Cardiovascular System Flashcards
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4 features of the mammalian cardiovascular system
- Four chambered heart
- Blood flows in one direction
- Arterial blood flows away from heart
- Venous blood flows towards heart
Name the series circuit
- Pulmonary —> systemic
Name the parallel circuit
- Systemic
What does the series circuit ensure?
- Ensures that all blood flows to the lungs before flowing through the systemic circulation and to all the organs
Features (3) of parallel circuits
- Arterial blood continually divides as it flows away from the heart
- All organs receive the oxygen-rich blood that left the lungs
- No organs receive the the carbon dioxide-rich blood leaving another organ (except the liver)
Define the variables that determine blood flow
- Flow = Pressure difference/resistance
- Q = ΔP/R
Features (2) of a BLOOD vascular system
- What type of system?
- A closed supply and drainage system
- A continuous loop
Features (2) of a LYMPHATIC vascular system
- What type of system?
- An open drainage system
- A one-way system
Organisation of the cardiovascular system
- SED
- Supply side
- Exchange network
- Drainage
Principles (4) of supply side
- Arteries are the only supply path
- Major arteries are situated to avoid damage
- Important structures often receive supply from two sources ( two separate structures)
- Arteries change their name at each major branch
Principles (1) of Exchange network
- Capillaries of varying degrees of permeability
- Continuous (controlled-tight) - 5-10um
- Fenestrated (leaky) - 5-10um - small intestine - kidney
- Sinusoidal (very leaky) - 20-30um - liver
Principles (2) for drainage
- What are the three pathways for drainage?
- What is the cross sectional area for veins?
- 3 pathways for drainage
- Deep veins
- Superficial veins
- Lymphatics
- Cross sectional area of veins is at least twice that of arteries
Right atrium receives?
- Superior vena cava
- Inferior vena cava
- Coronary sinus
Left atrium receives?
- Four pulmonary veins
Layers of the heart wall and what makes up them
Endocardium - Squamous epithelium Myocardium - Elastin & collagen Epicardium - Visceral serous pericardium - Loose irregular FCT -Blood vessels - Adipose Visceral pericardium pericardium fluid Parietal pericardium
The left & right ventricles wall features (3)
- Right ventricle = 0.5cm —> pulmonary arteries (lungs)
- left ventricle = 1.5cm —> Aorta (systemic)
- Muscular interventricular septum (wall b/w ventricles)
Atrioventricular (AV) valves function (3)
- Prevent blood returning to atria during ventricular contraction
- Right side - Tricuspid valve
- Left side - Bicuspid (mitral) valve
Operation of atrioventricular valves?
- Open = Diastole
- Close = Systole
Function (5) of semilunar valves
- Prevent blood from returning to ventricles during filling (diastole)
- Aortic (semilunar) valve, three cusps
- Pulmonary (semilunar) valve, three cusps
- Pushed open as blood flows out of heart
- Close as blood starts to backflow
cardiac muscle structure
- Striated
- Short fat, branched cells
- One (or occasionally 2) nuclei/cell
- Central (oval shaped), nucleus
- Intercalate disks (ICDs)
- Mitochondria 25% of volume of cell
- Irregular branched sarcomeres
Skeletal muscle structure
- Many nuclei (pushed to periphery)
- Mitochondria 2 % of skeletal cell
Cardiac muscle, intercalated disks features (3)
- Adhesion belts (linking actin to actin)
- Desmosomes (linking cytokeratin to cytokeratin)
- Gap junction (electrochemical communication)
Features of purkinje cells
- Some peripheral myofibrils
- Mitochondria
- Glycogen
- Some desmosomes
- Few adhesion belts
- Lots of gap junctions
- 1% of cardiac cells
Structure of Blood Vessels
- Tunica Intima
- Tunica Media
- Tunica Adventitia (externa)
Tunica intima structure
Endothelium
- A simple squamous epithelium which lines the lumen of all vessels
Subendothelium
- A sparse pad of loose FCT. Cushioning the endothelium
Internal Elastic Lamina (IEL)
- A condensed sheet of elastic tissue
- The IEL is well developed in arteries and less developed in veins
Tunica media (smooth muscle) structure
- A variable of connective tissue fibres
- Mainly elastin and collagen
- Thickness of media is proportional to both vessels diameter and blood pressure
Tunica Adventita (externa) Structure
- Loose FCT with a high content of collagen and variable amount of elastin
- In larger vessels, the adventitia contains vaso vasorum
- Lymphatics and autonomic nerves are also found in this region
features of vein
-Irregular, flattened shape with large lumen & thin wall
- Have spare capacity ( can take up extra blood volume)
= capacitance vessels
Structure of veins
Three layer
- Intima
- Media - Much thinner than arteries - a few layers of smooth muscle ( often in two distinct layers)
