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Male Reproductive System

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Male Reproductive Organs scrotum and testes ducts accessory sex glands penis

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Male Reproductive Organs

penis

testicle within scrotum

epididymis

ductus deferens

seminal vesicleprostate gland

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Scrotum (cont.)

pendulous sac of loose skin and fascia supports testes divided internally by medial septum,

supporting each testis left testes is usually suspended lower

than the right so they are not compressed against each other

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Scrotum (cont.)

location (outside the body) and muscle fibers regulate temperature of the testes

production and survival of sperm require temperature about 3o lower than normal body temperature

contains Dartos muscle

- contains smooth muscle fibers

- causes wrinkling of scrotum

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Cremaster Muscle continuation of internal oblique muscle stimulation by touch or cold results in

contraction of muscle pulling testicles closer to the body

presence of cremasteric reflex indicates integrity of the first lumbar nerve segment

absence of reflex indicates damage

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Testes primary sex organs; male gonads paired oval glands two inches long, one inch in diameter develop high in posterior fetal abdominal wall descend into scrotum during seventh month

of fetal development suspended in scrotum by spermatic cord

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Testes (cont.)

Produce:

- sperm

- testosterone divided into compartments (about 250) called

lobules formed by inward extensions of tunica albuginea

- contain several highly coiled tubules called seminiferous tubules

spermatozoa are formed in walls of tubules

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Covering of Testes tunica vaginalis

- pouch-like sac of peritoneum

- formed during descent of the testes tunica albuginea

- internal to tunica vaginalis

- dense, white, fibrous tissue

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Cryptorchidism

occurs when testes fail to descend into scrotum results in sterility because of higher temperature in

pelvic cavity

- higher temperature destroys cells involved in development of sperm cells

Treatment:

- human growth hormone

- surgery

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Seminiferous Tubules Consists of:

- spermatogenic cells

- sustenacular cells

- blood-testis barrier

- basement membrane

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Spermatogenic Cells line walls of seminiferous tubules towards lumen of tubules cells are

progressively more mature Cells in various stages of development:

- spermatogonia

- primary spermatocytes

- secondary spermatocytes

- spermatids

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Spermatogonia most immature cells lie next to basement membrane have 46 chromosomes (diploid)

Primary Spermatocytes produce four spermatids have 46 chromosomes (diploid)

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Secondary Spermatocytes cells formed by first nuclear division

(reduction division) each cell has 23 chromosomes (haploid)

Spermatids cells formed by second nuclear division

(equatorial division) - mitotic each cell has 23 chromosomes (haploid)

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Sustentacular Cells extend from outer basement membrane to the

lumen support and nourish developing cells immature cells are embedded in luminal

membranes secrete inhibin

- protein hormone

- directly affects anterior pituitary by inhibiting FSH secretion

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Follicle-Stimulating Hormone FSH encourages spermatogenesis and

stimulates sustentacular cells once adequate spermatogenesis level is

achieved, inhibin is secreted

- inhibits FSH secretion and decreases spermatogenesis

if spermatogenesis occurs too slowly, lack of inhibin permits FSH secretion

- increases rate of spermatogenesis

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Blood-Testis Barrier

developing sperm have surface antigens recognized as foreign by immune system

prevents an immune response against sperm

isolates cells from blood

Basement Membrane surrounds each seminiferous tubule

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Mature Sperm travel through seminiferous tubules to

straight tubules through rete testis and from testes into epididymis

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Epididymis

half-moon-shaped organ encircling posterior of each testis

site of sperm maturation contains highly coiled tube called the ductus

epididymis used for storage of spermatozoa continuous with ductus deferens during ejaculation, muscle contractions move

sperm and seminal fluid into ductus deferens

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Ductus Deferens also called vas deferens or seminal duct 18 inch long tube carries spermatozoa from epididymis of

each testis to an ejaculatory duct ascends along posterior border of

epididymis

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Ductus Deferens (cont.) enters pelvic cavity through inguinal canal loops over side and down posterior surface

of urinary bladder terminal end is called ampulla stores sperm and moves sperm from

epididymis to urethra seminal vesicle joins at distal end of

ampulla

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Vasectomy method of sterilization portion of each ductus deferens is

removed sperm production continues but cannot

be expelled from body

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Ejaculatory Duct distal end of ampulla one inch long formed from union of duct from seminal

vesicle and ductus deferens passes into prostate gland joins prostatic urethra eject sperm into prostatatic urethra just

prior to ejaculation

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Urethra tube extends from urinary bladder to tip of penis about 8 inches long Three parts:

- prostatic urethra

- membranous urethra

- spongy urethra

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Prostatic Urethra passes through prostate gland

Membranous Urethra passes through urogenital diaphragm

Spongy Urethra passes through corpus spongiosum of

penis

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Male Reproductive Glands seminal vesicles prostate gland bulbourethral glands

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Seminal Vesicles paired, convoluted, pouch-like structures posterior to and at base of urinary bladder secrete an alkaline, viscous fluid

