Lecture 12: Capillaries & Veins Flashcards
What are “Capillaries?”
Site of exchange of materials between the blood and tissues
What are the 3 factors that enhance diffusion?
1) Diffusing molecules only have a short distance to travel
2) Incredible numbers of capillaries (10-40 billion)
3) Slow moving blood
What organs would you find the Continuous Capillaries?
- muscles
- skin
- lungs
- CNS
What organs would you find the Fenestrated Capillaries?
- Kidneys
- Intestines
What organs would you find the Sinusoidal Capillaries?
- Liver
What is Fick’s Law?
the rate of diffusion of one material in another is proportional to the negative of the gradient of the concentration of the first material.
What are Veins?
serve as a blood reservoir and passageways back to the heart
Veins have small radii, so they offer little resistance to flow.
T/F
False, they have large radii
Veins that serve as a blood reservoir is often referred to as:
-Capacitance Vessels
Veins have ____walls with less _____muscle than arteries
Thinner; Smooth
Veins have very _____ elasticity
More _____ than elastin
Little;
Collagen
What is “Venous Return?”
Volume of blood entering each atrium per minute from the veins
What is the mean pressure average when blood enters the venous system?
17 mm Hg
Atrial pressure is around 0 mm Hg, there’s still a driving pressure.
T/F
True
What are the 5 factors that enhance venous return?
1) Cardiac Contraction (suction)
2) Sympathetically Induced Venous Tone
3) Skeletal Muscle Activity
4) Venous Valves
5) Respiratory Activity
During Ventricular contraction:
The ___ valve are drawn ______. enlarging the atrial cavities
AV;
Downwards
During Ventricular contraction:
The atrial pressure drops BELOW 0 mm Hg.
T/F
True
During Ventricular contraction:
Increase in ___to_____ pressure gradient so venous return is _______
vein; atria
enhanced
Sympathetic Stimulation produces _____ venous tone.
Modesty _____ venous pressure.
Increases the _____ _______ to drive more ______ into the Right Atrium
Increased
Increases
Pressure Gradient; blood
Many ____ veins in the extremities lie between ______ muscle, so when the muscles _____, the veins are _______
Large
Skeletal; Contract
Compressed
Venous Valves on Venous Return:
Blood can only move in a __________ fashion in the veins due to ______ way valves spaced about 2-4 cm intervals.
When these valves fail, we get _______ veins
Unidirectional
one
varicose
Due to ____ activity. the pressure within the chest cavity is _____ mm Hg less than ______ pressure
Respiratory
5; atmospheric
