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
