A&P Chapter 13: Cardiovascular System

brady-

slow

diastol-

dilation

-gram

something written

papill-

nipple

syn-

together

systol-

contraction

tachy-

rapid

heart

a muscular pump that generates force that moves blood through vessels

cardiovascular system

the heart and blood vessels

amount of blood pumped each day

around 7000 liters

amount of heart contractions in a life time

around 2.5 billion

veins

vessels that carry blood from the body toward the heart (usually oxygen poor blood carrying other waste)

arteries

vessels that carry oxygen rich blood from the heart to the body

capillaries

microscopic vessels that lie between and connect arteries and veins

circuits

closed pathways of blood flow

pulmonary circuit

sends oxygen poor blood from the heart to the lungs to unload and pick up more oxygen, which is then carried back to the heart and further distributed

systemic circuit

sends oxygen rich blood from the heart to the body and removes waste, which it brings back to the heart

average heart size

around 14 cm long and 9 cm wide

heart location

the heart is located in the mediastinum right above the diaphragm, bordered by a lung on each side

apex

the bottom point of the heart; located left of the sternum at the level of the 5th rib or intercostal space

base

the broad, top end of the heart, attached to large vessels; located beneath the 2nd rib or intercostal space

pericardium

membranous sac that encloses the heart + proximal ends of the attached vessels (only covers the heart, not classified as the wall of the heart itself)

fibrous pericardium

outermost layer of the pericardium, composed of dense connective tissue; also connects to the diaphragm, sternum, vertebral column, and large attached blood vessels

visceral pericardium

innermost layer of the pericardium, covers the heart directly; also classified as the epicardium (the outermost layer of the wall of the heart)

parietal pericardium

the visceral pericardium turns in on itself and to form a double layer that attaches to the fibrous pericardium; this inner layer is the parietal pericardium

pericardial cavity

small space between the visceral and parietal pericardium; contains serous fluid secreted by the parietal pericardium, which reduces friction between the pericardial membranes as the heart moves

pericarditis

inflammation of the pericardium, often due to infection

heart wall structure

composed of 3 distinct layers

epicardium

the outermost layer of the heart wall, also one with the visceral pericardium; serous membrane that consists of connective tissue covered by epithelium; adipose tissue is found in the deeper portion around arteries and veins

myocardium

thick, middle layer of the heart wall; composed mostly of cardiac muscle tissue

endocardium

innermost layer of the heart wall; composed of epithelium and connective tissue (elastic and collagen fibers), also contains blood vessels and Purkinje fibers (specialized cardia muscle fibers)

atria (atrium)

the two upper chambers of the heart; have thin walls and function in receiving blood returning to the heart

auricles

small, hollow projections or extensions at the top of the atria, one in each; increase the blood volume capacity of the atria

ventricles

the two lower chambers of the heart; thicker muscular walls, function in receiving blood from the atria and contracting to force blood out into arteries

septum

thick wall of cardiac muscle that separates the left atrium and ventricle from the right

atrioventricular valve

one each between the atria and their respective ventricles; ensures a one way blood flow from the atria to the ventricles

vena cava

large vein that drains into the right atrium

coronary sinus

cardiac veins drain into this sinus, which then drains into the right atrium

tricuspid valve

large valve that has three projections called cusps; lies between the right atrium and right ventricle; permits blood to move from the atrium to the ventricle, and also prevents back flow

papillary muscles

small mounds of cardiac muscle that project inward from the ventricles

chordae tendineae

strong, fibrous strings attached from the papillary muscles to the cusps of the valve from the ventricular side

right ventricle function

when the right ventricle contracts, the blood inside is put under increasing pressure, causing the tricuspid valve to close, and the blood to be pushed through the pulmonary valve, the only other available exit

pulmonary valve

valve that leads from the right ventricle to the pulmonary trunk

pulmonary trunk

vessel leaving the heart that divides to from left and right pulmonary arteries

pulmonary arteries

two arteries that lead to a lung each

left atrium function

the left atrium receives blood from the lungs through four pulmonary veins, two from each lung; the blood passes from the left atrium to the left ventricle through the mitral valve

mitral/bicuspid valve

prevents back flow from the left ventricle into the left atrium during ventricular contraction

left ventricle contraction

contraction of the left ventricle leads to the mitral valve closing, leaving the aortic valve as the only exit for the pressurized blood

aortic valve

valve at the base of the aorta, consisting of three cusps; opens and allows blood to leave when left ventricle contracts; closes and prevents back flow when the left ventricle relaxes

semilunar valves

the pulmonary and aortic valves, due to their cusps having a half moon shape

skeleton of the heart

rings of dense connective tissue that surround the ends of the pulmonary trunk and aorta, along with masses of dense connective tissue in the interventricular septum

blood flow cycle

the vena cava drains oxygen poor blood that has circulated through out the whole body into the right atrium → the blood passes through the tricuspid valve → the blood enters the right ventricle → the still oxygen poor blood gets pumped through the pulmonary valve → the blood passes through the pulmonary trunk and arteries into the lungs → the metabolic waste in the blood gets discarded and clean oxygen gets picked up from the lungs → the newly oxygen rich blood flows the 4 pulmonary veins into the left atrium → the blood flows pumps through the mitral valve → the blood enters the left ventricle → the blood gets pumped through the aortic valve into the aorta- the arterial branches carry the blood through out the body and distribute the oxygen → the blood passes through the venous system and picks up metabolic waste → the venous system carries the blood back to the heart → the cycle starts over anew

