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Respiratory System

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Chris Softley

on 26 September 2018

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Transcript of Respiratory System

Respiratory System
Learning Objectives:
Understand the structure and function of the respiratory system
Know the function of the respiratory system and how it adapts to physical activity
Assessment Criteria:
P6 - Describe the structure and function of the respiratory system
M3 - Explain the function of the respiratory system
Structure of the respiratory system:
Air is drawn in to the body via the nose or the mouth
Known as the respiratory tract - divided into two main parts
The upper respiratory tract
The lower respiratory tract
Upper Respiratory Tract
Nasal cavity
Lower Respiratory Tract
Label the lungs
Nasal Cavity:
Divided into two parts - external nose and the internal nasal cavity
Air passes through the nostrils
Hairs in the cavity filter out dust, pollen and other foreign substances before the air passes into the two parts of the nasal cavity
The air is then warmed and moistened before it passes into the nasopharynx
A sticky mucous layer traps smaller foreign particles, which tiny hairs called cilia transport to the pharynx to be swallowed.
Small flap of cartilage at the back of the tongue
Closes the top of the trachea when you swallow
Stops food and drink from passing into your lungs
Pharynx - Throat
Connects nasal cavity and mouth to the larynx (air) and oesophagus (food)
Small tube - 10-13cm from base of the skull to the level of the sixth cervical vertebra
Pharynx is composed of skeletal muscle
Passageway for food and air
Special adaptations to prevent choking from food and liquid
Voice box
Rigid walls of muscle and cartilage
Contains vocal cords
Connects Pharynx to the Trachea
5cm from the level of the third to sixth vertebra
Sometimes call the windpipe
Start of the lower respiratory tract
12cm long by 2cm wide
Contains rings of cartilage to prevent from collapsing
Very flexible
Located down the front of the neck
In front of the oesophagus
Branches into the right and left bronchi
Splits the trachea into two parts
Carries air to the lungs
Right bronchus is wider and shorter than the left
Usually warm, clear air reaches the bronchi
Each bronchus subdivides into lobar bronchi - 3 on the right and 2 on the left
Lobar bronchi branch into segmental bronchi which divide again into smaller and smaller bronchi
Overall 23 orders of branching bronchial airways in the lungs
This is often called the bronchial tree
Small airways which extend from the bronchi
1mm in diameter
First airway that branches of the respiratory system that does not contain cartilage
Bronchioles end in thin-walled air sacs, known as alveoli
Occupy most of the thoracic cavity
Extend down to the diaphragm
Hang suspended in the right and left plural cavities
Left lung is smaller than the right
Each lung is divided into lobes
Right lung has 3 lobes
Left lung has 2 lobes
Pleural membrane and cavity
Lungs are surrounded by membranes known as pleura
Fluid lubricates the pleural surfaces
This helps prevents friction when the lungs expand and contract
Keeps them airtight
Thoracic Cavity
Chamber of the chest protected by the thoracic wall
Separated from the abdominal cavity by the diaphragm
Visceral pleura
The innermost of the two pleural membranes
Covers the surface of the lungs
Dips into the spaces between the lobes
Pleural fluid
Pleural membranes produce pleural fluid which fills the space between them
Allows lungs to glide easily over the thoracic wall during respiration
Membranes are separated due to surface tension of the pleural fluid that keeps the lung surface in contact with the chest wall
Air sacs at the end of the bronchioles
300 million gas filled in each lung
Creates a massive area for gaseous exchange
The size of a tennis court
Capillaries surround the alveoli
Gaseous exchange occurs rapidly by diffusion across the respiratory membrane
Oxygen passes from the alveoli into the blood
C02 passes from the blood into the alveoli
Separates the chest from the abdomen
Most important muscle involved in breathing
Contraction of the diaphragm increases volume of the chest cavity
Draws air into the lungs during respiration
Relaxation involves recoil of the diaphragm and decreases the volume of the chest cavity, pumping out air.
Internal and External Intercostal muscles
Lie between the ribs
Help inhalation and exhalation
They extend and contract
Internal Intercostal muscles
lie inside the rib cage
Draw the ribs downwards and inwards
