Urinary System: Part Two

Question 1

Early Filtrate Processing
Tubular Reabsorption

Describe:

Answer 1

A transepithelial process whereby most tubule content are returned to the blood

Question 2

Early Filtrate Processing
Tubular Reabsorption

Related membranes:

Answer 2

Transported substances move through three membranes:

Luminal membranes of tubule cells
Basolateral membranes of tubule cells
Endothelium of peritubular capillaries

Question 3

Early Filtrate Processing
Sodium Reabsorption- Primary Active Transport

Describe:

Answer 3

Na+ ions are the most abundant ion in filtrate; sodium reabsorption is almost always by active transport

Question 4

Early Filtrate Processing
Sodium Reabsorption- Primary Active Transport

Active transport process

Describe:

Answer 4

Sodium reabsorption is almost always by active transport:

Actively transported out of tubules by a Na+/K+ ATP pump

Na+ passively enters the tubule cells at the luminal membrane (PCT)

From there is moves to the peritubular capillaries due to low hydrostatic pressure and high osmatic pressure of the blood

Question 5

Early Filtrate Processing
Reabsorption by PCT Cells

Describe:

Answer 5

Active pumping of Na+ drives reabsorption of:

Water by osmosis, aided by water-filled pores called aquaporins

Cations and fat soluble substances by diffusion

Organic nutrients and selected cations by secondary active transport

Question 6

Early Filtrate Processing
Reabsorbed Substances

Transport Maximum

Describe:

Answer 6

Reflects the number of carriers in the renal tubules available

Exists for nearly every substance that is actively absorbed

When the carriers are saturated, excess of that substance is excreted

Question 7

Early Filtrate Processing
Reabsorbed Substances

Substances are not reabsorbed…

Describe:

Answer 7

Substances are not reabsorbed if they…

Lack carriers

Are not lipid soluble

Are too large to pass through the membrane pores

Question 8

Early Filtrate Processing
Reabsorbed Substances

Key Non-reabsorbed Substances

Describe:

Answer 8

Creatine and uric acid (not the same as urea) are the most important non-reabsorbed substances

Question 9

Secondary Active Transport

Describe:

Answer 9

No direct coupling of ATP

Instead the electrochemical potential difference created by pumping Na+ ions out of the cells

Three main forms of this are uniport, counter-transport (antiport), and co-transport (symport)

Question 10

Early Filtrate Processing
Absorptive Capabilities of Renal Tubules and Collecting Ducts

Substances Reabsorbed in PCT Include

Describe:

Answer 10

Sodium, all nutrients, cations, anions, and water

Urea and lipid soluble solutes

Small proteins

Question 11

Early Filtrate Processing
Absorptive Capabilities of Renal Tubules and Collecting Ducts

Loop of Henle Reabsorbs

Describe:

Answer 11

H2O in the descending limb (but not solutes)

Solutes in the ascending limb (but not H2O)

Question 12

Early Filtrate Processing
Absorptive Capabilities of Renal Tubules and Collecting Ducts

DCT (Distal Convoluted Tubule) Reabsorbs

Describe:

Answer 12

Ca, Na, H, K, and water

Question 13

Early Filtrate Processing
Absorptive Capabilities of Renal Tubules and Collecting Ducts

Collecting Duct Reabsorbs

Describe:

Answer 13

Water, urea, and sodium

Question 14

Early Filtrate Processing
Na+ Entry into Tubule Cells

Passive Entry

Describe:

Answer 14

Na+ down concentration gradient

Question 15

Early Filtrate Processing
Na+ Entry into Tubule Cells

In the PCT (Proximal Convoluted Tubule)

Describe:

Answer 15

Facilitated diffusion using symport and antiport carriers

Question 16

Early Filtrate Processing
Na+ Entry into Tubule Cells

Ascending Loop of Henle

Describe:

Answer 16

Facilitated diffusion via Na+ K+ and 2Cl- symport system

Question 17

Early Filtrate Processing
Na+ Entry into Tubule Cells

In the DCT (Distal Convoluted Tubule)

Describe:

Answer 17

Na+ Cl- symporter

Question 18

Early Filtrate Processing
Na+ Entry into Tubule Cells

In the collecting tubules

Describe:

Answer 18

Diffusion through the membrane pores

Question 19

Early Filtrate Processing
Atrial Natriuretic Peptide Activity

ANP reduces blood Na+ which…

Describe:

Answer 19

ANP reduces blood Na+ which:

Decreases blood volume
Lowers blood pressure

Question 20

Early Filtrate Processing
Atrial Natriuretic Peptide Activity

ANP lowers blood Na+ by…

Describe:

Answer 20

ANP lowers blood Na+ by:

Acting directly on medullary ducts to inhibit Na+ reabsorption

Counteracting the effects of angiotensin II

Indirectly stimulating an increase in GFR reducing water reabsorption

Question 21

Early Filtrate Processing
Tubular Secretion

Describe:

Answer 21

Essentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells back into filtrate

Question 22

Early Filtrate Processing
Tubular Secretion

Tubular secretion is important for…

Describe:

