Unit 4a - Circulation Basics Flashcards
Functions of the Circulatory system (5)
-diffusion, convection, transportation, transportation of heat, production of heat
3 basic components of the cir sys.
- circulatory fluid 2. pump 3. Vascular system
Characteristics of an open system
- incomplete system of vessels - most invertebrates -low blood flow and BP -slow return of blood to the heart
Characteristics of a closed system
- enclosded system of vessels -vertebrates, some inverts -higher blood flow and BP -blood/tissue exchange across capillary walls
Advantages of a closed system
- control velocity and distribution of blood -increase in metabolic rate and body mass -enable evolution of glomerula kidney
Undivided vs. divided blood (pros of divided)
- undivided= no separation -divided= complete or partial separation pros of divided= increased BP to body, increased metablolic rate and body mass
Evolutionary trend to become O2 breathers
- increase in o2 uptake -increased size- energy goes up - need separation of blood as well as an effecient blood transportation system -increase in BP and flow
3 types of vessels
arteries, veins and capillaries
what is the structure of the vessels
- all have an endothelial lining -arteries and veins have connective tissue (elastic and collagenous fibres) and smooth muscles
how does cross-sectional area affect velocity
-small cross section-= highest velocity = arteries, aorta
how does the large area of the capillaries influence the ability and speed of O2 delivery
- large area, velocity is low- spends a lot of time going through, allows lots of diffusion to occur
Tunica media and tuica adrentitia
tunica media- muscle layer around the endothelium tunica adrentitia= outer fibrous layer
How does the tunica media differ between large and medium arteries
large= elastic (needs to expand) medium= muscular
Compliance
-the elasticity of the aorta walls allows for dampening of the oscillation of the heart to allow for continuous blood flow
Arteries- Characteristics
- large= low resistance, low pressure drop -pressure is determined by the volume of blood and the wall properties - in charge of maintaining blood flow - thick muscular wals to withstand high pressure -PRESSURE RESERVOIR
What two factors can cause pressure in the arteries to increase and decrease respectively?
increase in cardiac output= increase in pressure increased flow into capillaries= decrease in pressure
Veins- Characteristics
- large diameter, low pressure, \ -VOLUME RESERVOIR (50% of blood) -smooth muscles, sympathetitc adrenegetic fibres —-these are less elastic- will tear if pressure is hight -venous blood flow is affected by muscle contractions and valves (expansion of the chest helps move venous blood to the heart)
What happens when blood volume is lost from the venous system ie. giving blood
- vasoconstriction reduces the volume, so pressure stays constant as well as flow rate
What happens when blood pools in the veins
-venous return drops, cardiac output dops, arterial pressure drops, less blood to the brain= faint
Capillaries Characteristics
- approx 1 mm long 3-10um in diameter -endothelial cells with a basement membrane -extensive network an high surface area
What are the functions of the capillaries
- gas, nutrient and waste exchange -fluid exchange and balance
how does gas exchange and waste exchange occur in the capillaries
- down concentration gradients or partial pressure -gradient is determined by cellular metabolism
how does fluid exchange occur in the capillaries
- diffusion is porportional to permeability -lipid soluble substances pass through the membrane (o2 co2) -others (ions, water, glucose) pass through water-filled channels in the capillary walls (slower)
What are the three types of permeable capillaries
-continuous, fenestrated, sinusoidal
