hubs192 M2 cardiovascular system

what is the role of the heart in the cardiovascular system?

the pump - provide pulsile pressure

what is the role of the arteries in the cardiovascular system?

supply path (for capillaries) - for the exchange between blood and tissues

what is the role of the veins/lymphatics in the cardiovascular system?

drainage - fluid to go back to heart

what is vascular tissue made up of?

• connective tissues

• cells

  • epithelia cells

  • muscle cells

what is the blood vascular system?

a closed loops supply and drainage system between the heart→exchange capillaries→heart

what is the lymphatic (vascular) system

an open entry drainage system which picks up any fluid that has leaked and returns it back to heart

what are the general principals of the supply side of the heart (LHS)

• arteries are the only supply path

• major arteries are situated to avoid damage (high pressure)

• important structures receive supply form more than 1 source

• arteries change their name at each major branch

what are the 3 different types of capillaries based on permeability?

1. continuous (controlled/tight) - most common

2. fenestrated (leaky)

3. sinusoidal (very leaky)

what are the general principles of the drainage side of the heart? (RHS)

3 pathways for drainage

• deep veins (opposite to arteries)

• superficial veins

• lymphatics

cross sectional area of veins is at least twice the that of arteries

• so that ml/s of blood moved is equal

what is the shape of the heart?

• size of loose fist

• blunt, cone shaped

• pointed end = apex (ribs 5/6)

• blunt end = base (ribs 2/3)

• it is rotated to point to the left and tilted back so that the right side is anterior

• PMI (max impulse) and apex beat can be heard at ribs 5/6 at the LHS midclavicular line

what is the blood flow direction of the superior vena cava?

into the heart (top) from the chest and arms

(vena cavas are largest vein in body)

what are the 4 ventricles of the heart and the 2 dividing sections

• right atrium

• right ventricle

• left atrium

• left ventricle

• interatrial septum

• interventricular septum

what is the blood flow direction of the opening of the coronary sinus?

into the right atrium of the blood used by the heart itself

what is the blood flow direction of the inferior vena cava?

into the heart (bottom) from everywhere below the diaphragm

(vena cavas are largest veins in the body)

what is the blood flow direction of the left and right pulmonary veins?

oxygenated blood into the sides of the heart from the lungs to the aorta and out to the rest of the body

what to the left and right atria of the heart recieve?

• only receive and are thin walled

RHS: deoxygenated blood

• superior vena cava

• inferior vena cava

• coronary sinus

LHS: oxygenated blood

• four pulmonary veins

what are the 3 layers of the heart wall?

superficial

• epicardium (upon)

  • made of visceral pericardium - continuous w/ sac

  • blood vessels - large

  • loose irregular FCT and adipose

• myocarium (muscle) - thickest layer/contracts the heart

• endocardium (within)

  • made of simple squamous epithelium (endothelium) which line whole cardiac system and prevents clotting

  • this rests on loose irregular fibrous connective tissue FCT(mostly collagen) - protective

deep

what is the sac called which surrounds the heart?

pericardium - not part of the 3 layers of the heart but is continuous with the outermost layer (epi)

• made up of outer wall = parietal pericardium

• inner wall = visceral pericardium

  • both one continuous tissue folded

• space in between = pericardial fluid

provides protection for the heart (tough/leathery) and lubrication for the beating

there is also the ‘fibrous pericardium’ which sits on top of the parietal layer

what is the differences in thickness of the left and right ventricle ?

right = 0.5cm

left = 1.5 (x3) but only myocardial layer increases as needs to produce more force

what are the 2 main valves of the heart?

Left and right

• semilunar valves

• atrioventricular (AV) valves

what is the function of the atrioventricular (AV) valves? and specific names of the left and right one?

function:

• prevent blood from returning to atria during ventricular contraction (closed in systole)

Right

• tricuspid valve (3 cusps) or right AV

Left

• bicuspid valve (2 cusps) or left AV or mitral valve

what happens and which valves are open during diastole?

• heart muscle is relaxed and blood fills the heart (both atria and ventricles)

• atrioventricular AV valves open

• semilunar valves closed

what happens and which valves are open during systole?

