Unit V: Development Male Reproductive System Chapter 25: 909-921

Male Reproductive System

Scrotum Pouch holding testes divided into 2 compartments by median septum Sperm not produced at core body temperature cremaster muscle dartos muscle pampiniform plexus countercurrent heat exchanger

Testes Oval organ, 4 cm long x 2.5 cm in diameter Seminiferous tubules thick germinal epithelium Sustentacular cells/nurse cells promote germ cell development secrete inhibin Interstitial cells Scrotum Cremaster muscle Skin Dartos muscle Superficial fascia Scrotal cavity Epididymis Efferent ductule Ductus deferens Seminiferous tubule Septa Rete testis

Testes 3% born with undescended testes (cryptorchidism) 2 months 3 months Birth Developing testis Connective tissue band 5 mm The connective tissue bands do not get longer as the fetus grows. Late in fetal development, hormones cause the connective tissue band to contract. Testis Scrotum Testes 3% born with undescended testes (cryptorchidism) Location outside pelvic cavity essential for low temperatures needed for sperm production Blood-testis barrier Formed by tight junctions between sustentacular cells -- separating sperm from immune system

Spermatic Ducts Efferent ductules 12 small ciliated ducts Epididymis Reabsorbs 90% of testicular fluid site of sperm maturation and storage (fertile for 60 days) Vas (ductus) deferens muscular tube 45 cm long sympathetic nerve fibers peristalsis during orgasm Ejaculatory duct 2 cm duct empties into urethra

Male Duct System

Seminal vesicles/glands Accessory Glands LM  35 Seminal gland Lumen Secretory pockets Smooth muscle Seminal vesicles/glands pair of glands empty into ejaculatory duct Prostate gland aggregate of glands empty into urethra Bulbourethral glands near bulb of penis; empty into spongy urethra lubricating fluid neutralizes acid of urine LM  35 Prostate gland Connective tissue and smooth muscle Prostatic glands Smooth muscle Capsule Mucous glands Bulbo-urethral gland Lumen LM  140

Penis Internal root; external shaft and glans skin over shaft loosely attached allows expansion extends over glans as prepuce (foreskin) 3 cylindrical bodies of erectile tissue Fill with blood during sexual arousal Membranous urethra Bulb of penis Right crus of penis Corpus spongiosum Corpora cavernosa Scrotum Pubic symphysis Root of penis Body (shaft) of penis Neck Glans of penis External urethral orifice

Penis 3 cylindrical bodies of erectile tissue corpus spongiosum encloses spongy urethra bulbospongiosus muscle corpus cavernosa (2) diverge like arms of a Y ischiocavernosus muscle

Spermatogenesis Spermatogonia (diploid) 2 3 4 5 1 n Secondary spermatocyte Sustentacular cell Spermatid Spermiogenesis Meiosis II Meiosis I Sperm Blood–testis barrier Lumen of seminiferous tubule Primary spermatocyte Type B spermatogonium Tight junction Type A spermatogonium Basement membrane of seminiferous tubule 2n Spermatogonia (diploid) 1. type A - produce more daughter cells until death 2. type B differentiate into primary spermatocytes cells must pass through BTB 3. meiosis I  2 secondary spermatocytes 4. meiosis II  4 spermatids

Spermiogenesis Changes that transform spermatids into spermatozoa 400 million per day

Spermatozoon Head containing the nucleus, acrosome and basal body of the tail flagella Tail (flagellum) midpiece contains mitochondria

Semen / Seminal Fluid 2-5 mL of fluid expelled during orgasm 60% seminal vesicle fluid, 30% prostatic, 10% sperm normal sperm count 50-120 million/mL Other components of semen: fibrinogen - causes clotting  seminogelin prostatic fluid - is a base stabilizing sperm pH at 7.2 to 7.6 prostaglandins - stimulate female peristaltic contractions For capacitation: serine protease - liquefies semen within 20-30 minutes fructose - energy for sperm motility

Excitement Erection of penis is due to parasympathetic triggering of nitric oxide (NO) secretion dilation of deep arteries and filling of lacunae with blood

Orgasm Orgasm (climax) is 15 second reaction that includes the discharge of semen (ejaculation) Ejaculation emission = peristaltic contractions propel sperm through ducts as glandular secretions are added expulsion = semen in urethra activates muscular contractions that lead to expulsion

Resolution Sympathetic signals reduce blood flow to penis penis becomes soft and flaccid Cardiovascular and respiratory responses return to normal Refractory period (10 minutes to few hours)