Answer 22

Tubular secretion is important for:

Disposing of substances not already in the filtrate

Eliminating undesirable substances such as urea and uric acid

Ridding the body of excess potassium ions

Controlling blood pH

Question 23

Early Filtrate Processing
Regulation of Urine Concentration and Volume

Osmolarity

Describe:

Answer 23

Measure of the osmoles of solute per liter of solution. Reflects the solution’s ability to cause osmosis

Typically number of solute particles dissolved in 1L of water

Question 24

Early Filtrate Processing
Regulation of Urine Concentration and Volume

Osmolality

Describe:

Answer 24

Measure of osmoles of solute per kilogram of solvent . If the concentration is very low, osmolarity and osmolality are considered equivalent

Question 25

Early Filtrate Processing Countercurrent Mechanism Describe:

Answer 25

Medullary osmotic gradient is created by the loops of Henle in the juxtamedullary nephrons. Dissipation of the medullary osmotic gradient is prevented because the blood in the vasa recta equilibrates with the interstitial fluid

Question 26

Early Filtrate Processing Loop of Henle: Countercurrent Multiplier The descending loop of Henle Describe:

Answer 26

Is relatively impermeable to solutes Is permeable to water

Question 27

Early Filtrate Processing Loop of Henle: Countercurrent Multiplier The ascending loop of Henle Describe:

Answer 27

Is permeable to solutes Is impermeable to water

Question 28

Late Filtrate Processing Formation of Dilute Urine (Closed State) Describe:

Answer 28

Filtrate is diluted in the ascending Loop of Henle. Dilute Urine is created by allowing this filtrate to continue into the renal pelvis. Collecting ducts remain impermeable to water; no further water reabsorption occurs. Sodium and select ions can be removed by active and passive mecahisms.

Question 29

Late Filtrate Processing Formation of Concentrated Urine (Duct has Opened Up) Describe:

Answer 29

Antidiuretic hormone (ADH) inhibits diuresis. This equalizes the osmolarity of the filtrate and interstitial fluid. In the presence of ADH, 99% of the water in the filtrate is reabsorbed. The kidney's ability to respond depends on the high medullary osmotic gradient. ADH increases the permeability of the collecting duct and water is reabsorbed and urine is concentrated.

Question 30

Late Filtrate Processing Diuretics Describe:

Answer 30

Chemicals that enhance the urinary output. These include: Any substances not reabsorbed Substances that exceed the ability of the renal tubules to reabsorb it. Substances that inhibit Na+ reabsorption

Question 31

Late Filtrate Processing Diuretics Osmotic Diuretics Describe:

Answer 31

High glucose levels- carries water out with glucose. Alcohol- inhibits the release of ADH. Caffeine and most diuretic drugs- inhibits sodium ion reabsorption.

Question 32

Late Filtrate Processing Dehydration Describe:

Answer 32

Lack of adequate body fluids needed for the body to carry on normal functions at an optimal level. Caused by fluid loss, inadequate intake, or a combination of both

Question 33

Late Filtrate Processing Dehydration Mild Describe:

Answer 33

Thirst Dry lips Slightly dry mouth membranes

Question 34

Late Filtrate Processing Dehydration Moderate Describe:

Answer 34

Very dry mouth membranes Sunken eyes Sunken fontanel on infant's head Skin doesn't bounce back quickly when lightly pinched or released (more chronic than acute)

Question 35

Late Filtrate Processing Dehydration Severe Describe:

