The Male Reproductive System
The Male Reproductive System
The Male Reproductive System Main Topics General Information Testis Ducts Accessory Sex Glands Penis Supporting Ligaments Male Reproductive Physiology
Testis Overview Connective Tissue Coverings (tunica vaginalis; tunica albuginea) & supporting structures (scrotum) Seminiferous Tubules – site of sperm production
Ducts Overview Ducts of the Testis Ducts of the Epididymis Ductus Deferens (vas deferens; seminal duct) Ejaculatory ducts Urethra
Accessory Sex Glands Overview Seminal Vesicles Prostate Gland Bulbourethral Glands (Cowper’s glands)
The Penis Overview Body Root Glans Penis
Male Reproductive Physiology Overview Erection Emission Ejaculation
General Information Gonads (testes; ovaries) Ducts production of gametes (sperm; secondary oocytes); secrete hormones Ducts transport and store gametes Accessory sex glands produce materials that support gametes Supporting structures – penis; uterus
Testis Connective Tissue Coverings (tunica vaginalis; tunica albuginea) & supporting structures (scrotum) Seminiferous Tubules – site of sperm production
The Testis
The Testis Connective Tissue Coverings Tunica vaginalis outer, serous membrane that partially covers the testis Tunica albuginea inner, dense fibrous capsule extends inward forming septa that divide each testis into internal compartments (lobules) lobules - 200-300 compartments within the testis; each contains 1-3 tightly coiled tubules (seminiferous tubules) packed in an areolar connective tissue
The Testis Connective Tissue Coverings Scrotum connective tissue sac that supports the testes contains skeletal muscle (cremaster) and smooth muscle (dartos) which regulate the temperature of the testes by controlling the distance between the testes and the body
The Testis Seminiferous Tubules dead-ended, coiled tubules outer basement membrane layer inner lumen which empties into the straight tubules site of sperm production (spermatogenesis)
Seminiferous Tubules
Meiosis
Seminiferous Tubules Spermatogenic cells Spermatogenic cells - sperm-forming cells; successive layers of developing cells, from most immature (next to basement membrane) to most mature (next to lumen spermatogonia diploid (2n) stem cells that develop from primordial germ cells; lie dormant until puberty; lie next to basement membrane primary spermatocytes - differentiated (more mature) diploid daughter cells of spermatogonia mitosis secondary spermatocytes - haploid (n) daughter cells of primary spermatocytes which have undergone reduction division (meiosis I) spermatids - haploid daughter cells of secondary spermatocytes which have undergone equatorial division (meiosis II); lie close to lumen; each diploid primary spermatocyte produces four haploid spermatids sperm (spermatozoa)
Spermatogenic cells
Sperm maturation of spermatids (spermiogenesis) mature at rate of about 300 million per day once ejaculated, have about a 48 hour survival time within the female reproductive tract
Sperm head mid-piece tail contains DNA and acrosome (lysosome-like structure that aids in the penetration of the secondary oocyte) mid-piece contains numerous mitochondria that supply ATP for locomotion tail flagellum; propels the sperm cell
The Seminiferous Tubules Sustentacular cells (Sertoli cells) extend from the basement membrane to the lumen of the tubule spermatogenic cells are embedded within the Sertoli cells basal surface forms tight junctions with neighboring cells forms a blood-testis barrier
Sustentacular cells (Sertoli cells) Functions support, protect, & nourish developing spermatogenic cells phagocytize excess spermatid cytoplasm mediate effects of testosterone and FSH control movements of spermatogenic cells control release of sperm into the lumen produce fluid for sperm transport secretes hormone, inhibin, which helps regulate sperm production by inhibiting secretion of FSH from the anterior pituitary gland
Sustentacular Cells
The Seminiferous Tubules Interstitial endocrinocytes (Leydig cells) fill spaces between adjacent seminiferous tubules secrete testosterone
Interstitial Endocrinocytes (Leydig cells)
Ducts Ducts of the Testis Ducts of the Epididymis Ductus Deferens (vas deferens; seminal duct) Ejaculatory ducts Urethra
Ducts of the Testis Straight tubule Rete testis single, simple columnar-lined, short, straight tubule collects sperm (& seminiferous fluid) from the seminiferous tubules of the lobule empties into the rete testis Rete testis network of anastomosing channels lined with simple squamous to simple cuboidal epithelium collects sperm from the straight tubules of all the lobules
Epidiymis comma-shaped organ lying along the posterior surface of the testis consists of a: head (mainly efferent ducts) body (ductus epididymis) tail (ductus epididymis)
