8. Transport in MammalAnd the Circulatory System

Why do we need a mammalian transport

System Animals – far more active

than plants Need energy for –

contraction of muscles, brain power, mobility (have to find their own food), nervous system

Evolved transport system Diffusion – too slow, the

surface area is not enough

Pulmonary Circulation

Deoxygenated blood moving out from the right ventricles through the pulmonary arteries to the lung.

The now oxygenated blood then travels back into the left atrium from the pulmonary vein.

Systemic Circulation

Oxygenated blood moving out of the left ventricle through the aorta to the rest of the body.

Deoxygenated blood travelling back through the vena cava into the right atrium

The Blood vessels

ArteryCapillariesVein

Arteries

Vessels that transport blood at high pressure to the tissue away from the heart

Inner endothelium: Tunica intima – layer of flat squamous epithelium cells – REDUCE FRICTION

Middle layer: Tunica media – smooth muscle, collagen, elastic fiber

Outer layer: Tunica externa – Elastic fiber/ collagen fibers

Arteries

Strong and elasticTo withstand high pressure of blood leaving

the heart (120mmhg)Elastic fibers: Wall can stretchAllows the heart to moderate the pressure of

the blood by recoiling or stretching

Arterioles Arteries branch into smaller vessels –

Arterioles Arterioles’ wall have more smooth

muscle The muscle can contract – controlling

the volume of blood moving in and out of a certain body part

Vasoconstriction and vasodilation occurs with arterioles

Blood pressure drops here from 120 to 85 as arteries branch out

Capillaries

Arterioles further branch out into capillaries where cell will receive oxygen and give out waste

One-cell thick wall (endothelium) – 7 micrometer – just enough for Red blood Cell

Blood brought to 1 micrometer from the cellBlood pressure drops enough for slower flow

with exchange of thingAllow diffusion to occur

Venules

Capillaries gradually join up to form Venules Venules join to form veins – function: return

blood to the heart

Veins

Blood pressure is low – no need for elastic muscles or thick wall

Larger lumenBlood flow because the contraction of muscle

around the veinsBackflow prevented by semilunar valves

THE LYMPHATIC SYSTEMBLOOD PLASMA, TISSUE FLUID, LYMPH

Blood Plasma

Pale yellow liquid composing of 55% of the blood

Content: 90% water – 10% : Ions, Glucose, Urea, Plasma proteins (amino acids, hormones, enzymes, antibodies etc.)

Blood plasma - Importance

Contains hormones and other useful substances

Maintains pH and osmotic balance

Tissue Fluid

When passing through capillaries – plasma leaks into the spaces between cells forming tissue fluid

Proteins cannot pass throughWhite blood cells can squeeze through

Tissue Fluid The process is as such: The high blood pressure at arterial end of capillary bed –

causes blood plasma to flow out of capillaries High protein concentration in plasma = lower water

potential, osmotic pressure causes plasma to flow back into capillaries at venule ends of the capillary bed

Hence tissue fluid maintains the osmotic balance of the cell

If blood pressure too high – at arterial ends too much of the plasma flow into tissue fluid and accumulates – swelling in the form of oedema

Lymph

90% of fluid that leaks out of capillary – seeps back Another 10% is returned by the lymphatic system Lymphatic systems: made up of lymph vessels The lymphatic will allow tissue fluid to leak in Lymph vessels have valves large enough for

proteins Lymph nodes: contain antibodies https://www.youtube.com/watch?v=I7orwMgTQ5I

The Lymphatic system

The lymphatic system’s main job is to return blood plasma to the blood and also to maintain the osmotic balance by allowing protein to leak in from the tissue fluid

The system is also where a lot of of the white blood cells reside

Content of Blood

5 dm3 blood = 5 kg5 x 1013 Red Blood Cells/ Erythrocytes6 x 1012 Platelets2.5 x 1011 White Blood Cells/ Leukocytes

Red Blood Cells

Small size = 7 micrometersBiconcave shapeSmall amount of organellesHigh flexibility in membrane

HemoglobinThe Dissociation curve, Transport of Carbon dioxide and the

Bohr Shift

Haemoglobin

Proteins found inside the red blood cellsThey combine with oxygen to form

OxyhaemoglobinThey are tools Red blood cell uses for

transporting oxygenEach haemoglobin has 4 haem groups with each

one containing an iron prosthetic groupThis iron allows the molecule to combine with

oxygen and hence give a red color to blood

The Dissociation Curve

This is a curve used to show how haemoglobin combine with oxygen at different partial pressure

It is important to show how haemoglobin pick up oxygen but also how it releases those oxygen molecules

The Dissociation Curve

At low partial pressure of oxygen – percentage saturation is very low – haemoglobin combines with very little, in this case 1 oxygen molecule

As partial pressure increases, it gets easierPlus haemoglobin changes shape after first

combination to make it easier for the other 3https://www.youtube.com/watch?v=

HYbvwMSzqdY

The S-Curve

We must also take in account the changes of partial pressure of Carbon Dioxide

Where there are high CO2 concentration (high partial pressure) eg. Muscle cells – usually respiring cells that actually do need oxygen

Oxygen will be released more readilyHow so?