right and left coronary arteries

the first two branches of the aorta, branching right above the aortic valve; supply blood to the tissues of the heart

coronary artery blood flow

blood flow to the coronary arteries increases during ventricular relaxation, due to the myocardial blood vessels not being compressed as they are during contraction; the opened aortic valve during contraction also blocks the openings of the coronary arteries

anastomoses

connections between smaller branches of coronary arteries and vessels; provide alternate pathways for blood when a coronary artery is blocked

cardiac veins

drain the oxygen poor blood that has passed through the myocardial capillaries

sequence of heart contractions

the atria contract while the ventricles relax, then the ventricles contract while atria relax, following is a brief relaxation period of all chambers

systole

contraction phase of heart

diastole

relaxation phase of heart

cardiac cycle

one complete heartbeat, including contraction and relaxation of all chambers

functional syncytium

a group of cells acting as one unit; two functional syncytiums in the heart

atrial syncytium

functional group of cells in the atrial walls

ventricular syncytium

functional group of cells in the ventricular walls

specialized cardiac cells

cells that have few myofibrils, and function not in contracting but generating and sending impulses

cardiac conduction system

specialized cells that coordinate the events and timing of the cardiac cycle

sinoatrial/SA node

(aka pacemaker) small mass of specialized cardiac tissue located in the right atrium near the superior vena cava; initiate and control rhythmic cardiac impulses

atrioventricular/AV node

mass of specialized cardiac tissue located in the lower interatrial septum; serves as a impulse conduction pathway between the atrial and ventricular syncytia

purkinje fibers

large, fast conducting fibers that spread through the ventricles

pathway of a cardiac impulse

SA node → atrial syncytium → junctional fibers → AV node → AV bundle → bundle branches → purkinje fibers → ventricular syncytium

ventricular wall muscles

form in spiral patters, when impulse is reached they contract in a twisting motion

heart beat sound

the lubb-dupp sound of the heart is caused by vibrations of valves closing

first heart sound (lubb)

occurs during ventricular contraction, caused by the AV valves closing

second heart sound (dupp)

occurs during ventricular relaxation, when the pulmonary and aortic valves close

endocarditis

inflammation of the endocardium, which may erode the valvular cusps and result in a heart murmur

average heart rate

70-75 beats per minute in an average adult at rest; normal range of 60-100 bpm

tachycardia

abnormally fast heart rate, more than 100 bpm at rest

bradycardia

abnormally slow heart rate, less than 60 bpm at rest

parasympathetic action on heart

released by the medulla oblongata, decrease heart rate; inhibition of parasympathetic impulses increases heart rate

acetylcholine

neurotransmitter released by parasympathetic impulses that slows heart rate

sympathetic action on heart

secrete neurotransmitter norepinephrine, which increases heart rate and contraction strength

baroreceptor reflex

upon detecting change in blood pressure, baroreceptors send a signal to the cardiac center of the medulla oblongata, which responds accordingly to balance the blood pressure back to normal levels

hyperkalemia

an excess of potassium ions in the blood, decreasing heart rate and contraction force

hypokalemia

low potassium ions in blood, causes abnormal rhythm

hypercalcemia

excess of blood calcium ions, increasing heart action

hypocalcemia

less blood calcium ions, decreases heart action

blood vessels

closed circuit of tubes that carry blood to and from heart

artery

strong vessels that transport blood away from heart under high pressure

arteriole

smaller vessels branched from arteries

structure of artery

consists of 3 main layers

tunica interna

innermost layer of an artery, composed of simple squamous epithelium (endothelium) and a connective tissue membrane of elastic and collagen fibers

tunica interna function

prevents blood clotting by having a smooth surface and secreting biochemicals that inhibit platelet aggregation; can help regulate local blood flow by secreting substances that dilate or constrict blood vessels

tunica media

middle, biggest layer of the artery wall, includes smooth muscle cells and a thick layer of elastic connective tissue

tunica externa

thin outermost layer of artery wall, relatively thin and consists mostly of connective tissue with irregular elastic and collagen fibers; attaches the artery to the surrounding tissues

vasomotor fibers

stimulate vessel smooth muscle to contract, reducing diameter of the vessel and lessening blood flow

vasoconstriction

constricting of blood vessel, stimulated by vasomotor fibers; lessens blood flow

vasodilation

relaxation of blood vessel, in the absence of vasomotor fiber stimulation; greater blood flow

arteriole wall structure

have 3 layers similar to arteries; small arterioles consist only of endothelial lining, rings of smooth muscle cells, and connective tissue

capillaries

smallest blood vessels that branch from the smallest arterioles and venules; thin walls consist of layer of endothelial cells; semipermeable to certain substances via the thin slits between cells

capillary density

structures that use a lot of oxygen and nutrients are abundant in capillaries; structures that use less have fewer or no capillaries; reflects tissues’ rates of metabolism

capillary metabolism rate

higher metabolism = higher capillary density; slower metabolism = lower capillary density