• heart muscle contracts and blood is pushed out of the heart

• semilunar open

• atrioventricular closed

what is the function of the semilunar valves? and specific names of the left and right one?

function:

• prevent blood that has been pumped out of the heart returning to ventricles again during filling (closed in diastole)

  • pushed open as blood flows out of the heart

  • closes as blood starts to back flow

right side

• pulmonary semilunar valve - 3 cusps

left side

• aortic semilunar valve - 3 cusps

what are the 3 structures involved with systole for AV valve?

1. AV valve leaflet

   • the ‘flap’ parts of the valve - what opens and closes

2. chordae tendineae

   • extensions/fibrous chords attached to the valve leaflet free edge and papillary muscle

3. papillary muscles

   • extension of the myocardial heart wall from ventricle

   • provides tension to stop leaflet from prolapsing into the heart chamber during systole

not needed for semilunar because less pressure

what is the arterial circulation of the heart?

right side

• from aortic valve leads to right coronary artery → right side of the heart

• vessels run over epicardium and only drop deep into the myocardium where blood is needed

left side

• from aortic valve to left coronary artery

• branches → circumflex artery

• branches → anterior interventricular artery

what is the vein circulation of the heart?

right side

• small cardiac vein

left side

• great cardiac vein

→ both meet together at the coronary sinus

what is the total circulation loop of the heart?

[ ]coronary veins → [ ]cardiac vein → coronary sinus

what is the structure of capillaries?

they are in high quantity on the heart

• skinny - only wide enough for one red blood cell at a time to max gas exchange (small lumen)

• there are supplying and draining capillaries in the heart

1. very thin walled

2. large cross sectional area of capillary bed

3. slow and smooth blood flow (opposite to pulsing of heart)

   • due to much larger total area of capillary bed compared to arterioles → slower blood flow

what are the features of cardiac muscle (myocardium/one of 3 types of muscle)

features of both skeletal and smooth + cardiac specific

• function = beating of the heart (high stamina)

cell structure - cardiomyocytes

• striated (but irregular - branched sarcomeres that need to fit around central nucleus)

• short, branched cells

• one (or 2) nuclei per cell

• central and oval shaped nucleus

• cytoplasmic organelles packed at the poles of the nucleus

• mitochondria 20% volume of cell (high energy)

• interconnected with neighbouring cells via intercalated disks ICDs

what are intercalated disks and what are they made up of?

the join between 2 seperate heart muscle cells made but of 3 different cell junctions

1. adhesion belts

   • link actin to actin

   • vertical orientation

2. desmosomes

   • link cytokeratin with cytokeratin

   • so cells dont rip a part if sarcomeres go different directions

   • neither horizontal/verticle

3. gap junctions

   • for electrochemical communication

   • horizontal orientation - as delicate so in opposite orientation to contraction

to join individual cardiac muscle cells to make a ‘mega’ cell

what is the conduction system of the heart?

• its action greatly increases the efficiency of the heart pumping

• this system is responsible for the coordination of heart contraction and of atrioventricular valve action

• autonomic nerves alter the rate of conduction impulse generation

• made of cardiac muscle cells that modified/differentiated into conduction tissue

what is the conduction pathway of the heart

1. sinoatrial (SA) node

2. internodal pathways

3. atrioventricular (AV) node

4. AV bundle

5. left and right bundle branches

6. purkinje fibres (also extend into papillary muscles for pre-tension)

what makes but the cardiac conduction cells?

• some peripheral myofibrils

• central nucleus

• mitochondria

• glycogen

• lots of gap junctions

• some desmosomes and few adhesion belts

forms 1% of all cardiac cells (if dosent get enough O2 then can cause arrhythmias) - not that heart muscle cant contract but cant conduct)

what is the arterial blood supply path down from the belly button down to the feet?

• common illiac artery

• external illiac artery

• fermoral artery

• popliteal artery (posterior to knee)

• posterior tibial artery

• plantar arch

what is the deep and superficial veinous drainage path from feet to belly button

deep

• plantar venous arch

• posterior tibial vein

• popliteal vein (posterior to knee)

• femoral vein

• external illiac vein

• common iliac vein

• inferior vena cava

superficial

• great saphenous vein (longest vein in body- from foot to hip)

• connect w/ deep veins before external iliac vein so can join back with inferior vena cava

what are the 3 layers of the blood vessel?

