Gross Anatomy of the Heart Flashcards
Location of the heart
- Located in the middle mediastinum between the lungs within the thoracic cavity.
- Located anterior; deep to the sternum and costal cartilages 3-5.
- The apex is near the midclavicular line (MCL) at teh level of the 5th intercostal space.
Mediastinum
A space located between the two pleural cavities and contains all the thoracic viscera except the lungs. It runs from the superior thoracic aperture to the diaphragm and from the sternum to the thoracic vertebral bodies.
Layers of the pericardium
- Fibrous pericardium
- Parietal layer of serous pericardium
- Visceral layer of serous pericardium
Fibrous pericardium
Dense CT, fused to the diaphragm and tunica adventitia of the great vessels (aorta, SVC). The fibrous pericardium and heart move with the diaphragm during respiration.
Parietal layer of serous pericardium
Simple squamous epithelium and thin layer of LCT lines the inner surface of fibrous pericardium. It is reflected back onto the heart where the great vessels enter and leave the heart to become the visceral layer of serous pericardium (=epicardium).
Visceral layer of serous pericardium
Epicardium.
This is the outermost layer of the three layers of the heart, with the two other layers being the myocardium and endocardium.
Adipose tissue frequently deposits between the epicardium and mycoardium, making identification and dissection of the coronary vessels difficult.
Pericardial cavity
Is located between the parietal and visceral layers, it is a potential space with thin film of serous fluid = reduces friction as the heart pumps.
Transverse pericardial sinus
Lies anterior to the SVC and posterior to the ascending aorta and pulmonary trunk.
Oblique sinus
Lies posterior to the heart in the pericardial sac.
What vessels open into the right atrium?
SVC, IVC and coronary sinus.
Fossa ovalis
A remnant of the foramen ovale in the interartrial septum.
Describe the anatomy of the walls of the right atrium.
The internal atrial wall is smooth posteriorly and rough (pectinate muscles) anteriorly.
What is the junction between the smooth wall and pectinate muscles called in the right atrium?
Sulcus terminal exteriorly and crista terminalis internally.
What is the term for the muscle ridges in the right ventricle?
Trabeculae carnae
What separates the inflow tract from the outflow tract in the right ventricle?
The supraventricular crest which is an elevated smooth musclar ridge.
Conus arteriosus
The superior narrowing of the outflow track. Also termed infudibulum.
Septomarginal trabecula
Also called the ‘moderator band’.
Curved muscle bundle travelling from the inferior interventricular septum to the base of the anterior papillary muscle in the right ventricle.
It carries part of the conducting system.
Describe the structure of the walls of the left atrium.
Mostly smooth walled except the small left auricle which has pectinate muscles.
Difference between right and left ventricle.
The left ventricle has a thicken wall, and the trabeculae carnae are finer and more numerous than RV. Has large papillary muscles.
Aortic vestibule
Outflow area of LV.
Custs of pulmonary valve
Anterior, right and left.
Cusps of aortic valves
Posterior, right and left.
Tricuspid valve cusps
septal, anterior and posterior.
Mitral valve cusps
Anterior, posterior.
Stenocostal surface of the heart
‘Anterior’ surface.
Mainly right ventricle, also right atrium (incuding auricle) and left ventricle.
Base of the heart
‘posterior’ surface.
Left and right atria
Diaphragmatic border
Inferior border.
Mainly left ventricle, partly right ventricle.
Left surface of the heart
‘Pulmonary’
Left ventricle and left atrium.
Right surface of the heart
‘Pulmonary’ surface
Right atrium.
Apex of the heart.
Left ventricle.
Right mediastinal border
Right arium, SVC, ICV
Left mediastinal border
Left ventricle, auricle, pulmonary trunk, aortic arch.
Inferior mediastinal border
Right ventricle, left ventricle at apex.
Posterior border on lateral CXR
Left atrium
Anterior border on lateral CXR
Right ventricle
Inferior border on lateral CXR
Right and left ventricle.
Surface anatomy upper border of the heart
2nd left costal cartilage to 3rd right costal cartilage.
Surface anatomy of right border of heart
A curved line convex to the right from the 3rd right costal carlage to the 6th right costal caritlage 1-2cm lateral to the sternal edge.
