Flashcards in Circulatory System Deck (54):
Major arteries of abdomen/leg?
Common iliac artery
External iliac artery
Posterior tibial artery
Major veins of abdomen/leg?
Common iliac vein
External iliac vein
Great saphenous vein (superficial)
Small saphenous vein (superficial)
Posterior tibial vein
Systemic and Pulmonary Circuits: which lies in parallel and which lies in series?
Equation for blood flow in a vessel
Flow = Pressure difference/Resistance
(F = P/R)
What are the 3 degrees of permeability for capillaries?
Sinusoidal (v leaky)
3 pathways for drainage?
Layers of the heart wall & function; (incl. sac)
1. Endocardium: barrier layer
2. Myocardium: muscle layer
3. Epicardium: supply & drainage
- Pericardium: covers heart
- How many valves on each side?
- Diastole vs systole?
- Prevent blood returning to atria during ventricular contraction
- RHS tricuspid & LHS bicuspid
- Diastole is open & systole is closed
Left ventricle: structure/function of;
- Papillary muscles
- Chordae tendinae
- Papillary muscles: finger-like projections attached to chordae tendinae
- Chordae tendinae: 'heart strings' attached to AV cuspids
--> prevents valves from slamming shut & swinging into atrial chamber
- How many valves?
- Prevent blood from returning to ventricles during diastole
- Aortic valve: 3 cuspids
- Pulmonary valve: 3 cuspids
Difference b/w cardiac & skeletal muscle
Cardiac: short, fat, branched; central nucleus; ICDs
Skeletal: long, thin, linear; peripheral nuclei; no ICDs
3 junctions of ICDs? (Intercalated disks)
1. Adhesion belts: link actin to actin; synchronised propagation
2. Desmosomes: link cytokeratin to cytokeratin; holds cells together
3. Gap junction: electrochemical communication
3 Layers of blood vessel wall
Layers of intima & their function
1. Endothelium; non-stick surface
2. Sub-endothelium; cushion
3. Internal Elastic Lamina; provide elasticity & resilience
What is the media composed of?
Smooth muscle & connective tissue fibres (mainly elastin & collagen)
What is the adventitia composed of? Function?
- Loose FCT w/ lots of collagen & some elastin
- Protective sheath around vessel
Histological structure of arteries (deep to superficial)
Function of arterioles
- resistance vessels
- determine BP
Histological structure of veins
Function of venules
- start of the drainage system (smallest/first veins)
- contain venus valves
Functions of lymph vascular system
1. Drainage of excess tissue fluid & return to blood
3. Defence (screens for antigens, releases antibodies/activates immune cells)
4. Fat absorption
Describe the cardiac cycle
1. Atrial systole; atria contract, AV valves open, blood flows into ventricles
2. Isometric ventricular contraction; ventricles contract, atria relax, all valves closed (pressure builds)
3. Ejection; blood leaves ventricles via SL valves, AV closed
4. Isometric ventricular relaxation; blood enters atria, all valves closed
5. Passive ventricular filling; AV valves open
3 Stages of cardiac contraction
1. Increase in cytosolic Ca2+ levels (induces Ca2+ release from SR)
2. Exposure of actin binding site (allows myosin to bind --> cross bridge)
3. A&M filaments slide across each other (contraction)
How do you increase the force of cardiac contraction?
Increase the cytosolic Ca2+ level
How do you calculate pulse?
Difference b/w highest & lowest BP in cardiac cycle
How do elastic arteries regulate the blood pressure wave to provide continuous blood flow to the capillaries?
Store energy/force by expanding at high pressure and release it by contracting at low pressure
1. SA node (generated)
- travel via interatrial bundle and internodal bundle
2. Right & left atria, paused in AV node
- travel via AV bundle, then L & R branch
- travel via purkinje fibres
4. Lateral wall (ventricles)
Features of the ECG trace
1. P-wave: SAN pulse & atrial depolarisation
2. QRS: ventricular depolarisation & atrial depolarisation
3. T-wave: ventricular repolarisation
How do you calculate arterial pressure?
CO (cardiac output) x TPR (resistance)
What is cardiac output? What is it determined by?
- The blood flow leaving the heart
- Determined by stroke vol. (SV) and HR
How are SV and HR controlled?
HR: by vagal and/or sympathetic activity to the SAN
SV: by changing sympathetic activity to the contractile cells
What is needed for organs to have fine vascular control of blood flow?
High arterial blood pressure (MAP)
What is the approximate relative distribution of blood to the body's organs at rest?
Skeletal muscle (29%)
GI system (25%)
Coronary circulation (4.5%)
How does the distribution of blood flow change during exercise?
- Increased flow to muscle, the heart, and the skin (except not the skin during maximal exercise)
- Decreased flow to GI tract & kidney (rest and digest organs)
- Distribution to brain doesn't change
How does MAP stay constant during exercise?
MAP = CO x TPR
thus, since CO increases and TPR decreases, it stays approx. constant.
Which organs increase resistance and which organs decrease it?
- Increase: kidneys, intestines, spleen, etc.
- Decrease: heart, muscle, skin
Why are arterioles effective resistance vessels?
1. Many of them
2. Small changes in diameter make significant difference to blood flow (R = 1/(r)^4)
What is vascular compliance? What is the relative compliance of arteries vs veins? Why is this?
- Compliance is the vessel's ability to change shape in response to a changing internal pressure.
- Arteries have low compliance bc they have a thick wall & veins have high compliance bc they have a thin wall.
What is the equation for compliance?
C = change in volume / change in pressure
What is venoconstriction useful for?
Transfusing stored blood in the veins into the arterial system when MAP is low.
What is venous pooling & what mechanisms counteract it?
- The accumulation of blood in the veins due to their high compliance.
- venous valves and tissue tone
What is the effect of skeletal muscle contraction on venous blood flow? Why?
- Increases flow
- Push on veins which increases pressure and forces blood forward (not back, bc of valves)
What is Starling's law of the heart? How does it relate to venous return?
- The more stretched muscle fibres are before a contraction, the stronger the contraction will be.
- The more blood that returns to the heart = the more that leaves = the higher the stroke vol.
How do you calculate stroke volume?
Vol. of blood in heart before contraction - vol. of blood in heart after contraction.
What are 3 nodes which are involved in the immune response? (bc they bathe immune cells)
Where does the right lymphatic duct go to?
Right subclavian vein
Where does the lymph from the small intestines go to? Where does it go from there?
Cysterna chyli --> thoracic duct --> left subclavian vein
What is the anatomical basis of contraction of the heart?
Helical muscle fibres; squeezing/twisting/contorting movement
How do elastic arteries maintain a relatively constant pressure/flow despite the pulsatile nature of blood in the arteries?
They stretch when a large amount of blood flows through, and recoil when the volume drops.
What is the conduction pathway of the heart?
SAN --> atria --> AVN --> AV bundle --> lateral wall (purkinje fibres)
How is BP controlled?
- Coordinated in the brainstem
- Baroreceptors in the aorta and carotid arteries (neck) detect change
- Low BP: (SNS)
medulla --> spinal cord --> sympathetic ganglia --> nodes --> increased HR
- High BP: (PSNS)
medulla --> venus nerve --> nodes --> decreased HR
State what happens to each of the following when someone's standing upright:
HR increases (to compensate)
CO decreases (slightly)
VR increases (to compensate for decreased CO)
MAP remains relatively constant
What is the normal BP for:
Systolic = 120
Diastolic = 80
MAP = 90-100