21  Urinary System

Figure 21.1 The female urinary system.

In this laboratory, you will use models and diagrams to study the anatomy of the urinary system. Specifically, you will examine the gross and microscopic anatomy of the human urinary system.

21.1 Learning Objectives for this lab:

By the end of this lab, you will be able to:

• Describe the function of the male and female urinary systems.

• Identify the organs of the urinary system on a model or a diagram and describe the function of each.

• To identify the following on a dissected kidney:

  • Hilum
  • Cortex
  • Medulla
  • Medullary pyramids

• Major and minor calyces

• Pelvis

• Renal columns

• Renal capsule

• Trace the blood supply of the kidney from the renal artery to the renal vein.

• Describe the anatomy of a nephron.

• Identify and describe the anatomical features of the nephron. These should include:

  • Glomerulus
  • Glomerular capsule
  • Renal tubule

• Proximal convoluted tubule

• Nephron loop

• Distal convoluted tubule

• To compare the course and length of the urethra in the male and female urinary systems.

• Identify the following structures of importance found in the lists below:

21.2 Terms to Learn:

21.3 Kidney Structures

• Renal capsule

• Renal cortex

• Renal columns

• Renal medulla

• Renal pyramids

• Renal papillae

• Hilum

• Renal sinus

• Minor calyces

• Major calyces

• Renal pelvis

21.4 Nephron

• Renal corpuscle

• Afferent arteriole

• Efferent arteriole

• Glomerulus

• Glomerular (Bowman’s) capsule

• Proximal convoluted tubule

• Nephron loop (loop of Henle)

  • Descending limb
  • Ascending limb

• Distal convoluted tubule

• Collecting duct

• Papillary duct

21.4.1 Blood Flow

• Renal artery

• Segmental artery

• Interlobar artery

• Arcuate artery

• Cortical radiate (interlobular) artery

• Afferent arteriole

• Glomerulus

• Efferent arteriole

• Peritubular capillaries

• Vasa recta

• Cortical radiate (interlobular) vein

• Arcuate vein

• Interlobar vein

• Renal vein

21.5 Storage and Elimination

• Ureter
• Urinary bladder
  • Detrusor muscle
  • Trigone
• Urethra
• Transitional epithelium

21.6 Prelab Activities

21.7 Prelab Activity 21.1

• Kidney _______________________________________________________
• Ureter ________________________________________________________
• Bladder ______________________________________________________
• Detrusor muscle _______________________________________________
• Trigone ______________________________________________________
• Urethra _______________________________________________________

21.8 Kidney Structures

• Renal capsule _________________________________________________
• Renal cortex __________________________________________________
• Renal columns ________________________________________________
• Renal medulla _________________________________________________
• Renal pyramids ________________________________________________
• Renal papillae _________________________________________________
• Hilum ________________________________________________________
• Renal sinus ___________________________________________________
• Minor calyces __________________________________________________
• Major calyces __________________________________________________
• Renal pelvis ___________________________________________________

21.9 Prelab Activity 21.2

Complete table 21.1 by identifying the structures in figure 21.2.

Figure 21.2 Unlabeled kidney.

21.10 Word bank: Kidney

• Renal pyramid

• Interlobular artery

• Renal artery

• Renal vein

• Renal hilum

• Renal pelvis

• Ureter

• Minor calyx

• Renal capsule

• Inferior extremity

• Superior extremity

• Interlobar vein

• Nephron

• Renal sinus

• Major calyx

• Renal papilla

• Renal column

Table 21.1 Identification of the Structures in the Kidney

Number	Identification
1
2
3
4
5
6
7
8
9
10
11

21.11 Prelab Activity 21.3

Using your text or the information in this workbook, label the diagram of the nephron below.

Figure 21.3 Nephron Anatomy.

21.12 Lab Activities

21.13 Introduction to the kidney

Figure 21.4 Structures of the Kidney..

