HUBS192 - lectures 4-13 - CARDIOVASCULAR

Describe the blood vascular system?

a closed supply and drainage system - a continuous loop

Describe the lymphatic (vascular) system

an open entry drainage system - one way system

What are the 3 general principles of organisation of the cardiovascular system? Describe them

1. supply side

   • arteries are the only supply path

   • major arteries are situated to avoid damage

   • important structures often receive supply from 2 sources

   • arteries change their name at each major branch

2. exchange network

   • capillaries of varying degrees of permeability - continuous (tight), fenestrated (leaky), sinusoidal (very leaky)

3. Drainage

   • deep veins

   • superficial veins

   • lymphatics

Where is the apex located on a human body and what is the apex also known as?

Located at midclavicular line and between 5 and 6 ribs

AKA point of maximal impulse

What does the right atrium receive? What type of blood does it carry?

• superior vena cava

• inferior vena cava

• coronary sinus

• (deoxygenated blood)

what does the left atrium receive? What type of blood does it carry?

four pulmonary veins (oxygenated blood)

What are the 4 layers of the heart wall? What do each of them mean?

• endocardium - within

• myocardium - muscle

• epicardium - upon

• pericardium - around

what is myocardium AKA?

the pumping chamber

How thick is the left and right ventricle of myocardium?

left = 1.5cm

right = 0.5cm

where does the heart sit?

pericardial space

What are the 3 layers of pericardium? From the outermost layer to the innermost layer

• Parietal pericardium

• pericardial fluid

• visceral pericardium

Name all the layers that make up the heart wall

• fibrous pericardium

• parietal layer of serous pericardium

• pericardial cavity

• epicardium - the visceral serous pericardium, lose irregular FCT, blood vessels

• myocardium

• endocardium

What are the left and right atrioventricular (AV) valves called and what is their function?

Left - bicuspid (mitral) valve

Right - tricuspid valve

Prevent blood returning to atria during ventricular contraction

What are the left and right semilunar valves called and what are their functions?

Left - Aoritc valve, 3 cusps

Right - pulmonary valve, 3 cusps

Prevent blood returning to ventricles during filling (diastole)

When are the semilunar valves open and closed?

open = as blood flows out of heart

closed = as blood starts to backflow

What is the function of cardiac muscle?

beating of the heart

Describe the structure of Cardiac muscle cell

• striated

• branched, short

• one or 2 nuclei

• oval shaped nucleus

• connected with neighbouring cells by ICD

What are electrical conduction pathways made of?

non contractile cardiac muscle

What are the 3 layers that make up blood vessels? What are each of these layers made of?

1. tunica intima - endothelium, sub-endothelium, internal elastic lamina

2. tunica media - smooth muscle, connective tissues = elastin and collagen

3. tunica adventitia (external) - loose FCT, vasa vasorum, lymphatics and autonomic nerves

What is the function of an arteriole?

determine blood pressure

What is the function of capillaries?

site of exchnage between blood and tissues

What do veins have to ensure arteries can only go in one direction?

valves

What are the functions of veins?

• large volume transport system

• one way flow

• capacitance vessels

What are precapillary sphincters composed of?

smooth muscle cells

How big is a continuous capillary? what structures is it made of?

8-10um diameter

basement membrane, endothelial layer, intercellular cleft

How big is a fenestrated capillary? what structures is it made of?

8-10um diameter

fenestrations

How big is a sinusoidal capillary? what structures is it made of?

30-40um diameter

intercellualr gap, incomplete basement mebrane

What are the functions of the lymph vascular system?

1. drains excess tissue fluid and plasma proteins from tissues and returns it to the blood

2. filters foreign material from lymph

3. screens lymph for foreign antigens and responds by relasing antibodies

4. absorbs fat and transports to blood

What are lacteals?

a group of lympatic vessels that drain fat into a collecting vessel called cisterna chyli

What do lymph vessels not have?

red blood cells

What type of blood flow moves to the heart and away from the heart?

away - arterial

towards - venous

Does the atria or ventricles contract first?

Atria

Describe the cellular mechanism of cardiac contraction

• Ca levels go up and more Ca is released from the SR

• myosin binds to actin to form cross bridges

• myosin pulls on actin to shorten the sacromere and generate force

How can you increase force of cardiac contraction?