- Adventitia - often the thickest layer of a vein
Capillary Function & function demands
Function
- Site of exchange between blood and tissue
Function demands (3):
- Very thin walls
- Large total cross sectional area of capillary bed
- Slow & smooth blood flow
Side note - Large total area of the capillary bed (compared to arterioles), means much slower blood flow
Lymph Vascular system functions (4)
- Drains excess tissue fluid & plasma proteins from tissues and returns them to blood
- Filters foreign material from the lymph
- ‘Screens’ Lymph for foreign antigens & responds by releasing antibodies & activated immune cells
- Absorbs fat from intestine and transports to blood
The Lymphatic Structure
Lymphatic vessels
- Commence as large, blind ending capillaries
- From small intestine, a special group of lymphatic vessels called LACTEALS drain fat-laden lymph into a collecting vessel called the CISTERNA CHYLI
- Larger (thin wall) collecting vessels have numerous valves to prevent backflow
Features of a lymphatic vessel
- Filaments anchored to connective tissue
- Endothelial cell
- Flaplike minivalve
Regional lymph nodes
- Cervical nodes
- Axillary nodes
- Inguinal nodes
Features of a continuous capillary
- Lumen
- Intercellular cleft
- Endothelial fenestration (pore)
- Vesicles
- Basal lamina
- Diffusion through pore
- Diffusion through intercellular cleft
- Direct diffusion
Cellular mechanism of cardiac contraction
(1) Increase in cytosolic Ca2+ levels
- Ca2+ induced Ca2+ release from sarcoplasmic reticulum (SR)
(2) Actin binding site revealed
- Myosin binds forming the X-bridge
(3) A/M filaments slide relative to each other
- Sarcomere shortens
- Force generated
(4) Every myocyte activated each heart beat
Ways to increase cardiac contraction
(1) Every cardiomyocyte is activated during each heart beat
(2) Extent of x-bridges formed not maximized at rest…
- ↑ cytosolic Ca2+ level
- ↑ number of x-bridges formed
- ↑ force of contraction
Cellular mechanism of cardiac relaxaition
(1) ATP binds to myosin
(2) Decrease in cytosolic Ca2+ levels
- Ca2+ into SR
(3) X- bridges release
- A/M separate
(4) Reduction in force
(5) All cardiac myocytes relax each beat
Anatomical basis of cardiac contraction
- Cardiac muscle fibres in helical pattern
- Heart twist and controls as it contracts
Cardiac cycle and it’s main phases
Atrial systole → isovolumetric ventricular contraction → ejection → Isovolumetric ventricular relaxation → passive ventricular filling
Features (4) of Pulsatile blood flow in arteries
- Continuous flow in capillaries
- Intermittent injection of blood into aorta from the left ventricle
- Elastic arteries - stretches then recoils - storing and releasing energy
- cycles of increase (systolic) and decrease (diastolic) pressure
- Pulse wave is a pressure wave - travels along the arteries - ahead of the blood
Features (2) of Electrical cells of the heart
- 1%
- ‘Pale’ striated appearance - low actin and myosin
Features (3) of contractile cells of the heart
- Striated appearance
- High actin and myosin
- ‘working myocardial cell’
electrical “wiring” of the heart:
6 parts of the conduction pathway
(1) Sinoatrial (SA) node (pacemaker) → interatrial bundle & fibres → (2) Left atrium & (3) Right atrium
Internodal bundle & fibres→ (4) Atrioventricular (AV) node
→ Subendocardial branches (purkinje fibres) → (5) Lateral wall & septum of right ventricle & (6) Lateral wall and septum of Left ventricle
ECG and cardiac cycle
P wave - Atrial depolarisation - Atrial contraction QRS complex - Ventricular depolarisation - Ventricular contraction - Rise in ventricular pressure - Ejection of blood - Fall in ventricular volume - Rise in aortic pressure T wave - Ventricular repolarisation - Ventricular relaxation .... fall in ventricular pressure .... atrioventricular valves open ... filling of the ventricles occur
Blood pressures throughout the systemic circulation
- Blood pressure high in major arteries - Oscillatory
- Blood pressure falls steeply across the “microcirculation”
- Oscillatory nature is reduced
- Blood pressure is very low in veins
- Large difference in pressure (ΔP) between the arterials and venous sides
- Creates a driving force for blood flow
Blood pressure throughout the systemic system
- Highest to lowest
Left ventricle → large arteries → resistance vessels → capillaries & pulmonary artery → venules → veins
Ejection of blood into the arterial system
- maintains arterial blood volume and blood pressure
Features of “Blood flows in”
- Fills arteries
- Raises arterial pressure
- Increases arterial blood volume
Ejection of blood into the arterial system
- maintains arterial blood volume and blood pressure
Feature of “Blood flows out”
- Drains arteries
- Decreases arterial blood volume
- Lowers arterial pressure
What is arterial blood volume and pressure determined by?