21.13.1 Structures of the Kidney Word Bank:

• Renal pyramid

• Interlobular artery

• Renal artery

• Renal vein

• Renal hilum

• Renal pelvis

• Ureter

• Minor calyx

• Renal capsule

• Inferior extremity

• Superior extremity

• Interlobar vein

• Nephron

• Renal sinus

• Major calyx

• Renal papilla

• Renal column

21.14 Lab Activity 21.1

Gather in your assigned groups. Obtain a free-standing 3d model of the urinary system of the male.

• Identify and label the structures listed below. Palpate the models as you identify the structures to assist in your learning the kidney structures.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.

21.15 Urinary system

• Kidney

• Ureter

• Bladder

• Urethra

Figure 21.5 The Male Urinary System.

21.15.1 Lab Activity 21.2:

Obtain a 3d model of the microanatomy of the kidney, a human kidney section and a free-standing kidney model.

• Identify and label the structures listed below. Palpate the models as you identify the structures to assist in your learning the kidney structures.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.
• If you have time create a 5ive-minute video reviewing the structures of the kidney.

21.16 Kidney Structure

• Renal capsule

• Renal cortex

• Renal columns

• Renal medulla

• Renal pyramids

• Renal papillae

• Hilum

• Renal sinus

• Minor calyces

• Major calyces

• Renal pelvis

Figure 21.6 The Kidney.

21.16.1 Lab Activity 21.3

Obtain a 3d model of human kidney model with nephrons, blood vessels and renal corpuscle and/or the microanatomy kidney model.

• Identify and label the structures listed below. Palpate the models as you identify the structures to assist in your learning the kidney structures.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.
• If you have time create a 5ive-minute video reviewing the structures of the kidney.

21.17 Nephron

• Renal corpuscle

• Afferent arteriole

• Efferent arteriole

• Glomerulus

• Glomerular (Bowman’s) capsule

• Proximal convoluted tubule

• Nephron loop (loop of Henle)

  • Descending limb
  • Ascending limb

• Distal convoluted tubule

• Collecting duct

• Papillary duct

Figure 21.7 The Nephron.

21.17.1 Lab Activity 21.4:

Obtain a 3d model of human kidney model with nephrons, blood vessels and renal corpuscle and/or the microanatomy kidney model.

• Identify and label the structures listed below.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.

21.17.2 Blood Flow

• Renal artery

• Segmental artery

• Interlobar artery

• Arcuate artery

• Interlobular (Cortical radiate) artery

• Afferent arteriole

• Glomerulus

• Efferent arteriole

• Peritubular capillaries

• Vasa recta

• Interlobular (Cortical radiate) vein

• Arcuate vein

• Interlobar vein

• Renal vein

Figure 21.8 Blood Flow in the Kidney.

21.18 Lab Activity 21.5:

Obtain a free-standing 3d model of the urinary system of the male and/or a dual sex urinary system model.

• Identify and label the structures listed below. Palpate the models as you identify the structures to assist in your learning the kidney structures.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.

21.19 Storage and Elimination

21.20 Terms

• Ureter
• Urinary bladder
  • Detrusor muscle
  • Trigone
• Urethra
• Transitional epithelium

Figure 21.9 The Male and Female Urinary Tracts.

21.21 Lab Activity 21.6 (Optional)

• Under the direction of your instructor, obtain a microscope from the storage cabinet.
• Locate obtain a slide of the transitional epithelium of the bladder.
• Focus on the slide using the 400 x magnification.
• Have the group next to you review your identifications for their correctness.
• Take pictures of your finished work for review later on.

Figure 21.10 Transitional Epithelium Found in the Bladder.

21.22 Lab Activity 21.7: Urinalysis

Performing a urinalysis

In this procedure you will test simulated urine from several patients.

1. Obtain five test tubes. Place the test tubes in a test tube rack and label the test tubes for patient A, B. C, D, and E.
2. Fill each test tube with the following simulated solutions: one filled with simulated urine from patient A, B, C, D, and E. label each test tube
3. Visually determine the color and transparency of each patient’s sample. Record your observations in table ____. Determine whether the sample is clear or cloudy.

