Lecture 14: The Vascular System Flashcards
What is the job of the pulmonary and systemic circuits?
Pulmonary circuit
- supplied by right heart
- blood vessels to and from heart and lungs
Systemic circuit:
- supplied by left heart
- blood vessels to and from heart and systemic tissues
Fundamentals of vascular blood flow
- Vascular system is divided into 2 circulations, the pulmonary and systemic circulations
- each circulation is a closed system of blood vessels
- the circulations has both series and parallel components
Series circuit: components connected by a single path
Parallel circuit: components connected by multiple, alternative pathways
Describe how there is parallel flow through the cardiovascular system
Blood flows in parallel through the different capillary beds of the systemic circuit
Advantages:
-each capillary bed receive fully oxygenated blood
-blood flow to different organs can be regulated independently
Exception: GI tract and liver are connected in series
What to things determine blood flow through the body?
Pressure gradient/resistance
What are the cellular components of a blood vessel?
- all blood vessels have a hollow interior, the lumen
- all blood vessels are lined by an endothelial cell layer
- some types of blood vessels also have
- smooth muscle (➡contractile control of radius)
- fibrous connective tissue (➡strength)
- elastic connective tissue (➡stretch, recoil)
Arteries and veins are names according to the direction of blood flow, NOT oxygenation.
True or false
True
What is the properties and function of each of these vessels?
Arteries: P: large, elastic. Function: store pressure Arterioles: P: quite small, variable diameter. Function: resistance, regulate blood flow Capillaries: P: small, thin walled F: blood- tissue exchange Venules: P: small, thin-walled F: blood- tissue exchange Veins: P: large, variable diameter F: store blood
Arteries. Describe
-Large branching vessels that conduct blood away from the heart
-rapid transport pathway: Large diameter➡little resistance
-store blood pressure:
➡Thick walls➡ low compliance➡ small increase in blood volume causes a large increase in pressure
-elastic walls ➡ stretch during systole, store energy, recoil during diastole, maintaining arterial BP
Describe muscular arteries
Small arteries supplying tissues
- little elastin
- smooth muscle regulates radius
- structurally and functionally more like arterioles
Describe arterioles
Small branching vessels that conduct blood away from heart. High resistance (small and not many of them (compared with capillaries) Variable resistance (depends on contractile state of rings of smooth muscle in walls)
Arterioles and total peripheral resistance.
What is peripheral resistance?
How do arterialise effect it?
TPR= combined resistance of all blood vessels in the systemic circuit. Arterioles provide greatest resistance to blood flow of all vessels >60% of TPR
How do arterioles regulate blood flow?
The resistance of arterioles is regulated
Arterioles play important roles in
1) regulating mean arterial pressure
2) controlling flow to individual capillary beds
Both intrinsic (local) and extrinsic (neural, hormonal) control of arteriolar radius
Capillaries
What are they
What’s their function?
Sit of exchange between blood and tissue
-single porous endothelial cell layer ➡minimal diffusion distance (most cells within 1mm of capillary)
-high cross sectional area, low velocity blood flow, allows exchange
Blood flow through capillary beds is highly regulated
What are the 2 functions of movement of material across capillary walls
1) exchange of material
- waste, nutrients
- different mechanisms depending on solute (passive diffusion, mediated transport etc)
2) distribution of the extracellular fluid (bulk flow) = mass movement of water and dissolved solutes according to pressure gradients
What is the purpose of bulk flow across capillary beds?
Bulk flow= mass movement of water and dissolved solutes according to pressure gradients
Purpose of bulk flow is to distribute the ECF
Filtration= movement out of capillary
Absorption= movement into capillary