Exercise 9: Urinary System

Figure 9.1 Illustration of a woodchuck kidney from an anterior view and highlighting the internal anatomy of the kidney.

Exercise 9 Learning Goals 

After completing this lab, you should be able to: 

• Identify structures of the urinary system
• Understand the basic function of urinary structures
• Illustrate the macroscopic and microscopic structures of the kidneys
• Outline how blood is filtered in the kidney nephron
• Understand how urinalysis can help diagnose diseases

Pre-Lab Activities for Exercise 9

Pre-Lab Activity 9.1:  Identify the Major Organs of the Urinary System

Using the image below, label the major anatomical structures of the urinary system.

Figure 9.2 Major Structures of the Urinary System

1. Which organ(s) are responsible for PRODUCING urine?
2. Which structures/organs are responsible for STORING urine?
3. Why do the kidneys receive such direct and major blood flow to/from them? How does their location relative to major blood vessels of the abdomen relate to their function?

Pre-Lab Activity 9.2 Blood Flow in the Kidney

Use the following terms to label the diagram below: peritubular capillaries, renal artery, segmental artery, renal vein, interlobar artery, interlobar vein, arcuate vein, arcuate artery, cortical artery, cortical vein, afferent arteriole, glomerulus, and efferent arteriole.

Figure 9.3 Blood Flow to the Kidneys. The figure depicts a kidney and nephron with boxes pointing to structures to label.

1. Where in the kidney are the parts of a nephron found?
2. What are the two distinct types of nephrons? What is different about them?

Pre-Lab Activity 9.3 Terms Associated with the Urinary System

Use your required textbook to complete the table below.

Lab Exercise 9: Urinary Anatomy

The urinary system’s key role is to control the composition and volume of blood and remove waste. This system contributes significantly to homeostasis by altering blood composition, pH, volume, and pressure. And riding the body of nitrogenous and other waste products such as ammonia, salts, drugs, and other toxins. Elevated levels of waste products in the blood can be damaging to other organ systems; therefore, it is important to filter the blood and remove excess waste products regularly and efficiently. The urinary system includes 2 kidneys; 2 ureters; 1 urinary bladder; and 1 urethra.

Figure 9.4 Urinary system of a young child. The figure depicts the left and right kidneys, bladder and urethra.Kidneys

Of all the organs in the urinary system, the kidneys are the most important. They are paired bean-shaped structures located in the abdomen. The kidneys are retroperitoneal, outside the peritoneal membrane, and nearer to the posterior abdominal wall. They are partially protected by ribs 11 and 12 and positioned such that their hilum faces medial, serving as entry and exit routes for the ureters, blood and lymphatic vessels and nerves. The left kidney is at the level of T12-L3, whereas the right kidney is slightly lower due to the liver placement. The kidneys are covered directly by connective tissue called the renal capsule.

The region of the kidney under the renal capsule is known as the renal cortex, a highly vascularized area where the functional units of the kidneys are found, the nephron. The area deep to the cortex is known as the renal medulla.

The medulla includes cone-shaped structures called pyramids, and the area between the pyramids is known as the renal columns. Blood is filtered through the nephrons where the waste (in the form of urine) passes through to the papilla, before being collected at the renal pelvis. Urine drains from the pyramids into the pelvis via cup-like structures known as major and minor calyces. Minor calyces are directly connected to individual pyramids at the papilla. Urine drains from these minor calyces into larger major calyces before being collected at the pelvis and continuing into the ureter. The ureter transports the urine to the bladder, where it is eventually expelled through the urethra.

Figure 9.5 Internal Anatomy of the Left Kidney. Figure shows a longitudinal section of the left kidney with structures labeled.

The Nephron

The best way to understand how blood is filtered is to learn blood circulation through the kidneys. The renal hilum is the site where the two major blood vessels, the renal vein and renal artery, along with the renal nerves, exit and enter the kidney. The hilum is also where the renal pelvis forms the ureter, before exiting the kidney. The renal artery carrying oxygen, nutrients and waste products enters the kidney and branches towards the cortex via the renal columns. Within the cortex, the branching artery (now called arterioles) surround millions of nephrons. An afferent arteriole forms a convoluted structure of capillaries called a glomerulus. Due to the blood being under higher pressure at the glomerulus, important molecules such as proteins, glucose, salts, and water, along with waste products, get filtered here. These molecules and waste products get collected in a structure known as the Bowman’s capsule and flow through the various parts of the nephron towards the collecting duct which eventually leads to the ureter. Molecules important for the body's everyday function, such as glucose, get reabsorbed into the blood along the nephron loop.

