Anatomy and physiology of cardiovascular system

Key components of CV system

• blood (liquid)

• Blood vessels (pipe)

• Heart (pump)

How much body mass does blood make and how much in M and F?

8% body mass

M = 5-6L

F = 4-5L

What are the functions of blood?

• transportation

• Homeostasis

• Protection

Describe transportation - function of blood

• transport O2 from lungs to body cells and CO2 back to lungs

• Transport nutrients from GI tract to body cells

• Transport hormones from endocrine glands to body cells

• Transport heat and wasted products to lungs, kidneys and skin for elimination from body

Describe homeostasis - function of blood

• control pH through buffer

• Adjust temp

• Osmotic pressure to control water content of cell

Describe protection - function of blood

• white cells and Ab can be carried to pathogens to protect against infection

• Blood can clot to protect against excessive loss and then form barrier for protection from infection

Components of blood and quantity

• blood plasma - 55%

• Erythrocytes RBC - 45%

• Leukocytes WBC - <1%

• Platelets - <1%

Describe plasma and what it is made out of?

Straw coloured sticky fluid

Transport molecules - over 100 types

Made from : 91.5% water, 7% protein, 1.5% others

Draw pie chart of components of plasma and describe what each is made of I.e what proteins and their functions, for others what’s in it?

What are erythrocytes? And structure?

Oxygen carrying cells:

• cytoplasm packed w/Hb

• Hb has single Fe2+ ion which reversible binds to O2

Biconcave shape:

• provide 30% more SA than sphere

• Allow more rapid o2 diffusion

No nucleus/organelles:

• exclude H2O, 97% RBC is Hb

• Generate energy anaerobically so don’t use up O2

Live for 100-120 days

• replacement can be slow for this reason

What are leukocytes and what are 5 types and their functions

WBC

Mobile part of immune system

5 types of WBC

Granulocytes:

• neutrophils

• Eosinophils

• Basophils

Agranulocytes:

• lymphocytes

• Monocytes

What are platelets (thrombocytes)? And functions

Fragment of cells (megakaryocytes)

• cells grown huge then splinter into 2000-3000 fragments

• Each fragment wrapped in membrane and is a platelet

Chemicals inside can promote blood clotting

React to tissue damage and activate - become sticky

• help form clotting

Whats haematopoisesis? What do they receive? What to progenitor cells produce?

• red marrow

• Haematopoietic stem cells receive cytokine, erythropoietin and thrombopoietin signals

• Progenitor cells produce precursors cells that become “committed” to type of blood cell

• Mature cells enter blood stream (diapedesis)

What are the 2 distinct circuits that blood never leaves?

Systemic circulation:

• oxygenated blood pumped out of heart through aorta

• Blood returns to heart via vena cava

Pulmonary circulation:

• deoxygenated blood pumped through pulmonary artery to lungs

• Blood returns to heart via pulmonary vein

Describe arteries and structures

• away from heart

• Thicker muscle

• Higher BP

• Muscle contracts forcing blood through

• Thicker walls allow them to withstand high pressures

Describe veins and structure

• toward heart - in

• Thinner muscle

• Lower BP

• Presence of valves to prevent backflow

• Thinner walls so catch withstand high pressure but good at adapting to different blood volumes

• Veins primarily rely on heart pumping to move blood but veins in lower limbs also use contraction of muscles.

What is tunica intima, media, externa

Tunica intima - smooth muscle for blood flow

Tunica media - smooth muscle and elastic tissue control vasodilation and vasoconstriction

Tunica externa - thick layer of connective tissue to protect vessels

Whats a distributing artery?

Medium sized artery that carries oxygen rich blood from large arteries to specific organs or body parts.

Has thick muscular walls to control blood flow by tightening or relaxing.

E.g brachial artery, radial artery

Whats a conducting artery?

Large arteries that carries blood directly from heart and stretches to handle high pressure,

Has elastic walls that expand and recoil to help smooth out blood flow.

