Reproduction Chapter 27
Male Reproductive System Reproductive organs Testis Scrotum Reproductive tract Epididymis Vas Deferens Spermatic cord Accessory glands & organs Seminal vesicles Prostate gland Bulbourethral gland Penis
Gamete Production Testes Spermatogenesis- VERY temperature sensitive Spermatozoa (sperm) ~100-300 million/ day Production begins at puberty Spermatogenesis- VERY temperature sensitive Optimal temperature ~3-4C below body temp
Pendulous Testes
Scrotum Bi-chambered external pouch of skin Function Houses testes Protects testes Regulates testicular temperature Scrotum modifications for temperature regulation & protection Low insulation- sparse hair & thin skin Sweat glands Vascularization- countercurrent blood flow Musculature Ennervation
Low Insulation Little insulating fat Sparse hair Sweat glands
Musculature Dartos muscle (tunic) Cremaster muscle Muscle inserting into scrotal skin Contraction tenses skin of scrotum & raises testis wrinkling Cremaster muscle Surrounds testis Contraction pulls testis closer to body Cold- contraction Warm- relaxation
Vascularization Pampiniform plexus Countercurrent blood flow Cool venous blood surrounds incoming arteries Actively cools incoming blood & warms outgoing blood Testes always surrounded by cool blood Testes
Varicocele Most common curable cause of infertility Equivalent of varicose veins
Scrotum Nerves Behavioral protection
Testis Paired gonads inside of scrotum Surrounded by tunic Function Tunica albuginea Function Spermatogenesis- sperm formation Hormone production Androgens- testosterone
Tunica albuginea “White Coat”
Testis Structure Seminiferous tubules Rete testis Sertoli cells Rete testis Interstitial (Leydig) cells
Seminiferous Tubules Actual site of spermatogenesis 800+ coiled tubes Maximizes surface area Bulk of testes tissue
Figure: 17-02 Title: The internal structure of the testis and epididymis. Caption:
Figure: 17-03b Title: The stages of spermatogenesis in the wall of a seminiferous tubule. Caption: Bottom: As the cells that will become sperm develop, they are pushed from the outer wall of the tubule to the central canal.
Sertoli Cells Lots tight junctions in cells near basement membrane Form blood testes barrier Protects from pathogens, mutagens, immune cells
Spermatogenesis & Androgen Production Stimulated by Brain
Interstitial (Leydig) Cells Located between seminiferous tubules Site of androgen production Surrounded by capillaries Stimulated to produce by increased levels of testosterone by Leuteinizing Hormone
Interstitial (Leydig) Cells
Interstitial (Leydig) Cells
Testosterone Levels
Testosterone Levels
Testosterone Levels
Sperm Path Male reproductive tract continuous- Isolates sperm
Rete Testis Located within the testis Site of merging seminiferous tubules exiting from testes Common pathway for exiting sperm
Male Reproductive Tract
Epididymis Testicular cap Single coiled tubule 6M long Receives sperm from rete testis Function Secretes/absorbs nourishing fluid Recycles damaged spermatozoa Stores spermatozoa Up to 2 weeks Allows time for maturation
Epididymis
Epididymis
Tunica Vaginalis Surrounds testes & epididymis Allows free movement of testes inside of scrotum
Vas Deferens Aka Ductus Deferens Single tubule carries sperm from epididymis into abdominal cavity 45 cm long Muscular tube Passes thru inguinal canal Connects to urethra at prostate
Vas Deferens
Spermatic Cord Tissue located within the inguinal canal Combination of tissues Vas deferens Pampiniform plexus Testicular tissue Arteries & nerves Muscle
Inguinal Canal
Testis Torsion
Accessory Glands Seminal vesicle Prostate Bulbourethral gland
Accessory Glands Secrete seminal fluid Nourish, activate & protect sperm Semen (seed) Glandular secretions (99%) & sperm (1%) ~2-5 mls per ejaculation ~50-200 million sperm per ml of ejaculate 100-700 million per ejaculation 50 reach oocyte
Seminal Vesicle Paired elongate glands Located posterior & inferior to bladder Secretes (60% semen) Fructose “sugar” Energy source Prostaglandins Activate sperm motility Stimulate contractions of female reproductive tract Fibrinogen Clotting factors Slows sperm
Prostate Large solid single gland Located at base of bladder Houses prostatic urethra Secretes (20-30%) Enzymes Aid in activating sperm motility Antibiotic Mucus degradation Alkaline fluid Neutralize female reproductive tract Citric acid, proteolytic enzymes Antioxidants ???secretions of unknown function
Prostate Cancer Most common cancer in men 3rd most common cause of death in men Disease of well developed nations Diet & lifestyle High fat diet High testosterone levels Cadmium exposure Low rates in Japanese & vegetarians By age 80 70% men will have it
Bulbourethral Gland Small paired gland Located at the base of the penis Secretes alkaline mucus Neutralize urinary acids Lubrication
Penis Copulatory & excretory organ Excretory Copulatory Penile urethra Carries urine & sperm Copulatory 3 cylindrical masses or erectile tissue 2 corpora cavernosa (rt & lt) Corpus spongiosum
Corpora Cavernosa Right & left Primary erectile tissue Paired superior masses Provides the majority of rigidity & length Pulls urethra taught by pushing glans Crus posterior expansions “anchor” tissue against pelvic bone
Corpora Cavernosa
Corpora Cavernosa
Sinusoids & Trabeculae Smooth muscle holds closed Vasoconstriction
Rich Blood Supply
Corpora Spongiosum Inferior mass Contains Penile urethra Glans Secondary erectile tissue Contains Penile urethra Glans Anterior expansion Bulb of penis Posterior expansion Prepuce Folds of skin covering glans
Houses Penile Urethra
Prepuce Protects Produces smegma Waxy substance
2300 BC
Male-female Comparison Penis Corpora cavernosa Corpora spongiosum Prox shaft of penis Prostate Bulbourethral glands Scrotum Clitoris Corpora cavernosa Corpora spongiosum Labia minora Paraurethral glands Grtr vestibular gland Labia Majora