Blood vessels Flashcards
What conditions can be present with diseases of the BV?
- Myocardial infarction
- TIA (transient ischaemic attack)
- Renal failure
- Stroke
- Blindness
- Aneurysm
- Headache
- Skin rash
- Syncope/ collapse
- Hypertension
- Claudication (pain on exercise)
- Peripheral arterial disease
- Ulcers
- Amputation
- Gangrene
How often does CVD death occur?
CVD is the leading cause of death with 1 death in every four minutes.
RBC to the organs passes what?
6 main types of BV, elastic arteries, muscular arteries, arterioles, capillaries venules and veins.
What are the anatomical layers of arteries and veins?
Adventitia (outermost) , media and intima (innermost)
What does vasoconstriction do and how does it occur?
Vasoconstriction decreases blood flow- smooth muscle contracts and makes the lumen narrower and increases BP
What does vasodilation do and how does it occur?
What does vasoconstriction do and how does it occur?
What is the endothelium made out of? Where is the endothelium found? What happens when it is damaged? What are the functions of the endothelium?
• Specialised squamous epithelium • Continuous throughout circulation- including chambers in heart- infection get endocarditis • Damage -> clot formation • Physiologically active – Blood pressure regulation – Regeneration & repair
What are the features of veins? What is their function?
Large diameter, low resistance
Veins have 3 layers- no elastic laminar and thin muscular wall
They return blood to heart organised into superficial (can see) and deep system (deeper)
Act as reservoir of blood- stretch and fill up with blood
Low P system and low resistance in there. Have valves to prevent back flow.
What are the 3 mechanisms to aid blood back to the heart?
- Skeletal muscle contraction system which helps compress the veins
- P of artery next to vein helps blood move in right direction
- Breathing in helps lower intrathoracic P and draw blood back into the heart
What is the general appearance of the artery, the tunica intimacy, media and external of the artery?
General appearances- Thick walls with small lumens
Generally appear rounded
Tunica intima- Endothelium usually appears wavy due to constriction of smooth muscle
Internal elastic membrane present in larger vessels
Tunica media-Normally the thickest layer in arteries
Smooth muscle cells and elastic fibres predominate (the proportions of these vary with distance from the heart)
External elastic membrane present in larger vessels
Tunica externa- Normally thinner than the tunica media in all but the largest arteries
Collagenous and elastic fibres
Nervi vasorum and vasa vasorum present
What is the general appearance of the veins, the tunica intimacy, media and external of the vein?
General appearance- Thin walls with large lumens
Generally appear flattened
Tunica intima- Endothelium appears smooth
Internal elastic membrane absent
Tunica media- Normally thinner than the tunica externa
Smooth muscle cells and collagenous fibres predominate
Nervi vasorum and vasa vasorum present
External elastic membrane absent
Tunica externa- Normally the thickest layer in veins
Collagenous and smooth fibres predominate
Some smooth muscle fibres
Nervi vasorum and vasa vasorum present
What are the types of capillaries?
- Continuous- Most tissues, BBB
- Fenestrated- Small intestine, kidney, endocrine organs- pituitary releasing thyroxine or GH
- Sinusoid- Liver, spleen, lymph nodes
Continuous- most common- forms basis of BBB and most vascularised tissues- water and ions can pass through-small molecules can pass intracellular cleft
Fenestrated- ‘windows’- for anything need to get in and out easily
Sinusoid- for specialised things- allow large molecules passage like plasma and proteins
What are the 3 types of flow?
- Frictionless flow- BV didn’t exert resistance at all on blood- doesn’t happen in BV
- Laminar flow- what we should have in BV- most efficient way of blood flow. Faster flow in the centre and all blood flowing in layers without mixing and touching each other
- Turbulent flow- mixing all of blood, different direction, noisy blood flood- can cause thrombosis
How does blood flow in the body?
- Movement of blood through a vessel, tissue or organ
- Volume of blood / unit of time
- Higher -> lower pressure
- Exerts pressure on vessels themselves (hydrostatic pressure)
- “Blood Pressure” = Systemic Arterial Blood Pressure
How to measure systemic arterial P?
When measure systemic arterial P ratio of two numbers- systolic P- higher- when blood ejected during ventricular contraction- diastolic ventricular relaxation- difference between two is pulse pressure- should be about 25% of systolic BP anything low is described as low or narrow such as heart problems/ when lost lot of blood.
Systolic blood pressure
The blood pressure when the heart is contracting
Diastolic blood pressure
Minimum arterial pressure during relaxation and dilatation of the ventricles of the heart when the ventricles fill with blood
Pulse pressure
Difference between systolic and diastolic blood pressure
Mean arterial pressure
The average pressure in a patient’s arteries during one cardiac cycle
Hypertension
Hypertension- blood pressure in the arteries is persistently elevated
Hypotension
Blood pressure in the arteries is persistently low
What 5 factors affect blood flow?
- Cardiac output
- Compliance
- Volume of the blood
- Viscosity of the blood
- Blood vessel length and diameter
- How much blood flows from heart to ventricles anything that increase HR or SV will increase P and blood flow- adrenaline, noradrenaline, calcium levels
- Ability for any compartment to expand or increase content- balloon very compliant- greater compliance of artery can expand more and accommodate blood flow- veins more complaint when vascular disease cusses stiffening or calcification- resistance increase, compliance decreases causing turbulent blood flow- happens over time with disease
- Low blood volume- from bleeding, vomiting, medication, burn - can lose lot of blood before showing symptoms
- Heart failure, liver cirrhosis, kidney disease, if patient on steroids
What is Poiseuille’s law?
