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Te function of the reproductive system is to produce oﬀspring.
Te gonads produce gametes (sperm or ova) and sex hormones.
All other reproductive organs are accessory organs.
Anatomy of the Male Reproductive System
Te scrotum contains the testes. It provides a temperature slightly
lower than that of body temperature, as required to produce
Each testis is covered externally by a tunica albuginea that
extends internally to divide the testis into many lobules. Each
lobule contains sperm-producing seminiferous tubules and
interstitial endocrine cells that produce androgens.
The Male Perineum and the Penis
Te male perineum which suspends the scrotum and penis, is the
region encompassed by the pubic symphysis, ischial tuberosities,
Te penis is largely erectile tissue (corpus spongiosum and
corpora cavernosa). Engorgement of the erectile tissue with blood
causes the penis to become rigid, an event called erection.
The Male Duct System
Te epididymis hugs the external surface of the testis and serves
as a site for sperm maturation and storage.
Te ductus (vas) deferens, extending from the epididymis to the
ejaculatory duct, propels sperm into the urethra by peristalsis
during ejaculation. Its terminus fuses with the duct of the seminal
gland, forming the ejaculatory duct, which empties into the
urethra within the prostate.
Te urethra extends from the urinary bladder to the tip of the
penis. It conducts semen and urine to the body exterior.
The Male Accessory Glands
Te accessory glands produce the bulk of the semen, which
contains fructose from the seminal glands, an activating ﬂuid
from the prostate, and mucus from the bulbo-urethral glands.
Semen is an alkaline ﬂuid that dilutes and transports sperm.
Important chemicals in semen are nutrients, prostaglandins, and
Physiology of the Male Reproductive System
Male Sexual Response
Parasympathetic reﬂexes control erection.
Ejaculation is expulsion of semen from the male duct system,
promoted by the sympathetic nervous system. Ejaculation is part
of male orgasm, which also includes pleasurable sensations and
increased pulse and blood pressure.
Spermatogenesis, the production of male gametes in the
seminiferous tubules, begins at puberty.
Meiosis, the basis of gamete production, consists of two
consecutive nuclear divisions without DNA replication in
between. Meiosis reduces the chromosomal number by half and
introduces genetic variability. Events unique to meiosis include
synapsis and crossover of homologous chromosomes.
Spermatogonia divide by mitosis to maintain the germ cell line.
Some of their progeny become primary spermatocytes, which
undergo meiosis I to produce secondary spermatocytes. Secondary
spermatocytes undergo meiosis II, each producing two haploid (
Spermiogenesis converts spermatids to functional sperm,
stripping away superﬂuous cytoplasm and producing an
acrosome and a ﬂagellum (tail).
Sustentocytes form the blood testis barrier, nourish
spermatogenic cells, move them toward the lumen of the tubules,
and secrete ﬂuid for sperm transport.
Hormonal Regulation of Male Reproductive Function
GnRH, produced by the hypothalamus, stimulates the anterior
pituitary gland to release FSH and LH. FSH causes sustentocytes
to produce androgen-binding protein (ABP). LH stimulates
interstitial endocrine cells to release testosterone, which
binds to ABP, stimulating spermatogenesis. ±estosterone and
inhibin (produced by sustentocytes) feed back to inhibit the
hypothalamus and anterior pituitary.
Maturation of hormonal controls occurs during puberty and
takes about three years.
±estosterone stimulates maturation of the male reproductive
organs and triggers the development of the secondary sex
characteristics of the male. It exerts anabolic eﬀects on the
skeleton and skeletal muscles, stimulates spermatogenesis, and is
responsible for male sex drive.
Anatomy of the Female Reproductive System
Te female reproductive system produces gametes and sex
hormones and houses a developing infant until birth.
Te ovaries ﬂank the uterus laterally and are held in position by
the ovarian and suspensory ligaments and mesovaria.
Within each ovary are oocyte-containing follicles at diﬀerent
stages of development and possibly a corpus luteum.
The Female Duct System
Te uterine tube, supported by the mesosalpinx, extends from
near the ovary to the uterus. Its ﬁmbriae and ciliated distal end
along with peristalsis create currents that help move an ovulated
oocyte into the uterine tube.
Te uterus has fundus, body, and cervical regions. It is supported
by the broad, cardinal, uterosacral, and round ligaments.