circulatory system Flashcards
2 main parts of the circulatory system
pulmonary and systemics circuits
blood flows…
unidirectionally in the body through and the heart
Endothelium - blood vessels
common, inner cell lining, single cell layer thick
Elastic tissue - blood vessels
stretch, extend and come back to shape, in veins and arteries
Smooth muscle - blood vessels
contraction and relaxation of blood vessels, maintain pressure within the system
main component of arteriole
Fibrous tissue - blood vessels
Provides structure
main component of venule
Arteriole
resistance vessels within the body, tightly regulated, regulation of blood to underlying tissue
Capillaries
where exchange occurs (gasses)
pulmonary circulation
1st circulation
Blood from heart > gets oxygenated in lungs > returns to heart
Oxygenated blood leaves heart via
aorta (largest): thick muscular structure - relates to pressure
Blood goes everywhere
systemic circulation
2nd circulation
Takes oxygenated to blood to the rest of the body
Arteries
Away from heart
Veins
Return to heart
Circulation and how blood flows
Typical Artery > arteriole > capillary bed > venule > vein
Portal systems: additional filtration
What is blood?
It is a connective tissue made up of cellular elements, suspended in a fluid matrix
transport O2
blood composition
92% water
7% protein
1% dissolved organic molecules
cellular elements of blood
RBC
WBC
Platelets
types of WBC
Lymphocytes
Monocytes
Neutrophils
Eosinophils
Basophils
Erythropoiesis
Controlled by the glycoprotein erythropoietin (EPO) + some cytokines
* Produced by the kidneys
* The trigger for EPO release is hypoxia (low blood O2 lvls)
Blood doping
Used to improve athletic performance by artificially improving the body’s ability to transport O2 to the tissues/muscles
Three common types:
1. Blood transfusion
2. Injection of EPO
3. Injection of synthetic O2 carriers
Heart
The workhouse of the body:
Generates a pressure to force blood continuously around the body
Composed predominantly of cardiac muscle
Tricuspid valve
3 cusps
Stops blood backflow from right ventricle into the right atrium
Bicuspid valve
2 cusps
Stop blood flowing backwards from left ventricle into left atrium
Aortic semilunar valve
3 cusps
determine the passage of blood between the ventricles and the main arteries, transporting blood away from the heart to the vital organs
How does the heart contract?
Specialised cells within the heart generate an electrical signal to coordinate contraction
1. Sinoatrial node (S node)
2. Atrioventricular node (AV node) - down Bundles of His
3. Purkinje fibres
Depolarises the membrane, spreading rapidly throughout the conducting pathway
Systole
pressure in the arteries when the heart has contracted
Diastole
pressure in the arteries when the heart is fully relaxed
Mechanical events of the heart
Cycles between contraction (systole) and relaxation (diastole)
after each beat,
blood still remains in the heart (65mL)
* never “empty” heart
* protective mechanism
stroke volume (SV)
the volume ejected after each contraction
Performance is measured by…
cardiac output CO
CO = SV X HR
CO = 70 mL/beat x 72 bpm = 5.4 L/min
HR is altered by…
ANS
* by changes to the depolarisation of the autorhythmic cells
Arterial system is under…
high pressure
Venous system is under…
low pressure
Why does blood pressure decrease as we get further away from the heart?
Picking up friction from blood vessel walls
blood pressure
normal : 120/80 mmHg
As the heart oscillates between contraction and relaxation, measurements are taken at these points
* 120 mmHg is the systolic pressure
* 80 mmHg is the diastolic pressure
postural hypotension
- If we don’t move our legs we cannot bring blood to the heart
- Low pressure assoc. with the venous side of the circulation
- Standing causes our blood to pool at the feet
- If not enough blood is returning to the heart, we faint to “rectify” the problem
- Take away effect of gravity
Capillary transport
Deliver key nutrients and remove wastes from tissue
Transcytosis (capillary trans)
Package within cells and move across membrane
Bulk flow (capillary trans)
Mass movement of molecules and water into interstitial fluid
Driven by pressures
Movement between endothelium (capillary trans)
Between cells themselves - soluble/small/particular charge
Continuous capillaries
Leaky junctions
Allow water and small dissolved solute to pass through
Fenestrated capillaries
Large pores
Allow additional movement
Found in the kidney, brain etc.
Lymphatic system
Returned fluid lost in interstitial space back to the circulatory system
Fat absorption from gut into circulation
Destroy foreign pathogens
