The Heart

Give the function of:

• The heart

• Arteries

• Veins

• Capillaries

• Blood

• Lymphatic system

• Heart: mechanical pump

• Arteries: transporting blood away from the heart

• Veins: transporting blood to the heart

• Capillaries: site of exchange of substances

• Blood: transport of cellular components and dissolved substances

• Lymphatic system: returning tissue fluid to systemic circulation

Draw out the circulatory system of fish

Draw out the circulatory system of amphibians

Draw out the circulatory system of mammals

What is the structure/function of:

• Muscular arteries

• Elastic arteries

• Arterioles

• Capillaries

Muscular arteries: medium sized artery, changes (vasodilation/constriction) affect blood pressure

Elastic arteries: conducting artery, expands during systole and recoils during diastole

Arterioles: small diameter which changes in response to local conditions

Capillaries: small diameter, endothelial layer only, site of exchange of substances

Describe the structure of:

• Tunica interna

• Tunica media

• Tunica externa

• Lumen

Tunica interna: endothelial lining

Tunica media: concentric sheets of smooth muscle

Tunica externa: connective sheath around a vessel

Lumen: cavity of an organ

Draw a labelled diagram of the heart

Where are the 4 different heart valves located?

Tricuspid: right atrioventricular

Mitral: left atrioventricular 

Pulmonic: right semilunar

Aortic: left semilunar

Describe the different stages of the cardiac cycle

1. Ventricles fill with blood, atria contract- forcing more blood into ventricles

2. Ventricles contract, increasing the ventricular pressure

3. When the ventricular pressure increases above arterial pressure, the atrioventricular valve closes

4. When the pressure inside the ventricles exceeds the pressure in the outgoing arteries, the semilunar valves open

5. As a result of ventricular systole and opening of the semilunar valves, blood flows from the ventricles to the arteries

6. Pressure in the ventricles drops below aortic pressure and the semilunar valves close

7. When ventricular pressure becomes lower than atrial pressure, the atrioventricular valves open

Draw the pathway of nerve fibres from the central nervous system to:

• Skeletal muscle (SMNS)

• Smooth muscle, heart muscle, glands (SNS)

• Smooth muscle, heart muscle, glands, reticular formation (SNS)

• Smooth muscle, heart muscle, glands (PNS)

Include relevant synapses and the neurotransmitters

What are the neurotransmitters, designation and receptors associated with the following nerve fibres?

• Pre-G SNS

• Pre-G PSNS

• Post-G SNS

• Adrenal medulla

• Post-G PSNS

Nerve fibre	Neurotransmitter	Designation	Receptor
Pre-G SNS	Acetylcholine	Cholinergic	Nicotinic Ach R
Pre-G PSNS	Acetylcholine	Cholinergic	Nicotinic Ach R
Post-G SNS	Noradrenaline	Adrenergic	Ɑ and/or β
Adrenal medulla	Adrenaline	Adrenergic	Ɑ and/or β
Post-G PSNS	Acetylcholine	Cholinergic	Muscanaric Ach R

When and why is the SNS activated?

The SNS is activated during times of stress, physical activity or danger to trigger the ‘fight or flight’ response

When and why is the PNS activated?

The PNS is activated when the body is at rest, safe and recovering to trigger the ‘rest and digest’ response

Describe the outflow of the SNS

The SNS has a thoracolumbar outflow. The preganglionic neurons originate from the thoracic (T1) and lumbar (L2/3) segments of the spinal cord

Describe the length of ganglionic fibres in the SNS

Preganglionic fibres are short in length

Postganglionic fibres are long in length

Give the locations of the SNS ganglia

Paravertebral ganglia 

• Cranial cervical ganglion

• Middle cervical ganglion

• Caudal cervical ganglion

• Thoracic and lumbar ganglia 

• Sacral and pelvic ganglia

Prevertebral ganglia

• Celiac ganglion

• Superior and inferior mesenteric ganglia

List the effects of the SNS on various parts of the body

Eye: pupil dilation

Salivary glands: viscous secretion

Heart: increased heart rate, increased force of contraction

Lungs: dilation of bronchioles

Upper digestive tract: motility reduction

Digestive glands: reduced secretion

Liver: increased release of glucose to the blood 

Adrenal medulla: increased secretion

Lower digestive tract: reduced motility

Urinary bladder: relaxation of wall musculature, contraction of sphincter muscle 

Genitals: ejaculation (male)

