Adaptations for transport in Animals

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Adaptations for transport in animals

Open circulatory system (Insects, crustaceans, molluscs and other invertebrates)

Fluid pumped at a relatively low pressure from one main long dorsal tube shaped heart running the length of the body

Spaces= haemocoel

Fluid called haemolymph (like "blood" but does not contain a respiratory pigment) bathes tissues directly, poor control of fluid

Heart relaxes > Haemolymph sucked slowly back to the heart > valves and contraction of muscle wall aid the movement of blood t the head region > Open circulation starts again

Low pressure

Haemolymph leaves circulatory system and bathes organs directly

Blood contained in haemocoel

Little control of direction of circulation once in the haemoceoel

No respiratory pigment

Oxygen transported directly to the tissues

Closed circulatory system (Mammals, fish, amphibians)

Blood circulates in a fully enclosed system of tubes (Blood vessels)

Heart= Muscular pump, pumps blood at high pressure, rapid flow rate

Organs not in direct contact with blood but are bathed in tissue fluid

Blood contains respiratory pigment (Haemoglobin= carries oxygen)

Earthworms > Dorsal and ventral vessels run the length of the body > connected by 5 pairs of pseudohearts ( Not real hearts, has chambers)

High pressure in blood as it is contained in vessels

Organs not in direct contact with the blood, bathed in tissue fluid

Blood is always within vessels

Blood flows in a continuous system of tubes (vessels) around the organism

Oxygen diffuses into the blood and is carried around the body bound to haemoglobin (respiratory pigment)

Oxygen transported from the lungs in a system of vessels towards capillaries in body tissues

Single circulation

Blood passes through the heart once during one complete circuit

Pulmonary circulation: Consists of all the vessels involved in transporting blood between the heart and lungs

Systemic circulation: " ^ between the heart and the rest of the body excluding the lungs

Double circulation

Separate systemic circulation for the body and pulmonary circulation for carrying the blood to and from the lungs. Blood passes through the heart twice during one complete circuit.

Advantages:

Maintains high blood pressure in systemic circulation > ensures oxygen is delivered repairing cells rapidly

Allows for lower pressure in pulmonary circulation > Prevents build up of tissue fluid the lungs

Faster circulation in systemic than in pulmonary > Systemic transports blood around the body, has to travel a much greater distance therefore the left side as to generate a higher pressure and faster circulation, shorter distance traveled for the pulmonary circulation

Oxygenated and deoxygenated blood is kept separate > maintains a steep concentration gradient for oxygen at the tissue and CO2 in the lungs

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Blood vessels and the circulatory system

Blood vessels in a closed double circulatory system

From the heart > Arteries > Arterioles (smaller than arteries, lead to capillaries) > Capillaries > Venules ( Smaller than veins, lead away from capillaries) > Veins > To the heart

Blood vessels

Tunica externa > Tunica Media > Tunica Media > Tunica Intima > Endothelium > Lumen

Blood vessels composed of the same parts just in different proportions except for capillary which only consists of the endothelium.

Endothelium is the innermost layer of the vessel and is once cell thick, provides a smooth lining : short diffusion pathway, reduces friction, provides minimal resistance to blood flow

Elastic fibres abd smooth muscle > Middle layer of vessel/ tunica media > much thicker layer in arteries than in veins

Smooth muscle > Withstand high pressure, contracts and relaxes allowing arteries to flex , restricts blood flow (vasoconstriction), relax to allow blood flow (vasodilation)

Elastic fibres > recoil to maintain high blood pressure and to prevent overs-tretching, aids pumping, stretches to accommodate blood flowing at a high pressure

Collagen fibres > Outer layer of vessels, resistant to overstretching

Skeletal muscle runs very closely alongside veins: Types of muscle include > smooth, skeletal (both require nerves) cardiac muscle is myogenic, causes own impulses, contraction of the heart

Artery:

Thick layer of smooth tissue to withstand high blood pressure

Elastic fibres > Elastic recoil to maintain high blood pressure

Smooth tissue changes during vasoconstriction and vasodilation

Endothelium >simple squamous epithelial cell

10 mm

Arterioles able to adjust diameter to vary blood supply to a capillary bed

Vein:

Wider lumen (diameter) and thin walls, pressure and flow is lower

Pocket valves prevents backflow ensures blood travels in one direction, veins rush very close alongside skeletal muscle therefore when it contracts blood moves through the next valve

Can be compressed easily allowing contracting skeletal muscle to squeeze veins and push the blood along

6mm

Capillary:

Endothelium > one cell thick of squamous epithelial cells

Some may have pores on their walls

Permeable to water and dissolved substances like glucose amino acids, urea, oxygen and carbon dioxide

More efficient exchange of materials and geese due to short diffusion distance and larger cross-sectional area

Narrow lumen that restricts blood flow, slowing down blood

How valves work

Blood above the valve tries to flow back

Blood fills the pocket above the valve

This forces valve to shut

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Comparing blood vessels

Arteries:

Carry blood away from the heart

Thick walls with smooth tissue and elastic layers to withstand and maintain high blood pressure

Small lumen

No valves except for in the heart

High blood pressure

Usually oxygenated except in pulmonary artery

Veins:

