Blood Vessels Flashcards
Three Tunics of Artery and Vein Walls
(1) Tunica externa - loose connective tissue, lots of ANS nerve fibers, vaso vasorum
(2) Tunica media - smooth muscle, collagen, elastin - vasomotion
(3) Tunica interna - permeable layer consisting of endothelium (simple squamous epithelium)
3 Types of Blood Vessels
(1) Arteries are efferent vessels, carrying blood away from the heart
(2) Veins are afferent vessels, carrying blood toward the heart
(3) Capillaries serve as the exchange vessels of the circulatory system
Three Classes of Arteries
(1) Conducting (elastic or large) - largest class that contains elastic to withstand pressure “upstream” (ex aorta, common carotid, subclavian)
(2) Distributing (muscular or medium) - distribute blood to specific organs (ex brachial, femoral, renal, splenic)
(3) Resistance (small) - typically not given names - smallest are arterioles
Metarterioles
Link arterioles and capillaries, contain precapillary sphincter that regulates blood flow
Carotid Sinuses versus Carotid Bodies
- Carotid sinuses contain baroreceptors - increase in BP stimulates CN IX which delivers signals to the vasomotor and cardiac centers
- Carotid bodies contain chemoreceptors - change in chemistry stimulates CN IX and X to deliver signals to the respiratory center
- *there are also aortic bodies that perform similar functions**
Three Types of Capillaries
(1) Continuous capillaries are found in skeletal muscle and allow for passage of small molecules
(2) Fenestrated capillaries are found in the kidneys, endocrine glands, small intestine, and choroid plexus of the brain
(3) Sinusoids (discontinuous) capillaries are found in the bone marrow, liver, and spleen
Five Types of Veins
(1) Postcapillary venules
(2) Muscular venules
(3) Medium veins make up most named veins and contain venous valves
(4) Venous sinuses are thin veins not capable of vasomotion
(5) Large veins include the vena cavae, pulmonary veins, internal jugular veins, renal veins
Three Portal Systems
Portal systems consist of two capillary networks before returning to the heart
(1) Glomerular-Pericapillary
(2) Hypothalamo-Hypophyseal
(3) Hepatic
Types of Anastomoses
- Arteriovenous anastomoses drain from artery directly into veins
- Venous anastomoses drain vein-vein while arterial anastomoses drain artery-artery
Korotkoff Sounds
- 1st sound is ~120 mmHg and represents systolic pressure
- 2nd sound is ~80 mmHg and represents diastolic pressure
Pulse Pressure
Stress on small arteries
Systolic - Diastolic = pulse pressure
Mean Arterial Pressure (MAP)
Diastolic + (1/3)Pulse pressure
Three Factors of Blood Pressure
(1) Cardiac output
(2) Blood volume
(3) Peripheral resistance
Factors of Peripheral Resistance
- Blood viscosity
- Length of vessel
- Vessel radius
Three Ways of Controlling Vasomotion
(1) Autoregulation
(2) Neural control (baroflexes, chemoflexes, medullary ischemic reflexes)
(3) Hormonal control
Hormones and BP
Angiotensin II, Aldosterone, ADH, Epi and norepinephrine raise BP
natriuretic peptides lower BP
Three Causes of Edema
(1) Increased capillary filtration
(2) Reduced capillary reabsorption
(3) Obstructed lymphatic drainage
Mechanisms of Venous Return
(1) Pressure gradient
(2) Thoracic pump
(3) Skeletal muscle pump
(4) Cardiac suction
(5) Gravity
Circulatory Shock
State where cardiac output is insufficient to meet the body’s metabolic needs
Two Categories of Circulatory Shock
(1) Cardiogenic shock - inadequate pumping by heart
(2) Low venous return (LVR) shock - CO low due to low return of blood
(a) Hypovolemic LVR shock results from dehydration, trauma, ulcers, etc
(b) Obstructed venous return shock results from tumor or aneurysm suppressing venous flow
(c) Venous pooling (neurogenic shock results from loss of vasomotor tone)
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Septic Shock
bacterial toxins trigger vasodilation and increased capillary permeability
Anaphylactic Shock
Results from exposure to an antigen a person is allergic to
Transient Ischemic Attacks (TIAs)
Minor stroke with dizziness, weakness, aphasia
Cerebrovascular Accident (CVA)
Stroke, sudden death (infarction) of tissue caused by ischemia
