Human Breathing - Chp 30

Respiratory system diagram

Thorax - structure

consist of the lungs, thoracic cavity and a series of tubes

Diaphragm - structure

a sheet of muscle that forms the floor of the thorax

Intercostal muscles - structure

located between each of the ribs + makes up the walls of the thorax together

Nasal passages - structure + function

• has 2 openings called nostrils separated by a nasal septum

• walls lined with fine hairs and mucous which trap and filter the air

• moistens and warms the air to help it diffuse more easily in the alveoli

Pharynx - structure

passage at the back of the mouth that connects the mouth and larynx

Epiglottis - structure + function

• a flap of tissue that closes off the trachea when we swallow

  • this prevents food entering the windpipe

Larynx - structure + function

• found just below the epiglottis, also known as the voice box or Adam’s apple

• contains 2 vocal cords that vibrate to produce sound when air passes over

Glottis- structure + function

area at the top of the trachea that contains the larynx and vocal cords

Trachea, Bronchi + Bronchioles - structure + function

Trachea, bronchi and higher bronchioles are all made up of muscle and elastic fibres with incomplete C shaped rings of cartilage - these prevent the tubes from collapsing as air is taken in

• trachea allows air to pass to the lungs

• trachea divides into 2 bronchi transporting the air into each lung

• each bronchus divides into bronchioles which transport air into the alveoli

Cilia - structure + function

• hair like projections that line the trachea, bronchi and bronchioles - mucous producing cells also line these structures

• the mucous traps particles and the cilia beat to create an upward current to move these particles up to the oesophagus where they are swallowed

Alveoli - structure + function

• hollow, balloon like sacs at the end of each bronchiole

• about 700 million in 2 lungs

What adaptations are there to imrpove gas exchange in the lungs?

• alveoli are numerous

• alveoli have thin walls

• alveoli are moist and warm

• covered in capillaries that have thin walls

• capillaries are numerous

all increase surface area

Lungs - structure + function

• large spongy organs where gas exchange occurs

Pleural membrane - structure + function

aka Pleura

• outer membrane lines the chest wall and diaphragm

• inner membrane lines the lung

• the gap between the membranes is the pleural cavity + is full of liquid, which lubricates the membranes preventing friction

Diffusion

movement of molecules from an area of high concentration to an area of low concentration

Describe the process of gas exchange:

O₂

• blood returning to the lungs is rich in CO₂ and low in O₂

• O₂ will diffuse into through the alveoli wall and capillary to the blood as the concentration is lower and the concentration in the alveolus is higher

CO₂

• CO₂ and water diffuse through the capillary and alveoli wall out of the blood as the concentration in the alveolus is lower and the concentration in the blood is higher

• they are then exhaled

How are gases transported around the body?

O₂

• 97% of O₂ combines with haemoglobin and 3% is dissolved in the plasma

• travels to the pulmonary vein, into the heart, and then is pumped around the body

CO₂

• CO₂ and water are transported in the plasma

What factor controls breathing?

CO₂ levels

How do CO₂ levels control breathing?

• CO₂ is a slightly acidic gas, and dissolved in water to form weak carbonic acid

• this causes the pH of blood to fall slightly

• cells in the medulla oblongata in the brain detect the slightly drop in pH

• nerve cells in the medulla oblongata are connected to the diaphragm and intercostal muscles

• when CO₂ levels are high, pH drops and nerve impulses are sent to the diaphragm and intercostal muscles

Describe the process of inhalation:

• an impulse is sent from the medulla oblongata to the intercostal muscles and diaphragm - muscles contract making this an active process

• the intercostal muscles contract moving the ribs up and out

• the diaphram contracts pulling down

• this increases the size of the thorax

• increase lung volume

• deacreases thoracic pressure

• external pressure is now higher than the thorax and air is forced into the lungs

Describe the process of exhalation:

• no message is sent to the intercostal muscles and diaphragm and they relax - passive process no ATP required

• intercostal muscles move down and in

• diaphrahm moves up

• this reduces the size of the thorax

• decreases lung volume

• increases thoracic pressure

• external air pressure is lower than thoracic pressure and air is forced out of the lungs

How does exercise effect rate of breathing?

• increases rate of respiration as muscle cells need more O₂ and also increases CO₂ levels

• this triggers deeper and faster breathing to gain more oxygen and remove carbon dioxide

• exhalation become an active process

Name a breathing disorder + what problems it causes

Asthma - the narrowing of the lower bronchioles, which prevents air from reaching the alveoli

Symptomms, causes, prevention and treatment of the named breathing disorder:

• Symptoms: Noisy, wheezy breathing and a feeling of breathlessness

• Causes: Triggered by external allergens that are inhaled e.g. pollen or dust

• Prevention: Avoid allergens and preventative inhalers (bronchodilator)

• Treatment: Use a bronchodilator which widens/dilates the bronchioles