cardiovascular system

where is the heart located?

mediastinum

how is the base of the heart angled?

craniodorsally

how is the apex of the heart angled?

caudoventrally

the heart is tilted towards the ____ of the body

left

what is included in the cardiac covering?

pericaridum — pericardial sac/fibrous pericardium, serous pericardium, & pericardial space/cavity

what are the 2 layers of the serous pericardium?

parietal & visceral

pericardial sac/fibrous pericardium

thick outer layer of the heart; very tough

parietal layer of serous pericardium is located…

just underneath the fibrous pericardium

visceral layer of serous pericardium is also called…

epicardium

visceral layer of serous pericardium is located…

mashed/glued into the myocardium

pericardial space/cavity

separates the parietal & visceral layers of the serous pericardium; filled with pericardial fluid

pericardial fluid function

lubricates & facilitates movement of the heart; allows inner portions of the heart to contract & relax freely

pericardial effusion

excessive amount of pericardial fluid, causing the heart to struggle to beat

myocardium

middle & thickest layer (making up most of the heart); composed of muscle

which side of the heart has a thicker myocardial wall?

left side

endocardium

inner (layer) surface of myocardium; lines chambers of heart, covers valves & papillary muscles

the endocardium is continuous with…

blood vessel endothelium (inner most layers of vessels)

autorythmic

has the ability to generate its own impulses without the nervous system

how many chambers are there in the heart?

4

what do the 4 chambers of the heart consist of?

2 atria & 2 venticles

atria

receives blood (takes blood into the heart)

interatrial septum

separates the left & right atria

the SA (sinoatrial) node is located in which atrium?

right

auricles

anterior portion of each atrium; wrinkled, flap-like extensions; atria are located beneath

ventricles

export blood (push blood out of the heart)

interventricular septum

wall that separates left & right ventricles

interventricular groove

dent on the outside of the heart that indicates where left & right ventricles are; contains coronary vessels & fat

atroventricular septum

interventricular & interatrial septum together

there are 4 valves in the heart, & blood can only go…

in 1 direction

which valve is between the right atria & right ventricle?

tricuspid valve (right AV valve)

which valve is between the left atria & left ventricle?

mitral valve/bicuspid valve (left AV valve)

mitral valve disease

most common heart disease in canines

chordae tendonae

collagen fibers attached to papillary muscles; attach to AV valves to help with valvular opening & closing

which valve is between the right ventricle & pulmonary artery?

pulmonary valve (a semilunar valve)

which valve is between the left ventricle & aorta?

aortic valve (a semilunar valve)

functions of dense fibrous tissue rings

separate atria & ventricles

anchors valves

provides attachment point for myocardium

provides electrical insulation between atria & ventricles

coronary arteries

branch from aorta & encircle the heart; brings oxygen rich blood to the myocardium

coronary veins

return to the coronary sinus directly into the right atrium; takes used blood from the myocardium & dumps into the right atrium through the coronary sinus

heart uses outside nerve stimulation in…

fight, flight, freeze, or fawn situations

steps of blood flow on the right side of the heart

1. oxygen depleted blood coming from body goes through the cranial & caudal vena cava & enters the right atrium

2. when right atrium is full, blood passes through the tricuspid valve & enters the right ventricle

3. once right ventricle fills, blood passes through pulmonary valve, into the pulmonary artery & goes to the lungs (to pick up oxygen)

steps of blood flow on the left side of the heart

1. from the pulmonary veins, oxygen rich blood enters left atrium & passes through the mitral valve once full, entering the left ventricle

2. once left ventricle fills, blood exits through aortic valve & into the aorta

3. oxygen rich blood is then sent out to the rest of the body

pulmonary arteries contain…

deoxygenated blood

pulmonary veins contain…

oxygenated blood

depolarization

consists of 2 events

1. sodium & calcium ions move from the exterior to the interior of the cell wall through channels (reverses polarity of cell wall)

