UNIT 17-19 The Heart

unit 2 of 2nd semester

FACTS

• weights under 1lbs

• size = fist

• in mediastium cavity

• sits left of sternum

• apex points to left hip

2 pumps feeding

pulmonary (lungs) circuit & systemic circuit

pulmonary (lungs) circuit

gets deoxy blood (increase CO2) from body into right side of heart. then is pumped to lungs. At lungs (CO2 decrease and O2 increases). then returns Left of heart. (blood is now oxy)

systemic circuit

L. side of heart gets oxy blood and pumps out to rest of body. deoxy blood returns to R. side of the heart

# arteries leave heart; veins return to heart

ATRIA (RL)

2 recieving chambers

VENTRICLES (RL)

2 pumping chambers (lower)

Coverings:

• fibrous pericardium sac

• serous pericardium (2) (parietal and visceral)

serous pericardium (2) (parietal and visceral)

• parietal membrane is stuck on inside of fibrous pericardium

• visceral membrane covers heart like plastic wrap

in btwn fibrous pericardium & visceral membrane is…

pericardial cavity filled w/ fluid to reduce friction

3 layers of heart wall

epicardium, myocardium, endocardium

(1) epicardium layer

actually visceral membrane

(2) myocardium layer

cardiac muscle

(3) endocardium layer

lines chamber and vessels

grooves on surface house the…

coronary vessels that feed the heart itself

interatrial septum

btwn atria

interventricular septum

btwn ventricles

ATRIA

“entry way“ -> receive blood

R. arium

receives deoxy blood from body thru 3 veins:

• superior vena cava, inferior vena cava

• coronary sinus

L. atrium

receives oxy blood from lungs thru 4 veins:

• 2 left pulmonary veins

• 2 right pulmonary veins

auricles

“pouches“ on surface of atria which allows for increase in volume

ventricles

• “belly“ discharging chamber (lower)

• make up most of heart volume

ventricles (RL)

• L side = thicker wall due to pumping blood into aorta (largest artery) to all body

• R sits more anterior. L sits more posterior

• R ventricles pumps into pulmonary truck (with an artery) & feeds deoxy blood to lungs

• L ventricles pumps into aortic artery & feed to body oxy blood

trabeculae coneae

muscular ridges that give structure

papillary muscles

connect tendons to values

chordae tendons

tendons

2 atriaventicular values (AV values)

R - tricuspiad

L - bicospid = mitral valve

• each cusp connects to chordae tendonae and papillary muscle

as ventricles contract and move blood into the arteries…

pap. muscles contract & tighten tendons to hold atria valves in place so blood doesn’t enter into atria

1 aortic semilunar value is where?

at base of aorta

1 pulmonary valve is where?

is at base of pulmony trunk

the SL values have no

pap muscles and tendons

in the valves…

the valve cups close and prevents backflow

Cardiac Conduction System (POGIL) Begins

in right atrium at sinoatrial mode (SA)

• group of specialized cells that self propogate action potentials

• creates synus rythm (heart beat)

Cardiac Conduction System (POGIL) Then

on to AV node - here the communication is halted to allow atria contraction before ventricles contract

Cardiac Conduction System (POGIL) Next

AV bundle in interventricular septum initiates ventricle contractions.

continues down septum to L/R bundle branches to apex

Cardiac Conduction System (POGIL) Last

the Purkinje fibers (subendocardial conducting network) radiate throughout ventricles

Electrocardiogram (ECG or EKG)

• measures the hearts electrical activity w/ each beat

depolarization

electrical activity that triggers heart chamber contractions (SYSTOLE)

repolarization

electrical activity that triggers heart chamber relaxations (DIASTOLE)

letter waves

P- depolarization at atria

QRS- depolarization ventricles

T- repolarization of ventricles

• repolarization at atria are masked by QRS

arrhythmia

irregular heart rhythm (tachycardia and Bradycardia)

tachycardia (over 100 beats/min)

exercise induced = good

TYPES:

• fibrillation - chaos, SA node loses control

• use AED (automatic external defibrillator) because it uses a shock to restart SA Node

• flutter = more organized than Fib. but still very rapid

Bradycardia (< 60 beats/min)

• a fit person can be <60 and healthy

• as we age the electrical activity can be disrupted and need a PACEMAKER (to monitor SA node)

Heart Sounds (auscultation) “LUB“ 1st

blooding pushing against the closed AV valves during ventricular systol

Heart Sounds (auscultation) “DUB“ 2nd

blood in aorta and pulmonary pushing back on closed SL valves when ventricles are in diastole

cardiac cycle - all the P and V

• involved in 1 heart beat

• cardiac output - V of blood leaving per/min ~ 75 b/min

• beats/min * mL/b = mL/min

• 75 b/min * 70mL/b = 5250 mL/min = 5.25L

congestive failure

pumping efficiency of heart cannot over blow circulation needs?? look at lecture

arteries/veins outer layer

• tunica externa (connective tissue)

arteries/veins middle layer

tunica media (smooth muscle/elastin)

arteries/veins inner layer

• tunica intima (endothelial cells)

ARTERIAL SYSTEM Elastic (aorta) arteries

• aorta and other big branches

• lots of elastin to create reservoirs and recoil

ARTERIAL SYSTEM Muscular (Distributis)?? arteries

• smaller

• feeding into organs

• lots of smooth muscle

Arterial System Artericles

• smaller

• feeding into capillary beds

capillaries

• smallest vessels

• one layer thick - endothelial

• site of gas, nutrient and waste exchange

• form “beds“

• have precapillary sphincteus that controls flow blood

• 1 RBC at a time

VENOUS SYSTEM (venules)

• smallest; located on other side cap.bed

  • “leaky“ - fluid and WBC can enter interstitial space

VENOUS SYSTEM (veins)

• larger than venules

• biggest lumen (opening)

• little smooth and elastin

• have valves (prevents backflow)

• bad valves - varicose veins: dilated veins due to leaky valves

Arterial Blood Pressure - force exerted on an artery wall

120mmHg: Systolic Pressure (<120). Ventricular contraction forcing blood into aorta

80mmHg: Diastolic Pressure (<80). After the semi lunar aortic valve closes and L vent is relaxed and aorta recoils

Blood pressure is measured w/Sphygmoanometer

high BP = Hypertension

pulse

created by alternating stretch and recoil of arteries during a cardiac cycle.