Thorax - Part 5 - Heart

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TheHeart[Topography[Pericardium[Chambers[Structurallayers[Circulationofheart[Electricalconduction[Heartsounds[Clinicalanatomy

Canine- lateralthorax

1

2 3

4

1) Right Atrium 2) Right Ventricle3)Left Atrium4)Left Ventricle
Cranial End
Trachea
Bifurcation of the trachea is around the 5th intercostal space
Diaphragm
Crura of the Diaphragm- pillar of muscle (right and left) - diaphgragm originates from the periosteum of the lumbar vertebrae 2/3. It fans out (trefoil shape - peripheral muscle fibers with a tendon/aponeurosis in the middle) and then attaches to the ribs on the periphery. The caval foramen is in the aponeurosis.
Right Lateral Recumbancy.

Positionofheart

Apex right down near the sternum (by xiphoid process). Top is near the tracheal bifurcation.
Heart shifted to the left (somewhat) - greater mass of lungs on the right side (cranial, middle, caudal, accessory).

Cardiactopography

•Heart•Cardiacnotch•Space5-6forcardiocentesis

•Regionsofauscultation

Equine

B/w the third and 6th rib (lateral aspect)
3rd Rib
6th Rib
Cardiac Notch - nothing lies b/w the heart and the ribs in this area. B/w the third and 5th space - is a bit bigger on the right (in dogs)
Lung covering a bit of the heart

Equine

Horse
Notch is a little more cranial - is bigger on the left side than on the right.
1. Outline of the heart2. Basal border of the lungs3. Line of pleural reflection.

line of pleuralreflection

Dog

caudal borderof the triceps

Dorsally at last rib

Crosses at ~9th c-cjunction

Ribs 3-6

Cow

line of pleuralreflection

caudal borderof the triceps 8th costochondral

junction

Last rib

Ribs 3-6

line of pleuralreflection

caudal borderof the triceps

HorseLast rib

8-9th costochondraljunctionRibs 3-6

If you want to listen to the heart or do a pericardiocentesis you gotta do it around the axilla.
Not the same as the costal arch! Is more cranial than that
AKA the costo-diaphragmatic line.
Costodiaphragmatic recess

Theangleoftheheartdiffersbetweenspecies

Species with deeper chests have a more upright heart. Cat in particular have a heart that really leans forward.
Apex
Cranial
Caudal

Relationstotheheart

• Lateral• Lungs,chestwall,phrenicn.

•Cranial• Thymus,lungs,cranialmediastinum

•Caudal• Diaphragm(abdominalviscera)

Dog, left lateral

What is it in contact with?
(innervates the diaphragm)
phrenic n
Cranial mediastinum (thymus, great vessels, sympathetic trunk & vagosympathetic trunk)

Pericardium

1. Heart2. Greatvessels3. Visceralpericardium4. Pericardialspace5. Parietalpericardium6. Fibrouslayer7. Mediastinalpleura8. Sterno-pericardialligament

poPericardium made of two serous membranes sandwiched together.
potential space - may house a few mL of clear/yellowish/slippery fluid.
Visceral pericardium is not seperable from the heart itself.
Mediastinal pleura is the same as the parietal pleura
attaches pericardium to the sternum
poPericardium made of two serous membranes sandwiched together.
potential space - may house a few mL of clear/yellowish/slippery fluid.
Visceral pericardium is not seperable from the heart itself.
Mediastinal pleura is the same as the parietal pleura
attaches pericardium to the sternum

Functionalanatomy

•4chambers,2pumps•Sizevariesbyspecies&fitness•Approx.0.75%BW

•Portalsystems•Oxygenatedblood•Bloodpressure

One side pumps deoxygenated blood around. The other pumps oxygenated blood around.
Arteries - 25 mmHg
Has a capillary bed on each side.
7) hepatic portal system3) hypophyseal portal system.
1. left ventricle2. aortic arch3. brain capillary bed4. thoracic aorta5. liver portal system10. caudal vena cava11. cranial vena cava12. right ventricle13. pulmonary trunk/artery14. lungs15. pulmonary veins
One side pumps deoxygenated blood around. The other pumps oxygenated blood around.
Arteries - 25 mmHg
Has a capillary bed on each side.
7) hepatic portal system3) hypophyseal portal system.
1. left ventricle2. aortic arch3. brain capillary bed4. thoracic aorta5. liver portal system10. caudal vena cava11. cranial vena cava12. right ventricle13. pulmonary trunk/artery14. lungs15. pulmonary veins