- contains fructose, prostaglandins, and fibrinogen

- helps to neutralize acid of female tract

- provides nourishment for sperm

- 60% of the volume of semen

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Fructose used for ATP production

Prostaglandins contribute to sperm motility and viability may also stimulate muscular contraction

within female reproductive tract

Fibrinogen aids in semen coagulation

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Prostate Gland single, donut-shaped, walnut size inferior to urinary bladder surrounds superior portion of urethra secretes milky, slightly acidic fluid

- contains citric acid, acid phosphate, clotting emzymes, and fibrinolysin

- aids in sperm motility and viability

- 25% of the volume of semen

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Bulbourethral Gland also known as Cowper’s glands paired, size of peas lie beneath prostate gland on either side of

membranous urethra ducts open into spongy urethra secrete alkaline, mucus-containing fluid

- neutralizes acid ; lubricates end of penis

- 10% of the volume of semen

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Penis cylindrical organ transports urine and semen through urethra

to the outside of body Consists of:

- body

- glans penis

- root

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Body of the Penis composed of three cylindrical masses of

spongy erectile tissue enclosed in fascia and skin permeated by

blood sinuses sexual stimulation causes dilation of arteries

supplying penis blood accumulates in erectile tissue, and penis

swells and elongates, producing an erection

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Erectile Tissue corpora cavernosa penis

- two dorsolateral masses corpus spongiosum penis

- smaller midventral mass

- contains spongy urethra

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Glans Penis distal end of corpus spongiosum slightly enlarged forms tip of penis Anatomy:

- corona

- external urethral orifice

- prepuce or foreskin

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Corona margin of glans penis

External Urethral Orifice slitlike opening of urethra

Prepuce or Foreskin covers the glans penis often removed in circumcision

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Circumcision removal of part or all of the prepuce many physicians believe it decreases risk of

urinary tract infections, possible protection from penile cancer, and lowers risk of sexually transmitted diseases

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Root of Penis attached portion Consists of:

- bulb of penis

expanded portion of the base of the corpus spongiosum penis

- crura

separated and tapered portions of the corpora cavernosa penis

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Semen Mixture of:

- sperm secretions of the seminal vesicles,

prostate gland, and bulbourethral glands

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Characteristics of Semen volume

- 2.3 - 2.5 ml per ejaculation color

- milky appearance because of prostate secretion

sperm count

- 50 - 150 million sperm per ml

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Characteristics of Semen (cont.)

motility of sperm

- at least 60% active, good forward motility in order to be viable

pH is slightly alkaline (7.20 - 7.60) specific gravity - denser than water (1.0280) morphology

- at least 80% normally shaped in order to be viable

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Characteristics of Semen (cont.)

antibiotics - seminalplasmin

- has ability to destroy certain bacteria nutrients - fructose

- provides energy source necessary for sperm motility

buffers - phosphate and bicarbonate

- maintain relatively constant pH of semen

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Characteristics of Semen (cont.)

enzymes - hyaluronidase, proteinases

- digest material covering ovum clotting enzymes

- coagulate semen fibrinolysin

- liquifies coagulated semen

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Hormonal Control of Male Reproductive System Controlled by:

- GnRH (gonadotropin releasing hormone)

- FSH (follicle-stimulating hormone)

- LH (luteinizing hormone)

- inhibin

- testosterone

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Gonadotropin Releasing Hormone secreted by hypothalamus carried by anterior pituitary gland

- stimulates the release of gonadotropins,

follicle-stimulating hormone, and luteinizing hormone

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Follicle-Stimulating Hormone stimulates sustentacular cells in

seminiferous tubules

- secrete chemicals that stimulate spermatogenesis

- secrete inhibin which has a negative feedback effect on anterior pituitary gland, inhibiting secretion of FSH

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Luteinizing Hormone stimulates interstitial endocrinocytes

located in spaces within seminiferous tubules

stimulates testosterone secretion

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Androgens male sex hormones testosterone is principal androgen

- synthesized from cholesterol in the testes

- in some target cells testosterone is not active and must be reduced and converted into dihydrotestosterone (DHT)

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Androgen Functions male pattern of development before

birth sexual characteristics sexual functions metabolism

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Male Pattern of Development Before Birth development of reproductive system ducts descent of testes development of external genitals (by DHT) converts some androgens into estrogens

which aid in brain development

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Sexual Characteristics development and enlargement of male

sex organs development of male secondary sex

characteristics

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Male Secondary Sex Characteristics muscular and skeletal growth wide shoulders, narrow hips pubic, axillary, facial, and chest hair

growth thickening of skin increased sebaceous gland secretion enlargement of larynx and deepening of

voice

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Sexual Functions male sexual behavior spermatogenesis sex drive

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Metabolism androgens are anabolic hormones which

stimulate protein synthesis

- leading to heavier muscle and bone mass in males

cause cessation of bone growth by stimulating closure of epiphyseal plate

increase rate of metabolism and production of red blood cells