Arteries, Veins and Peripheral Resistance Flashcards
What are the parts of the circulatory system?
arteries, arterioles, capillaries, venules, veins.
What is after load?
it is the force the heart must overcome to push blood into the arteries
What is pulse pressure?
the force the heart generates with each contraction to overcome arterial pressure
What are the equations of mean arterial pressure (MAP)?
MAP = DBP + 1/3 pulse pressure
MAP = CO x TPR
What are the factors that influence pulse pressure?
stroke volume
compliance of arteries
ejection velocity
What connective tissue is present is arteries?
elastic
What muscle is present in arteries and what layer is it mostly located?
smooth muscle
tunica media
What are the major areas of the aorta?
ascending
arch
descending thoracic
descending abdominal
What is the size of small arteries?
<2mm
What do capillaries form?
large networks
How thick are capillaries?
1 cell thick for optimal exchange
What do capillary walls lack?
tunica media, tunica adventitia
What is the difference between veins and arteries?
veins have larger diameter and lumen
thinner walls
lower pressure
valves to prevent back flow
What prevents backwards flow of blood in veins?
valves
What type of muscle do blood vessels contain?
smooth
How much blood do veins contain at low pressure?
70%
What can cause varicose veins (distended -swollen or large)?
weakened vein walls or valves
What do weakened vein walls or valves cause?
turbulent blood flow
What are the 3 wall layers all vessels share except capillaries?
tunica intima
tunica media
tunica adventitia
What do endothelial cells form?
the inner lining of vessels (tunica intima)
What do endothelial cells play an important role in?
local BP
provide friction free surface for blood
regulate permeability of vessels
regulation of platelet function and fibrinolysis
promote vessel formation (angiogenesis)
What is the structure of the tunica intima?
single line of endothelial cells attached to basement membrane
underlaying layer of extracellular matrix
then internal elastic lamina
What is the structure of the tunica media?
layers of elastic fibres and smooth muscle cells (proportion depends on artery type-muscular or elastic)
enables vessel contraction and relaxation
What is the structure of the tunica adventitia?
external elastic lamina (separates media)
thick connective tissue (collagen +elastin)
nerve fibres, lymphatics
in larger arteries vasa vasorum
What are vasa vasorum?
small arterioles that perfuse the media (vessels of vessels)
What is vascular compliance?
ability of a blood vessel to expand and recoil as a response to changes in pressure
What is the equation of compliance?
changes in volume / changes in pressure
What is an example of arterial compliance?
arterial wall will expand to accommodate ventricular stoke volume
What is arteriosclerosis?
a chronic condition in which arteries harden and narrow through build-up of plaques. (plaque contains lipids, fibrous)
What can decreased compliance increase?
pulse pressure
What is local control of BP?
alteration of small artery and arterioles resistance
What are hormones that cause local control of BP?
adrenaline
atrial natriuretic peptide (ANP)
angiotensin
Where is adrenaline released from and where does it bind to most?
adrenal medulla and beta 2 receptors
How does ANP cause vasodilation?
increasing sodium ion excretion by the kidneys
increasing water loss by urine
therefore reduced blood volume
Describe the Renin-Anginotensin-Aldosterone-System (RAAS)
1-reduced blood flow to kidney is detected by receptors in juxta-golmerular granular cells causing release of renin
2-renin acts on circulating angioteninogen produced by liver to convert it to anginotensin 1
3- ACE enzyme converts angiotensin 1 to angiotensin 2 which is a potent vasoconstrictor
4 -angiotensin 2 promotes release of aldosterone from the adrenal cortex
5 -aldosterone stimulates Na+ and water reabsorption in distal convoluted tubule which increases blood volume
What are examples of ace inhibiting drugs?
captopril
enalapril
What is an example of a angiotensin 2 receptor blocker?
losartan
What vasodilators do endothelial cells release?
Nitric Oxide (NO)
Prostaglandin I2 (prostacyclin)
What hormone does angiotensin 2 promote release of?
antidiuretic hormone which causes vasoconstriction in V1 SMC
What vasoconstrictors do endothelial cells release?
Endothelin 1 (ET-1)
Thromboxane A2)
What is shear stress?
the force of blood flowing on endothelial layer
What can shear stress cause?
release of vasodilators from endothelial cells
How does shear stress occur?
blood travelling at different velocities in a blood vessels
What can alterations in homeostatic conditions (physiologic or pathologic) cause?
adaptation or disease of blood vessel
What are metarterioles?
terminal arterioles that don’t have a layer of smooth muscle, but instead smooth muscle fibres surrounding the vessels intermittently
What is the branch site of the met arterioles surrounded by?
pre-capillary sphincters that contract and relax in response to metabolic factors
What pressure forces fluid from intercellular space to interstitial space?
hydrostatic
What pressure forces fluid from interstitial space to intercellular space?
osmotic
What is colloid pressure dependant on?
movement of proteins
What does negative net filtration mean?
net fluid absorption from interstitial space to capillaries
What can build up of fluid in tissues lead up to?
oedema
What flows through the lymphatic system?
lymph
Can lymph vessels contract?
yes
What is the lymphatic system made from?
lymph nodes, and lymph vessels
What does the lymphatic system do to excess fluid?
return it to circulation
What does the lymphatic system play a central role in controlling?
concentration of proteins in interstitial fluid
volume of interstitial fluid
interstitial fluid pressure
What are pulmonary hydrostatic pressures lower than?
systemic hydrostatic pressure
What pressure is equivalent in both systemic and pulmonary?
colloid
What can pulmonary oedema be caused by?
heart failure
high altitudes
lung damage
adult respiratory distress syndrome
Which hormone is produced in the hypothalamus?
ADH
What is responsible for moving absorbed fat?
lymphatic system
