Heart- internal structure and surface anatomy Flashcards
What are the surfaces of the heart and what makes up each of them?
• Sternocostal (anterior)
- right ventricle
- right atrium
- some of left ventricle
• Diaphragmatic (inferior)
- Sits on the central tendon
- Left ventricle
- Some right ventricle
- separated from the base by the coronary sinus
• Right pulmonary
- right atrium
• Left pulmonary
- left ventricle
What makes up the base of the heart?
- mainly the left atrium and pulmonary veins
* Small portion of the right atrium
Describe the position of the base of the heart
• Fixed posteriorly to the pericardium at the level of T6- T9 (when standing, T5-T8 when supine)
Where is the apex of the heart?
- Left side of the 5th intercostal space
- 8-10cm away from the midline
- More superior and lateral in children
What are the heart margins?
• Right margin
- right atrium
• Left margin
- Left ventricle
- Left auricle
• Inferior margin
- Right ventricle
- Left ventricle (apex)
External sulci
- Anterior intercostal sulcus
- Anterior inter ventricular artery
- Great cardiac vein
- Right of the apex
Coronary sulcus
- Separates the atria from the ventricles
- Right coronary sinus
- Left circumflex artery
- Cornoary sinus
What percentage of venous blood of the heart is drained by the coronary sinus?
• 60%
Posterior interventricular sulcus
- Posterior interventricualr artery
* Middle cardiac vein (posterior interventriuclar vein)
What is the function of the right atrium?
- Temporary reservoir for deoxygenated blood
* Receives blood from the superior vena cava , inferior vena cava, coronary sinus and smallest cardiac veins
What separates the right atrium from the right auricle?
- Crista terminals internally (muscular ridge)
* Sulcus terminals externally
Fossa ovalis
- On the right side of the IA septum
* Site of foramen vale in the foetus
What is the margin of fossa ovale?
Limbus fossa ovalis
At what level does the SVC open in to the atrium?
Behind the 3rd right costal cartilage
Which vessels opening into the right atrium have valves and which don’t?
Valves:
• Inferior vena cava
• Coronary sinus
No Valves:
• Superior vena cava
• Openings of the smallest cardiac veins
What is the right auricle?
- Rough surface formed by the pectinate muscles
* Provides some power of contraction without significantly thickening the cardiac wall
Where is the right ventricle
It sits on the central tendon of the diaphragm
What is the thickness of the right ventricle?
• 3-4mm
What is the outflow tract of the right ventricle?
- Infundibulum [conus arteriosus]
- Pulmonary trunk arises here
- Surface of the infundibulum is smooth
What are the muscular ridges in the wall of the right ventricle called?
Trabecular carnea
What are the 3 types of muscle on the right ventricular wall?
- Trabecular carnea
- Septomarginal trabecular (moderator band)
- Papillary muscles
Describe the septomarginal trabecular muscle
- Act as a bridge between the septum and the anterior papillary muscles
- Carries the right bundle branch of the AV bundle of the cardiac conduction system
Describe the papillary muscles
- Fibrous chords called chorda tendinae run between their apex and free edges of tricuspid valve cusps
- Contract before ventricular contraction
- Chorda tendinae prevent the exertion of cusps
- chorda tendinae from one papillary muscle attach to more than one cusp
Describe the tricuspid valve
- Closes the AV orifice
- Consists of 3 cusps (anterior, posterior and septal)
- Base of each cusp attached to right fibrous ring - anulus fibrosus
How does blood flow through the tricuspid valve?
• Forwards (inferiorly) and medially
Pulmonary valve
- Consists of 3 semilunar cusps: anterior, right and left
- on their free edge, there is a nodule of the semilunar cusp
- Each cusp forms a pulmonary sinus which helps the closure of pulmonary valves after systole
Describe the left atrium
- makes up most of the base
- Four pulmonary veins (no valve)
- Consists of the left auricle and left atrium
- Depressed area on the IA septum (falx septi) is caused by the fusion of the valve of foramen ovale (not at the same level as foramen ovale
What is the direction of the blood flow into the left ventricle?
Flows anteriorly and towards the apex
What is the thickness of the left ventricle wall?
8-12mm
Papillary muscles in the left ventricle
Anterior and posterior (2)
Mitral valve
- 2 cusps: anterior and posterior
- Bases of the cusps are attached to left fibrous ring (anulus fibrosus)
- Chorda tendinae extend between their free margins and papillary muscles
Aortic valve
- Aortic vestibule is the outflow tract of the LV
- 3 semilunar cusps: left, right and posterior
- Between the superior surface of the cusps and aortic wall are pocket like aortic sinuses (sinus valsalvae)
How does blood flow out of the aortic valve?
• Upwards, backwards and to the right
Describe the fibrous skeleton of the heart
- Structural and functional support
- 4 fibrous rings (anulus fibrosus) around AV, aortic and pulmonary valves
- Between the 4 rings are 2 trigones (right and left) and the membranous portions of the IA, IV and AV septa
What is the function of the fibrous skeleton?
• Points of attachment for the heart cusps
• Maintains the patency and integrity of AV and semilunar orifices
• Serves as an origin/insertion for atrial and ventricular muscles
• Insulates the atria from the ventricles
- allows the independent contraction of the atria and ventricles
- Atrioventricular bundle of His should be the only conduction between them
What are the layers of the cardiac wall and what is the make up of each of these layers?
• Epicardium: visceral layer of the pericardium
• Myocardium:
- atrial musculature
- ventricular musculature
- muscles arranged in spiral and circular bundles
- originate and insert on the fibrous skeleton
• Endocardium:
- Thin layer of endothelium that lines the inner surface of the walls as well as the valves
What is the blood supply to the endocardium?
Receives oxygen and nutrients directly from the chambers of the heart
Surface anatomy of each of the corners of the heart
- Right 3rd costal cartilage 2cm right of midline
- Right 6th costal cartilage 2cm right of the midline
- Left 5th costal cartilage 8cm left of midline
- Left 2nd costal cartilage 3cm left of midline
What is the surface projection of the tricuspid valve?
Behind the right half of the sternum at the level of the 4th intercostal space
What is the surface projection of the mitral valve?
Posterior to the articulation between the left 3rd costal cartilage and the sternum
What is the surface projection of the aortic valve?
Posterior to the sternum, level of the 3rd intercostal space
What is the first heart sound
AV valves - tricuspid and mitral
• Systole
What is the second heart sound?
Semilunar valves: aortic and pulmonary
• Diastole
Where is the tricuspid valve best heard
• just left of the lower part of the sternum near the 5th intercostal space
Where is the mitral valve best heard?
apex of the heart, left 5th intercostal space at the mid clavicular line
Where is the aortic valve best heard?
• Medial end of the right second intercostal space
where is the pulmonary valve best heard?
Medial end of the left second intercostal space
How does blood flow through the aortic valve?
Superiorly and to the right
How does blood flow through the pulmonary valve?
Superiorly and to the left
How does blood flow through the tricuspid valve?
Anteriorly and medially (towards the left)
How does blood flow thorough the mitral valve?
Anteriorly and inferiorly to the apex
