Download Parts of the respiratory system

Respiratory System
Why do we inhale oxygen and exhale carbon dioxide?
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Respiration takes place in every cell to supply them with energy. We use oxygen and produce
carbon dioxide and water in the process of respiration
Introduction
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Pair of lungs are located in the chest (thorax) region known as the thoracic cavity.
Ribs and intercostals muscles surround the thoracic cavity.
Diaphragm muscles form at the bottom of the thoracic cavity.
Air passes in and out of the lungs by the contraction of these muscles.
Parts of the respiratory system
Nose
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Air is inhaled in through the nose (nostrils)
Nostrils are separated by a nasal septum (made of cartilage)
Benefits of breathing through the nose:
1) Filter by hairs and mucous in the nose
2) Moistened
3) Warmed as it passes through the nasal passage
NOTE: Warm, moist air diffuses easily from the lungs into the blood stream.
Pharynx
 In the pharynx (throat) the epiglottis closes off the trachea (windpipe) when we swallow. This
prevents food from entering the windpipe and lungs.
 The larynx (voicebox) produce vibrations to create sound.
 Glottis is situated at the top of the windpipe.
Trachea, bronchi and the bronchioles
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These parts are all made from muscle and rings of cartilage.
NOTE: The rings of cartilage prevent these tubes from collapsing.
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When bronchioles become narrow c can cause an asthma attack.
All these tubes are lined with mucous and tiny hairs (cilia). These trap any dust, bacteria or
viruses.
NOTE: When we clear our throat it helps force mucous up and into the oesophagus and away from the
vocal cords.
Lungs
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Spongy material
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Gas exchange occurs here.
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Lungs are enclosed by a pair of pleura membranes.
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Pleural cavity is full of liquid which reduces friction on the lungs during breathing.
Alveoli
Function: to allow gas exchange
Each bronchus divides into millions of bronchioles.
At the end of each bronchiole you have an air sac called an alveoli (700 million).
Adaptions of alveoli
1. Large surface area for gas exchange as they are so numerous.
2. Thin walled (
) for easier gas exchange
3. Moist
4. Capillaries also have thin walls.
Gas exchange
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Carbon dioxide and water diffuses out of the cell and into the blood.
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The carbon dioxide and water then diffuse out of the blood and into the alveoli of the lungs
(from high to low concentration).
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Also, oxygen diffuses from the alveoli into the blood and then into the cells (from high to low
concentrations)
Transport of gases
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Oxygen is mostly transported (97%) by haemoglobin and 3% by the plasma.
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Carbon dioxide and water is carried by plasma.
Inhaled and exhaled air
Inhaled
Exhaled
21
14
% carbon dioxide
0.04
5.6
Water concentration
Low
High
% oxygen
Breathing disorders
Asthma
Cause – external:
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Triggered by allergens that are inhaled (pollen, scales from skin, house dust, dust mites)
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Stress or anxiety
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Exercise (especially in cold air)
Cause internal:
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Lower bronchioles become narrower during an asthma attack.
Prevention
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Avoiding allergens
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Preventative inhalers
Treatment
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Steroids inhaled
Control of human breathing
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The brain controls breathing by monitoring the levels of carbon dioxide in the blood.
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Carbon dioxide is slightly acidic when it dissolves in blood which lowers its pH.
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The brain detects this low pH and reacts by sending a message to the diaphragm and
intercostals muscles which causes us to breathe faster especially when we exercise.
NOTE: Our brain does not respond to low levels of oxygen but only to levels of carbon dioxide.
Therefore carbon dioxide operates as a controlling factor in gas exchange in both animals and plants
Mechanism of breathing
At rest the breathing rate is approx 15 times per minute.
Inhalation = breathing in
Exhalation = breathing out
Steps involved in inhalation:
1) A message is sent from the brain to diaphragm and intercostals muscles.
2) These muscles contract (active process)
3) Ribs are pulled up and out and diaphragm moves down.
4) The volume of the chest cavity (thorax) increases and the pressure in the chest falls (external air
pressure is higher than the pressure of air in lungs).
5) As a result air is forced into the lungs (inhalation).
Steps involved in exhalation:
6) The diaphragm and intercostals muscles relax.
7) Ribs move down and in, diaphragm moves up.
8) Volume of chest cavity (thorax) decreases and the thoracic pressure increases.
9) Air is forced out of lungs back into the air (passive).