Respiration

2 types of respiration

Internal and external

Pulmonary capillaries

Surround the alveoli

How many sets of branches in the lungs?

24

What are the 2 zones of the lungs?

Conducting and respiratory

What is the function of the conducting zone of the lungs?

Way of transporting gases into the respiratory zone

What makes up the conducting zone?

Nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles

What number branch is the bronchi?

11

What branch is the 0?

Trachea

What supports the bronchi?

Cartilage

What supports the bronchioles?

No cartilage
Rely on tissue around them and their elastic nature to keep them open
Much more subject to contraction

Why is it more efficient if we breathe through our nose?

Small hairs help filter and trap particles
As the air is moving through it creates a turbulent type condition - smaller particles are more likely to drop our or get trapped because of this

Why is it beneficial for air to warm to our body temperature?

Warming gas helps prevent the formation of bubbles

What can carry more gas warm or cold air?

Cold

What stops the lower airways from drying out?

As air passes through it becomes humidified and equilibrated with water vapour

What controls the contraction of bronchi?

Smooth muscle underneath the cartilage lining the outside of bronchi under the control of para/sympathetic innervation

Epithelia mucous gland

Secretes mucus onto surface of bronchi to help trap particles

Function of elastic tissue in the airways

Recoil and helps to support

Function of ciliated epithelium in the lumen of the airways?

Helps direct mucus out of the lungs towards the throat to move small particles out of the lungs

Goblet cells

Produce mucus

Function of sensory nerve endings between epithelial cells in bronchi and bronchioles

Help detect noxious chemicals in the airway e.g. smoke

Diameter of bronchioles

Less than 1mm

What keeps bronchioles open?

Tethering of tissue around them - elastic tissue connection helps keep them open

What breaks down in COPD?

The elastic tissue surrounding the bronchioles subjecting them to collapse

Why do the bronchioles have proportionally more smooth muscle cells compared to the bronchi?

Controlling the airway diameter is more important

How many alveoli?

300 million per lung

Surface area of alveoli?

100 m2

How many biological membrane does oxygen have to diffuse across?

5

Inspiration pressure gradients

Atmospheric pressre is greater than the pressure inside the alveoli so gas moves down the pressure gradient and into the lungs

Expiration pressure gradients

Pressure in alveoli is greater than atmospheric pressure so gas moves down the pressure gradient and out of the lungs

What is the primary muscle of inspiration?

Diaphragm

What muscles does quiet inspiration involve?

Primary

What happens to the diaphragm during inspiration?

Contracts and moves down

ICE ECI

Internal contract expiration
External contract inspiration

Boyle's Law

P1V1\=P2V2

What muscles are involved in forced inspiration?

Secondary muscles

Scalene muscle function in forced inspiration?

Attach to top of rib cage - contraction helps move the rib cage up and forward

Function of sternocleidomastoids in forced inspiration?

Attach to the sternum - and helps to lift the sternum up and forwards

What is the function of neck and back muscles during forced inspiration?

Pull pelvic girdle up

Function of elastic tissue in quiet expiration?

Recoil of the elastic tissue returns the lungs to their original size

Function of abdominal muscles in forced expiration?

Pull diaphragm up

Pleura

Double-layered membrane surrounding each lung

Parietal pleura

Outer layer of pleura lying closer to the ribs and chest wall

Visceral pleura

Inner layer of pleura lying closer to the lung tissue

Pleural cavity

Between parietal and visceral pleura

What is the pleural cavity filled with?

Serous fluid

Function of pleural cavity?

Allows lung and chest wall to move over each and prevent them from sticking together
Enables free expansion and collapse of lungs
Helps set resting lung volume

Pneumothorax

Collapsed lung - air in the pleural cavity
Intrapleural space is at atmopsheric pressure and so force keeping lungs inflated is lost
Elastic nature will take over and lungs will collapse

Is the pressure in the intrapleural space greater or less than atmospheric pressure?

Less

Compliance

Measure of how distensible the lungs are - how elastic they are

Concentration \=

Change in volume/ change in pressure

As you inspire, what happens to intrapleural pressure?

