Heart Physiology: Location and Pericardium

Heart Physiology: Location and Size

• The heart is about the size of a closed fist and located near the midline of the thoracic cavity.
• The heart rests on the diaphragm within the mediastinum, between the sternum and vertebrae, from the first rib to the diaphragm, and between the lungs.

Location Terms and Surfaces

• The apex, formed by the left ventricle, forms the inferior point of the heart.
• The base is opposite of the apex and the superior aspect of the heart.
• The anterior surface is the front-facing surface, posterior to the sternum and ribs.
• The inferior surface rests on the diaphragm
• The right surface faces the right lung and the left surface faces the left lung.

Pericardium Structure and Function

• The pericardium is a triple-layered membrane that surrounds and protects the heart.
• Fibrous pericardium anchors the heart in the mediastinum with thick tough connective tissue.
• Serous pericardium is a double layer around the heart.
  • The Parietal layer is the outer layer fused to the fibrous pericardium.
  • The Visceral layer, or epicardium, is the inner layer adhering tightly to the heart surface.
• The pericardial cavity, lies between the serous layers and is filled with pericardial fluid.

Heart Wall Layers

• Epicardium is the external layer that covers the heart
  • It comprises the visceral pericardium and provides a slipper surface to the outermost surface of the heart. Also features fibroelastic tissue and adipose tissue.
• Myocardium is the middle layer and the cardiac muscle layer responsible for the heart's pumping action.
• Endocardium is the innermost layer, providing a smooth lining for the heart chambers.

Chambers of the Heart

• The heart has two atria (right and left) that act as entry halls to receive blood returning to the heart from veins.
• Two Ventricles (right and left)
  • Eject blood from the heart into arteies
• Atrial Auricle located on the anterior surace of rach atria
  • Slightly increased capacity of the atria
• The coronary sulcus marks the boundary between atria and ventricles and contain the coronary sinus.

Right Side of the Heart

• The right atrium receives blood from the superior vena cava, inferior vena cava, and coronary sinus.
• The posterior wall is smooth, while the anterior wall is rough due to pectinate muscles.
• The interatrial septum is the thin wall between the left and right atria.
• Fossa ovalis is a depression in the interatrial septum; a remnant of an opening in the fetal heart that closes after birth.
• The tricuspid valve, also known as the right atrioventricular valve, consists of three cusps and separates the right atrium from the right ventricle.
• The right ventricle receives blood from the right atria.
• Has Papillary muscles
• Nipple shaped
• Prevents inversion of the atrioventricular valves during ventricular contraction.
• Trabeculae carneae are ridges of muscular columns that assist the papillary muscles to resist the inversion.

Left Side of the Heart

• The left atrium receives blood through four pulmonary veins (two from the left lung and two from the right lung).
• The bicuspid valve, also is known as the mitral valve or left atrioventricular valve, allows blood pass to the left ventricle through the bicuspid valve with two cusps
• The left ventricle has the Thickest chamber in the heart
• Blood leaves it to the Aortic Valve
• which passes from left ventricle through aortic valve into ascension aorta
• Ligamentum arteriosum
  • Ligament that connects aoritc arch to pulmonary trunk

Myocardial Thickness

• The thickness of muscle in the heart varies depending on the pressure each chamber needs to produce.
  • Atria, have thin walls because they do not need to create much pressure
  • Whereas the Ventricies and Left Ventricle needs to push aganst the pressure to the lungs and for the rest of the body
  • Fibroid skeleton provide structure to do this, with dense connective tissue to prevent over strectching

Heart Valves

• The heart has pulmonary and aortic (semilunar) valves that allow blood flow out the ventricles and prevent backflow into ventricles. - Semilunar AKA half-moon shaped
• It also has tricuspid and bicuspid (atrioventricular) valves that closes with ventricles contract - Push av valves and closes them
• Atrial constraction, is where blood then flows inti relaxed ventricles via the AV Valves

Blood Circuits

• The heart consists of two circuits, arranged in series and is connected to the blood supply to provide oxygen, nutrients, and removal as need - Two cirulations means that what comes out as output for the blood from the heart (output of one) feeds into the other - Heart can be really considerred as 2 pumps, pump 1: right, Pump 2: left
• Right pump: Collects deoxygenated blood from systemic circulation
• Left pump: Collects oxygenated blood from lungs and pumps it to systemic circulation
• Coronary: Provide blood to heart, with circuling and the crown shape, and carry out deoxygenated blood

Veins and Coronary

• Coronary veins
  • Are what bring back deoxygenated blood to the heart
  • Drain through the coronary circus into the right atria
  • These can include multiple where 2 supply arteries connect

Conduction System

• Rhythmic Electral cavity controls for Autorythmic fibers and peacemaker
  • hearts life long and contous beating
  • Continuous beats is due to specialist fibres
  • Hearat contines to beat even if remove, the specialized fibres act as a pacemaker

Cardiac Action Potential (CAP)

• Flow through induction, 5 steps
  1. Sinoatrial node (SA): Locted in the rigth antia
  • Is unstable and repeatedly depolarize initiaring action potentials, and are carried out to both left and right atria so the contract together
  2. Atrioventricular Valve
  • Ation potential reches AV node At this stage blood empities in the ventricles
  3. AV bundle
  • Action potential
  • Enters Av bundle
  4. Right and Left
  5. Purkinje fibers
  • Contratino starts at apex