Transport of Materials to and From Cells

Nutrients – from SMALL INTESTINE to blood – from blood to cells

O2 from the AIR to blood (LUNGS) – from blood to cells

CO2 from cells to blood – from blood to LUNGS – from lungs to AIR

Urea (nitrogenous waste) from LIVER to blood – from liver to KIDNEYS – formation of urine

Features of a good transport system

A circulating FLUID or MEDIUM to carry materials around the body – BLOOD (Plasma + Cells)

A MUSCULAR pump to create pressure that will push the fluid around the body – the HEART – composed of CARDIAC MUSCLE

Vessels to convey the medium from one region to another – ARTERIES, CAPILLARIES, and VEINS

EXCHANGE SURFACES – enable useful materials to enter the blood and to leave it again where they are needed.

TWO circuits (DOUBLE CIRCULATION)– one to pick up O2 and another to deliver O2 to the tissues

Single Circulation – e.g. fish

Blood pressure reduced as blood passes through the gill capillaries - slows down flow to the rest of the body

Limits the rate of delivery of O2 and nutrients to cells and removal of waste

Efficient for the level of activity of fish but not mammals – also fish do not maintain their body temperature – need to respire relatively less compared to mammals

Double Circulation – more efficient - e.g. mammals

Heart is composed of two separate pumps – right side pumps blood to the lungs to pick up oxygen; the blood is returned to the left side; the left side pumps oxygenated blood rapidly and at high pressure to the body; the blood is returned to the right side

Higher level of activity (energy) and need to maintain theirbody temperature at 370C – through respiration

Need to deliver and remove materials to and from cells rapidly – achieved by delivering blood at high pressure to tissues.

Pulmonary – oxygenates blood & removes CO2Systemic – oxygenated blood from lungs pumped rapidly at an increased pressure by the heart

Blood passes through heart TWICE per complete circuit

Blood passes through heart ONCE per complete circuit

Open Circulatory System

Some animals (e.g. insects) have an open circulatory system – the circulating blood is not contained within vessels all the time. It flows freely through the body cavity and is in direct contact with the body cells.

Blood circulated in a closed circuit – comprisingthe heart and blood vessels - It is a CLOSED circulation

DOUBLE circulation2 circuitsPulmonary & SystemicBlood passes through heart twice per complete circuit

In lungsO2 diffuses into RBCsBlood oxygenatedHb + O2 HbO2CO2 diffuses into alveoli

In tissuesBlood deoxygenatedHbO2 Hb + O2O2 diffuses into cellsCO2 diffuses into plasma

Hb = haemoglobin

Pulmonary circulation

Systemic circulation

O2

CO2

O2

CO2

O2

O2

CO2

CO2

Against pathogens - white blood cells - phagocytosis (neutrophils); immune response - production of antibodies and antitoxins (lymphocytes)

Transport

Functions of Blood

Defence

Blood clotting To prevent blood loss at site of damage & prevent entry of pathogens (platelets)

red blood cells

1 Larynx

2 Trachea

3 Thymus gland

4 Right lung

5 Left lung

6 Heart

7 Diaphragm

1. Right Auricle

2. Right Ventricle

3. Brachiocephalic Artery (Oxygenated blood)

4.Aortic Arch (Oxygenated blood)

5.Pulmonary Artery (Deoxygenated blood)

6. Left Auricle

7. Interventricular Sulcus

8. Left Ventricle

Anterior view of heart

Labels

A Right ventricleB Bicuspid (mitral) valveC Tricuspid valveD Right atriumE Pulmonary veinF Pulmonary arteryG Vena cavaH Aortic semilunar valveI Pulmonary semilunar valveJ Chordae tendinae

Activity - Label the diagram of the heart

The cardiac cycle

Heart relaxed AV valves are open

Deoxygenated blood from vena cava flows into RA Oxygenated blood from pulmonary vein flows into LA