• every cardiomyocyte is activated during contraction

• increase cytosolic Ca levels

• increase number of cross bridges formed

Describe the cellular mechanism of cardiac relaxation

• decrease in Ca2+ levels = Ca is pumped back into SR

• cross bridges release when ATP binds to mysoin

• reduction in force means the heart can relax

What is diastole?

relaxation, falling pressure

What is systole?

contraction and rising pressue

What is pulse pressure?

difference between the highest and lowest points

Does the heart spend more time in systole or diastole?

diastole

is systemic or pulmonary pressure higher?

systemic

What is the main difference between electrical and contractile cells of the heart?

electrical = low actin and myosin

contractile = high actin and myosin

where does depolarisation start?

in the sinoatrial node

What are gap junctions?

• pores with low resistance to ionic current

• allow current flow between adjacent cells

What is a ECG? and what does it do?

electrocardiogram - line between two surface electrodes that detect a difference between electrodes

• records depolarisation and repolarisation of cardiac cells

What does P wave control?

atrial depolarisation

what does QRS complex control?

ventricular depolarisation

What does T wave control?

ventricular repolarisation

Blood pressure is very low where?

in the veins

What is the equation for flow?

pressure difference/ resistance

What is the equation for mean arterial pressure?

Cardiac output x total peripheral resistance

During the “blood flows in” stage what is happening?

• fills arteries

• increases arterial blood volume

• raises arterial pressure

During the “blood flows out” stage what is happening?

• drains arteries

• decreases arterial blood volume

• lowers arterial pressure

How is cardiac output calculated?

stroke volume x heart rate (SV x HR)

What are baroreceptors? where are they located?

blood pressure sensors

carotid sinus and aortic arch

What is the difference between sympathetic and parasympathetic signalling? Where does the pathway cross through for both?

sympathetic = increases heart rate and force of contraction and increases stroke volume (vagus nerve)

parasympathetic = decreases heart rate (sympathetic trunk ganglion)

Why is there a parallel design of systemic ciruclation?

reduces resistance and decide how much blood flow.

During exercise where does blood flow increase?

• muscle

• heart

• skin

During exercise where does blood flow decrease? where does blood flow stay constant?

• GI tract

• kidneys

brain

in individual circulations in muscle and kidneys describe the flow rate and resistance rate

muscle - increased flow = decreased resistance

kidneys - decreased flow = increased resistance

What is the resistance equation to blood flow and vessel radius?

R= 1/r4 = 1/(0.5d)4

What has a huge effect on flow?

radius of the vessel lumen

Where is blood mainly found?

in the systemic veins

What is the total blood volume in a 70kg human?

5Litres

thin walls =

more compliance

what is compliance? what is the equation for compliance?

the extent to which a vessel allows deformation in response to an applied force

difference Volume/ Difference Pressure

Which one is bigger… arterial volume or venous volume?

venous volume

What structures counteract with pooling? and what do they do?

venous valves - prevent backflow of blood

skeletal muscle - stiffens veins making them less compliant and therefore less prone to pooling.

What is starlings law fo the heart?

The more stretched muscle fibres are before a contraction, the stronger the contraction will be

Increased venous retun =

increased stroke volume

What are the 3 functions of blood? describe them in detail

• transport - o2, co2, nutrients, waste, heat, hormones, immune cells

• immune response - white blood cells, immunoglobulins

• coagulation - platelets, coagulation factors in plasma

What 3 things is plasma made of?

1. plasma proteins

2. other solutes

3. water

What 3 things are formed elements made of? describe each of them

1. platelets - stop bleeding

2. white blood cells - immune response and defence mechanism

3. red blood cells - transport oxygen

What is haematopoiesis? where is it initiated?

formation of blood cells. In red bone marrow which contains stem cells

What is the structure of red blood cells?

biconcave disc shape - large surface area and movement through capillaries

What are the 4 characterisitcs of RBCs?

1. contain large amount of haemoglobin

2. one third weight of RBC

3. Uses iron as part of the haem structures to bind oxygen

4. 4 haem units, so each haemoglobin can bind four oxygen molecules

What is packed cell volume (PCV)?

the fraction of blood occupied by the red cells

What does low haemoglobin levels = _____ and how does this happen?

anaemia

• blood carried less O2 - reduces amoutn delivered to tissues

What is RBC production stimulated by?

Erythropoietin (EPO)

How does the process of erythropoiesis work?

• low levels of oxygen in blood

• kidneys sense that the oxygen levels in blood are low

• kidneys release EPO

• EPO circulates to bone marrow

• stimulates the production of more RBCs - which carry more O2