Final: Circulation 7 Flashcards
net filtration pressure (NFP) (3)
- based on the Starling principle
- may result in net filtration or net reabsorption across capillary membrane
- creates a micro-circulation to mix interstitial fluids around the capillaries
NFP formula
NFP = (Pcap - Pif) - (πcap - πif)
NFP formula: Pcap
- hydrostatic pressure of blood in capillary
NFP formula: Pif
- hydrostatic pressure of interstitial fluid
NFP formula: πcap
- osmotic pressure in the capillary
NFP formula: πif
- osmotic pressure of interstitial fluid
what determines osmotic pressure (2)
- determines by concentration of salts and proteins in a solution
- water will move to solution with higher concentration of salts + proteins
hydrostatic pressure (2)
- pressure of a column of fluid due to gravity
- the area with high hydrostatic pressure will force fluid to the area of lower hydrostatic pressure
NFP: arterial side of capillary (3)
- Pcap > πcap
- NFP is positive
- net filtration occurs
NFP: middle of capillary (3)
- Pcap = πcap
- NFP is ~0
- net movement is zero
NFP: venous side of capillary (3)
- Pcap < πcap
- NFP is negative
- net reabsorption occurs
lymphatic system: functions (2)
- collects excess filtered fluid and returns it to the circulatory system
- lymph nodes filter lymph to remove and kill pathogens
how does fluid move through the lymphatic system (2)
- net water pressures and body movement drive fluid movement
- lymphatic veins and ducts contains valves to prevent backflow
edema (2)
- accumulation of interstitial fluid
- can be due to ineffective lymphatic system
gravity on blood pressure: formula
ΔP = p * g * Δh
gravity on blood pressure: ΔP
- pressure difference between two points
gravity on blood pressure: Δh
- height of the fluid column
gravity on blood pressure: p
- density of the fluid
gravity on blood pressure: g
- acceleration due to gravity
what are the arterial and venous pressures at our heart due to gravity (standing) (2)
- arterial: 100 mmHg
- venous: 10 mmHg
how much lower are venous pressures than arterial pressures due to gravity
- venous pressure at each height are ~100 mmHg lower to permit blood flow
how does body position affect blood pressure
- changes in body position can alter blood pressure and flow
- changes relative to gravity, such as standing up
body positions and blood pressure: standing up (2)
- causes pooling of blood in lower body
- due to low venous return, low SV, and low MAP
how does our body regulate MAP when we stand up (2)
- baroreceptor reflex brings MAP back to normal
- increases HR and SV to raise MAP
orthostatic hypotension (2)
- low blood pressure upon standing
- occurs when baroreceptor reflex is too slow and not enough blood flows to the head
in what animals are the effects of gravity more important (2)
- snakes
- giraffe
how do snakes deal with gravity
- heart is close to the brain so that it is guaranteed blood flow regardless of body position
how do giraffes deal with body position changes (2)
- vasoconstriction occurs in vessels of lower body when the head is upright and aortic pressure increases
- vasodilation occurs in the vessels of the lower body when the head is feeding on ground and aortic pressure decreases
giraffes and gravity: head problem
- heart must generate sufficient pressure to overcome hydrostatic pressure
giraffes and gravity: head solution (2)
- thick-walled heart with low stroke volume & fast heartbeat
- generate very high MAP
giraffes and gravity: feet problem
- giraffe must have solution to counter blood pooling in their legs and feet
giraffes and gravity: feet solution (4)
- giraffe arteries are usually muscular
- skin on legs is very tight, acting as a compression stocking
- tight endothelium to prevent H20 loss
- venous valves
gravitational effects on cardiovascular function in air
- pressure increases with height of the water column, causing pooling/high pressure at the bottom
gravitational effects on cardiovascular function in water (2)
- blood and water have similar density and hydrostatic pressure
- effects outside the animal cancel out gravitational effect, acting as a large “compression stocking”
