Cardiovascular system

Learning objectives I

To 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 II

To 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 Human

The 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

Platelets

250,000 blood platelets / mm3 Small colorless fragments No nucleusProduced in bone marrowLife span: 10 days

Function of platelets

Stimulate 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 blood

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

Structure of heart

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

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

Atrium

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

Ventricles

Lower 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 valves

Allow 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 pulm

onary artery & the aorta

Coronary system

Coronary artery ~ branches from aorta ~ supplies oxygen and nutrients to

the heart muscleCoronary vein

~ drains deoxygenated blood from the cardiac muscle into RA

Heart beat

Heart 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 impulses

SA 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 cycle

Sequence of events taking place in one heartbeat:

~ Atrial systole (contraction of atrium)

~ Ventricular systole (contraction of ventricles)

~ Diastole ( both atrium and ventricles relax)

Heart sound

1st heart sound “Lup”: ~ closure of tricuspid & bicuspid valves ~ low pitched, not very loud, long dura

tion2nd hear sound “Dup”

~ closure of semi-luna valves ~ high pitches, louder, short duration

Control of heart beat I

Cardiac 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 II

Nervous regulation ~ Parasympathetic nerveCardio-inhibitor center vagus nerve acetych

oline SA node slow down heart beat~ Sympathetic nerveCardio-accelerator center accelerator nerve

noradrenaline SA node heart beat

Control of heart beat III

Hormonal control~ Adrenaline heart beat

Others~ pH Heart beat

~ temperature Heart beat

Blood vessels

Artery~ elastic artery~ muscular artery~ arterioles

Vein~venules

Capillary

Artery

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

Capillary

No muscle & elastic tissueLinks arteries to veinBlood change from oxygenated to deoxygenated

Vein

Thin 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 veins

I. 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 veins

III. 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 aci

d, fatty acid, hormones, water & inorganic ions

Matter in:CO2, ammonia, lactic

acids

Variation in blood pressure

Blood pressure in

Arteries> Arterioles> Venules & vein > capillaries

Variation on permeability of blood vessels

Permeability of

Capillaries > 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 velocity

Velocity in arteries > veins > capillaries

Blood circulation in the body

Mammalian double circulationCoronary circulationPortal circulationRenal system

Double circulation

Pulmonary 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 circulation

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

Portal circulation

It 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 system

Kidney 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 nodes

Swelling 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