Cardiovascular System Flashcards
What does the circulatory system consist of? (3)
Heart
Blood vessels
Blood
What kind of circulatory system is in humans?
A closed system used to transport essential food, oxygen, nutrients and water to the cells of the body.
What does a closed circulatory system mean? (3)
The transport medium (blood) is contained in blood vessels and is not in direct contact with tissues.
The medium is under pressure as it is pumped around the body and returns directly to the heart.
This maintains pressure of the blood and ensures blood flows faster and blood flow can be directed.
What is the structure d the heart? (4)
It is hollow
Come-shaped muscular organ
Apex is at the bottom
Base is at the top
What is the position of the heart? (3)
Lies in the mediastinum of the thoracic cavity
Lies posteriorly to the sternum and between the lungs
Lies at an oblique angle, two thirds of which lie to the left of the bodies midline
Where is the apex of the heart positioned?
It is about 9cm to the left of the midline at the level of the 5th intercostal space
Where is the base of the heart positioned?
It extends to the 2nd rib.
What organ is inferiorly associated with the heart?
Diaphragm
What organ is associated superiorly to the heart? (4)
Aorta
Superior vena cava
Pulmonary artery
Pulmonary veins
What organ is laterally associated with the heart?
Lungs
What organs are located posteriorly to the heart? (6)
Oesophagus
Trachea
Left and right bronchus
Descending aorta
Inferior vena cava
Thoracic vertebrae
What organs are located anteriorly to the heart? (3)
Sternum
Ribs
Intercostal muscles
What are the three layers (structure) of the heart?
Pericardium (outer layer)
Myocardium (middle layer)
Endocardium (inner layer)
What is the purpose of serous fluid in the heart?
Lubrication
Allows layers to slide over eachother during each pump of the heart
What is the outer pericardium also known as?
Heart sac
What is the pericardium?
It is the outermost layer of the heart
Outer sac is fibrous
Inner sac is double layer of serous membrane
What is the two key characteristics of the outer fibrous sac of the pericardium?
It is continuous with the tunica adventitia (extra coat) of the blood vessels
Attached to the diaphragm below
What is the tunica externa?
It is the coating on the outer surface of the blood vessels
What is the tunica intima?
The most inner region of a blood vessel
Has endothelium, subendothelial layer was internal elastic lamina
What is tunica media?
The middle of the blood vessel, in between the tunica intima and tunica externa.
Has external elastic lamina
What is the purpose of an outer fibrous sac of the pericardium?
Prevents over-distension of the heart
What is the inner layer of the pericardium and explain the outer layer and how they both work? (4)
It consists of a double serous membrane
Outer layer is called the parietal pericardium and lines the fibrous sac
The inner layer is called the visceral pericardium and is adherent (attached) to the heart muscles
There is a potential space in between these that contain serous fluid and prevents friction
What lines the fibrous sac of the pericardium?
Parietal pericardium (outer layer)
What is adherent (attached) to the heart muscle?
Visceral pericardium (inner layer)
What is the pericardium?
It is the membrane enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane
What is the myocardium composed of? (2)
Specialised cardiac muscle found only in the heart
It is striated and is not under voluntary control
What happens when an impulse is initiated in the heart in the myocardium?
It spreads from cell to cell (cellular communication) via the branches and intercalated discs
What are the key features of the myocardium in the heart? (2)
It is thicker at the apex
The left ventricle has a thicker myocardium than the right because the right only has to pump blood to the lungs whereas the left has to pump around the whole body so needs to create more pressure.
What is the network of specialist conducting fibres responsible for?
Transmitting the hearts electrical signals also running through the myocardium
What separates the atria and ventricles and what is it’s key characteristic? (2)
They are separated by fibrous tissue that DOES NOT conduct electrical impulses.
Therefore it is up to the electrical conducting system to transmit impulses from the atria to the ventricles.
What is the endocardium?
It is what lines the chambers and valves of the heart
What does the endothelium consist of?
