CHAPTER TWENTY-SEVEN: MALE REPRODUCTION The organs of the male reproductive tract can be categorized by function. In addition to serving in a reproductive capacity, several of the male reproductive structures serve a urinary system function. testes ducts accessory sex glands The male gonads, testes, are stored in a protective sac called the scrotum. The scrotum is divided into two isolated compartments by a strip of fibrous connective tissue called the scrotal septum. < scrotal septum < scrotal raphe < unequal suspension < cremaster muscle (skeletal muscle) < dartos muscle (smooth muscle) < spermatic cord: blood vessels, nerves, lymphatic vessels, vas deferens, cremaster muscle < testicular arteries < testicular veins a.k.a. pampiniform plexus • blood flow from testicles • increased surface area for trapping heat & moving it away from testes What are the functions of the scrotum? < testicular support < testicular protection < temperature regulation < sexual experience . . . nerves How do the testicles arrive at/into the scrotum? < inguinal canal < gubernaculum . . . testes to scrotal floor . . . “pull” < descent at 7th month of development • descent failure termed cryptorchidism - increased risk of testicular cancer - increased risk of sterility -1- The testicles are covered by several layers of protective connective tissue. < tunica vaginalis- double layered serous membrane < tunica albuginea -subdivisions into septum/lobules in the testes The tunica albuginea invaginates to form a series of lobules which make up the testicle. Housed within each lobule is a series of “coiled” tubes called seminiferous tubules. Between the seminiferous tubules are cells called interstitial endocrinocytes or Leydig cells. What are the functions of the testicles? < production of sperm < production of testosterone < production of a contribution of fluid to semen < regulates secondary sex characteristics The walls of the seminiferous tubules are a collection of several types of cells. Functionally, these cells can be divided into those which create sperm and others which “support or nourish” the developing sperm. Cells which develop into sperm are termed spermatogenic cells. There are specific names for each cell as it passes through sperm development spermatogenesis. Completion of spermatogenesis takes approximately 65 days. < spermatogonia ( 46 Ch) < 1°spermatocyte (46 Ch) < 2°spermatocyte (23 Ch) < spermatids (23Ch) < “spermiogenesis” < sperm (23 Ch) a.k.a. spermatozoa The onset of spermatogenesis is puberty. Each day a normal male produces 400 million sperm. Let’s add some new terminology to the chromosome numbers and type of spermatogonia cells present at each phase of spermatogenesis. < diploid (2N) < haploid (1N) < type A daughter cell < type B daughter cell -2- Sperm are streamlined versions of spermatids. The loss of the spermatid cytoplasm creates a “sperm.” < head w/acrosome hyaluronidase proteinase < midpiece ATP < flagellum Cells which are located in between spermatogenic cells are the sustentacular cells or Sertoli cells. < tight junctions < blood-testis barrier . . . “self” issues What are the functions of the Sertoli cells? < protection < nourish via blood -testis barrier < phagocytosis of spermatid cytoplasm < < < control spermatogenic cell progression from periphery to lumen contribute fluid to semen secretes inhibin which alters the release of FSH from the anterior pituitary gland -3- The areas surrounding the seminiferous tubules are filled with interstitial cells a.k.a leydig cells or interstitial endocrinocytes. What are the functions of the interstitial cells? < support seminiferous tubules < respond to LH stimulation < testosterone production in response to LH How does hormonal regulation of male reproductive system operate? < hypothalamus GnRH < anterior pituitary FSH: spermatogenic, sertoli cells LH: interstitial cells < interstitial cells testosterone: spermatogenic cell < sertoli cells androgen-binding protein (ABP): spermatogenic cells inhibin: anterior pituitary gland FSH stimulates spermatogenesis and ABP production. ABP binds testosterone at discrete sites in the testes - seminiferous tubule lumen & interstitial fluid. LH (a.k.a. interstitial cell-stimulating hormone ICSH) stimulates interstitial cell production of testosterone from cholesterol. Testosterone stimulates spermatogenesis and ABP production. ABP binds testosterone at discrete sites in the testes - seminiferous tubule lumen & interstitial fluid. ABP is working in positive feedback. Inhibin is produced by the Sertoli cells. It decreases the production of FSH and LH from the anterior pituitary. Inhibin is working in a negative feedback. -4- What are somatic effects of testosterone? What are the somatic effects of dihydrotestosterone (DHT)? Some cells will not respond to testosterone, however, they will respond to a modified form - DHT. For example, the prostate gland responds to DHT not testosterone. NOTE In some neurons of the brain, testosterone is converted into estrogen in order to carry out “brain masculinization”. TESTICULAR DESCENT GENITAL ENLARGEMENT AT PUBERTY INCREASED SEBACEOUS GLAND PRODUCTION AT PUBERTY LARYNX ENLARGEMENT CHARACTERISTIC SKELETAL MUSCLE DEPOSITION CHARACTERISTIC HAIR DEPOSITION SEXUAL BEHAVIOR LIBIDO EPIPHYSEAL PLATE CLOSURE EXTERNAL GENITAL DEVELOPMENT GENITAL ENLARGEMENT AT PUBERTY INCREASED SEBACEOUS GLAND PRODUCTION AT PUBERTY LARYNX ENLARGEMENT CHARACTERISTIC SKELETAL MUSCLE DEPOSITION CHARACTERISTIC HAIR DEPOSITION SEXUAL BEHAVIOR LIBIDO EPIPHYSEAL PLATE CLOSURE ANABOLIC METABOLISM The contents of the testes are collected into a “collection” organ - epididymus. The epididymus sits atop the testes with the head being most superior and the tail most inferior, in orientation. < head