HUMAN ANATOMY AND PHYSIOLOGY: MALE REPRODUCTIVE SYSTEM

LECTURE QUESTION 1

Obviously, the function of the reproductive system is to provide both the cells and physiology to produce viable offspring. In that light, outline meiosis, identify gonads, gametes, reproductive hormones, the process of fertilization, zygote, and accessory reproductive organs.

REPRODUCTIVE SYSTEM

Primary sex organs (gonads): testes and ovaries Produce sex cells (gametes) Secrete steroid sex hormones

Androgens (males) Estrogens and progesterone (females)

Accessory reproductive organs: ducts, glands, and external genitalia

LECTURE QUESTION 2-4 Describe the structure and function of the

testes, and explain the importance of their location in the scrotum.

Explain the male duct system by naming each organ and describing the role of the each organ involved.

List the three male accessory glands and describe their contributions to the formation of semen.

MALE REPRODUCTIVE SYSTEMAKA: THE ADVENTURES OF “SPERM MAN”

Testes (within the scrotum) produce sperm

Sperm are delivered to the exterior through a system of ducts Epididymis, ductus

deferens, ejaculatory duct, and the urethra

Figure 26.1

PeritoneumSeminalvesicle Ampulla ofductus deferensEjaculatoryduct

RectumProstateBulbourethralgland

AnusBulb of penis

Epididymis

UreterUrinary bladderProstaticurethra

Pubis

Membranousurethra

Urogenitaldiaphragm

Corpuscavernosum Corpusspongiosum

Glans penisPrepuceExternalurethral orifice

Spongy urethra

TestisScrotum

Ductus (vas)deferens

THE SCROTUM

Sac of skin and superficial fascia Hangs outside the abdominopelvic cavity Contains paired testes

3C lower than core body temperature (temperature necessary for sperm production)

Temperature is kept constant by two sets of muscles Smooth muscle that wrinkles scrotal skin (dartos

muscle) Bands of skeletal muscle that elevate the testes

(cremaster muscles)

THE TESTES

Each is surrounded by two tunics Tunica vaginalis, derived from peritoneum Tunica albuginea, the fibrous capsule

Septa divide the testis into 250–300 lobules, each containing 1–4 seminiferous tubules (site of sperm production)

Blood supply comes from the testicular arteries and testicular veins

Spermatic cord encloses nerve fibers, blood vessels, and lymphatics that supply the testes

TESTES:

Seminiferous Tubules “sperm factories” Be able to ID area of spermatogonium to

spermatids to spermatozoa Interstitial Cells (Leydig cells)

Outside seminiferous tubules Produce androgens

testosterone

NOTE: the sperm producing and hormone producing functions of testes carried out by different cells

Figure 26.3a

Head of epididymis

Body of epididymis

Tail of epididymis

Efferent ductule

Rete testis

Straight tubule

Duct of epididymis

Ductus (vas)deferens

Lobule

Testis

SeptumTunica albuginea

Tunica vaginalis

Cavity oftunica vaginalis

Spermatic cord

Seminiferoustubule

Blood vesselsand nerves

(a)

Figure 26.3c

Spermatogeniccells in tubuleepithelium

Interstitial cells

Areolarconnective tissue

SpermMyoidcells

(c)

Seminiferoustubule

Distinguish between:Spermatogonium SpermatocyteSpermatid

meiosisSpermatozoa

spermiogenesis

SPERMIOGENESIS: SPERMATIDS TO SPERM

Spermatids lose excess cytoplasm and form a tail, becoming spermatozoa (sperm)

Major regions of sperm1. Head: genetic region; nucleus and helmetlike

acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg

2. Midpiece: metabolic region; mitochondria 3. Tail: locomotor region; flagellum

Figure 26.8a, b

CentriolesSpermatidnucleus

GolgiapparatusAcrosomal

vesicleMitochondria

Approximately 24 days

Excesscytoplasm

Nucleus

Acrosome

MicrotubulesFlagellum

Tail

Midpiece Head(a)

(b)

1 2

3

4

5

6 7

Where does spermiogenosis occur?

