Chapter 16The Reproductive System

Intro & Male

Notice: This presentation contains actual pictures of human reproductive anatomy

The Reproductive SystemThe Reproductive System1. Gonads – primary sex

organs

Testes in males

Ovaries in females

2. Gonads produce gametes (sex cells) and secrete hormones

Sperm – male

Ova (eggs) – female

Male Reproductive SystemMale Reproductive System Testes

Duct system

- Epididymis

- Ductus deferens

- Urethra

Accessory organs

- Seminal vesicle

- Prostate gland

- Bulbourethral gland

External genitalia

- Penis

- Scrotum

TestesTestes

Tunica albuginea – capsule that surrounds each testis

Septa – extensions into testis; dividing it into lobules

TestesTestesEach lobule contains 1-4

seminiferous tubules Tightly coiled

Sperm-forming factories

Empty sperm into the rete testis

Sperm travels through the rete testis to epididymis

Interstitial cells produce androgens such as testosterone

EpididymisEpididymis

Comma-shaped, tightly coiled tube

Superior and along posterior lateral side

Matures and stores sperm cells (at least 20 days)

Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens

Ductus DeferensDuctus Deferens Carries sperm

from epididymis to ejaculatory duct

Passes through inguinal canal & over bladder

Moves by peristalsis

Spermatic cord – ductus deferens, blood vessels, and nerves in a connective tissue

Ends in the ejaculatory duct which unites with urethra

Vasectomy – cutting of the ductus deferens at the level of the testes to prevent transportation of sperm

UrethraUrethra Extends from the base of

bladder to the tip of penis

Carries both urine and sperm

Sperm enters from the ejaculatory duct

Regions:

Prostatic urethra –surrounded by prostate

Membranous urethra – from prostatic urethra to penis

Spongy (penile) urethra – runs the length of the penis

Seminal VesiclesSeminal Vesicles

Located at the base of the bladder

Produces a thick, yellowish secretion (60% of semen)

- Fructose (sugar)

- Vitamin C

- Prostaglandins

- Substances that nourish & activate sperm

Prostate GlandProstate Gland

Encircles upper part of urethra

Secretes a milky fluid

- Helps activate sperm

- Enters urethra through several small ducts

Bulbourethral GlandsBulbourethral Glands Pea-sized gland inferior

to prostate

Produces a thick, clear mucus

- Cleanses urethra of acidic urine

- Lubricant during intercourse

- Secreted into penile urethra

SemenSemen

Mixture of sperm & gland secretions

Advantages of secretions

- Fructose provides energy

- Alkalinity neutralizes acidic vagina

- Semen inhibits bacterial growth

- Elements of semen enhance sperm motility

External GenitaliaExternal Genitalia

Scrotum

- Divided sac of skin outside abdomen

- 3°C lower than body temp to protect sperm

External GenitaliaExternal Genitalia

Penis- Delivers sperm into female repro tract

- Shaft

- Glans penis (enlarged tip)

- Prepuce (foreskin) Folded cuff of

skin around proximal end

Often removed by circumcision

External GenitaliaExternal Genitalia

3 areas of spongy erectile tissue around the urethra

SpermatogenesisSpermatogenesis

Production of sperm cells

Begins at puberty and continues throughout life

Occurs in the seminiferous tubules

Processes of SpermatogenesisProcesses of Spermatogenesis

Follicle stimulating hormone (FSH) regulates

Spermatogonia (stem cells) - rapid mitosis to produce more stem cells before puberty

First division of a stem cell becomes 1 stem cell & 1 primary spermatocyte

Primary spermatocytes undergo meiosis

Haploid spermatids

Anatomy of a Mature Sperm CellAnatomy of a Mature Sperm Cell

Only human flagellated cell

Late spermatids - distinct regions

- Head –DNA covered by acrosome

- Midpiece

- Tail

Sperm cells = mature spermatids

Spermatogenesis takes 64 to 72 days

Testosterone ProductionTestosterone Production- Most important hormone of testes

- Produced in interstitial cells

- Functions

Organ development

Sex drive

Secondary sex characteristics

- Deepening of voice

- Increased hair growth

- Larger skeletal muscles

- Thicker bones

Regulation Regulation of Male of Male Androgens Androgens (Sex (Sex Hormones)Hormones)