Mediastinum & Heart II Flashcards
Overview of the heart
- Do atria or ventricles have thicker walls?
- What chamber has the thickest wall?
- What are the septum names?
- What are the grooves on the heart’s surface?
Overview of the heart
Ventricles have thicker walls than atria because ventricles pump blood to lungs or body, while atria pump blood to adjacent chambers
Left ventricle has thick wall because it pumps blood to the rest of the body
Interatrial septum separates the atria
Interventricular septum separates ventricles
Coronary vessels sit in the grooves of the heart’s surface:
- Coronary (atrioventricular) groove
- Anterior interventricular groove
- Posterior interventricular groove
Describe flow of blood through heart (including if it is oxygen rich or poor blood)
SVC, IVC, and coronary sinus give oxygen POOR blood to right atrium
Right atrium pumps blood though tricuspid (right atrioventricular) valve into right ventricle
Right ventricle pumps blood through pulmonary valve into pulmonary trunk
Pulmonary trunk branches off into pulmonary arteries and head to the lungs so blood can get oxygenated
Pulmonary veins give oxygen RICH blood to left atrium
Left atrium pumps blood through mitral (left atrioventricular) valve into left ventricle
Left ventricle pumps blood through aortic valve, which pushes oxygen rich blood to rest of body
Arterial supply of the heart: coronary arteries
- Where do coronary arteries arise?
- Map out the coronary arteries and their branches
Arterial supply of the heart: coronary arteries
Coronary arteries arise from the ascending aorta
Right coronary artery (RCA)
- Travels in coronary groove
- Gives quickly off to sinoatrial (SA) nodal branch
- Gives off to right marginal branch at inferior border of heart
- Gives off to posterior interventricular branch, which occupies posterior interventricular groove
Left coronary arter (LCA)
- Gives off quickly to circumflex branch, which occupies coronary groove
- Circumflex branch gives rise to left marginal branch
- Gives off to left anterior descending (LAD) aka anterior interventricular branch, which occupies the anterior interventricular groove and runs towards apex of heart
What is an MI?
Myocardial infarction
When an area of the heart muscle has undergone necrosis, is usually caused by ischemia (lack of adequate blood supply) due to occlusion of coronary arteries
What is coronary bypass surgery?
Coronary bypass surgery is a technique used to shunt blood around narrowed or blocked coronary arteries
Venous drainage of the heart
- What drains blood from the heart?
- Where is it located?
- Where does it drain to?
- What are the branches?
Venous drainage of the heart
Coronary sinus
Located in posterior portion of coronary groove
Drains into right atrium
Collects blood from:
- Great cardiac vein
- Middle cardiac vein
- Small cardiac vein
Right atrium
- What are all of the openings?
- What are the structures of right atrium?
Right atrium
Openings: SVC, IVC, coronary sinus
Right auricle is an appendage of the right atrium with pectinate muscles
Crista terminalis is a ridge separating the auricle and the smooth posterior wall
Fossa ovalis is an oval shaped depression in the interatrial septum that is the remnant of the embryonic foramen ovale
Tricuspid valve (right atrioventricular valve)
- How many cusps?
- When does it open?
Tricuspid valve (right atrioventricular valve)
3 cusps
Opens passively during atrial contraction
Right ventricle
- What are the structures in right ventricle?
- How is backflow prevented?
Right ventricle
Wall has trabecular carneae muscle
3 papillary muscles come off wall - anterior, posterior, and septal
Chordae tendineae connect papillary muscles to cusps of tricuspid valve
Septomarginal trabecula (moderator band) - muscle bundle extending from interventricular septum to anterior papillary muscle, and carries portion of right bundle branch
Back flow of blood into the right atrium during ventricular contraction is prevented by the papillary muscle / chordae tendineae function to hold the tricuspid valve closed
Pulmonary valve
- How many cusps and sinuses?
- Explain how valve works
Pulmonary valve
3 cup-like cusps and 3 sinuses
When ventricles contract, valve opens and blood passes through to pulmonary trunk
When ventricles relax, the blood falls down trunk and fills the sinuses above the cup-like cusps, and the filled sinuses hold the valve closed
Left atrium
- What opens into left atrium?
- What are the structures of left atrium?
Pulmonary veins open up into left atrium
Left auricle has pectinate muscles
Mitral valve (left atrioventricular valve)
- How many cusps?
- When does it open?
Mitral valve (left atrioventricular valve)
2 cusps
Opens passively during atrial contraction
Left ventricle
- Thick or thin walls?
- What are the structures of left ventricle?
- How is backflow prevented?
Left ventricle
Walls are twice as thick as right ventricle
Wall has trabecular carneae muscle
2 papillary muscles come off wall - anterior and posterior
Chordae tendineae connect papillary muscles to cusps of mitral valve
Backflow of blood into the left atrium during ventricular contraction is prevented by the papillary muscle / chordae tendineae function to hold the mitral valve closed
Aortic valve
- How many cusps and sinuses?
- Explain how valve works
- Where does blood in sinuses go?
Aortic valve
3 cup-like cusps and 3 sinuses
When ventricles contract, valve opens and blood passes through to ascending aorta
When ventricles relax, the blood falls down aorta and fills the sinuses above the cup-like cusps, and the filled sinuses hold the valve closed
Blood in the aortic sinuses flow into coronary arteries
Explain fetal circulation
- Include the two bypasses
- Include when blood is oxygen rich, poor, or mixed
Oxygen rich blood enters fetus via umbilical vein
As O2 rich blood reaches liver, it is shunted past organ via ductus venosus (blood is already filtered by mother)
Ductus venosus leads directly to IVC, which carries the O2 rich (but now mixed with O2 poor blood from the structures inferior to the diaphragm) to the right atrium
Since there is no need to oxygenate the blood in the lungs (not functioning at this time anyways), there are two bypasses in fetal heart
- Blood from right atrium passes through the foramen ovale into the left atrium, then goes to left ventricle, aorta, and body
- Blood that does not enter the right ventricle and pulmonary trunk (which is typically O2 poor blood from the SVC, which does not tend to mix with the O2 rich blood from the IVC) bypasses the pulmonary arteries by flowing through the ductus ateriosus, a shunt to the arch of the aorta, then to the body
What are the 3 bypasses in fetal circulation?