The human heart from the ventral (or anterior) aspect

Adapted from Martini, Timmons and McKinley, 2000

Inhumans,leftisleftandrightisright

Pulmonary Artery - only artery pumping deoxygenated blood.
Pulmonary Artery - only artery pumping deoxygenated blood.

LV

cranial

LVRVRV

cranial

Left lateral (Auricular) Right lateral (Atrial)

R Auricle L Auricle R AtriumL Atrium

Right atria is cranialLeft atria is caudalRight ventricle is cranial and to the right. Left ventricle is caudal and to the left. Auricular - blind ended sacs of the atria - lie on the left and right sides of the heart. Interventricular groove on the left side (periconal)Subsinuosal groove on the caudal/right side.
4. paraconal groove with
pulmonary trunk
Right atria is cranialLeft atria is caudalRight ventricle is cranial and to the right. Left ventricle is caudal and to the left. Auricular - blind ended sacs of the atria - lie on the left and right sides of the heart. Interventricular groove on the left side (periconal)Subsinuosal groove on the caudal/right side.
4. paraconal groove with
pulmonary trunk

Right ventricle

Photo: P. F. Flood

Left ventricle

Equineheart- leftside

Equine heartright side

Right atriumLeft atrium

Atrialsurface

Right ventricle
Subsinuosal groove
Left Ventricle
Right ventricle
Subsinuosal groove
Left Ventricle

cranialcranial

Paraconal groove

Conus arteriosus

SA node

Subsinuosal groove

Conus arteriosus is a cone that funnels blood into the artery
Grooves are almost always filled with fat. In the depth there are arteries and veins.
Called it because its beneath the SA node
Coronary groove - filled with fat - seperates the atria from the ventricles - carries the great cardiac vein and other vessels.
Right Atrium
Conus arteriosus is a cone that funnels blood into the artery
Grooves are almost always filled with fat. In the depth there are arteries and veins.
Called it because its beneath the SA node
Coronary groove - filled with fat - seperates the atria from the ventricles - carries the great cardiac vein and other vessels.
Right Atrium

Right ventricle

Left ventricle

= Coronary groove

Paraconal groove

Equineheart,leftview

= Coronary groove

Subsinuosal groove

Equineheart–rightview

Baseofheart

• Ossacordis• Heartvalves• Coronaryvessels

Seperates the atria (above) and the ventricles (below). 1) left atrio-ventricular valve.2) right atrio-ventricular valve. Has Cusps/Leaves - tied down by the heart strings (AKA cordae tendinae)3/4) semilunar valves.3) aortic valve.4) pulmonary valve & arteryBase of the heart is a fibrocartilagenous plate - gives the heart a rigid structure - so right its not uncommon to have bones within the plate called the ossa cordis. The plate has 4 holes in it.
Seperates the atria (above) and the ventricles (below). 1) left atrio-ventricular valve.2) right atrio-ventricular valve. Has Cusps/Leaves - tied down by the heart strings (AKA cordae tendinae)3/4) semilunar valves.3) aortic valve.4) pulmonary valve & arteryBase of the heart is a fibrocartilagenous plate - gives the heart a rigid structure - so right its not uncommon to have bones within the plate called the ossa cordis. The plate has 4 holes in it.

Baseofequineheart,atriaremoved

Right
Left
Cranial
Caudal
Right
Left
Cranial
Caudal

RightAtrium

• Cranial&Caudalvenacava• Intervenous tubercle• Sinusvenarum• Auricularportionwith

pectinate muscles• Coronarysinus• Fossaovalis• Terminalcrest• Azygous v.