Figure 21.11 Color Results of the Relative Amount of Dehydration in a Urine Sample.

4. Obtain a urinalysis test strip.

Figure 21.12 A Medical Illustration Depicting a Ketone Urine Test.

5. Dip the quickly into the urine sample for patient A. Make sure that the entire strip is immersed into the solution, covering all of the test pads.

Figure 21.13 A Urine Test Strip is Immersed into the Sample.

6. Place Patient A’s test strip[ on a paper towel marked “A.” Set the strip on its side and gently tap the strip to remove any excess fluid.
7. Allow the strip to dry for 30 seconds.
8. Compare the color of the strips to the color of the blocks on the Siemens Healthcare bottle. Record the results in table 21.2.

Figure 21.14 Comparison of a Color Strip to the Label on a Test Strip Container.

Repeat steps 1-8 for the samples from patients B-E

Fill in the following table and answer the following questions:

Table 21.2 Urinalysis Results

Characteristics	Normal	Possible abnormal results pathologies	Patient A	Patient B	Patient C	Patient D	Patient E
Color	Light yellow to amber	Dehydration, liver disease, muscular breakdown
Clarity	Clear	infection
pH	4.6-8	Acidosis, alkalosis
Glucose	Negative	Diabetes mellitus
Ketosis bodies	Negative	Diabetes mellitus
Nitrites	Negative	Urinary tract infection
Protein	Negative - trace	Kidney disease
Blood/hemoglobin	Negative	Trauma, infection, tumor, kidney stones
Specific gravity	1.003- 1.035	Low: excessive fluid intake elevated: dehydration

21.22.1 Questions:

• What conditions might they have?

• Which results may indicate that your patient is taking diuretics?

21.23 Post Lab Activities Check Your Understanding

21.23.1 Post Lab Activity: 21.1

Figure 21.15 The Urinary system.

Identify the structures in figure 21.15.

Table 21.2 Structures of the urinary system

Number	Structure identification
1
2
3
4
5
6
7
8
9
10
11
12
13
14

Identify all of the structures in figure 21.16.

Figure 21.16 Juxtamedullary Nephron.

Match the number or letter in figure 21.16 with the structure listed in the following table.

Table 21.2 Structures of the Nephron.

Number or letter	Structure
	Afferent arteriole
	Arcuate artery
	Arcuate vein.
	Ascending limb of Loop of
	Henle
	Bowman’s capsule
	Collecting duct
	Cortex
	Corticomedullary junction
	Descending limb of Loop of Henle

Number or letter	Structure
	Distal convoluted tubule
	Efferent arteriole
	Glomerulus
	Interlobular vein
	Interlobular artery
	Medulla
	Minor calyx
	Peritubular capillaries
	Proximal convoluted tubule

21.24 Label the structures in Figure 21.17.

Figure 21.17 .The Bladder.

21.25 Post Lab Activity: 21.2

21.26 Answer the following questions

• Trace the path of urine from its point of filtration to its secretion out of the body.

• What is unique about the location of the kidneys in the abdominopelvic cavity?

21.27 Post Lab Activity: 21.3

21.28 Crosswords

Complete the following crossword puzzles:

Figure 21.18 Renal anatomy 1.