EPIDIDYMIS Epi: outer side/ didym: testes Highly coiled duct of about 20 feet Epithelium: pseudostratified with long, nonmotile

microvilli (stereocilia) Microvilli (stereocilia) absorb testicular fluid and pass

nutrients to stored sperm Nonmotile sperm enter, pass slowly through, and

become motile (about 20 days) During ejaculation the epididymis contracts,

expelling sperm into the ductus deferensIf no ejaculation in 3-4 months, sperm are phagocytized

Po Poor Sperm Guy!

Figure 26.3a

Head of epididymis

Body of epididymis

Tail of epididymis

Efferent ductule

Rete testis

Straight tubule

Duct of epididymis

Ductus (vas)deferens

Lobule

Testis

SeptumTunica albuginea

Tunica vaginalis

Cavity oftunica vaginalis

Spermatic cord

Seminiferoustubule

Blood vesselsand nerves

(a)

DUCTUS DEFERENS AND EJACULATORY DUCT

Lucky sperm guy gang empty into

Ductus deferens Aka: vas deferens Passes through the inguinal canal Expands to form the ampulla and then joins the duct

of the seminal vesicle to form the ejaculatory duct Propels sperm from the epididymis to the urethra

Vasectomy: cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control

Figure 26.1

PeritoneumSeminalvesicle Ampulla ofductus deferensEjaculatoryduct

RectumProstateBulbourethralgland

AnusBulb of penis

Epididymis

UreterUrinary bladderProstaticurethra

Pubis

Membranousurethra

Urogenitaldiaphragm

Corpuscavernosum Corpusspongiosum

Glans penisPrepuceExternalurethral orifice

Spongy urethra

TestisScrotum

Ductus (vas)deferens

SEMINAL VESICLES

Accessory Gland Produces viscous alkaline seminal fluid

Fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins

Enhances sperm motility 70% of the volume of semen

Duct of seminal vesicle joins the ductus deferens to form the ejaculatory duct

Figure 26.1

PeritoneumSeminalvesicle Ampulla ofductus deferensEjaculatoryduct

RectumProstateBulbourethralgland

AnusBulb of penis

Epididymis

UreterUrinary bladderProstaticurethra

Pubis

Membranousurethra

Urogenitaldiaphragm

Corpuscavernosum Corpusspongiosum

Glans penisPrepuceExternalurethral orifice

Spongy urethra

TestisScrotum

Ductus (vas)deferens

Figure 26.4

Urinary bladder

Dorsal vesselsand nerves

Skin

Deep arteries(b)

(a)

Bulbourethral gland and duct

Urogenital diaphragm

Bulb of penis

Corpora cavernosa

Corpus spongiosum

Section of (b)

Spongy urethra

Glans penis

Prepuce (foreskin)

External urethral orifice

Corpora cavernosa

Urethra

Tunica albuginea of erectile bodies

Corpus spongiosum

Crus of penisBulbourethral duct openingDuctus deferens

Ampulla of ductus deferens

Prostatic urethraOrifices of prostatic ducts

Prostate

Membranous urethra

Root of penis

Shaft (body) of penis

Ejaculatory duct

Seminal vesicle

Epididymis

Testis

Ureter

URETHRA

Conveys both urine and semen (at different times)

Has three regions 1. Prostatic urethra2. Membranous urethra3. Spongy (penile) urethra

PROSTATE

Accessory Gland Encircles part of the urethra inferior to the

bladder Secretes milky, slightly acid fluid:

Contains citrate (nutrient source for sperm), enzymes, and prostate-specific antigen (PSA)

Plays a role in the activation of sperm Accounts for 1/3 of semen volume Enters the prostatic urethra during ejaculation

BULBOURETHRAL GLANDS (COWPER’S GLANDS)

Accessory Gland Pea-sized glands inferior to the prostate Prior to ejaculation, produce thick, clear

mucus Lubricates the glans penis Neutralizes traces of acidic urine in the urethra

Figure 26.4

Urinary bladder

Dorsal vesselsand nerves

Skin

Deep arteries(b)

(a)

Bulbourethral gland and duct

Urogenital diaphragm

Bulb of penis

Corpora cavernosa

Corpus spongiosum

Section of (b)

Spongy urethra

Glans penis

Prepuce (foreskin)

