Male Reproductive System PDF

Chapter 27 Male Reproductive System  Male Reproductive System Terminology – Meiosis = process by which sperm and egg are made – Gametes (sex cells)= Sperm and egg – Gonads = ovary and testis – Zygote (fertilized egg) has combination of both parents’ genes...

Chapter 27 Male Reproductive System  Male Reproductive System Terminology – Meiosis = process by which sperm and egg are made – Gametes (sex cells)= Sperm and egg – Gonads = ovary and testis – Zygote (fertilized egg) has combination of both parents’ genes – Human Cells: Diploid: the cell contains two sets of DNA (hair, skin, intestine, etc.) – The diploid number of chromosomes is 46. Haploid: the cell contains one set of DNA (gametes) – The haploid number of chromosomes is 23. Male Reproductive Anatomy  Scrotum and Testes Two testes each contained within a scrotum (sac) – The testes are located on the outside of the body Must be at least 2-3 degrees cooler for the normal production of sperm – Left usually lower than the right – Skin has sebaceous glands, sparse hair, rich sensory innervation, dark pigmentation – Internal medium septum divides scrotum into left and right compartments  The Scrotum Scrotum has three mechanisms to regulate temperature of testes – Cremaster: strips of int. abdominal oblique muscle (surrounds spermaic cord) In cold temperatures, contracts and draws testes upward toward body In warm temperatures, relaxes suspending testes further from body – Dartos fascia: subcutaneous layer of smooth muscle Contracts when cold, wrinkling the scrotum, holding testes against warm body Reduces surface area of the scrotum and heat loss – Pampiniform plexus: veins from the testes that surrounds the testicular artery and spermatic cord without would inhibit sperm production Removes heat from the descending arterial blood By the time it reaches the testis, the blood is 1.5° to 2.5°C cooler The Scrotum and Spermatic Cord  Testes Testes (testicles)—combined endocrine and exocrine glands that produce sex hormones and sperm – Tunica Vaginalis (peritoneum) cover them anteriorly & laterally Serous membrane, reduces friction – Tunica Albuginea White fibrous capsule on the testes – Connective tissue septa divides testes into 250-300 wedge shaped lobules Lobules contain seminiferous tubules interstitial endocrine cells (Leydig cells) surround seminiferous tubules – Secrete androsterone and testosterone – when LH from the anterior pituitary acts on them Ductus deferens Epididymis Rete Scrotum testis Skin Dartos muscle Superficial scrotal fascia Cremaster Seminiferous Tunica vaginalis tubules Tunica albuginea Septa testis a A transverse section of the scrotum and testes  The Testes Seminiferous tubules—ducts where sperm are produced One to three in each lobule (32 inches each, 1/2 mile in each testis) Each tubule lined with Germ cells (become sperm) Nurse cells Protect & promote their development Interstitial endocrine cells (leydig cells) between tubules produce testosterone Stimulated by LH  Testosterone Made by the testis will cause: – Male hair pattern forms – Enlargement of genitalia – Increased sex drive – Enlargement of thyroid cartilage – Protein anabolism = allows for muscle & bone growth in the male  Spermatogenesis - FSH Process of sperm production in seminiferous tubules: – Spermatogonium: stem cells undergo mitosis Divides into 2 cells – Spermatogonium (stays near basement membrane) – Primary spermatocyte (diploid and moves toward lumen) – Chromosomes replicate during interphase and have duplicate copies (count the centromeres) – Meiosis I Primary spermatocyte divides into 2 secondary spermatocyte – Each spermatocyte has 23 chromosomes but with duplicates (DNA doubles) – Crossing over creates new combinations – Meiosis II Both secondary spermatocytes divides – 4 haploid spermatids (23 chromosomes only = haploid) – Spermiogenesis https://www.youtube.com/watch?v=VzDMG7ke69g  Spermiogenesis Spermatid to sperm Completed in 24 days Occurs as sperm travel from rete testes to epididymis 1. Head compacts 2. Gain of flagella and addition acrosome cap 3. Shed cytoplasm 4. Develops a middle piece  Nurse (Sertoli) Cells Support Spermiogenesis – Surround and support spermatids Providing nutrients and promote development Phagocytize shed cytoplasm Maintain blood testis barrier – Isolates seminiferous tubules from general circulation – protect developing sperm from immune system Support mitosis and Meiosis – Promotes division of spermatogonia – meiotic division of spermatocytes Secretion of “inhibin” – blocks effects of FSH  Cryptorchidism “Hidden testes” – Condition where the testes has not descended into the scrotal sack – 3% of male births – Most descend within 1st year – Testosterone injection or surgery can draw testes into scrotum This can lead to – sterility – Testicular cancer  Epididymis Start of the reproductive tract (head, body and tail) – 23 feet long!! Site of sperm maturation and storage – Fertile for 40-60 days – Immobile sperm moved there by cilia – Sperm mature as they travel through – If not ejaculated, they disintegrate and are reabsorbed  Ductus (vas) Deferens Muscular tube that transports sperm Passes from scrotum to posterior surface of bladder Duct widens to form ampulla where sperm can be stored for months Loops around ureter and widens into an ampulla before entering the prostate gland Forms ejaculatory duct via union with duct from seminal vesicle  Spermatic Cord The spermatic cord is formed from the following structures that follows the testes into the scrotal sack: – cremaster muscle – testicular artery – veins – lymph vessels – nerves – ductus deferens  Pathway for the flow of Sperm Seminiferous tubule Rete testis Epididymis Ductus deferens Ejaculatory duct Urethra  Urethra Prostatic Urethra – Bladder à prostate – Transitional epithelium Membranous Urethra – From prostate through pelvic cavity – Pseudostratified epithelium Penile Urethra – Through the penis – Psuedostratified squamous epithelium – End stratified squamous  Accessory Glands Seminal glands Prostate glands Bulbo-urethral gland Functions: – Where semen is formed – Sperm are activated – Provide nutrients for motility – Propel sperm by peristalsis – Produce buffers  Accessory Glands Seminal Glands (Vesicles) – Pair of glands posterior to bladder – Joins Ductus Deferens to form ejaculatory duct – 65-70% of semen is made by seminal vesicles – Thick mucus like secretion Fructose (for ATP) Prostaglandins (smooth muscle contraction in male & female) Fibrinogen (clotting protein) – Semen clot within vagina Alkaline pH (neutralize the acidity of the vagina)  Accessory Glands Prostate Gland – Secretes prostatic fluid – 25-30% of semen – Slightly acidic rich in enzymes – Citrate – Acid Phosphatase & amylase Prevents sperm coagulation in vagina Prostatitis – Inflammation in mostly older men  Accessory Glands Bulbourethral glands (Cowper’s Gland)