Transcript The Cardiovascular System

VET 205
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Heart lies within Mediastinum
◦ Mediastinum separates R. and L. Pleural Cavities
◦ Other structures?
 Dorsal to the Heart-Trachea, mainstem bronchi,
espophagus, lymph nodes, vessels
 Ventral to the Heart-Sternum
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Dog
◦ Third to Sixth intercostal space
◦ Base of the heart-Surface of the heart that all the
vessels enter and exit
 lies craniodorsal
◦ Apex-located at diaphragm/sternum junction
 Lies slightly more on the left side of midline
◦ Conformation of animal can alter angle heart sits in
the thorax
Slightly louder on L. side
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Heart is almost completely surrounded by
lungs
Cardiac Notch- small window where heart
makes contact with thoracic wall
◦ Right ventrolateral thoracic wall
◦ At 4th to 5th intercostal space, costochondral
junction (junction between bony and cartilage
portion of the rib)
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Optimum sites of listening to heart valves
Left thorax
◦ Pulmonic valve
 Low third intercostal space
◦ Aortic valve
 High fourth intercostal space
◦ Mitral valve
 Low fifth intercostal space
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Tricuspid Valve
◦ Low third or fourth intercostal
space
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Fibroserous covering
surrounding the heart
◦ Fibrous pericardium-outer surface
◦ Attaches to great vessels as they
leave and enter heart
◦ Serous pericardium-lines the
fibrous pericardium (parietal
pericardium) and covers the heart
(epicardium or visceral
pericardium)
 Space between two layers of serous
pericardium= pericardial cavity
◦ Fluid in Pericardial cavitylubrication
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Epicardium=outside layer of the heart
(visceral pericardium)
Myocardium= muscular layer of the heart
◦ Cardiac muscle
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Endocardium= thin membrane that covers
the inside chambers of the heart
◦ Remember the characteristics of cardiac cells
 Intercalated disks Desmosomes and Gap junctions-allow ion transfer from
cell to cell
 Transmits the current (depolorization)
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Fibrous tissue that
separates the atria from the
ventricles
Does not transmit electrical
impulses as well-no
myocytes.
Allows delay from top of
the heart (atria) to the
lower portion of the heart
(ventricles)
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Four Chambers
◦ 2 Atria
◦ 2 Ventricles
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Heart is divided into right and left sides
partitions
◦ Interatrial septum-divides right and left atria
◦ Interventricular septum-divides right and left
ventricle
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Atria-receive venous blood (blood coming to
the heart)
◦ Cranial vena cava-receives blood from head, neck,
chest wall and the thoracic limb
 Brachiocephalic veins Azygos vein-drains the spine, intercostal, esophagus
 Thoracic duct-drains most of the lymph from the body
◦ Caudal vena cava
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Ventricles- pump the arterial blood away
from the heart
◦ Right Ventricle>>Pulmonary Artery
◦ Left Ventricle>>Aorta
11. Brachiocephalic vein 12. Cranial vena cava 13. Azygous vein
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Receives deoxygenated blood
from Cranial and Caudal Vena Cava
 Atrium-Body and Auricle (blind-ended sac)
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◦ Body-smooth
◦ Auricle-rough, lined with pectinate muscles
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Foramen Ovale -fetal structure to shunt blood
from the right left atrium
◦ Fossa ovale-remnant
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Coronary Sinus-venous
blood return from heart
muscle
◦ Empties in at the base of
Caudal Vena Cava
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Interatrial Septumseparates right and left
Atria
Separates right atrium and right
Ventricle
 One way valve-only allows blood to
leave right atrium and enter right
ventricle
 Three valve leaflets attached to a
valve annulus
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Annulus
Leaflets
Chordae Tendinae
Papillary Muscle
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Pumps deoxygenated blood to
the low pressure pulmonary circulation
 Walls of right ventricle much thinner than
left ventricle
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◦ Left ventricle must pump to systemic circulation
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Body and outflow portion
Moderator Band (trabecula
septomarginalis)- from interventricular
septum and right free wall of ventricle
◦ Contains conductive (nerve) tissue-right bundle
branch
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Semilunar valve
Prevents blood from flowing from the
pulmonary artery back into the right ventricle
when the ventricle is filling.
