BIOL 2304
The Reproductive System
Reproductive Organs
Primary sex organs (gonads): testes in males; ovaries in females
Gonads produce sex cells called gametes and secrete sex hormones
Secondary sex organs:
Accessory reproductive organs – ducts, glands, and external genitalia
Male Reproductive System
The male gonads (testes) produce sperm and lie within the scrotum
Sperm are delivered to the exterior through a system of ducts:
epididymis, ductus deferens (vas deferens), ejaculatory duct, and the spongy urethra
Accessory sex glands:
Empty their secretions into the ducts during ejaculation
Include the seminal vesicles, prostate gland, and bulbourethral glands
The Testes
Seminiferous tubules produce the sperm
Interstitial (Leydig) cells – hormone-releasing cells surrounding the seminiferous tubules
Epididymis – the narrow, tightly-coiled tube that connects the seminiferous tubules to the vas deferens and
functions to mature and store sperm cells (at least 20 days)
Spermatic cord – encloses nerve fibers, blood vessels, and lymphatics that supply the testes
The Scrotum
Contains paired testicles that hangs outside the abdominopelvic cavity
External positioning keeps testes 3C lower than core body temperature, needed for sperm production
Intrascrotal temperature kept constant by two different muscles:
Dartos muscle – smooth muscle that wrinkles scrotal skin
Cremaster muscle – bands of skeletal muscle that elevate the testes
The Penis
Urethra – conveys both urine and semen (at different times)
Three cylindrical bodies of erectile tissue in shaft of penis:
One corpus spongiosum and two corpora cavernosa:
Expansion of the corpora cavernosa compresses drainage veins and retards blood outflow and
maintains engorgement
The corpus spongiosum functions in keeping the urethra open during ejaculation
Glans penis – the expanded tip of the penis that surrounds the urethral opening; continuous with the corpus
Prepuce (aka “foreskin”) – a lose fold of skin that surrounds the glans penis; secretes a waxy material called
Accessory Glands: Seminal Vesicles
Seminal Vesicles – secrete a viscous alkaline fluid that accounts for 60% of the volume of semen and which
contains nutrients and enzymes
Seminal vesicles join the ductus deferens to form the ejaculatory duct where sperm and seminal fluid
Accessory Glands: Prostate Gland
Prostate gland – the gland that encircles part of the urethra inferior to the bladder
Produces a milky, slightly acid fluid that accounts for one-third of the semen volume and which contains
nutrients, enzymes, and antibiotics
Accessory Glands: Bulbourethral Glands (Cowper’s Glands)
Bulbourethral Glands – pea-sized glands inferior to the prostate
Produce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra
Sperm Conveyance
From seminiferous tubules, the sperm enter the epididymis
Upon ejaculation the epididymis contracts, expelling sperm into the ductus deferens
Ductus deferens merges with the duct of the seminal vesicle to form the ejaculatory duct
From ejaculatory duct, sperm enter urethra
Female Reproductive System
Ovaries are the primary female reproductive organs
Make female gametes (ova)
Secrete female sex hormones (estrogen and progesterone)
Internal genitalia – ovaries, uterine tubes, uterus, vagina
External genitalia – vulva, clitoris, labia, and hymen
Embedded in the ovary cortex are
ovarian follicles
Each follicle consists of an immature
egg called an oocyte
Primordial follicle – one layer of squamous-like follicle cells surrounds the oocyte
Primary follicle – two or more layers of cuboidal granulosa cells enclose the oocyte
Secondary follicle
Tertiary follicle (aka vesicular or Graafian follicle) – at its most mature stage, cell bulges from the surface of the
Ovulation – the ejection of the oocyte from a mature vesicular follicle
Corpus luteum – a ruptured follicle after ovulation
Zona pellucida – the thick transparent membrane surrounding the ovum before implantation
Corona radiata – the layer of cells immediately surrounding the ovum
Ovaries and Oocytes
Uterine Tubes (Fallopian Tubes)
Uterine tubes – receive the ovulated oocyte and provide a site for fertilization; have direct physical contact with
the ovaries
Fimbriae of the uterine tube – beating cilia at end of uterine tubes that create currents to draw the oocyte into
the uterine tube
Infundibulum of the uterine tube – the portion between the ampulla and fimbriae
Ampulla of the uterine tube – the dilated portion of uterine tube which curves over the ovary
Uterus – a hollow, thick-walled organ that receives, retains, and nourishes the fertilized egg
Body of the uterus – the main, central portion of the uterus
Fundus of the uterus – the rounded region superior to the entrance of the uterine tubes
Cervix of the uterus – the narrow outlet that protrudes into the vagina
Cervical canal – the canal extending from the uterus to the vagina
Internal os – the opening at the top of the cervical canal
External os – the opening at the bottom of the cervical canal
Uterine Wall
Composed of three layers:
Perimetrium – outermost serous
layer; the visceral peritoneum
Myometrium – middle layer;
interlacing layers of smooth
muscle, during labor this layer
contracts to expel fetus
Endometrium – mucosal lining of
the uterine cavity
The inner layer of the
Allows for implantation of
a fertilized egg
Sloughs off if no pregnancy
occurs (menses)
Thin-walled tube lying between the bladder and the rectum, extending from the cervix to the exterior of the
Serves as the female organ of copulation; receives the penis during sexual intercourse
Provides a passageway for birth and menstrual flow
Mons pubis – mound of fatty tissue overlying the pubic symphysis (pubic bone)
Labia majora – outer folds of skin contains fat, sudoriferous and sebaceous glands, covered with pubic hair
(homologous to scrotum)
Labia minora – inner folds of skin containing sebaceous glands and nerve endings that provide stimulation
Clitoris – cylindrical mass of erectile tissue covered by a layer of skin called the prepuce (homologous to penis)
Vestibule – cleft between the labia minora; includes the urethral orifice, vaginal orifice, and vestibular glands
that produce lubricants during sexual intercourse
Urethra – muscular tube, opening is anterior to opening of vagina, carries urine from bladder to exterior
Mammary Glands
Modified sweat glands consisting of 15-25 lobes that radiate around and open at the nipple
Lobes contain glandular alveoli that produce milk in lactating women