2. potassium ions move through channels from the interior of the cell membrane to the exterior (restores polarity of cell wall)

repolarization

return of sodium, calcium, & potassium to their original locations via channel pumps (cell is now ready to depolarize again)

LUB

sound of the closing of tricuspid & mitral valve after atrial systole

DUB

sound of the closing of pulmonary & aortic valves after ventricular systole

murmurs

audible sound; signals turbulent flow of blood in the wrong direction

in order for cardiac muscle cells to contract, it must…

depolarize

cardiac conduction consists of…

sinoatrial node (SA node)

atrioventricular node (AV node)

bundle of His

right & left bundle branches

purkinje fibers

steps of cardiac conduction

1. impulse for cells begin contraction generated from SA node

2. translated signal goes to the atrioventricular node (AV node) to bundle of His (delays slightly to give ventricles time to fill)

3. signal from bundle of His goes down left & right bundle branches which then travel to the purkinje fibers

4. apex first facilitates ejection of blood (goes from apex, up & out).

systole

contraction of myocardium

diastole

relaxation of myocardium

although each chamber goes through systole & diastole, but not…

simultaneously

when at rest, cardiac muscle cells are…

polarized

inside of the cell is more ____ charged, & the outside is more _____

negatively; positive

potassium ions are located…

inside of the cell

sodium & calcium ions are located…

on the outer membrane of the cell

cardiac output (CO)

volume of blood ejected from the left ventricle per unit of time

cardiac output is determined by what 2 factors?

heart rate & stroke volume

heart rate

how many times the heart beats per minute

stroke volume

volume of blood ejected from the left ventricle during 1 contraction

stroke volume is determined by what 2 factors?

preload & afterload

preload

volume of blood the ventricle receives from the atrium; 80% by gravity, 20% by atrial systole

afterload

physical resistance presented by the artery the ventricle is pushing blood into

formula to determine cardiac output

stoke volume (SV) x heart rate (HR)

what are the 3 main layers of vessels?

endothelium, smooth muscle, & connective tissue

compared to veins, arteries have a ______ muscle layer & connective tissue

thicker

arteries are more ______ & _______compared to veins

narrow, thinner

arteries are protected by _______, & are set further away from the skin

soft tissue

arterioles

small arteries

why is the aorta more elastic?

because it is taking a large volume of pressure from the left ventricle

why are arterioles more muscular?

in order to keep vessels constricted to keep blood pressure adequate

veins are capable of fluid exchange, meaning what?

fluids can diffuse in & out (from intravascular space to the interstitial space)

venules

small veins

check valves (located in veins)

blocks blood from going back down & allowing blood to fight against gravity

pulse

rate of alternating stretching & recoiling of the elastic fibers in an artery with each heartbeat

blood pressure is dependent on what factors?

heart rate, stroke volume, total blood volume, & elasticity & diameter of artery

foramen ovale

opening in between the 2 atria, allowing them to communicate with one another

ductus arteriosus

opening in between the pulmonary artery & aorta, allowing the blood to come back down into the heart, rather than into the lungs

patent foramen ovale (PFO)

occurs when the foramen ovale does not close after birth

patent ductus arteriosus (PDA)

occurs when the ductus arteriosus does not close after birth; more common (especially in small dogs)

electrocardiography (ECG/EKG)

measure of electrical stimulus produced by the heart on the surface of the patient

P wave

time it takes for the wave of depolarization to travel from SA node across the atria; corresponds to atrial contraction in healthy patients

QRS complex

ventricular depolarization & contraction

Q wave

depolarization of interventricular septum

R wave

depolarization of main mass of ventricles

S wave

depolarization of final part of the ventricle near base of heart

T wave

ventricular repolarization & relaxation; time taken by ventricles to get ready for the next contraction by refilling with blood from atria

where is blood drawn from felines?

jugular vein, cephalic vein, femoral vein

where is blood drawn from canines?

jugular vein, cephalic vein, saphenous vein

where is blood drawn from bovines?

jugular vein, coccygeal vein