Anatomy

arteries

carry blood away from the heart, largest blood vessels, highest pressure, three tunics

veins

carry blood back to the heart, three tunics

capillaries

exchange vessels, site where gasses, nutrients, and hormones pass between the blood and tissue fluid, one tunic, smallest blood vessels, lowest pressure

tunica interna (tunica intima)

lines the blood vessel (most inner layer), exposed to blood, act as a selectively permeable barrier, composed of endothelial cells, found in all blood vessels

tunica media

middle layer, smooth muscle, collagen, and elastic tissue, regulates diameter, found in veins and arteries

tunica externa

outermost layer, loose connective tissue, anchors vessel and provides passage for small nerves, found in veins and arteries

conducting (elastic or large) arteries

biggest arteries, aorta, common carotid, pulmonary trunk, have a layer of elastic tissue

distributing (muscular or medium) arteries

mid-sized, distributes blood to specific organs, brachial, femoral, renal arteries, smooth muscle layer

resistance (small) arteries

arterioles are smallest arteries, control amount of blood to various organs, thick tunica media and thin tunica externa

metarterioles

branches of arterioles, muscle cells form sphincters, diverts blood to other tissues

What is an aneurysm?

a weak point in the artery of the heart wall, forms a thin-walled bulging sac that can burst

baroreceptors

found in carotid sinuses, monitor blood pressure, transmit signals through the glossopharyngeal nerve

continuous capillaries

most common (most tissues), endothelial cells have tight junctions forming a continuous tube with intercellular clefts, allow passage of solutes

fenestrated capillaries

found in kidneys and the small intestine, require rapid absorption or filtration, allow passage of only small molecules

sinusoids (discontinuous capillaries)

found in the liver, bone marrow, and spleen, irregular blood-filled spaces with large fenestrations, allow proteins, clotting factors, and new blood cells to enter

capillary beds

networks of 10-100 capillaries, usually supplied by a single arteriole or metarteriole, control of flow

Which blood vessels contain most of your blood at any given time?

veins

postcapillary venules

smallest venules, exchange fluid with surrounding tissues, tunica interna with no muscle fibers, leukocyte transport

muscular venules

bigger than postcapillary venules, one or two layers of smooth muscle in tunica media, thin tunica externa

medium veins

larger than muscular venules, thin tunica media, thick tunica externa, varicose veins, venous valves

venous sinuses

veins with especially thin walls, large lumens, and no smooth muscle, not capable of vasomotor responses (dural venous sinus and coronary sinus)

large veins

largest veins, smooth muscle in all three tunics, thin tunica media, tunica externa is the thicket layer, venae cavae, pulmonary veins, internal jugular veins

varicose veins

medium veins, cusps of valves pull apart, vessels weaken, blood backflows and further distends the vessels

portal system

blood flows through two consecutive capillary networks before returning to the heart, between hypothalamus and anterior pituitary, kidneys, and between the intestines and liver

anastomosis

convergence point between two vessels other than capillaries (venous most common)

blood flow

the amount of blood flowing through an organ, tissue, or blood vessel in a given time (mL/min)

perfusion

the flow per given volume or mass of tissue in a given time (mL/min/g)

hemodynamics

physical principles of blood flow based on pressure and resistance, inverse relationship between resistance and pressure in regards to flow

normotension

BP ~ 120/80

hypotension

BP < 90/60

hypertension

BP \> 140/90

how blood volume affects BP

increase in blood volume increases BP, and vice versa

how cardiac output affects BP

when cardiac output increases, BP increases, and vice versa

What three things affect peripheral resistance?

blood viscosity, vessel length, and vessel radius

What is the quickest way to regulate peripheral resistance?

vessel radius

vasoconstriction

when smooth muscle of tunica media contracts, decrease in vessel radius

vasodilation

relaxation of smooth muscle, allows blood pressure to expand a vessel, increase in vessel radius

How do sympathetic nerves affect vessel radius?

signals increase vasoconstriction

Histamine causes \____________.

vasodilation

Accumulation of wastes in the blood causes \____________.

vasodilation

medullary ischemic reflex

automatic response to a drop in perfusion of the brain, medulla oblongata monitors its own blood supply

Angiotensin II

increases blood volume and pressure, reabsorption in kidneys, vasoconstriction

atrial natriuretic peptide (ANP)

reduces blood volume, lowers blood pressure, increases secretion, vasodilation

ADH

increases blood pressure, increases reabsorption, vasoconstriction

epinephrine and norepinephrine (blood vessels)

vasoconstriction

epinephrine and norepinephrine (cardiac muscle)

vasodilation

What are the three routes for capillary exchange?

endothelial cell cytoplasm, intercellular clefts, filtration pores or fenestrated capillaries

What are the mechanisms for capillary exchange?

diffusion, transcytosis, filtration, and reabsorption

Fluid filters out of the \________ end of the capillary and osmotically reenters at the \______ end.

arterial, venous

(blood) hydrostatic pressure

drives fluid out of capillary, high on arterial end of the capillary, low on venous end, physical force exerted against a surface by a liquid

colloid osmotic pressure (COP)

draws fluid into capillary, results from plasma proteins

oncotic pressure

net COP (blood COP - tissue COP)

Capillaries reabsorb about __% of the fluid they filter.

