structure of heart

how many ribs and ICS does a horse have?

18 ribs, 17 ICS

how many ribs and ICS does a dog have?

13 ribs, 12 ICS

what is the general location of the heart?

3rd to 6th rib; 3rd to 5th ICS

how is the heart oriented in dogs and cats?

obliquely oriented

how is the heart oriented in horses and ruminants?

located more ventrally; the apex makes more contact with the sternum

what supports the apex of the heart in dogs and cats?

phrenicopericardiac ligament

what supports the apex of the heart in horses and ruminants?

sternopericardiac ligament

what is the function of the phrenicopericardiac ligament?

short strong band of connective tissue that firmly attaches the pericardium to diaphragm to provide support

In mammals, how is the apex of the heart oriented?

slightly to the left side

in horses and ruminants where may the heart begin?

heart may be pushed more forward towards 2nd rib

when the heart is obliquely oriented, what will it make more contact with?

diaphragm

what is another word for ribs?

thoracic vertebrae

In a horse, the base of the heart is located more…

dorsally

In a horse, the apex of the heart is…

not as forward, oriented more vertically

In the dog, the apex of the heart is located more…

caudal and ventral

in the dog, the base of the heart is located more…

cranially and dorsally

where are the great vessels located?

present at the base of the heart

which of the great vessels will take blood AWAY from the heart?

aorta and pulmonary trunk

which of the great vessels will bring blood back to the heart?

cranial and caudal vena cava

which species will have cardiac notches present on both sides of the pulmonary tissues?

horses

what portion of the heart will the trachea make contact with?

base of the heart

what side will the cardiac notch be present in the dog?

only on the right side

what is a cardiac notch?

area where heart makes direct contact with the body wall due to the thinner pulmonary tissue layer

what side is the cardiac notch present in dogs?

prominent on right, small impression on the left side

why do we listen for the heart on the left side of the animal?

1. apex on left side

2. thinner pulmonary tissue present on left lung = left muffled sound

carina

cartilagenous ridge where the trachea ends and will bifurcate into 2 larger branches

what does a shift in the carina indicate?

shift in location can indicate if heart has changed in size

if the heart was larger, where would you expect the carina to shift towards?

dorsal and slightly more upward

what are the two branches of the carina?

1. right primary bronchus

2. left primary bronchus

what are the larger blood vessels supporting heart at its base?

1. caudal vena cava

2. cranial vena cava

where is the esophagus located in relation to the heart?

base of the heart

what do we call it when the middle mediastinum pleura makes contact with the heart?

pericardial pleura

what is the order of mediastinum from cranial to caudal in the thoracic cavity?

1. cranial mediastinum pleura

2. middle mediastinum pleura

3. caudal mediastimun pleura

how many layers composes the outer covering of the heart?

3 layers

visercal pericardium of the heart is also known as…

epicardium

epicardium

the layer that covers the heart wall, practically inseparable from the heart wall

parietal pericardium of heart

the outer layer which is attached to the mediastinum

pericardial cavity of the heart

space between visceral and parietal pericardium containing small amount of serous fluid

fibrous pericaridum

fibrous connective tissue which attaches the parietal pericardium to the mediatinal pleura (mediastinum)

why do we need fluid in pericardial cavity?

prevent friction and provide free space to allow heart to contract without interference form other organs

what is the order of layers of the pericardium starting with the heart to outside?

1. heart

2. epicardium

3. pericardial cavity

4. parietal pericardium

5. fibrous pericardium

6. mediastinal/ pericardial pleura

what three layers of the pericardium are tightly attached that when you cut one you cut them all?

1. parietal pericardium

2. fibrous pericardium

3. mediastinal/pericaridal pleura

what is the function of the pericardium?

1. provide isolated environment for heart

2. pericardial fluid function as lubricant

3. prevents overstretching/overdilation of the heart

how does the pericardium prevent overstretching of the heart?

fibrous connective tissue provides toughness and does not allow the heart to expand past a certain limit

which layers are cut to expose the heart wall?