Ductus venosus (liver)
Foramen ovale (heart going from right to left atrium)
Ductus arteriosis (heart going from pulmonary trunk to aorta)
Explain lack of blood flow through pulmonary circulation for fetuses
In the fetus, very little blood flows through the pulmonary circulation (to and from the lungs) due to the high vascular resistance in the collapsed fetal lungs
Instead, blood follows the path of least resistance (e.g. through the foramen ovale or ductus arteriosus)
At birth, with the first intake of air, the flow of blood takes on the adult pattern as the vascular resistance in the lungs is drastically reduced
Summary of fetal circulation
Umbilical vein (oxygen rich blood)
Ductus venous
IVC
Right atrium
- Foramen ovale
- Left atrium
- Left ventricle
- Aorta
- Body
SVC (oxygen poor blood returned from the body)
- Right atrium
- Right ventricle
- Pulmonary trunk
- Ductus arteriosus
- Aortic arch
- Body
Body to umbilical arteries (oxygen poor blood)
What are the adult remnants of the fetal bypasses in the heart? (There are others located in the abdomen)
Ligamentum arteriosum - fetal ductus arteriosus (closed by 3 weeks after birth)
Fossa ovalis - fetal foramen ovale (closed by 3 months after birth)
Parts of the heart conduction system
Sinoatrial (SA) node
Atrioventricular (AV) node
Atrioventricular (AV) bundle / Bundle of His
Sinoatrial (SA) node
- Location?
- What does it do?
- Stimulated by? Inhibited by?
Sinoatrial (SA) node
Located at the junction of the SVC and right atrium
Pacemaker of the heart, initiates electrical impulse for atrial contraction
Stimulated by sympathetic innervation - increases HR
Inhibited by parasympathetic innervation via vagus nerve - decreases HR
Atrioventricular (AV) node
- Location?
- What does it do?
Atrioventricular (AV) node
Located at the interatrial septum
Receives signal of the SA node via atrial walls
Sends signal to ventricles via the AV bundle
Atrioventricular (AV) bundle / Bundle of His
- Location?
- What does each bundle stimulate?
Atrioventricular (AV) bundle / Bundle of His
Located at the interventricular septum
Divides into right and left bundles
Right bundle stimulates the interventricular septum, walls, and papillary muscles of the right ventricle via moderator band
Left bundle stimulates the interventricular septum, walls, and papillary muscles of the left ventricle
Esophagus
- Location?
- Where does it pass through diaphragm?
Esophagus
Fibromuscular tissue flattened between the pharynx and stomach
Posterior to trachea and superior to mediastinum
Right side of thoracic aorta
Posterior to base of heart
Passes through esophageal hiatus at T10
Thoracic (descending) aorta
- Left or right of midline?
- Where does it pass through diaphragm?
- Anterior midline branches?
- Paired branches?
Thoracic (descending) aorta
Lies to left of midline
Passes through aortic hiatus at T12
Anterior midline branches - bronchial arteries and esophageal arteries
Paired branches - posterior intercostal arteries (part of VAN)
Azygos system
- Do this system have valves?
- Describe location of three parts of azygos system
- Where does he azygos vein collect blood from and drain to?
Azygos system - no valves
Azygos vein
- Lies to right of midline
- Collects blood from the mediastinal structures (via bronchial and esophageal veins), thoracic wall (via intercostal and subcostal veins), and posterior abdominal wall (via lumbar veins)
- Drains primarily into the SVC
Accessory hemiazygos vein
- Lies to left of midline
- Courses down posterior to esophagus to join azygos vein at T9 level
Hemiazygos vein
- Lies to left of midline, inferior to accessory hemiazygos vein
- Courses up posterior to esophagus to join the azygos vein at T9 level
Thoracic duct
- Function?
- Location?
- Where does it drain?
Thoracic duct
Collects lymph from most of body
Courses posterior to the esophagus on the anterior surface of the vertebral bodies, between the azygos vein and the aorta
Drains into the left venous angle (where the subclavian and left internal jugular veins join)
Right lymphatic duct
- Function?
- Where does it drain?
Right lymphatic duct
Collects lymph from the right upper quadrant (right side of the head / neck / thorax and right upper extremity)
Drains into right venous angle (where subclavian and right internal jugular veins join)
Sympathetic trunks
- Function?
- Location?
- How does it connect to the ventral rami?
- What kind of innervation and how does it provide innervation to the abdominal organs?
Sympathetic trunks - right and left
Connects series of paravertebral ganglia
Extends from the cervical to sacral region
Connected to ventral rami (e.g. intercostal nerves, which are the ventral rami of thoracic spinal nerves) via the white (entrance) and gray (exit) commincans
Provides sympathetic innervation to the abdominal organs via the thoracic splanchnic nerves
Thoracic splanchnic nerves
- What are the three parts?
- Where do they emerge?
- What kind of fibers do they carry?
Thoracic splanchnic nerves
The greater, lesser, and least splanchnic nerves emerge from the sympathetic trunks in the posterior mediastinum
They carry preganglionic fibers that will synapse in the prevertebral ganglia in the abdomen to supply the abdominal viscera
