3.2 - Transport in animals

What are the 3 main factors that influence the need for a transport system?

Size, surface area to volume ratio and level of metabolic activity.

Define double circulatory system

One in which the blood flows through the heart twice for each circuit of the body

Define single circulatory system

One in which the blood flows through the heart once for each circuit of the body

What is the passage of the double circulatory system?

heart, body, heart, lungs, heart

What are the advantages of a double circulation?

Lower pressure blood reaches the lungs to become oxygenated. The left ventricle contracts with more force to create greater pressure for oxygenated blood to be delivered to the rest of the body. Oxygenated and de-oxygenated blood do not mix.

Why must the blood pressure not be too high in the pulmonary circulation?

It could damage to delicate capillaries in the lungs.

Why does the heart increase the blood pressure after it has passed the lungs?

So that the blood is under higher pressure as it flows to the body and it flows more quickly

Define arteries

vessels that carry blood away from the heart

Define arterioles

small blood vessels that distribute the blood from an artery to the capillaries

Define capillaries

The smallest blood vessels, which deliver oxygenated blood to the body's tissues and carry away deoxygenated blood

Define closed circulatory system

Blood is enclosed within vessels/diffusion of substances only takes place within vessels

Define open circulatory system

A circulatory system with a heart but few blood vessels to contain the transport medium. The blood vessels open up to a pool of blood called the haemoceol

Define veins

Blood vessels that carry blood back to the heart

Define venules

small blood vessels that collect blood from the capillaries and lead into the veins

What are the disadvantages of open circulatory systems?

Blood pressure is low and blood flow is slow and circulation of blood may be affected by body movements or lack of body movements

What are the advantages of closed circulatory systems?

Higher pressure, more rapid delivery of oxygen and nutrients, rapids removal of carbon dioxide and other wastes and transports is dependent of body movements

What is endothelium?

Simple squamous tissue that lines blood vessels and the heart that reduces friction

What are arteries?

Blood vessels that carry blood away from the heart

What are the features of arteries?

1. They have thick, muscular walls which helps maintain pressure
2. They have elastic tissue to help recoil the artery after the blood flows through it
3. The endothelium is folded to allow it to stretch which maintains high pressure.

How many layers are in artery walls?

3 layers; inner, middle and outer layer

What is the inner layer of the artery?

It consists of a thin layer of elastic tissue which allows the wall to stretch and then recoil to help maintain blood pressure

What is the middle layer of the artery?

A thick layer of smooth muscle

What is the outer layer of the artery?

A thick layer made from collagen and elastic tissue, providing strength to withstand the high pressure and recoil to maintain the pressure

How are arterioles adapted to their function?

They contain a layer of small muscles which contracts, constricting the diameter of the arteriole. This increases the resistance to flow and reduce the rate of the flow of blood.

Define capillaries

The smallest blood vessels, which deliver oxygenated blood to the body's tissues and carry away deoxygenated blood

What are the features of capillaries?

They are only 1 cell thick to reduce diffusion distance in areas such as the alveoli. There are large numbers of capillaries in capillary beds to increase surface area. They are always found very close to tissues.

Why is the capillary lumen narrow?

Red blood cells are squeezed against the walls as they pass. This helps the transfer of oxygen as it reduces the diffusion paths. It also increase resistance and reduces the rate of the flow

What does the capillary consist of and what does it do?

It has a single layer of flattened endothelial cells and it reduces resistance and reduces the rate of flow

Define venules

a very small vein, especially one collecting blood from the capillaries.

What does the venule wall consist of?

thin layers of muscle and elastic tissue outside the endothelial and a thin outer layer of collagen

Define veins

Blood vessels that carry blood back to the heart

What are the features of veins?

Large lumen, thin muscle wall, little elastic tissue and valves

Why is the lumen larger in veins?

To ease the flow of blood

Why do the veins have thinner layers of collagen, smooth muscle and elastic tissue?

