Vascular Tree and Examination of Peripheral Pulses Flashcards
What is the role of the circulatory system?
-Contributes to homeostasis by delivery of nutrients and O2 via blood from one part of the body to another.
What do arteries/arterioles do?
-Carry oxygenated blood away from the heart and serve as a pressure resevoir.
What do venules/veins do?
-Highly distensible tubes that return oxygen depleted blood back to heart and lungs.
What so capillary beds do?
-Place of exchange of water, oxygen, nutrients and other substances between tissues and blood.
List the structures in the histology of the artery?
- Endothelium
- Tunica intima
- Internal elastic membrane
- Tunica media
- External elastic membrane
- Tunica externa
List the structures in the histology of the vein?
- Endothelium
- Tunica intima
- Tunica media (much larger in artery)
- Tunica externa
Describe the structure of the tunica intima media layer of arteries and veins?
- Single layer of flt epithelial cells with a separating layer of elastin rich collagen.
- Provides a smooth, friction reducing lining for the vessel.
Describe the structure and function of the tunica media layer of arteries and veins?
- Smooth muscle
- Activated by sympathetic NS, vasoconstriction and increase BP, or vasodilation and decrease BP.
-Connective tissue (primarily elastic fibres), elastic fibres stretch then passively recoil
Describe the tunica externa layer of arteries and veins?
- Outermost layer, made of fibrous connective tissue and vasa vasorum
- Protective and supporting layer
What can buegers test help show?
- An ischaemic leg would show difference in colour after elevation then lowering.
- Can let you see if it is heart pump that brings blood down or just gravity.
What is the vascular tree?
- Lots of branches of arteries and veins coming off a common trunk (aorta) which commences at left ventricle.
- The smallest branches can extend to peripheral parts of the body.
When/ how may a blood vessel divide?
- When aorta divides into common iliac arteries.
- A short vessel can subdivide into several branhces at the same point.
- A vessel may give off several branches in sucession and still continue as the main trunk (eg. arteries of the limb)
What are anastomoses and how may they form?
- Arteries communicating with one another form anastomoses
- They can be anatomical eg. Circle of Willis in brain
- Or can be functional eg. mesenteric vessels in GI tract
What results in collateral circulation?
-Expansion of vascular anastomoses results in collateral circulation.
Do smaller or larger branches anastomose more frequently and what can this result in?
Smaller branches
-Can result in extensive networks allwoing ongoing perfusion
In what clinical problems may collateral circulation be relevant and how?
- In chronic lower limb ischaemia collateralisation allows blood flow in non-textbook pathways
- In acute limb ischaemia where there is no collateral circulation, or occlusion of end arteries eg. splenic artery, reanl artery
Summarise the relationship between anastomoses and collateral circulation?
- An anastomoses is a union of vessels supplying blood to the same body tissue.
- Should a blood vessel become occluded, a vascular anastomoses provides collateral circulation (alternative route) for blood to reach a tissue.
What does the pulse represent and how may we feel our pulse?
- Represents palpable arterial palpatation after each heartbeat. Systolis contraction leads to this ressure wave we feel.
- Felt where an artery can be compressed against bone.
What do pulses allow us to assess?
- Rate
- Rythm
What are the pulses we can feel on our bodies?
- Popliteal
- Axillary
- Radial
- Brachial
- Carotid
- Ulnar
- Dorsalis pedis pulse
- Femoral pulse
- Posterior tibial pulse
How can the femoral pulse be located?
-Mid inguinal point: halfway between anterior superior iliac spine and pubic symphysis.
How can popliteal pulse be located?
-Above the knee in the popliteal fossa, found by holding the bent knee.
How can the dorsalis pedis pulse be located?
-Top of foot, immediately lateral to tendon of extensor hallicis longus
How can posterior tibial pulse be located?
- Medial side of ankle
- 2cm inferior and 2cm posterior to the medial malleous
How can the axillary pulse be located?
Located inferiorly to lateral wall of axilla
How can the brachial plexus be located?
Located on medial aspect of the arm near the elbow.
How can the radial pulse be located?
Lateral aspect of wrist and also anatomical snuff box.
How can the ulnar pulse be located?
-Located on medial aspect of wrist
How can carotid pulse be located?
-Medial to anterior border of sternocleidomastoid muscle, above the hyoid bone and lateral to the thyroid cartilage.
What can ankle brachial pressure values indicate?
- > 1 is normal
- 0.7-0.9 mild PAD
- 0.5-0.7 moderate PAD
- 0.3-0.5 severe PAD
- <0.3 limb threat
What is the caveat when it comes to measuring ankle brachial pressure values?
-Calcified vessels do not compress and can give falsely elevated readings.
What is atherosclerosis?
- Most common type of arterial disease characterised by calcification and plaque formation.
- Arterial wall thickening and elasticity loss
- Hardening of arteries
What are risk factors for atherosclerosis?
- Non modifiable: -increasing age
- sex (male)
- Family history
- Modifiable: -Diabetes
- Obesity
- Smoking
- Hypertension
- Hyperlipidaemia
- Pro thrombotic tendencies
What are the components of atherosclerotic plaque?
- Cellular (SMC, macrophages, WBC)
- ECM (collagen, elastin and prostaglandins)
- Lipid (cholesterol)
What is the major process of plaque formation in atherosclerosis?
- Intimal thickening (SMC proliferation and ECM synthesis)
- Lipid accumulation
How do vessels change in atherosclerosis and what are the potential consequences?
- Plaque narrows lumen: ischaemia, turbulence
- Weakening of wall: aneurysm, rupture
- Thrombosis: ischaemia, embolisation
- Plaque disruption: athero-embolisation
What is an embolism?
-Embolism is the blockage of blood vessel by solid, liquid or gas at a site distant from its origin.
90% are thrombo emboli
What does the internal carotid artery supply?
The brain and vertebral arteries
What is a common site of atherosclerosis and what consequences does this have?
- Common carotid bifurcation
- Causes luminal narrowing and potential embolisation of brain
What can cerebral ischaemia lead to?
-Can result in transient ischaemic attack or thromboembolic stroke
What is an aneurysm?
-An aneurysm is a bulge in a blood vessel caused by a weakness in the blood vessel wall, usually where it branches.
As blood passes through the weakened blood vessel, the BP causes a small area to bulge outwards like a baloon.
What are symptoms/signs of an aneurysm?
- Pain
- Low BP
- Rapid heart rate
- Light headedness
What can rupture of AA lead to?
-Life threatening internal bleeding
What can be done to reconstruct artery?
- Endovascular: baloon angioplasty, stent
- Open surgery: endarterectomy, bypass
- Open aneurysm repair
- Endovascular aneurysm repair
- Peripheral bypass
- Major limb amputation
What is the response to injury hypothesis for atherosclerosis?
- Presence of focal plaques within intima containing cholesterol and cholesterol ethers from young age.
- Chronic inflammatory response to vascual wall to endothelial injury or dysfnuction.
- Activation of endothelial cells
- Recruitment of monocytes/macrophages
- Formation of foam cells (fatty streaks)
- Proliferation of smooth muscle cells
- Deposition of ECM proteins
What size of artery tends to be affected by atherosclerosis?
-Large and medium sized
