Urinary System Flashcards

Objectives

• Identify the major anatomical components of the urinary system.
• Understand the role of each nephron portion in kidney function.
• Trace blood flow through the kidney, starting with the renal artery.
• Understand the relationship between the ureter, urinary bladder, and urethra.
• Describe how the histology of the urinary bladder contributes to its function.
• Assess urine composition using the urinalysis dipstick and Sedi-stain.

Introduction

• The urinary system removes waste and excess water from circulation.
• Approximately 25% of cardiac output goes to the kidneys.
• Over 1 L of blood is filtered every minute.
• Kidney failure requires dialysis.
• The urinary system pathway is: blood → kidney → ureter → urinary bladder → urethra.
• The nephron is the functional unit where filtrate is transferred from blood to renal tubules.
• Filtrate is adjusted through excretion and reabsorption to produce urine.

Renal Blood Supply

• The kidney receives blood from the abdominal aorta via the renal artery.
• Blood enters the kidney at the renal hilum, branching into 4-5 segmental arteries.
• Segmental arteries branch into interlobar arteries along the renal column between renal pyramids.
• As segmental arteries enter the renal cortex, they branch into arcuate arteries, which arc over the superior margin of the renal pyramids.
• Cortical radiate arteries (interlobular arteries) branch from arcuate arteries, narrowing to become afferent arterioles that serve the nephron.
• Efferent arterioles from the glomerulus form peritubular capillaries associated with renal tubules for reabsorption.
• Peritubular capillaries converge to form cortical radiate veins in the renal cortex.
• Cortical radiate veins transmit to interlobar veins and leave the kidneys via the renal veins, delivering filtered blood to the inferior vena cava.

The Nephron

• Fluid filtered through the glomerulus is collected by the glomerular (Bowman’s) capsule.
• The fluid enters the proximal convoluted tubule (PCT) where simple cuboidal epithelium performs bulk absorption.
• Amino acids, glucose, and water are reabsorbed into interstitial spaces, then diffuse into peritubular capillaries.
• Filtrate descends into the descending segment of the Loop of Henle where water is reabsorbed via aquaporin channels.
• In the ascending Loop of Henle, urea is actively secreted into the tubule, while K^+, Na^+, and Cl^- ions are reabsorbed. Water remains trapped due to the lack of aquaporin channels.
• Lastly, the filtrate enters the distal convoluted tubule (DCT), where electrolytes and water are reabsorbed, while K^+, H^+, and some drugs are actively secreted into the tubule.

Distal Urinary System Structures

• Several tubules converge onto the collecting ducts, which descend through the renal pyramid.
• Collecting ducts combine to form the papillary duct, through which filtrate exits via the renal papilla.
• Urine from renal papillae enters the minor calyx (up to 13 in each kidney).
• Minor calyces converge to form three major calyces: superior, middle, and inferior.
• Urine is collected in the renal pelvis, which funnels urine to the ureters.
• The renal pelvis converges into bilateral ureters, descending through the abdominal cavity to the urinary bladder.
• Ureters descend below the urinary bladder before bending upward, forming a valve-like structure.
• Two ureters and the urethra form the trigone of the urinary bladder.
• The bladder is composed of transitional epithelium for expandability.
• The detrusor muscle enables forceful emptying of the bladder.
• Internal and external urethral sphincters regulate urine flow into the urethra.
• Urethra length differs by sex: ~19 cm in males, ~3.5 cm in females.
• Shorter urethra in females makes them more prone to urinary tract infections.

Analysis of Urine

• Urinalysis (U/A) is a clinical tool for assessing patient health.
• The standard U/A tests 10 parameters:
  • (a) leukocyte esterase
  • (b) nitrite
  • (c) urobilinogen
  • (d) protein
  • (e) pH
  • (f) blood
  • (g) specific gravity
  • (h) ketones
  • (i) bilirubin
  • (j) glucose
• Blood or protein in urine indicates a compromised glomerular filtration membrane.
• High glucose indicates glycemic issues, including diabetes.
• Specific gravity (SG) is measured via U/A dipstick or urinometer, measuring fluid density.
• High dissolved solute results in high SG, indicating pathologies.
• Urine is analyzed for sediment, including crystalline materials (e.g., uric acid) or epithelial/blood cells.
• The procedure involves centrifuging urine, pouring off the supernatant, and mixing the sediment with Sedi-stain to highlight cellular and crystalline structures.

Procedures

Part A: Overview of the Male and Female Urinary Systems

• Review gross anatomy of the urinary system.
• Using lab models, along with Figure 1 from this lab exercise and Figures 26.1 – 26.3 from your text, as references, identify the following urinary system structures:
  • Kidney
  • Ureter
  • Urinary bladder
  • Urethra
• Answer questions 1 – 2 in the post-lab section.

Part B: The Kidney

• Review important structures and features of the human kidney.
• Using the lab models, along with Figure 2 from this lab exercise and Figure 26.4 from your text as references, identify the following renal structures:
  • Renal capsule
  • Renal cortex
  • Renal medulla
  • Renal pyramid
  • Renal papilla
  • Minor calyx
  • Major calyx
  • Renal pelvis
  • Renal sinus
  • Hilum
• Answer question 3 in the post-lab section.

Part C: The Nephron

• Review important structures and features associated with the nephron.
• Using the lab models along with Figures 26.6 – 26.7 from your text as references, identify the following structures associated with the nephron and renal corpuscle.
  • Cortical nephron
  • Juxtamedullary nephron
  • Renal corpuscle
    • Glomerulus
      • Afferent arteriole
      • Efferent arteriole
    • Glomerular (Bowman’s) capsule
  • Renal tubule
    • Proximal convoluted tubule (PCT)
    • Loop of Henle
    • Distal convoluted tubule (DCT)
  • Collecting duct
  • Papillary duct
• View a kidney tissue specimen under the microscope and sketch your results in the space provided below.
• Answer questions 4 – 6 in the post-lab section.

