Post on 17-Jan-2016
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Chapter 21
Blood Vessels
Direction of Flow
Heart to aorta to arteries to arterioles to capillaries.
Capillaries to venules to veins to vena cava to heart.
ArteriesVeins
• Capillaries form Microcirculation• Microscopic vessels that connect arterioles to venules• Found near every cell in the body but more extensive in
highly active tissue (muscles, liver, kidneys & brain)•entire capillary bed fills with blood when tissue is active•lacking in epithelia, cornea and lens of eye & cartilage
• Function is exchange of nutrients & wastes between blood and tissue fluid
• Structure is single layer of simple squamous epithelium and its basement membrane
Capillaries:
1. Continuous
2. Fenestrated
3. Sinusoid
Venous valves
Blood Distribution
• 12% pulmonary vessels
• 8 % = heart
• 15% = systemic arteries and arterioles
• 5% = capillaries
• 60% = systemic veins and venules
Venous flow occurs by:
1. muscle contraction
2. respiratory pump
3. valve assistance
4. Ventricular relaxation
Varicose Veins
• Twisted, dilated superficial veins– caused by leaky venous valves
• congenital or mechanically stressed from prolonged standing or pregnancy
– allow backflow and pooling of blood• extra pressure forces fluids into surrounding tissues
• nearby tissue is inflamed and tender
• Deeper veins not susceptible because of support of surrounding muscles
Anastomoses• Union of 2 or more arteries supplying the same body
region– blockage of only one pathway has no effect
• circle of willis underneath brain• coronary circulation of heart
• Alternate route of blood flow through an anastomosis is known as collateral circulation– can occur in veins and venules as well
• Alternate routes to a region can also be supplied by nonanastomosing vessels
Pulse Pressure
• Pulse pressure = systole - diastole
• MAP = diastolic pressure + pulse pressure/3
• MAP = mean arterial pressure
• MAPB = diastole + 1/3 (systole – diastole)
• MAPB = mean arterial blood pressure
Blood PressureInfluenced by:
• Peripheral resistance
• Heart efficiency
• Blood viscosity
• Total blood vessel length
• Arteriole elasticity
• Blood volume
Hormones that affect BP
• Renin angiotensin
• Epinephrine and norepinephrine
• Antidiuretic hormone
• Atrial natriuretic peptide
Autoregulation of BP
• Physical changes
• Vasodilating and constricting chemicals
Major Branches of the Aorta
• Coronary arteries• Brachiocephalic• Left common carotid• Left subclavian• Celiac• Superior mesenteric artery• Renals• Ovarian / testicular• Inferior mesenteric
Minor Branches of the Aorta
• Pericardial Thoracic
• Bronchial Lumbar
• Esophageal Suprarenal
• Mediastinal
• Intercostal
• Phrenic
Celiac circulation
Abdominal arteries
Arterial supply and venous drainage of the liver
Hypertension
• Systole > 140
• Diastole > 90
• Causes: diet high in fat and sodium, obesity, older age, race, heredity, stress, and smoking.
Words to Learn
• Aneurysm Shock• Angiogram Sphygmomanometer• Diuretic Korotkoff sounds• Phlebitis Angiogenesis• Phlebotomy Hypotension• ThrombophlebitisOcclusion• Syncope White Coat Hypertension• Tachycardia Edema