The velocity of the steady flow of a fluid through a narrow tube (as a blood vessel or a catheter) varies directly as the pressure and the fourth power of the radius of the tube and inversely as the length of the tube and the coefficient of viscosity.
Flow (Q)= Pi x Change in P (pressure difference across tube) x R^4/ 8 x n (viscosity of liquid) x l (length of tube)
What BV gives the largest resistance?
Arterioles main component to resistance- however lots of capillaries in comparison to any type of BV- even though capillaries smallest lot more of them
Biggest change in P and steepest bit of curve when dealing with arterioles
How does coronary circulation work?
Coronary arteries come off route of aorta in two vessels- left main stem which becomes left anterior descending and left circumflex and supplies LA, LV and septum. Right pulmonary supplies RA, both ventricles and conducting system.
What are the phasic changes to coronary circulation?
There are phasic changes- when LV squeezes hard flow- blood flow can’t happen through those capillaries- blood flow in systole is low and in diastole is high- coronary fill in diastole
Intramyocardial P- when heart contracts spirals up in one direction for blood to go out of aorta- gradient of P in myocardium- highest P at top of heart, highest resistance at the bottom- more likely to get ischaemia at bottom of heart.
What is a sphincter?
A sphincter is a circular muscle that normally maintains constriction of a natural body passage.
How does auto regulation occur of the coronary circulation?
Open sphincter if oxygen drop carbon dioxide drop, increase lactic acid, becoming more acidotic- all encourage flood flow to error and if the opposite, blood flow is directed to other places
How does pulmonary circulation occur?
Pulmonary artery has deoxygenated blood
Pulmonary veins bring back to left side of heart
Receives full cardiac output
Operates at much lower P- arteries and arterioles lot less muscular
Local metabolic control- regulated by oxygen levels
What is the circle of Willis comprised of?
Anterior cerebral artery (left and right)
Anterior communicating artery
Internal carotid artery (left and right)
Posterior cerebral artery (left and right)
Posterior communicating artery (left and right)
What does the circle of Willis do?
Circle of Willis- is a circulatory anastomosis that supplies blood to the brain and surrounding structures. The middle cerebral artery is the artery most often blocked during a stroke.
What are the 3 components of auto regulation?
- Chemical- causes sphincters to open or close
- Myogenic response- where smooth muscle cells within arterioles respond to stretch and sense that- contract or relax
- Neurogenic component- direct connection between brainstem and sympathetic fibres of walls of arterioles if have a stroke or traumatic injury and those components are damaged more likely to have a worse outcome
What are age-related changes to arteries and veins
- Fibrous thickening of intima
- Fibrosis and scarring of media
- Accumulation of ground substance
- Fragmentation of elastic lamina
What is arteriosclerosis?
Arteriosclerosis- the thickening and hardening of the walls of the arteries
What is artherosclerosis?
Atherosclerosis- plaque builds up inside the arteries
What happens when you have arteriosclerosis?
Arteriosclerosis- where arteries are flamed or injured- become less compliant- BP and resistance increase- turbulent blood flow- inflammation spreads to the walls weakens and scars it making it sclerotic- triglycerides get trapped under arteries- WBC and leukocytes come under and form a plaque
What is a dissection?
Dissection when blood traps between layers of intima, media and adventitia
Blood should be flowing in true lumen, false lumen- blood traps and makes a false lumen which causes disease
What is an aneurysm?
Localised, permanent, abnormal dilatation of a blood vessel
Aneurysms can be true or false.
True- all three layers
False- blood within layers and bulges out to make an aneurysm
What is an abdominal aortic aneurysm?
AAA- localised dilation of aorta
An abdominal aortic aneurysm is an enlarged area in the lower part of the major vessel that supplies blood to the body (aorta). The aorta runs from your heart through the centre of your chest and abdomen.
What are the causes of aneurysm?
- Age
- Sex
- Family History
- Smoking
- Hypertension
- Hyperlipideamia
- Diabetes protective
What is thrombosis?
Clots in someone’s lungs
What is the difference between arterial and venous thrombosis?
Artery- white thrombus, contains lots of platelets and forms in fast flowing blood
Veins- red thrombus, contains lots of RBC and forms in slow flowing blood
Thrombosis occurs when in arteries and veins?
- Arteries happens after atherosclerotic plaque
- Venous- from triads tract
What is hypertension?
- Accelerates atherosclerosis
- Potentiates dissection, aneurysm formation and cerebrovascular haemorrhage
- Histological changes
- Fibrinoid necrosis- pink substance
- Hyaline arteriolosclerosis
- Hyperplastic Arteriolosclerosis (“onion skinning”)
What is vasculitis? What is an example of this?
Vasculitis- inflammation of BV
Giant Cell Arteritis- most common form of vasculitis that occurs in adults
What is vasculitis? Example of this?
Vasculitis- inflammation of BV
Giant Cell Arteritis- most common form of vasculitis that occurs in adults
