreted in a small amount from an endocrine gland directly to the bloodstream in response to stimulus to cause physiological responses at the target tissues. Professor Lau Ying CUHK 2025 4  How hypothalamus controls anterior pituitary? By the secretion of hypothalamic- releasing and hypothalamic inhibitory hormones into the primary capillary plexus of the hypothalamo-hypophyseal portal system, which travel through portal veins to act on specific receptors on different pituitary cells to secrete their respective hormones. Professor Lau Ying CUHK 2025 5 Hypothalamic-Pituitary-Gonadal (HPG) Axis The male testis consists of tightly packed seminiferous tubules. Within these tubules the formation of sperm (spermatogenesis)occurs. Leydig cells between the tubules secrete the male steroid, testosterone (T) and Sertoli cells secrete a peptide hormone, inhibin. Sertoli cells also feed the maturing sperm. Secretion of testosterone (T) at puberty initiates spermatogenesis, induces development of the male accessory organs, stimulates protein synthesis, induces male secondary sexual characteristics, and increases sex drive. Professor Lau Ying CUHK 2025 6 Hypothalamic-Pituitary-Gonadal (HPG) Axis 2 Testicular function, including the action of the Leydig and Sertoli cells, is stimulated by two tropic hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary. Release of these tropic hormones is under hypothalamic control through the pulsatile release of the neurohormone, gonadotropin releasing hormone (GnRH). Testosterone (T) and inhibin inhibit the hypothalamus and/or the pituitary glands. Professor Lau Ying CUHK 2025 7 Professor Lau Ying CUHK 2025 8 Male Reproductive Hormones FSH = Follicle-stimulating hormone LH = Lutenizing hormone Professor Lau Ying CUHK 2024 9 Male Reproductive Hormones Control GnRH = Gonadotropin- releasing hormone) FSH = Follicle- stimulating hormone LH = Lutenizing hormone Professor Lau Ying CUHK 2024 10 Professor Lau Ying CUHK 2025 11 Spermatogenesis Spermatogenesis is the origin and development of the sperm cells within the male reproductive organs, the testes. Sperm cells are produced within the testes in structures called seminiferous tubules. Once the sperm has matured, it is transported through the long seminiferous tubules and stored in the epididymis of the testes until it is ready to leave the male body. Professor Lau Ying CUHK 2025 12  Spermatogonium Type A cell Mitosis 2n 2n 2n Type B cell grows 2n Primary spermatocyte Spermatogenesis Meiosis 1st division Process by which Spermatogenesis n n Secondary spermatocytes spermatogonia (immature 2nd division male gametes) develop n n n n Early spermatids into spermatozoa (mature male gametes) Late spermatids Spermatogenesis takes Spermiogenesis 64 to 72 days Spermatozoa [mature sperms] Professor Lau Ying CUHK 2025 13  Spermatogenesis Mitosis of spermatogonium (16 days) - Each diploid (2N) spermatogonium produced two daughter cells: 2N * one remains in contact with the basement 4N membrane of the tubules * one is named as primary spermatocyte that is displaced toward the lumen 2N Meiosis I (24 days) - At the end of meiosis I, the daughter cells are called secondary spermatocytes 1N - Every secondary spermatocyte contains 23 chromosomes, each with a pair of duplicate chromatids Professor Lau Ying CUHK 2025 14 Meiosis II (few hours) - The secondary spermatocytes undergo meiosis II and yield 4 haploid spermatids - Each containing 23 chromosomes Spermiogenesis (24 days) - Each spermatid matures into a single spermatozoon (sperm) (remains to be haploid) Professor Lau Ying CUHK 2025 15 Chromosome Human has 23 pairs of chromosomes 23rd pair of human chromosome is the sex chromosome – determine sex X/Y  Male X/X  Female 23 rd 16 Professor Lau Ying CUHK 2025  Testes with exocrine & endocrine functions Sertoli cells (inside seminiferous tubules) Leydig cells (outside) Exocrine 外分泌腺: Endocrine 内分泌: secrete secrete testicular fluid (transport medium for Testosterone Function sperm) Converts secrete androgen binding protein (ABP) to Dihydrotestosterone (DHT) 二氫睪酮 support spermatogenesis estrogen / estradiol 雌二醇 to stimulate spermatogenesis Under FSH stimulates → ↑ adrogen bindinng LH → ↑ testosterone control protein 10% Professor Lau Ying CUHK 2025 6 17  Leydig cells seminiferous Sertoli cells tubules developing sperm cells Leydig Sertoli (lying on basement cells cells (d) membrane) Sertoli cells Lumen Seminiferous Smooth tubule muscle Sperms Lumen layers containing sperms Professor Lau Ying CUHK 2025 18  Hormonal control of spermatogenesis secrete Hypothalamus GnRH = Gonadotropin-releasing hormone) inhibit secretion GnRH activate convert Anterior pituitary FSH = Follicle-stimulating hormone FSH LH LH = Lutenizing hormone Testes Sertoli cells Leydig cells Androgen binding ABP Testosterone protein (ABP) converts Spermatogenesis DHT Estradiol 雌二醇 Dihydrotestosterone High sperm (DHT) 二氫睪酮 count Professor Lau Ying CUHK 2025 19  To maintain high testosterone level Spermatogenesis requires a high testosterone level, so… leydig cells (secrete testosterone) are very near to seminiferous tubules androgen binding protein (ABP) binds testosterone and helps maintain a high concentration of testosterone within the testes; this is essential for spermatogenesis. re-circulation of testosterone through arterio-venous exchange [counter- current exchange]: exchange of testosterone from