Ducts of the Epididymis Efferent ducts 10-15 coiled tubules that drain the rete testis forms the head of the epididymis empties into the ductus epididymis Ductus epididymis tightly coiled (20 ft. in uncoiled length) tubule lined by pseudostratified columnar epithelium encircled by smooth muscle layers comprises the body & tail of the epididymis collects sperm from the efferent ducts empties into the vas deferens
Ductus Deferens (vas deferens; seminal duct) 18” long lined by pseudostratified columnar epithelium ascends along the posterior border of the epididymis, through the inguinal canal, over the ureter descends retroperitoneally behind the bladder toward the urethra Ampulla of ductus deferens dilated, terminal segment of the vas deferens joins the excretory duct of the seminal vesicle to form the ejaculatory duct
Vas Deferens Functions stores sperm (up to several months) conveys sperm from epididymis toward the urethra by peristaltic contractions of its smooth muscular layers (inner & outer longitudinal; middle circular)
Ejaculatory Ducts 1” long formed by the union of the duct from the seminal vesicle and the ampulla of the vas deferens forcibly ejects sperm into the prostatic urethra (it pierces the prostate gland) just before ejaculation (expulsion of semen from the urethra)
Urethra passageway for semen through the prostatic urethra through the membranous urethra through the spongy urethra through the external urethral orifice
Accessory Sex Glands Overview Seminal Vesicles Prostate Gland Bulbourethral Glands (Cowper’s glands)
Semen & Seminal Fluid Semen Seminal fluid slightly alkaline mixture of sperm and seminal fluid provides sperm with a transportation medium and nutrients neutralizes hostile acidic environment of male urethra and female vagina Seminal fluid liquid portion of semen that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate gland, and bulbourethral glands
Seminal Vesicles paired, convoluted, pouch-like structures 2” in length lie posterior to and at the base of the bladder Secretions alkaline, viscous fluid contains fructose (for ATP production by sperm), prostaglandins (contribute to sperm motility & viability), semenogelin (protein coagulator of ejaculated semen) 60% of seminal volume
Prostate Gland single, doughnut-shaped gland surrounds the prostatic urethra prostatic secretions enter prostatic urethra through many prostatic ducts Secretions milky, slightly acidic fluid contains citrate (for ATP production by sperm) acid phosphatase proteolytic enzymes [prostate-specific antigen (PSA); pepsinogen; lysozyme] which liquefy coagulated semen 25% of seminal volume
Bulbourethral Glands (Cowper’s glands) paired, pea-sized glands lie on either side of the membranous urethra within the urogenital diaphragm ducts open into the spongy urethra Secretions during sexual arousal, secrete alkaline substance (neutralizes acidic environment of urethra) and mucus (for lubrication)
The Penis Body Root Glans Penis
The Penis Body Body- composed of three cylindrical masses of erectile tissue; permeated by blood sinuses; each bound by fibrous tissue (tunica albuginea) Corpora cavernosa penis (sing: corpus cavernosum penis) - paired, dorsolateral masses; tapered ends (crura) are attached to the pelvis Corpus spongiosum penis - mid-ventral mass; contains the spongy urethra
The Penis Root Root - consists of the bulb of the penis and the crura of the penis Bulb of the penis - expanded portion of the base of the corpus spongiosum penis; attached to the inferior surface of the urogenital diaphragm; enclosed by the bulbospongiosus muscle Crura (sing: crus) - the tapered ends of the corpora cavernosa penis; attached to the ischial ramus and the inferior pubic ramus; surrounded by the ischiocavernosus muscle
The Penis Glans Penis Glans Penis - distal end of the corpus spongiosum penis Corona - margin of the glans penis External urethral orifice - an enlarged, terminal, slit-like opening Prepuce (foreskin) - loose covering over the glans penis
Male Reproductive Physiology Erection Emission Ejaculation
Male Reproductive Physiology Erection Erection - results from vascular changes Parasympathetic nerve stimulation causes the arteries that supply the penis to dilate allowing large amounts of blood to enter the blood sinuses of the erectile tissue The blood-filled spaces expand compressing the superficial veins that drain the penis and allowing more blood to trapped in the spaces The erectile tissue becomes larger and stiffer
Male Reproductive Physiology Emission the discharge of a small volume of semen before ejaculation due to peristaltic contractions (in the ampulla of the vas deferens, the seminal vesicles, the ejaculatory ducts, and the prostate gland) which propels semen into the spongy urethra
Male Reproductive Physiology Ejaculation Ejaculation - sympathetic nerve stimulation (Ll, L2) causes rhythmic simultaneous muscular contractions of the bulbospongiosus, the ischiocavernosus, and the anal sphincter; propels semen out of the external urethral orifice Simultaneous contraction of the internal urethral sphincter prevents urine leakage from the bladder and semen from entering the bladder
Male Reproductive Physiology