Answer 35

``` All signs of moderate dehydration Rapid, weak pulse (more than 100 at rest) Cold hands and feet Rapid breathing Blue lips Confusion, lethargy, difficult to arouse ```

Question 36

Late Filtrate Processing Hyponatremia Describe:

Answer 36

Plasma Na+ levels too low (i.e. from water intoxication) Usually caused by high ADH levels; requires treatment with intravenous isotonic/hypertonic saline.

Question 37

Late Filtrate Processing Renal Clearance Describe:

Answer 37

The volume of plasma that is cleared of a particular substance in a given time

Question 38

Late Filtrate Processing Renal Clearance Importance Describe:

Answer 38

Used to determine GFR (Glomerular Filtration Rate), detect glomerular damage, and follow-up on the progress of diagnosed renal disease

Question 39

Late Filtrate Processing Renal Clearance Equation Describe:

Answer 39

RC = UV / P RC = Renal Clearance U= Concentration (mg/ml) of the substance in urine V = Flow rate of urine formation (ml/min) P = Concentration of the same substance of plasma

Question 40

Late Filtrate Processing Creatinine Clearance Equation Describe:

Answer 40

RCcr = Ucr * V / Pcr Relatively constant level in the blood, freely filtered but neither reabsorbed nor secreted by the kidneys

Question 41

Late Filtrate Processing Renal Clearance Normal GFR Range Describe:

Answer 41

Males: 97 to 137 ml/min Females: 88 to 128 ml/min

Question 42

Late Filtrate Processing Physical Characteristics of Urine Color and Transparency Describe:

Answer 42

Clear, pale to deep yellow; concentrated urine has a deeper yellow color

Question 43

Late Filtrate Processing Physical Characteristics of Urine Odor Describe:

Answer 43

Fresh urine is slightly aromatic; standing urine develops an ammonia odor

Question 44

Late Filtrate Processing Physical Characteristics of Urine pH Describe:

Answer 44

Slightly acidic (pH 6) with a range of 4.0 to 8.0

Question 45

Late Filtrate Processing Physical Characteristics of Urine Specific Gravity Describe:

Answer 45

Ranges from 1.001 to 1.035. It is dependent on the solute concentration.

Question 46

Late Filtrate Processing Chemical Composition of Urine Describe:

Answer 46

Urine is 95% water and 5% solutes Nitrogenous wastes include urea, uric acid, and creatinine Other normal solutes include sodium, potassium, phosphate, and sulfate ions, calcium, magnesium, and bicarbonate ions

Question 47

Late Filtrate Processing Urinalysis Describe:

Answer 47

A description of color and appearance

Question 48

Late Filtrate Processing Urinalysis pH Describe:

Answer 48

Reflects blood plasma pH

Question 49

Late Filtrate Processing Urinalysis Glucose Describe:

Answer 49

DM (Diabetes Meticulitis)

Question 50

Late Filtrate Processing Urinalysis Ketones Describe:

Answer 50

Up in starvation, DM, and alcoholics

Question 51

Late Filtrate Processing Urinalysis Protein Describe:

Answer 51

Up in kidney disease

Question 52

Late Filtrate Processing Urinalysis RBC # Describe:

Answer 52

Hematuria

Question 53

Late Filtrate Processing Urinalysis WBC * Describe:

Answer 53

Infection

Question 54

Late Filtrate Processing Urinalysis hCG (Human Chorionic Gonadotropin) Describe:

Answer 54

Pregnancy hormone

Question 55

Late Filtrate Processing Urinalysis Specific Gravity Describe:

Answer 55

Amount of solute per solvent Comparing the density of the liquid to water High specific gravity means dehydration; low specific gravity means kidney disease, absent ADH, water intoxication

Question 56

Late Filtrate Processing Ureters Describe:

Answer 56

Slender tubes that convey urine from the kidneys to the bladder Ureters enter the base of the bladder through the posterior wall Ureters actively propel urine to the bladder via response to smooth muscle stretch (distension)

Question 57

Late Filtrate Processing Ureters Tri-layerd wall Describe:

Answer 57

Ureters have a tri-layered wall: transitional epithelial mucosa, smooth muscle muscularis, fibrous connective tissue adventitia

Question 58

Late Filtrate Processing Urinary Bladder Describe:

Answer 58

Is it smooth, collapsable, muscular sac that temporarily stores urine It is distensible and collapses when empty, forming rugae As urine accumulates, the bladder expands without significant rise in internal pressuure

Question 59

Late Filtrate Processing Urinary Bladder Trigone Describe:

Answer 59

Triangular area outlined by the openings for the ureters and the urethra Clinically important because infections tend to persist in this region

Question 60

Late Filtrate Processing Urinary Bladder Tri-layered bladder wall Describe:

Answer 60

A transitional epithelial mucosa A thick muscular layer (detrusor muscle) A fibrous adventitia

Question 61

Late Filtrate Processing Urethra Describe:

Answer 61

A muscular tube that drains urine from the bladder and conveys it out of the body

Question 62

Late Filtrate Processing Urethra Sphincters and the urethra... Describe:

Answer 62

Sphincters keep the urethra closed when urine is not being passed: Internal urethra sphincter- involuntary sphincter at the bladder-urethra junction External urethral sphincter- voluntary sphincter surrounding the urethra as it passes through the urogenital diaphragm Levator ani muscle- voluntary urethral sphincter

Question 63

Late Filtrate Processing Urethra Female Urethra Describe:

Answer 63

The female urethra is tightly bound tot he anterior vaginal wall and has an external opening that lies anterior to the vaginal opening and posterior to the clitoris

Question 64

Late Filtrate Processing Urethra Male Urethra Describe:

Answer 64

The male urethra has three named regions: Prostatic urethra- runs with the prostate gland Membranous urethra- runs through the urogenital diaphragm Spongy (penile) urethra- passes through the penis and opens via the external urethral orifice

Question 65

Late Filtrate Processing Micturation (Voiding or Urination) Describe:

Answer 65

The act of emptying the bladder. Distension of the bladder walls (at approximately 220ml) initiates spinal reflexes that stimulate contraction of the external urethral sphincter and inhibit the detrusor muscle and internal sphincter

Question 66

Late Filtrate Processing Selected Pathology - Renal Calculi Kidney Stones Describe:

Answer 66

Most pass without concerns Crystals of normally dissolved minerals (m/c = calcium oxalate CaC2O4)

Question 67

Late Filtrate Processing Selected Pathology - Renal Calculi Kidney Stones - Risk Factors Describe:

Answer 67

Low water intake, high protein diet, high vitamin C intake, high Ca2 supplementation Coffee intake is protective