Blood vessels/sweat glands: vasoconstriction, increased sweat secretion

Describe the outflow of the PNS

The PNS is activated when the body is at rest, safe and recovering to trigger the ‘rest and digest’ response

The PNS originates in the brainstem, and travels through four cranial nerves: 

1. CN III- Oculomotor 

2. CN VII- Facial

3. CN IX- Glossopharyngeal

4. CN X- Vagus 

The sacral outflow originates from spinal segments S2-S4 via pelvic splanchnic nerves to supply the lower bowel, bladder and reproductive organs

Describe the length of ganglionic fibres in the PNS

Preganglionic fibres are long in length

Postganglionic fibres are short in length

Give the locations of the PNS ganglia

Sensory ganglia

• Dorsal root ganglia

• Cranial nerve ganglia

Autonomic ganglia

• Sympathetic ganglia

• Parasympathetic ganglia

Describe how autonomic reflexes are involved in neural regulation of the ANS, giving examples

These work through feedback mechanisms, which involve the afferent nervous system

Their main function is to maintain homeostasis

Examples

1. Heart rate (controls speed, manages blood flow)

2. Digestion (moves food, releases stomach acid and enzymes)

3. Breathing rate (adjusts air flow, responds to gas levels)

4. Pupil size (dilation in low light, constriction in bright light)

Give the function and locations of baroreceptors

Baroreceptors detect changes in blood pressure by sensing the stretch of blood vessel walls

Location

• Walls of the atria

• Walls of pulmonary vessels

Give the function and locations of chemoreceptors

Chemoreceptors monitor chemical levels (oxygen, carbon dioxide, pH) in the blood and brain

Location

• Medulla oblongata

• Carotid bodies and aortic bodies

How is the SNS involved in innervating the heart and lungs?

Post-G fibres go directly to the heart. The sympathetic cardiac nerves are found within the cardiac plexus

Post-G fibres go to the SA node and AV node (in the walls of the heart)- this controls heart rate and rhythm

Post-G fibres also go to the myocardium- this controls the force of contraction 

Lungs

• β-2 adrenergic receptors are stimulated to relax the smooth muscle of the airway

How is the PNS involved in innervating the heart and lungs?

Pre-G fibres travel in branches of the recurrent laryngeal and vagal nerves to the cardiac plexus

The post-G fibres end in the atrial walls

Lungs

• M3 muscarinic receptors are stimulated to constrict the smooth muscle of the airway

What is the difference between the ‘lub’ and ‘dub’ sound of the heart?

‘Lub’ (S1)

• Heard at the beginning of ventricular systole, when the atrioventricular valves shut 

‘Dub’ (S2)

• Heard at the beginning of ventricular diastole, when the semilunar valves shut

What is the difference between systolic and diastolic murmurs in the heart?

Systolic murmurs

• Swishing sounds 

• Heard between S1 and S2 during ventricular contraction

Diastolic murmurs

• Sounds heard after S2 and before S1

How can acquired heart disease cause heart murmurs?

• Thickening and weakening of heart valve can cause leakage, causing backflow turbulence (common in older, small-breed dogs)

• Diseases that weaken or thicken heart muscle alter chamber size/function, disrupting normal blood flow

• Bacterial infections can cause inflammation and growths on the heart valves, preventing proper closure

How can congenital heart defects cause heart murmurs?

• Shunts and holes: abnormal openings between heart chambers force blood where it should not go

• Stenosis: narrowing of the valves/major arteries forces blood through tight spaces at high speed

What are the functional causes of heart murmurs?

• Fever, stress and pregnancy increase metabolic rate which increases blood flow velocity- temporarily producing a functional murmur 

• Anaemia/low protein can create physical turbulence

• Harmless heart murmurs are common in rapidly growing animals, or athletic animals- these disappear with maturity

Describe the structure and function of the annulus fibrosus

The annulus fibrosus consists of 4 interconnected rings of fibrous tissue, situated between the atria and the ventricles 

It acts as an electrical insulator, ensuring action potentials from the sinoatrial node only reach the ventricles via the atrioventricular node

This helps ventricular filling to be complete before the initiation of ventricular systole

Give the function of:

• The SA node

• The AV node

• The bundle of His

• Purkinje fibres

Sinoatrial node: generates electrical impulses that spread through the heart muscle, setting the normal resting heart rhythm, and causing the atria to contract (acts as the natural pacemaker)