Carry blood to the heart

Thin walls, mainly collagen

Large lumen to reduce resistance to flow

Many pocket valves to prevent back flow, except in veins leading from the head

Low blood pressure

Usually deoxygenated except in pulmonary vein

Capillaries:

Exchange of materials between blood and tissues, greater cross- sectional area

Very thin walls, permeable, once cell thick to allow the exchange of materials

Very small lumen, blood cells must distort to pass through

No valves

Blood pressure falls as velocity of blood decreases

Blood changes from oxygenated to deoxygenated except in lungs

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Heart

4 chambers

Cardiac muscle= specialised tissue that is capable of rhythmical contraction and relaxation over a long period of time without fatigue

Left side= Thicker muscular wall, needs to transport blood around the body excluding the lungs which is a much larger distance than the right side which only transports blood to and from the lungs.

Septum and apex ( bottom point of the heart)

Right side:

Superior Vena Cava (Vein > Top half of the body) / Inferior Vena Cava (Vein > Bottom half of the body) > Right atrium > atrioventricular valve (tricuspid) + tendinous chords + papillary muscles > Right ventricle > Semi lunar valves (Like pocket valves) >Pulmonary artery > Transports blood to the lungs

Left side:

2 Pulmonary Veins (one for each lung) > Left atrium > Atrioventricular valve (Bicuspid) + tendinous chords + papillary muscles > Left ventricle > Semi lunar valves > Aorta > Transports blood to the rest of the body excluding the lungs

Atrioventricular valves are forced shut due to high pressure > Tricuspid and bicuspid (R & L)

Ventricle contracts and pulls the papillary muscle and tendinous chords which keeps tension on the valves in the heart holding them in a closed position to prevent valves from inverting (prolapsing) s pressure in the heart changes

Coronary Arteries = Supply heart cells with oxygenated blood and glucose

Coronary Veins = Remove deoxygenated blood from cardiac muscle

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Cardiac Cycle( Continuous process)

Sequence of events in one heartbeat > Pumping action fo the heart consists of alternating contractions and relaxations

Systole = Contraction

Diastole = Relaxation

Atrial diastole is not shown, too quick to be shown in the cardiac cycle

Important that the chambers of the heart all contract in a co-ordinated manner, otherwise it may lead to insufficient pumping

Atrio-ventricular valves open when the pressure of blood in the atria is greater than in the ventricles, close when the pressure of blood in the ventricles is greater than in the atria

Opening and closing of semi-lunar valves depends on the relative pressures in the aorta and pulmonary artery and the ventricles

3 Stages:

Atrial Systole > Both atria contract, blood flows from atria to ventricles, backflow prevented by atrioventricular valves

Ventricular Systole > Both ventricles contact, atrioventricular valves forced shut due to high blood pressure in the ventricle, semi-lunar valves in the aorta and pulmonary artery are pushed open and blood flows from the ventricles into the arteries

Ventricular diastole > Atria and ventricles relax, semi lunar valves are forced shut and blood flows from the veins through the atria and into the ventricles

Pressure in the systemic circulation is always greater than the pulmonary circulation as blood is being pumped a further distance by the left ventricle which has a higher pressure than the right side of the heart only pumping blood to the lungs, if you extend the graph as this one only shows the blood pressure changes in the systemic circulation to show pulmonary circulation also, the graph would look the same as the systemic only the graph starts at a lower pressure.

Arteries > Highest pressure occurs in the aorta/arteries, rhythmic rise and fall corresponding to ventricular contraction

Arterioles > Friction in vessel walls causes a progressive drop in pressure, large cross-sectional area, narrow lumen > substantial decrease in aortic pressure, pressure in arterioles depends on whether they are dilated or constricted

Venules > Small diameter and friction, slows the blood flow (relationship between pressure and speed) > man capillaries in a capillary bed providing a large cross-sectional area > some fluid is forced out of capillaries into the tissues which further reduces blood flow

Veins > turn flow to the heart is non-rhythmic and the pressure in venues is low, pressure in the veins is low but never fall falls to zero due to massaging effect of the skeletal muscles.

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Control of heartbeat

Sino-atrial node (SAN) > Specialised cardiac fibres, act as pacemaker, sends out regular electric impulses ( Top of right atria)

Atrio-ventricular node (AVN)

Septum > Atrioventricular node > Bundle of His > Purkinje fibres

Heart is myogenic > Heartbeat is initiated from within the muscle itself, not due to electrical stimulation

Wall of right atrium SAN acts as a pacemaker

Wave of electrical stimulation arises at the SAN and the nerve impulses spread over the two atria (right to left, right actually contracts a tiny bit faster than the left) causing them to contract simultaneously

Electrical stimulation is prevented from spreading to the ventricles by a thin layer of connective tissue which acts as an electrical insulator (important that ventricles doe not start to contract uncle the muscles of the atria have finished contracting)

Short delay of (0.1 sec) and the nerve impulses reaches the AVN which lies between the two atria, this passes the impulse to the ventricles

From the AVN the impulse is passed down to the Bundle of His to the apex of the heart > Bundle branches into Purkinje fibres in the ventricle walls which carry the wave of excitation through the ventricle muscle

Impulses cause the cardiac muscle in each ventricle to contract simultaneously from the apex upwards