1.1 - Renal Function Test

What are the 2 regions of the kidney?

• Cortex

• Medulla

1. What is the functional unit of the kidney?

2. What are its 5 basic parts?

• NEPHRONS

  • Glomerulus

  • Proximal Convoluted Tubule (PCT)

  • Loop of Henle

  • Distal Convoluted Tubule (DCT)

  • Collecting Ducts

The kindey receives about how much blood pumped through the heart at all times?

25%

On an average body size of 1.73 m² of surface, the about how much is the:

1. total renal BLOOD flow

2. total renal PLASMA flow

• BLOOD FLOW = 1,200 mL/min

• PLASMA FLOW = 600-700 mL/min

1. The glomerulus consist of approximately how many capillaries?

2. What kind of capillaries?

3. What is do you call the walls of these capillaries?

1. about 8 capillaries

2. Fenestrated capillaries

3. glomerular filtration barrier

What characteristics of a substance is filtered in the glomerulus?

• [Non-selective] substances with molecular weight of <70,000 KD

• Negatively charged particles (ex. protein)

Glomerular Filtration Barrier —refers to the walls of the capillaries of glomerulus. What are the cellular layers of these walls?

• Capillary wall membrane

• Basement membrane

• Visceral epithelium of Bowman’s Capsule

What are the two type of Glomerular Pressure? differentiate each?

• HYDROSTATIC PRESSURE

  • pushes fluid out of the blood vessels (filtration), driven by blood pressure

• ONCOTIC PRESSURE

  • pulls fluid back into the vessels (reabsorption)

This type of Glomerular Pressure results to the smaller size of the efferent arteriole and the glomerular capillaries enhances filtration

Hydrostatic Pressure

Explain the Renin-Angiotensin-Aldosterone-System (RAAS)

• Macula Densa detects LOW blood pressure and sodium level

• Macula Densa signals Juxtamedullary cells to release RENIN

• RENIN binds to ANGIOTENSINOGEN to form ANGIOTENSIN 1

• ANGIOTENSIN CONVERTING ENZYME (ACE) converts ANGIOTENSIN 1 → 2
  

• ANGIOTENSIN 2 actions:

  • Vasoconstriction of efferent arteriole

  • Reabsorption of Sodium in PCT

  • Stimulates adrenal cortex to release Aldosterone → Reabsorption of Sodium in DCT

  • Stimulates hypothalamus to release Antidiuretic Hormone (ADH) → Reabsorption of Water in collecting duct

RECALL: What are the action of the Renin-Angiotensin-Aldosterone-System (RAAS)

• Vasoconstriction of efferent arteriole

• Reabsorption of Sodium in PCT

• Stimulates adrenal cortex to release Aldosterone

  • Aldosterone → reabsorption of sodium in DCT

• Stimulates hypothalamus to release Antidiuretic Hormone (ADH)

  • ADH → reabsorption of water in collecting duct

• This is the BEST overall indicator of the level of kidney function

• The STANDARD TEST used to measure the filtering capacity of the glomeruli

Glomerular Filtration Rate (Clearance Tests)

What are the different Clearance Tests?

• Creatinine Clearance —_{^{never mistaken of CREATINE}}

• Inulin Clearance

• Cystatin C Clearance

• Beta-Trace Protein

• Radioisotopes

Will the function of Glomerular Filtration Rate (GFR) decreases when half of the nephrons are non-functional (ex: 1 kidney donated)?

NO — GFR remains unchanged if functional nephrons double their filtering capacity

This clearance test if the earliest glomerular filtration test because of its presence in all urine specimens

Urea Clearance