E.g aorta, carotid artery

What are small arteries?

Arteries smaller than distributing arteries that array blood to even smaller vessels called arterioles.

Have thick muscular walls to help regulate blood flow and blood pressure before blood reaches capillaries.

Control blood flow into capillaries

What are little veins?

Venules small blood vessels that collect deoxygenated blood from capillaries and carry towards large veins.

Have thin walls and help start return of blood back to heart.

Drain capillaries blood

Features of large veins to elastic artery photo

Whats a capillary and 3 kinds?

deliver substances to cells in body in extensive interconnected networks

3 kinds:

• Continuous - least permeable - substances leave/enter through intercellular clefs. —> CNS,lungs,skin,skeletal and smooth muscle, connective tissue

• Fenestrated: more permeable - pores (fenestrations). Allows more substances to diffuse —> kidneys, small intensive, brain, eyes, endocrine glands

• Sinusoid - most permeable - wider and large fenestrations without full membrane surrounding them —> big enough for blood cells to pass through e.g RBC from bone marrow

What do arteries and veins carry in systematic circulation?

Arteries = carry oxygenated blood

Veins = deoxygenated

What do arteries and veins carry in pulmonary circulation?

Only in pulmonary circulation are arteries deoxygenated (blue) and veins oxygenated (red)

Location of heart to sternum, diaphragm, lungs

Posterior to sternum

Superior to diaphragm

Medial to lungs

Draw rough what heart looks like and surface anatomy

What 4 things is heart wall made out of?

Pericardium

Epicardium

Myocardium

Endocardium

Describe structure of 4 tissues in heart

Pericardium

• protective membrane w/ multiple layers of connective tissue, fluid filled to reduce friction. Keeps heart in position whilst allowing movement for breathing

Epicardium:

• connective and adipose fat tissues for protection - fat accumulates here during to weight and age

Mycocardium:

• thickest part of wall (95%), cardiac muscle that contracts for heart beats

Endocardium:

• interior lining covering valves also. Thin smooth layer which minimised surface friction w/ blood.

What are the 4 chambers of the heart?

Left atrium - receives oxygenated blood from lungs

Right atrium - receive deoxygenated blood from body

Right ventricle - blood to lungs

Left ventricle - blood to body

Which heart chamber has least muscle? Which has more and why? Whats brachial systemic and pulmonary systolic BP?

• atria has least muscle as only needs to move blood to next chamber

• Ventricles needs more muscle to push blood out of heart

• Muscle of left ventricle substantially thicker to allow for even stronger force of contraction.

• Brachial systemic artery systolic BP = 120mmHg

• Pulmonary artery systolic BP = 12mmHg

What are valves? What do they do?

• prevent blood from flowing backwards by only opening one way

• Open and close dependent upon pressure e.g mitral opens when pressure higher In atria than ventricles and close when reverse is true

• “Slam” closed which can be heard with stethoscope “lub dub”

What are the 2 types of valves and functions

Atrioventricular valve:

• tricuspid - 3 leaflets

• Bicuspid (mitral) - 2 leaflets

• Between atria and ventricles

• Allow blood flow to ventricle but not back to atria

• Feature chordate tendinea and papillary muscles which reinforce against pressure of ventricle contraction

Semilunar valves:

• aortic

• Pulmonary

• Named after 3 leaflets being crescent moon shaped

• Attached to arterial walls

• Allow blood flow to arteries but not back to ventricles

Are there any valves from vein to atria?

