Heart Flashcards
Pericardium layers
3 layers-
Outer fibrous pericardium
2 layers of serous pericardium (parietal and visceral)
Fibrous pericardium is made of … and attached to the posterior surface by…
Made of tough connective tissue.
Attached to posterior surface by sternopericardial ligaments- helps keep in position
The phrenic nerves pass through the fibrous pericardium on route to the diaphragm and innervate the sac.
Serous pericardium consists of…
Visceral and parietal pericardium with pericardial cavity
Pericardial cavity contains a small amount of fluid to prevent friction. The potential space allows for movement of the heart (beating).
Pericardial sinuses are…
Pericardial sinuses are small ‘pouches’. In two placesthe visceral and parietal pericardium fuse together and become continuous- the pericardial cavity is sealed:
- Superiorly, surrounding the arteries (aortaandpulmonary trunk)
- Posteriorly, surrounding the veins (superior vena cava,inferior vena cava,pulmonary veins) –>Oblique pericardial sinus.
- The transverse pericardial sinus is a passageway connecting the anterior and posterior reflections
Pericardium conditions
Pericarditis- Inflammation of the pericardium. Chest pain and high temperature but not usually serious. Usually caused by viral infection. Similar pain to a myocardial infarction but pain is often relieved by leaning forward. Confirmed by ECG.
Cardiac tamponade- Caused by pericardial effusion (excess fluid in pericardial cavity). Fibrous pericardium is ‘fixed’ in place so no room for structures to expand. Compresses the heart due to a build up of blood, fluid, pus or gas in the pericardial cavity, reducing cardiac output. The fibrous pericardium is fairly rigid so cannot expand easily. Medical emergency. Fluid can accumulate for several reasons- haemorrhage, infection, complication of pericarditis.
Great vessels
L& R brachiocephalic veins:formed by theunion of the subclavian and internal jugular veins.Unite to form the superior vena cava –> upper body
Inferior vena cava–> lower body
Pulmonary trunk divides into L&R pulmonary arteries
Pulmonary veins= 4- 2 left and 2 right
Aorta
A: Arch of Aorta
B: Brachiocephalic trunk
C: Common carotid (left)
S: Subclavian (left)
Anterior view of the heart
Anterior surface mainly consists of the right ventricle. Some R ventricle and some L ventricle.
Posterior view of the heart
base (posterior surface) and diaphragmatic (inferior) surface- coronary sinus separates these
Base is quadrilateral shaped and mainly formed from proximal ends of great veins + some of L and R atrium. Immediately anterior to oesophagus. Inferior is mainly left ventricle, some right ventricle.
Right atrium
Forms most of the right border and contributes to the anterior surface
Deoxygenated blood enters the right atrium via either the SVC, IVC, or coronary sinus.
Separated by the Crista terminalis (a thick muscular ridge).
Walls anterior to the crista terminalis are covered in muscular ridges called musculi pectinati(pectinate muscles). Walls posterior to the crista terminalis are smooth.
Interatrial septum separates R and L atria. Fossa ovalis marks location of foramen ovale- important part of foetal circulation-allowed oxygenated blood to pass from R atria to L, bypassing lungs.
Right ventricle
Forms most of the anterior surface and part of diaphragmatic surface
Trabeculae carneae= irregular muscular ridges
Tricuspid valve closes the atrioventricular orifice during ventricular contraction and has three cusps. Each cusp is attached to chordaetendineae. Chordae tendineae attach to two papillary muscles. Pulmonary semilunar valve consists of threesemilunar cusps.
Deoxygenated blood leaves the heart via the pulmonary trunk -> lungs.
Left atrium
Forms most of the base
Posterior ½ has smooth internal walls and receives the 4 pulmonary veins.Anterior ½ contains Musculi pectinati. Continuous with left auricle.
Valve of foramen ovale: important developmentally. Not always completely fused in adults
Left ventricle
Diaphragmatic surface and some anterior
Mitral (or bicuspid) valve has twocusps.Mitral cusps attach to papillary muscles via chordae tendineae.
Trabeculae carneae present
Longer and thicker walls (myocardium) than right ventricle.
Aortic semilunar valve consists of 3 semilunar cusps
Oxygenated blood leaves via the aorta
Heart orientation
Right border = R. atrium
Inferior border = mostly RV with small amount of LV (the apex)
Left border = mostly LV + small part of LA
Ant. (sternocostal) surface = RV (plus small amounts of the atria)
Inf (diaphragmatic) surface = 1/3 RV, 2/3 LV
Post. Surface (base) = LA
Surface markings of the heart
Aortic valve: Medial end of R 2nd intercostal space
Pulmonary valve: Medial end of L 2nd intercostal space
Tricuspid valve: Just left of lower part of sternum near the 5th intercostal space
Bicuspid valve: Left 5th intercostal space at the midclavicular line.
Electrical conduction
- Sino-atrial node (cardiac pacemaker) generates excitatory signals.
- Excitatory signals spread across the atria causing them to contract.
- The wave of excitation stimulates the atrioventricular node.
- Signal travels downthe atrioventricular bundle.The bundle is specialist tissue which conducts the excitatory impulse to all ventricle musculature.
- The atrioventricular bundle divides in to a left and right branch. The branches descend towards the apex. Further divide into terminal pukinje fibres.
- The wave of excitation causes the ventricles to contract from the apex upwards.
- The Autonomic division of the PNS is directly responsible for controlling heart rate and the force of contraction
Fibrous cardiac skeleton
Four interconnected rings of dense fibrous connective tissue surrounding the two atrioventricular orifices, the aortic valve, and the pulmonary valve.
Maintains the integrity of the openings it surrounds.Provides points of attachment for the cusps. Provides a solid structure for muscle tocontract against.
Electrically isolated- the fibrous skeleton separates the atrial half of the heart from the ventricle half of the heart. They are electrically isolated
The Atrioventricular bundle passes through the skeleton and is the only connection between the two groups of myocardium (cardiac tissue).
Coronary arteries
Right coronary artery- arises from right aortic sinus, descends in the coronary sulcus
Left coronary artery- arises from left aortic sinus, runs between the left auricle and the pulmonary trunk to enter the coronary sulcus. Divides into 2 branches.
Venous drainage of the heart
Anterior- great and small cardiac vein
Posterior- middle and posterior cardiac vein
Cardiac arrest
Malfunction in electrical conduction system- ventricular fibrillation
Heart stops pumping blood and brain starved of oxygen
Abrupt loss of breathing and consciousness
Coronary artery disease
Reduction of blood flow to myocardium due to build up of atherosclerotic plaque within coronary arteries eg.
Angina (chest pain due to reduced blood flow) and myocardial infarction (reduced blood flow to heart causing tissue death, can lead to cardiac arrest)
Cardiac referred pain
Referred pain is pain perceived at a location other than the site of the painful stimulus/ origin.
Cardiac ischemia: pain is felt in the jaw, neck, left shoulder and down the left arm.
Multiple primary sensory neurons converging on a single ascending tract in the spinal cord.
Pain perceived in visceral receptors is interpreted by the brain as more common signals that arise from somatic receptors (skin), rather than the viscera.
Dermatome = an area of skin innervated by a spinal nerve, but nerve distribution is variable, and territories can overlap.
