Cardiovascular system

Learning objectives ITo outline the cardiovascular system;To state the general properties of cardiac muscle;To describe the conducting system of the heart;To describe the cardiac action potentials;

Learning objectives IITo describe cardiac cycle;To define cardiac output and blood pressure;To describe the structure of blood vessels;To identify the control of cardiac function and blood circulation;To state the composition of blood;To describe the relation between blood and lymph.

Transport in HumanThe necessity:

far distancehigh metabolic rateslow diffusionsmall surface area for material exchange

The circulatory system in Human

Transport medium: bloodPumping device: heartOne- way flow: valvesWay for the exchange of materials: capillary network

Plasma~ pale yellow, alkaline, 90% water,

10% solid materialsPlasma protein: fibrinogen, globulin, prothrombin & albumenCarbohydrates & fatsInorganic ions : Fe, Ca, K, Mg & NaNitrogen: urea, uric acid Others: O2. CO2 & antitoxins

Erythrocytes(Red blood cell)5,000,000 RBC /mm3

Female has less RBC than maleNo nucleus in matured RBCTiny biconcave discMillion hemoglobin/ RBCProduction: Fetus liver; Adult bone marrowLife span: 4 monthsDestruction: liver, spleen & bone marrow

Leukocytes(White blood cell)

Colorless or transparentAmoeboid in shape1-2, or more distinct nuclei5000- 10000 WBC/ mm3 5 main classes of leukocytes:

Neutrophils, eosinophils, basophils, monocytes & lymphocytes

Platelets250,000 blood platelets / mm3 Small colorless fragments No nucleusProduced in bone marrowLife span: 10 days

Function of plateletsStimulate contraction of injured vessels prevent blood lossAdhere to one another plug the woundFormation of thromboplastin main step of blood clotting

Hemophilia ~ / plateletexcessive bleedingHemorrhage ~ vit. K bleeding

Function of bloodTransportation ~ gas, food, wastes, heat, hormones & metabolitesHomeostasis ~ water balance, acid- base balanceDefense ~ blood clotting, phagocytosis & immune response

Structure of heartPericardium

~ double-layer sac surrounding the heart; ~ fluid fills the sac to reduce friction.

Heart chambers ~ right atrium ~ right ventricle ~ left atrium ~ left ventricle

AtriumUpper chambersThin wallSmaller than the ventriclesReceive blood from the veins Push blood into ventricles

VentriclesLower chambersThicker muscle wallPump blood out of the heart to he lungs or around the whole body.The muscular wall of the left ventricle is thicker than that of the right ventricle

Heart valvesAllow one-way flow of the blood.Closure of the heart valves results in heart beat sound “Lup dup”

Tricuspid valve: between RA & RVBiscuspid valve: between LA & LVSemi-lunar valve: at the base of pulmonary artery & the aorta

Coronary systemCoronary artery

~ branches from aorta ~ supplies oxygen and nutrients to

the heart muscleCoronary vein

~ drains deoxygenated blood from the cardiac muscle into RA

Heart beatHeart beats automatically i.e. it does not depend on impulses from the nervous system.Contraction is generated within the muscle itself.Pacemaker (SA node) is the origin of stimulus(cardiac action potential) for heart muscle contraction.

Important !SA node initiates

the heart beat, but the rate at which it beats can be varied by stimulation from the nervous system.

Spread of cardiac impulsesSA node

Atrial muscle

AV node

Bundle of His

All parts of ventricle

Characteristics of cardiac muscle

Long refractive period ~ avoid fatigueNo tetanus or oxygen debt ~ avoid fatigueHighly vascularized ~ adequate nutrients & oxygen

Characteristics of cardiac cycle

Pressure in Left ventricle > Pressure in Right ventricle thicker muscle wall of left ventricleLength of cardiac cycle is varied at different state, but during exercise, less time is consumed.