No valves between atria and veins

When atria contracts some blood does flow backwards but it’s minimised by direction of contraction of atria

Describe blood Flow inside the heart

• deoxygenated blood enters RA from vena cava (back from rest of body) - end of systemic circulation

• RA contracts and forces tricuspid valve open as pressure in atrium is higher than pressure in ventricle

• Deoxygenated blood pushed by RA into RV

• RV contract, pressure causes tricuspid valve to close

• Pulmonary valve opens

• Deoxygenated blood pushed into right ventricle into pulmonary arteries

• Blood travels to lungs - beginning of pulmonary circulation

• Oxygenated blood enters LA from pulmonary vein - end of pulmonary circulation

• LA contracts and cause mitral (bicuspid) valve to open

• Oxygenated blood pushed by LA into LV

• LV contracts and forces mitral valve to close

• Aortic valve opens

• Oxygenated blood pushed by LV into aorta

• Blood travels around body - beginning of systemic circulation

Summarise blood flow in heart

Heart relaxes

Blood flows into atria

Atria contract

Blood flows into ventricles

Ventricles contract

Blood flows into arteries

What are the 3 phases of cardiac cycle?

Atrial systole - atrial walls contract

Ventricular systole - ventricular walls contract

Diastole - relaxation of heart muscle

Systole - contraction of heart muscle (myocardium)

Describe process of electrical signalling

• excitation begins at sinoatrial SA node (pacemaker) in RA and flows through RA across to LA. Signal can’t enter ventricles through walls between chambers

• Signal hits Atrioventricular AV valve where it’s held for 0.1s.

• AV bundle connects atria to ventricles

• Signal travels down insulated routes down blunder of his and slits into left and right bundle branches. Bundle branches conduct impulses through interventricular septum

• Signal travels to purkinje fibres which spread around heart muscle and aren’t insulated allowing signal to reach ventricle muscle.

• Subendocardial conducting network stimulated contractile cells of both ventricles

Summarise electrical signalling

SA node

Atria contract

AV node - delay

Bundle of his

Bundle branches

Purkinje fibres

Ventricles contract

What causes higher BP? Systolic or diastolic?

Systolic - 120

How do we measure movement of electrical current in heart?

ECG

V4 is apex

How does ECG show activity?

P QRS T

Whats autonomic and innervation? How can SA node operate and how does it link to medulla oblongata?

Autonomic = involuntary or unconscious

Innervation = stimulate an activity

Heart rate of contraction set by SA node

SA node can operate independent of signals

But rate can be altered by neural controls from medulla oblongata

Medulla oblongata receives instructions from higher brain regions e.g hypothalamus

Whats the cardioinhbitory centre and cardioacceleratory centre? Functions?

Cardioinhibitory:

• parasympathetic innervation - rest and digest

• Decreases HR

• Restricted to SA and AV nodes and coronary arteries

Cardioacceleratory:

• sympathetic innervation - fight or flight

• Increase HR and strength contraction

• Targets same structure as parasympathetic fibres but also project to cardiac musculature throughout heart

Whats the normal HR? How to count?

• 60-100 bpm

• Count by pressing radius pulse on wrist under thumb for 15s then x4

How does heart get its blood supply?

• walls of heart too study for blood inside it to diffuse into tissue and there are no capillaries on inside

• Provides O2 and nutrient the wall has own blood supply called coronary arteries

• Heart is muscle so when works hands it needs more o2

What phase does heart receive blood?

Heart only part of body that receives its blood supply in diastolic phase

Describe what’s happening in the 6 boxes - grey, red, blue,green,orange, purple

Grey - Atrial Systole - P wave - electrical signal in L+R atria. Pushes blood into ventricles —> ventricular volume increases as blood pushed in

Red - Ventricular systole - ventricle start contracting. Pressure increases. As soon as pressure in it exceeds pressure in atria, it forced mitral + aortic valve closed —> “lub”. Then reaches point where pressure in ventricle height that in atria and that opens aortic + pulmonary valve —> blood flows into circulation. QRS complex

Blue - Diastole - relax - BP in aorta higher than in ventricles so slam shuts valves —> “dub” - blood can trickle into atria here

Green - Atrial systole - electrical signal flow through atria and pushes blood into ventricles

Orange - ventricles contract into circulation - 1st heart sound.

Purple - relaxes. Valves close. 2nd heart sound