male reproductive system

Testes (primary sex organ of male)

(within scrotum) produce sperm

• Sperm delivered to exterior through

system of ducts

pathway of sperm flow

Epididymis, ductus deferens, ejaculatory

duct, and urethra

Accessory sex glands

Seminal vesicles

– Prostate

– Bulbourethral glands

The Scrotum

Sac of skin and superficial fascia

– Hangs outside abdominopelvic cavit

scrotum function

contains paired testes

• 3C lower than core body temperature

• Lower temperature necessary for sperm

production

how does scrotum keep an optimal temperature

two sets of muscles

Dartos muscle

smooth muscle; wrinkles

scrotal skin; pulls scrotum close to body

Cremaster muscles -

bands of skeletal

muscle that elevate testes

Tunica vaginalis

outer layer of testes derived from

peritoneum

Tunica albuginea

inner layer of testes r; fibrous

capsule

What do the septa of the testis do?

They divide the testis into about 250 lobules.

How many seminiferous tubules are in each testicular lobule?

About 1–4 seminiferous tubules per lobule.

What is the function of the seminiferous tubules?

They are the site of sperm production (spermatogenesis).

Where does sperm production occur in the testes?

In the seminiferous tubules within each lobule.

Seminiferous Tubule composition

Thick, stratified epithelium surrounding central

fluid-containing lumen

Myoid cells of seminiferous tubule

surround each tubule

– May squeeze sperm, testicular fluids out of testes

Tubules of each lobule form

straight tubules

Sperm conveyed from

Seminiferous tubules, Straight tubule, Rete testis, Efferent ductules, and Epididymis

Interstitial endocrine cells

in soft tissue surrounding seminiferous tubules

• Produce androgens, e.g., testosterone

– Secrete it into interstitial fluid

Blood supply of testes

Testicular arteries arise from abdominal aorta

Spermatic cord

encloses nerve fibers, blood vessels, and lymphatics that supply testes

The Male Perineum

• Diamond-shaped region between pubic symphysis, coccyx, and ischial tuberosities, suspends scrotum; contains root of penis

and anus

External genitalia

scrotum and penis

Penis

male copulatory organ

• Penis consists of

• Root and shaft that ends in glans penis

• Prepuce, or foreskin—cuff of loose skin covering glans

Circumcision

• Surgical removal of foreskin and

  • 60% reduction in HIV risk

  • Reduced risk for other reproductive system infection

What is the spongy urethra surrounded by?

The corpus spongiosum.

What are the three cylindrical bodies of erectile tissue in the penis?

One corpus spongiosum and two corpora cavernosa.

What is the corpus spongiosum?

A column of erectile tissue that surrounds the urethra and expands to form the glans and bulb of the penis.

What are the corpora cavernosa?

Paired dorsal erectile bodies responsible for rigidity during erection.

What is erectile tissue made of?

Spongy connective tissue and smooth muscle containing vascular spaces.

What causes an erection?

Erectile tissue fills with blood, causing the penis to enlarge and become rigid

The Male Duct System

• Epididymis

• Ductus deferens

• Ejaculatory duct

• Urethra

Epididymis Head

• contains efferent ductules; superior aspect of testis; body and tail on posterolateral area of testis 

• Duct of the epididymis 

• 6 m in length

  • Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm

What is the initial state of sperm entering the epididymis?

They are nonmotile.

What happens to sperm while passing through the epididymis?

They mature, become motile, and are stored.

How long does sperm typically take to pass through the epididymis?

about 20 days

How long can sperm be stored in the epididymis?

Several months.

What happens to the epididymis during ejaculation?

t contracts to expel sperm into the ductus (vas) deferens.

What is another name for the ductus deferens?

The vas deferens.

What is the approximate length of the ductus deferens?

about 45 cm.

What pathway does the ductus deferens take?

it passes through the inguinal canal into the pelvic cavity.

What structure does the ductus deferens expand into?

The ampulla.

What forms the ejaculatory duct?

