Theme 3: Lecture 1 - Introduction to Circulation Flashcards
Perfusion
The flow of fluid through a tissue
What does flow require?
A pressure differnce
Hypotension
Low pressure - can lead to syncope or shock
Hypertension
High pressure - can lead to vessel damage, heart damage and many other pathologies
What are the functions of circulation?
- To carry oxygen, glucose and nutrients to the cells
- To remove waste such as carbon dioxide and heat
- Homeostasis of the extracellular fluid (via the kidneys)
- Distribution of hormones
- Temperature regulation
- Defence against infections
What are pressure and flow determined by?
The heart, blood volume and vessels
Blood pressure equation
Blood pressure = cardiac output (flow) x peripheral resistance
Peripheral resistance
The total resistance of all the blood vessels in the systemic circulation
Korotkoff sounds
What you listen for when taking blood pressure
sphygmomanometer
An instrument for measuring blood pressure, typically consisting of an inflatable rubber cuff which is applied to the arm and connected to a column of mercury next to a graduated scale, enabling the determination of systolic and diastolic blood pressure by increasing and gradually releasing the pressure in the cuff.
Functions of aorta
Stretch and recoil, stores energy
Function of arteries
Distribute, volume adjust
Function of arterioles
regulate caps, resistance, set BP and TPR
Function of capillaries
Exchange (nutrients, gas, fluid)
Function of venules
Collect blood, some exchange
Function of veins
Reservoir for blood, muscle pump
Structure of the right atrium
- Thin walled
- Crescent X-section
Structure of left atrium
- Thick walled
- Circular X-section
Features of pulmonary circulation
- Lungs only
- Low pressure
- High flow
- Low resistance
Features of systemic circulation
- Multiple organs
- High pressure
- Variable flow
- Variable resistance
Pulmonary artery blood pressure
24/12 mmHg
Right atrium blood pressure
4 mmHg
Right ventricle blood pressure
24/4 mmHg
Aorta blood pressure
130/70 mmHg
Left atrium blood pressure
7 mmHg
Left ventricle blood pressure
130/7 mmHg`
Systole
When ventricles contract. Blood is ejected
Diastole
When ventricles relax. Blood can fill ventricle
Apex beat
At systole, apex of heart moves forward and strikes the chest wall
Valves
Flaps of tissue inside a blood compartment that guarantee one way flow of blood
How many leaflets do heart valves have?
3, apart from the mitral (bicuspid) valve that has 2
Mitral valve
AKA the bicuspid valve, between the left atrium and ventricle
Chordae tendinae
Stringlike processes in the heart that attach the margins of the mitral and tricuspid valve leaflets to the papillary muscles
Papillary muscles
Projections of the wall of the ventricles that the chordae tendinae attach to
What is the route that blood flows through the heart?
Superior and inferior vena cava, Right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary arteries, lungs, pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta, systemic circulation
AV valves
- Are attached by papillary fibres (prolapse occurs when papillary fibres fail)
- Close during sytole
- Produce first heart sound
S1
First heart sound (lub)
Semilunar valves
- Moon shaped
- Close during diastole
- Diastole is longer than systole
- Produce second heart sound
S2
Second heart sound (dub)
Cardiac myocyte/cardiomyocyte
Heart muscle cell
What can a heart muscle cell be stimulated by?
- A neighbour
- A conducting system
Cardiac output
The amount of blood ejected by the heart in a minute
Formed elements
All the blood cells and platelets
Blood pressure is determined by the balance between
Circulating blood volume and circulatory capacity
Circulatory capacity
Total volume of all the blood vessels
Nephron
The structural and functional unit of the kidney
Glomerulus
Network of capillaries contained within Bowman’s capsule of the nephron. It is the primary filter
Bowman’s capsule
Cup shaped end of the nephron which encloses the glomerulus
Peritubular capillaries
Tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron
Vasa recta
One set of peritubular capillaries in the medulla of the kidney
What happens when the afferent arteriole constricts?
Filtration decreases
What happens when the afferent arteriole dilates and the efferent arteriole constricts?
Filtration increases
Filtration
Fluid leaving the glomerular capillaries and entering the tubule system of Bowman’s capsule
Reabsorption
Fluid that has been filtered that is then transported out of the tubule system and back into the bloodstream at the peritubular capillaries
Secretion (in the kidney)
The process where molecules (esp waste and drugs) are removed from the blood system at the peritubular capillaries and enter the tubule system of the nephron
Excretion (in the kidney)
Fluid that ends up inside the tubule system of the kidney and is ultimately transported to the urinary bladder for excretion
How many glomerulus are there per kidney?
Roughly 1 million
what are the inputs and outputs of the glomerulus?
Input:
-Afferent arteriole
Outputs:
- Into Bowman’s capsule
- Efferent arteriole
Glomerular filtration rate
- Measurement of how much filtering the kidney does from measuring the volume of entering all Bowman’s capsules in both kidneys
- Measured in ml/min
- An increased GFR leads to more fluid loss in urine
- Increased renal blood flow leads to increased GFR
Hypoxia
Insufficient oxygen supply to a region or the entire body
Anoxia
Complete deprivation of oxygen supply
Hypoxaemia
Too little oxygen in the arterial blood system
Causes of hypoxia, anoxia and hypoxaemia
- Low haemoglobin: anaemia
- Tissue consumption too much for the flow
- Lung: failure of gas exchange or of breathing
Ischaemia
Insufficient blood flow to a region
Causes of ischaemia
- Vessel: Clog, constriction, closure
- Insufficient blood volume: e.g. from haemorrhage
- Heart: Insufficient pressure generation
Haemorrhage
Escape of blood from a ruptured blood vessel, internally or externally
Angina pectoris
Chest pain due to over exertion of (damaged) heart tissue. It can occur with or without physical exertion
Treatment of angina pectoris
- Nitrates for immediate relief
- Long term treatments as per coronary artery disease
Causes of angina pectoris
- Immediate cause: Ischaemia of heart tissue due to an obstruction (or spasm) of coronary artery
- Ultimately may be caused by coronary artery disease or an embolism
Myocardial infarction
- AKA heart attack
- Death of one region of the heart
- Sudden crushing chest pain
- Results from occlusion of a coronary artery
Treatment for myocardial infarction
Immediate reperfusion e.g. PCI
PCI
Percutaneous coronary interventione.eg balloon angioplasty
Reperfusion
The re-establishment of blood supply to an area that has been ischaemic otherwise deprived of oxygen
Drug treatments for myocardial infarction (won’t cure but help the patient)
- Morphine: For pain
- Oxygen: For blood to remain oxygenated
- Nitrates: To open blood vessels
- Aspirin: Reduce the unwanted formation of clots and reduce platelet activity
Heart failure
- AKA pump failure
- Heart pumps out insufficient blood
- Results from previous myocardial infarctions
Symptoms of heart failure
- Fatigue
- Dyspnoea
- Oedema
Dyspnoea
Difficulty breathing
Oedema
Excessive accumulation of fluid in the body tissues
Shock
- Critically low perfusion
- Medical emergency
- Affects critically ill patients
- Affects cerebral and renal function
Haemorrhagic shock
Patient loses so much blood from vasculature that other regions of the body can’t get perfusion
Treatments for shock
Aggressive intravenous fluid and oxygen and airway maintained
Syncope
- Loss of consciousness (fainting)
- Due to insufficient blood flow to the brain
- Often caused by heart malfunction
Arrhythmia
Any deviation from the normal rhythm of the heart