efferent ducts < body ductus epididymus < tail ductus epididymus The epididymus consists of pseudostratified ciliated columnar epithelium with sterocilia and a band of smooth muscle called the dartos muscle. -5- What are the functions of the epididymus? < stores sperm < provides swimming instructions to sperm < propels sperm during coitus < reabsorbs old sperm The vas deferens (a.k.a. ductus deferens) in the long tube which transports stored sperm from the epididymus to outside of the body via the urethra. Its passage begins external to the pelvic cavity, proceeding internally into the pelvis where it joins the urethra at the level of the prostate gland. Remember that the vas deferens enters the pelvic cavity through the inguinal canal as part of the spermatic cord. < ampulla of vas deferens < seminal vesicles (x2) 60% semen volume yellowish viscous fluid < < alkaline contribution to semen fructose contribution to semen ascorbic acid contribution to semen vesiculase (a.k.a. semenogelin) for coagulation contribution of semen prostaglandins for sperm motility prostaglandins for sperm viability prostaglandins for vaginal and uterine contractions seminal vesicle ducts (x2) ejaculatory duct (x2) site of sperm and semen mixing propel semen into the prostatic urethra The prostatic urethra is the first region of the urethra where it passes from the urinary bladder through the middle of the prostate gland. < prostatic urethra: prostate gland < membranous urethra: urogenital diaphragm < penile (spongy) urethra: penis < external urethral orifice -6- Along the length of the urethra, various accessory organs provide “input” into the contents of the urethra during ejaculation. < ejaculatory ducts (x2) < prostate gland (x1) • connective tissue capsule • fibromuscular stroma w/ smooth muscle • tubular-alveolar glands The prostate gland serves the following functions. < provides 33% of seminal fluid contributions < milky contribution < provide citrate for conversion to ATP during the Kreb’s cycle < provides substances which enhance sperm motility < provides a gel-liquid transition medium < provides an assortment of proteases involved in the liquid transition • fibrinolysin • hyaluronidase • acid phosphatase < prostate-specific antigen (PSA) The two bulbourethral (a.k.a. Cowper’s glands) are located w/in the urogenital diaphragm. The ducts of the bulbourethral glands empty their contents into the spongy urethra. The functions of these glands include < small contribution to semen < contribute a thick, clear mucus < provides mucus to coat the urethra prior to ejaculation < provides alkaline mucus to reduce the acidity of urethral lumen created by presence of residual urine -7- The penis (Latin for “tail”) is subdivided into three regions - root, shaft/body and glans penis. While the length of the penis contains “cores” of tissue, the arrangement of these cores differs w/in each region of the penis. The two “cores” of erectile tissue are termed corpus spongiosum and corpora cavernosa. < dense connective tissue sheath < corupus spongiosum (x1) w/ spongy urethra < copora cavernosa (x2) each w/ a deep arteries < dorsal blood vessels < dorsal nerves The regions of the two corpora cavernosa varies as these erectile tissues progress proximal to distal. < crus (“winged”) region at the root of the penis - proximally < consistent diameter passing through the shaft of the penis The corpus spongiosum varies as this erectile tissue progress proximal to distal. < consistent diameter passing through the root and shaft of the penis < enlarged regions, corona & glans penis, at the distal end of the penis -8- SEMEN How does semen differ from sperm and seminal fluid? What is the final pH of semen? 7.2 -7.6 What is the role of the chemical, seminalplasmin, found in semen? What is the final semen volume? 2-5 ml What is the sperm count? 50 -130 million sperm MALE SEXUAL RESPONSE This is a two part response. < erection • stimulation triggers the parasympathetic reflex • release of nitric oxide (NO) locally • vasodilation of deep arteries of corpora cavernosa • swelling of the corpora cavernosa lead to stiffening of the penis < ejaculation • peaked stimulation of the spinal reflex at L1 and L2 triggers sympathetic response • reproductive glands propel at speed of 200 inches/second at same time • bladder sphincter muscle contract preventing urine from leaving the bladder RECENT ISSUES < decrease sperm production • hydrocarbons • estrogenic chemicals • clothing choices • antibiotics i.e. TCN < abnormal sperm production • radiation • lead exposure • pesticide exposure • lack of selenium • marijuana • alcoholism < erectile dysfunction . . . low levels of nitric oxide • causes medication usage: BP, antihistamines (Tagamet), antidepressants (i.e. Prosac) diseases: diabetes mellitus, arteriosclerosis, varicose veins trauma cancer • sidenafil (Viagra) MOA: increases NO levels side effects: blue/green vision, stuffy nose, death usage in women? -9- HOMEOSTATIC IMBALANCES Cause benign prostatic hyperplasia enlarged prostate gland treatments: medications cryptoorchidism undescending testes hypospadiasis abnormal urethral opening impotence failure to achieve erection inguinal hernia gut bulges into the inguinal canal prostate cancer tumor within the prostate gland treatments: medications, surgery, radiation prostatitis inflammation of the prostate gland testicular cancer rare, young males w/ hx of orchitis, 90% cure rate with testicle remoal MEDICAL PROCEDURES Procedure Details castration removal of testicles circumcision removal of prepuce orchitis testicular lumps “mumps” orchiectomy removal of a testicle vasectomy vas deferens is severed October 17, 2006 (11:12am) C:\MyFiles\LCCC\a&p hybrid\lecture_f\ap.lec_malerepro.wpd -10-