Inferior border surface anatomy
Form the 6th right costal cartilage to the apex of the heart located at the 5th left intercostal space in the mid clavicular line.
Left border surface anatomy
A line convex laterally from the apex to the 2nd left costal caritlage 1cm from the left sternal edge.
Left coronary artery
Also called the left anterior descending (LAD).
Gives rise to:
- Anterior interventricular a
- Circumflex a
A common variation is the lateral branch (diagonal branch) arising from the LAD__.
Left marginal branch
Arises from the circumflex artery.
SA nodal branch
Arises from the circumflex artery in 40% of people.
In 60% of people the right coronary artery gives off the SA nodal branch.
LCA dominant
In 10% of people, the circumflex artery continues around to the posterior surface of the heart and becomes the posterior interventricular a.
What does the LCA supply?
Typically the LA, most of the LV, part of the RV, most of the IVS (interventricular septum), the AV bundle (of His), right and left bundle branches and the SA snode in 40% of the population.
The right coronary artery
The right coronary artery gives off
- Right (acute) marginal a
- Posterior interventricular a
- AV nodal branch.
RCA dominant
Posterior interventricular a given off by teh right coronary artery (80% of people).
What does the RCA supply?
Supplies the RA, most of the RV, the diaphragmatic surface of the LV, the SA node in 60% of people and the AV node in 80% of people.
It may supply the apex of the heart if the LAD is short.
Veins of the heart
Great cardiac vein: travels with the anterior interventricular artery and circumflex artery.
Middle cardiac vein: travels with the posterior interventricular artery
Small cardiac vein: tarvels with the right marginal branch.
All terminate at the coronary sinus which drains into the right atrium.
The anterior cardiac veins and other small cardiac veins drain directly into the heart chambers.
Lymphatic drainage of the heart
Generally follows blood vessels of heart, then to lymph node groups around trachea to the right lymphatic duct or thoracic duct.
Fibrous skeleton of the heart
Composed of DCT - forms a fibrous ring around each valve, connects the valves and forms part of the interatrial and interventricular walls. Functions to support the valves and as an attachment point for the valve cusps or leaflets. Prevents electical conduction between atria and ventricles. The myocardium also attaches to the fibrous skeleton.
Conduction system of the heart
- SA node
- AV node myogenically (by muscle)
- AV bundle (of His)
- Right and left bundle branches
- Purkinje fibres (subendocardial)
SA node location
Right atrium near SVC origice and crista terminalis.
AV node location
Interatrial septum near coronary sinus opening.
Autonomic innervation of the heart
Autonomic system supplies the heart via the cardiac plexus, primarily acts on SA node (some effect on the AV node and myocardium).
Sympathetic activity on heart
- Increase HR
- Increase force of contraction
- Increase coronary artery flow
Sympathetic preganglionic innvervation of heart
The preganglionic cell bodies are located in the lateral horn of T1-5 spinal cord.
Preganglionic axons travel through the ventral root, spinal nerve, white ramus communicans to the sympathetic chain ganglion where they synapse in the cervical and upper thoracic ganglia.
Postganglionic sympathetic innervation heart
Postganglionic axons travel via cardiac nerves to cardiac plexus to heart primarily to the SA node but also to other parts of teh conduction system.
Parasympathetic innervation of the heart
The parasympathetics travel in the vagus nerve (CNX) and act to slow the heart rate.
Preganglionics of parasympathetics
Preganglionic cell bodies are located in the medulla of brainstem. Preganglionic axons travel in the vagus nerve and it’s cardiac branches. They synapse in ganglia in cardiac plexus of near SA and AV nodes. They innervate the conduction system, particularly the nodes.
Afferent innervation of the heart
Afferents carry pain, stretch etc. and travel with the vagus and sympathetic branches. Pain fibres travel with sympathetic fibres to T1-T5 spinal cord levels mainly on the left.
Referred cardiac pain
Brain misinterprets pain from heart as arising from T1-T5 body segments (corresponding dermatomes) - chest pain, left upper limb, other areas. Neck and jaw pain may relate to vagus afferent, not fully understood.
