Week 2 - The cardiovascular system Flashcards
1
Q
What is the cardiovascular system commonly referred to as and what does it do?
A
- Commonly referred to as the fluid transport system
- Delivers substances to the tissues of the body while removing waste products of metabolism
- Ensures that each cell is replenished with nutrients, water and oxygen
- Transports substances, such as hormones, from their site of production to their target organs
2
Q
Where is the heart positioned in the body?
How many chambers does the heart have?
A
- To the left of the thoracic cavity between the lungs
- The heart has four chambers
3
Q
What are the similarities and differences between cardiac muscle and skeletal muscle?
A
- The heart has it’s own conduction system in contrast to skeletal muscle which needs nervous stimuli
- Composed of specialised cardiac muscle cells which have their own electrical conductance abilities similar to nerves
4
Q
What are the different layers of the heart?
A
- Outer pericardium - thick membrane sack that surrounds the heart and protects and lubricates the heart by reducing friction
- Visceral pericardium / epicardium - the inner layer of pericardium, consists of connective tissue
- Myocardium - thick and composed of specialsed cardiac muscle cells that have electrical conductance abilitities
- Coronary arteries supply the myocardium
- Endocardium - thin layer of smooth muscle consisting of epithelium and connective tissue + elastic & collagenous fibres
- Inner layer of the heart wall
- Purkinje fibres are specialised cardiac muscle fibres foudn here
5
Q
Describe the chambers of the heart and what they are divided by
A
- Four chambers in the heart (2 left & 2 right)
- Upper chambers are the atria divided by interatrial septum (a wall-like structure)
- Lower chambers are the ventricles divided by interventricular septum
6
Q
How is the heart able to act like a pump?
A
- Two sides of the heart function as two seperate pumps & pump blood through seperate circulations
- Right side pumps deoxygenated blood in the pulmonary system
- Left side pumps oxygenated blood in the systemic circulation
- Since the right and left ventricle & atrium is seperated from the right, oxygenated and deoxygenated blood doesn’t mix
7
Q
What are the atria referred to as?
Where do they recieve blood from?
A
- Referred to as receiving chambers because the recieve blood returning to the heart (have smaller and thinner walls than ventricles)
- Right atrium receives deoxygenated blood from the superious vena cava and the inferior vena cava
- Superiour vena cava carries blood from head, neck, chest & arms
- Inferior vena cava carries blood from trunk & legs
- Left atrium receives oxygenated blood from the left &right pulmonary veins
8
Q
What are the ventricles referred to as and where to the pump blood to?
A
- Referred to as discharding chambers as they receive blood from the atria and pump out into the pulmonary artery and aorta
9
Q
Describe the flow of blood through the heart
A
- Blood from the superious / inferior vena cava enter the right atrium
- Right atria contracts and and blood flows across the tricuspid valve into the right ventricle
- Right ventricle contacts, tricuspid valve closes and blood flows across the semilunar valve into the pulmonary artery
- Pulmonary artery splits into two vessles & enters the capillaries of the alveoli in the lungs
- Blood returns to left atrium through the 4 pulmonary veins
- Left atrium contracts and blood goes across the bicuspid (mitral) valves into the left ventricle
- Left ventricle contracts, mitral valve closes forcing blood into the aorta across the semilunar valve
10
Q
How many atrioventricular valves are there?
What is the function of the atrioventricular valves?
A
- There are two atrioventricular valves (AV) seperating the atria from the ventricles
- They are one way valves to ensure that blood only flows in one direction from the atria to the ventricles
11
Q
What are the left / right AV valves known as and what is their structure?
A
- Right AV valve is known as the tricuspid valve because it has three flaps and is located between the right atrium and the right ventricle
- Left AV valve is called the bicuspid (mitral) valve as it has two flaps and separates the left atrium from the left ventricle
12
Q
How & where are the AV valves attached?
