A/P Final Flashcards
What is the surface area of the lungs?
70 square meters
What is the surface area of the circulatory system?
500 or more square meters
In the body, what swaps in the V = IR equation?
V = pressure
I = flow
R = resistance
What is the formula for conductance? Explain the relationship
1 / R (resistance). Conductance is the inverse of resistance, if resistance is high, conductance is low, if resistance is low, conductance is high
Where is blood flow control dictated?
At the local level of the capillary
What effect does parallel systems have on pressure?
The more series in parallel, the lower pressure will be
What is the relationship to cross-sectional area and blood vessels in the body?
As you go from the large single vessels to the numerous smaller ones, cross sectional area increases
What is the formula for velocity of blood flow?
Blood flow / cross sectional area
Aorta (CSA of 2.5) 5 / 2.5 = 2 L/min
Vena Cava (CSA of 8) 5 / 8 = 0.625 L/min
Why is pulse pressure wider in the large arteries, especially relative to the Aorta?
Because the large arteries are “stiffer”
What is the pressure range of the LA?
0 - 2
What is the pressure range of the LV?
0 - 120
What is the pressure range of the Aorta?
80 - 100
What is the pressure range of the large arteries?
80- 120
What is the pressure range of the small arteries?
60 - 100
What is the pressure range of the arterioles?
20 - 60
What is the pressure range of the capillaries?
0 - 30
What is the pressure range of the veins?
0 - 5 ish
What is the pressure range of the RV?
0 - 20
What is the pressure range of the pulmonary arteries?
15 - 30 ish
Why does pressure start to drop in the small arteries?
Branching and blood flow resistance increases
What determines pressure in the capillaries at a systemic level?
The pressure in the vessels upstream
What would happen upstream of arteriolar squeeze? Downstream?
It would increase pressure upstream, and decrease it downstream
What is Delta P?
The change in pressure
What happens with a high Delta P? Low?
High = more driving pressure meaning more blood flow can occur
Low = less driving pressure and less flow occurring
What is the MOA of edema in CHF in terms of pressure?
With higher venous pressure, fluid can get pushed (filtered) into the ISF, but it can’t be reabsorbed because of the higher pressure. So Delta P here is smaller.
What drives CO?
Tissue demand
What is the highest point of resistance in an artery? lowest?
Highest = the vessel wall
Lowest = the middle of the blood vessel (blood isn’t touching anything there)
What makes up Poiseuille’s law in the body?
The constant of pie, Delta P and radius, an increases in any of these would lead to more flow. Flow is inverse to blood viscosity and length of the tube, increase any of these and there will be less flow
What is the formula to determine vascular resistance?
Rearrange V = IR -> R = Delta P / Flow
If resistance goes up, either flow is going down, Delta P goes up
What drives the biggest change in flow of a blood vessel?
Radius or circumference of the vessel
What is the pressure on the afferent end of the arteriole? Efferent end?
30 and 10
Which vessels have the most resistance in the body?
Arterioles
What are the 4 starling forces? Give numbers as well
Hydrostatic pressure in the capillary (pushing fluid out) 30 mmHg
Hydrostatic pressure outside the capillary in the ISF (sucking fluid out of the capillary) -3 mmHg
Capillary oncotic pressure (protein pressure, sucking water into the capillary) 28 mmHg
ISF oncotic pressure (protein pressure suck water into the ISF) 8 mmHg
Why is water filtered at the beginning of the capillary and reabsorbed at the end?
A high delta P favors filtration, low favors reabsorption
What happens to pressure as it flows through high resistance vessels?
Pressure drops
What is the mean capillary pressure?
17.3 mmHg
What is the net filtration pressure? What does this mean?
0.3 mmHg, this means we slightly favor filtration
How much fluid is lost due to the net filtration pressure, and what happens to it?
1 - 2 L into the ISF, but it is scavenged by the lymphatic system and dumped back into the Vena Cava
What components make up the capillary oncotic pressure? Fraction of the total?
Albumin - 21.8 / 28 or 22 mmHg (4.5 g/dL)
Globulins - 6 / 28 or 6 mmHg (2.5 g/dL)
Fibrinogen - 0.2 / 28 or 0.2 mmHg (0.3 g/dL)
If you have CHF, the higher venous pressure means less fluid will be reabsorbed, and more gets pushed into the ISF, why is there no immediate edema in early stages of CHF?
The lymphatic system can increase its capacity to suck up fluid 20 fold, allowing it to suck up a lot of water
What is the permeability of compounds compared to? General trends?
The standard permeability of water, which is 1. The larger you are, the harder it is for you to cross a capillary
How do kidneys regulate RBC manufacture?
By erythropoietin release, if oxygen tension is low, EP is released to make the bone marrow grow more RBCs. If oxygen tension is high, EP release is slowed to decrease RBC production
What is the difference in split points of arteries vs veins in the kidney?
Renal artery -> segmental arteries, -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles
Veins are the reverse, interlobular -> arcuate -> interlobar -> segmental -> Renal vein
Describe the basic setup of a nepron
Afferent arteriole -> glomerular capillary bed -> efferent arteriole -> peritubular capillaries
What is the term for deep peritubular capillaries? How many are there?
Vasa Recta, 5% of total PTCs
What occurs in the peritubular capillaries?
The bulk of reabsorption
What organs are the right kidney in contact with? Left?
R = liver
L = stomach, spleen and pancreas
What nerve controls bladder emptying?
Pudendal nerve
What is the supporting structures of the glomerulus?
The podocytes
What category of cell are the podocytes? What is their function?
Endothelial cells, and the slit pores of the podocytes are - charged to repel - charged proteins. Negative ions are still allowed in
What are the large openings on the endothelial layer of the glomerulus? Function?
Fenestrations, allows small things like water, glucose and ions to move with little to no resistance
What is the GFR?
125 ml/min
What is secretion?
Specifically placing something in the urine to be excreted, usually involves a transporter to move it from the capillary into the urine.
What is the formula to determine excretion?
Excretion = Filtration - reabsorption + secretion
What is the average reabsorption rate?
124 ml/min
What is the net filtration pressure in glomerulus? What is different about it relative to a normal capillary?
10 mmHg, and the starting pressure, which is 60 mmHg, double what is in a standard capillary
What is the relationship to BP in the capillary to filtration rate?
The higher the BP, the higher filtration will be, the lower it is, the lower filtration will be
What would happen to filtration if you squeezed the afferent arteriole?
BP in the glomerulus would drop, filtration would decrease
What would happen to filtration if you squeezed the efferent arteriole?
BP in the glomerulus would increase, filtration would increase