Decrease the volume of the chest cavity
Forces air out of the lungs during expiration
External Intercostal muscles
Lie outside of the rib cage
Pull the ribs upwards and outwards
Increases the volume of the chest cavity
Draws air into the lungs during inspiration
Functions of the respiratory system
Gaseous Exchange
Diffusion between air in the alveoli and blood in the capillaries
Partial pressure applies to the diffusion of the gasses from a gas mixture to a gas in solution
Gasses dissolve into a liquid solution by diffusion until equilibrium is achieved
At Equilibrium, partial pressure of the gases is the same in both gaseous and liquid state
Blood from the pulmonary arteries has a lower oxygen content and a higher CO2 content than the air in the alveoli
Mechanisms of breathing
The process:
Oxygen diffuses into the blood via the surface of the alveoli
This happens through the thin walls of the capillaries through the red blood cell membrane
Oxygen then latches onto haemoglobin
CO2 diffuses in the opposite direction from the blood to the alveoli
Pulmonary Ventilation - How air is transported into and out of the lungs
Considered to have two phases
Breathing is regulated by the respiratory centres in the brain and stretch receptors within the air passages and lungs
Requires the thorax to increase in size to allow air to be taken in
Decrease of the thorax forces air out
Intercostal muscles contract to lift the ribs upwards and outwards
Diaphragm is forced downwards
Sternum goes forwards
Expansion of the thorax causes a drop in pressure below atmospheric pressure
Enables air to flow into the lungs
Oxygen is exchanged for CO2 through the capillary walls
Happens after inspiration
Intercostal muscles relax
Diaphragm extends upwards
Ribs and sternum collapse
Pressure in the lungs is increased
Air is expelled
During exercise greater amounts of oxygen is required meaning the intercostal muscles and diaphragm have to work harder
Lung Volumes
Respiratory rate is the amount of air your breathe in 1 minute
18 year old = 12 breaths per minute at rest
This equals 6 litres of air passing through the lungs
Increases significantly during exercise to about 30-40 breaths per minute
Tidal Volume
Amount of air breathed in and out in 1 breath
Normal conditions = 500cm3 of air breathed (inhaled and exhaled)
Approximately 2/3's (350cm3) reaches the alveoli
The remaining 150cm3 fills the pharynx, larynx, trachea, bronchi and bronchioles (known as dead or stationary air)
During exercise tidal volume increases
Amount of air passing through the lungs in 1 minute is called minute volume
Lungs also usually contain 2,500cm3 of air that has already undergone gaseous exchange with the blood
Inspiratory reserve volume
Breathing in deeply means that you can inhale more than the usual 350cm3 of fresh air
Especially important during exercise
As well as tidal volume, you can inhale up to an additional 3,000cm3 of fresh air
Known as inspiratory volume
Expiratory reserve volume
can be up to 1500cm3
amount of additional air that can be breathed out after normal expiration
The lungs contain residual volume and expiratory reserve volume after a normal breath
If you then exhale as much as possible, only the residual volume remains
Vital capacity
Amount of air forced out of the lungs after maximal inspiration
Around 4,800cm3
Residual Volume
Lungs are never fully emptied of air otherwise they would collapse
This is the air that is left in your lungs after maximal expiration (breathing out as hard as you can)
Around 1200cm3 for an average male
Total lung capacity
After your have inhaled as deeply as you can
Normally around 6,000cm3 for an average sized male
Control of breathing
Neural control
Involves neurones
Cells that conduct nerve impulses
Neurones in two areas of the medulla are critical in respiration
Dorsal respiratory group (DRG)
Ventral respiratory group (VRG) - thought to be responsible for the rhythm generation of respiration
Chemical Control
Continually changing levels of oxygen and CO2
Different sensors respond to to chemical fluctuations within the body when exercising
These can be found in the medulla oblongata, aortic arch and carotid arteries
Detect chemical fluctuations within the body
pH levels changing due to the body working at higher intensities.
Detect changes in blood pressure
Detect a change in temperature
Detect movements in the body
Prevents over inflation of the lungs
Additional key receptors in the body that helps increase respiratory rate and prepare the body for exercise.
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