Balance between blood flows “in” and “out”
Cardiac output and arterial resistance effect blood pressure
Features of “Blood flow in”
- Ventricular contraction
- Ejection of blood
- CARDIAC OUTPUT
Cardiac output and arterial resistance effect blood pressure
Features of “Blood flow out”
- Capillary flow
- Controlled by resistance of the arteries
Balance flow in/out determines pressure
- Increase cardiac output (increase inflow)
- Increase resistance (decrease outflow)
- Increase arterial volume and pressure
MAP = CO x TPR
Arterial pressure = cardiac output x total peripheral resistance
Cardiac output is determined by?
Cardiac Output (L/min) = Stroke Volume (L/beat - pulse strength) x Heart Rate (beats/min - Pulse speed)
Is the stroke volume of the Leaf and Right ventricle the same?
Yes
Features of homeostasis of arterial blood pressure control of the heart and blood vessels
Mean arterial pressure is tightly regulated - narrow range MAP = CO x TPR - Heart (cardiac output) - Blood vessels (vascular resistance) Co-ordinated within the brainstem - Afferent input from both the CNS and 'periphery' - Efferent output to heart and vessels
How is MAP controlled during exercise?
- Increase cardiac output
- Constant mean arterial pressure
- Decreased total peripheral resistance
What controls vascular resistance?
Local (Mechanical - response to force)
- from within the vessels (blood pressure)
- From outside the vessel (e.g. swelling)
Central
- Neural - vascular sympathetic nerves
- Humoral (blood) - hormones released from remote organs - e.g. adrenaline
Compliance definition & equation
- The extent to which a vessel allows deformation in response to an applied force
- ΔV/ΔP
Compliance of Vein vs Artery
- Vein = thin wall → compliant
- Vein - Large volume = small pressure = high compliance
- Artery = think wall → rigid
- Artery - Small volume = large pressure = low compliance
Features of blood transfusion from venous to arterial system
- Arterial puncture
- Loss of arterial blood
- Life threatening fall in arterial pressure
- Leads to vasoconstriction (under neural control)
- Blood transfusion from venous to arterial system
Features (4) of High vascular compliance (pooling in veins)
- Venous volume (blue) is larger than arterial volume (red)
- While supine (laying down), venous volume is uniform from head to toe
- In the upright position, venous volume below the heart increases; whereas venous volume above the heart decreases
- Extreme venous pooling in the legs and feet
Features (2) of venous valve counteracting venous pooling
- No valves → continuous column: heavy at bottom
- Valves → discontinuous column: more even distribution of weight
Features (4) of ‘tone’ of surrounding tissue counteracting venous pooling
- Particularly the case for skeletal muscle, because it can alter it’s tensile state
- resting muscle tone varies between individuals
- Muscle tone acts to stiffen the veins - makes them less compliant and prone to pooling
- Some people prone to fainting have low muscle tone and excessive venous pooling
How does the skeletal muscle pump affect ‘venous return’ to the heart?
- Muscle relaxed = low pressure
- Muscle contracted = high pressure
- Muscle contraction increase venous blood flow
- Increased venous return means increase stroke volume
Features (3) of Starlings law of the heart
- The more stretched muscle fibres are before a contraction, the stronger the contraction will be
- ↑ in stroke volume (mL) = ↑ ventricular volume (mL) at end of diastole - increasing venous return
- ↑ venous return means ↑ stroke volume
