Cardiovascular System Flashcards
What is the Mediastinum?
The mediastinum is the central compartment of the thoracic cavity, situated between the lungs.
What does the mediastinum contain and consist of?
It contains all the thoracic structures except the lungs and is a highly mobile region in the living because it consists primarily of hollow visceral structures which are joined by loose connective tissue.
Describe where the inferior mediastinum is situated.
The mediastinum extends from the superior thoracic aperture to the diaphragm and from the sternum and costal cartilages to the bodies of the thoracic vertebrae.
Name the 3 parts of the inferior mediastinum.
- Anterior mediastinum
- Middle mediastinum
- Posterior mediastinum
Describe where the superior mediastinum is situated.
Extends inferiorly from the superior thoracic aperture to the horizontal plane, which includes the sternal angle and passes approximately through the junction of T4 and T5 vertebrae posteriorly.
What does the superior mediastinum contain?
Contains the roots of the great vessels and the trachea.
Define the sternal angle.
The sternal angle is the joint between the manubrium (top part) and the body (middle part) of the sternum. It also marks the division of the superior and inferior mediastinum.
At what vertebral level is the sternal angle found?
Between T4 and T5.
Which part of the inferior mediastinum contains the heart?
The middle mediastinum.
What lies within the fibrous pericardial sac?
The heart.
The pericardial sack is fused superiorly with what?
The aorta and pulmonary trunk.
The pericardial sac is blended inferiorly with what?
The central tendon of the diaphragm.
The pericardial sac has a tough fibrous outer layer (the fibrous pericardium) which protects the heart against sudden over filling by doing what?
Physically preventing overexpansion.
What is the internal surface of the fibrous pericardium lined with and what does it do?
A serous membrane which passes onto the surface of the heart to provide a continuous membrane surrounding the fluid filled pericardial cavity.
What is the epicardium?
The visceral layer of the serous pericardium.
What does the fluid in the pericardial cavity do?
The fluid in the pericardial cavity allows the heart to beat in an almost frictionless environment.
Name the 2 circulatory systems.
Pulmonary and systemic systems.
Name the 4 chambers of the heart and their relative positions.
Left & Right Atria. Left and Right ventricles. The atria are the upper chambers.
What are the chambers of the heart made of?
Specialised cardiac muscle known as myocardium.
True or false? Expulsion of blood from the hearts chambers is a passive process.
False. Contraction of the cardiac muscle pushes blood out of the chambers. The passive process of relaxation causes the chambers to refill.
Define Systole.
Contraction of the ventricles.
Define Diastole.
Relaxation of the ventricles.
Pulmonary, derived from the Latin for lungs, is used to describe what?
Objects or systems that are related to the lungs.
Is the pulmonary circulation pumped at a high or low pressure? Why?
The pulmonary circulation is pumped at a low pressure. Not much force is required to send blood the short distance through the lungs from the right to the left heart and high pressure in pulmonary capillaries would force fluid out of the blood, into the lung tissue and we would drown.
In pulmonary circulation, blood leaves the right ventricle through what?
The pulmonary arteries.
In pulmonary circulation, blood returns to the heart from the lungs through what vessels?
Pulmonary veins.
In pulmonary circulation, blood enters which chamber of the heart after returning from the lungs?
The left atrium.
In pulmonary circulation what does the pulmonary trunk divide into?
The right and left pulmonary arteries.
Define Systemic.
Affecting the whole body.
Which chamber of the heart is the origin of systemic circulation?
The left ventricle.
Which chamber of the heart is the end of systemic circulation?
The right atrium.
Why does the systemic circulation operate at a high pressure (compared to the pulmonary)?
Considerable force is required to adequately perfuse all the tissues in the human body and the blood has a much larger distance to travel.
Arteries carry _____ blood?
Oxygenated.
Veins carry _____ blood?
Deoxygenated.
From superficial to deep, name the 3 layers of the heart.
- Epicardium
- Myocardium
- Endocardium
What separates the atria?
The Interatrial (IA) septum.
What separates the ventricles?
The Interventricular (IV) septum.
Why is the left ventricle especially muscular?
As it has to push blood around the whole body.
The systemic circulation drains into the right atrium through what vessels?
The superior and inferior vena cava.
Describe the epicardium.
The epicardium consists of a layer of connective tissue and provides a protective layer over the heart.
Describe the myocardium.
This is the muscular component of the heart wall, it consists of myocytes or cardiac muscle cells.
Describe the endocardium.
This layer of epithelium and connective tissue lines the heart and covers the heart valves. The endocardium is continuous with the endothelial lining of blood vessels.
At rest when do the atria contract?
At the end of diastole.
During exercise, how does atrial contraction change?
During exercise, atrial contraction becomes essential to match the speed of ventricular filling to the increased rate of ventricular contraction.
Which have thicker walls, the atria or the ventricles? Why?
The ventricles. The atria only need to pump blood into the ventricles therefore have little muscle whilst the ventricles pump blood much further therefore have thicker, more muscular walls.
How are muscle fibres in the ventricles arranged?
Muscle fibres in the ventricles are arranged so that ventricular contraction progresses upwards in a spiral from the apex of the heart, towards the vessels leading out of the ventricles.
Where does the de-oxygenated blood carried by the superior vena cava come from?
The systemic circulation superior to the heart.
Where does the de-oxygenated blood carried by the inferior vena cava come from?
The systemic circulation inferior to the heart.
Name the 4 pulmonary veins.
Left superior and left inferior pulmonary veins and the right superior and right inferior pulmonary veins.
What do the valves of the heart separate?
Atria from ventricles, and ventricles from great vessels.
What would happen to the heart if it lacked valves?
If it were not for the valves of the heart, contraction of the wall surrounding the ventricles would send the blood both forwards, into the pulmonary artery and aorta, and backwards into the atria. Relaxation of the ventricles would also allow blood to re-enter the heart from the pulmonary artery and aorta.
What do atrioventricular valves do?
They prevent backflow of blood from the ventricles into the atria during systole.