Blood passes into ventricles passively

SA node contracts – sends impulses through atriaAtria contract (top downwards) – forces additional blood into ventricles

through AV valvesBlood from RA to LA; blood from LA to LV

Ventricles receive impulses from AVN via Purkinje fibres – ventricles contract (bottom upwards) – force of blood causes AV valves to close (lub)–

prevents blood flowing back into atria

Blood is forced from RV into PA through pulm semilunar valves and from LV into aorta through aortic semi lunar valves

Heart relaxes – semilunar valves close due to force of blood (dub)- prevent backflow from pulm artery and aorta into heart - AV valves open

Atria fill with blood again to start cycle again

Cardiac Cycle

Blood from RV to LA

Right ventricle muscle contracts-tricuspid valve closes- pulmonary semi-lunar opens – blood forced into pulmonary artery – ventricles relax – pulmonary semilunar valve closes – blood forced to lungs from pulmonary artery - blood sent to left atrium via pulmonary vein – valves in veins prevent backflow

A Atrioventricular (bicuspid / mitral) valve(s) closes (“snaps shut”– makes 1st louder heart sound “LUB”

B Semilunar valve(s) (aortic valve) opens

C Semilunar valve(s) closes – makes second softer heart sound “DUB”- shut due to blood accumulating in their pockets

D Atriioventricular (bicuspid) valve(s) opens

“LUB”

“DUB”

Atrial Systole

Ventricular Systole

Diastole

Cardiac cycle= 0.8 sec

60/0.8 bpm= 72 bpm

Pressures changes in the aorta, left ventricle and left atrium during one heartbeat

© Pearson Education Ltd 2008This document may have been altered from the original

Week 8

Length of 1 cardiac cycle ~ 0.8 secNo of beats per minute = 1 x 60/0.8 sec = 75 beats/min

Electrocardiogran (ECG)

P wave = electrical activity during atrial systole

QRS complex = electrical activity during ventricular systole

T wave = ventricular repolarisation (recovery of ventricular walls)

Q-T interval – contraction time (ventricles contracting)

T-P interval – filling time – ventricles relaxed and filling with blood

Pattern are studied in different conditions and compared to the standard ECG in order to diagnose heart conditions, such as arrythmias and fibrillation. Fibrillation is stopped by passing a strong electric current through the chest wall – the heart stops for up to 5 seconds after which it begins to beat in a controlled way

Electrodes are placed on the skin over opposite sides of the heart, and the electrical potentials generated recorded with time. The result is an ECG.

A normal ECG trace compared with others indicating an unhealthy heart

Regulation of the Heart

•Atria relaxed – fill with blood•RA with deoxygenated blood from vena cava•LA with oxygenated blood from pulm vein•SAN sends out 72 impulses/min over atrial wall – atria contract 72 times/min•Atria contract to force blood into ventricles•Atria relax•Impulse reaches AVN•Delayed momentarily•Impulse travels through nerve fibres of the atrioventricular bundle and its branches into walls of the ventricles•Ventricles contract – from apex upwards to force blood into arteries•Oxygenated blood from LV to aorta – to body•Deoxygenated blood from RV to pulmonary artery – to lungs (to be oxygenated)

Cardiac Output

Stroke Volume X Heart Rate = CO75 X 70 = 5250 ml/min – Normal

Factors that increase SV or HR increase CO

SV depends on how much blood enters the ventricle during diastole

HR is regulated by several factors – Chemical(e.g. CO2; pH) and physical ( blood pressure)

Muscles – greater demand for O2 and nutrients (glucose) for energy; increased production of waste – CO2 and lactic acid; excess heat produced - need to be removed. Increase in CO2

detected by chemoreceptors in aortic arch and carotid artery

Accelerator (sympathetic cardiac) nerve releases chemical neurotransmitter (NE) at SAN to increase rate and force of contraction of heart to increase cardiac ouput

Adrenaline is released from adrenal gland – stimulates heart (increase rate and force; dilates blood vessels in muscles to increase blood flow)

Decelerator (vagus) nerve releases chemical (acetylcholine) at SAN to slow heart

Carotid artery

Aortic arch

Exercise; Stress; Fright

The pathway followed by the wave of excitation

Narrow lumen; High pressureHighly elastic – expand and recoilThick muscular wall – to withstand force; more elastic fibres (recoil)No valves (except aortic and pulmonary semilunar at the start)Oxygenated blood from heart – except pulmonary artery to lungsPulsatile blood flow (expansion + recoil)Pulse can be felt – e.g. wrist

