The Circulatory System Flashcards
Describe the histology of Tunica external and what it contains
CT w loose weave of collagen/elastic fibres
Thicker when found in veins
Contains
Nervi vasorum, lymphatics and vasa vasorum (only in larger vessels)
Describe the histology of Tunica media and the significance of this.
Smooth muscle and loose CT
Smooth muscle = maintains patency and controls vessel diameter =stabilises and influences BP
Describe the histology of Tunica intima and what it contains
CT w elastin
Inner endothelium = friction free surface for easy blood flow
What are anastomoses?
connection between 2 peripheral vessels, without an intervening capillary bed
What are the three main parts of Blood vessel anatomy?
Tunica Externa
Tunica Media
Tunica Intima
What is Vascular Tone?
degree of constriction experienced by a blood vessel
What are the three factors that regulate vascular tone?
Membrane potential of smooth muscle
Chemical ligands
Mechanical stimuli/ myogenic mechanism
How does the Membrane potential of smooth muscle regulate vascular tone?
Hyperpolarisation = relaxation
Depolarisation = contraction
Explain the chemical ligand control of vascular tone
A-adrenoreceptors on arterioles in skin and salivary glands = vasoconstriction
B-adrenoreceptors of coronary and muscle arterioles = vasodilation
What are the two mechanisms of mechanical stimuli/myogenic mechanism regulation of vascular tone?
Stretch-induced contraction
pressure induced contraction
Where does the following occur:
a) Stretch-induced contraction
b) Pressure-induced contraction
a) arteries and large arterioles
b) terminal resistance arterioles
What is the consequence of a sympathetic surge in arteries?
Noradrenaline released from a1-adrenergic receptors on smooth muscle = vasocontriction
B-Adrenergic receptors cause vasodilation to ensure cardiac tissue not compromised
What is the consequence of Loss of nervous input
vasodilation
Do arteries carry Oxy or Deoxy blood in
a) systemic circulation
b) pulmonary circulation ?
a) oxy
b) deoxy
What are the three main anatomical features of arteries?
External elastic membrane/lamina
Internal elastic membrane/ lamina
circumferential Smooth Muscle
What is External elastic membrane/lamina and where is it found?
Band of elastic CT at outer surface of tunica media
What is Internal elastic membrane/lamina and where is it found?
Band of elastic fibres at the outer surface of tunica intimia
What are the two types of arteries?
Elastic/conducting
Muscular/distributing
What are the structural features of Elastic/conducting arteries and what is the significance of them?
LARGEST
Most proximal to heart (resilient)
Thick walls and wide lumen (laminar blood flow)
High density elastin in tunica media (withstand pressure from ejection and dampen oscillation)
Few smooth muscle fibres (oppose stretch, maintain paten
What are the structural features of muscular/directing arteries?
Distal to elastic
Thickest tunica media
Limited vasoactivity
features and function of arterioles
Features
Distal to both types of arteries
Larger ones = poorly defined arteries
No tunica advenitia in terminal/resistance arterioles
Function
Vasoactive (strong influnce on blood flow)
What is the effect of injury for elastic arteries?
Loss of elastin
Aneurysm
What is the effect of injury for muscular arteries?
Aneurysms
More tendency to develop atherosclertoic plaque
Thick tunica media = protects against crushing
How does smoking/ nicotine damage arteries?
causes loss of elastin by stimulating the release of elastase
Why not take carotid pulse in an elderly patient?
elastin is lost with age so the artery may not rebound after compression OR dislodge a plaque.
True vs false aneurysm
True = all three walls affected
False = 1-2 walls affected
How is blood moved in elastic vs muscular arteries?
E= elastic recoil
M= pressure difference using force from V ejection and previous elastic recoill
Systolic pressure in exercise
SNS stimulates inceased CO = more blood into arteries = large INCREASE in S.
Describe what determines Diastole pressure and how it is impacted in Exercise
Rate of blood moving out determined by pressure drops between beats
this is determined by Peripheral Vascular Res.
Therefore PVR = major determinat of D
D doesn’t really change in exercise
do veins carry blood towards heart that is oxy or deox in
a) systemic
b) pulmonary
a deoxy
b oxy
Anatomical features of Veins
Valves
Large ones may have 1-2 layers of smooth muscle
Why is skeletal muscle activity important for venous blood flow?
Muscle pumping promotes venous return
What is a Vascular Venous Pump
Venae comitantes = artery coupled with a pair of veins wrapped in CT
What is the purpose of the Vascular venous pump?
When arterial pulse flows through artery, the artery expands = compresses vein = pushes blood towards the hearts
what 2 resp pumps aid in Venous return and how?
Thoracic V pump and Abdomino-throacic pump
Aids in V retrun via Negative pressure allowing the chest to suck blood up
What are the three types of capillaries?
Continuous
Fenestrated
Sinsusoid
Structural features of continuous capillaries
uninterrupted endothelium
partially or completely impermeable
within most tissue
Structural features of Fenestarted capillaries
fenestrated endothelium - pores between cells allow easier fluid/ protein movement
Structural features and location of Sinsusoid Capillaries
Very leaky - intercellular gaps allow larger molecules to pass
usually also fenestrated
may have large and irregular lumens
within the liver, bone marrow, lymphoid tissues, and some endocrine organs
How is systemic capillary bed exchange controlled?
- substance movement under greater (continuous) or lesser (sinusoid) control
- substances move according to concentration gradients
- fluid movement governed by pressure and osmotic/ oncotic gradients
What is the formula for NFP?
NFP = Net Hydrodtatic pressure - net colloid osmotic pressure
NFP= (Pc-Pif) - (IIp - IIif)
What is the jugular a peak?
right atrium systole
What is the jugular AV dip.
right atrium diastole
what is the jugular C peak?
early R ventricular systole
Pressure rise causes tricupsid valve bulging
What is the jugular X-dip?
ventrical sytole
heart shortens = pulls and elongates veins
what is the jugular V peak?
RA filling when tricupsid closes
what is the jugular y-dip?
blood speeds out of jugular during rapid ventricular filling
What occurs at the dicrotic notch?
small increase in aortic pressure caused by the brief backward flow of blood as the aortic valve snaps shut
What is the consequence of MI on the Ventricular Pressure curve?
less contractibility = decreased peak Systole pressure
increased diastole pressure –> stiff and less compliant = can’t relax enough
= less step rise and fall
What is the impact of increasing SNS on ventricular pressure curve?
increased ionotrophy = increased peak systolic pressure curve
increased chronotrophy = shortened duration of systole and diastole
increased lusitropy = diastole curve falls fast
What are the chemoreceptors and where are they located?
what: regulate resp activity and cardiovascular function
where: carotid and aortic bodies
