Exchange surfaces - ventillation + heart

Inspiration

• External intercostal muscles and diaphragm contract

• Causes diaphragm to flatten moving rib cage upward and outward

• Volume of the thorax now increases

• This decreases lung pressure - below atmospheric pressure

• Causing air to flow into the lungs

Why does inspiration considered active

• Requires energy

• Muscle contraction

Expiration

• External intercostal muscles and diaphragm relax

• Causes rib cage to move downward and inward causing diaphragm to curve

• Volume of the thorax decreases - increases lung pressure above atmospheric pressure

• Forcing out air from lungs

Vital capacity

Maximum volume of air an individual can inhale and exhale in one deep breath

Tidal volume

The air inhaled and exhaled while at rest

Residual volume

Volume of air that stays in lungs so they do not collapse

Breathing rate

Number of breaths taken per minute

Stroke Volume

Volume of blood cm3 pumped by the heart in 1 minute

Hear Rate

Number of heart beats per minute

Cardiac Output Stroke

Stroke volume x heart rate

Why is expiration considered passive

• No muscle contraction

• No recoil of tissue

What is the septum?

• The septum is the wall between the left and right sides of the heart

• Septum prevents the mix of oxygenated and deoxygenated blood from different sides of the heart

How do valves work?

• Open when the pressure of blood behind them is greater than the pressure in front of them

• Close when the pressure of blood in front of them is greater than the pressure behind them

Why are valves important?

• Prevent backflow of blood into the wrong chamber

• Maintains correct pressure of blood in chambers

How are the right atrium and right ventricle separated

• By the tricuspid valve

How are the left atrium and left ventricle seperated

• By the bicuspid valve

How is the right ventricle and the pulmonary artery separated

Semi lunar valve

How is the left ventricle and aorta seperated

Semi lunar valve

Why is left ventricle wall thicker?

• Enables stronger contractions

• Generating a higher blood pressure

• To push blood over a longer distance to the whole body rather than just the lungs in the right ventricle

Deoxygenated blood

Vena cava carries deoxygenated blood -—> right atrium -—> tricuspid valve —-> right ventricle -—>semi lunar valve ——> pulmonary artery (heart to lungs)

Oxygenated blood

Pulmonary vein carries oxygenated blood ——> left atrium ——> bicuspid valve ——> left ventricle —->semi lunar valve —-> aorta

Aorta adpatation

• Very elastic to recoil and withstand a high blood pressure from heart

• Sends oxygenated blood to rest of the body

How does Blood flow

High pressure —→ low pressure

How does contraction change pressure

Increases pressure

How does relaxation change pressure

Decreases pressure

Why is the heart described as myogenic

• Cardiac muscle can initiate its own contractions

Where are AV and SV node found

In right atrium

What is the role of the AV node

• AV node delays impulse

• Allows atria to fully contract so all blood enters ventricles

• Prevents ventricles contracting at the same time as atria - which would result in not all blood entering ventricles before pumped out

• Blood will go from ventricles to aorta/ pulmonary artery

• Not all blood would be pumped out

Role of bundle of his

Transports impulse

Why is there not ventricular systole in bundle of His

• Has an insulating layer

• Ventricular walls are not affected by impulse

• Do not contract

Why does heart contract from apex

• Ensures that all blood is squeezed out of the hurt

Artery lumen

• Artery lumen is smaller

• This is because artery wall is much thicker than a vein

Vein lumen

• Veins lumen is bigger and irregular shape

• Thinner wall

Muscular layer artery

• Much thicker in arteries compared to veins - so can constrict and dilate to control volume of blood pumped out of heart

Muscular layer vein

Thin - cannot control blood flow

Elastic layer artery

• Much thicker - maintain blood pressure

• Stretch and Recoil in response to heart beat

Elastic layer - veins

• Veins carry blood at a much more low pressure

• Thin elastic layer

Wall artery

Much thicker in the artery - prevent vessels bursting at high pressures

Valves - artery

No valves

Veins artery

Have valves

Capillary

• One cell thick

• Only red blood cells can just fit through diameter of lumen

• Blood flow is slower in capillaries

• More time for diffusion

Arterioles - muscular wall

• Connect arteries to capillaries

• Much thicker muscular layer than arteries

• Restrict blood flow before capillaries

• Decreases pressure of blood going into capillaries

• As this could damage capillaries

Arterioles - Elastic layer

• Thinner as does not need to recoil and stretch to withstand high pressures

• Low pressures

Arterioles - Wall thickness

Thinner as pressure is lower

Arterioles - valves

No valves

Capillaries - elastic layer

No elastic layer

Capillaries - muscle layer

No muscle layer

Capillary wall thickness

• One cell thick - short diffusion distance

• Slows blood so more diffusion can occur