External urethral orifice

Corpora cavernosa

Urethra

Tunica albuginea of erectile bodies

Corpus spongiosum

Crus of penisBulbourethral duct openingDuctus deferens

Ampulla of ductus deferens

Prostatic urethraOrifices of prostatic ducts

Prostate

Membranous urethra

Root of penis

Shaft (body) of penis

Ejaculatory duct

Seminal vesicle

Epididymis

Testis

Ureter

THE PENIS

External genitalia are the scrotum and the penis Penis is the male copulatory organ Penis consists of

Root and shaft that ends in the glans penis Prepuce, or foreskin—the cuff of loose skin covering the

glans Circumcision is the surgical removal of the foreskin

Spongy urethra and three cylindrical bodies of erectile tissue (spongy network of connective tissue and smooth muscle with vascular spaces)

Erection: erectile tissue fills with blood, causing the penis to enlarge and become rigid Parasympathetic reflex promotes release of nitric oxide

(NO) NO causes erectile tissue to fill with blood Impotence: the inability to attain erection

MALE SEXUAL RESPONSE

Ejaculation Propulsion of semen from the male duct system Sympathetic spinal reflex causes

Ducts and accessory glands to contract and empty their contents

Bladder sphincter muscle to constrict, preventing the expulsion of urine

Bulbospongiosus muscles to undergo a rapid series of contractions

Propulsion of semen 11 miles/ hr

Go Sperm Man, Go!

FORMATION OF SEMEN

SEMEN

Mixture of sperm and accessory gland secretions Contains nutrients (fructose), protects and

activates sperm, and facilitates their movement (e.g., relaxin)

Prostaglandins in semen Decrease the viscosity of mucus in the cervix Stimulate reverse peristalsis in the uterus

Alkalinity neutralizes the acid in the male urethra and female vagina

Antibiotic chemicals destroy certain bacteria Clotting factors coagulate semen just after

ejaculation, then fibrinolysin liquefies it Only 2–5 ml of semen are ejaculated, containing

20–150 million sperm/ml

LECTURE QUESTION 5

Based on your knowledge of how the prostate encircles part of the urethra, what are two clinical manifestation of an enlarged prostate?

Benign Prostatic Hyperplasia (BPH) Affects nearly every elderly male Difficulty/ straining with urination Enhances risk of bladder infection (cystitis) and

kidney damage Prostatitis

Acute bacterial/ chronic bacterial Chronic prostatitis/ pelvic pain syndrome

PROSTATE HEALTH Benign Prostatic Hyperplasia

Hypertrophy of prostate affects every elderly male Distorts urethra/ urination strained/ can block urethral

opening +/or cause cystitis (bladder infection) or kidney damage

Treatment varied: can include Finasteride which reduces dihydrotestosterone, hormone involved in BPH and male pattern baldness

Prostate Cancer Second most common cause of cancer death in men/

slow growing/ stimulated by androgens 2x as common in black men Risk factors: fatty diet/ heredity Screening: digital exam and PSA levels

Normal PSA: 2.5 ng/mL PSA is a tumor marker and will rise in BPH and Prostate CA

INFERTILITY

Gradual decline of male fertility in past 50 years

Xenobiotics Environmental toxin, often novel compounds Examples: PVCs, phthalates, pesticides Many are hormone mimics, specifically estrogen

like Risky behavior

Some antibiotics, marijuana use, exposure to radiation, excessive alcohol use, oxidative stress

Sperm counts Average: 20-150 million/ mL Low fertility count: ‹1 million/ mL

Figure 26.9

Anteriorpituitary

Inhibin

GnRH

Testosterone

Via portalblood

Interstitialcells

SustentacularcellSpermatogeniccells

Seminiferoustubule

Somatic andpsychologicaleffects atother bodysites

LHFSH

1

2

2

3 4

5

6

78

Stimulates

Inhibits

ABP: AndrogenBinding Protein…keeps concentration of testosterone high around spermatogenic cells

MALE SECONDARY SEX CHARACTERISTICS Features induced in the nonreproductive

organs by male sex hormones (mainly testosterone) Appearance of pubic, axillary, and facial hair Enhanced growth of the chest and deepening of

the voice Skin thickens and becomes oily Bones grow and increase in density Skeletal muscles increase in size and mass