Becomes more negative

Low compliance

Large pressure chaneg and small volume change - more work needed to expand the lungs

Pulmonary fibrosis

Build up of structural tissue in the lungs - more rigid so harder to expand
Lower compliance of the lungs

High compliance

Small pressure change induces a large volume change

What can high compliance lead to?

Problems when expiring
Emphysema/COPD
Lost some elastic properties as a result of breakdown of tissue
Airways can collapse
Harder to breathe out

What are the 2 components of elastic recoil in the lungs?

Anatomical and surface tension

Surface tension in the lungs

Air/water interface - water molecules tend to be pulled into the body of water

Laplace's equation

P\=2T/r

What produces surfactant?

Type 2 pneumocytes

Surfactant

Chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing

What is surfactant composed of?

90% phospholipids and 10% proteins

How does surfactant prevent alveolar collapse?

Decreasing surface tension
Inncreasing compliance

How does surfacant affect rate of inflation?

SLows

Production of surfactant decreases and causes what?

Pneumonia

What happens to surfactant in pneumonia?

Production decreases

What does surfactant prevent?

Oedema
Reduces fluid entering alveoli

How are surface tensions balanced out between large and small alveoli?

Small alveoli have a higher density of surfactant compared to large

Dead space

Volume of lungs not involved in gas exchange

Anatomical dead space

Conducting zone volume - first 16 generations of airways

How much inspired air volume is dead space?

30%

At rest how many ml of air is in anatomical dead space?

150ml

Tidal volume

Amount of air we breathe in and out in one breath

Average tidal volume

500ml

Physiological dead space

Volume of lungs not participating in gas exchange
Conducting zone + non-functional areas of respiratory zone
Normally physiological dead space and anatomical dead space are almost identical

2 types of dead space in lungs

Anatomical and physiological

Vital capacity

Maximum amount of air we can breathe in and out

Residual volume

Amount of air remaining in the lungs after a forced exhalation

Total lung capacity

Residual volume + vital capacity

Forced expiratory volume

How much air can be forced out of the lungs in 1 second

Expiratory reserve volume

Amount of air that can be forcefully exhaled after a normal tidal volume exhalation

Vital capacity \=

TV + IRV + ERV

Inspiratory reserve volume

Amount of air that can be forcefully inhaled after a normal tidal volume inhalation

Functional residual capacity

Volume of air remaining in the lungs after a normal tidal volume expiration

FRC \=

ERV + RV

Inspiratory capacity

Maximum amount of air that can be inhaled after a normal tidal expiration

What happens to tidal volume during exercise?

Increases

What happens to IRV and ERV if tidal volume increases?

IRV and ERV must decrease

How to measure residual volume?

Helium dilution
Measure the helium concentration before and after

Relationship between flow of air and pressure gradient?

Flow of air is proportional to the pressure gradient

Relationship between flow of air and resistance?

Flow of air is inversely proportional to resistance

Poiseuille's Law

Airway resistance is proportional to gas viscosity and the length of the tube but is inversely proportional to the 4th power of the radius

Relationship between resistance and radius?

R \= 1/r^4

4 factors that impact on airway resistance

Airway diameter
Mucus secretion
Oedema
Airway collapse

How does mucus secretion affect airway resistance?

Increased mucus secretion will reduce airway diameter and increase resistance

How does oedema impact on airway resistance?

Increased fluid retention in lung tissue will cause swelling and narrowing of the airways increasing resistance

How does airway collapse impact on airway resistance?

Forced expiration - narrows airway - increased resistance

Parasympathetic control of the bronchial smooth muscle

ACh os released from the vagus nerve and acts on muscarinic receptors leading to constriction

Sympathetic control of the bronchial smooth muscle

Norepinephrine is released from nerves leading to dilation

How does epinephrine affect bronchial smooth muscle?

Leads to dilation

How does histamine affect bronchial smooth muscle?

Histamine is released during inflammatory processes and leads to constriction