Urinary System

Urinary System

I. Urinary System Functions:

A.__________________________________________________
B.__________________________________________________
C.__________________________________________________
D.__________________________________________________

II. Organization of the Urinary System (See Interactive Physiology Urinary System: Anatomy Review)

A. Blood Supply to the Kidneys (see p. 5)

1. Renal artery
2. Interlobar arteries
3. Arcuate (arciform) arteries
4. Interlobular arteries
5. Afferent arteriole
6. Glomerulus
7. Efferent arteriole 8. Peritubular capillaries
9. Vasa Recta
10. Interlobular veins
11. Arcuate veins
12. Interlobar veins
13. Renal vein

B. The Kidneys: Superficial and Sectional Anatomy

1. Renal hilus
2. Renal artery and vein
3. Ureter
4. Renal cortex
5. Renal columns
6. Nephrons (cortical and juxtamedullary)

7. Renal medulla
8. Renal pyramids
9. Renal papillae
10. Renal pelvis
11. Major calyces (sing. = calyx) 2 - 3
12. Minor calyces (8 - 14)

C. The Nephron = functional unit of the kidney (see Anatomy Review: p. 7)

1. Renal corpuscle

a. Glomerulus (Q: From which blood vessel is this capillary formed?)

b. Bowman’s (glomerular) capsule (Anatomy Review: p. 10)

1. Visceral layer (Q: What are:

Fenestrations,
Podocytes,
Filtration slits

2. Parietal layer

3. Capsular (urinary) space

2. Renal Tubules

a. Proximal convoluted tubule (PCT) (note microvilli or brush border)
b. Descending limb of loop of Henle (note permeability to water)
c. Ascending limb of loop of Henle (note permeability to NaCl, impermeable to water)
d. Distal convoluted tubule (DCT) (note H+ movement and hormonal regulation controls this segment of the renal tubule)
e. Collecting duct (note: water permeability regulated by ADH)

3. Juxtaglomerular Apparatus (see Anatomy Review: p. 16)

a. Macula densa - responds to osmolarity (Na+) changes
b. Juxtaglomerular (JG) cells - baroreceptors that release the enzyme renin

II. Renal Physiology

A. Metabolic Waste Products Comprising Urine

1. Urea
2. Creatinine
3. Uric Acid

B. Process of Urine Formation (3 Steps) (see Interactive Physiology Urinary System: Glomerular Filtration)

1. Glomerular Filtration Q: How is making coffee analogous to kidney filtration?

a. Description of the filtration membrane (see Glomerular Filtration: p. 5)

b. Forces Affecting Filtration

1. Filtration Pressure = Glomerular Hydrostatic Pressure (GHP)

2. Opposing forces

a. Glomerular Osmotic Pressure (GOP; remember BOP from Cardiovascular?)
b. Capsular Hydrostatic Pressure (CHP)

c. Net filtration pressure (NFP) = GHP - [GOP + CHP]

d. Filtered substances (what becomes part of the "filtrate"; (see Glomerular Filtration: p. 6):

1. H₂O
2. Ions: Name 3: ____________________________
3. Nitrogenous wastes: Name 3: __________________________________________
4. Organic molecules: Name 2:____________________________________

Q: The concentration of the above substances in the filtrate is similar to their concentrations in the _______________.

e. Substances NOT filtered (remain in the blood):

1. Plasma proteins
2. Blood cells

Q: How might the contents of the filtrate be altered if the filtration membrane is damaged or destroyed?

f. Factors affecting Filtration Rate (125 mL/min or 180 L per day!!)

1. Autoregulation (see Glomerular Filtration: p. 11)

a. Afferent arteriole diameter

Q: What happens to its diameter when BP rises?

......When BP falls?

2. JG Apparatus

a. Decreased Na+ concentration (decreased osmolarity) of filtrate causes macula densa cells to signal the release of _______________________ from the JG cells

b. Renin-Angiotensin Mechanism

3. Sympathetic N.S. Stimulation (see Glomerular Filtration: p. 14)

Note: Interactive Physiology Urinary System: Early Filtrate Processing is very detailed. I've chosen certain pages to view and others to ignore. The only things you are responsible for are the items on this lecture outline.