21.28.1 Across

3 The medial surface is concave and has a(n) ___ (or ___) where ureters, blood vessels, nerves and lymphatics enter and leave the kidney. (5,5)

4 Blood leaves the glomerulus via the ___ arterioles, which take it to a second capillary bed called the ___ ___. (8,11,11)

6 Each renal pyramid projects into a tube within the renal sinus which conducts urine out from the kidney. The projection itself is called the ___ ___; the tube which it enters is called a(n) ___ ___ (the plural is “___ ___’) (5,7,5,5,5,7)

8 The kidneys are encased in a fibrous layer of connective tissue called the ___ ___. (5,7)

10 The renal cortex surrounds the ___; columns of corticular tissue extend toward the hilum, separating it into distinct regions called ___. (7,5,8)

11 Most of the blood reaching the kidneys flows to the ___ ___, where it is filtered. (5,6)

12 Columns of tissue in the corticular region that extend to the hilum are called the ___. (5,7)

13 Urine is formed by each of two ___. From each, a muscular tube called the ___ propels urine to the ___ where it is stored until its release. Then it flows out of the body through the ___. (7,6,7,7)

21.28.2 Down

1 Many small arteries arise in the cortex and are called the ___ arteries; these supply blood to the ___ arterioles and the ____. (12,8,10)

2 The kidneys are ___ to the peritoneum. Each lies in the ___ ___ region, anterior to the ___ ___, but the right is slightly lower than the left to make room for the ___. (9,5,6,4,3,5)

5 Several minor calyces merge to form a(n) ___. (5,5)

7 Blood flows to the renal cortex through the ___ arteries, then arches around the renal lobes just below the cortex via the ___ arteries. (10,7)

9 Each renal pyramid and the corticular tissue surrounding it is called a(n) ___. The term “___’ refers to these units. (5,4,5)

Figure 21.19 Renal anatomy 2.

Figure 21.19 Renal anatomy 2.

21.28.3 Across

7 In ___ the liquid components of the blood are separated from the formed elements and large molecules. (10)

9 There are three processes involved in urine formation: ___, ___ and ___ (10,10,9)

10 ___ is another word for urination (11)

11 The muscular layer which comprises the bulk of the bladder is the ___ muscle. It consists of ___ muscle fibers arranged in three layers. (8,6)

21.28.4 Down

1 In males, the urethra has three regions: the ___ urethra under the bladder, the ___ ( or ___) urethra within the penis and the ___ urethra which connects them. (9,6,6,10)

2 Blood to the glomerulus is supplied by the _____ arteriole and leaves by the _____ arteriole. (16)

3 Resorption of calcium is controlled by ___ It is not unusual that the resorption of most minerals is controlled by _____. (3,8)

4 When peritubular cells in the kidney become hypoxic, they secrete ___ to stimulate the formation of more oxygen-carrying red blood cells. (14)

5 Calcium resorption is controlled by ___ hormone. (11)

6 At the base of the bladder the two ureter openings and the urethral opening form a triangle; the region of the bladder encompassed by this triangle is called the ___. (7)

8 In females the outer urethral opening is immediately ___ to the vaginal opening. (8)

Figure 21.20 Renal Physiology.

21.28.5 Across

2 The tubular portion of the nephron is divided into several sections both functionally and conceptually; the tube farthest from the renal corpuscle is the ___ _ Its primary function is to resorb ____. (6,10,6,5)

8 Each nephron has two major parts: the ___ ___ in the cortex and a thin ___, u- shaped the center, which extends from the cortex into the medulla and back. (5,9,6)

9 The renal corpuscle has two arts: the central portion is a tangled ball of capillaries called the ___. The surrounding outer portion, a double-walled, cup- like chamber is called the___ ___. (10,7,7)

10 ___ ___ forces liquid to leave the capillaries in the glomerulus, while the formed elements and large molecules remain behind. (5,8)

21.28.6 Down

1 There are two types of nephrons, the glomerulus of ____ nephrons is near the medulla and the tubule of these nephrons travels ___ into the renal pyramid. (14,4)

3 The proximal and distal tubules of the nephron are connected by a hairpin-like loop called the ___ __ ___. Its primary function is to resorb ___ and ___. (4,2,5,5,4)

4 There are two types of nephrons, most are ___ nephrons. Each of these has a glomerulus which is near the outer surface of the cortex. (10)

5 The function of the renal corpuscle is to ___ ___ in the first step of urine formation. (6,5)

6 ___ are structures within the kidney that actually sort the substances which should be kept or discarded. (8)