Atrioventricular node: delays electrical signals from the SA node, ensuring the atria empty blood into the ventricles before the ventricles contract

Bundle of His: carries electrical signals from the AV node down to the apex

Purkinje fibres: rapidly spread signals from the bundle of His through the ventricular walls, causing the ventricles to contract

Draw a diagram to show the conduction system of the heart

Describe the different phases of conduction in the heart, including a relevant diagram

Phase 0

• A stimulus opens voltage gated sodium ion channels

• This causes an influx of sodium ions

• Membrane voltage sharply increases

Phase 1

• Sodium ion channels close

• Outward potassium ion channels open briefly, causing a small outflow of potassium ions

• This causes a minor decrease in voltage 

Phase 2

• Calcium ion channels open

• Calcium ions enter the cells whilst potassium ions continue to leak out

• This holds the voltage steady

Phase 3

• Calcium ion channels close 

• Outward potassium ion channels remain open

• This drives the membrane potential back to baseline resting levels

Phase 4

• The membrane potential remains stable near -90mV

• Inward potassium ion channels stay open

Describe how the action potential is generated in the heart

The SA node, AV node, bundle of His and Purkinje fibres are autorhythmic cells

These spontaneously generate action potentials and undergo slow depolarisation until a threshold potential is reached

These depolarisations occur most rapidly in the SA node- which therefore drives the rhythm of the heart

Action potential at the SA node

1. Ion channels that are permeable to both sodium and potassium ions open, causing a small influx of sodium ions- this is known as I𝑓 current 

2. Calcium ion channels begin to open

3. Further calcium ion channels open

4. Potassium ion channels are activated, allowing an efflux of potassium ions

5. Potassium ion channels close and I𝑓 channels open

Describe the effects of the SNS on the conduction system of the heart

• SA node: speeds up the rate of pacemaker firing (positive chronotropy)

• AV node: shortens the delay between atrial and ventricular contraction (positive dromotropy)

• Mechanism: noradrenaline binds to beta-1 adrenergic receptors, increasing calcium/sodium entry

• Increases heart rate, speeds up electrical conduction, increases strength of contraction and quickens muscle relaxation

• Stimulates cardiac myocytes

Describe the effects of the PNS on the conduction system of the heart

• SA node: slows down the rate of pacemaker firing (negative chronotropy)

• AV node: lengthens the delay between atrial and ventricular contraction (negative dromotropy)

• Mechanism: acetylcholine binds to M2 muscarinic receptors, opening potassium channels to hyperpolarise the cells

• Has very little direct influence on ventricular muscle cells, because vagal nerve fibres are heavily concentrated in the atria and pacemakers- with very little distribution in the ventricular walls

Draw a diagram to show the conduction of the action potential in both the SA and AV nodes

Draw a diagram to show a summary of cardiac excitation throughout the heart and the relevant structures related to each stage of conduction

Describe the structure of the heart, including the locations of the 4 valves

The heart is a simple pump consisting of 4 chambers: 2 atria and 2 ventricles 

It has 4 valves- ensuring blood flows unilaterally

AV valves separate the atrium and ventricles

• Mitral valve on the left

• Tricuspid valve on the right

SL valves separate the ventricles from the aortic and pulmonary arteries

• Aortic valve in the left outflow tract 

• Pulmonic valve in the right outflow tract

Label an echocardiogram of the heart

Describe the key functions of the cardiorespiratory system

Transport to and from metabolising tissue

• Oxygen and carbon dioxide 

• Nutrients 

• Waste 

• Heat 

• Hormones

Homeostasis

• pH, osmolarity, electrolytes 

• Infection

Other

• Generating pressure (e.g renal filtration)

Describe the basics of clinical relevance in relation to the heart

Heart disease is common in both small animal and equine practice

Disease usually involves valve degeneration

Acquired heart disease: valves becoming incompetent, diseases of the heart muscle (resulting in the heart not contracting well, or not filling well)

• Disease can also result from issues during the development of the heart (congenital heart defects)

Heart disease does not always result in heart failure

• Heart failure: a syndrome in which the heart fails to deliver blood effectively to meet the requirements of metabolising tissues

Describe the structure of the circulatory system of mammals

What is the difference between ventricular systole and ventricular diastole?

