Reproductive System

•     Gonads (Primary sex organs) – testes in males, ovaries in females

–   Gonads produce sex cells called gametes and secrete sex hormones

•   Spermatozoa

•   Oocyte à ovum

•   Sex hormones – androgens (males), and estrogens and progesterone (females)

•     Ducts

–   Reproductive tract

•     Accessory glands

•     External genitalia

Mitosis vs. Meiosis

•    Produces diploid cells

Male Reproductive System

•     Scrotum

–    Contains paired testicles separated by a midline septum

–    Its external positioning keeps the testes 3°C lower than core body temperature (needed for sperm production)

–    Intrascrotal temperature is kept constant by two sets of muscles:

•   Dartos – smooth muscle that wrinkles scrotal skin

•   Cremaster – bands of skeletal muscle that elevate the testes

•     Testes

•     Epididymis

•     Ductus/vas deferens

•     Seminal vesicle

•     Prostate gland

•     Ejaculatory duct

•     Bulbourethral gland

•     Urethra

Male Reproductive System

•    Spermatic cords

–  Inguinal canal

•  Inguinal hernia

–  Deferential/testicular artery

–  Testicular vein

Male Reproductive System

•    Descent of the testes

–  Gubernaculum testis

Testes

•    Raphe

–  Scrotal cavities

•    Each testis is surrounded by two tunics:

–  Tunica vaginalis

–  Tunica albuginea

•  Septum

•  Septa divide the testis into 250-300 lobules, each containing 1-4 seminiferous tubules

•  Seminiferous tubules produce the sperm

Male Reproductive System

•     Seminiferous tubules

–    Spermatogenesis

•   The sequence of events that produces sperm in the seminiferous tubules of the testes

–    Spermatogenic cells

•   Primordial germ cells

•   Spermatogonia

–    Sertoli (sustentacular) cells

•   Their tight junctions form a blood-testis barrier

–   This prevents sperm antigens from escaping through the basal lamina into the blood

•   Mullerian-inhibiting factor

–    Leydig (interstitial) cells

•   Androgens

SPERMATOGENESIS

•    Mitosis

•    Meiosis

•    Spermiogenesis

–  Sperm cells

–  Spermiation

SPERMATOGENESIS

•     Spermatogonia

–   Mitosis

•     Primary spermatocytes

–   Meiosis

•     Secondary spermatocytes

•     Spermatids

•     Spermiogenesis

–   Spermatids form sperm

SPERMATOGENESIS

•     Sperm have three major regions

–   Head

•   Contains DNA and has a helmetlike acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg

–   Middle piece

•   Contains mitochondria

–   Tail (flagellum)

Male Reproductive System

•     The hypothalamus releases gonadotropin-releasing hormone (GnRH)

•     GnRH stimulates the anterior pituitary to secrete FSH and LH

–    FSH causes sustentacular cells to release androgen-binding protein (ABP)

•   ABP binding of testosterone enhances spermatogenesis

•   Inhibin

–    LH stimulates interstitial cells to release testosterone

–   DHT (dihydrotestosterone)

»   Testosterone is synthesized from cholesterol

»   It must be transformed to exert its effects on some target cells

TUBULES

•    Straight tubulus rectus conveys sperm to the rete testis

•    From the rete testis, the sperm:

–  Leave the testis via efferent ductules

–  Enter the epididymis

TUBULES

•    Epididymis

–  Nonmotile sperm enter, pass through its tubes and become motile

–  Upon ejaculation the epididymis contracts, expelling sperm into the ductus deferens

–  Ductus epididymis

–  Head, body, & tail

TUBULES

•     Ductus deferens

–    Runs from the epididymis through the inguinal canal into the pelvic cavity

–    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

•     Ejaculatory duct

•     Urethra

–    Conveys both urine and semen

–    Consists of three regions

•   Prostatic

•   Membranous

•   Spongy (penile)

–    External urethral orifice

Accessory Glands

•     Seminal vesicles

–    Secrete 60% of the volume of semen

•     Prostate gland

–    Milky, slightly acid fluid

•     Bulbourethral glands

–    Produce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra

•     Semen

–    Viscous alkaline fluid containing fructose and prostaglandins

–    Prostaglandins facilitate the movement of sperm through the female reproductive tract

PENIS

•     An organ designed to deliver sperm into the female reproductive tract

•     Root

•     Body

–    Tunica albuginea

–    Corpus cavernosum

–    Corpus spongiosum

•     Glans penis

•     Prepuce (foreskin)

–    Circumcision – surgical removal of the foreskin after birth

Female Reproductive System

•    Ovaries

–  Primary female reproductive organs

•  Make female gametes (ova)

•  Secrete female sex hormones (estrogen and progesterone)

•    Uterine tubes

•    Uterus

•    Vagina

•    Mammary glands

OVARIES

•     Paired organs on each side of the uterus held in place by several ligaments

–   Broad ligament

•   Contains the suspensory ligament and the mesovarium

–   Ovarian ligament

–   Suspensory ligament

•   Ovarian vessels

•     Hilus

OVARIES

•    They are surrounded by a fibrous tunica albuginea, which is covered by a layer of simple epithelial cells called the germinal epithelium

