Repro

• Reproduction


  Not Replication
• Sexual reproduction


  • Biparental: Offspring receives genes from two parents
  • Offspring is not genetically identical to either one
• Gametes


  Sperm and ovum produced by each parent, each only has 1 set of chromosomes (haploid, n)
• Zygote


  Fertilized ovum, has a combination of both parents' genes (diploid, 2n)
• Chromosomal Sex Determination


  • Our cells contain 23 pairs of chromosomes, 22 pairs of autosomes, 1 pair of sex chromosomes (XY males; XX females)
  • Males produce half Y-carrying sperm and half X-carrying sperm
  • All eggs carry the X chromosome
  • Sex of child determined by type of sperm that fertilizes mother's egg
• Reproductive roles


  • Primary sex organs (gonads): Produce gametes
  • Secondary sex organs: Organs other than gonads that are necessary for reproduction
• Male's reproductive system


  • Serves to produce motile sperm and introduce them into the female body
  • Has ducts, glands and a copulatory organ (penis) for introducing their gametes into the female reproductive tract
• Female's reproductive system


  • Produces egg/ovum, receives sperm, provides for gametes' union, harbors fetus, and nourishes offspring
  • Has uterine tubes, harbors developing fetus in uterus, has a copulatory organ (vagina) for receiving the sperm
• Scrotum


  Consists of ~5 layers: Epidermis, Tunica dartos, Stratum subdarticum, Tunica vaginalis-parietal layer, Tunica vaginalis-visceral layer
• Mechanisms to regulate the temperature of the testes

  1. Cremaster: Contracts in cold, relaxes in warm

  2. Tunica Dartos: Smooth muscle contracts when cold, reduces surface area and heat loss

  3. Pampiniform plexus: Countercurrent heat exchanger
• Testes


  Combined endocrine and exocrine glands that produce sex hormones and sperm
• Seminiferous tubules


  • Ducts where sperm are produced, lined with germinal epithelium, spermatogonia germ cells, and Sertoli nurse cells
• Leydig cells


  Cells between tubules that produce testosterone
• Blood-testis barrier


  Formed by tight junctions between Sertoli cells, separates sperm from immune system
• Sperm production and transport


  Produced in seminiferous tubules, funneled to rete testis, leave testis through epididymis, mature as they travel through duct
• Spermatic ducts


  • Efferent ductules, epididymis, ductus deferens, ejaculatory duct
• Seminal vesicles


  Pair of glands posterior to bladder that form 60% of semen
• Prostate


  Surrounds urethra and ejaculatory duct, produces 30% of semen
• Bulbourethral glands


  Produce pre-ejaculate fluid that lubricates the penis
• Semen


  Fluid expelled during orgasm, contains sperm and secretions from accessory glands
• Semen


  • Elevated pH and energy source (fructose) required for sperm motility
  • Prostaglandins may thin cervical mucus and stimulate uterine contractions
• Seminal vesicle fluid


  Contains fructose, citrate, prostaglandins, and proseminogelin
• Prostatic fluid


  Contains calcium, citrate, lipids, phosphate ions, clotting enzyme, and prostate-specific antigen
• Bulbourethral gland fluid


  Clear, salty, viscous, alkaline fluid that lubricates the urethra
• Seminogelin


  Sticky fibrin-like protein formed from proseminogelin, helps entangle sperm and stick to vagina/cervix
• Penis


  • Composed of erectile tissue enclosing the penile urethra, has root, shaft, and glans
• Corpus cavernosum


  Large spongy structure that fills with blood during erection
• Corpus spongiosum


  Smaller spongy structure surrounding the urethra
• Glans penis


  Enlarged free end of the penis, richly supplied with nerves and nerve endings
• Blood flow to penis


  Internal pudendal artery divides into dorsal artery (supplies skin) and deep artery (fills cavernous spaces during erection)
• Innervation of penis


  Richly innervated, with autonomic and somatic motor fibers
• Male sexual response


  1. Erection (parasympathetic): Vasocongestion, myotonia, increased heart rate, blood pressure, ventilation

  2. Ejaculation (sympathetic): Emission (peristalsis propels sperm) and expulsion (muscular contractions)
• Erectile dysfunction


  Inability to attain an erection, due to increased fight-or-flight response and not enough nitric oxide release
• Phosphodiesterase inhibitors


  Drugs like Viagra that prolong erection by inhibiting breakdown of cGMP
• Orgasm and ejaculation


  1. Orgasm: Intense climactic reaction, further elevation of heart rate, blood pressure, breathing

  2. Emission: Sympathetic peristalsis propels sperm

  3. Expulsion: Muscular contractions expel semen from urethra
• Resolution phase


  Body variables return to pre-excitement state, penis becomes flaccid
• Refractory period


  Period after orgasm in which it is impossible to attain another erection or orgasm
• Spermatogenesis


  Primordial germ cells form spermatogonia, which undergo meiosis to produce sperm (400 million per day)
• The larger the testis, the more parent spermatogonia you can have, and the more sperm you can produce
• Resolution Phase


  Body variables return to pre-excitement state