IBHS 527 lecture 2

• 1. distribution of oxygen, nutrients
• 2. removal of metabolic wastes like carbon dioxide and urea

• 1. pulmonary
• 2. systemic

(1) right heart --> (2) pulmonary arteries --> (3) pulmonary veins --> (4) left heart --> (5) aorta --> (6) arteries ("away" from heart) --> (7) arterioles --> (8) capillaries --> (9) venules --> (10) veins ("back" to heart) --> (11) vena cava

• 1. arteries
• 2. arterioles
• 3. capillaries
• 4. venules
• 5. veins

• carry blood away from heart
• transport blood under high pressure

smallest arterial branches, strong muscular walls

where diffusion occurs between blood and interstitial fluid - exchange of fluid, gas, nutrients, etc.

small veins that carry blood from capillaries

larger vessels, blood transport back to heart, blood reservoir (where most blood is located)

• 1. tunica intima (innermost layer): endothelium, internal elastic membrane (arteries only)
• 2. tunica media (middle layer): smooth muscle tissue, external elastic membrane (arteries only)
• 3. tunica externa (outmost layer): connective tissue sheath

• arteries:
• 1. thicker walls
• 2. thicker tunica media (more contractile and elastic components - to handle the change in blood pressure by stretching and recoiling to resist breaking)
• 3. endothelial lining has pleated appearance
• veins:
• 1. thinner walls
• 2. tunica externa is thicker than tunica media
• 3. no elastic membranes
• 4. contains smooth muscle cells (SMC) in tunica externa

• controlled by autonomic nervous system
• 1. vasoconstriction: contraction of smooth muscle cells
• 2. vasodilation: relaxation of smooth muscle cells

• 1. afterload on heart (how hard the heart has to work to pump into the vessel)
• 2. peripheral blood pressure
• 3. capillary blood flow

• 1. elastic
• 2. muscular
• 3. arterioles

• tunica media contains elastic fibers, few SMCs
• helps stabilize changes in pressure during systole and diastole
• ex: aorta, pulmonary arteries

• thick tunica media contains more smooth muscle cells (SMCs)
• ex: external carotid arteries, brachial arteries, femoral arteries

• aka resistance vessels (can INC. or DEC. resistance by dilation, constriction)
• smallest in size of arteries
• poorly defined tunica externa
• can dilate or constrict in response to sympathetic nervous system, endocrine system, local factors

• thin walls
• slow blood flow
• consists of endothelial tube within a basal lamina
• no tunica media or externa (only one layer)
• diamater is close to RBC

• 1. continuous
• 2. fenestrated
• *depending on size of molecules to get through

• complete endothelium
• permit diffusion of H₂O, small molecules, lipid-soluble materials
• movement across membrane via pinocytosis

• endothelium contains pores
• pores permit rapid exchange of H₂O and larger solutes (even small peptides)
• found in GI tract (absorption), kidneys, hypothalamus, pituitary

• located in central nervous system ex. blood brain barrier (BBB)
• tight junctions allow passage of water, glucose, amino acids, inorganic ions, lipid soluble molecules
• very restricted permeability via active and passive transport

• 1. facilitated diffusion (passive)
• 2. active transport
• *both use carrier proteins to regulate/allow only specific molecules to come through

• resemble fenestrated capillaries (irregularly shaped, flattened)
• difference: contains gaps between endothelial cells, thin or absent basal lamina
• permits free exchange of H₂O and large solutes (even proteins)
• significant in liver where plasma proteins enter blood and for liver, spleen, bone marrow where phagocytic cells monitor the passing blood

• 1. precapillary sphincter:
• -band of smooth muscle
• -guards entrance to capillary
• 2. direct connections between arterioles and venules:
• -Metarteriole: smooeth muscle that can change in diamter
• -thoroughfare channel: resembles a capillary
• 3. collaterals (vessels):
• -capillaries can receive blood from more than 1 artery (back-up plan). arterial anastomosis

• regulation of diameter of metarterioles and precapillary sphincters
• -local regulation of [oxygen] in tissues and the rate of tissue metabolism

• continuous cycling of contraction and relaxation of smooth muscles that regulate blood flow through capillaries
• -help meet demands of tissue

• players:
• capillaries are the only vessels that allow exchange (of gas and nutrients)
• relies on 3 things:
• 1. wall thickness
• 2. flow velocity
• 3. diameter