Ventricular systole: contraction of ventricles 

• Results in cardiac output 

• AV valves close

• ‘Lub’ sound 

Ventricular diastole: relaxation of ventricles

• Results in ventricular filling

• SL valves close

• ‘Dub’ sound

Describe the considerations of regulation of cardiac function

• Can change heart rate and contractility

• Electrical activity (electrophysiology)- can assess using and ECG

• Contractile function control

• The important role of the ANS

• Hormonal mechanisms (local and systemic)

Describe the considerations of regulation of vasculature

• Autoregulation: local blood flow regulation, intrinsic ability of an organ to maintain a constant blood flow, despite changes in perfusion pressure

• The important role of the ANS

• Hormonal mechanisms (local and systemic)

What are the considerations for the heart to act as a pump? Include definitions

• Cardiac output: volume delivered into the circulation per minute

• Stroke volume: volume delivered by the ventricle per beat

• Other pumping mechanisms (venous)

• And what control these

What are the considerations for the distribution of blood?

• Vascular constriction and dilation (arteries and veins)

• The maintenance of unidirectional flow in vital organs

• Cardiac valves

• Vascular valves

Draw a graph to (roughly) show the percent of cardiac output vs the weight of the following organs:

• Lungs

• Bones

• Skin

• Digestive tract

• Liver

• Brain

• Skeletal muscles

• Heart

• Kidneys

Describe venous return to the heart, including important controlling factors

Deoxygenated blood is returned to the heart

Diastolic cardiac volume is important for cardiac output

Important controlling factors

• SNS

• Blood volume

• Muscle (respiratory) pump

Describe the key components of the vascular system, including a diagram to show various structures

Arteries: from the heart

Capillaries: site of diffusion

Portal veins: between 2 capillary beds

Veins: return to the heart

Describe the differences of the cardiac system of birds

Birds have a highly efficient cardiovascular system

• To cope with high metabolic demands 

• Important for oxygen delivery and thermoregulation

Main features of the avian CVS

• 4-chambered heart, similar to mammals

• AV valves are different in structure compared to mammals

• The heart is located within the cranial ventral coelom, and is surrounded by air sacs

• The term coelom is used because birds do not have a diaphragm

Avian cardiac function

• Birds have a relatively high cardiac output (195ml/min)

• They can increase cardiac output to over 1 litre/min

  • During exercise

  • Mainly by increasing heart rate (115-670bpm)

• Heart size fluctuates (increases prior to migration in migratory species)

Ventricles

• The left sided ventricular wall is 3x thicker than the right

• These empty almost completely on each cardiac cycle 

• Low end-systolic volume

Describe the structure and function of the renal portal system (including a diagram)

Present in reptiles, birds, amphibians and most fish

Receives blood from the caudal body, and returns it to the heart via the kidneys

It functions to supply blood to renal tubules at all times

• Portal blood flow is regulated by the renal portal valve

This is important, as it alters how drugs will act

• If injected in the caudal half of the body, it may be metabolised before entering general circulation

What is ontology?

Ontology: the development of the embryo from fertilisation to gestation/hatching

Describe the theory of recapitulation

The stages that the mammalian heart goes through during embryological development are evident in the CV systems of fish, amphibians and reptiles

• Theory of recapitulation

• Embryological parallelism 

• ‘Ontogeny recapitulates phylogeny’

What are the 5 zones of the primitive heart tube? Label a diagram to show these

1. Arterial trunk/ truncus arteriosus 

2. Ventricle 

3. Primitive ventricle 

4. Atrium

5. Sinus venosus

Describe the cardiovascular system of fish

Fish have a simple cardiovascular system

2 chambers to the heart

Blood flows in one direction effectively through a single atrium and ventricle 

Vascular includes to accommodate oxygenation

The heart is often positioned ventral and caudal to the gills

Describe the cardiovascular system of amphibians, including a labelled diagram

In anurans, we start to see 2 atria (3 chambers in total)

Oxygenation occurs from lungs, skin and buccan cavity- hence vasculature is more complex in comparison to mammals

The heart is mid-cranial coelom

Like birds, they have no diaphragm (hence the herm coelom again)

Describe the cardiovascular system of reptiles

Most reptiles have 3 chambers, with 2 atria and 1 ventricle. The ventricle is split into three sections by folds in the muscle wall

Crocodiles are an exception with 4 chambers, but they still have distinct differences from mammals (e.g 2x aortas)

All reptiles can shunt blood away from the respiratory tract when needed

For most species, the heart is mid-cranial coelom, some are very cranial 

For snakes, the heart is often found in the cranial third of the body

What are the functions and pressures of the left and right side of the heart in mammals? Draw a diagram to show the two pumps in series

The right heart:

• Pumps blood without oxygen to the lungs

• Low pressure needed

The left heart:

• Pumps blood with oxygen to all the organs

• High pressure needed

Draw a diagram to show the relevant landmarks close to the heart in dogs

Ventral border of the lungs

Cardiac notch

Lungs (laterally)

Thymus (cranially)

Diaphragm (caudally)

What does this radiograph show?