Figure 9.6 Blood Vessels Surrounding an Individual Nephron.

• What substances are secreted/absorbed in the various parts of the nephron?

Lab Activity 9.1: Identify Urinary Structures

Using a torso or kidney model identify the following structures:

Lab Activity 9.2: Sheep/Pig Kidney Observation

1. Obtain one undyed/dyed sheep/pig kidney from those provided. If uncut- make a longitudinal incision through the kidney.
2. Observe the renal capsule, the thin membranous covering of the kidney.
3. The renal pelvis is the large sac at the base of the kidney. It may be filled with white adipose tissue.
4. The pyramids are the smooth, discolored structures located in the inner core of the kidney, above the pelvis.
5. The calyces are tube-like extensions from the renal pelvis. The pin-prick openings at the ends of the calyces are the papillae.
6. The columns are the tissue between each calyx.
7. The renal medulla is the tissue of the pyramids.
8. The renal cortex is the tissue between the renal capsule to the renal medulla.

Clean up procedure:

• Dispose of all organic debris in the appropriate biohazard containers and clean the dissecting instruments and tray with soap and water before leaving the laboratory. Do not forget to wash your hands with water and soap, and to disinfect the lab bench.

Lab Activity 9.3: Urinary Histology

Examine the slides bladder and kidney section slides using low and high-power magnification. Closely observe the mucosa, muscularis and serosa, making notes of how they are arranged on the slide.

1. After examining the bladder slide on the microscope, use the image of the bladder to identify the following layers: mucosa, muscularis, and serosa.

Figure 9.7 Histology of the Urinary Bladder. Figure shows the pink stain with the transitional epithelium magnified at the top. The nuclei have stained purple in the figure. Photograph by Gina Profetto

1. After examining the kidney slide on the microscope, use the image of the kidney to identify the following: renal corpuscle (Bowman’s Capsule and Glomerulus), renal tubules, and collecting duct.

Figure 9.8 Histology of the Kidney. Photograph by Gina Profetto. Figure shows section of kidney tubules stained with pink and purple dyes. The tubules are lined with cube-shaped cells.

Lab Activity 9.4: Urinalysis

Background:

When observing normal urine, the color ranges from yellow to amber due to the breakdown of products from bile and hemoglobin (urochrome and urobilin). Normal urine is transparent with a mild odor and with a pH between 4.5 to 8.0. Certain foods, drugs, diseases, and amount of water intake can cause lighter or darker colored urine.

Table 9.1: Normal Urine Characteristics

Urinalysis is used by healthcare professionals to assess several factors of urine, including color, pH, specific gravity, and volume, and deviations from the normal range provide information about renal health.

Specific gravity is the density of a solution relative to water, which has a specific gravity of 1.000. The specific gravity of normal urine ranges from 1.003 to 1.032. Specific gravity varies according to fluid intake. A higher specific gravity indicates a higher solute concentration and hints at dehydration.

Glucose should not be detected in normal urine; its presence indicates diabetes mellitus. The kidneys play an essential role in glucose homeostasis and reabsorb all glucose under normal conditions. If blood glucose is too high, as in diabetes, the kidneys will be unable to reabsorb all glucose, resulting in glucose presence in urine. Glucose may normally be present in urine after a big meal or during times of emotional stress.

A trace amount of protein is present in urine. Any change in the color of a protein test strip indicates an elevated level of protein. Diet and disease can affect protein levels in urine. For example, patients with severe anemia usually excrete protein in their urine.

Activity Instructions:

In this activity, you will perform and examine five tests of urinalysis: color, pH, specific gravity, glucose, and protein. The Normal simulated urine sample is designed to produce results indicative of normal characteristics. You will also be provided with two unknown urine samples for urinalysis and asked to report and interpret those results. Students must wear gloves and safety goggles when handling urine samples.

Procedure

1. Take 5 plastic urine specimen containers and use a marking pen to label the containers Normal, A, B, C, and D. Use the labeled graduated cylinders at the side counter to transfer 5 mL of Normal urine to the appropriately labeled container.
2. Return to your lab bench and place the container of simulated urine on the absorbent paper towel. Observe the sample and record the color in the data table below.
3. Use a pen or pencil to label one end of 5 test strips (all in one or individual 5 pH, 5 glucose and 5 protein strips), N, A, B, C, and D.
4. Holding the labeled end, dip the N strip into the Normal sample. Shake off any excess liquid. Lay the strip on the absorbent paper towel.
5. Compare the color of the test strip to the pH color chart or strip packaging. In your data table record the pH of the sample using the color chart below. Also record whether protein and glucose are present in the sample (positive) or absent in the sample (negative) by consulting the chart on the strip packaging.