• R- horse&dog• L- pig• L&R- ruminants

6 - cranial vena cava - empties into RA4 - caudal vena cava5 - intervenous tubercle8 - terminal crest - the site of the SA node9 - fossa ovale b/w RA and LA - doesn’t let blood from each side to mix. 7 - coronary sinus - empties blood into the RA - where the vast majority from the heart itself is drained back into the RA. Venous openings into all 4 chambers - deoxygenated heart blood is deposited into all the other chambers in the fabesian veins
pectinate muscles in auricles
6 - cranial vena cava - empties into RA4 - caudal vena cava5 - intervenous tubercle8 - terminal crest - the site of the SA node9 - fossa ovale b/w RA and LA - doesn’t let blood from each side to mix. 7 - coronary sinus - empties blood into the RA - where the vast majority from the heart itself is drained back into the RA. Venous openings into all 4 chambers - deoxygenated heart blood is deposited into all the other chambers in the fabesian veins
pectinate muscles in auricles

[ Conus arteriosus[ Supraventricular crest[ RAV valve (tricuspid)[ Cordae tendineae[ Papillary muscles[ Trabeculae carneae[ Trabecula

septomarginalis[ Pulmonary semilunar

valve

Rightventricle(ventralview)

cone shaped part of right ventricle leading into the pulmonary artery
divides the inflow/outflow regions
Ties down valves to the papillary muscles
Septomarginal (muscular) band from intraventricular septum to the free boarder of the ventricle - prevents thin wall of right ventricle from balooning out - also is a short cut for electrical impulses so the entire ventricular wall contracts at the same time.
Trabeculae carneae - irregular spongy look of the heart inside - decreases blood turbulence.
cone shaped part of right ventricle leading into the pulmonary artery
divides the inflow/outflow regions
Ties down valves to the papillary muscles
Septomarginal (muscular) band from intraventricular septum to the free boarder of the ventricle - prevents thin wall of right ventricle from balooning out - also is a short cut for electrical impulses so the entire ventricular wall contracts at the same time.
Trabeculae carneae - irregular spongy look of the heart inside - decreases blood turbulence.

Adapted from Martini, Timmons and McKinley, 2000

Rightventriclelitfromconusarteriosus

•Tendinous cordsandpapillarymuscles

looking up towards the right AV valve
looking up towards the right AV valve

Equineheart,leftview

•pulmonaryarteryandconusarteriosusopened

Paraconal groove
Paraconal groove

A cusp of a semilunar valve

RV

LV

Right&LeftVentricles

•Orientationinsitu•Trabeculae carneae•Wallthickness•Grooves

Paraconalgroove

SubsinuosalGroove

4 - trabeculae carneaeLV much thicker - has to pump blood to the systemic circulation.RV is much thinner.
4 - trabeculae carneaeLV much thicker - has to pump blood to the systemic circulation.RV is much thinner.

Septomarginalband

Sectionoftheventriclesofahorse

Paraconal vessels
Subsinuosal vessels
Paraconal vessels
Subsinuosal vessels

LeftVentricle

• Thick-walled• Chordae tendineae• Papillarymuscles• Trabeculae carneae• Noseptomarginal band• LeftAV

• Bicuspid(“mitral”)• Aorticvalve

• semilunar

“Pope (wears a mitre) is never right”
“Pope (wears a mitre) is never right”

Left atrium

Left ventricle

Papillary muscle

Equineheart,longitudinalsection,leftside

Left AV valve
Left AV valve

Cardiacbloodsupply• 15%ofLVoutputgoestoheart• 80- 100%bloodvolumepassesthroughheart/min.

• Leftcoronarya.• paraconal br.• circumflexbr.• � subsinuosal br.

• Rightcoronarya.• � subsinuosal br.