85-90

The other __% is absorbed by the lymphatic system and returned to the blood.

10-15

hypoproteinemia

the presence of abnormally low concentrations of protein in the blood, a disorder that affects osmotic pressure

Capillary \__________ at the arterial end.

filtration

Capillary \____________ at the venous end.

reabsorption

edema

accumulation of excess fluid in a tissue

causes of edema

increased capillary filtration, reduced capillary absorption, obstructed lymphatic damage

five mechanisms of venous return

pressure gradient (blood pressure most important), gravity, skeletal muscle pump in the limbs, thoracic (respiratory) pump (pressure changes with inhalation), and cardiac suction of expanding atrial space

How does exercise affect venous return?

exercise increases venous return because heart beats faster and harder, vessels dilate, increased action of thoracic and skeletal muscle pumps

transient ischemic attack (TIA)

brief episodes of cerebral ischemia (lack of blood flow to the brain), caused by spasms of diseased cerebral arteries

stroke or cerebral vascular accident (CVA)

sudden death of brain tissue caused by ischemia (lack of blood flow to the brain), thrombosis is the most common cause

What are the primary causes of hypertension?

obesity, sedentary behavior, and nicotine

side effects of hypertension

major cause of heart failure, stroke, or kidney failure, increases afterload, enlarged myocardium is overstretched, renal arterioles thicken, salt retention (aldosterone)

What is the major function of blood?

transport of oxygen and carbon dioxide

About how much blood is in an adult human body?

4-6L

hematocrit

centrifuge the blood to separate components (erythrocytes, white blood cells and platelets, and plasma)

What does an increased hematocrit mean?

too many RBCs

What does a decreased hematocrit mean?

too much plasma, less RBCs

plasma

matrix of blood, clear, light yellow fluid, about 50% of blood volume, contains proteins, nutrients, hormones, etc.

seven kinds of formed elements

erythrocytes, platelets, neutrophils, eosinophils, basophils, lymphocytes, monocytes

granulocytes

neutrophils, eosinophils, and basophils

agranulocytes

lymphocytes and monocytes

neutrophils

increase in number during bacterial infections, 60-70% of leukocytes, 3-5 lobed nucleus

eosinophils

increased numbers in parasitic infections or allergies, 2-4% of leukocytes, bilobed nucleus

basophils

vasodilatory and anticoagulatory function, vitally important initiators of the inflammatory response, less than 1% of leukocytes, large granules obscure large S-shaped nucleus

lymphocytes

differentiate into cells that produce antibodies, include memory cell lines, destroy cancerous and virally infected cells, 25-33% of leukocytes, large round nucleus

monocytes

involved with immune clearance, differentiate into dendritic cells and tissue macrophages, 3-8% of leukocytes, horse-shoe shaped nucleus

albumin

most abundant plasma protein, contributes to viscosity and osmolarity, blood pressure and flow

fibrinogen

plasma protein, precursor of fibrin threads, helps form blood clots

Where are plasma proteins (besides globulins) synthesized?

liver

viscosity

resistance of a fluid to flow, resulting from the cohesion of its particles, thickness

What two things affect blood viscosity?

RBC count (mostly) and albumin

What happens when viscosity changes?

blood pressure increases or decreases as a result of osmolarity

What three things affect osmolarity?

RBC count, albumin, and sodium

hemopoiesis

production of blood, especially in its formed elements, elements formed in red bone marrow

two principal functions of RBCs

carry oxygen from lungs to cell tissues and pick up carbon dioxide from tissues and bring it to the lungs

What two organelles do RBCs lack?

mitochondria and nucleus

hemoglobin structure

four protein chains (globins), adult has two alpha and two beta chains, fetal contains two alpha and two gamma chains, four heme groups (each carrying one oxygen molecule)

heme group

nonprotein moiety that binds O2 to ferrous iron at its center

Where does oxygen bind in hemoglobin?

heme group

How many oxygen molecules can bind to a single hemoglobin?

four

How many days do RBCs typically live?

120

What hormone regulates the production of RBCs?

erythropoietin (EPO)

How long does it take to create a RBC?

3-5 days

Which organ makes EPO?

kidneys

hypoxemia

deficient amount of oxygen in the blood, lack of RBCs

hypoxia

lack of oxygen in the tissues

What situations cause an increased release of EPO?

hypoxemia, high altitude, increase in exercise, loss of lung tissue in emphysema (increased blood viscosity)