1. Measure the specific gravity of simulated Normal urine.
   1. Rinse the Hydrometer jar thoroughly with tap water before using.
   2. Fill the jar to the fill-line with the urine sample.
   3. Insert the Hydrometer into the jar as shown in the figure.
   4. Read the fluid level on the Hydrometer scale and record the level in your data table below.
   5. Add or subtract the calibration factor from your measurement. Record the adjusted value in your data table.

Figure 9.9 Hydrometer use and measurement of urine specific gravity.

1. Repeat the specific gravity test for the A, B, C, and D samples and record the results in your data table. Be sure to carefully rinse the Hydrometer and the jar thoroughly between each sample with tap water.
2. Analyze the color, pH, glucose, protein, and specific gravity of each sample, and record the results in your data table.
3. Return the synthetic urine back to the original containers and rinse all the containers used with tap water. The used testing strips may be discarded in the trash.

1. What are the normal results for urine tests regarding?
   1. Color:
   2. pH:
   3. Specific gravity:
   4. Glucose:
   5. Protein:
2. Which diseases, if any, may be indicated by the results for Unknown A, B, C, and D? Explain.
3. When using a microscope to examine the urine samples, what types of cells might you see and why?

Lab Activity 9.5: Fetal Pig Dissection (Optional)

Supplies needed: gloves, scalpel/scissors, blunt probe, tweezers. Use human terminology wherever terms for the pig may differ.

1. To begin, locate the two kidneys in the abdominal cavity. Find the adrenal (suprarenal) glands: small, white bands of tissue on the top, inside edge of each kidney. Be aware that the peritoneum holds the adrenal gland against the kidney. You may have removed the peritoneum during previous dissections and the adrenals will no longer be resting on the kidney; but will instead be near the spinal column. Also, while there are left and right adrenal glands, the left adrenal may be missing due to the removal of tissue during the dissections earlier in the semester.
2. Observe and trace the ureters from their origin at the hilum of each kidney. These are the bilateral tubes that go from each kidney to the urinary bladder. The bladder is the muscular structure located between the two umbilical arteries. Remember that the bladder is not filled with urine in your pig, so it does not have the shape you may be expecting.
3. Locate the urethra coming off the base of the bladder. You will get a much better view of the urethra after you have completed the dissection of the reproductive systems. Note that the female urethra is short while the male urethra is much longer.

Clean up procedure:

• Dispose of all organic debris in the appropriate biohazard containers and clean the dissecting instruments and tray with soap and water before leaving the laboratory. Do not forget to wash your hands with water and soap, and to disinfect the lab bench.

Post-Lab 9 Review

Post-Lab Activity 9.1: Review Questions

1. What is the function of the renal capsule?
2. Which structure is continuous with the renal pelvis that transports waste from the kidneys to the bladder?
3. What is the structural importance of the renal hilum?
4. What is the difference between calyces and papillae?
5. Where in the kidneys are nephrons present?
6. What are the two parts of a nephron?

Post-Lab Activity 9.2: Fill in the Table for the Internal Kidney Structures

Figure 9.10 Label the Major Structures of the Kidney

Post-Lab Activity 9.3: Label Structures Associated with Blood Flow in the Nephron

Figure 9.11 Label the Major Structures of the Nephron

A

B

C

D

E

F

G

H

I

Post-Lab Activity 9.4: Urinalysis

1. What urinalysis results would you expect for someone being treated for a bacterial infection?
   1. Color:
   2. pH:
   3. Specific gravity:
   4. Glucose:
   5. Protein:
2. What urinalysis results would you expect for someone being treated for diabetes mellitus?
   1. Color:
   2. pH:
   3. Specific gravity:
   4. Glucose:
   5. Protein:

Post-Lab Activity 9.5: Label the Kidney

Figure 9.12 Kidney Dissection Photograph by Heather Cathcart. Figure shows a kidney cut equally into two halves, with structures labeled A-K.

Identify the following structures on the kidney image:

Post-Lab Activity 9.6: Histology

1. Identify the epithelial tissue on the image of the contracted bladder.

• What type of epithelium is found in the bladder?

Figure 9.13 Histology of the contracted bladder.

2. In the image, identify the Bowman’s capsule.

• What structure is located within this capsule?

Figure 9.14: Histology of the kidney. Photograph by Gina Profetto.