•    Ovarian cortex

–  Embedded in the ovary cortex are ovarian follicles

–  Each follicle consists of an immature egg called an oocyte

•    Ovarian medulla

OOGENESIS

•     Production of female sex cells by meiosis

•     Primordial germ cells

•     Oogonia

–    Atresia

•     Primary oocytes

–    Primordial follicles

•   One layer of squamouslike follicle cells surrounds the oocyte

•   Primordial follicles appear as oogonia are transformed into primary oocytes

–    Primary follicles

•   Two or more layers of cuboidal granulosa cells enclose the oocyte

•   Zona pellucida

•   Corona radiata

OOGENESIS

•      Secondary follicles

–    Has a fluid-filled space between granulosa cells that form a central antrum

–    Follicular fluid

•      Polar bodies

•      Secondary oocyte

–    Graafian follicle

•    Secondary follicle at its most mature stage that bulges from the surface of the ovary

•    The secondary oocyte arrests in metaphase II and is ovulated

•      If penetrated by sperm the second oocyte completes meiosis II, yielding:

–    One large ovum (the functional gamete)

–    A tiny second polar body

•      Zygote

Uterine Tubes

•     Receive the ovulated oocyte and provide a site for fertilization

•     Funnel-shaped, ciliated infundibulum containing fingerlike projections called fimbriae

•     Beating cilia on the fimbriae create currents to carry the oocyte into the uterine tube

•     The oocyte is carried toward the uterus by peristalsis and ciliary action

UTERUS

•     Fundus

–    Rounded region superior to the entrance of the uterine tubes

•     Body

–    Major portion of the uterus

–    Uterine cavity

–    Isthmus

•   Narrowed region between the body and cervix

•     Cervix

–    Narrow neck which projects into the vagina inferiorly

–    Cervical canal

•   Cavity of the cervix that communicates with:

–   The vagina via the external os

–   The uterine body via the internal os

–    Cervical mucus

•   Secrete mucus that covers the external os and blocks sperm entry except during midcycle

UTERUS

•    Composed of three layers

–  Perimetrium

•  Outermost serous layer; the visceral peritoneum

–  Myometrium

•  Middle layer; interlacing layers of smooth muscle

–  Endometrium

•  Mucosal lining of the uterine cavity

–  Stratum functionalis

–  Stratum basalis

Endometrium

•     Has numerous uterine glands that change in length as the endometrial thickness changes

•     Stratum functionalis:

–  Undergoes cyclic changes in response to ovarian hormones

–  Is shed during menstruation

•     Stratum basalis:

–  Forms a new functionalis after menstruation ends

–  Does not respond to ovarian hormones

UTERUS VASCULAR SUPPLY

•     Uterine arteries

•     Arcuate arteries

–    Branches of the uterine arteries in the myometrium that give rise to radial branches

•     Radial branches

–    Descend into the endometrium and give off:

•   Spiral arteries to the stratum functionalis

–   Degeneration and regeneration of spiral arteries causes the functionalis to shed during menstruation

•   Straight arteries to the stratum basalis

VAGINA

•     Thin-walled tube lying between the bladder and the rectum, extending from the cervix to the exterior of the body

•     Provides a passageway for birth and menstrual flow

•     Mucosa

–   Rugae

•     Muscularis

•     Vulva

–   Labia

–   Clitoris

–   Vestibule

–   Vaginal orifice

–   Paraurethral & vestibular glands

Mammary Glands

•     Modified sweat glands consisting of 15-25 lobes that radiate around and open at the nipple

•     Lactation

•     Lobes

–    Contain glandular alveoli that produce milk in lactating women

–    Alveolar glands pass milk to lactiferous ducts, which open to the outside

–    Lobules

–    Lactiferous sinus

Female Reproductive Cycle

•     Ovarian cycle

–    Monthly series of events associated with the maturation of an egg

–    Follicular phase – period of follicle growth (days 1–14)

–    Luteal phase – period of corpus luteum activity (days 14–28)

–    Ovulation occurs midcycle

•     Uterine (menstrual) cycle

–    Series of cyclic changes that the uterine endometrium goes through each month in response to ovarian hormones in the blood

–    Days 1-5:  Menstrual phase – uterus sheds all but the deepest part of the endometrium

–    Days 6-14:  Proliferative (preovulatory) phase – endometrium rebuilds itself

–    Days 15-28:  Secretory (postovulatory) phase – endometrium prepares for implantation of the embryo

Hormonal Control

•     GnRH

–   FSH

–   LH

•     Estrogens

•     Progesterone

•     Relaxin

•     Inhibin

Ovulation

•    Ejection of the oocyte from the ripening follicle

•    Ovulation occurs when the ovary wall ruptures and expels the secondary oocyte

Female Reproductive Cycle

•    Menstrual phase

–  Menstruation/menses

•  If fertilization does not occur, progesterone levels fall, depriving the endometrium of hormonal support

•  Spiral arteries kink and go into spasms and endometrial cells begin to die

•  The functional layer begins to digest itself

•  Spiral arteries constrict one final time then suddenly relax and open wide

•  The rush of blood fragments weakened capillary beds and the functional layer sloughs

Female Reproductive Cycle

•    Postovulatory phase

•    Ovaries

–  Corpus hemorrhagicum

–  Corpus luteum

•  Ruptured follicle after ovulation

•  If pregnancy does not occur, the corpus luteum degenerates in 10 days, leaving a scar (corpus albicans)

•  If pregnancy does occur, the corpus luteum produces hormones until the placenta takes over that role (at about 3 months)

–  hCG