Chapter 1: Introduction to the Renal System

Tissue Structure

  • Renal fascia

    • Tough and cartilaginous type of tissue

    • Functions to protect surrounding structures, specifically the kidneys

    • Prevents outward growth of kidney cancer into normal tissues

Anatomy of the Kidney

  • General Structure

    • Composed of two primary regions: cortex and medulla

    • Cortex:

    • Superficial part of the kidney

    • Approximately 1 centimeter thick

    • Medulla:

    • Deeper area consisting of renal pyramids and renal columns

    • Contains about 10 renal pyramids per kidney

    • Renal pyramid:

    • Inner tip called the papilla, where urine exits

    • Renal column:

    • Tissue found between pyramids

Blood Supply to the Kidneys

  • Renal artery:

    • Directly branches from the aorta

    • Splits into segmental arteries which further divide into interlobar arteries

  • Interlobar arteries:

    • Run in renal columns between pyramids

  • Arcuate arteries:

    • Formed at the junction of the pyramid and cortex

  • Cortical radiate arteries:

    • Branch from the arcuate arteries and supply blood to the cortex

    • Give rise to afferent arterioles that supply blood to nephron glomeruli

    • Importance: Understanding blood vessels critical for tests

Urine Collection System

  • Urine formation and collection:

    • Papilla releases urine into minor calyx

    • Minor calyces join to form major calyx

    • Major calyces converge to create renal pelvis

    • Renal pelvis narrows to form the ureter, which transports urine to the bladder

    • Clinical note: Kidney stones often get trapped in the narrow ureter, causing pain

Nephron Structure

  • Types of Nephrons:

    • Cortical nephron:

    • Located higher in the cortex

    • Short nephron loops, involved in urine composition

    • Juxtamedullary nephron:

    • Located adjacent to the medulla

    • Long nephron loops, concentrated on water retention

Hormonal Regulation of the Nephron

  • Distal convoluted tubule:

    • Site for action of several hormones

  • Hormones involved:

    • Antidiuretic hormone (ADH):

    • Increases water reabsorption

    • Aldosterone:

    • Promotes sodium reabsorption, water follows sodium

    • Atrial natriuretic peptide (ANP):

    • Induces sodium and water excretion during volume overload

Juxtaglomerular Apparatus

  • Role:

    • Senses urine concentration and adjusts glomerular filtration rate (GFR) accordingly

    • If urine is concentrated:

    • Afferent arteriole constricts to reduce blood flow and decrease water filtering

Final Excretion of Urine

  • Collecting duct:

    • Final adjustment of urine concentration occurs here

    • Osmolarity of renal pyramid increases deeper into the tissue

    • High osmolarity encourages water reabsorption into the body

Common Urinary Disorders

  • Kidney stones:

    • Genetic predisposition, pain caused by sharp stones scraping ureter

    • Prevention: Hydration to dilute urine and decrease stone formation

  • Kidney Transplant and Ethical Considerations

    • Ethical dilemma in donor selection based on age and health of recipient

    • Use of pig kidneys in research to address transplant shortages

    • Pig kidneys are genetically altered to lessen immune rejection

Bladder Anatomy

  • Urinary bladder structure:

    • Contains a region known as the trigone, formed by openings of ureters and urethra

    • Detrusor muscle:

    • Smooth muscle responsible for bladder contraction during urination

    • Rugae:

    • Folds in the bladder wall allowing for expansion

    • Normal urine volume after voiding: typically around zero to prevent infection

Urethra Structure

  • Differences between male and female urethra:

    • Male urethra: longer, divided into three sections:

    • Prostatic, membranous, and penile

    • Internal urethra sphincter to prevent retrograde ejaculation during urination

    • Female urethra: shorter, susceptible to stress urinary incontinence

Conclusion

  • Understanding kidney structure and function is essential for grasping how urine is formed and excreted, as well as the overall health of the urinary system.