Heart and Pericardium Flashcards
What are the borders of the heart + how is the how situated?
• The shape of the heart was formed by twisting and turns during foetal development.
• The apex of the heart will be towards the left, and it will have a base which is where it sits on posteriorly.
• When you first look at a heart, the first thing you will notice is the right side of the heart, mainly the right ventricle.
• Inferior border of the heart: RIGHT VENTRICLE
• Right border: RIGHT ATRIUM
• Base(posteriorly): LEFT ATRIUM
Left border: LEFT VENTRICLE
What are the two grooves within the heart, and what are they markers for?
- Interventricular groove: Between the ventricles
- Atrioventricular groove: Between the atrium and ventricles
What are two types of wall of the atrium?
(1) Musculi Pectinati, (made up of muscular ridges), (2) Smooth wall; including the inter-atrial septum(the marker that separates the right and left atrium.)
What is the Crista Terminalis, and what is the alternative name?
• There is a little ridge that runs between the two types of wall, separating them called the ‘Crista Terminalis’.
• There is a ‘Sulcus Terminalis’ on the outside atrial wall, which is formed by a little bit of dimpling on the external surface of this ‘Crista Terminalis’.
—-> This is a really good marker to find the SA node.
What is the fossa ovalis and function?
Remnant of the Foramen Ovale from foetal circulation, which was an opening between the right and left atrium early in development. Its importance lies in that, during foetal life, no oxygen is present, so its unnecessary to shunt blood from RA to RV through the Pulmonary trunk to lungs etc, instead this hole allows the blood to by pass the Right Ventricle and pulmonary circulation and just go straight into the Left Atrium and Left Ventricle, out to the systemic circulation. After birth, this hole is closed.
What is the coronary sinus?
It is a venous structure on the posterior surface of the heart, but it receives all the veins that drain the heart itself. It is pointless for all those veins to otherwise go into the SVC and then drain into the Right Atrium. Instead, they collect into the coronary sinus which opens directly into the Right Atrium. This opening can be appreciated between the IVC and Right atrioventricular orifice.
What is atrioventricular orifice of the right atrium protected by and why?
‘Tricuspid Valve’.
What is the auricle?
Little ear shaped projection of the RA, in front of the great vessels, the aorta and pulmonary trunk. Remnant of the way the heart developed so it has a rough wall part.
What is the Septomarginal band?
Also referred to as the ‘Moderator band’. Essentially connects the anterior papillary muscle with the medial or the interventricular wall. Some of the conduction system of the heart travels through this band and gets direct access to the papillary muscle. Providing it with the ability to contract at the same time as all of the other papillary muscles which have a shorter conduction distance, and makes sure all the cusps get anchored all at the same time, and at the same level.
Explain the metal heart and circulation?
• Blood bypasses the pulmonary circulation during foetal life, because we don’t have any oxygen.
• All the oxygen is obtained from maternal circulation via the placenta.
• Parts of the foetal circulation will pass through the liver, which is very different to post-birth.
• There are a few systems that allow the blood to bypass the pulmonary circulation:
(1) Foramen Ovale: Blood comes in from IVC, and passes through a deficiency in the inter-atrial septum called the ‘Foramen Ovale’ and directly into the Left Atrium.
(2) Ductus Arteriosis: A lot of blood comes in through the SVC into the foetal Right atrium, and tends to fall directly down into the Right Ventricle and wants to go directly into the Pulmonary trunk to go to the lungs, so to stop that, there is another opening, between the P-trunk and Aorta, called the ‘Ductus Arteriosis’.
What happens at birth to the circulation?
• At birth there is a different in pressure between the atmosphere and the lungs, air is going to want to move into the lungs, so the lungs expand, and as they do so, blood moves into the lungs, changing the pressure, hormones begin to act, that act on the smooth muscle around the Ductus Arteriosus and closes it.
What its the fibrous skeleton?
- Fibrous skeleton of the heart is connective tissue which bridges or separates the Atria from the Ventricles.
- This is essential so that the contractions can be out of sync.
- Forms figure 8’s around all the valves, and they can be found in this atrioventricular plane, surrounded by this connective tissue.
- Important electric insulator. Also for making sure the atria and ventricles were not all electrically connected.
Discuss the nerve supply to heart?
Vagus nerve supplies most of the viscera, and it decreases heart rate and force of contraction.
- It runs down past the heart, posterior to the root of the lungs, runs down the arch of the aorta, and behind the pulmonary artery
As the Vagus nerve comes down, it gives off fibers that contribute to the parasympathetic innervation of the heart.
Sympathetic nerve increases heart rate and force of contraction.
- Preganglionic neurons originate of the lateral horn of spinal segments T1-T4. They synapse in the sympathetic chain, and run down through these branches into the substance of the heart.
- Cardiac plexus reaches into the heart, just before the bifurcation of the pulmonary trunk into the pulmonary arteries.
These branches that contribute to the plexuses are really had to differentiate.
Where is pain referred from heart?
Pain referred from the heart is projected to T1 - T4 dermatomes.
- We know that the sympathetic nerves derive from spinal segments T1-T4, and the somatic afferents follow the sympathetics, we are going to predict that the visceral sensory neurons end up in back in T1- T4 spinal cord segments.
- Heart attack pain, is therefore referred to across the chest and down the arm.
- The left limb specifically because the orientation of some of the plexus leading into the heart are found there.
Discuss the pericardium?
3 coverings of the heart:
(1) Serous, double layered pericardium: with 2 components, Visceral layer - directly lines the heart , Parietal layer - lines some of the structures outside of heart.
(2) Pericardial space, which has abit of fluid in it, which allows for movements, and frictionless beating of the heart
(3) Fibrous pericardium: Thick, dense, connective tissue sheet around the serous pericardium and it is anchored to the central tendon of the diaphragm. Parietal layer is stuck underneath the fibrous pericardium
Some textbooks will name the visceral layer “epicardium”