systemic veins into spermatic arteries which run parallel but in opposite direction Professor Lau Ying CUHK 2025 20 Counter-current exchanger of heat and testosterone Professor Lau Ying CUHK 2025 21  To maintain low testicular temperature Normal spermatogenesis requires a lower temperature (33 – 34oC) during fetal development, testes undergo testicular descent to move away from the body’s core also through arterio-venous exchange In scrotum, – dartos muscle relaxes → ↓ wrinkling → ↑ scrotal size → ↑ surface area for heat loss – cremaster muscle relaxes at higher temp → scrotum descends away from body core – more sweat from scrotum Professor Lau Ying CUHK 2025 22 Other effects of Testosterone & Dihydrotestosterone Anabolic effects (合成代谢作用): 1) ↑ growth in – bone (↑ mineralization) – muscle (↑ protein formation) 2) ↑ red blood cells by ↑ erythropoietin 3) ↑ sebaceous gland secretion → ↑ acne 4) ↑ Low-density lipoprotein (LDL) but ↓ High-density lipoprotein (HDL) → ↑ risk of cardiovascular diseases Androgenic effects (雄激素作用) : ↑ sex drive/libido Sex characteristics – Develop reproductive organs in the fetus & teenage growth – ↑ hair in pubic, axillary & facial areas – broader shoulder, narrower hip Professor Lau Ying CUHK 2025 23 Quiz A chemical or hormone produced by the testes that causes bodily changes during male puberty? A. Estrogen B. Testosterone C. Luteinizing hormone D. Follicle stimulating hormone Professor Lau Ying CUHK 2025 24 Quiz Where is the male hormone, testosterone, produced? A. Testes B. Vas deferens C. Prostate D. Seminal vesicles Professor Lau Ying CUHK 2025 25 Quiz The ______________ of the testes secrete male hormones, such as testosterone. A. seminiferous tubules B. sustentacular cells C. interstitial cells D. efferent ductiles Professor Lau Ying CUHK 2025 26 Quiz Which of these is not an action of the male androgens? A. deposition of subcutaneous fat on the hips and thighs B. growth of bone and muscle C. growth of facial and axillary hair D. development of male external genitalia Professor Lau Ying CUHK 2025 27 Quiz The ____________________ are the first haploid cells during the process of spermatogenesis. A. spermatogonia B. primary spermatocytes C. secondary spermatocytes D. spermatids Professor Lau Ying CUHK 2025 28 Quiz What is spermiogenesis? A. Spermiogenesis is another name for the process of puberty. B. Spermiogenesis is the sequence of events that leads to the production of spermatozoa. C. Spermiogenesis is the reabsorbing of sperm that are not ejaculated. D. Spermiogenesis is the conversion of spermatids to spermatozoa. Professor Lau Ying CUHK 2025 29 Quiz The dartos muscle and cremaster muscle contract in an effort to __________. A. ejaculate sperm B. keep sperm cells warm C. maintain proper temperature for sperm storage and development D. Increase the sexual drive Professor Lau Ying CUHK 2025 30 Quiz Which hormones can facilitate spermatogenesis? I. Follicle-stimulating hormone II. Gonadotropin releasing hormone. III. Dihydrotestosterone IV. Testosterone A. I & II B. II & III C. II & IV D. III & IV Professor Lau Ying CUHK 2025 31 Quiz Which of the following hormones are involved in the development of the secondary sex characteristics in males? A. Estrogen B. Testosterone C. Follicle stimulation hormone D. Gonadotropin-releasing hormone Professor Lau Ying CUHK 2025 32 Quiz Which of the following hormones are involved in causing the release of testosterone? A. Luteinizing hormone B. Follicle stimulating hormone C. Gonadotropin‐releasing hormone D. Progesterone Professor Lau Ying CUHK 2025 33 Quiz Which following cells to testosterone? A. Leydig cells B. Type A cells C. Type B cells D. Sertoli cells Professor Lau Ying CUHK 2025 34 Quiz Which of the following anabolic effects for testosterone EXCEPT? A. Increased red blood cells by increasing erythropoietin B. Increased growth in bone C. Broader shoulder and narrower hip D. Increased sebaceous gland secretion Professor Lau Ying CUHK 2025 35 Quiz Which of the following androgenic effects for testosterone EXCEPT? A. Increase in sex drive B. Increase growth in bone C. Broader shoulder, narrower hip D. Increase hair in pubic, axillary & facial areas Professor Lau Ying CUHK 2025 36 Summary: At the end of this lecture, students should be able to: understand hypothalamic-pituitary-testicular axis and feedback control describe the testis and spermatogenesis understand testicular steroidogenesis and conversion of testosterone (T) understand hormonal support (high intratesticular testosterone, T/follicle Stimulating Hormone, FSH) and attainment of lower testis temperature for normal spermatogenesis understand androgenic and anabolic effects of testosterone Professor Lau Ying CUHK 2025 37  (1) Recommended textbooks Widmaier, E. P., Vander, A. J., Raff, H., & Strang, K. T. (2022). Vander's human physiology: The mechanisms of body function (16th ed.). McGraw-Hill Education. Acknowledgements (2) Recommended references Costanzo, L. S. (2021). Physiology (7th ed.) Elsevier. Dr Judy Chan Boore, J.R.P. (2021). Essentials of anatomy and physiology for contributes some of nursing practice (2nd ed.) SAGE Publications. the previous slides (3) Electronic resources Physiology animations. Visible Body. Argosy Publishing, Inc. Basic Life Sciences for Nursing Students: Physiology. http://libguides.lib.cuhk.edu.hk/c.php?g=532421&p=3642856 Professor Lau Ying CUHK 2025 38