Male Reproductive System Overview

Male Reproductive System

• The male reproductive system becomes active after puberty.
• Puberty causes reproductive organs to mature, creating a fertile individual.
• Primary sex organs produce sex cells (sperm) and sex hormones.
• Accessory sex organs support the sex cells and aid in fertilization.
• Scrotum: a sac outside the abdominal cavity.
• Scrotum structure: smooth and skeletal muscle and skin, divided into left and right compartments for testes.
• Scrotum function: maintains testes at 3 degrees cooler than body temperature.
• Muscles in scrotum contract/relax to adjust temperature.
• Testes: oval-shaped organs with seminiferous tubules for sperm production.
• Testes respond to follicle-stimulating hormone.
• Sperm maturation in epididymis.
• Seminiferous tubules: composed of stratified epithelium surrounding a lumen.
• Spermatogenic cells mature into sperm.
• At puberty, seminiferous tubules produce approximately 400 million sperm.
• Spermatogenic cells (different stages): Spermatogonium, Primary spermatocyte, Secondary spermatocyte, Spermatid, and Sperm.
• Spermatogenesis stages: formation of spermatocytes, meiosis, and spermiogenesis.
• Spermatogonium divides by mitosis producing two daughter cells.
• Meiosis is reduction division producing 4 spermatids from one spermatogonium.
• Spermiogenesis: spermatids mature into sperm with flagella, mitochondria, nucleus (DNA), with a special structure at the head called the acrosome.
• Support cells in testicles help sperm mature and leave the scrotum.
• Muscle contractions help sperm exit the testes.
• Epidydimis: organ arching over posterior side of testicles, about 6 meters long when uncoiled.
• Epididymus function: Complete maturation and ability for sperm to swim and fertilize during 20 days.
• Ejaculation: smooth muscle causing mature sperm to move to the ductus deferens.
• Ductus deferens (vas deferens): carries sperm from epididymis to ejaculatory duct and prostatic urethra.
• Spermatic Cords: hold blood vessels, nerves, and ductus deferens to the testes.
• Urethra: carries sperm and urine; secretes lubricating solution before ejaculation.
• Semen consists of sperm plus secretions from accessory glands.
• Accessory Glands: these glands increase sperm's survival outside the body. 
• Seminal vesicles: produce fructose (sugar), nutrients, prostaglandins to stimulate urethra contraction, and enzymes to thicken ejaculate.
• Prostate gland: secrete milky fluid enhancing sperm mobility and thickening ejaculate; prone to STDs and tumors.
• Bulbourethral glands: lubricate and neutralize the acid from urine in the male urethra.
• Penis: designed to deliver semen.
• Penis contains corpora spongiosum, corpora cavernosa and smooth muscle and connective tissues. 
• Erectile bodies: spongy, blood vessel rich network, dilate during arousal.
• Veins that drain penis are compressed during erection.
• Vasodilation from parasympathetic branch causes erection.
• Ejaculation from sympathetic branch contracting smooth muscles along reproductive tract.

Female Reproductive System

• The female reproductive system produces ova (eggs) and sex hormones.
• These organs provide an environment for internal fertilization and development. The female reproductive system also goes through changes during the menstrual cycle.
• Mammary glands nourish the infant.
• Ovaries: paired organs suspended by ligaments.
• Ovaries structure: surrounded by a fibrous capsule, divided into cortex (ova) and medulla (vascular tissue).
• Ovaries function: oogenesis and female hormone production.
• Ovaries respond to follicle-stimulating hormone (FSH) to mature ova, only one egg released each month.
• Estrogen and progesterone released by ovaries regulate the menstrual cycle.
• Ovarian Cycle stages: Follicular phase, Ovulation, Luteal phase
• Follicular phase-(first two weeks): follicles develop and mature, releasing eggs (oocytes.)
• Ovulation (midcycle): the mature follicle ruptures, releasing oocyte, due to Luteinizing Hormone (LH) release.
• Luteal phase-(second two weeks): ruptured follicle becomes the corpus luteum that produces progesterone.
• If pregnancy fails, corpus luteum degenerates, initiating the next cycle.
• Oogenesis (in fetal development): meiosis I begins but is not completed.
• Primary oocytes in ovaries remain in prophase I until puberty.
• At ovulation, primary oocyte completes meiosis I, starts meiosis II
• Meiosis II completed if fertilization occurs, resulting in ovum.
• Uterine/fallopian tubes: these tubes carry ova to uterus.
• Ciliated epithelium inside tubes guides ova towards the uterus.
• Muscles contraction (peristaltic waves) aids in movement.
• Non-ciliated cells along the tube nourish ova or the developing embryo.
• Uterus: pear-shaped muscular pouch superior to bladder, receives embryo.
• Uterus walls have 3 layers (perimetrium, myometrium, and endometrium).
• The thick endometrium undergoes changes during menstrual cycle.
• Cervix: opening of the uterus, dilates during childbirth. 
• Vagina: birth canal, the opening that leads to the cervix.
• Vagina structure: very flexible, composed of adventitia, muscularis, and mucosa layers.
• Vagina produces glycogen to support beneficial bacteria producing lactic acid.
• External genitalia (vulva): mons pubis, labia majora, clitoris, vestibule (vaginal and urethral orifices, vestibule glands), and labia minora.
• Mammary glands are modified sweat glands to produce milk after childbirth.
• Mammary glands appear as rudimentary structures in both genders; after puberty, ducts grow but glands do not fully develop, mainly adipose.