The circulatory system Flashcards
Describe the circulatory system of a unicellular organism
Simple diffusion
Convection
Steep conc gradient for nutrient/waste exchange
What is the primary function of the circulation system?
Distribution of gases/molecules
(nutrition, growth and repair)
What are the secondary functions of the circulation system?
Fast chemical signalling
Dissipation of heat
Mediates inflammatory and host defences to microbes
What regulation is required in order to change circulatory demands?
Body position/inthoracic pressure
Rest (deceleration of hr)
Emotional stress
Digestion
Sleep/wake
What are the 3 main components of the circ system?
- Pump (heart)
- Fluid (blood)
- Containers (blood vessels)
Pathway of blood around the body (from left heart)
Left atrium -> left ventricle via mitral valve -> Aorta via aortic valve -> into various organ systems -> right atrium via vena cava -> right ventricle via tricuspid valve -> lungs via pulmonary artery -> left atrium via pulmonary vein
Which side of the heart carries oxygenated blood?
The left side
What type of circulation is used by the left heart?
Systemic circulation
What type of circulation is used by the right heart?
Pulmonary circulation
Function of arteries
Distribution system (high pressure system)
Function of microcirculation
Diffusion and filtration
Function of veins
Collection system (reservoir)
Size of first order arteriole and venule
30 um
Size of fourth order arteriole and venule
5 um
Size of capillary
3 um
Is the combined cross-sectional area of the daughter vessels larger or smaller than the parent?
Larger
Describe the structure of a vascular wall
- Endothelial cells
- Elastic fibres
- Collagen fibres
- Vascular smooth muscle cells
Describe the structure of blood vessel walls
- Intima (tunica interna)
- Media (tunica media)
- Adventitia (tunica externa)
Structure of a capillary wall
Tunica intima which rests on the basement membrane
Specialisation of elastic arteries
High compliance
Enable vessels to cope with peak ejection
Recoil forces blood to move even when ventricles are relaxed
Specialisation of muscular arteries
Greater vasoconstriction/vasodilation
SMC arranged circumferentially
Vascular tone (efficient flow)
Specialisation of arterioles
Smooth muscle enables blood flow to capillary networks
Terminal regions
Precapillary sphincters (regulate blood flow to capillaries)
Specialisation of venules
Porous
Thin smooth muscle layer
Thin walls for expansion (reservoirs)
Specialisation of venules
Porous
Thin smooth muscle layer
Thin walls for expansion (reservoirs)
Specialisation of veins
Elastic but distensible
‘Store’ blood
Large veins have valves to prevent backflow
What can lead to varicose veins?
Defective and leaky valves in veins ->
Blackflow
Functions of capillary exchange
Glomerular filtrate
Skin temperature regulation
Hormone delivery
Platelet deliver
Structure of capillaries
Endothelial cells and basement membrane
What are the 3 groups of capillaries from most-least leaky
- Continuous capillary
- Fenestrated capillary
- Sinusoidal (discontinuous) capillary
What is oncotic pressure a result of?
Serum proteins (albumin)
What is starling equation showing?
The fluid transfer across capillary walls due to a sum of hydrostatic and osmotic pressures
What happens to Pc as it travels across the length of a capillary? Why?
Pc (capillary hydrostatic pressure) decreases along the length so filtration becomes absorption
Due to fluid filtration
Function of the lymphatic system
Drains excess interstitial fluid in all organs but the brain
Maintenance of blood volume
What vein is lymph returned to CVS via?
Subclavian veins