Between Right ventricle and Pulmonary Artery
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Deliver deoxygenated blood from the right
ventricle to the lungs
Branches to Right and Left Pulmonary Arteries
and travels with Right and Left Bronchi
Ductus Arteriosum -connection between
pulmonary artery and aorta-fetal shunt
◦ Closes at birth and fibroses= Ligamentum
Arteriosum
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Most common
congenital heart
defect in dogs
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Stenosis= narrowing of a passageway
Third most common defect
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Bring oxygenated blood from the lungs to the
left atrium
4-6 veins enter into Left atrium via Ostia or
orifices
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Receives blood from pulmonary veins
Divided into Body and Left Auricle
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Lies between Left Atrium and Left Ventricle
Bicuspid valve-2 leaflets
Chordae tendinae attaches valve to papillary
muscle
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Mitral Prolapse
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Thick walled chamber
Pumps oxygenated blood
into systemic circulation
Inflow-from Mitral valve
Outflow-Aortic
valve>>Aorta
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Division between Right
and Left Ventricle
Membranous portion and
Muscular portion
◦ Membranous portion –
closes to valves
◦ Muscular portion-closes to
apex
Ultrasound
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Semilunar valve- three cusps
Separates Left ventricle and Aorta
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Three Main Divisions
◦ Ascending Aorta
 Contains opening for Right and Left Coronary Arteries
◦ Aortic Arch
 Brachiocephalic Trunk
 Left subclavian artery
◦ Descending Aorta
 Contains ligamentum arteriosum
 Continuous with Abdominal Aorta (retroperitoneal)
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Grooves for Coronary arteries and veins
Circumflex
Coronary
Artery
Paraconal
Interventricular
Coronary artery
Right Coronary Artery
Subsinosal interventricular branch
Left Coronary Artery
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Return blood from heart tissue
Enter into Right Atrium via the Coronary Sinus
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Artery>> Arterioles>> Capillaries>>
Venules>> Veins
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Three layers or tunics:
◦ Endothelium (Tunica interna)
◦ Middle tunic (Tunica media)
 Largest vessels-elastic fibers and smooth muscle
 Smaller arteries-smooth muscle
 Controlled by autonomic nervous system
 Smallest arteries (resistance arterioles)
 Regulate resistance to blood flow and blood pressure
 Vasoconstriction vs. vasodilation
◦ Outer fibrous layer (Tunica adventitia)
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Small vessels-single layer of endothelium
with thin connective tissue supporting
Exchange vessels
No smooth muscles
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Thin walled structure
Large veins-some smooth muscle
◦ Venoconstriction and venodilation possible to
control return of blood to heart
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Low pressure vessels
◦ Valves present to keep blood flow in one direction
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Small veins = venules
◦ No smooth muscle
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Blood is a connective tissue composed of
formed elements in a fluid matrix.
Plasma is the fluid portion, called serum
when the clotting protein fibrinogen is lost.
The formed elements include:
◦ Erythrocytes (RBC), leukocytes(WBC), and platelets
(thrombocytes in avian species).
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In general plasma makes up about 50 %
of the total volume, RBC’s ~ 35 -45 and
WBC’s about 1%. We will look at species
differences later.
Blood pH is slightly alkaline (~7.4)
Functions - deliver nutrients, Oxygen
transport, waste transport, delivery of
hormones, heat regulation, pH,
protection.
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After losing ~25% of the total blood
volume an animal has a 50% chance of
survival.
To calculate the blood volume you
should use LEAN body mass.
We use ~ 8% of an animals body weight
(Kg) for all species.
The average for small animals would be
◦ 88ml/ kg – dogs (9% X kg=L of blood)
◦ 56ml/kg – cats (6% X kg = L of blood)
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Heart-similar to mammalian
Vessel differences:
◦ Pectoral and brachial arteries-larger
◦ Renal Portal System-veins from extremities travel
through kidneys to remove metabolic waste
◦ Countercurrent system of heat exchange
◦ Resting HR estimate (beats/sec)
=12 X (4X weight in gm)
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Blood
◦ RBC-oval, nucleated and larger than mammals
◦ WBC
 Young-produced by spleen, liver, kidneys, pancreas
and bursa of Fabricius (dorsal wall of proctodeum)
 Adult-produced by spleen
 Heterophils=mammalian neutrophils
◦ Thrombocytes=platelets
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Heart rates vary with the size of the bird.
◦ 25 grams 275 BPM (resting) – 400-600 BPM
(restrained)
◦ 1000 grams 130 BPM (resting) – 150-350 BPM
(restrained)
When working with eagles and waterfowl,
always test blood lead levels!
Jugular - The right jugular vein is used
because it is fairly prominent (many bird
species lack a left jugular vein).
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Alar vein - located running across the ventral
surface of the humeral-radial-ulnar joint
(elbow) directly beneath the skin.
Medial Metatarsal Vein – located on the
medial side of the lower leg. When available,
this vein is typically the site of choice for
blood sampling in birds.
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