Wide lumen; Low pressureThin wall - less elastic and less muscularValves (semilunar) – prevent backflowDeoxygenated blood to heart from tissues - except pulmonary vein from lungsNon pulsatile – smooth flow of blood

Capillary – endothelium – large number – large surface area for exchangeWall - one cell thick – short diffusion distance Endothelium is continuous throughout circulatory system

ArteryVein

Capillary

Blood – a connective tissue

Blood cells are made from stem cells, mainly in the bone marrow and foetal liver

Plasma (liquid part – 55%) – 90% water + 10% substances Transports substances around the body CO2 from cells to lungs; urea from liver to kidneys; hormones; enzymes; antibodies; fibrinogen; heat

White blood cells (Leucocytes) – 5000 – 7000 per ml of bloodDefenceLymphocytes (produce antibodies and antitoxins)Phagocytes – engulf and destroy pathogens (microbes)

Platelets (Thrombocytes) – 200 000 – 300 000 per ml of bloodblood clotting – cell fragments - contain enzymes – released a the site of a cut – converts soluble blood protein fibrinogen to insoluble fibrin – forms blood clot – prevent loss of blood and prevent entry of microorganisms

Red blood cells (Erythrocytes) – 4 -6 million per ml of blood45% of blood volume (termed the haematocrit) – lower in anaemiaTransport oxygen from lungs to cellsContain blood group antigens on surface of membrane

5 – 6 litres

Lymphocytes Defence – immune responseProduce antibodies and antitoxinsKiller cells – destroy cells infected with viruses

NeutrophilsDefence - phagocytosisContain enzymesEngulf (ingest) microbes and digest them

Red blood cells (erythrocytes) Contains haemoglobin (Hb) - formation requires FeHb transports O2 from lungs to cells Biconcave discs – large surface area for diffusion of O2

No nucleus – more space for HbFlexible – squeeze through capillaries in single file

PlateletsRupture and release enzyme at site of cut – initiates a cascade of reactions – converts insoluble blood protein fibrinogen to insoluble fibrin threads which trap blood cells and platelets to form a blood clot

Activity -Blood Vessels

1

2

3

4

5

6

7

8

9

10

1

10

6

8

7

3

45

9

2

E ………………………..

Hole in the Heart

Congenital (at birth) – between atria or ventriclesAllows mixing of oxygenated and deoxygenated blood – blood passes from RA to LASome blood does not enter ventriclesSome blood does not enter ventricles and pulmonary arteryReduces systolic pressure

Dangerous if not treated

Pressure reduced – some blood bypasses lungsLess O2 carried/picked up/loadedLess respiration – decreased O2 supply to cells – less energyWeakness; anaemia;

 

Platelets & Blood Clotting(Haemostasis)

1 Damage / Cut

2 Vascular spasm (vessels constrict – to reduce blood flow

3 Platelets become sticky – form a Platelet plug

4 Platelets rupture on contact with air and damaged tissue - release thromboplastin (enzyme)

5 Cascade of reactions (involving plasma proteins (clotting factors)

6 Fibrinogen (soluble) to fibrin (insoluble)

7 Blood cells trapped – CLOT formed

8 Clot tightens (retracts) - fibrin seals open tissue – hardens into a scab

9 Clot dissolves after blood vessel repair

Heparin prevents clotting normally – inhibitsconversion of prothrombin to thrombin – action ofanticoagulant drugs (e.g. warfarin) used clinically

Thrombosis – clotting in unbroken blood vesselStroke – clotting in cerebral blood vessel

Streptokinase – enzyme used clinically to dissolveblood clots in vessels

RequiresVitamin K

http://uk.youtube.com/watch?v=rguztY8aqpk

http://www.gwc.maricopa.edu/class/bio202/heart/inthrt.htm

http://www.zerobio.com/videos/sheep_heart_anatomy.html

http://www.vimeo.com/1813369?pg=embed&sec=1813369