Module 1M: The Pubescent Period

General functions of the human reproductive system

Gametogenesis, fertilization, growth and nourishment of a new individual, and production of reproductive hormones.

Gametogenesis

Production and development of gametes (sperm and ova).

Oogenesis

Formation of female gametes (ova).

Spermatogenesis

Formation of male gametes (sperm).

Fertilization

Union of sperm and oocyte to form a zygote.

Primary male gonad

Testes.

Primary female gonad

Ovaries.

Penis

Male copulatory organ that delivers sperm and carries urine and semen.

Glans penis

Enlarged tip of the penis.

Prepuce (foreskin)

Fold of skin covering the glans penis.

Scrotum

Skin pouch that encloses and protects the testes.

Optimal temperature for spermatogenesis

About 3°C below body temperature.

Dartos muscle

Contracts the scrotal skin in cold conditions.

Cremaster muscle

Pulls the testes closer to the body in cold conditions.

Testes

Produce sperm and testosterone.

Tunica albuginea

Fibrous connective tissue covering the testes.

Seminiferous tubules

Tightly coiled sperm-forming structures in the testes.

Germ cells

Cells that develop into spermatozoa.

Sertoli (sustentacular) cells

Nourish developing sperm cells.

Leydig (interstitial) cells

Secrete testosterone.

Testosterone

Primary male sex hormone.

Rete testis

Network that receives sperm from seminiferous tubules.

Ductuli efferentes

Transport sperm from the rete testis to the epididymis.

Epididymis

Site of sperm maturation and temporary sperm storage.

Time for sperm maturation in epididymis

About 20 days.

Vas deferens (ductus deferens)

Transports sperm from the epididymis to the ejaculatory duct.

Spermatic cord

Connective tissue sheath containing the vas deferens, nerves, and blood vessels.

Ampulla of vas deferens

Expanded portion that empties into the ejaculatory duct.

Ejaculatory duct

Receives sperm and gland secretions before entering the urethra.

Urethra

Carries urine and semen (not at the same time).

Prostatic urethra

Portion of urethra within the prostate gland.

Membranous urethra

Shortest part of the male urethra.

Penile (spongy) urethra

Portion of the urethra within the penis.

Accessory glands

Seminal vesicles, prostate gland, and bulbourethral glands.

Seminal vesicles

Produce thick alkaline fluid rich in fructose and prostaglandins.

Prostate gland

Produces thin milky alkaline fluid that enhances sperm motility.

Bulbourethral (Cowper’s) glands

Produce alkaline mucus that lubricates the urethra and neutralizes acidic urine residue.

Semen

Mixture of sperm and accessory gland secretions.

Normal sperm count

50-150 million sperm per mL of semen.

Normal semen volume

2-5 mL.

Normal semen pH

7.2-7.6 (alkaline).

Main purposes of semen

Transport sperm, nourish/protect sperm, and dilute sperm concentration.

GnRH (male)

Produced by the hypothalamus; stimulates LH and FSH release.

LH (male)

Stimulates Leydig cells to produce testosterone.

ICSH

Another name for LH in males.

FSH (male)

Stimulates Sertoli cells and supports spermatogenesis.

Inhibin

Inhibits FSH release to regulate sperm production.

Relaxin (male)

Produced by the prostate; increases sperm motility.

Spermatogonia

Primitive sperm-forming cells.

Type A spermatogonia

Remain as stem cells.

Type B spermatogonia

Develop into primary spermatocytes.

Primary spermatocyte

Cell that undergoes meiosis I.

Secondary spermatocyte

Product of meiosis I.

Spermatid

Product of meiosis II; immature sperm cell.

Spermiogenesis

Final maturation of spermatids into spermatozoa.

Spermatozoa

Mature sperm cells.

Acrosome

Cap-like structure containing enzymes for fertilization.

Capacitation

Process in the female reproductive tract that enables sperm to fertilize an oocyte.

Vulva

External female genitalia.

Mons pubis

Fatty tissue covering the pubic bone.

Labia majora

Hair-covered outer folds that protect the vulva.

Labia minora

Inner folds protecting the urethral and vaginal openings.

Vestibular glands

Secrete lubricating fluid into the vaginal vestibule.

Clitoris

Primary organ of sexual arousal.

Perineum

Diamond-shaped area between the vulva and anus.

Ovaries

Produce ova, estrogen, and progesterone.

Ovarian follicles

Sac-like structures containing immature oocytes.

Graafian follicle

Mature fluid-filled ovarian follicle.

Ovulation

Release of a mature secondary oocyte from the ovary.

Corpus luteum

Ruptured follicle that secretes progesterone.

Corpus albicans

Degenerated corpus luteum.

Fimbriae

Finger-like projections that guide the ovulated oocyte into the uterine tube.

Infundibulum

Funnel-shaped opening of the uterine tube.

Ampulla of the uterine tube

Most common site of fertilization.

Isthmus of the uterine tube

Narrow medial portion of the tube.

Travel time of zygote to uterus

About 3-4 days.

Uterus

Hollow muscular organ that receives and nourishes the embryo.

Fundus

Upper rounded portion of the uterus.

Body of uterus

Main central portion of the uterus.

Cervix

Lower narrow portion of the uterus opening into the vagina.

Perimetrium

Outermost serosal layer of the uterus.

Myometrium

Muscular layer responsible for uterine contractions.

Endometrium

Innermost uterine lining where implantation occurs.

Implantation

Embedding of the embryo into the endometrium.

Vagina

Muscular canal that receives the penis and serves as the birth canal.

Birth canal

Another name for the vagina.

Hymen

Thin vascular membrane partially covering the vaginal opening.

Lactiferous ducts

Carry milk from mammary glands to the nipple.

Ampulla of lactiferous duct

Milk reservoir behind the nipple.

Prolactin

Hormone responsible for milk production.

Oxytocin

Hormone responsible for milk ejection and uterine contractions.

GnRH (female)

Stimulates FSH and LH release from the anterior pituitary.

FSH (female)

Stimulates follicle development and estrogen secretion.

LH (female)

Triggers ovulation and corpus luteum formation.

Estrogen

Promotes female secondary sex characteristics and endometrial proliferation.

Progesterone

Maintains the endometrium for implantation.

hCG (human chorionic gonadotropin)

Maintains the corpus luteum during early pregnancy.

Source of hCG

Placenta.

Oogenesis

Begins during fetal development.

Number of oogonia by 4th fetal month

About 5 million.