• 1. venules
• 2. medium-sized veins
• 3. large veins

• smallest venous vessels, collect blood from capillaries
• some lack tunica media

• similar in size to muscular arteries
• thin tunica media
• thick tunica externa containing collagen and elastic fibers

• contains all 3 layers
• thin tunica media, thick tunica externa
• ex: vena cava

• majority of blood at rest is at the systemic venous system with 64%
• systemic venous system > systemic arterial system > pulmonary circuit > systemic capillaries = heart
• *veins expand easily at low pressures (capacitance vessels)
• -the majority of the blood volume is in veins and the largest cross-sectional area are in capillaries because of the gas and nutrients exchange occurring here

• for a given rise in blood pressure, amount of stretch in vessel
• -expandibility

amount of blood that can be shifted into general circulation (~20)

• hemorrhage
• -systemic veins constrict (venoconstriction) to help increase blood volume in circulation
• -constriction of veins in liver, skin, lungs which shunts blood to delicate organs (brain) and active skeletal muscles

• 1. arterial system = high pressure
• 2. venous system = low pressure (expands easily)

• 1. venous valves: 1 way valves that prevent backflow into capillaries and that affects the venous return (rate of blood flow to heart)
• 2. muscle or venous pump: muscles help squeeze the blood up
• *if standing perfectly still- DEC. in venous return because not flexing muscles

• excess stretching of veins due to INC. pressure over weeks, months, or years - long periods of time
• veins distend, but valves do not
• blood pools in veins, distends them more

• aching or heavy felling in legs
• throbbing
• muscle cramping
• itching around veins
• skin ulcers around veins

• age
• sex - more toward females
• genetics
• obesity
• standing for long periods of time

• 1. self-help:
• -exercise
• -weight loss
• -elevated legs
• 2. surgery or outpatient procedures:
• -sclerotherapy
• -vein stripping/removal

• exercise
• weight control
• avoid wearing heels
• avoid tight clothes
• elevate legs
• don't cross legs

• abnormal bulge in the weakened wall of a blood vessel
• location:
• -brain = stroke
• -aorta = death
• tend to form gradually
• often go undetected until they leak or rupture
• risk of rupture depends on size

• *most common aneurysm
• 2 types:
• 1. thoracic aortic aneurysm (TAA) - ~25%
• 2. abdominal aortic aneurysm (AAA) - ~75% MOST
• 

• 1. high blood pressure (BP)
• 2. atherosclerosis
• 3. Marfan syndrom - connective tissue disorder

• advanced age
• male sex 5-10X greater risk
• tobacco use
• family history
• race (whites at greater risk)

• 1. drugs: ß-blockers, vasodilators
• 2. surgery: removal of aneurysm, insertion of stent

• atherosclerosis (main cause)
• blood clots, injury to limbs, altered anatomy of ligaments or muscles, infection

smoking, diabetes, obesity, high BP, high cholesterol, increased aged, family history

• leg pain while walking
• leg numbness or weakness
• changes in toenails or color of legs
• coldness and/or hair loss on legs

increased risk for coronary artery disease, heart attack, stroke, and transient ischemic attacks (TIA) - mini stroke

• 1. statins (cholesterol lowering drugs):
• -simvastatin, lovastatin, atorvastatin (LIPITOR)
• 2. ß-blockers or ACE inhibitors:
• -Atenolol, carvedilol (COREG), metoprolol (TOPROL XL) or enalapril, lisinopril
• 3. medication to control blood sugar
• 4. clot prevention:
• -daily aspirin or clopidogrel (PLAVIX)
• 5. symptom relief medication
• *Lifestyle modifications:
• -quit smoking, exercise, healthy diet, careful foot care

• 1. line blood vessels
• 2. vasoregulation:
• -vasodilators secreted: NO (nitric oxide - also anti-thrombotic), PGI₂
• -vasocontrictors secreted: endothelin
• -balance is key!!
• 3. coagulation:
• -normal conditions: endothelium is smooth surface, anti-thrombotic (inhibits platelet adhesion and clotting by secretion of NO, PGI₂, and tPA)
• -physical or chemical perturbation: endothelium becomes pro-thrombotic (platelet-activating factor (PAF; promotes platelet activation and adhesion); switch is initiated by induction of tissue factor
• 4. interaction with blood cells:
• -in response to tissue injury or infection (inflammation)
• -leukocytes (via cellular adhesion molecules or CAMs) and platelets can adhere to endothelium; release of cytokines
• -permeability of vessel increases