Exam Review Notes (second part)

Large Intestines

• Chyme moves through the small intestines, then through the ileocecal valve/junction, and into the large intestines.
• In the large intestines, it's called feces.
• Mechanical digestion:
  • Haustral churning: Movement of waste through the large intestines.
    • Haustra: pockets in the large intestines that hold waste.
  • Peristalsis: occurs throughout the entire GI tract.
  • Mass movement: Moving waste to the colon.
• Chemical digestion: Bacteria helps with chemical digestion.
• Absorption of water: main function of the large intestines.

Enteric and Autonomic Nervous Systems

• Enteric nervous system: part of the autonomic nervous system.
  • Myenteric plexus: controls the smooth muscle of digestion.
  • Submucosal plexus: controls glands and endocrine cells.
• Autonomic nervous system:
  • Parasympathetic branch:
    • Stimulation increases peristalsis and secretions via the vagus nerve (rest and digest).
  • Sympathetic branch:
    • Contraction of sphincters.
    • Inhibition of peristalsis and secretion (stopping digestion).

Male Reproductive System

• Scrotum:
  • Protects the testes.
  • Regulates the temperature of the testes.
• Testes:
  • Produce sperm.
  • Secrete hormones.
• Seminiferous tubules:
  • Location of sperm production.
  • Spermatogenic cells are located here.
• Two major cells:
  • Sertoli cells:
    • Support and protect spermatogenesis (sperm production).
    • Bind testosterone.
    • Secrete inhibin.
  • Leydig (interstitial) cells:
    • Produce testosterone, which is necessary for spermatogenesis.
• Spermatogenic cells:
  • Spermatogonium: stem cell.
  • Primary spermatocyte.
  • Secondary spermatocyte.
  • Spermatid.
  • Sperm cell (spermatozoon).
• Spermatogenesis:
  • Occurs in the seminiferous tubules of the testes.
  • Takes 64 days.
  • Spermatogonia mature into primary spermatocytes, then secondary spermatocytes, then spermatids, and finally, sperm.

Hormones and Sperm Production

• Hypothalamus:
  • Releases gonadotropin-releasing hormone (GnRH).
• Anterior pituitary:
  • GnRH triggers the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
• FSH:
  • Causes spermatogonia to start spermatogenesis.
  • Sertoli cells support sperm production.
• LH:
  • Goes to Leydig cells and causes testosterone to be secreted.
• Testosterone:
  • Supports the maturation of sperm.
• FSH and testosterone stimulate spermatogenesis.
• Negative feedback:
  • Testosterone production goes to the anterior pituitary gland and hypothalamus to turn off the process when there is enough.
• Inhibin:
  • Inhibits spermatogenesis by stopping the secretion of FSH from the anterior pituitary gland.
• Sperm production:
  • Must happen at 3 degrees lower than body temperature.
• Testicular veins:
  • Superficial, so heat exchange can occur with the air.
  • Countercurrent heat exchange with the testicular artery.
• Cremaster muscle:
  • Helps with scrotal movements, pulling the scrotum up if it's cold and relaxing if it's hot.
• Cremaster reflex:
  • Scratching the inside of the thigh gently will cause the cremaster muscle to pull that side of the scrotum away to protect it.

Maturation of Sperm

• Spermatozoa (sperm) entering the epididymis are nonmotile and cannot fertilize.
• Epididymis:
  • Sperm mature and are stored here until they are released.
• Ejaculate (semen):
  • Sperm.
  • Seminal vesicle fluid.
  • Prostate gland fluid.
  • Bulbourethral gland fluid.
• Seminiferous tubules:
  • Spermatogonia mature into primary spermatocytes, then secondary spermatocytes to the spermatids, and then finally, the sperm.
• Vas deferens, then the ejaculatory ducts, and finally, the different parts of the urethra into hopefully, we'll see the outside.

Contents of Ejaculate

• Seminal vesicle fluid:
  • 60% of the ejaculate.
  • Enters the ejaculatory duct.
  • Alkaline viscous fluid (raincoat).
  • Fructose (lunchbox).
  • Clotting proteins and prostaglandins.
• Prostate gland:
  • Secretes into the prostatic urethra.
  • Citric acid (snack).
  • Clotting enzymes (clumper).
• Bulbourethral gland:
  • Secreting into the spongy urethra.
  • Alkaline fluid (rain hat).
  • Mucus (lubricator).
• Penis
  • Male organ of population. Depositing the semen into the female reproduction tract
  • Shaft and the gland penis
  • Two different erectile tissues: corpus cavernosum fills with blood; corpus spongiosum surround the urethra

Sperm

• Acrosome: cap of digestive enzymes.
• Flagellar tail: become motile in the epididymis after being deposited in a female