a and p lecture 21

Weekly Advice Quiz

• Opens after class today

• More focus on materials after the last lecture on renal system chart 6

• This quiz is counted as an extra, with the possibility of dropping 3 marks instead of 2 for some students

Final Exam Details

• Term/final exam timeline discussed

• Reviewing quiz feedback can be advantageous if completed earlier

Kidney Structure

• Kidney Parts

  • Renal Cortex: Outer portion

  • Renal Medulla: Inner region

• Nephrons: Over a million per kidney, the functional units for urine production and modification

Nephron Overview

• Structure: Long tube structure

  • Renal Corpuscle: Blind end with Bowman Capsule

  • Proximal Convoluted Tube: In the renal cortex

  • Loop of Henle:

    • Descending Limb: Leads down into the medulla

    • Ascending Limb: Comes back up into the cortex

  • Distal Convoluted Tube: Connects to the collecting duct

• Connection to Collecting Ducts: Hundreds/thousands of nephrons drain into the collecting duct

Kidney Function

• Regulation of Water and Salt Balance: To remove metabolic waste products via urine

• Daily production of approx. 60 liters of primary urine from blood

• Modification to Definitive Urine: Only about 2 liters excreted daily, most water is reabsorbed

Primary Urine Formation

• Produced through pressure-driven ultrafiltration in the renal corpuscle

• Filter includes:

  • Fenestrated Blood Capillaries: Allows small particles to pass

  • Basilar Membrane: Acts as a gel-like filter for larger particles

  • Podocytes: Epithelial cells forming filtration slits

• Glomerular Filtration Rate (GFR): Rate influenced by blood pressure and resistance to flow; critical to urine production

Substances Found in Primary Urine vs. Blood

• Found in Primary Urine: Water, glucose, amino acids, metabolic waste (urea, uric acid, creatinine), hormones

• Not Found in Primary Urine: Blood cells, plasma proteins, bound hormones

Renal Autoregulation

• Mechanisms to maintain GFR regardless of systemic blood pressure

• Afferent Arterioles: Control blood flow into the glomerulus to maintain filtration rate

  • Constriction/Dilation based on the body's needs

  • Hormonal Regulation: Renin-angiotensin-aldosterone system (RAAS) involved

Hormonal Control of Kidney Function

• Angiotensin II:

  • Vasoconstrictor that increases blood pressure

  • Stimulates water retention in kidneys and thirst response in the brain

• Antidiuretic Hormone (ADH):

  • Promotes water reabsorption to decrease urine output and concentrate urine

• Aldosterone:

  • Increases sodium reabsorption, which leads to water retention

Nephron Tubule Function

• Includes reabsorption and secretion for urine modification

• Stages include loop of Henle, distal convoluted tube, and collecting duct

• Final urine volume and concentration determined through these processes

Active and Passive Transport

• Key transport mechanisms discussed: passive diffusion (osmosis), primary and secondary active transport

• Use of ion channels, carrier proteins for solute transport

• Importance of gradients for efficient solute exchange

Concentration and Dilution of Urine

• Conditions for hypoosmotic (dilute) and hyperosmotic (concentrated) urine

• Implication of hydration status on urine output

Conclusion

• System of kidney function intricately linked to body's homeostasis through filtration, reabsorption, secretion, regulated by various mechanisms and hormones

• A comprehensive understanding of kidney physiology is essential for recognizing renal health and function.