Heart and great vessels Flashcards
Which two circuits make up the circulatory system?
Pulmonary circuit
Systemic circuit
Which two blood vessels make up the pulmonary circuit?
Pulmonary arteries carrying deoxygenated blood
Pulmonary veins carrying oxygenated blood
Which two blood vessels make up the systemic circuit?
Aorta carrying oxygenated blood
Vena cava carrying deoxygenated blood
What are the two divisions of the vena cava?
Superior vena cava supplying the head, thorax and arms
Inferior vena cava supplying the legs, abdomen and pelvis
What are the two divisions of the mediastinum?
Superior mediastinum
Inferior mediastinum
What are the contents of the superior mediastinum?
Aorta
Vena cava
Trachea
Esophagus
What are the contents of the inferior mediastinum?
Anterior mediastinum = remnant of the thymus
Posterior mediastinum = oesophagus, thoracic aorta and thoracic duct
Middle mediastinum = heart and pericardium
What determines the division of the mediastinum?
The heart position splits the mediastinum into inferior and posterior
What surrounds the heart?
A fibrous bag called the fibrous pericardium
What is found between the fibrous pericardium and the heart?
Serous pericardium
What are the two layers of the serous pericardium?
Parietal layer - layer facing the fibrous pericardium
Visceral layer - layer facing the heart
Which nerves supply the fibrous and parietal layers?
Somatic phrenic nerves
What is the shape of the heart?
Trapezoid
What features are found in the borders of the heart?
Superior border - great vessels
Inferior border - mostly right ventricle
Right border - right atrium
Left border - left ventricle
Apex
What are the two main divisions of the heart?
Atria - receives blood from veins
Ventricles - passes blood to the arteries
Aside from the major blood vessels, what are other important external features of the heart?
Vagus nerve
Ligamentum arteriosum
Which regions of the embryo form the atria?
- The true atrium
2. The sinus venosus
What is the sinus venosus?
Sac into which all the veins empty
What forms the smooth muscle of the atrial wall?
The sinus and parts of the pulmonary vein
What forms the pectinate muscle?
The true atrium
What is the pectinate muscle?
Rough part of the atrial wall
What are the two remnants of foetal circulation?
Fossa ovalis
Ligamentum arteriosum
What is the fossa ovalis?
Remnant of the foramen ovale between the right and left atria
Carries oxygenated blood from the placenta across to the left side for circulation to the growing body
What is the ligamentum arteriosum?
Remnant of the ductus arteriosus
Carries blood from the pulmonary trunk into the aorta to bypass the lungs
What are the 3 major structures making up the valves?
- Valve cusps - rounded projection of tissue forming the closure of the valve
- Chordae tendinae - tendons running from the edges of the valve cuplets to the papillary muscles
- Capillary muscles - muscles that contract before the ventricular wall to ensure the valve does not flip inside out and let the blood back into the atrium
What is the moderator band?
Important in the contraction of the papillary muscles
A branch of the conducting system acting directly on the base of the papillary muscles
What muscle type is found in the ventricle wall?
Trabeculae carneae muscle
What muscle type is found in the atrial wall?
Pectinate muscle
What are the valves of the ventricles?
Bicuspid (mitral) valve
Tricuspid valve
Pulmonary semilunar valve
Aortic semilunar valve
Why does the right ventricle have thinner walls than the rest of the heart?
The resistance in the pulmonary circuit is less than in the systemic circuit, so less pressure is required
What is the fibrous skeleton of the heart?
Connective tissue supporting the valves
Also insulates the myocardium of the atrium so the only muscular connection is the atrioventricular conducting bundle
Found in the junction of the atria and ventricles
Describe the development of the fibrous skeleton
Invasion of the connective tissue cells from the inner and outer layers of the heart during the development of the atrioventricular canal
Forms gradually so that the myocardial muscle connection is progressively reduced
What is the root of the coronary arteries?
The aorta
What are the two coronary arteries?
Right coronary artery
Left coronary artery
Where does the aorta branch into the coronary arteries?
Immediately above the semilunar valves
Form the crown at the top of the heart
Describe the divisions of the right coronary artery
Sinoatrial coronary artery
Right posterior intraventricular artery
Right marginal artery
Describe the divisions of the left coronary artery
Circumflex artery -> marginal artery
Left anterior intraventricular artery
What is the source of the cardiac veins?
The cardiac veins are branches of the great cardiac vein, which is itself a branch of the superior vena cava
What does the great cardiac vein give rise to?
Anterior cardiac vein
Middle cardiac vein
Coronary sinus
What is the nerve supply of the heart?
Sympathetic
- superior cervical
- middle cervical
- inferior cervical
- thoracic T1-T5
Parasympathetic
- vagus nerve
Describe the role of nerves in the heart
The cardiac muscle has its own intrinsic beat
But the speed and strength of the beat is moderated by autonomic nerves
Describe the initiation of the heart beat
- The beat is initiated at the SA node which lies at the junction of the superior vena cava and the sinus of the heart
- The wave of contraction crosses the atria and stimulates the atrioventricular node which lies close to the opening of the coronary sinus in the wall of the right atrium
- It crosses the atrioventricular junction in the AV bundle, which then divides into left and right branches that travel in the interventricular septum to the base of the heart
- One large branch from the right passes to the base of the right side papillary muscles to ensure they contract in time to sense the tricuspid valve
What are the branches of the aortic arch?
Right
- Brachiocephalic ->
- Right subclavian
- Right common carotid
Left
- Left common carotid artery
- Left subclavian artery
What is the origin of the vertebral artery?
The subclavian artery
What are tributaries?
Veins that drain into a bigger vein
What are the tributaries of the vena cava?
Azygous vein
Right Brachiocephalic vein ->
- right subclavian vein
- internal jugular vein
- external jugular vein
Left Branchiocephalic vein ->
- internal jugular vein
- left subclavian vein
- external subclavian vein
