The Heart Flashcards
Arteries
Carry blood away from the heart (usually oxygenated)
Veins
Carry blood towards the heart (usually deoxygenated)
Describe the position of the heart
Posterior to the sternum, superior to the diaphragm.
Within the mediastinum of the thorax between the lungs.
Orientated with the apex pointing to the left.
Roles of the pericardium
- Anchors the heart in place
- Prevent overexpansion
- Provide lubrication to permit free movement
- Limit potential spread of infection
What is the main cause of myocardial infarction?
Thrombi (clots) in the coronary arteries which provide oxygen-rich blood to the myocardium
What is a common site for a blockage in blood vessels ?
The left anterior descending coronary artery
Which side of the heart has thin walls ?
The right side
How does the right atrium receive blood ?
- Via the superior Vena Cava from the head, neck, thorax and upper limbs.
Blood from the coronary circulation also enters here via the coronary sinus. - Via the inferior Vena Cava from the trunk, pelvis and lower limbs.
Nutrient-rich blood from the gastrointestinal system is also brought by the portal circulation.
What are two important features of the right atrium?
- Sino-atrial node
- Fossa ovalis
What is the SA node ?
It is the pacemaker of the heart which is responsible for generating electrical activity to stimulate contraction
What is the fossa ovalis ?
The remnant of a hole in the inter-atrial septum during foetal development.
What is the role of the right ventricle?
It pumps blood into the pulmonary trunk, which pumps blood towards the lungs for reoxygenation
Where is the tricuspid valve located ? What is another name for it ?
It is an atrioventricular value located between the right atrium and ventricle
Where is the semilunar valve located? What is another name for it ?
The pulmonary valve is found between the right ventricle and the pulmonary trunk
What does the left ventricle do ?
Pumps blood into the thoracic aorta which pumps blood across the systemic circulation
Where is the mitral valve found? What is another name for it ?
The bicuspid valve is an AV valve found between the left atrium and ventricle
What are chordae tendinae ?
Heart strings
What do chordae tendinae do ?
They extend from papillary muscles to the leaflets of the two AV valves and prevent the back flow of blood during systole
What are the 3 layers of the heart ?
- Endocardium- lining
- Myocardium- muscle layer
- Epicardium- visceral pericardium
Histology of the endocardium
Comprises of:
1. Thin layer of endothelium
2. Middle layer of dense connective tissue and smooth muscle
3. Deeper subendocardial layer which has Purkinje fibres
What cell-cell junctions link the heart muscle cells at intercalated discs ?
- Adherens junctions
- Desmosomes
- Gap junctions
What do adherens junctions do ?
Link the actin cytoskeleton to allow sarcomere contraction
What do desmosomes do ?
Link intermediate filaments to provide stength
What do gap junctions do ?
Link cytosol to allow cell-cell communication, coordination of contraction from cell to cell along heart muscle fibres