• Greatcardiacv.• Coronarysinus

Dog heart

Ors Petnehazy, University of Alaska Fairbanks

Caudal view

Left lateral view

drains into coronary sinus
Paraconal Groove
Small thebesian veins drain directly into all 4 heart chambers
Caudal View
drains into coronary sinus
Paraconal Groove
Small thebesian veins drain directly into all 4 heart chambers
Caudal View

= Coronary groove

Subsinuosal groove

Anequineheartseenfromtheright

Coronary Groove
Coronary Groove

The coronary sinus entering

the right atrium

CoronaryVessels

horse

Right Coronary Artery (supplies righ subsinuosal groove)
Right Coronary Artery (supplies righ subsinuosal groove)

Cardiacbloodsupply

horse

Cardiac Vein
Left Coronary Artery
Right Coronary Artery
Cardiac Vein
Left Coronary Artery
Right Coronary Artery

Rt. Lat. view

Ruminants&Carnivores

• Greatcardiacv.® coronarysinus

• Leftcoronarya.®Paraconal®Circumflex®Subsinuosal

• Rightcoronarya.small

Rt. Lat. view

Horse&Pig

•Leftcoronarya.•Paraconal•Circumflex

•Rightcoronarya.®Subsinuosalbr

•Great&middlecardiacv.•Coronarysinus

Thedistributionofthecoronaryarteriesdiffersbetweenspecies

PF Flood1994

Blockage of the coronary arteries is not tolerated very well - doesnt take long to damage the muscles (myocardial infarcation)
Blockage of the coronary arteries is not tolerated very well - doesnt take long to damage the muscles (myocardial infarcation)

ConductingSystem

•Sinuatrialnode•pacemaker

•Atrioventricularnode•Delaysimpulse

•Atrioventricularbundles•2limbs

•Septomarginal(moderator)band• short-cut

just dorsal to the hole in the fibrocartilagenous plates.
3. Purkinje Fibers
Purkinje Fibers
No delay @ AV node - contraction of atria/ventricles will contract at the same time - no inflow of bloodinto the ventricle chambers
just dorsal to the hole in the fibrocartilagenous plates.
3. Purkinje Fibers
Purkinje Fibers
No delay @ AV node - contraction of atria/ventricles will contract at the same time - no inflow of bloodinto the ventricle chambers

From König and Liebich, 2004

Theleftatrioventricularbundle

Ventricularcontraction

• Right:bellows• Left:radial&shortening• AVvalvesclose• A&Pvalvesopen

Right ventricle wraps around the front and contracts against the left ventricle. The left ventricle contacts more during a circular fashion.
During diastole - there is very little pressure on the inflow to the ventricles. Venous pressure exceeds the low ventricular pressure. The beginning of filling is passive. At the end of diastole the atria contracts (tops up the volume in the ventricle). Eventually the ventricle will contract - pushes AV valve shut - pressure is high and leaves out the semilunar valves.
Right ventricle wraps around the front and contracts against the left ventricle. The left ventricle contacts more during a circular fashion.
During diastole - there is very little pressure on the inflow to the ventricles. Venous pressure exceeds the low ventricular pressure. The beginning of filling is passive. At the end of diastole the atria contracts (tops up the volume in the ventricle). Eventually the ventricle will contract - pushes AV valve shut - pressure is high and leaves out the semilunar valves.

Heartsounds

4sounds(butusuallycanonlyhear2):S1- “lub”=closureofAVvalves

• AtonsetofventricularsystoleS2- “dub”- closureofaorticandpulmonaryvalves

• Atonsetofventriculardiastole• Higherpitchedsound

S3- ventricularfillingduringdiastole• passive

S4- atrialsystole- morecommonlyheardinhorse

(or at the end of ventricular systole)
(or at the end of ventricular systole)

CardiacMurmurs

• Murmurs=audibleturbulencebetweenheartsounds

• Grade1to6• Systolicmurmur

• InsufficiencyofAVvalves(regurgitation)

• Stenosisofsemilunars• Ventricularseptal defect• PDA

• Diastolicmurmur• Insufficiency

• aortic- uncommonindogs,commoninoldhorses

• Pulmonary- rare

lub-shhh-dub
lub-shhh-dub

The base of an equine heart, atria removed

LA

P

Dog- puncta maxima

P - pulmonary valve - 3rd rib spaceA - aortic valve - 4th rib spaceL - Left AV valve - 5th rib space

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