Heart Flashcards
Organization of the thorax
two compartments (or 3)
Respiratory Compartments
two laterally placed areas containing the lungs and pleura
Mediastinum
- partition separating the lungs
- contains the heart, trachea, 1o bronchi, esophagus, great vessels, and many other nerve trunks and lymphatic channels.
Pericardial Sac (3 details)
- 2 components comprising 3 layers
A. Fibrous Pericardium - tough heavy connective tissue component - inferiorly this is adherent to central tendon of diaphragm - merges and becomes continuous with connective tissue around the great vessels.
B. Serous Pericardium - forms a sac called the pericardial cavity - the heart does not lie within the cavity but rather is surrounded by it. Cavity is “potential space” and contains only a small amount of fluid (pericardial fluid). Serous pericardium can be considered to have 2 layers:
1. Parietal layer - lining inner aspect of fibrous pericardium
2. Visceral layer - applied to surface of the heart
note: pericarditis = inflammation of serous pericardium
External Morphology of Heart (4 details, with sub details)
A. lies slightly to the left of midline
B. roughly about the size of your clenched fist
C. position occupied by the heart can be roughly approximated on outside of chest by imagining 4 points.
1. just under the 2nd rib about an inch to the right of the sternum.
2. about level with the top of the xiphoid process of the sternum and about 2 inches right of body’s midline.
3. about 1/2 - 1” lower than this point on the left in a saggital plane that would include the middle of the left clavicle.
4. the second rib about an inch left of the sternum.
D. Described as having 4 surfaces (like upside down pyramid)
1. Sternocostal surface - right atrium, right ventricle, and small portion of left ventricle.
2. Diaphragmatic surface - mostly left ventricle with small part of right ventricle.
3. Pulmonary surface - left ventricle
4. Base - both atria and points of entrance and exit of the great vessels.
Structure of Heart Wall (4 details)
- made up of 3 layers
A. Epicardium - outermost layer - includes visceral pericardium and underlying connective tissue and fat - houses the coronary arteries.
B. Myocardium - composed of cardiac muscle - constitutes bulk of the heart - responsible for contraction.
C. Endocardium - simple squamous epithelium similar to endothelium in blood vessels - also consists of thin layer of connective tissue and has some smooth muscle.
*note: inflammation of any of these areas is known as: epicarditis, myocarditis, and endocarditis respectively.
Chambers of the Heart
A. Heart can be divided into 4 chambers
- 2 receiving chambers called atria
- 2 distributing chambers (pumping) called ventricles
Atria (2 big details)
- have appendage called auricle (resembles dog’s ear)
- auricles’ walls are very rough with numerous projections of muscular bundles - pectinate muscles or (musculi pectinati) - means “like a comb”
- in fetus early stages - auricle is functioning atrium - but as development progresses, walls of adjacent vessels are incorporated into final structure - thus most of atrium has a smooth wall. - right and left atria are separated by interatrial septum
- this septum has a depression called the fossa ovalis - normally blood progresses from atria to ventricles - but in embryo (fetus) blood is shunted through foramen ovale - this closes after birth to become fossa ovalis.
Ventricles (5 details)
- separated by interventricular septum internally.
- externally differentiated from atria by coronary sulcus and from each other by anterior and posterior interventricular sulci
- posses tendon like cords that attach to valves called chordae tendinae
- at the base of these cords are very large muscles called papillary muscles
- walls of ventricles are very rough with many muscular projections called trabeculae carnae
Great Vessels and Schema of the heart (4 steps)
A. Right atrium receives blood from the upper part of the body via the superior vena cava - from the lower portion of the body via the inferior vena cava
B. Right atrium then squeezes the blood into the right ventricle which pumps it out of the heart via the pulmonary trunk - this trunk then divides into the right and left pulmonary artery (one for each lung)
C. Blood then flows to the lungs for oxygenation and release of CO2 and returns to the heart via 4 pulmonary veins into the left atrium
D. Left atrium squeezes the blood into the left ventricle which pumps it into the ascending aorta and from here it goes to the arch of the aorta and the descending thoracic and abdominal aortas for distribution to the entire body.
*note the varying size and thickness of the compartments…
1. the left ventricle is much thicker walled than the right ventricle because it must pump against a great deal more resistance in pumping to the entire body than the right ventricle which pumps only to the lungs.
2. both ventricles are much thicker than either atria because they only have to squeeze blood into an adjacent chamber - and in fact a great deal of this work is accomplished simply by a negative pressure created as the ventricles expand (relax).
Valves (What they do)
- as blood passes through the heart it always goes in one direction following a contraction and never returns to the chamber from which it has just come, without first being distributed to the body. This is due to valves.
Atrioventricular Valves (AV valves)
- between atria and ventricles
1. Tricuspid Valve - between right atria and ventricle - consists of 3 “cusps” attached to the chordae tendinae and papillary muscles
2. Bicuspid Valve - between left atria and ventricle - similar to tricuspid but with only 2 cusps
Semilunar Valves (means half-moon)
- between ventricles and arteries
1. Pulmonary Semilunar Valve - between right ventricle and pulmonary trunk
2. Aortic Semilunar Valve - between left ventricle and aorta - each is composed of 3 cup like structures whose convex sides attach to the walls of the ventricles.
Blood Supply of the Heart (How?)
A. even tissues of the heart must be supplied by blood vessels.
B. heart circulation is via Coronary arteries and cardiac veins
- generally referred to as Coronary circulation.
Right Coronary Artery (4 details)
- arises opposite right cusp of aortic semilunar valve and passes to coronary sulcus on the right side and follows this sulcus around to the posterior aspect of heart.
major branches: - posterior interventricular (posterior descending) artery
- continues down posterior interventricular sulcus
- Right atrial branches - variable in number - supply right atrium - most important - Nodal Artery that supplies Sinoatrial node.
*note: often nodal artery will arise from left coronary artery
