CH 19 - The Heart

the heart is a

muscular double pump

the heart has two functions

pulmonary circuit and systemic circuit

pulmonary circuit

right side receives oxygen-poor blood from the body and pumps it to the lungs

systemic circuit

left side receives oxygenated blood from the lungs and pumps throughout the body

atrium

receive blood from the pulmonary and systemic circuits

ventricles are

the pumping chambers of the heart

healthy heart typically weighs

250-350 grams

the heart is the largest organ of the

mediastinum

• located between the lungs

apex lies to the

left of the midline

heart is the

broad posterior surface

heart coverings - pericardium layers

fibrous and serous

fibrous pericardium

strong layer of dense connective tissue

serous pericardium

formed from two layers

• parietal and visceral layer

layers of the heart wall - epicardium

visceral layer of the serous pericardium

layers of the heart wall - myocardium

• consists of cardiac muscle

• muscle arranged in circular and spiral patterns

layers of the heart wall - endocardium

• endothelium resting on a layer of connective tissue

• lines the internal walls of the heart

walls differ in

thickness

atria has

thin walls

ventricles have

thick walls

systemic circuit is longer

than pulmonary circuit

• offers greater resistance to blood flow

left ventricle is 3x

thicker than right ventricle

• exerts more pumping force

left ventricle flattens

right ventricle into a “crescent shape’

right atrium forms

right border of heart

right atrium receives

oxygen-poor blood from systemic circuit

right atrium receives oxygen-poor blood from systemic circuit though these vessels

superior and inferior vena cava, coronary sinus

coronary sinus is a collection of

veins joined together to form a large vessel that collects blood from the heart muscle

• delivers less-oxygenated blood to the right atrium

right atrium - pectinate muscles

muscular ridges found in the walls of the heart’s atria, named for their resemblance to the teeth of the comb

right atrium - fossa ovalis

depression in interatrial septum; remnant of foramen ovale

right ventricle receives blood from right atrium through

the right AV valve (tricuspid valve)

right ventricle pumps blood into

pulmonary circuit via the pulmonary trunk

internal walls of the left and right ventricle

• trabeculae carneae

• papillary muscles

• chordae tendineae

pulmonary semilunar valve located

at opening of right ventricle and pulmonary trunk

left atrium makes ups

heart’s posterior surface

left atrium receives oxygen

rich blood from lungs through pulmonary veins

left atrium opens int the left ventricle though

left AV valve (bicuspid or mitral valve)

left ventricle forms

apex of the heart

left ventricle pumps blood through systemic circuit via

aortic semilunar valve

AV valves =

entrance valves

AV valves are valves within your heart to

keep your blood moving the right way

two AV valves -

tricuspid and mitral/bicupside

two semilunar valves -

pulmonary and aortic

• contain 3 cusps shaped like crescent moons

tricuspid valve location

right atrium to right ventricle

mitral/bicupsid valve location

left atrium to left ventricle

aortic valve location

between left ventricle and aorta

pulmonary semilunar valve location

between right ventricle and pulmonary artery

heart sound

• Lub-dup

  • sound of valves closing

first sound - lub

the AV valves closing

second sound - dup

the semilunar valves closing

each valve sound is best heard near a

different heart corner

heart sounds - superior left corner

pulmonary valve

heart sounds - superior right corner

aortic valve

heart sounds - at the apex

mitral/bicupsid valve

heart sounds - inferior right corner

tricuspid valve

stenosis

narrowing, especially of opening of valved

valve disorders - causes

genetic and congenital abnormalities, inadequate blood supply (heart attack), bacterial infection (endocardium)

valve disorders - “leaky” (incompetent)

produce a distinct sound when the valve closes

valve disorders - “narrowed openings” (stenosis)

occurs when cusps are fused or stiffened by calcium deposits

valve disorders “stenoic” valves

produce a distinctive “click” sound during ventricular systole as blood passing the constricted opening becomes turbulent and vibrates

open valve - blood returning to the heart fills the

atria, pressing against the Av valves

open valve - the increased pressure forces

AV valves open

open valve - as ventricles fill, AV valve flaps hang

limply into ventricles

• atria contract, forcing additional blood into ventricles

AV valves open; atrial pressure

greater than ventricular pressure

closed valve - ventricles contract, forcing

blood against AV valve cusps

• AV valves close

closed valve - papillary muscles and chord tendineae

contract and tighten, preventing valve flaps from everting into atria

AV valves closed; atrial pressure

less than ventricular pressure

semilunar valve open - as ventricles contract and intraventricular pressure rises,

blood is pushes against semilunar valves, forcing them open

semilunar valves closed -

as ventricles relax and intraventricular pressure falls, blood flow back from arteries, filling the cusps of semilunar valves and forcing them to close

blood flow through heart - beginning with oxygen-poor blood in

superior and inferior vena cava

blood passes through all

structures sequentially

• atria contract together; ventricles contract together

heartbeat -

sequence of atrial contractions and ventricular contractions which propels blood through the heart

systole -

chamber contraction

diastole -

chamber filling with blood

cardiac muscle tissue forms the

myocardium

cardiac muscle is

striated, like skeletal tissue

contractions pump

blood through the heart and into the blood vessels

cardiac muscle contracts by

sliding filament mechanism

cardiac muscle cells

short, branching, have one or two nuclei, not fused colonies

cardiac muscle tissue - cells joint at

intercalated discs

• complex junctions

• form cellular networks

cardiac muscle tissue - cells are separated by

delicate endomysium

• binds adjacent cardiac fibers

• contrains blood vessels and nerves

intercalated discs - complex junctions

adjacent sarcolemmas interlock

intercalated discs possess three types of cell junctions

• desmosomes

• fasciae adheres - long desmosome-like junctions

• gap junctions

cardiac muscle tissue triggered to contract by

Ca2+ entering the sarcoplasm → signals sarcoplasmic reticulum to release Ca2+ ions → ions diffuse into sarcomeres → trigger sliding filament mechanism

cardiac muscle tissue - not all cardiac cells are

innervated

• will contract in rhythmic manner without innervation

  • inherent rhythmicity → basis for rhythmic heartbeat

cardiac muscle tissue has intrinsic ability to

• generate and conduct impulses

• signal these cells to contract rhythmically

conduction system

a series of specialized cardiac muscle cells

sinoatrial (SA) node sets

the inherent rate of contraction

conduction system - From the SA node

internodal pathway to the AV node

internal pathway to the AV node

AV node to the AV bundle → AV bundle to the bundle branches → bundle branches into the subendocardial conducting network (purkinje fibers)

heart rate is set

by SA node

rate is altered by

extrinsic and neural controls

• visceral sensory fibers and parasympathetic fibers

nerves pass through

cardiac plexus

innervation - parasympathetic fibers

• branches of vagus nerve

• decreases heart rate

• restricted to

  • SA node, AV node, coronary arteries

innervation nerves

• increase heart rate and strength of contraction

• travel to heart from cervical and upper thoracic chain ganglia

• innervate:

  • SA node, AV node, coronary arteries, cardiac musculature throughout the heart

autonomic input controlled by

cardiac center in reticular formation of medulla

• cardioinhibitory and cardioacceleratory center

cardioinhibitory center influences

parasympathetic neurons

cardioaccelaeratory center influences

sympathetic neurons

coronary arteries supply

oxygenated blood to the heart muscle

cardiac veins

drain the deoxygenated blood from the heart

coronary artery disease (CAD) -

arteries supplying heart wall are narrowed or blocked

atherosclerosis

fatty deposits, leads to CAD