WJEC AS Biology - Unit 2.3 Adaptations for Transport

Types of circulatory system

• Open

• Closed

Open circulatory systems

• Blood is not carried around the body in blood vessels

• Blood bathes tissues directly while held in a cavity, allowing oxygen to be transported/delivered directly to respiring cells

• Oxygen diffuses directly to cells from tracheoles so blood does not need oxygen → no respiratory pigment

Advantages of open circulatory systems

Less energy needed to pump the transport medium

Disadvantages of open circulatory systems

• Substances are transported at lower pressures and therefore transported slower

Example of open circulatory systems

Insects

Circulatory system of insects

• Open circulatory system

• Long, dorsal tube-shaped heart running length of body

• Heart pumps blood → haemocel (cavity), where materials are exchanged between the blood and body cells

• Blood returns slowly to the heart and open circulation starts again

• Lack of respiratory gases and respiratory pigment in blood as oxygen diffuses directly from tracheoles so blood does not need oxygen

Closed circulatory systems

• Blood is carried in vessels (VASCULARISATION) to transport molecules/substances to and from exchange surfaces/tussues

• Pumps/hearts used to pump blood

• No direct contact with cells therefore resp pigment needed to carry respiratory gases in the blood

Advantages of closed circulatory systems

Blood pumped at higher pressure so blood travels at greater velocities, delivering oxygen and materials quickly to respiring cells

Disadvantages of closed circulatory systems

Contraction of a pump requires a large amount of energy

Types of closed circulatory systems

• Single

• Double

Single closed circulatory systems

Blood passes through the heart once in a single circuit around the body

Advantages of single closed circulatory systems

• Requires less energy to operate the single pump than a double pump

• Less complex single pump therefore less likely to have issues with values as exposed to lower pressures

Disadvantages of single closed circulatory systems

Lower pressure transporting oxygen to respiring cells → less velocity to blood → transporting oxygen to cells more slowly

Examples of single closed circulatory systems

• Fish

• Earthworms

Circulatory system of fish

• Single closed

• Ventricle of heart pumps deoxygenated blood → gills, where capillary network reduces it pressure

• Oxygenated blood returns to atrium of heart

• Blood moves to ventricle and circulation starts again

Circulatory system of earthworms

• Respiratory gases carried

• Blood moves forward in the dorsal vessel and back in the ventral vessel

• 5 pairs of pseudohearts (thickened, muscular blood vessels) pump blood from dv to vv

Double closed circulatory systems

• Blood passes through the heart twice in its circuit around the body

• Fastest type of delivery

• Cells are more metabolically active and mammals need to maintain a constant body temperature

Advantages of a double closed circulatory systems

• High pressure → fast delivery

• Blood is repressurised when it leaves the gas exchange surface, giving a faster and more efficient circulation to the tissues

Disadvantages of a double closed circulatory system

• Require lots of nerve transmission → requires lots of ATP

• Issues with valves due to higher pressure

• Contraction requires a lot of energy

Example of closed double circulatory system

Mammals - Blood pigment; haemoglobin

Types of circulation in mammals

• Pulmonary

• Systemic

Pulmonary circulation

• Serves the lungs

• Right side of the heart pumps deoxygenated blood to the lungs

• Oxygenated blood returns from the lungs to the left side of the heart

Systemic circulation

• Serves the body tissues

• Left side of heart pumps the oxygenated blood to the tissues

• Deoxygenated blood from the body returns to the right side of the heart

Pathway of blood

• Heart

• Artery (pulmonary or aorta)

• Arteriole

• Capillary

• Venule

• Vein (Vena Cava or pulmonary)

Blood vessels

Artery, Arteriole, Capillary, Venule and Vein

Arteries

• adapted to carry blood at higher pressure

• Have thick tunic externa; contains collagen fibres. Resists overstretching under pressure

• Layer of muscle and elastic tissue = thick to provide elastic recoil aiding propulsion of blood and maintaining blood pressure

• Lumen is relatively small to the maintain the pressure of the blood

Function of arteries

Supply oxygenated blood to respiring organs in the body

Structure of arteries

• thick elastic walls; withstand higher pressures in arteries

• Lots of elastic fibres; allow the arteries to expand and then recoil, helping to maintain arterial blood pressures and maintain a continuous flow of blood (ELASTIC RECOIL)

• The smooth endothelial lining is undulating and elastic

• Tunic externa, thick and contains many collagen fibres; numerous collagen fibres in tunica externa prevents rupture

Diagram of arteries

Function of arterioles

• supply oxygenated blood to tissues/capillary beds.

