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Unit 2A Human Form & Function Body systems The respiratory system
Further information Further information about this topic can be found in Our Human Species (3 rd edtn) Chapter 11, sections 1-2, 4-6
Background reading Our Human Species (3 rd edtn.) Chapter 11, Gas Exchange Sections 1, 2, 4, 5, 6, 7 Student work book Topic 9, Respiratory system
The respiratory system Structure
Organs of the respiratory system Larynx Trachea Rib cage Bronchus Mediastinum Lung Diaphragm
Section through the head Nasal cavity Palate Tongue Pharynx Hyoid bone Epiglottis Larynx Esophagus Teeth Vocal cords The Miles Kelly Art library, Wellcome Images
The mucous lining The nasal cavity and upper airways have a mucous lining. The epithelial lining contains goblet cells which secrete a clear, sticky mucus. The function of mucus is to trap dirt particles and microbes before they enter the lungs.
The nose (nasal cavity) Air enters and leaves the body through the nose. Here it is cleaned, warmed and moistened before entering the body. The nasal secretions contain an anti-bacterial enzyme – lysozyme.
A section through the nasal cavity The Miles Kelly Art library, Wellcome Images Nostril Hard palate Soft palate Sinus NASAL CAVITY
The larynx (Adam’s apple or voice box) The larynx is a box-like structure constructed from nine cartilages and is the entrance to the trachea and lungs. The larynx houses the vocal folds or vocal cords. The entrance to the larynx is protected by the epiglottis. Gray’s Anatomy
The bronchial tree Larynx Trachea Bronchus Bronchiole The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989)
Trachea & bronchi The trachea & bronchi are reinforced with C-shaped rings of cartilage (these prevent the tubes collapsing during inhalation).
The bronchi The Miles Kelly Art library, Wellcome Images Mucous lining Muscular wall Cartilage rings
The upper airways are lined with a ciliated mucous membrane –The sticky mucus traps dirt & microbes –The cilia sweep the dirty mucus up the trachea and into the throat.
The ciliated lining tissue Mucus- secreting goblet cells Cilia G. Meyer, ANHB-UWA,
EM of ciliated epithelium & goblet cells D Gregory & D Marshall, Wellcome Images
Alveoli The brochioles terminate in microscopic clusters of air sacs – the alveoli. Gas exchange takes place in the alveoli. Alveoli G. Meyer, ANHB-UWA
The alveoli (air sacs) The Miles Kelly Art library, Wellcome Images
Section through a lung showing alveoli and blood supply M I Walker, Wellcome Images
The respiratory system Gas exchange
Exchange surfaces Like all exchange surfaces, the alveoli: –are very thin –have a large surface area –are moist –have a rich blood supply
Breathing Breathing (sometimes referred to as ventilation) is the process of moving air into and out of the lungs. The purpose of breathing is to exchange oxygen and carbon dioxide between the lungs and the air.
Boyle's law Boyle's law states that: for a fixed amount of gas kept at a fixed temperature, pressure (P) and volume (V) are inversely proportional (while one increases, the other decreases). This can be stated mathematically as: PV = k where: P is the pressure, V is the volume & k is a constant value representative of the pressure and volume of the system.pressurevolume
Respiration Respiration is the transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction. [ not to be confused with the process of cellular respiration discussed earlier ]
External respiration and Internal respiration External respiration is the movement of O 2 and CO 2 between the lungs and the bloodstream. Internal respiration is the exchange of O 2 and CO 2 between the blood and the tissues.
External respiration Partial pressure (mmHg) Alveolar airDeoxygenated blood Oxygenated blood Oxygen Carbon Dioxide Breathing maintains the correct concentration of gases in the lungs Concentration gradient
Breathing – inhaling (remember P 1 V 1 = P 2 V 2 ) Anatomical changes VP1P1:P2Result Rib cage raised Diaphragm flattens IncreasesDecreases P1
P 1 V 1 = P 2 V 2 A bicycle pump works in much the same way as the lungs
The lungs work in much the same way as a bicycle pump If you increase the volume of the chamber air is sucked in If you decrease the volume of the chamber air is forced out
Breathing – exhaling (remember P 1 V 1 = P 2 V 2 ) Anatomical changes VP1P1:P2Result Rib cage relaxes Diaphragm domed DecreasesIncreases P1>P2 Air forced out of lungs V = volume of thoracic cavity P1 = pressure in thoracic cavity P2 = air pressure
The Miles Kelly Art library, Wellcome Images INHALE EXHALE Ribcage raised Ribcage lowered Diaphragm domed Diaphragm flattened Thoracic volume increased Thoracic pressure < air pressure Thoracic volume decreased Thoracic pressure > air pressure
Why breathe? Fresh air passing through the lungs delivers oxygen to the red blood cells. At the same time, waste carbon dioxide is removed from the blood. This can only occur if fresh air is constantly circulating through the lungs. Wellcome Photo Library Carbon dioxide Oxygen
Oxygen transport Oxygen combines with haemoglobin in RBCs to form oxyhaemoglobin.
Carbon dioxide transport Most CO 2 is transported in the plasma as dissolved bicarbonate ions. -
Diseased lung tissue Photo by Pöllö CDC A.healthy lung tissue B.Smoker’s lung C.Emphysema A B C
Study Guide Read: Our Human Species Chapter 11, sections 1-2, 4-6 Complete: Workbook Topic 9, Respiratory system