• tunica intima (innermost)

• tunica media

• tunica adventitia (externa)

what is the tunica intima made up of ?

1. endothelium - a simple squamous epithelium which lines the lumen of all vessels (to prevent blood clotting)

2. sub-endothelium - a sparse pad of loose fibrous connective tissue cushioning/supporting the endothelium

3. internal elastic lamina - condensed sheet of elastic tissue. it is well developed in arteries and less so in veins

   • mostly elastin protein

   • ‘rubber’ built into vessel

   • line where intima stops and media begins

layer as a whole is very thin

what is the tunica media made up of?

• smooth muscle (involuntary/non-striated) - therefore able to contract to control blood flow and pressure

• a variable content of connective tissue fibres - mainly elastin and collagen

• thickness of the media is proportional to both the vessel diameter and blood pressure

  • thicker or higher blood pressure = thicker media

  • thus artery and vein thickness of media is different

thicket layer in artery but not vein

what is the tunica adventitia made up of?

• lots of loose fibrous connective tissue with a high content of collagen and variable amounts of elastin

• in larger vessels, contains the vasa vasorum - the vessels of the vessel

  • smaller blood vessels that supply and drain the media (layer above)

• lymphatics and autonomic nerves are also found in this region

thickest layer of veins

what are the differences between elastic and muscular arteries?

elastic arteries - close to heart

• media has many layers of elastic tissue in between smooth muscle

  • allows rebound with pulsile pressure from heart

muscular arteries - in leg

• little elastic layers, high concentration of smooth muscle

  • able to change diameter of lumen better

this is as capillaries (the bridge between arteries and veins prefer a steady flow the different make ups of the artery are able to buffer the pressure as the vessel become smaller

what is the order of size/flow from artery to vein?

• aorta

• arterors

• arterioles

• capillaries

• venules

• veins

• vena cava

what is the basic function of arterioles ?

• primary site of resistance of circulation

• determine/maintain blood pressure

what is the basic function of capillaries?

• site of gas exchange between blood and tissues

what is the basic function of venules ?

• they are the start of the collecting/draining system

• smalled veins

• have valves to keep blood flow direction on way

what is the basic function of veins?

• low pressure but large volume transport system

• one way flow due to valves

• capacitance vessels

  • can hold additional blood volume if needed

what is the basic structure and 3 layers of veins?

• irregular, flattened shape with huge lumen and thin wall

• has spare capacity to take up extra blood volume → capacitance

same 3 layers as artieries

1. intima

2. media (thinner than in arteries as less layers of smooth muscle - less pressure)

3. adventitia - often thickest layer

   • high collagen for capacitance (collagen amount determines capacitance)

what is varicose vein?

when the valves of veins are leaky

• particularly of the great saphenous vein (superficial)

• will become distended (swollen and longer so bunches up more

what is a general capillary made up of ?

• it is an epithelial cell wrapped around and connected to itself with a cellular junction

  • connects via cellular junctions with other epithelial cells above and below to form a tube

• because its a cell it contains a nucleus and has lumen where (one) RBC sits

what is the pathway of the capillary bed from the terminal arteriole to post capillary venule?

• central vascular shunt

  • contains metarteriole and thoroughfare channel

  • a direct path from supply to drain without passing through capillary bed

• above and below is capillary bed network with access controlled by precapillary sphincters

  • composed of smooth muscle and dial (tone) that can control perfusion into bed

what is the structure of a continuous capillary?

• 8-10 micrometers diameter (fits 1 RBC)

• termed ‘continuous’ because epithelial cell wraps around and is continuous around the whole capillary

• contains intercellular cleft as junction

• has complete basement membrane/basal lamina

• eg skeletal and cardiac muscle

what is the structure of the fenestrated capillary?

similar to continuous but has fenestrations:

• 8-10 micrometer diameter (1 RBC)

• has complete basement membrane/basal lamina

• epithelial cells has fenestrations - small holes that allow exchange and filters blood (cannot fit cells/organelles)

• common in kidney

what is the structure of the sinusoidal capillary?

quite different to the other 2 capillaries:

• bigger - 30-40 micrometer diameter (3ish RBC)

  • not as concerned with gas exchange

• contains intercellular gaps as epithelial cell covering is incomplete (gaps larger than fenestrations but still cannot let out cells)

• incomplete basement membrane - thus cells can have direct contact/exchange with capillary

what are the different ways continuous capillaries can exchange nutrients ?