Flattened squamous epithelium
What is the purpose of the flatted squamous epithelium in the endothelium of the heart?
It allows a smooth passage of blood flow inside the heart and prevents blood clotting.
It is continuous with the tunica intima in the blood vessels
How is the inferior of the heart divided into the right and left hand side?
By the septum
What is the septum composed of?
It is myocardium covered by endothelium.
How are atrioventricular valves formed?
They are formed by double folds of endocardium strengthened by a little fibrous tissue
What is the right atrioventricular valve also known as?
Tricuspid valve
What is the left atrioventricular valve also known as?
Bicuspid valve
How does blood go from the atrium into the ventricles?
The valves open under pressure in the atrium
How does the valves close after blood travels from the atrium into the ventricles?
The pressure forces them shut
What structure prevents valves opening upwards?
Chordae tendineae
Why are valves extended inferiorly and open downwards?
Have papillary muscles
What are papillary muscles?
Extensions of myocardium
Describe pulmonary circulation? (3)
Deoxygenated blood returns to the heart via the superior and inferior vena cava into the right atrium.
It passes through the tricuspid valve into the right ventricle
It leaves the right ventricle via the pulmonary arteries and goes to the lungs for reoxygenation. Carbon dioxide is also exchanged via diffusion
Describe systemic circulation? (3)
The oxygenated blood leaves the lungs and enters the left atrium via the pulmonary vein
It passes through the bicuspid valve into the left ventricle
It is forced into the aorta via the semi lunar valves for deliverance around the body to the tissues
What is the sinoatrial node? (3)
It is a small mass of specialised called that lie in the walls of the right atrium near the opening of the superior vena cava generating regular impulses initiating contractions.
It is known as the pacemaker
Control depolarisation and repolarisation
What is the atrioventricular node? (3)
It is a mass of neuromuscular tissue that is situated in the wall of the atrial septum near the atrioventricular valves.
Imposes slight delay allowing atria to fully contract and empty of blood before the ventricles contract.
It then passes signal to Bundle of His
What is the Bundle of His? (4)
It is made of purkenji fibres
It is a conducting tissue running down septum
Branches travelling town septum to apex
Fibres spread up ventricle walls and causes contraction of ventricles from apex upwards to push blood up and out of the heart. The ventricles completely empty.
What is a key characteristic of specialised cells in the myocardium?
It is able to initiate contractions without the need for outside stimuli (nervous or hormonal)
What two circulating hormones does the heart respond to?
Adrenaline
Thyroxine
How many bpm can the atrioventricular node produce without the use of SA node?
40-60bpm at a slower rate
Where is the cardiovascular centre located?
Medulla oblongata
What does the cardiovascular centre do?
It controls the rate and force of cardiac contraction
What does the Cardiac Acceleratory Centre (CAC) do?
It stimulates the heart
- increases heart rate and contractility
What does the Cardiac Inhibitory Centre (CIC) do?
It inhibits the heart
- parasympathetic stimulus along the vagus nerve decreases the heart
What factors affect heart rate?
Gender Autonomic activity Age Hormones Exercise Temp Emotion
What is the sequence of the cardiac cycle?
Atrial systole
Ventricular systole
Compete cardiac diastole
What is atrial systole?
Contraction of the atria
What is ventricular systole?
Contraction of the ventricles
What is cardiac diastole?
Relaxation of the atria and ventricles
What is cardiac output?
It is the amount of blood ejected from each ventricle every minute
What is stroke volume?
The amount of blood ejected from each ventricle on every contraction
How do you worn out cardiac output?
Cardiac output = stroke volume x heartbeat
What is venous return?
It is the flow of blood back to the heart. Need steady-state conditions, venous return must equal cardiac output.
The force of contraction of the left ventricle is not sufficient to force the blood back to the heart. Other factors assist this: (4)
Position of the body
Muscular contraction
Respiratory pump
Suction of the heart
What is blood vessels made of?
Connective tissue and muscle
The inner layer of blood vessels are formed of endothelium