A
- The AV valves are attached to the walls of the ventricles by string-like structures known as chordae tendinae
13
Q
What are the valves positioned between the ventricles and the arteries known as?
A
- The semilunar valves are positioned between the centricels and large arteries (pulmonary atery and aorta) that carry blood away from the heart
14
Q
What happens to the deoxygenated blood pumped from the heart?
A
- Blood leaves the right side of the heart and enters the pulmonary trunk
- From the pulmonary trunk to the pulmonary artery
- Enters the capillaries of the alveoli of the lungs where gas exchange occurs
15
Q
What happens to blood from the left side of the heart?
A
- Blood is pumped across the aortic semilunar valve into the ascending aorta
- Aorta branches into ateries carrying oxygenated blood to all parts of the body
- First 2 aortic branches are the coronary arteries (supply oxygen. blood to the capillaries of the myocardium)
16
Q
Structurally, what is the difference between the left and right side of the heart?
A
- Left ventricular musclar wall is very thick since it needs to force blood to all body parts meaning a high resistance to blood flow
- Right ventricular muscular wall is thinner as it only pumps blood to the lungs with a lower resistance to blood flow
17
Q
How are the four chambers of the heart coordinated?
A
- Atria contract first (atrial systole) whilst the ventricles contract (ventricular diastole)
- Once ventricles are filled with blood the ventricles contract (ventricular systole) and the atria relax (atrial diastole)
- A brief period of relaxation for both the atria and the ventricles occurs
- The above series of events make up the cardiac cycle
18
Q
What is the distinctive sound of the cardiac cycle called and why does the sound arise?
A
- Distinctive double thumping sound (lub dup) when heard through a stethoscope
- Lub is caused by the vibration and sudden closure of the AV valves during ventricular systole
- Dup is caused by the closure of the SL valves during ventricular diastole
19
Q
What are the two pacemakers of the heart?
How are they regulated?
A
- The sinoatrial node and the atrioventricalar node are the two cardiac pacemakers causing the heart to beat
- They can be regulated by the automonic nervous system and circulating adrenalin
20
Q
Describe the structure and function of the SA node
A
- SA node is a small mass of specialised cells located beneath the epicardium of the right atrium
- SA node is impulse generating tissue which initiates impulses throughout the myocardium, stimulating the contraction of cardiac muscle fibres
- Referred to as the pacemaker as it generates the hearts rhythmic contractions
21
Q
Describe the path of the cardiac impulse
A
- Cardiac impulse starts as the SA node
- Travels into the atrial syncytium which causes the atria to contract
- Impulse travels along junctional fibres to the AV node
- Due to the smaller diamter of the junctional fibres, the impulses are slightly delayed
- Once impulse reaches AV node it passes into the bundle of His and Purkinje fibres to the ventricles causing them to contract
22
Q
What is the significance of the smaller diameter of the junction fibres before the AV node?
A
- The impulses are slightly delayed
- Allows the atria more time to contract and pass their blood to the ventricles before ventricular contraction occurs
- Under normal circumstances ventricular beat follows each atrial beat
23
Q
What is and electrocardiogram and what does it represent?
A
- An electrocardiogram (E. C. G.) is the graphic record that represents the electrophysiology of the heart
24
Q
What can an E. C. G. show?
A
- ECG can show the heart’s rate and rhythm and it can also detect abnormalities such as enlargement of the heart
25
Q
How many distinct waves does and ECG have and what are they?
A
- P-wave - indicates that the atria are depolarised (electrically stimulated), which triggers atrial contraction that causes the blood to be pumped into the ventricles
- QRS complex - indicates that the ventricles are depolarised
- T-wave - indicates repolarisation (recovery period) of the ventricles
28
Q
Describe the different layers of arteries
A
- The arteries walls consist of three layers:
-
Tunica interna - is the inside layer made of squamous epithelial cells called the endothelium
- Endothelium regulates blood flow and helps prevent the blood clotting
- Tunica media - is the middle layer consisting of smooth muscle fibes and a thick elastic connective tissue layer - this layer contribues most of the arterial cell wall
- Tunica externa - thinner, made of connective tissue fibres, aka tunica adventitia )
32
Q
Outline capillaries
A
- They are the smallest vessel and connect the smallest arterioles to the smallest venules
- Extremely prevalent in the body and interact closesly with tissues
35
Q
What is the permeability of capillaries decided by?