1. through direct diffusion (through the epithelial cell wall and the basement membrane → to interstitium)

2. diffusion through intercellular cleft (depending on how many cell junctions present)

3. vesicles (transported out)

what are the different ways fenestrated capillaries can exchange nutrients?

1. through endothelial fenestration (pore)

   • still has to diffuse through basement membrane

2. diffusion through pore?

what are the different ways a sinusoidal capillary can exchange nutrients?

1. through endothelial fenestration (pore)

   • direct exit as does not have to diffuse through basement membrane

2. diffusion through pore?

what is the function of the lymph vascular system?

• drains excess tissue fluid and plasma proteins from tissues and returns them to the blood

• filters foreign material from the lymph

• ‘screens’ lymph for foreign antigens and responds by releasing antibodies and activated immune cells

• absorbs fat from intestine and transports it to the blood

• found anywhere in the body where collecting veins are also present

what is the structure of lymphatic vessels?

• begin as large blind ending (cul de sac) capillaries - porous at tip

  • epithelial cells dont form very tight junctions with each other particularly at tip

• from small intestine, special type of lymphatic vessels called lacteals drain fat-laden lymph (white) into collecting vessel, cisterna chyli (upward direction)

  • drains into left subclavian vein

• larger collecting vessels have many bicuspid valves to prevent backflow

• NO RBC

• thin walled

what is the direction of lymph flow in the left side of the face/upper body?

down to up

• lymphatic collecting vessels

• thoracic duct

• entrance of thoracic duct into left subclavian vein

  • lymph drains back into vein

• drains into superior vena cava

what is the direction of lymph flow in the right side of the face/upper body?

down to up

• entrance of thoracic duct into right subclavian vein

  • lymph drains back into vein

• drains into superior vena cava

what is the structure and blood flow and lymph of the small intestine villus?

• oxygenated blood flows into the villis from the intestinal arteries

• deoxygenated blood (but nutrient rich) flows back to the portal vein → then liver for processing

• in between there is the lacteal

  • porous allowing fats to be transported [lymph]

what are the 3 main clusters of regional lymph nodes?

1. cervical nodes (by neck)

2. axillary nodes (armpits)

3. inguinal nodes (groin)

what is the lymph node structure?

• lymph flows in through the afferent lymphatics

  • inside lymph nodes are immune cells suspended on fibres

  • as lymph flows through the cells are able to screen and filter

• lymph/immune cells are then able to leave through the efferent lymphatics toward the subclavian vein

(there is blood vessels in lymph nodes as well)

what is the lymphatic drainage of the breast?

1. lymphatic vessels of the breast

2. axillary lymph nodes

3. right lymphatic duct

   • all above are lymphatics

4. right subclavian vein (blood vessel)

important because breast tissue lymphatic drainage can carry cancer cells into the blood vascular system leading to metastatic cancer.

how does the heart work as 2 pumps but one unit/in series?

2 pumps

• systemic circuit for the body (left pump)

• pulmonary circuit to oxygenate the blood (right pump)

(thus important to remember, A=arteries=away from heart - not oxygenated blood as rule does not always apply)

there is an equal flow of blood through the two circuits

which chamber of the heart pumps first?

atria, then ventricles (valves open and close to direct blood)

what are the important things to know about heart muscle for jeff?

1. actin and myosin make up sarcomeres which are the individual contractile units

2. cross bridges cannot form without Ca2+ and there is no recruitment in heart muscle - every muscle cell in the heart contracts with each heart beat

   • this means the only way to control how strong the heart beats is through regulating the amount of Ca2+ that is released

   • this is because Ca2+ increased the amount of cross bridges form thus more tension/force of contraction

   • (technically all cross bridges release when atp binds but realistically no time so all about Ca2+

what is the difference between diastole and systole?

diastole

• = relaxation and falling pressure

systole (action)

• = contraction and rising pressure

[describes conditions of the heart but different parts of the heart are in different phases at same time

what are the main phases of the cardiac cycle?