Cardiac cycleSequence of events taking place in one heartbeat:

~ Atrial systole (contraction of atrium)

~ Ventricular systole (contraction of ventricles)

~ Diastole ( both atrium and ventricles relax)

Heart sound1st heart sound “Lup”:

~ closure of tricuspid & bicuspid valves ~ low pitched, not very loud, long duration

2nd hear sound “Dup” ~ closure of semi-luna valves ~ high pitches, louder, short duration

Control of heart beat ICardiac pacemaker ( SA node)

~ nerve innervated the heart only regulate the rate of heart beat but not initiation of heart beatCardiac output

~ CO = Heart Rate x Stroke Volume

Control of heart beat IINervous regulation ~ Parasympathetic nerve

Cardio-inhibitor center vagus nerve acetycholine SA node slow down heart beat

~ Sympathetic nerveCardio-accelerator center accelerator nerve

noradrenaline SA node heart beat

Control of heart beat IIIHormonal control

~ Adrenaline heart beat Others

~ pH Heart beat~ temperature Heart beat

Blood vesselsArtery

~ elastic artery~ muscular artery~ arterioles

Vein~venules

Capillary

ArteryThick muscular wallSmall lumenMuch elastic tissueBlood under high pressureOxygenated blood except in pulmonary arteryElastic artery, muscular artery, arterioles

CapillaryNo muscle & elastic tissueLinks arteries to veinBlood change from oxygenated to deoxygenated

VeinThin muscular wallLittle elastic tissueLarge lumenPresence of valvesDeoxygenated except in pulmonary veinBlood under low pressure

Blood flow in arteriesLeft ventricle contract

Push blood through aorta

Ventricles relax & semi- lunar valve close

Elastic aorta recoils

Muscular wall contracts & push blood to adjacent part of

aorta

Blood flow in veinsI. Contraction of skeletal muscle~ many veins are lying between

large skeletal muscle;~ muscles contract and squeeze the

blood to flow forward in the vein.

Blood flow in veinsII. Inspiration movement

Inspiration

ICM & diaphragm contract

Enlarge thoracic cavity & pressure

-ve pressure suck blood towards the heart

Blood flow in veinsIII. Remaining blood pressure~ blood pressure in the vein is not

zero;~ the remaining blood pressure

pushes blood back to the heart.

Material exchange Matter out:O2, glucose, amino acid, fatty acid, hormones, water & inorganic ions Matter in:CO2, ammonia, lactic acids

Variation in blood pressureBlood pressure in

Arteries> Arterioles> Venules & vein > capillaries

Variation on permeability of blood vessels

Permeability ofCapillaries > arteries, arterioles, venules & veins

Variation in total sectional area

Capillaries have the largest total section area.This makes sure the blood staying in the tissue area longer, so promote material exchange.

Variation in velocityVelocity in arteries > veins > capillaries

Blood circulation in the body

Mammalian double circulationCoronary circulationPortal circulationRenal system

Double circulationPulmonary circulation

~ circulation of deoxygenated blood from RV to lungs and oxygenated blood return to RA;

~ a short cycleSystemic circulation

~ circulation of oxygenated blood from RV to other parts of the body and the deoxygenated blood returns to RA;

~ a long cycle.

Coronary circulationRight & left coronary arteries: supply oxygenated blood to heart muscle;Coronary vein drains deoxygenated blood into RA.

Portal circulationIt is characterized by having a vein with capillaries at both of its ends.The capillary network at both ends of the portal vessel promote rapid and efficient loading and unloading substances.

e.g. hepatic portal vein

Renal systemKidney receives urea-rich oxygenated blood via renal artery;Kidney drains urea-free deoxygenated blood through renal vein;

Lymphatic circulation system

Lymph~ Fluid leaks out

from the capillaries due to filtration

~ Similar composition as plasma except:

proteinWBCNo RBC

Lymph vesselsBlind endingPresent everywhereThin wall, no valvesLymph flow: adjacent skeletal muscle & breathing motion of chestLymph flows back to blood via: Right lymphatic duct & thoracic duct

Lymph nodesSwelling along lymph vessels at intervalConspicuous in armpits, angle of the jaw & groinAs filters for lymph prevent foreign particles from entering the bloodstream

Function of Lymphatic system

Bridge for the exchange of materialsCollects excess tissue fluid back to the blood circulationTransport oil soluble substancesFilters the lymphProduce lymphocytes