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The thorax

1) The thorax is the top part of your body
2) The thorax is separated from the lower part of the
body by the diaphragm
3) The lungs are protected by the ribcage and surrounded by the pleural membranes
4) The air that you breathe in goes through the trachea which splits into 2 bronchi, one going left and one right
5) The bronchi split into progressively smaller tubes called bronchioles
6) The bronchioles end at small bags called alveoli where more gas exchange takes place


What happens to the ribcage when you breathe in ?

Rib cage moves up and outwards as the external intercostal muscles contract and the internal intercostal muscles relax


What happens to the rib cage when you breathe out?

Rib cage moves in and down as your external intercostal muscles relax and internal intercostal muscles contract


What happens to the diaphragm when you breathe in?

Contracts and moves down


What happens to the diaphragm when you breathe out?

Relaxes and moves up


What happens to the volume in the thorax when you breathe in?

Volume in the thorax increases


What happens to the volume in the thorax when you breathe out?

Volume in the thorax decreases


What happens to the pressure inside the thorax when you breathe in?

Pressure decreases to draw air in


What happens to the pressure inside the thorax when you breathe out?

Pressure increases to push air out


Why is the bell jar model of the lungs inaccurate?

The scale of the model is inaccurate and the glass wall representing the ribs does not expand or contract


How does gas exchange take place?

1) The lungs contain millions of air sacs called alveoli where gas exchange takes place
2) The blood next to the alveoli has just returned to the lungs from the rest of the body so it contains lots of carbon dioxide and little oxygen. This means oxygen can diffuse out of the alveoli into the blood (from high concentration to low concentration) and vice versa for carbon dioxide
3) When the blood reaches body cells, oxygen diffuses into body cells from red blood cells (high to low concentration) and carbon dioxide diffuses from the body cells into the blood


How are alveoli specialised for gas exchange?

1) The huge number of microscopic alveoli gives the lungs enormous surface area
2) There's a moist lining for gases to dissolve in
3) The alveoli have walls that are 1 cell thick so the gas doesn't have far to diffuse
4) They have good blood supply to maintain high concentration gradient
5) The walls are permeable so gases can diffuse across easily


What problems does smoking cause in the lungs?

1) Damages the walls of the alveoli reducing surface area available for gas exchange and leading to diseases such as emphysema
2) The tar in the cigarettes damage the cilia in the lungs and trachea. Cilia and mucus are used to catch and sweep away dust and bacteria before the reach the lungs and keep the trachea clear. When cilia are damaged chest infections are more likely.
4) Tar also irritates the bronchi and bronchioles which causes more mucus to be produced but is unable to be cleared by damaged cilia which can cause smoker's cough and chronic bronchitis


How does smoking damage the circulatory system?

1) Carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry which reduces aerobic respiration and to make up from this heart rate increases which causes an increase in blood pressure.
2) High blood pressure damages the artery walls making the formation of blood clots more likely which in turn increases the risk of coronary heart disease.