Part D: Renal Blood Supply

• Review the blood vessels that serve the human kidney.
• Using the lab models along with Figure 26.5 from your text as references, identify the following blood vessels:
  • Renal artery
    • Segmental arteries
    • Interlobar arteries
    • Arcuate arteries
    • Cortical radiate arteries
    • Afferent arterioles
    • Glomerulus
    • Efferent arterioles
  • Peritubular capillaries
  • Cortical radiate veins
    • Arcuate veins
    • Interlobar veins
    • Renal vein
• Answer question 7 in the post-lab section.

Part E: Ureters, Urinary Bladder and Urethra

• Review the distal urinary system structures.
• Using the lab models along with Figures 26.17 – 26.19 from your text as references, identify the following urinary system structures:
  • Ureters
  • Urinary bladder
    • Median umbilical ligament
    • Lateral umbilical ligaments
    • Trigone
      • Ureteral openings
      • Urethral opening
      • Neck (of urinary bladder)
    • Internal urethral sphincter
    • Detrusor muscle
  • Male urethra:
    • Prostatic urethra
    • Membranous urethra
    • Spongy (penile) urethra
  • External urethral orifice
  • External urethral sphincter
• View a tissue section of the ureter under the microscope and sketch your observations in the space below.
• View each of the bladder specimen – one distended, the other relaxed – under the microscope and sketch your observations in the spaces below.
• Answer questions 8 - 10 in the post-lab section.

Part F: Analysis of Urine

Urinalysis

• Collect a midstream urine sample by placing the collection vessel within the path of the urine a second or so after starting urination. This is important so that you avoid collecting bacteria and yeast that may have accumulated at the distal end of the urethra.
• Perform the urinalysis by placing the dipstick in the urine for no longer than 1 second. Drag the underside of the dipstick along the edge of the container to remove excess urine.
• Place the dipstick on an absorbent paper towel.
• Read the results as suggested by the manufacturer. Note that some tests may need to develop for longer periods of time.
• Note your results in Table 1 below.
• Dispose of the dipstick in the container filled with bleach. Reserve the urine for the additional tests described below.

Specific Gravity via Urinometer

• Half fill a urinometer cylinder with a portion of your urine sample.
• Place the urinometer (see Figure 3) into the cylinder and wait until it stops moving and is free from the walls of the cylinder before reading the measurement.
• Determine the density of the sample by estimating the specific gravity based on the graduated markings on the urinometer.
• Record your results in the space below.

Microscopic Analysis

• Fill a conical centrifuge tube with 10 mL of urine.
• Place the tube in a centrifuge. Be sure to place a second tube with 10 mL of water opposite of the tube with urine in order to balance the centrifuge. This is important so that the centrifuge does not wobble during operation.
• Centrifuge the sample at 2000 rpm for 10 minutes.
• Following centrifugation, carefully pour off the supernatant urine into the sink.
• Turn the tube upright and then mix the sediment with the small amount of residual urine by flicking with your finger a few times.
• Using a disposable pipet, transfer a drop of sediment resuspended in urine to a clean microscope slide.
• Add one drop of Sedistain to the urinary sediment that has been placed on the slide.
• Mix by gently rocking the slide back and forth without losing any of the sample off of the edges.
• Place a coverslip on top of the specimen and visualize the sample using the microscope.
• Sketch 4 selected fields of view within the spaces provided below.
• NOTE: Figures 4 – 6 depict three types of crystals sometimes seen in urine, as well as epithelial and white blood cells.
• Answer questions 11 in the post-lab section.

Part G: Check-off (Required)

Before departing from the lab, identify and confirm the following structures and features to your instructor or teaching assistant:

• Renal papilla (Kidney Plaque)
• Glomerular capsule (Microscope)
• Renal artery (Model)
• Glomerulus (Microscope)
• Renal sinus (Model)
• Specific gravity values (Data)
• Urinary sediment (Microscope)
• Interlobar vein (Kidney Plaque)
• Renal pyramid (Kidney Plaque
• Ureter (Model)

Post-Lab Questions

1. Identify the female urogenital structures being indicated in the figure shown below.
2. Identify the male urogenital structures being indicated in the figure shown below.
3. Identify key renal structures being indicated on the diagram of the kidney shown below.
4. Identify the major features of the nephron which are being indicated on the diagram below.
5. Identify important features of the corpuscle which are indicated in the figure below
6. On your sketch of kidney tissue performed in Part C, label the following nephron structures: (a) glomerular (Bowman’s) capsule; (b) glomerulus; (c) renal tubule; and (d) collecting duct.
7. Identify the blood vessels that serve the kidneys being indicated on the diagram shown below.
8. Identify important structures of the lower part of the urinary system which are indicated on the figures shown below. Additionally, identify the histological structures being indicated on the micrograph of bladder tissue also shown in this figure.
9. Identify key features of the ureter which are indicated in the figure below which features a cross section of ureter tissue.
10. What type of epithelial tissue makes up the urinary bladder wall? Based on your observations using the microscope, describe how this epithelium permits extensibility in this organ for the purpose of storing urine.
11. Answer the next two questions based on your analysis of urine:
    • What does specific gravity (SG) measure? Were your SG results consistent between the urinometer and dipstick methods of testing? If not, why do you think a difference exists?
    • What types of sediment did you observe in your urine specimen. If you refer to external resources, please cite those in your answer.