7 Glomerular capillaries contain many ___ through which liquid can pass. (13)

21.29 Keys

21.30 Crosswords

21.31 Figure 21.18. Renal Anatomy 1

• Across: 3 Hilum hilus, 4 Efferent peritubular capillaries, 6 Renal papilla minor calyx minor calyces, 8 Renal capsule, 10 Medulla renal pyramids, 11 Renal cortex, 12 Renal columns, 13 Kidneys ureter bladder urethra.
• Down: 1 Interlobular afferent glomerulus, 2 Posterior upper lumbar 12th rib liver, 5 Major calyx, 7 Interlobar arcuate, 9 Renal lobe lobar.

21.31.0.1 Figure 21.19. Renal Anatomy 2

• Across: 7 Filtration, 9 Filtration resorption secretion, 10 Micturition, 11 Detrusor smooth.
• Down: 1 Prostatic spongy penile membranous, 2 Afferent efferent, 3 PTH hormones, 4 Erythropoietin, 5 Parathyroid, 6 Trigone, 8 Anterior.

21.31.0.2 Figure 21.20. Renal Physiology

• Across: 2 PTH hormones, 8 Prostatic spongy penile membranous, 9 Filtration resorption secretion, 10 Anterior.
• Down: 1 Juxtamedullary, deep, 3 Loop of Henle, water, salt, 4 Corticular, 5 Filter, blood, 6 Nephrons, 7 Fenestrations,

21.31.1 Figure 21.16 Juxtamedullary Nephron Key:

1. Renal pyramid
2. Interlobular artery
3. Renal artery
4. Renal vein
5. Renal hilum
6. Renal pelvis
7. Ureter
8. Minor calyx
9. Renal capsule
10. Inferior extremity
11. Superior extremity
12. Interlobar vein
13. Nephron
14. Renal sinus
15. Major calyx
16. Renal papilla
17. Renal column