A
- The walls of capillaries contain thin slits where endothelial cells overlap
- Slits have various sizes which affects the permeability
- E.g. plasma proteins cannot normally move across capillary walls due to their large size, therefore they remain in the blood
38
Q
Describe the structure of vein walls
A
- Veins walls are similar to arteries but they lack the smooth muscle in the endothelium and less connective tissue in the tunica externa
- Have thinner walls that are less elastic than arteries and their lumens have a greater diamter
44
Q
Outline pulmonary circulation
A
- In the pulmonary circuit, deoxygenated blood is pumped from the right ventricle of the heart to the lungs via the pulmonary arteries
- In the lung gas exchange occurs thus ensuring oxygenated blood returns to the heart to the left atrium via the pulmonary vein
45
Q
Outline systemic circulation
A
- Systemic circulation refers to oxygenated blood pumped from the left ventricle into the aorta
- Supplies oxygenated blood to the organ system
- Systemic arteries arise from the capillaries and direct blood into the capillaries
- Cells consume oxygen and nutrients and add waste products (e.g. CO2), enzymes and hormones
- Veins drain deoxygenated blood from the capillaries and return it to the right atrium via the vena cava
46
Q
Outline hepatic portal circulation
A
- Refers to the flow of blood through the liver
- Veins from: gallbladder, spleen, stomach, intestines and pancrease do not empty directly into the inferior vena cava but instead into the liver via the hepatic portal vein
- The deoxygenated blood is cleaned by the liver and then enters the inferior vena cava
- None of the hepatic veins have valves
47
Q
Outline fetal circulation
A
- This differs from the circulation after birth since the fetus receives oxygen and nutrients from maternal blood not their own organs
- The development of human fetus depends on gas, water, nutrient and waste exchange in the fetal and maternal portions of the placenta
- Human fetal placenta has two small umbillical arteries which drain into a single umbillical vein
- Umbillical vein carries oxygen and nutrients from the mother to fetal cardiovascular system
- Umbillical arteries carry blood containing waste products from the fetus to the mothers blood
-
Placental villus is the key anatomical structure for fetal/maternal exchange
- Completely surrounded by maternal blood, site for nutrient and waste exchange
- Outermost layer of PV is the syncytiotrophoblast and the underyling layer is cytotrophoblast
- The vasculature of the placenta adapts to the size of the fetus as well as to the oxygen available in the maternal blood.
58
Q
Describe the stages of atherosclerosis
A
- Fibrous fatty intimal plaques (atheromas) in the arterial walls
- Atheromas lead to the narrowing of blood vessels and consequently a decline in blood flow
- Initiated by accumulation of low-density lipoproteins (LDL) within the endothelium of the blood vessel wall, here they come entangled by interactions with proteoglycans
- In endothelium LDL phospholipid and other proteins undergo oxidation which progresses to an inflammatory response
- Inflammatory response stimulates endothelial cells and smooth muscle cells to release chemokines (signal molecules) that attract macrophages to the site
- Architecture of the vessel wall is reorganised are a result of damaged endothelial cells, smooth muscle cells and macrophages which promote cell division and migration
- Formation of a fibrous cap that seals the damaged area of the blood vessel
- Eventually inflammation weakens the fibrous cap causing it to rupture
- Blood clot forms & blocks blood flow, especially in smaller vessels such as coronary artery
- Decreased blood flow through coronary arteries can cause pain and tightness in the chest (angina pectoris) which conseuqently prevents oxygen from reaching myocardial cells