1. parietal pericardium

2. fibrous pericardium

3. mediastinal pleura

atrium

a thin-walled chamber that receives blood

auricle

a blind sac extended from each atrium

ventricle

thick-walled chamber located ventrally that pumps the blood away from the heart

right auricle location and function

extends from upper and front part of right atrium reservoir for blood and contributing to initation of atrial contraction

what structure is responsible for seperating atria from ventricles?

coronary groove

apex

ventral end of the left ventricle

base

thin walled atria

interventricular grooves

separate the ventricles from one another

paraconal interventricular groove

seperates the left and right ventricle externally, provides some space for blood vessels to run through

where will you see the paraconal interventricular groove?

left larteral view

where will you see the subsinuosal interventricular groove?

right lateral view below the coronary sinus to separate the ventricles

conus arteriosus

inverted cone shaped part of the right ventricle where the pulmonary trunk arises

what is the function of the conus arteriosus?

serves as a pathway for blood to exit right ventricle and enter pulmonary trunk

what is the function of the pulmonary trunk?

carry deoxygenated blood to the lungs

what is. the function of the aorta?

carry oxygenated blood supply to the body

ductus arteriosus

a blood vessel in the fetus that shunts blood from pulmonary artery to aorta to bypass the lungs since they are not functional yet

ligamentum arteriosum

small fibrous remnant of ductus arteriosis that serves no function

where does the aorta arise from?

left ventricle

where does the pulmonary trunk arise from?

right ventricle

which of the great vessels will you see on a left lateral view of the animal?

1. aorta

2. pulmonary trunk

which of the great vessels will you see on a right lateral view of the animal>

1. azygos vein

2. cranial vena cava

3. caudal vena cava

what is the function of the cranial and caudal vena cava?

collect deoxygenated blood from the body to return to the heart

what is the function of the azygos vein>

collect deoxygenated blood from the throracic wall to bring back to the right atrium through the vena cava

what internal structure separates the ventricles?

interventricular septa

what internal structure separates the atria?

interatrial septa

what is the purpose of the AV valves?

valves maintain unidirectional blood flow

what are the internal layers of the heart wall?

1. endocardium

2. myocardium

3. epicardium (visceral pericardium)

what type of cells make up the endocardium of the heart wall?

simple squamous endothelium

describe the steps involved in deoxygenated blood to the heart

1. blood enters the heart through the inferior or superior vena cava to the right atrium

2. blood flows across the tricupsid valve

3. blood enters the right ventricle

4. blood ejected to pulmonary artery

5. pulmonary artery splits into 2 vessels, each going to the lung to get oxygenated

describe the steps involved in oxygenated blood flow

1. oxygenated blood returns from lungs to heart via pulmonary artery

2. blood enters left atrium

3. passes through mitral valve

4. enters left ventricle

5. blood ejected to body via aorta

internally, which structure accompany the interventricular grooves?

interventricular septum

the deoxygenated blood from the body and heart returns to which chamber of the heart?

right atrium

what is the function of the intravenous tubercule?

helps prevent turbulence of blood flow between the right atrium and ventricle by preventing blood from cranial and caudal vena cava from running into one another

what is the composition of the chordae tendinae?

composed of collagen and elastic fibers

function of opening-coronary sinus

bring deoxygenated blood to right atrium

what is the function of the chordae tendinae?

connect papillary muscles to AV valves to prevent valves from collapsing into atria during ventricular systole and further prevent back flow of blood

what is the location of the septomarginal band?

a muscular band in the right ventricle that extends from interventricular septum to base of anterior papillary muscle

what is the function of the pectinate muscles?

provide strength for contraction for right auricle

what is the location of the right auricle?

extends from upper front part of right atrium to overlap with root of aorta

what is the function of the right auricle?

increase capacity of right atrium by helping collect and store blood

which contracts and expands more: right atrium or right auricle?

right auricle

fossa ovalis

a shallow depression formed by infoldings of atrial walls; remenant of foramen ovale

forman ovale

fetal circulatory shunt to bypass blood to the lungs; closes within first week of life

what guards the right AV opening?

tricuspid valve

what are the different AV cusps?

1. parietal

2. septal

3. angular

what cusps are associated with the tricuspid valve?

1. angular cusp

2. parietal cusp

3. septal cusp

what type of cusps are associated with the pulmonary valve?

three semilunar cusps

what is another name for pulmonary and aortic valves?

semilunar valves

what is important to understand about semilunar cusps?

do not require chordae tendineae

what are the names of the semilunar cusps?

1. pulmonary sinus

2. nodule

3. lunule

how do the cusps of the pulmonary valve function?

1. self-supportive

2. filling of cusps allow contact with each other to prevent back flow of blood

cusp of bicuspid valve

• prevent backflow of blood between left atrium and left ventricle

• need chordae tendiane to support

how many cusps does the aortic valve possess?

three semilunar valves

what is the function of trabaculae carnae?

reduced velocity of blood through its rough surface

what is important about the arrangement of the cardiac muscles?

reduce size of heart during contraction due to spiral arrangement