The joining of the ductus deferens (ampulla) and the duct of the seminal vesicle.

What is the function of smooth muscle in the ductus deferens?

it propels sperm from the epididymis toward the urethra.

What is a vasectomy?

A surgical procedure that cuts and ligates the ductus deferens to prevent sperm transport.

How effective is a vasectomy as birth control?

100%

Urethra convey both

semen and urine (different times)

• Prostatic urethra

surrounds prostate

intermediate part of the urethra (membranous urethra

• in urogenital diaphragm

• Spongy urethra 

• runs through penis; opens at external urethral orifice

The Male Accessory Glands

seminal glands/vesicles, prostate gland, and paired bulbouretheral gland

seminal glands location

• On posterior bladder surface; smooth muscle contracts during ejaculation

what does the seminal gland produce

• Produces viscous alkaline seminal fluid 

  • Fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins

  • ~70% volume of semen

semen

• Milky-white mixture of sperm and accessory gland secretions

  • 2–5 ml semen ejaculated, contains 20–150 million sperm/ml

what does semen contain

• Contains fructose for energy (ATP) production; protects and activates sperm; facilitates sperm movemen

purpose for alkalinity in semen

• Alkaline  neutralizes acidity of male urethra and female vagina  enhanced motility

• Ejaculation

• Propulsion of semen from male duct system

• Sperm (spermatozoa)

• production in seminiferous tubules

• Most body cells of sperm have

• have 46 chromosomes - diploid chromosomal number (2n)

chromosomes composition

Two sets (23 pairs) of chromosomes

One maternal, one paternal – homologous chromosomes 

Gametes have

23 chromosomes - haploid chromosomal number (n)

• Only one member of homologous pair 

• Functions of meiosis

• Number of chromosomes halved (from 2n to n)

• Introduces genetic diversity

how are gametes formed?

meiosis,

• Two consecutive cell divisions (meiosis I and II); only one round of DNA replication

  • Produces four daughter cells

What causes genetic variability in gametes during meiosis I?

Random alignment (independent assortment) of homologous chromosome pairs.

What is the role of crossover in meiosis?

it exchanges genetic material between homologous chromosomes, increasing variation.

Why are no two gametes exactly alike?

Because of independent assortment and crossing over during meiosis.

How are gametes different from the original mother cell?

they are genetically different due to recombination and independent assortment.

What is the purpose of reduction division in meiosis?

It reduces the chromosome number from diploid (2n) to haploid (n).

In which stage does reduction division occur?

Meiosis I.

What happens during synapsis?

Homologous chromosomes pair up to form tetrads (four chromatids).

What is a tetrad?

A structure made of two homologous chromosomes (four chromatids total).

What is crossover?

Exchange of genetic material between homologous (maternal and paternal) chromatids.

• End of meiosis I each daughter cell

• Two copies of one member of each homologous pair (either maternal or paternal); none of the other

Meiosis II

• Equational division of meiosis

  • Sister chromatids from meiosis I separated, one per cell

• Spermatogenic cells

• give rise to sperm

  • Mitosis of spermatogonia (stem cell) forms two spermatocytes

• Meiosis sperm pathway

• Spermatocytes  secondary spermatocytes  spermatids

• Spermiogenesis

Spermatids become sperm

• Meiosis I overall production

• Primary spermatocyte (2n) → two secondary spermatocytes (n)

• Meiosis II overall production

• Each secondary spermatocyte (n) → two spermatids (n)

• Spermatid – small, nonmotile cells close to lumen of tubule

• Spermatids

• Correct chromosome number (n)

• Nonmotile

• Spermiogenesis

• Spermatids elongate; lose excess cytoplasm; form a tail  spermatozoon (sperm)

• Head of sperm

• genetic region; nucleus and helmetlike acrosome containing hydrolytic enzymes that enable sperm to penetrate egg

• Midpiece of sperm

• metabolic region; mitochondria  ATP to move tail

• Tail of sperm

• locomotor region; flagellum