1. atrial systole

   • atrium is filled will blood and muscle contracts

   • ‘lubb’ sound heard as AV valve slams shut

   • ventricles are in diastole

2. isovolumetric ventricular contraction and 3. ventricular ejection

   • first pressure builds in ventricles, then blood ejected into artery

   • ‘dupp’ sound heard as aortic and pulmonary valves slam shut

   • ventricles is systole and atrium in diastole

4. isovolumetric ventricular relaxation and 5. passive filling (longest phase)

   • heart is relaxed/expanding and this released pressure

   • AV valves are open and blood fills atrium ready to repeat cycle

   • both in diastole

what are the 4 features of a blood pressure trace?

1. pulsatile change in pressure in the major arteries linked to ejection of blood (and graph seen on trace)

   • periods of systole - rising pressure and diastole - falling pressure

   • systolic pressure = highest point on trace

   • diastolic pressure = lowest point on trace

2. diastole is typically longer than systole thus mean pressure will be slightly lower than the middle (calculated as an average over time)

3. pulse pressure however, is systole-diastole

4. systemic arterial pressure is always higher than pulmonary pressure (as less of a distance for blood to travel)

   • seen as 2 traces, one directly on top of the other

what does hyper and hypotension mean and which one is generally worse?

hypertension = high blood pressure

hypotension = low blood pressure

hypotension often worse because blood cannot get around your body

what are the main differences between contractile and electrical cells of the heart?

• contractile makes up 99% of the heart cells, electrical makes up 1%

• contractile cells have striated appearance and high concentration of actin and myosin

  • electrical cells have ‘pale’ striated appearance and low actin and myosin present (less resistance for signal)

how does electrical signal to tell the heart to beat begin and travel to the different cells?

• depolarisation starts at the sinoatrial node (SAN)

• the signal spreads to neighbouring cells through intercalated disks and gap junctions

  • pores with low resistance to ionic current

  • allow current flow between adjacent cells

  • impulse spread along conduction pathway, between electrical and contractile cells, and between just contractile cells

    • causes increased speed of the impulse throughout the heart, millions of cardiac cells to behave as one → a functional syncytium

• in contractile cell, increased cytosolic Ca2+ levels, cross bridge attachment and contraction

what is the electrical wiring pathway of the heart/conduction pathway?

1. begins at sinoatrial (SA) node and through interatrial bundle and fibres, sends signal to…

2. Right atrium, left atrium (both signalled to contract), and atrioventricular (AV) node

3. AV node holds the signal and only released it when the atria have finished contracting

4. the signal then travels to the right and left AV bundles (sends signal to septum) which both split via subendocardial branches to become purkinje fibres

5. the purkinje fibres send signal to the lateral wall, where it wraps under the heart and extends upwards again

   • this is done to generate max force and push out as much blood in one beat as possible

what is the de/repolarisation cycle of the heart?

[quiescence = no change in electrical signal; relaxed]

1. quiescence ends when excitation spreads from the SA nodes (top of atria depolarises/contracts)

2. the atria are fully depolarised and contract)

3. atria repolaraise and relax, while AV node sends excitation to ventricles

4. ventricles fully depolarised and contract

5. ventricles begin to repolarise and relax (begins at apex/bottom)

6. ventricles fully repolarised and relaxed, the heart is back to quiescence - passive filling, ready for cycle to repeat

what are the key phases of an ECG you need to know?

1. atrial depolarisation, initiated by the SA node, causes the P wave (first bump)

2. with atrial depolarisation complete, the impulse is delayed at the AV node (short return to base line)

3. ventricular depolarisation begins at apex, causing the QRS complex, atrial repolarisation occurs. (sharp spike because large change in electrical frequency of the ventricles in short period of time - small atrial changes drowned)

4. ventricular depolarisation is complete (short return back to base line)

5. ventricular repolarisation begins at apex, causing the T wave (small wave at end)

6. ventricular repolarization is complete (back to base line)