chapter 26: urinary system

glomerular filtration membrane area thickness?

thickness area of < 0.1 micrometers in thickness

why is the glomerular filtration membrane really thin?

thinner → faster diffusion for glomerular filtration

what does the glomerular filtration membrane consist of?

1. glomerulus capillary wall (fenestrated capillary)

2. fused basement membrane

3. visceral layer of Bowman’s capsule

what is the glomerulus capillary wall (fenestrated capillary) made of?

simple squamous epithelium with pores (fenestra)

what are the pores called in glomerulus capillary wall?

fenestra

what is the fused basement membrane made of?

areolar connective tissue

what is the visceral layer of Bowman’s capsule made of?

modified simple squamous epithelium with podocytes and filtration slits

glomerular filtration consists of?

• glomerulus capillary wall (fenestrated capillary): simple squamous epithelium with pores (fenestra)

• fused basement membranes: areolar connective tissues

• visceral layers of Bowman’s capsule: modified simple squamous epithelium with podocytes and filtration slits

podocytes

cells of the visceral layer of Bowman’s capsule

podocytes have foot processes (pericles) that wrap around?

glomerular capillaries

in podocytes, what wraps around the glomerular capillaries in the podocytes?

foot processes (pericels)

foot processes can also be known as?

pericels

filtration slits

gaps between adjacent foot processes (6-9 nm in width)

podocytes

• are cells of visceral layer of Bowman’s capsule

• have foot processes (pericels) that wrap around glomerular capillaries

• filtration slits: gaps between adjacent foot processes (6-9 nm in width)

glomerular filtration

passage across filtration membrane to produce essentially protein free filtrate

what Is glomerular filtration driven by?

net filtration pressure

(e.g. glomerular hydrostatic pressure is the passive force that creates filtrate)

in glomerular filtration, which solutes can and cannot pass?

• small solutes can pass through

• large solutes and materials cannot pass through (e.g. plasma proteins cannot pass through)

glomerular filtration

• driven by net filtration pressure (e.g. glomerular hydrostatic pressure is the passive force that creates filtrate)

• small solutes molecules pass through

• large solutes and materials cannot pass through (e.g. plasma proteins cannot pass through)

types of glomerular filtration pressure

1. glomerular hydrostatic pressure (GHP)

2. blood colloid osmotic pressure (BCOP)

3. capsular hydrostatic pressure (CsHP)

4. capsular filtrate colloid osmotic pressure (CfCOP)

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glomerular hydrostatic pressure (GHP) pressure?

~50 mmHg

glomerular hydrostatic pressure results from?

glomerular capillary blood pressure

function of glomerular hydrostatic pressure?

push down and solutes out of bloodstream into the filtrate

glomerular hydrostatic pressure

• ~50 mmHg

• result from glomerular capillary blood pressure

• push down and solutes out of bloodstream into filtrate

blood colloid osmotic pressure (BCOP) pressure?

~25 mmHg

blood colloid osmotic pressure results from?

suspended plasma proteins in blood

blood colloid osmotic pressure function?

keep water in bloodstream against filtration

blood colloid osmotic pressure (BCOP)

• result from suspended plasma proteins in blood

• keep water in bloodstream against filtration

capsular hydrostatic pressure (CsHP) pressure?

~15 mmHg

capsular hydrostatic pressure results from?

filtrate resistance to flow along nephron

capsular hydrostatic pressure function?

oppose glomerular hydrostatic pressure against filtration

capsular hydrostatic pressure (CsHP)

• results from filtrate resistance to flow along nephron

• oppose glomerular hydrostatic pressure against filtration

capsular filtrate colloid osmotic pressure (CfCOP) pressure?

~0 mmHg

capsular filtrate colloid osmotic pressure

• larger solutes (e.g. plasma proteins) do not pass through filtration membrane

• is essential protein free filtrate

capsular filtrate colloid osmotic pressure function?

• essential protein free filtrate

net filtration pressure (NFP)

combination of the above 4 forces together: NFP = GHP - BCOP - CsHP + CfCOP

net filtration pressure equation

NFP = GHP - BCOP - CsHP + CfCOP

If the NFP is positive, what is the net force?

outward force

If the NFP is negative, what is the net force?

inward force

If the NFP is positive, with an outward net force what occurs?

filtration

If the NFP is negative, with a inward net force what occurs?

absorption (first entry) or reabsorption (move out and re-enter)

What is the glomerular net filtration pressure, using the equation and pressures?

NFP = GHP - BCOP - CsHP + CfCOP

= 50 - 25 - 15 + 0

= +10 mmHg

Thus, the fluid moves out of the glomerular capillary into the capsular space → glomerular filtration

If the glomerular net filtration is +10 mmHg, what does that mean?

fluid moves out of the glomerular capillary into the capsular space → glomerular filtration

glomerular filtration rate (GFR)

amount of filtrate both kidneys produce per minute

what is the average glomerular filtration rate?

• averages 125 mL/min \

• 180 L of filtrate per day

• Renal tubule: 99% reabsorbed into blood stream

• Urine: 1% (1-2 L per day)

Autoregulation (local level)

primary regulatory mechanism that maintains GFR

what is the primary regulatory mechanism that maintains the GFR?

autoregulation (local level)