Blood vessels and Lymphatics Flashcards
What is the histology of blood vessels ?
3 layers: Tunica intima (endothelium + CT) Tunica media (muscle + CT) Tunia adventita (thick CT)
What is the histology of the Tunica intima ?
- Specialised simple squamous = endolthelium
- Deep to endothelium, BM which binds it to CT
- Possible internal elastic membrane at boundary with tunica media in larger arteries
What are the secretions of the endothelium ?
Endothelins, constrict smooth muscle within walls of vessels to increase BP
What is the histology of the Tunica Media ?
- Concentric layers of helically arranged smooth muscle cells with elastic fibres
- Possible external elastic membrane at boundary with tunica adventitia in larger arteries.
Which is the thickest layer in arteries ? Why ?
Tunica media (much thicker in arteries than in veins). Because they need to push blood against P gradient. (May be tunica adventitia in some arteries.)
How do vasoconstriction and vasodilation take place ?
Vasoconstriction: contraction of circular muscle, reducing diameter of the lumen, decreasing blood flow and increase blood P
Vasodilation: relaxation of circular muscle etc.
What is the histology of the Tunica Adventitia ?
-Longitudinally oriented CT made of type 1 collagen fibres
What is the thickest layer in veins ?
Usually tunica adventitia
What is the normal path for blood flow ?
Large Elastic arteries - Medium Muscular arteries - Arterioles - Capillaries - Venules - Medium Veins - Large Veins - Heart
Why are elastic arteries elastic ? What is the role of elastic arteries ? How do they behave during systole and diastole ?
Because of elastic fibres in the tunica media.
Conducting.
They expand during systole
They recoil during diastole to help drive blood onwards
Why are muscular arteries muscular ?
What is their role ?
Due to thick layer of circular smooth muscle in tunica media.
They:
1. control distribution of blood to regions and organs
2. regulate blood flow by constriction and relaxation of walls
What happens to muscular arteries when there is an occlusion of an artery ? If there is a haemorrhage ?
They can accommodate a change in diameter: The diameter of collateral muscular arteries increases to carry blood to ischaemic area. They contract (diameter decreases) to prevent blood loss.
What are the main arteries of the upper part of the body ?
Arotic arch, left subclavian, brachiocephalic artery, right subclavian, right vertebral, left vertebral, right common carotid, left common carotid, right internal carotid, left internal carotid.
What are the main arteries of the upper limbs?
Subclavian, Axillary, Brachial, Ulnar, Radial
What is the first branch of the aorta ?
Coronary Arteries
What is arterial anaestemosis ?
Where in the body is it useful ?
Communication between blood vessels
Around joints and in the hand and fingers (ensures supply of blood in any position of the upper limb, even if flexing)
What are the anaestemoses of the hand called ?
Deep and superficial palmar arch (between radial and ulnar arteries)
What are the large arteries of the trunk ?
Aorta divided into ascending, descending aorta, and aortic arch.
- Descending aorta yields thoracic and abdominal aorta
- Abdominal aorta then divides into R and L common iliac arteries (deliver blood to lower limbs)
What are the lower limb arteries ?
Common iliac arteries divides into internal and external.
-Once the external iliac artery passes ligament in the thigh, becomes femoral artery (accompanied by femoral vein medially and femoral nerve laterally)
Why is the femoral artery clinically relevant ?
Because you might get arterial blood from it (although difficult because may injure femoral nerve)
What are arterioles ? Metarterioles ?
Arteries with less than 0.5 mm in diameter.
Arteries with same diameter as capillary but one layer of smooth muscle cells in walls to still distribute blood.
What is the histology of capillaries ?
Endothelial cells supporting on BM
NO smooth muscle cells
Pericytes enclosed in BM splits (contain myosin, actin and tropomyosin)