The heart (dog)

What does this radiograph show?

The heart (dog)

Describe the pericardium, including a diagram

Sac surrounding the heart

Inner visceral layer: on the surface of the heart

Outer parietal layer

No significant lumen

Label this diagram to show the relevant structures of the right atrium of the heart, including their functions

Describe the structure and location of the left atrium

• Dorsal and caudal under the tracheal bifurcation

• Pulmonary veins enter in groups, into 2 or 3 sites

• In the septal wall is the scar of the valve of foramen ovale

Describe the structure and location of the right ventricle

• Crescent shaped in section

• Wraps around the left ventricle cranial and to the right

• Pulmonary artery is cranial and left of the aorta 

• Trabecular septomarginalis

  • Septum- outer wall

Describe the structure and location of the left ventricle

• Circular in section

• Occupies all of the apex

• Prominent papillary muscles 

• Aorta is central

What does this echocardiogram show?

Left ventricle

Describe the different types of cardiac valves

AV

• Right AV: tricuspid (3 cusps in people, 2 in domestic species)

• Left AV: mitral (2 cusps)

• Chordae tendinae- papillary muscles

SL

• Right SL: pulmonic 

• Left SL: aortic 

• Both are 3 cusps

Describe the pressure changes in the heart in relation to the heart valves

1. As ventricles relax, pressure drops below that in atria (blood moves from atria → ventricle)

2. Ventricles contract, ventricular pressure rises and AV valves close

3. When pressure in the ventricles exceeds that of the aorta and pulmonary artery, the SL valves open (ejection phase)

4. Pressure in the ventricles falls: lower pressure in the aorta and pulmonary artery 

5. All four valves are closed, and the cycle starts again

What is the function of the fibrous cardiac skeleton?

Supports the four valves

Separates atria and ventricles

These are known as ossa cordis

Draw a diagram to show a cross-section of the heart

What are the different layers of myocardium?

Label the following diagram (there are three labels- one at the bottom)

Describe the structure of cardiomyocytes, including the specialised structures relevant

Large, cylindrical cells

Striated like skeletal muscle 

Short, branches fibres

Lots of mitochondria

Intercalated discs: support cell-to-cell communication, required for coordinated muscle contraction

Purkinje fibres: specialised conducting tissue, deliver electrical activity to myocardium

How do cardiomyocytes respond to training and injury?

Training

• Mass increase (training/overload) can lead to myocyte hypertrophy

• No increase in cell numbers

Injury 

• Limited capacity to divide/regenerate 

• Undergo regulated cell death

• Release damage signals, which trigger acute inflammation 

• Prompt neighboring non-myocyte cells to form a structural fibrotic scar

What is the difference between ventrodorsal and dorsoventral radiographs?

Ventrodorsal: animal is on its back

Dorsoventral: animal is on its chest

Why are ventricular sounds louder?

Ventricular sounds are louder, as the ventricles are bigger

Draw a detailed diagram to show pressure and volume changes throughout a cardiac cycle, including a representative phonocardiogram and an electrocardiogram

What can affect filling of the ventricles?

Preload

Afterload

If the cardiac cycle is 1 second, how long would systole and diastole be?

If the cardiac cycle is 1 second, 

• Systole= 0.35 seconds

• Diastole= 0.65 seconds

Give a brief outline of the following phases

1. Filling phase (diastole)

2. Isovolumetric contraction

3. Outflow phase (systole)

4. Isovolumetric relaxation

Filling phase (diastole)

• Ventricles fill

Isovolumetric contraction phase

• Ventricles contract, but volume remains constant because the heart valves are closed- pressure builds

Outflow phase (systole)

• Ventricles contract, valves open and blood flows into the aorta or pulmonary artery

Isovolumetric relaxation

• Ventricles relax- ready for refill of blood during the next filling phase

Describe the atrial systole phase of the cardiac cycle

• Last phase of diastole (P → R wave)

