Blood Vessels Flashcards
3 major typed of blood vessels
- Arteries: carry blood away from the heart (oxygenated blood)
- Veins; carry blood to the heart (deoxygenated blood)
- capillaries: directly exchange gases and nutrient with tissues to meet cellular demand
Blood vessel walls
- Tunica interna (endothelium): reduces friction between the vessel walls & blood
- Tunica media (smooth muscle & elastin):controls vasoconstriction/dilation of the vessel
- Tunica externa (loosely woven collagen fibers): protects, reinforces, and anchors the vessel to surrounding structures
Elastic Arteries
large amounts of elastin to allow the vessels withstand the pressure changes of the cardiac cycle
Muscular arteries
Deliver blood to specific body organs and have the greatest proportion to tunica media of all vessel, making them more active in vasoconstrictions
Arterioles
smallest arteries
Regulate blood flow into capillary beds through vasoconstriction/dilation
Capillaries
Smallest vessels
- Allow for exchange of substance between the blood and interstitial fluids of tissue and organs
- Connect arterioles and venules
Continuous capillaries
Most common
- Allow passage of fluids and smalls solutes
- In the brain, the intercellular clefts are replaced with tight junction to make the blood-brain barrier
Fenestrated capillaries
More permeable to fluids & solutes than continuous capillaries
- This helps with absorption in the small intestines and flirtation in the kidneys
Sinusoid capillaries
Leaky capillaries that allow large molecules to pass between the bcos,ood and surrounding tissues (liver, spleen or bone marrow)
Anastomoses
A connection between blood cells that supplied blood to the same region of the body,
- Allow blood to have alternative routes to reach tissues and return back to the heart when one blood vessel is damaged/blocked
Arteriovenous anastomosis
Anastomosis that occurs between an artery and a vein
- Non-anastomosing blood vessels in the same body region can also provide alternate circulation routes
Metarterioles
Unique feature of the circulatory a system around the intestines
Pre-capillary sphincter: surrounds each capillary & acts as a valve to regulate blood flow into t he capillary/keep the blood in the thoroughfare channels
Veins
Venules: formed where capillaries converge and allow fluid and white blood cells to move easily between blood & tissues
Join to form veins
Blood flow
- Volume of blood flowing through a vessel, organ, or the entire circulation in a given period and may be expressed as mL/min
- Blood pressure: force per unit area exerted by the blood against a blood vessel wall and is expressed in (mmHg)
Resistance
A measure of the friction between blood and the blood vessel walls. Related to blood viscosity, vessel length, vessel diameter
Flow, pressure & resistance
- If blood pressure increases, blood flow increases
- resistance increases, blood flow decreases
Peripheral circulation
- Generally refers to circulation in all of the blood vessels outside of the heart and coronary vessels
Peripheral resistance
- the most important factor influencing local blood flow
- vasoconstriction/dilation can dramatically alter local blood flow, while systemic blood pressure remains unchanged
Blood pressure
- Decreases as blood flows from arteries through capillaries and into veins
- Blood pressure results when blood flow is opposed by resistance
Systemic blood pressure
- Highest in the aorta and declines throughout the pathways until it reaches 0 mmHg in the right atrium
Arterial blood pressure
- Relatively high because the arteries close to the heart can be stretched. A large volume of blood is forced into them at during ventricular systole
- Systolic pressure: a peak in pressure produced when the left ventricle contracts, blood is forced into the aorta, which averages 120mmHg
Diastolic pressure
- Occurs when the ventricles enter diastole, aortic valve closes & the walls of the aorta recoil (70-80mmHg), so the blood continues to flow forward into the smaller vessels
Pulse Pressure
- The difference between diastolic and systolic prsssure
- The mean arterial pressure (MAP) represents the pressure that propels blood to the tissues, and is approximately diastolic pressure + 1/3 pulse pressure
Capillary blood pressure
this is low, ranging from 15-40mmHg, which protects the capillaries from ruptures but is still adequate to ensure exchange between blood and tissues
Venous blood pressure
This is low, not pulsatile, and changes every little during the cardiac cycle, reflecting cumulative effects of peripheral resistance
Hypertension
- High blood pressure
- Characterized by a sustained increase in either systolic/diastolic pressure
- Primary hypertension: accounts for 90% of cases, and has no identifiable cause
- Secondary hypertension: 10% of cases, has a root cause by another thing and if that other thing (kidneys) is fixed, then the blood pressure is fixed
Hypotension
- Low blood pressure
- Often due to individual variation. Only a concern if blood flow to tissues becomes inadequate
Circulatory shock
- Any condition in which blood volume is inadequate and cannot circulate normally, resulting in blood flow that cannot meet the needs of a tissue
Hypovolemic shock
- Results form a large scale loss of blood
- May be characterized by an elevated heart rate & intense vasoconstriction
Types of circulatory shock
- Vascular shock
- Transient vascular shock
- Cariogenic shock
Vascular shock
- Occurs with normal blood volume but extreme vasodilation, resulting in poor circulation and a rapid drop in blood pressure
Transient vascular shock
- Due to prolonged exposure to heat, such as while sunbathing, resulting in vasodilation of cutaneous blood vessels
Cardiogenic shock
- Occurs when the heart is too inefficient to sustain normal blood flow and is usually related to myocardial damage, such as repeated myocardial infarcts