Ch. 20-1 The Blood Vessels Flashcards
What are the three major types of blood vessels?
Arteries, capillaries, and veins
What is the primary function of arteries?
Take blood away from the heart; oxygenated blood if in systemic circuit
What are arterioles?
Small arteries which feed capillary beds
What is the function of capillaries?
Allow transport to and from tissues; only blood vessel with direct cell contact
What do venules do?
Small veins which drain the capillaries
What is the role of veins?
Return blood to the heart; deoxygenated if in systemic circuit
What are the three distinct layers of blood vessel walls?
- Tunica Interna/Intima
- Tunica Media
- Tunica Externa
What is the tunica interna/intima?
Most internal layer; endothelium forming a slick surface that minimizes friction
What is the tunica media primarily composed of?
Circularly arranged smooth muscle and elastic tissue
What does the tunica externa consist of?
Loosely woven collagen fibers that support and protect the vessel
What are the major structural differences between arteries and veins?
- Arteries: Thick walls, smaller lumen, may have elastic membrane
- Veins: Thin walls, larger lumen, have valves
What is the function of elastic arteries?
Large, thick-walled arteries found near the heart that allow continuous blood flow
How are muscular arteries characterized?
Deliver blood to specific organs; have the most smooth muscle and are active vasoconstrictors
What is the average length and diameter of capillaries?
Average length = 1 mm; diameter = 10 µm
What are the three types of capillaries?
- Continuous
- Fenestrated
- Sinusoid
What is the primary function of capillary beds?
Material exchange (oxygen, nutrients, wastes etc.)
What regulates blood flow into capillary beds?
Precapillary sphincters
What is blood flow (F) defined as?
Volume of blood flowing through a given area/time period (ml/min)
What is blood pressure (P)?
Force per unit area exerted on wall by blood, usually referring to arterial blood pressure
What determines resistance (R) in blood flow?
- Blood viscosity
- Blood vessel length
- Blood vessel diameter
What is the relationship between blood flow, pressure change, and resistance?
F = ΔP / R
Where is systemic blood pressure greatest?
In the aorta
What happens to blood pressure as it moves further from the heart?
It decreases
What are systolic and diastolic pressures?
- Systolic: Pressure at peak of ventricular contraction
- Diastolic: Pressure when ventricles relax
What is the typical blood pressure reading format?
Systolic/Diastolic (e.g., 120/80 mm Hg)
What adaptations help return venous blood to the heart?
- Muscular pump
- Respiratory pump
- Sympathetic venoconstriction
What is the role of the muscular pump in venous return?
The action of skeletal muscle surrounding veins ‘milks’ the blood upwards
What does the respiratory pump do?
Pressure changes during breathing pull blood up towards the heart
What is the formula for cardiac output (CO)?
CO = SV x HR