• Depolarisation of the atria leads to atrial contraction 

• A tiny amount of ‘topping off’ completely fills the ventricle

Describe the isovolumetric contraction phase of the cardiac cycle

• First phase of systole 

• Begins at the peak of the R-wave

• No real change in the volume of the ventricles 

• First heart sound (‘lub’), closing of the AV valves, associated blood turbulence when ventricular pressure exceeds atrial pressure

Describe the rapid ejection phase of the cardiac cycle

• During ST segment

• When ventricular pressure exceeds that in the aorta or pulmonary artery, semilunar valves open and rapid ejection from the ventricles starts 

• ‘C’ wave in the atrial pressure curve is caused by slight (due to papillary muscles) distension of the AV valves into the atria- normally not measurable

Describe the reduced ejection phase of the cardiac cycle

• Final phase of systole

• Coincides with the T-wave (ventricular repolarisation)

• Blood flow out of the ventricles continues, but more slowly

• Eventually pressure in the ventricle falls below that in the artery, and semilunar valves close

Describe the isovolumetric relaxation phase of the cardiac cycle

• First phase of diastole

• Atria have been filling with blood, and atrial pressure has been gradually rising

• Blood flow out of the ventricles stop (ventricles are sufficiently empty)

• 2nd heart sound ‘dub’ occurs when the semilunar valves close

Describe the rapid ventricular filling phase of the cardiac cycle

• When ventricular pressure falls below atrial pressure, the atrioventricular valves open

• This allows blood to flow from the atria into the ventricles 

• Sometimes a sound may be heard (indicative of a congestive heart failure- atrial pressure too high)

Describe the venous pulse, and the structure of the waveform

The venous pulse reflects the dynamic changes in pressure and volume in the heart’s right atrium, and its interaction with venous return 

Changes in arterial pressure as a result of the cardiac cycle can be reflected in local veins. Clinicians may therefore be able to feel these waveforms as a venous pulse

The venous pulse waveform typically consists of three positive waves (a, c and v wave) and three descents (x, x’ and y descent)- each linked to specific phases of the cardiac function

A wave: atrial contraction 

C wave: tricuspid valve bulging 

X descent: atrial relaxation

X’ descent: ventricular systole

V wave: atrial filling

Y descent: ventricular filling

What are the changes when venous return is increased and decreased?

• Increased venous return elevates right atrial pressure, and can exaggerate waveforms 

• Decreased venous return diminishes the magnitude of the pulses

What can you use the ventricular PV loop for? Draw an associated diagram

The ventricular PV loop graphically represents the relationship between pressure and volume in the left ventricle during a single cardiac cycle

This loop is instrumental in understanding cardiac mechanics, as it delineates the phases of ventricular filling, isovolumetric contraction, ejection and isovolumetric relaxation

What are the fundamental units of measurement?

1. Length: metre (m)

2. Mass: gram (g)

3. Volume: litre (L)

How do you convert to:

• Milli

• Micro

• Nano

• Pico

• Kilo

Milli (m): 10⁻³

Micro (µ): 10⁻⁶

Nano (n): 10⁻⁹

Pico (p): 10⁻¹²

Kilo (k): 10³

What is concentration, and how can it be expressed?

Concentration: the amount of solute dissolved in a given amount of solvent

Concentration can be expressed in a number of ways

• Weight in volume (most common)

  • The number of grams in 100ml of solvent

  • e.g 5%= 5g per 100ml

• Volume in volume

• Weight in weight 

• Molarity

• Parts

• Mass = concentration x volume

What is meant by ‘dose’?

Dose: the quantity of drug to be delivered to a patient

Why are dilutions used, and what is the dilution factor?

Dilutions are used when the amount of compound required is so small, it cannot be accurately measured

Dilutions often involve combining a volume of a known solution (stock solution) with an appropriate volume of solvent

The dilution factor is the total number of unit volumes, in which your material is dissolved, or how much more concentrated one solution is compared to another

e.g a 1 in 5 dilution combines 1 volume of the solution with four volumes of the solvent

• Therefore the dilution factor is 5

• Dilution ratio is 1:4

How can you determine the rate of administering fluids, and what is drip rate usually measured in?

The rate of administering intravenous fluids can be determined from:

• Volume of fluid needed

• Time of administration

• Number by the drops per ml delivered by the giving set 

Drip rate: usually how many seconds per drop

Draw out the basic structure of the cat/dog heart