Cardiovascular System
The cardiovascular system is made up of the heart, blood vessels, and blood.
Heart
The heart is a self-adjusting double pump that propels blood around two circulatory
systems in series, the pulmonary and systemic systems.
It consists of four chambers: two atria and two ventricles.
The heart is formed from specialised, cardic muscle known as myocardium. Contraction of
myocardium pushes blood out of the chambers. Relaxation of a chamber allows blood to
flow or be pushed into it, but the heart does not actively draw blood in.
Each cycle of contraction and relaxation is known as a heartbeat. Contraction of the
ventricles is systole and relaxation of the ventricles is diastole.
The pulmonary circulation
Pulmonary is derived from the Latin for lungs and is used to describe objects or systems
that are related to the lungs.
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.
Blood pumped to the lungs from the right ventricle has a very low oxygen concentration.
Blood leaves the right ventricle through the pulmonary trunk which divides to give right and
left pulmonary arteries.
Oxygenation of this blood occurs in the lungs before it returns to the heart through a series
of pulmonary veins which enter the left atrium.
The systemic circulatory system
Systemic: refers to the whole body.
,The systemic circulation feeds into and out of all the organs of the body except the lungs.
The left ventricle is the origin of the systemic circulation, and the right atrium is its
termination.
The systemic circulation operates at a high pressure (compared to the pulmonary
circulation). Considerable force is required to adequately perfuse all the tissues in the
human body and the blood has a much larger distance to travel from left to right heart than
right to left.
The supply to the organs is rich in oxygen, the blood returning to the heart is low in oxygen.
Anatomy of the thorax
The thorax sits superiorly in the trunk of the body.
Thoracic cage
The thoracic cage protects the contents of the thorax. It is made up of the ribs, costal
cartilage, sternum (anteriorly), and thoracic vertebrae (posteriorly). These structures,
along with thoracic muscles, help form the boundaries of the thorax.
The thoracic cavity can be split into regions. The mediastinum sits centrally.
Mediastinum
Mediastinum is the central compartment of the thoracic cavity, situated between the
lungs. The mediastinum extends from the superior thoracic aperture (superiorly) to the
diaphragm (inferiorly) and from the sternum and costal cartilages (anteriorly) to the bodies
of the thoracic vertebrae (posteriorly).
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.
The sternal angle is the joint between the manubrium (top part) and the body (middle part)
of the sternum.
,A horizontal plane can be drawn from the sternal angle to the level between T4 and T5. This
imaginary plane is known as the thoracic plane.
The thoracic plane splits the mediastinum into two main compartments. These two
compartments are known as the superior mediastinum and the inferior mediastinum. The
inferior mediastinum is then further subdivided into the anterior mediastinum, middle
mediastinum, and posterior mediastinum.
Superior Mediastinum Superior mediastinum contains the oesophagus and the
trachea. It also contains neurovasculature: the arch of the
aorta and its branches, the superior vena cava and its
tributaries, left and right phrenic nerves, left and right
vagus nerves, the thoracic duct, and the sympathetic
chains.
Anterior Mediastinum Anterior mediastinum doesn’t contain a lot of structures.
It mainly consists of fat and the thymus.
Middle Mediastinum Middle mediastinum mainly contains the heart and
pericardium. It also contains the roots of the great
vessels, left and right phrenic nerves, left and right vagus
nerves, and the cardiac plexus.
Posterior Mediastinum Posterior mediastinum contains the descending aorta and
branches, the oesophagus, the thoracic duct, the azygos
system of veins, and the sympathetic chains.
Some structures will sit in both the superior and inferior mediastinum as they travel
through the thorax. For example, the oesophagus travels through the neck into the superior
mediastinum, then into the inferior mediastinum before entering the abdomen.
Azygos system of veins
, A H-shaped configuration of the azygos, hemiazygos, and accessory hemiazygos veins.
This system drains the posterior thoracic wall.
Sympathetic chains
The sympathetic chains are part of the sympathetic nervous system. The sympathetic
chain (also known as the sympathetic trunk) is external to the spinal column, adjacent to
the vertebral bodies. It is paired structure (one on each side of the body).
Thoracic duct
The thoracic duct is the main lymphatic vessel for the return of chyle/lymph to the
systemic venous system. It drains lymph from both lower limbs, abdomen (except the
convex area of the liver), left hemithorax, left upper limb and left side of face and neck.
Thymus
The thymus is a T-cell producing lymphoid organ that plays a role in the development of the
immune system, particularly, maturation of T cells.
Phrenic nerve
A paired nerve (one on the left and one on the right) that supplies the diaphragm. It comes
from the nerve roots C3, C4, and C5.
Vagus nerve
The tenth cranial nerve (CNX). It is paired (one on the left and one on the right). It provides
the bulk of the parasympathetic input to the gastrointestinal system and to the heart. It is a
complex mixed sensory, motor and parasympathetic nerve.
Pericardium
The pericardium is a membrane that covers the heart. It is positioned within the middle
mediastinum of the thorax.
