cardiovascular system. learning objectives i to outline the cardiovascular system; to state the...
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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