2. Tubular Reabsorption

a. Many substances in filtrate are reabsorbed by tubules

b. Direction of movement: from PCT ----> interstitium -------> bloodstream

c. Most reabsorption occurs in the ________________________

d. What gets reabsorbed and how? (See Interactive Physiology Urinary System: Early Filtrate Processing pp. 5-6, skip pp. 7-8, watch pp. 9-13)

1. Sodium ions move by both passive and active transport (Na+/K+ ATPase pump activity) (p. 9) ___________________________________________. This facilitates the reabsorption of......

2. Water - by osmosis (pp. 5-6) ___________________________________________

3. Chloride (Cl^-) follows the electrochemical gradient established by Na⁺ (passive transport)

4. Glucose moves by cotransport (with sodium ions) and facilitated diffusion ("carrier-mediated" transport which is passive) (pp. 10-11) ___________________________________________

e. Transport maximum (Early Filtrate Processing, pp. 12-13)

f. Diuresis

g. Osmotic diuresis

3. Tubular Secretion

a. Direction of movement: from bloodstream to interstitium to DCT or collecting duct

b. Substances that are secreted:

1. Drugs such as penicillin
2. Hydrogen ions (to balance pH)
3. Potassium ions (under hormonal influence)

c. Hormonal regulation of secretion (see Interactive Physiology Urinary System: Late Filtrate Processing)

1. Aldosterone and ADH (p. 5)

Q: How do caffiene and alcohol affect urine output specifically?

2. Antidiuretic hormone (pp. 11-12)

Q: Does urine become concentrated or dilute when you are overhydrated? When you are underhydrated?

Q: In which of the above instances (overhydration or underhydration) would ADH release be stimulated?

C. Summary of Regulation and Hormonal Control of Kidney Function (see Interactive Physiology CD)

1. Autoregulation by the Kidneys (Glom. Filt. p. 11)

2. Sympathetic Nervous System (Glom. Filt. p. 14)

3. Renin-angiotensin system (see flow chart in textbook)

4. ADH (affects urine volume) (see above section for review pages in IP-CD)

5. Aldosterone (affects urine volume) (same for ADH, see above)

6. Atrial Natriuretic Peptide (ANP) - a renin-angiotensin antagonist

III. Urine Transport, Storage and Elimination

A. Ureters
B. Urinary bladder
C. Urethra

1. Internal urethral sphincter
2. External urethral sphincter

D. Micturition Reflex and Urination (see textbook)

1. Stretch receptors
2. Sacral region of spinal cord

E. Normal components of urine

1. 95% water (more or less)
2. Urea
3. Uric acid
4. Creatinine

F. Abnormal Components of Urine (see Lab Manual for details)

NAME	SUBSTANCE DETECTED IN URINE	POSSIBLE CAUSES
Glycosuria/ Glucosuria
Ketonuria
Albuminuria/ proteinuria
Bilirubinuria
Hematuria
Pyruria

IV FLUID, ELECTROLYTE AND ACID-BASE BALANCE (See Interactive Physiology Fluids and Electrolytes)

A. Fluid Compartments (see Intro to Body Fluids: p. 10)

______% of the body is water by weight.

1. Intracellular fluid (ICF)

a. Location

b. Of the total body water, ______% is found in the ICF.

c. High in potassium, phosphate, magnesium, sulfate, & protein (see p. 14 for review)

2. Extracellular fluid (ECF)

a. Locations and examples of ECF:

b. Of the total body water, ______% is found in the ECF.

c. High in sodium, chloride and bicarbonate (see p. 14 for review)

Q: What is an "electrolyte?"

B. Fluid Shifts (osmosis: what happens to the RBC in each of the following 3 conditions?) (see p. 19-20)

1. Isotonic

2. Hypertonic

3. Hypotonic

Teacher's note: Recall our discussion of the term "osmotic pressure" and I defined it as a force that attracts water. ADAM refers to osmotic pressure as the "colloid osmotic pressure" or "oncotic pressure." For simplicity, we will continue to use the term "osmotic pressure" and our own definition.