Because they do not need to stretch and recoil and are not actively constricted in order to reduce blood flow

What do the valves in the veins do?

Valves in the veins prevent blood backflow and most are located in smaller, more distal veins

Define blood

the fluid used to transport materials around the body

Define hydrostatic pressure

As blood moves along the capillary, fluid moves out through its pores and into the interstitial space.

Define lymph

the fluid held in the lymphatic system, which is a system of tubes that returns excess tissue fluid to the blood system

Define Oncontic pressure.

the pressure caused by the osmotic effects of the solutes

Define plasma

liquid portion of blood

Define tissue fluid

A fluid surrounding cells that is formed from blood plasma without large proteins

What is the other name for red blood cells?

erythrocytes

What is the other name for various white blood cells?

leucocytes

What are the components of blood?

plasma, red blood cells, white blood cells, platelets

How is tissue fluid formed?

by plasma leaking from the capillaries and it surrounds the cells in the tissue and supplies them with the oxygen and nutrients they require.

What happens when blood plasma leaks from the capillaries?

It carries all the dissolved substances into the tissue fluid and the movement is mass flow rather than diffusion. Waste products from cell metabolism will be carried back into the capillary as some of the tissue fluid returns to the capillary

What happens when an artery reaches the tissue? ( formation of tissue fluid )

It branches into smaller arterioles and then into a network of capillaries and they eventually link up with venules to carry blood back to the veins. Therefore blood flowing into an organ or tissue contained in the capillaries

What happens at the arterial end of a capillary? ( formation of tissue fluid )

The blood is at high hydrostatic pressure and it tends to push the blood fluid out of the capillaries through the capillary wall. The fluid can leave through the tiny gaps between the cells in the capillary wall

Which substances can leave through the capillary wall? ( formation of tissue fluid )

The fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen. All the red blood cells, platelets and most of the white blood cells remain on the blood as do the plasma proteins, as they are too large.

Why does the tissue fluid surround the body cells? ( formation of tissue fluid )

So that the exchange of gases and nutrients can occur across the plasma membranes. The exchange occurs by diffusion, facilitated diffusion and active uptake

Returning to the blood

The blood pressure at the venous end of the capillary is lower, allowing some of the tissue fluid to return to the capillary carrying waste products.

Not all tissue fluid re-enters the blood

Some tissue fluid is directed into another tubular system called the lymph system and it drains excess fluid out of the tissues and returns it to the blood system in the subclavian vein in the chest

What does high hydrostatic pressure do?

Blood plasma - high
Tissue fluid - low
Lymph - low

What does oncotic pressure do?

Blood plasma - more negative
Tissue fluid - less negative
Lymph - less negative

What cells are in blood plasma?

red blood cells, neutrophils

What cells are in tissue fluid?

some neutrophils especially in affected areas

What cells are in lymph?

lymphocytes

What proteins are in blood plasma?

plasma proteins

What proteins are in tissue fluid and lymph?

few proteins

What does the hydrostatic pressure of the blood do?

It tends to push fluid out into tissues

What does the hydrostatic pressure of the tissue fluid do?

Pushes fluid into the capillaries

What does the oncotic pressure of the blood do?

pull water back into the blood (negative figure)

What does the oncotic pressure of the tissue fluid do?

pulls water into the tissue fluid

What are the external features of the heart?

It mainly consists of cardiac muscle and there are 2 main pumping chambers called ventricles, and above it is the atria

Where are the coronary arteries?

outside the heart

What do the coronary arteries do?

supply blood to the heart

What may cause angina or a heart attack?

Restricted blood flow to the heart muscle reduces the delivery of oxygen and nutrients such as fatty acids and glucose

How many chambers are in the heart?

4 chambers

What are the 4 chambers in the heart?

right atrium, right ventricle, left atrium, left ventricle

What is the atria?

The upper chambers of the heart that receive blood from the major veins

What is the passage of deoxygenated blood?

