Anatomy Of The Heart Flashcards
What is the shape and primary function of the heart?
Cone-shaped, muscular pump
The heart functions to pump blood throughout the body.
Where is the heart located?
In the thorax between the lungs (region of mediastinum)
It is protected by the ribs and sternum.
What is the apex of the heart?
Lies in the 5th intercostal space in the midclavicular line
The apex indicates the lower tip of the heart.
What is the fibrous pericardium?
Inelastic, made of dense connective tissue (network of capillary fibres)
It fuses inferiorly with the diaphragm and superiorly with great vessels, preventing overfilling of the heart and anchoring it in position
What are the two layers of the serous pericardium?
Parietal layer (outer layer) and visceral layer (inner layer)
The visceral layer is also known as the epicardium.
What is the function of the pericardial cavity?
Contains pericardial fluid, prevents friction & allows heart to move smoothly
overproduction can cause inflammation
The pericardial cavity is a potential space between the parietal and visceral layers.
What are the three layers of the heart wall?
- Endocardium: inner layer - endothelium (simple squamous epithelium)
- Myocardium: middle layer - cardiac muscle (main layer, forms atria and ventricles)
- Epicardium: outer layer - visceral pericardium
What chambers make up the heart?
- Right atrium (RA)
- Left atrium (LA)
- Right ventricle (RV)
- Left ventricle (LV)
These chambers are responsible for receiving and pumping blood.
What are the great vessels connected to the heart?
- Superior vena cava - delivers blood to RA from head, neck and upper limbs
- Inferior vena cava - carries blood to RA from trunk, viscera and lower limbs
- Pulmonary trunk & arteries
- Pulmonary veins (4 of them)
- Aorta
These vessels are essential for blood circulation to and from the heart.
What is the function of heart valves?
Prevent backflow of blood
There are 4 heart valves:
- 2x Atrioventricular valves
- 2x Semilunar valves
Heart valves ensure unidirectional blood flow through the heart chambers.
Name the two types of atrioventricular (AV) valves.
- Tricuspid (right AV valve) = has 3 cusps
- Bicuspid/mitral (left AV valve) = has 2 cusps
These valves separate the atria from the ventricles.
What are the semilunar valves?
- Pulmonary valve
- Aortic valve
These valves guard the entrances to the aorta and pulmonary trunk.
What is the role of chordae tendineae and papillary muscles?
Anchors AV valves and prevents backflow
Chordae tendineae connect the valves to the papillary muscles.
What is the cardiac conducting system responsible for?
Coordinating effective heart contraction
It consists of non-contractile cells that initiate electrical impulses.
What are the shortcuts in fetal circulation?
- Foramen ovale (window) = connects the right to the left atria, bypassing the right ventricle and pulmonary system
- Ductus arteriosus = connects the pulmonary trunk to the arch of the aorta, bypassing the pulmonary system and left side of heart (goes to aorta instead of lungs)
- Ductus venosus = connects the umbilical vein to the inferior vena cava (as processed by the mother), bypasses the liver
What happens to the foramen ovale at birth?
Closes to become fossa ovalis
This closure is due to increased left atrial pressure after birth.
How is blood flow through the heart sequenced?
RA → RV → Lungs → LA → LV → Aorta
This sequence describes the pathway of blood circulation.
What is the significance of the coronary circulation?
Supplies blood to the myocardium during ventricular relaxation
It consists of arteries and veins that specifically serve the heart muscle.
What does an electrocardiogram (ECG) measure?
The electrical activity of the heart
ECGs are crucial for assessing heart function.
What is the fibrous skeleton of the heart?
- Bands of fibrous connective tissue between the atria and ventricles
- Electrically separates the atria from the ventricles so they don’t contract at the same time
- Encircles the pulmonary trunk and aorta (leaving the ventricles)
- Heart valves suspended from it
Describe atrioventricular valves
- located between the atria and ventricles
- opened by the blood flowing from atria to the ventricles
- The cusps are anchored by chordae tendinae to papillary muscles (form part of heart wall)
- Contraction of papillary muscles prevents eversion of the valves and therefore backflow of blood into the atria
When do atrioventricular valves open/close?
Open when ventricular pressure is less than atrial pressure
Close when ventricular pressure is greater than atrial pressure
Describe semilunar valves
- Guards the entrances of the aorta and pulmonary trunk
- Opened by the force of blood (when pressure increases) as the ventricles contract
- Blood flows backwards in the aorta and pulmonary trunk during ventricular relaxation
- This pools in the cusps and pushes them shut
- Thus preventing backflow of blood into the ventricles
Internal features of the heart
What arteries and veins does the coronary circulation consist of?
Left coronary artery (LCA)
- anterior interventricular = left anterior descending (down between ventricles)
- Circumflex = wraps around heart
Right coronary artery (RCA)
- marginal artery = runs along lower border of right ventricle
- posterior interventricular = runs down ventricles at the back
- Great, middle and small cardiac veins drain into the coronary sinus which empties into the right atrium
- The anterior cardiac veins (come from right ventricle) drain directly into the right atrium
What is angiography?
Dye used to examine patency of coronary vessels
What are the non contractile cells that initiate electrical impulses?
- Sinoatrial (SA) node = in atrium
- Atrioventricular (AV) node = between the 2 atria, next to the ventricles
- AV bundle (bundle of His) = passes through septum, slows down passage of impulse
- Right & left bundle branches
- Purkinje fibres = spread backwards up the heart
What positions are non contractile cells that initiate electrical impulses located in?
How is foetal circulation different from usual circulation?
- oxygen and nutrients are received from the placenta via the umbilical vein
- needs to bypass non-functional lungs
What are the changes in foetal circulation at birth?
- Ductus venosus (causes bypassing of liver) becomes ligamentum venosum
- Foramen ovale (gap between the right and left atria) becomes fossa ovalis
- Ductus arteriosus (between pulmonary trunk and aorta) becomes ligamentum arteriosum