21.31.2 Chapter 21: Urinary System Glossary

Terms	Definitions
Afferent arteriole	an arteriole that feeds blood into the glomerulus in the nephron
anatomical sphincter	smooth or skeletal muscle surrounding the lumen of a vessel or hollow organ that can restrict flow when contracted
angiotensin I	protein produced by the enzymatic action of renin on angiotensinogen; inactive precursor of angiotensin II
angiotensin II	protein produced by the enzymatic action of ACE on inactive angiotensin I; actively causes vasoconstriction and stimulates aldosterone release by the adrenal cortex
Arcuate vein	a vessel of the renal circulation located at the border of the renal cortex and renal medulla
angiotensin- converting enzyme (ACE)	enzyme produced by the lungs that catalyzes the reaction of inactive angiotensin I into active angiotensin II
angiotensinogen	inactive protein in the circulation produced by the liver; precursor of angiotensin I; must be modified by the enzymes renin and ACE to be activated
anuria	absence of urine produced; production of 50 mL or less per day
aquaporin	protein-forming water channels through the lipid bilayer of the cell; allows water to cross; activation in the collecting ducts is under the control of ADH
Bowman’s capsule (glomerular capsule)	cup-shaped sack lined by a simple squamous epithelium (parietal surface) and specialized cells called podocytes (visceral surface) that participate in the filtration process; receives the filtrate which then passes on to the PCTs
brush border	formed by microvilli on the surface of certain cuboidal cells; in the kidney it is found in the PCT; increases surface area for absorption in the kidney
calyces	cup-like structures receiving urine from the collecting ducts where it passes on to the renal pelvis and ureter
cortical nephrons	nephrons with loops of Henle that do not extend into the renal medulla
Corticular radiate vein (interlobar vein)	veins of the renal circulation which drain the renal lobes.
countercurrent	multiplier system involves the descending and ascending loops of Henle directing forming urine in opposing directions to create a concentration gradient when combined with variable permeability and sodium pumping
detrusor muscle	smooth muscle in the bladder wall; fibers run in all directions to reduce the size of the organ when emptying it of urine
distal convoluted tubules	portions of the nephron distal to the loop of Henle that receive hypoosmotic filtrate from the loop of Henle and empty into collecting ducts
diuretic	compound that increases urine output, leading to decreased water conservation
efferent arteriole	arteriole carrying blood from the glomerulus to the capillary beds around the convoluted tubules and loop of Henle; portion of the portal system
endothelins	group of vasoconstrictive, 21-amino acid peptides; produced by endothelial cells of the renal blood vessels, mesangial cells, and cells of the DCT
external urinary sphincter	skeletal muscle; must be relaxed consciously to void urine
fenestrations	small windows through a cell, allowing rapid filtration based on size; formed in such a way as to allow substances to cross through a cell without mixing with cell contents
filtration slits	formed by pedicels of podocytes; substances filter between the pedicels based on size
forming urine	filtrate undergoing modifications through secretion and reabsorption before true urine is produced
glomerular filtration rate (GFR)	rate of renal filtration
glomerulus	tuft of capillaries surrounded by Bowman’s capsule; filters the blood based on size
glycosuria	presence of glucose in the urine; caused by high blood glucose levels that exceed the ability of the kidneys to reabsorb the glucose; usually the result of untreated or poorly controlled diabetes mellitus
hilum	a depression or fissure in an organ where structures such as blood vessels and nerves enter or exit
incontinence	loss of ability to control micturition
intercalated cell	specialized cell of the collecting ducts that secrete or absorb acid or bicarbonate; important in acid-base balance
Interlobar vein	See corticular radiate vein
internal urinary sphincter	smooth muscle at the juncture of the bladder and urethra; relaxes as the bladder fills to allow urine into the urethra
inulin	plant polysaccharide injected to determine GFR; is neither secreted nor absorbed by the kidney, so its appearance in the urine is directly proportional to its filtration rate
juxtaglomerular apparatus (JGA)	located at the juncture of the DCT and the afferent and efferent arterioles of the glomerulus; plays a role in the regulation of renal blood flow and GFR
juxtaglomerular cell	modified smooth muscle cells of the afferent arteriole; secretes renin in response to a drop in blood pressure
juxtamedullary nephrons	nephrons adjacent to the border of the cortex and medulla with loops of Henle that extend into the renal medulla
leaky tight junctions	tight junctions in which the sealing strands of proteins between the membranes of adjacent cells are fewer in number and incomplete; allows limited intercellular movement of solvent and solutes
leukocyte esterase	enzyme produced by leukocytes that can be detected in the urine and that serves as an indirect indicator of urinary tract infection
loop of Henle	descending and ascending portions between the proximal and distal convoluted tubules; those of cortical nephrons do not extend into the medulla, whereas those of juxtamedullary nephrons do extend into the medulla
macula densa	cells found in the part of the DCT forming the JGA; sense Na+ concentration in the forming urine
