Urinary System and Nephron Quiz

Urinary System

• Functions: Excretion of waste, regulation of blood volume and blood pressure, regulation of plasma ions, regulation of extracellular fluid pH, regulation of nutrients and vitamin D synthesis, regulation of erythrocyte production.

The Nephron

• Functional Unit: Forms urine, consists of:
  • Renal Corpuscle:
    • Bowman's capsule
    • Glomerulus (porous capillary)
  • Renal Tubule:
    • PCT (proximal convoluted tubule)
    • Loop of Henle (descending and ascending limbs)
    • DCT (distal convoluted tubule)

Filtration Vasculature

• Blood Supply: Afferent arteriole brings blood to the glomerulus, blood is filtered across the filtration membrane, blood exits through the efferent arteriole.
• Urine Formation Processes:
  1. Filtration (inside renal corpuscle)
  2. Reabsorption (in the PCT)
  3. Secretion (in the DCT)

Glomerular Filtration

• Anatomy of the Filtration Membrane:
  • Glomerular endothelium (fenestrated)
  • Basement membrane
  • Physiology of Filtration: Force promoting filtration.
• Filterable Molecules: Water, ions (e.g., K+, Na+, Cl-), nutrients (e.g., glucose, amino acids), wastes (e.g., urea, creatinine).
• Non-filterable Molecules: Blood cells, plasma proteins.

Tubular Reabsorption

• Processes: PCT modified for reabsorption with brush border (microvilli) increasing surface area. Mechanisms include active transport (e.g., Na+), passive transport (e.g., Cl-), facilitated diffusion (e.g., glucose), and osmosis (water). Some molecules have a maximum transport rate.
• Glucose transport max: When glucose exceeds the carrier protein capacity, glucose appears in the urine (osmotic diuresis).

Tubular Secretion

• Mechanism: Some molecules are secreted by hormones. For example, K+ secretion is driven by aldosterone, and H+ secretion helps balance pH.
  • Some substances are actively transported.

Regulation of Urine Concentration and Volume

• Renin-angiotensin-aldosterone Mechanism: Hormone mechanism important in increasing water reabsorption, related to blood pressure control.
• Antidiuretic Hormone (ADH): Hormone that decreases urine volume and is related to conserving water.
• Atrial natriuretic hormone (ANP): Hormone that leads to increasing water excretion..

Composition of Urine

• Mostly Water (95%): The remaining 5% consists of dissolved solutes like nitrogenous wastes (e.g., urea, creatinine), uric acid, and other substances. Abnormal components may signal disease.

Dialysis

• Process: Diffusion of waste products across a dialysis membrane.

Acid-Base Balance

• PH Scale: Indicates the concentration of H+ ions in a solution (ranges from 0 extremely acidic to 14 excessively alkaline).
• Acids: Substances that release hydrogen ions.
• Bases: Substances that accept hydrogen ions.
• Chemical Buffers (e.g., bicarbonate buffer): Help maintain stable pH in the body. These include protein buffers and the carbonic acid-bicarbonate buffer system, which acts quickly. The respiratory or renal systems also contribute, responding more slowly.

Reproduction System

• Meiosis: Specialized cell division producing haploid cells. Homologous chromosomes are separated.

  • Meiosis I: Chromosomes, crossing over
  • Meiosis II: Sister chromatids separate; results in four haploid cells.

• Male Reproductive Organs (Testes): Location, anatomy (Dartos muscle, spermatic cord, and cremaster muscle), descent and cryptorchidism, seminiferous tubules, interstitial cells, rete testes, spermatozoa anatomy (head, midpiece, tail);.

• **Female reproductive organs (Ovaries):**Location, anatomy (Ovaries and associated structures: ligaments, primordial follicles, primary follicle, secondary follicle, mature follicle, corpus luteum, scar) meiosis and oogenesis.

• Ovarian Cycle: Follicular phase (FSH dominant), ovulation (spike in LH, and estrogen), Luteal phase (LH promotes corpus luteum and progestins).

• Uterine Cycle: Menstrual, proliferative, and secretory phases; related to changes in hormone levels. Functions of estrogen.

• Hormones: (e.g., testosterone, estrogen, progesterone, FSH, LH, GnRH) regulate and support the reproductive processes..

• Menopause/Andropause: Changes in hormone levels and reproductive function as one ages.

Other

• Other substances that can affect urine production like caffeine and alcohol.
• The JG apparatus stimulates renin-angiotensin-aldosterone mechanism including factors impacting release.