Q: Which electrolyte influences fluid shifts most? (hint: see p. 20)

C. Fluid and Electrolyte balance are interconnected as electrolytes are dissolved in water

D. Regulation of Fluid Intake

1. Hypothalamus ("thirst center")

2. Osmoreceptor cells sense increasing osmotic pressure of the plasma. They inform the hypothalamus which produces a desire to drink. In addition, if you are losing water more rapidly than normal, say through sweating, this temporarily decreases your blood volume which stimulates the renin-angiotensin mechanism. How is this mechanism going to assist someone who needs more water? (see text or Interactive Physiology Fluids and Electrolytes: Water Homeostasis, p. 18)

E. Regulation of fluid balance (a REVIEW)

1. ADH (inhibited by excess water intake)

2. Aldosterone and Na⁺

F. Edema - while normally thought to be a water imbalance, it is typically caused by electrolyte imbalances.

G. Electrolyte Balance

1. Sources of electrolytes - food, beverages, & by-products of metabolism

2. Examples of electrolytes (can you write their chemical abbreviations?) -

Sodium, potassium, calcium, magnesium, chloride, sulfate, and hydrogen ions

H. Electrolyte balance

1. Aldosterone

2. ANP

3. Parathyroid glands (PTH)

I. Acid-Base Balance (see Interactive Physiology Fluids and Electrolytes: Acid-Base Homeostasis, pp. 1-10 for a great pH review. Note: Most of this section of the CD is very good and much of it is a review of things discussed previously this semester)

1. Sources of hydrogen ions

a. Aerobic respiration

CO₂ + H₂O --> _________ --> _________

b. Anaerobic respiration and ___________ acid generation

c. Incomplete oxidation of fatty acids forms ketone bodies

2. Strengths of acids and bases

a. Strong acids (Q: Are there any strong acids in the body?)

______________________________________

b. Weak acids

______________________________________

c. Strong bases (Q: Are there any strong bases in the body?)

______________________________________

d. Weak bases

______________________________________

3. Regulation of hydrogen ion concentration (3 mechanisms: a, b and c below, Q: Of these three mechanisms, which is the quickest to respond to fluctuations in pH of the body fluids? Which is the slowest to respond?)

a. Acid-base buffer systems: Function: to minimize pH changes in the body fluids

i. Protein buffer system

ii. Carbonic Acid-Bicarbonate ion buffer system

iii. Phosphate buffer system

b. Respiratory Center as an Acid-Base Controller

i. Brain stem

ii. Controls rate and depth of breathing

iii. Diffusion of _______________ into the CSF causes the following:

CO₂ + H₂O --> _______________ --> _______________

iv. This stimulates the chemosensitive area of the Medulla

v. Physiological response = _______________

vi. KEY stimulus to the chemosensitive area is _______________

c. Renal Contributions to pH Regulation

1. Secretion of hydrogen ions
2. Phosphates in the filtrate and ammonia in the urine

4. Respiratory Acidosis

a. Blood pH less than 7.35 due to CO₂ accumulation

b. Causes:

1. Respiratory Center injury
2. Obstructed airway
3. Pneumonia or emphysema (hypoventilation)

c. Treatment

5. Metabolic Acidosis

a. Accumulation of non-respiratory acids or excessive loss of bases (especially bicarbonate ions)

b. Causes:

1. Kidney failure
2. Keto-acid production
3. Vomiting from stomach and intestines
4. Prolonged diarrhea

c. Treatment

6. Respiratory Alkalosis

a. pH of blood exceeding 7.45 due to loss of CO₂

b. Causes:

1. Hyperventilation

c. Treatment

7. Metabolic Alkalosis

a. Excessive loss of hydrogen ions or accumulation of bases (especially bicarbonate ions)

b. Causes:

1. Vomiting stomach contents only

c. Treatment

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Last Updated 04/15/08