Major calyces	a larger funnel-shaped structure in the kidney that receives urine from two or more minor calyces.
medulla (renal medulla)	inner region of kidney containing the renal pyramids
mesangial contractile cells	cells found in the glomerulus; can contract or relax to regulate filtration rate
micturition	urination or voiding
minor calyces	minor calyces form a cup-shaped drain around the apex of the renal pyramids.
myogenic mechanism	mechanism by which smooth muscle responds to stretch by contracting; an increase in blood pressure causes vasoconstriction and a decrease in blood pressure causes vasodilation so that blood flow downstream remains steady
nephrons	functional units of the kidney that carry out all filtration and modification to produce urine; consist of renal corpuscles, proximal and distal convoluted tubules, and descending and ascending loops of Henle; drain into collecting ducts
net filtration pressure (NFP)	Pressure of fluid across the glomerulus; calculated by taking the hydrostatic pressure of the capillary and subtracting the colloid osmotic pressure of the blood and the hydrostatic pressure of Bowman’s capsule
oliguria	below normal urine production of 400-500 mL/day
osteomalacia	softening of bones due to a lack of mineralization with calcium and phosphate; most often due to lack of vitamin D; in children, osteomalacia is termed rickets; not to be confused with osteoporosis
pedicels	finger-like projections of podocytes surrounding glomerular capillaries; interdigitate to form a filtration membrane
peritubular capillaries	second capillary bed of the renal portal system; surround the proximal and distal convoluted tubules; associated with the vasa recta
physiological sphincter	sphincter consisting of circular smooth muscle indistinguishable from adjacent muscle but possessing differential innervations, permitting its function as a sphincter; structurally weak
podocytes	cells forming finger-like processes; form the visceral layer of Bowman’s capsule; pedicels of the podocytes interdigitate to form a filtration membrane
polyuria	urine production in excess of 2.5 L/day; may be caused by diabetes insipidus, diabetes mellitus, or excessive use of diuretics
principal cell	cell found in collecting ducts and possess channels for the recovery or loss of sodium and potassium; under the control of aldosterone; also have aquaporin channels under ADH control to regulate recovery of water
proximal convoluted tubules (PCTs)	tortuous tubules receiving filtrate from Bowman’s capsule; most active part of the nephron in reabsorption and secretion
renal columns	extensions of the renal cortex into the renal medulla; separates the renal pyramids; contains blood vessels and connective tissues
renal corpuscle	consists of the glomerulus and Bowman’s capsule
renal cortex	outer part of kidney containing all of the nephrons; some nephrons have loops of Henle extending into the medulla
renal fat pad	adipose tissue between the renal fascia and the renal capsule that provides protective cushioning to the kidney
renal hilum	recessed medial area of the kidney through which the renal artery, renal vein, ureters, lymphatics, and nerves pass
renal papillae	medullary area of the renal pyramids where collecting ducts empty urine into the minor calyces
Renal pelvis
renal pyramids	six to eight cone-shaped tissues in the medulla of the kidney containing collecting ducts and the loops of Henle of juxtamedullary nephrons
Renal vein	large-caliber veins that drain blood filtered by the kidneys into the inferior vena cava.
renin	enzyme produced by juxtaglomerular cells in response to decreased blood pressure or sympathetic nervous activity; catalyzes the conversion of angiotensinogen into angiotensin I
retroperitoneal	behind the peritoneum; in the case of the kidney and ureters, between the parietal peritoneum and the abdominal wall
sacral micturition center	group of neurons in the sacral region of the spinal cord that controls urination; acts reflexively unless its action is modified by higher brain centers to allow voluntary urination
specific gravity	weight of a liquid compared to pure water, which has a specific gravity of 1.0; any solute added to water will increase its specific gravity
systemic edema	increased fluid retention in the interstitial spaces and cells of the body; can be seen as swelling over large areas of the body, particularly the lower extremities
Transitional epithelium	a type of stratified epithelium. Transitional epithelium is a type of tissue that changes shape in response to stretching.
trigone	area at the base of the bladder marked by the two ureters in the posterior-lateral aspect and the urethral orifice in the anterior aspect oriented like points on a triangle
tubuloglomerular feedback	feedback mechanism involving the JGA; macula densa cells monitor Na+ concentration in the terminal portion of the ascending loop of Henle and act to cause vasoconstriction or vasodilation of afferent and efferent arterioles to alter GFR
ureter	The long, narrow duct that conveys urine from the kidney to the urinary bladder
urethra	transports urine from the bladder to the outside environment
Urinary bladder	An elastic, muscular sac situated in the anterior part of the pelvic cavity in which urine collects before excretion
urinalysis	analysis of urine to diagnose disease
urochrome	heme-derived pigment that imparts the typical yellow color of urine
vasa recta	branches of the efferent arterioles that parallel the course of the loops of Henle and are continuous with the peritubular capillaries; with the glomerulus, form a portal system