Glomerular Filtration Physiology

These flashcards summarize key concepts from the lecture on glomerular filtration physiology, focusing on the mechanics of filtration, regulation of GFR, and anatomy of the kidney.

What is glomerular filtration?

The process that the kidneys use to filter excess fluid and waste products from the blood into the urine collecting tubules.

What does GFR stand for?

Glomerular Filtration Rate.

What is net filtration pressure (NFP)?

The difference between the forces promoting filtration and those opposing it in the glomerulus.

What are the three main layers of the glomerular filtration barrier?

1. Fenestrated Endothelium 2. Glomerular Basement Membrane 3. Visceral Layer of the Bowman's Capsule.

What is the primary function of angiotensin II?

To act as a potent vasoconstrictor, regulating blood pressure and maintaining GFR.

What influences glomerular filtration rate (GFR)?

Hydrostatic pressure, osmotic forces, and the permeability of the glomerular filtration barrier.

What is the typical GFR range for men?

90-140 mL/min.

What percentage of cardiac output is represented by renal blood flow (RBF)?

20 to 25%.

What are the intrinsic control mechanisms for GFR?

The myogenic mechanism and tubuloglomerular feedback.

What is the relationship between GFR and systemic blood pressure?

GFR must be tightly controlled to maintain fluid homeostasis and systemic blood pressure.

What is the formula for calculating GFR using net filtration pressure?

GFR = Kf × NFP.

What effect does increased blood pressure have on the afferent arteriole?

Increased blood pressure causes the smooth muscle in the afferent arteriole to contract, reducing blood flow.

How does the juxtaglomerular apparatus regulate GFR?

It monitors NaCl concentration and fluid flow rate, releasing signals that can constrict or dilate the afferent arteriole.

What is the primary effect of aldosterone?

To increase sodium reabsorption in the nephron.

What does the term renal clearance refer to?

The volume of plasma from which a substance is completely removed by the kidneys per unit of time.

What is the role of ADH (Antidiuretic Hormone) in kidney function?

To promote water recovery and prevent excessive fluid loss.

What happens when GFR is too high?

Less NaCl is reabsorbed, causing the macula densa to release ATP and adenosine to decrease GFR.

What is blood colloid osmotic pressure (BCOP)?

The pressure that draws water back into the glomerulus due to plasma proteins.

What is the significance of the glomerular basement membrane (GBM)?

It restricts the passage of proteins and larger particles, contributing to selective filtration.

How does the sympathetic nervous system affect renal blood flow?

During stress, it causes vasoconstriction of afferent arterioles, reducing GFR to conserve fluids.

What is the primary function of the glomerulus?

To filter blood to produce a filtrate that lacks cells and large proteins.

What influences permeability of the glomerular filtration barrier?

Molecule size, shape, and electric charge.

What is the typical osmolarity of the glomerular filtrate compared to plasma?

Approximately 300 mOsm/L.

How is GFR affected by changes in renal blood flow?

Changes in renal blood flow directly influence glomerular hydrostatic pressure and hence GFR.

What is the effect of increased capsular hydrostatic pressure on filtration?

It opposes glomerular hydrostatic pressure and decreases net filtration pressure.

What is the function of podocytes in the glomerulus?

They form filtration slits that allow selective passage of molecules based on size and charge.

What can cause a decrease in blood colloid osmotic pressure?

Disorders causing excessive protein loss into the filtrate.

What are the key components of extrinsic mechanisms controlling GFR?

Neural and hormonal mechanisms, primarily affecting systemic blood pressure.

What happens to GFR when the afferent arteriole constricts?

Blood flow into the glomerulus decreases, leading to a lower GFR.

What is the measurement formula for GFR using urinary concentrations?

GFR = (U × V) / P.

What happens when blood pressure falls significantly?

Extrinsic controls override intrinsic mechanisms to maintain adequate GFR.