It goes to the vena cava then into the right atrium, through the right ventricle and out the pulmonary artery.

What is the passage of oxygenated blood?

It enters in the pulmonary vein and enters the left ventricle then exits out the aorta

Draw the internal structure of the heart

What does the septum do?

divides the heart into right and left sides

What are tendinous cords?

attached to valves to prevent them from turning inside out when ventricle walls contract

What are the different parts of the heart?

semi-lunar valve, aorta, pulmonary artery, atrium, atrio-ventricular valve, ventricle and ventricular septum

The atria

The muscle of the atrial wall is very thin because these chambers do not need to create much pressure. Their function is to receive blood from the veins and push it through the ventricles

The right ventricle

The walls of the right is thicker than the walls of the atria. This enables the right ventricle to pump deoxygenated blood out to the lungs.

The left ventricle

The walls are 2 or 3 times thicker and the blood from the left is pumped out through the aorta and need sufficient pressure to overcome the resistance of the systemic circulation

What is the cardiac cycle?

The period from the end of one ventricular contraction to the end of the next ventricular contraction.

What is the ventricular systole?

contraction of ventricles

What is the diastole?

Relaxation of the heart

What is atrial systole?

contraction of the atria

Step 1: Atrial contraction

Signal starts at the sinoatrial
node (SAN)
It has inherent rhythmical
contraction, and triggers
cardiac impulses.
Impulses pass across the atria
causing the atria to contract
Signal reaches the
atrioventricular node (AVN)

Step 2: signal atria 🡪 ventricles

The sinoatrial node (SAN) is
also known as the pacemaker
The atria and ventricles are
separated by bands of
non-conducting tissue.
The atrioventricular node
(AVN) is the only gap in these
tissues through which the
signal can pass. This causes a
slight delay atria 🡪 ventricles

Step 3: Ventricular contraction

Signal at the AV node
Electrical impulses are passed
down inter-ventricular bundles.
These are called the Bundle
of His.
The bundles separate into
Purkinje (Purkyne) fibres
which pass the electrical
impulse up the ventricles from
the apex (bottom) upwards.

Describe the process of diastole

Both atria and ventricles relaxed and pressure decreased. Internal volume increases, blood flows into heart from major veins and blood flows into atria, then through open atrioventricular valves
and into ventricles
'Filling phase'
Atria and ventricles have blood inside of them

Describe the process of atrial systole

Both atria contract together, small increase in pressure created by contraction helps to
push blood from atria into already partially full ventricles.
Stretches walls of ventricles, ensures that they are already
full of blood and AV valves then shut

Describe the process of ventricular systole

Ventricles full of blood, begin to contract and as pressure increases, volume decreases.
Contractions start at apex, pushing blood upwards towards
arteries. Semi-lunar valves forced open
Blood pushes out of both ventricles and into the arteries
Semi-lunar valves shut

atrioventricular valves

Valves located between the atrial and ventricular chambers on each side of the heart, prevent backflow into the atria when the ventricles are contracting.

semilunar valves

pulmonary and aortic valves located between the right ventricle and the pulmonary artery and between the left ventricle and the aorta

Draw pressure changes in the heart

Pressure in blood vessels

decreases as distance from the heart increases

What does the 1st bump mean in the cardiac cycle?

AV Valve closes

What does increase in aortic pressure mean in the cardiac cycle?

Aortic valve opens

What does the peak mean in the cardiac cycle?

The wave of arterial pressure

What does decrease in aortic pressure mean in the cardiac cycle?

Aortic valve closes

As soon as ventricular pressure falls below atrial pressure,.....

The atrioventricular valve opens and blood flows passively from atria into ventricles

What is ECG/EKG?

it is an electrocardiogram, which is a graphical recording of the electrical events occurring within the heart

Of the PQRST wave, what does the P wave represent?

P wave represents the impulses passing from the SAN to the AVN through the walls of the atria.