• Narrowing (VASOCONSTRICTION) and widening (VASODILATION) regulates blood flow to tissues

• Increasing total surface arterioles, causes frictions slowing the blood and reducing the blood pressure

Arterioles

• similar in structure to arteries but have more muscle

• Construct and dilate to control the flow of blood to capillaries

Structure of arterioles

• thicker tunica media in comparison to arteries. Therefore had a greater proportion of smooth muscle; allows narrowing and widening. Allows regulation of blood flow to tissues Increasing tissues

Capillaries

• Consists of a single layer of endothelial cells

• Tissue rather than an organ

• Site of gas exchange; single layer of flattened cells gives a short diffusion path

Function of capillaries

Exchange of materials. This is where tissue fluid is formed

Structure of capillaries

• Structure of endothelial cells; reduces diffusion path, increasing the rate of exchange of substances

• Microscopic pores - generations; allow fluid to leave and return to the capillaries. The fluid will carry with it dissolved substances such as glucose and oxygen

Diagram of capillaries

Venules

Veins

Function of veins

Return deoxygenated blood to the heart

Structure of veins

• thinner walls as they do not need to withstand the higher pressures as pressure are lower, backflow of blood is a potential issue

• Contain semilunar valves; prevent backflow of blood

• Larger wider lumens; reduces friction, increasing the velocity of the blood

• The contraction of skeletal muscle close to the veins helps to return blood to the heart

Diagram of veins

Tunica intima

• innermost layer of blood vessels

• Single layer of endothelium

• In some arteries, supported by elastin-rich collagen

• Smooth lining, reducing friction, producing minimal resistance to blood flow

Tunica media

• middle layer

• Contains elastic fibres and smooth muscle

• Thicker in arteries than in veins

• Arteries, elastic fibres allow stretching to accommodate changes in blood flow and pressure as blood is pumped from the heart. Recoil, pushing blood on through the artery

• Contraction of smooth muscle regulates blood flow and maintains blood pressure as the blood is transported further from the heart

Tunica externa

Outer layer, containing collagen fibres which resist overstretching

External structure of the heart

Internal structure of the heart

Myogenic

Layers of blood vessels

• Tunica intima

• Tunica media

• Tunica externa

Function of atrioventricular valves

Function of semilunar valves

The cardiac cycle

• Sequence of events of one heartbeat

Stages of the cardiac cycle

• Atrial systole

• Ventricular systole

• Diastole

Atrial systole in the cardiac cycle

• Atrial walls contract to move blood further into the ventricles

• Blood pressure in the atria increases

• This pushes blood through tricuspid and bicuspid valves down into the ventricles, which are relaxed

• The AVVs are open as greater pressure in the atria than the ventricles

Ventricular systole in the cardiac cycle

• Ventricle walls contract from the bottom upwards

• Increase blood pressure in the ventricles

• The AVVs close as pressure greater in the ventricles than the atria

• The SLVs are open as pressure is greater in the ventricles than the arteries (pulmonary artery and aorta)

• The blood flows into the arteries (aorta and pulmonary artery)

Ventricular diastole in the cardiac cycle

• Ventricles are relaxed

• Volume of ventricles increases and so pressure in the ventricles falls

• Most blood flows passively into the heart as pressure is greater in PVs and VC than the heart

• Greater pressure in the arteries then the ventricles means the SLVs are shut

Cardiac cycle graph

X on cardiac cycle graph

Aorta

Y on cardiac cycle graph

Ventricle

Z on cardiac cycle graph

Atria

When the AVV closes in the cardiac cycle graph

When the SLVs open in the cardiac cycle graph

When the aortic valve opens on the cardiac cycle graph

Atrial systole on the cardiac cycle graph

Reason for the delay between atrial systole and ventricular systole

Ventricular diastole on the cardiac cycle graph

Sounds made in cardiac cycle graph

Electrical control of the heartbeat

Sino-atrial node

Atrio-ventricular node

Atrial systole (electrical)

Ventricular systole (electrical)

Ventricular diastole (electrical)

ECG

P wave on an ECG

QRS region on an ECG

T wave of an ECG

Irregularities in ECGs

Atrial fibrillation causes

Atrial fibrillation effects on normal heart function

Atrial fibrillation symptoms

Arrhythmia causes

Arrhythmia effects

Arrhythmia symptoms

Tachycardia causes

Tachycardia effects

Tachycardia symptoms

Pressure changes in the blood vessels

Pressure changes graph

Functions of blood

Composition of blood

Role of white blood cells

Role of red blood cells

How SA:Vol ratio of RBCs is increased

Why it is important that RBCs are flexible

How lack of a nucleus increases the RBC’s ability to transport oxygen

Benefits of small RBCs on efficiency of transport of oxygen

Adaptations of RBCs to low oxygen concentrations

Binding properties of haemoglobin

Affinity

Plasma