VET 205

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

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

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)

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

Tricuspid Valve◦ Low third or fourth intercostal

space

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 cavity-

lubrication

Epicardium=outside layer of the heart (visceral pericardium)

Myocardium= muscular layer of the heart◦ Cardiac muscle

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)

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)

Four Chambers◦ 2 Atria◦ 2 Ventricles

Heart is divided into right and left sides partitions◦ Interatrial septum-divides right and left atria◦ Interventricular septum-divides right and left

ventricle

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

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

Receives deoxygenated blood from Cranial and Caudal Vena Cava Atrium-Body and Auricle (blind-ended sac)

◦ Body-smooth◦ Auricle-rough, lined with pectinate muscles

Foramen Ovale -fetal structure to shunt blood from the right left atrium◦ Fossa ovale-remnant

**

Coronary Sinus-venous blood return from heart muscle ◦ Empties in at the base of

Caudal Vena Cava Interatrial Septum-

separates right and left Atria

Separates right atrium and rightVentricle One way valve-only allows blood

to leave right atrium and enter right ventricle

Three valve leaflets attached to a valve annulus

Annulus Leaflets Chordae Tendinae Papillary Muscle

Pumps deoxygenated blood to the low pressure pulmonary circulation Walls of right ventricle much thinner than

left ventricle◦ Left ventricle must pump to systemic circulation

Body and outflow portion Moderator Band (trabecula

septomarginalis)- from interventricular septum and right free wall of ventricle◦ Contains conductive (nerve) tissue-right bundle

branch

**

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

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

Most common congenital heart defect in dogs

Stenosis= narrowing of a passageway Third most common defect

Bring oxygenated blood from the lungs to the left atrium

4-6 veins enter into Left atrium via Ostia or orifices

Receives blood from pulmonary veins Divided into Body and Left Auricle

**

Lies between Left Atrium and Left Ventricle Bicuspid valve-2 leaflets Chordae tendinae attaches valve to

papillary muscle

Mitral Prolapse

Thick walled chamber Pumps oxygenated

blood into systemic circulation

Inflow-from Mitral valve Outflow-Aortic

valve>>Aorta

Division between Right and Left Ventricle

Membranous portion and Muscular portion◦ Membranous portion –

closes to valves◦ Muscular portion-closes to

apex

Ultrasound

Semilunar valve- three cusps Separates Left ventricle and Aorta

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)

Grooves for Coronary arteries and veins

Right Coronary Artery Left Coronary Artery

ParaconalInterventricularCoronary artery

CircumflexCoronary Artery

Subsinosal interventricular branch

Return blood from heart tissue Enter into Right Atrium via the Coronary

Sinus

Artery>> Arterioles>> Capillaries>> Venules>> Veins

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)

Small vessels-single layer of endothelium with thin connective tissue supporting

Exchange vessels No smooth muscles

Thin walled structure Large veins-some smooth muscle

◦ Venoconstriction and venodilation possible to control return of blood to heart

Low pressure vessels◦ Valves present to keep blood flow in one direction

Small veins = venules◦ No smooth muscle

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).

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.

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)

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)

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

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).

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.

This workforce solution was funded by a grant awarded under the Workforce Innovation in Regional Development (WIRED) as implemented by the U.S. Department of Labor’s Employment and Training Administration working in partnership with the Colorado Department of Labor and Employment, the Metro Denver Economic Development Corporation, and the City and County of Denver's Office of Economic Development.  The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor.  The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership.  This solution is copyrighted by the institution that created it. Internal use by an organization and/or personal use by an individual for non-commercial purposes is permissible.  All other uses require the prior authorization of the copyright owner.