The Bohr Shift

When Carbon Dioxide enters the Red Blood cell, carbonic anhydrase allows it to combine with water to form Carbonic acid

The Carbonic acid dissociates into Hydrogen bicarbonate and hydrogen ions

The hydrogen ion is actually taken up by the haemoglobin

And hence the oxygen has to be released THIS IS PERFECT, BECAUSE NOW OXYGEN IS

RELEASED WHERE IT IS NEEDED MOST

Transport of Carbon dioxide

Because of the Bohr shift – 85% of the CO2 is now transported in the form of hydrogen bicarbonate ions

Another 10% of CO2 directly combines with haemoglobin to form Carbaminohaemoglobin

The other 5% is transported in solution

Problems with Oxygen Transport

High Altitude, Carbon Mooxide

Effects of Carbon Monoxide

Haemoglobin combines very readily with Carbon monoxide – even more so than oxygen (250 times more)

To form Carboxyhaemoglobin – a very stable molecule

Now the body cannot transport oxygen Carbon monoxide quickly diffuse through

alveoli Even 0.1% in the air may cause death by

asphyxiation They are found in cigarette smokes –

hence most smokers actually have 5% of their blood permanently combined with carbon monoxide

Effects of High Altitude

Partial pressure of oxygen in normal air is higher than in air at high altitude

Haemoglobin becomes less saturatedLess oxygen carried around the bodyCausing breathlessness and illness

Altitude Sickness

When the body doesn’t have enough time to adjust to the change in altitude

Increase in rate/ depth of breathDizziness and weaknessArterials dilate for more oxygen transport –

blood flow into the capillary bed more – oedemaOedema in brains can lead to disorientationThe way to cure is simple – come down

Adaptations

If the body is allowed to acclimatized – number of Red Blood Cells increases – usually takes 2 -3 weeks

Permanent adaptations for those living at high altitudes

Broader chest – for more lung capacity

Larger right side of heart – to pump blood to the lung

More haemoglobin

The HeartHeart beats and how they work

The Heart Structure

Mass: 300 gSize: fistA bag of muscle filled with bloodMuscles – cardiac muscles – interconnecting

cells with membranes tightly joined for electrical excitation to pass through

Aorta

The largest artery Arch shape Branches leading to the

head Main flow double back

down toward the body High pressure blood flow

here Connected to the left

ventricle

Venae Cavae

2 large veins running vertically on the right side of the heart, Connected to the right atrium

1 vessel (superior vena cava) brings blood from rest of the body

Another brings blood from the head

Pulmonary Arteries/ Veins

P Artery: takes blood out of the heart to the lung – connected to the right ventricle

P Veins: Takes blood from the lung into the hear – connected to the left atrium

The revers of the rest of the body – if veins at the rest of the body carry deoxygenated blood, pulmonary veins carries oxygenated blood. Same goes for pulmonary arteries

Pulmonary artery branches off immediately to the right and left lung

Pulmonary vein returns first into then combine into one

Coronary arteries

Branch off from aortaDeliver oxygen to the heart itself

The Cardiac Cycle

The sequence of events which make up one heartbeat

3 stagesAtrial systoleVentricular systoleVentricular diastole

Atrial Systole

Heart is filled with blood – muscle ready to contract

Muscular wall of atrial are thin – contraction do not produce much pressure

Pressure still forces Atrioventricular valves (tricuspid/ bicuspid) open

Blood flows from the atria into the ventriclesValves in the veins prevent backflow

Ventricular Systole

0.1 seconds after the atria contractVentricles contractAtrioventricular valves pulled shut due to the

pressure in the ventricles exceeding the atriaSemi lunar valves forced openBlood rushes into the arteriesThis lasts for 0.3 seconds

Ventricular Diastole

The whole heart muscle relaxesSemilunar valve shutsBlood from veins flow into the atria – at low

pressure – but thin wall of atria gives not much resistance

Blood just begins flowing into the ventricles when the atria contracts again

Control of heart beat

The muscles in the heart are myogenicThey naturally contract/ relaxesThe heart still has its own natural pacemakerSinoatrial node (SAN) - in the right atrium wall

– it can still respond to the brainSAN works a little faster than the heart It sends excitation waves across the atrial walls

– causing atrial systole

Control of heart beat

Muscles of the ventricle contracts 0.1 second after – this is because of the AVN

The AVN (Atrioventricular node) receives excitation wave which it withholds until the atria contracts, then it sends down to the ventricles so that they can follow in contraction

Between atria and ventricle – a band of fiber that does not conduct electrical impulse is there

The AVN send the impulse down through the purkyne tissues in the septum which travels to the rest of the ventricles