Exam 2 Flashcards by MATI (Blood Vessels)

1. simple squamous epithelium that lines lumen of all vessels

2. Continuous with endocardium; slick surface reduces friction

1. a basement membrane and loose connective tissue

2. supports endothelium

narrow channel or space between the plasma membranes of adjacent cells that allows selective passage of ions, fluids, and small molecules while helping maintain tissue barrier function

the final segment of an arteriole that directly feeds blood into capillary networks, controlling capillary perfusion through smooth muscle regulation

a small blood vessel immediately downstream of capillaries, specialized for immune cell exit and fluid exchange

1. channel that directly connects terminal arteriole with postcapillary venule (bypasses true capillaries)

   1. Consists of metarteriole and thoroughfare channel

1. cuff of smooth muscle surrounding each true capillary that branches off metarteriole

   1. Acts as valve regulating blood flow into capillary bed

   2. Controlled by local chemical conditions (not innervated)

In serous membranes of intestinal mesenteries

1. capillaries unite to form postcapillary venules

   1. Smallest venules; consist only of endothelium and pericytes

   2. Very porous; allow fluids and WBCs to move easily into tissues

2. Larger venules have a thin tunica media (one or two layers of smooth muscle cells) and a thin tunica externa

Veins

1. tortuous and dilated veins due to incompetent (leaky) valves

   1. over 15% of adults, in lower limbs

   2. Blood pools in lower limbs, valves to weaken and venous walls stretch

2. Elevated venous pressure

   1. bowel movement raises intra-abdominal pressure, preventing blood from draining from anal veins (hemorrhoids)

interconnections of blood vessels (branches of blood vessels connect with one another)

1. interconnected arteries

   1. Provide alternate pathways (collateral channels) to same tissues to ensure continuous blood flow, even if one artery is blocked

   2. Common in joints, abdominal organs, brain, heart (none in retina, kidneys, spleen)

alternative vascular pathways—usually small arteries, arterioles, or connecting vessels—that link two main blood vessels and can carry blood when a primary vessel is narrowed or blocked

1. shunts across capillary beds

   1. metarteriole–thoroughfare channel

1. interconnected veins

   1. So abundant that occluded veins rarely block blood flow or lead to tissue death

1. amount of blood flowing through vessel, organ, or entire circulation in a given period of time (ml/min)

   1. Equivalent to cardiac output (CO) for entire vascular system; relatively constant under resting conditions

   2. At any time, flow through individual organs may vary widely, based on needs

1. force per unit area exerted on vessel wall by blood

   1. Expressed in millimeters of mercury (mm Hg)

   2. Measured as systemic arterial BP in large arteries near heart

   3. Pressure gradient provides driving force that keeps blood moving from higher- to lower-pressure vessels

1. opposition to flow; measure of friction blood encounters along vessel walls

   1. Mostly encountered in peripheral (systemic) circulation, away from the heart, so usually use term total peripheral resistance (TPR)

   2. Three important sources of resistance: blood viscosity, vessel length, and diameter

overall resistance to blood flow in the systemic circulation, primarily determined by the arterioles, and is a key factor in regulating blood pressure

1. the internal resistance to flow in fluids

   1. Refers to the thickness or “stickiness” of fluid

   2. With greater viscosity, it is more difficult for molecules to slide past each other– Increased viscosity equals increased resistance

   3. Kept relatively constant, but can be affected by hematocrit disorders

1. relatively constant, but if a tissue grows so does its blood supply

2. With greater vessel length, more resistance is encountered

   1. Ex. a shorter straw is easier to drink from

1. smaller diameter, greater resistance (more fluid contact with vessel wall)

   1. wider straw easier to drink

2. Fluid closer to walls moves slower than middle of tube (laminar flow/streamlining)

3. Frequently changes to regulate peripheral resistance

4. Resistance varies inversely with 4th power of vessel radius

1. How much the elastic arteries close to heart can stretch (their compliance or distensibility)

2. Volume of blood forced into them at any time

blood pressure rises and falls with each heartbeat

1. pressure exerted in aorta during ventricular contraction

   1. Left ventricle pumps blood into aorta, imparting kinetic energy that stretches aorta

   2. Averages 120 mm Hg in healthy adult

1. lowest measure of aortic pressure when heart is at rest

   1. Averages 70 to 80 mm Hg in healthy adult

1. difference between systolic and diastolic pressure

   1. Felt as throbbing pulsation in artery, or pulse

a rhythmical throbbing of the arteries as blood is propelled through them, typically as felt in the wrists or neck

1. pressure that propels blood to tissues

   1. Heart spends about 2x as much time in diastole (compared to systole)

2. Pulse pressure/ MAP both decline with increasing distance from heart

   1. Pulse pressure phased out in less elastic muscular arteries

   2. Near end of arterial tree, flow becomes non-pulsatile (steady)

1. Systemic arterial BP measured indirectly (from brachial artery) by the auscultatory method using a sphygmomanometer

a medical technique that uses a stethoscope to listen to internal body sounds, commonly for assessing blood pressure, heart, lung, and abdominal function

Pressure when first sounds heard, as blood starts to spurt through artery

Pressure at which sounds disappear, as artery no longer constricted; blood flows freely

1. chronic high systolic BP (above 130 mm Hg) or diastolic BP (above 80 mm Hg)

2. Slowly damages the heart and vessels; called “silent killer”

   1. Usually asymptomatic for first 10 to 20 years

   2. Prolonged hypertension is major cause of heart failure, vascular disease, renal failure, and stroke

1. about 90% of hypertensive people have primary, or essential, hypertension

   1. No underlying cause identified; result of genetic and environmental factors

2. Risk factors: heredity, diet, obesity, age, diabetes mellitus, stress, smoking

3. No cure but can often be controlled

1. Less common, accounting for about 10% of cases

2. Due to identifiable disorders including obstructed renal arteries, kidney disease, and endocrine disorders such as hyperthyroidism and Cushing’s syndrome

3. Treatment focuses on correcting underlying cause

1. Low blood pressure below 90/60 mm Hg

2. Usually not a concern unless it causes inadequate blood flow to tissues

3. Often associated with long life and lack of cardiovascular illness

temporary low BP and dizziness when suddenly rising from sitting or reclining position

1. can be a concern if sign of serious condition

   1. Ex. Addison’s disease, hypothyroidism, or severe malnutrition

important sign of circulatory shock

1. an abnormal increase in interstitial fluid volume; this excess capillary filtrate results from either

   1. Rise in outward directed pressures, leading to higher NFP (more filtrate)

   2. Drop in inward directed pressures (less reabsorption), also leading to higher NFP

1. low levels of plasma proteins resulting from malnutrition, liver disease, or glomerulonephritis (in which plasma proteins are lost in urine)

   1. causes a decrease in capillary colloid osmotic pressure which hinders fluid return to blood

also called the circulatory system, is the network of blood and lymph vessels that transports blood, nutrients, oxygen, and waste throughout the body

1. pulmonary

2. systemic

short loop that runs from heart to lungs and back to heart

1. long loop to all parts of body (tissues and their cells) and back to heart

   1. Heart pumps blood out into single systemic artery, the aorta

   2. blood returning to the heart is brought by 2 terminal systemic veins (venae cava)

      1. exception is blood collected by cardiac veins (drained from myocardium) (C sinus)