Lesson 86: The topography and structure of the heart

Where is the heart located?

Thoracic cavity, between the 3rd and 6th rib

In dogs and cats, the heart is situated….

obliquely oriented, apex is slightly to the left side

Where are the great vessels of the heart located?

At the base

Where is the phrenicopericardiac ligament located and what species is it found in?

Located between the apex of the heart and the diaphragm, small animals

Where is the sternopericardiac ligament located and what species is it found in?

Located between the apex of the heart and the sternum, large animals

Lungs are located on ______ of the heart

either side

Which side of the heart is there thinner pulmonary tissue layer?

Left

What are cardiac notches and where are they located in the dog?

Where the heart makes contact with the cardiac wall, only on the right in dogs

Are there cardiac notches in cats?

Yes, a little imprint on the L side but mainly on the R side

Are there cardiac notches in horses and cows?

Yes, on the L and R side

What part of the heart does the trachea make contact with?

The base

What part of the heart does the esophagus make contact with?

The base

What part of the heart do the phrenic and vagus nerves make contact with?

Both lateral sides of the heart

The heart is completely invested by the ___

pericardium

What is the pericardium

Outer covering of the heart which is composed of 3 layers

What is the visceral pericardium (epicardium)?

The layer which covers the heart wall, practically inseparable from the heart

What is the parietal pericardium?

The outer layer which is attached to the mediastinum. associated with the body wall

What is the pericardial cavity?

The space between visceral and parietal pericardium, which is essentially a potential space containing small amounts of serous fluid.

What is the fibrous pericardium?

fibrous connective tissue that glues the parietal pericardium to the mediastinal pleura

What is the mediastinal pleura?

The outermost layer in this region, the fibrous pericardium connects the parietal pericardium and the mediastinal pleura.

*technically not part of the pericardium

*splits the heart into R and L side

What 3 layers of the pericardium are so tightly attached they essentially form one membrane?

1. parietal pericardium

2. fibrous pericardium

3. Mediastinal pleura

What are the functions of the pericardium?

1. Provides isolated environment to the heart

2. Pericardial fluid functions as a lubricant

3. Prevents overstretching/over dilation of the heart (fibrous CT)

Which layers of the heart are cut to expose the heart wall?

1. parietal

2. fibrous

3. mediastinal

The heart has how many chambers and what are they?

4 chambers

2 ventricles

2 atria (atriums)

What is the ventricle?

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

What is the atrium?

A thin-walled chamber that receives blood

What is an auricle?

A blind sac extended from each atrium

What is the base of the heart?

Thin walled atria

What is the apex of the heart?

Ventral end of the L ventricle W

What is the coronary groove?

The groove that separates atria and ventricles

What are intraventricular grooves?

The grooves that demarcate ventricles from each other

The L interventricular groove is called….

Paraconal interventricular groove T

The R interventricular groove is called….

Subsinuosal interventricular groove

What is the conus arteriosus?

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

What does the pulmonary trunk do?

Carries deoxygenated blood to the lungs

What does the aorta do?

Oxygenated blood supply to the body

What is the ligamentum arteriosum? (ductus arteriosum in embryos)

Connection between the aorta and pulmonary trunk

Used in embryos because they do not have functional lungs at this point, so need a way to bypass the lungs and deliver oxygenated blood to the rest of the body

What do the cranial and caudal vena cavas do?

Collect deoxygenated blood from the body and bring to the right atrium

What does the azygous vein do?

Collects deoxygenated blood from most of the thoracic wall and brings it to the right atrium

(rib 3-4 and backwards)

What is the interventricular septum?

Seperates the ventricles

What is the interatrial septum?

Separates the atriums from each other

What do the atrio-ventricular openings do? (AV Valves)

Connect the atriums to the ventricles on each side

What type of blood flow is present in the atrio-ventricular valves?

Unidirectional flow

The heart wall is made up of….

Endocardium

Myocardium

Epicardium (visceral pericardium)

Endocardium

Most inner layer of the heart wall

Made up of simple squamous epithelium

Myocardium

Middle layer of the heart wall

Where the cardiac muscles are present

Epicardium (Visceral pericardium)

Outermost layer of the heart wall, connecting with visceral pericardium

What happens during systole?

Contractions of the atriums/ventricles

What happens during diastole?

Dilation/Relaxation of the atriums/ventricles

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

Right atrium

Where is the intervenous tubercle found and what does it do?

Found in the right atrium, prevents turbulence from the cranial, caudal, and azygous veins when bringing blood to the R atrium

The right auricle contains pectinate muscles because….

The R auricle expands more than the R atrium so needs the muscle for the expansion

Where are chordae tendineae found?

L and R atrio-ventricular valves

The right AV opening is guarded by?

The tricuspid valve

The left AV opening is guarded by?

The bicuspid valve

What are the cusps in the right AV opening?

Roughly triangular leaf or flap of a heart valve

Parietal, septal, and angular cusps

The pulmonary valve has how many semilunar cusps?

3, self supported, do not need chordae tendineae

The pulmonary and aortic valves are also called…… and why?

Semilunar valves because of the shape of the cusps

Where is the trabacula septomarginalis found and what does it do?

Left ventricle

Aids in contraction and workings of perkinje fibers

The L AV valve is also called the…

Mitral valve

The physiology of the ventricular muscles does what?

Contraction reduces size of the heart

Which valves of the heart need chordae tendineae for support?

The atrio-ventricular valves