It consists of two layers:
The cardiovascular system is made up of the heart, blood vessels, and blood.
Heart
The heart is a self-adjusting double pump that propels blood around two circulatory
systems in series, the pulmonary and systemic systems.
It consists of four chambers: two atria and two ventricles.
The heart is formed from specialised, cardic muscle known as myocardium. Contraction of
myocardium pushes blood out of the chambers. Relaxation of a chamber allows blood to
flow or be pushed into it, but the heart does not actively draw blood in.
Each cycle of contraction and relaxation is known as a heartbeat. Contraction of the
ventricles is systole and relaxation of the ventricles is diastole.
The pulmonary circulation
Pulmonary is derived from the Latin for lungs and is used to describe objects or systems
that are related to the lungs.
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.
Blood pumped to the lungs from the right ventricle has a very low oxygen concentration.
Blood leaves the right ventricle through the pulmonary trunk which divides to give right and
left pulmonary arteries.
Oxygenation of this blood occurs in the lungs before it returns to the heart through a series
of pulmonary veins which enter the left atrium.
The systemic circulatory system
Systemic: refers to the whole body.
,The systemic circulation feeds into and out of all the organs of the body except the lungs.
The left ventricle is the origin of the systemic circulation, and the right atrium is its
termination.
The systemic circulation operates at a high pressure (compared to the pulmonary
circulation). Considerable force is required to adequately perfuse all the tissues in the
human body and the blood has a much larger distance to travel from left to right heart than
right to left.
The supply to the organs is rich in oxygen, the blood returning to the heart is low in oxygen.
Anatomy of the thorax
The thorax sits superiorly in the trunk of the body.
Thoracic cage
The thoracic cage protects the contents of the thorax. It is made up of the ribs, costal
cartilage, sternum (anteriorly), and thoracic vertebrae (posteriorly). These structures,
along with thoracic muscles, help form the boundaries of the thorax.
The thoracic cavity can be split into regions. The mediastinum sits centrally.
Mediastinum
Mediastinum is the central compartment of the thoracic cavity, situated between the
lungs. The mediastinum extends from the superior thoracic aperture (superiorly) to the
diaphragm (inferiorly) and from the sternum and costal cartilages (anteriorly) to the bodies
of the thoracic vertebrae (posteriorly).
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.
The sternal angle is the joint between the manubrium (top part) and the body (middle part)
of the sternum.
,A horizontal plane can be drawn from the sternal angle to the level between T4 and T5. This
imaginary plane is known as the thoracic plane.
The thoracic plane splits the mediastinum into two main compartments. These two
compartments are known as the superior mediastinum and the inferior mediastinum. The
inferior mediastinum is then further subdivided into the anterior mediastinum, middle
mediastinum, and posterior mediastinum.
Superior Mediastinum Superior mediastinum contains the oesophagus and the
trachea. It also contains neurovasculature: the arch of the
aorta and its branches, the superior vena cava and its
tributaries, left and right phrenic nerves, left and right
vagus nerves, the thoracic duct, and the sympathetic
chains.
Anterior Mediastinum Anterior mediastinum doesn’t contain a lot of structures.
It mainly consists of fat and the thymus.
Middle Mediastinum Middle mediastinum mainly contains the heart and
pericardium. It also contains the roots of the great
vessels, left and right phrenic nerves, left and right vagus
nerves, and the cardiac plexus.
Posterior Mediastinum Posterior mediastinum contains the descending aorta and
branches, the oesophagus, the thoracic duct, the azygos
system of veins, and the sympathetic chains.
Some structures will sit in both the superior and inferior mediastinum as they travel
through the thorax. For example, the oesophagus travels through the neck into the superior
mediastinum, then into the inferior mediastinum before entering the abdomen.
Azygos system of veins
, A H-shaped configuration of the azygos, hemiazygos, and accessory hemiazygos veins.
This system drains the posterior thoracic wall.
Sympathetic chains
The sympathetic chains are part of the sympathetic nervous system. The sympathetic
chain (also known as the sympathetic trunk) is external to the spinal column, adjacent to
the vertebral bodies. It is paired structure (one on each side of the body).
Thoracic duct
The thoracic duct is the main lymphatic vessel for the return of chyle/lymph to the
systemic venous system. It drains lymph from both lower limbs, abdomen (except the
convex area of the liver), left hemithorax, left upper limb and left side of face and neck.
Thymus
The thymus is a T-cell producing lymphoid organ that plays a role in the development of the
immune system, particularly, maturation of T cells.
Phrenic nerve
A paired nerve (one on the left and one on the right) that supplies the diaphragm. It comes
from the nerve roots C3, C4, and C5.
Vagus nerve
The tenth cranial nerve (CNX). It is paired (one on the left and one on the right). It provides
the bulk of the parasympathetic input to the gastrointestinal system and to the heart. It is a
complex mixed sensory, motor and parasympathetic nerve.
Pericardium
The pericardium is a membrane that covers the heart. It is positioned within the middle
mediastinum of the thorax.
It consists of two layers:
