Arterial pattern and venous drainage of the body Flashcards
Describe the vascular system
The vascular system transports blood around the body.
It includes the arteries that take blood away from the heart
The veins that bring blood back to the heart
The blood carries the oxygen, nutrients and waste products to and from the cells
Describe blood vessels
Blood vessels have different structural and functional characteristics depending on their function.
Those that supply oxygenated blood
Arteries
Arterioles
Capillaries
Those that drain deoxygenated blood
Venules
Veins
Describe the microstructure of blood vessels
Blood vessels have a common structure
Tunica intima – mainly endothelium
Tunica media – muscular (great variation)
Tunica adventitia – CT coat
Describe the endothelium
The endothelium is a specialised part of the tunica intima, it is made from squamous epithelial cells
Endothelial cells are bound together by junctional complexes
Endothelial cells secrete clotting factors and factors which maintain the tone of vascular smooth muscle
Describe arteries
Carry blood under high pressure away from the heart
Arteries have a decreasing luminal diameter
Arteries are classified according to the contents of the tunica media into:
Elastic
Muscular
Describe elastic arteries
Elastic arteries are the major conducting vessels e.g. aorta and common carotid
Tunica media is broad and has a high amount of elastin sheets
Function- accommodates surges in blood
Continues to push the blood downstream to medium arteries
Describe muscular arteries
Muscular arteries are the main distributing branches
Tunica media comprised predominantly of smooth muscle
They can control blood flow by constricting (vasoconstrict)
Have pulsatile contractions of their muscular walls to aid propelling the blood
Most named arteries in the body e.g. axillary, brachial, radial.
Lead into small arteries and arterioles.
Describe arterioles
Arterioles are microscopic - ≤0.3 mm Ø :
intima – thin (endothelium & elastic lamina)
media – smooth muscle
adventitia – CT merges
distribute blood to capillaries – regulate flow to capillary bed (affects blood pressure)
Describe capillaries
Capillaries may be of two types: Continuous - uninterupted lining - common: e.g. skin, smooth muscle, lungs Fenestrated - numerous pores ↑ exchange - e.g. renal glomeruli, endocrine glands Function: transfer of : oxygen / carbon dioxide, nutrients, hormones, immunologically competent cells, phagocytic cells
Describe venules
Venules are the smallest veins, they drain capillary beds
Post capillary venules
- union of several capillaries
- some metabolite exchange
Collecting venules
- progressive ↑ Ø , ↑ muscle
- passive collecting system
- no elastin
Describe veins
Veins are returning low oxygen blood to the heart
Because of low pressure the walls of the tunica media are thinner
Medium veins drain venous plexus e.g. cephalic vein
Large veins have a well developed tunica adventitia e.g. vena cava
Where veins have to work against gravity e.g. limbs valves are common
Describe the circulatory system
Heart has two pumps that act in series dividing the circulatory system into two:
Pulmonary system
Right ventricle-propels low oxygen blood into the lungs via pulmonary arteries
Systemic system
Left ventricle-propels high oxygen blood into aorta
Describe the portal system
Venous blood that is high in products of digestion needs to filtered
Veins from the: spleen, stomach, intestines drain into the liver via the hepatic portal vein
Filtered by the liver and blood drains into the hepatic veins and into Inferior Vena Cava to be returned to the heart.
Describe the association between arteries and veins
Vessels run in close relations- often in neurovascular bundles protected by connective tissue
Pairs of veins surrounding artery - venae comitantes (functional)
Describe anastomoses
uniting of arteries e.g. vertebral arteries
Creates un-interrupted circulation
Especially in limbs around joints
Clinically in either an accident, ligation, disease an anatomoses provides collateral circulation
