The Reproductive Systems Chapter 28 The Reproductive Systems

Reproduction Overview Sexual Reproduction is the process in which organisms produce offspring by means of uniting gametes (sperm and egg) Male reproductive organs secrete androgen hormones, produce gametes (sperm), and facilitate fertilization Female reproductive organs secrete female hormones, produce gametes (ova), facilitate fertilization and sustain growth of the embryo and fetus

Reproduction Overview Urology is the medical specialty that treats disorders and diseases of the male reproductive system Gynecology is the medical specialty that treats disorders and diseases of the female reproductive system Obstetrics focuses on the care of women during pregnancy

Male Reproductive Anatomy The genitals are all the structures of reproduction The gonads (the testes in males and ovaries in females) are the site for gamete production and hormone secretion Various ducts store and transport gametes Accessory sex glands produce secretions to protect and support the gametes Supporting structures deliver and/or assist in joining gametes (penis in male, vagina and uterus in female)

Male Reproductive Anatomy The male gonads are the testes (singular: testis) The ducts of the male reproductive system are the: vas deferens (ductus deferens) ejaculatory ducts urethra Male reproductive glands are the: seminal vesicles (2) Prostate (1) bulbourethral glands (2)

Male Reproductive Anatomy The scrotum is a supporting structure for the testes It consists of a sac of loose skin and superficial fascia that hangs from the root of the penis The location and contraction of muscle fibers (dartos and cremaster muscles) regulates the testicular temp to that required for sperm production (2-3o below the core temp)

Male Reproductive Anatomy The spermatic cord is a supportive structure that ascends “out of” the scrotum, and consists of: The vas deferens The testicular artery (of course this is going into the scrotum) Veins and lymphatics that drain the testes and carry testosterone to the body Autonomic nerves

Male Reproductive Anatomy The spermatic cord and ilioinguinal nerve pass through the inguinal canal, a passageway in the aponeuroses of the abdominal muscles (transversus abdominus, internal oblique, and external oblique muscles) In women, the round ligament of the uterus and the ilioinguinal nerve pass through a very small inguinal canal

Male Reproductive Anatomy The tunica albuginea (collagen) forms septa that divide each testis into compartments called lobules Each lobule contains 1-3 seminiferous tubules where sperm are produced

Male Reproductive Physiology Prenatal secretion of testosterone assists testicular descent and development of male external genital Secretion of testosterone at puberty leads to development of male secondary sexual characteristics stimulation of anabolism (musculoskeletal and protein growth) hair growth patterns lowering of the voice development of libido (sexual drive)

Spermatogenesis Spermatozoa are produced in the seminiferous tubules by sperm stem cells called spermatogonia At the beginning of puberty, the anterior pituitary increases secretion of the gonadotrophs LH and FSH Follicle-stimulating hormone (FSH) stimulates Sertoli cells and increases the rate of spermatogenesis FSH in males In sexually-mature males, FSH acts on spermatogonia stimulating (with the aid of testosterone) the production of sperm. LH in males LH acts on the interstitial cells (also known as Leydig cells) of the testes stimulating them to synthesize and secrete the male sex hormone, testosterone. LH in males is also known as interstitial cell stimulating hormone (ICSH).

Spermatogenesis LH stimulates Leydig cells, which are located between seminiferous tubules, to secrete the hormone testosterone (synthesized from cholesterol) Once the degree of spermatogenesis (sperm formation) required for male reproductive functions has been achieved, Sertoli cells release inhibin, a hormone that inhibits FSH

Spermatogenesis Spermatogonium to primary spermatocytes is mitosis. Meiosis takes a 2n primary spermatocyte to a 1n spermatid

Spermatozoa Each day about 300 million sperm complete the process of spermatogenesis. A sperm contains several structures that are highly adapted for reaching and penetrating a secondary oocyte The major parts of a sperm are the head and the tail the nucleus contains 23 highly condensed chromosomes (half the normal number) covering the anterior two-thirds of the nucleus is the acrosome

Spermatozoa The acrosome is a cap-like vesicle filled with enzymes (hyaluronidase and proteases) that help a sperm to penetrate a secondary oocyte to bring about fertilization The middle piece contains many mitochondria which provide the energy (ATP) for locomotion

Spermatozoa Before ejaculation, sperm travel via the following route: Seminiferous tubules Rete testis (network) Efferent ducts Ductus epididymis Vas (ductus) deferens…