Lecture 54 - Cardiovascular Function 2 Flashcards
What are the main functions of the cardiovascular system?
Transport:
• Nutrients, water, gases
• Signals
• Wastes
What are the signals that the cardiovascular system transports?
- Hormones
- Inflammatory mediators
- Antibodies
- Clotting Factors
Which wastes does the cardiovascular system carry away from cells?
- CO2
* Metabolic wastes
Do veins carry oxygen?
Yes
Not as much as the arteries
Which structure in the body has the most well oxygenated blood?
Pulmonary vein
Which structure in the body has the least well oxygenated blood?
Coronary sinus
The heart extracts the most oxygen out of the blood.
What are the two circulations in the body?
Pulmonary circulation
• from right side of heart to lungs
Systemic circulation
• from the left side of the heart to the body
What is the definition of a portal system?
Give some examples
Two capillary beds in series
- hepatic portal system
- kidneys
- hypothalamic portal system
Where in the body is the blood at the highest and lowest pressure?
Highest: aorta
Lowest: vena cavae
How does blood flow?
From areas of high pressure to areas of low pressure
What is responsible for the fall in pressure in circulation?
Friction against the walls of the vessels
What is the definition of flow?
Vol / time
What is flow proportional to?
Inversely proportional to?
Proportional to pressure gradient
Inversely proportional to resistance
What is resistance?
Radius of tube
Length of tube
Viscosity
More flow in:
Smoothie or water?
Water
More flow in:
Yakult or crazy straw?
Yakult
More flow in:
bubble tea straw or cocktail straw?
Bubble tea straw
Which variable of the blood is easiest to rapidly change?
Vessel radius
What is muscle tone?
The state of partial contraction at all times of the smooth muscle in the smooth muscle
What is happening in vasodilation?
Relaxtion of the smooth muscle in the blood vessels
What happens during hyperventilation
- All the CO2 is being expelled
- Drop in partial pressure of CO2 in blood
- Vasoconstriction
- Decrease in blood flow to the head
- Fainting
Where is blood flow the slowest?
Why?
Capillaries
Very high cross sectional area, flow rate is constant
Thus, the velocity is decreased.
Which vessels don’t have elastic fibres?
Which do?
- Capillary
- Venule
- Arteriole
Arteries and veins have elastic tissue
Which vessels have smooth muscle?
Arteries and veins and arterioles
Are the walls of arteries floppy?
What does this mean?
No, stiff
Substantial energy required to stretch the walls outward
What is the Windkessel effect?
Walls of the arteries distend when BP rises during systole
Recoil: the elastic energy stored in the stretched artery pushes the blood forward
When does the Windkessel effect diminish?
As we get older
Due to atherosclerosis
Where is most of the blood volume at any one time?
Veins: 64%
Compare veins to arteries
More numerous
Less elastic & wider
Expand easily → reservoir for blood
Solute concentration is higher in A than in B.
Where does water flow?
Flows into A
What is Fick’s law of diffusion?
Proportionate to:
• Surface area
• Permeability
• Concentration gradient
Inversely proportionate to:
• Thickness
Describe the structure and function of capillaries
One cell thick: endothelium
→ maximises diffusion across according to Fick’s law of diffusion
Compare intestitial and plasma fluid
- Solute: almost equal
* Protein: high in plasma, low in interstitial fluid
Describe the modes of transport across capillaries
- Diffusion: small molecules etc.
- Vesicular transport: protein
- Bulk flow
Describe bulk flow
Overall mass movement of fluid between plasma and interstitial fluid
Due to hydrostatic / osmotic pressure gradients
What are the two types of bulk flow?
Distinguish them
Filtration: out of capillary
Absorption: into capillary
What are the forces that regulate bulk flow?
What are these also known as
1/ Colloid osmotic pressure
• plasma proteins
2/ Hydrostatic pressure
• pushing of blood out through the capillaries
• blood exerting pressure on the walls of the vessel
Describe the change in hydrostatic pressure as blood flows along a capillary
Energy lost to friction
Decrease in hydrostatic pressure
Which pressures favour filtration?
Capillary hydrostatic pressure
Interstitial oncotic pressure
Which pressures favour absorption?
Interstitial hydrostatic pressure
Plasma oncotic pressure
What is the main thing in the plasma that contributed to plasma oncotic pressure?
Plasma proteins
• Albumin
What is bulk flow?
Balance of filtration and absorption
Filtration =
Pc - Pif
Absorption =
Colloid osmotic (interstitial) - Colloid osmotic (capillary)
Net pressure =
Hydrostatic P + Colloid Osmotic P
What is the change in hydrostatic pressure along the capillary?
Decrease in Hydrostatic pressure
What is the change in colloid osmotic pressure along the capillary?
Assumed to be roughly constant
There is net bulk flow out of capillaries.
Where does the extra fluid go?
Into the lymphatics
Describe the flow of fluid from intertstitial fluid
- Interstitial fluid
- Lymph vessels
- Larger lymph vessels
- Lymph ducts
- Venous circulation
What happens when Bulk flow is greater than lymphatic drainage?
Oedema
How does the lymph system function?
Smooth muscle in lymphatic vessel walls
One way valves
Muscle pump also aids flow of lymph
What are the functions of the lymph system?
- Return fluid and proteins to circulation
- Pick up fats absorbed from small intestine
- Immune system, movement of antigens and white cells
What are some circumstances under which there would be oedema?
Severe malnutrition Decrease in blood protein concentration Obstruction of lymph nodes Fluid overload Heart failure → increase in venous pressure
How does the heart make blood flow?
It creates a pressure gradient
