Respiratory System (11)

Function of the nose

Warms and moistens air before it enters the lungs, as well as filtering air through hair and mucus lining the structure. Contains smell receptors and acts as a resonating chamber for speech sounds.

Function of the pharynx

Also known as the throat, air from the nasal cavity passes through.

Function of the larynx (voice box)

Air passes through the larynx to and from the lungs, contains vocal cords which vibrate to make sound.

Function of trachea

Also known as the windpipe, carries air to and from the lungs. Lined with mucous and cilia, which move trapped particles upwards away from the lungs.

Function of the lungs

Site for gas exchange. Covered with a pleural membrane, the pleural fluid holds the lungs against the inside of the chest.

Function of bronchi

Two primary bronchi branch from the trachea, then divide into secondary and tertiary branches, carry air to and from the lungs.

Function of bronchioles

Very fine tubes with walls of smooth muscle, finest branch finishes at the alveoli (air sacs). Carry air to and from the lungs.

Function of alveoli

Tiny air sacs that make up the majority of the lungs, increased surface area, have thin walls and are well supplied with blood capillaries.

Function of diaphragm

Muscle that separates the chest from the abdomen, contracts and flattens to increase the volume of the chest and lungs causing air to move in.

Function of intercostal muscles

Muscle between the ribs, contracts and moves rib cage upwards and outwards to increase the volume of the chest and lungs causing air to move in.

Function of ribs

Form the framework for the chest.

Function of pleural membrane

Covers the lungs surface and inside of the chest, works with the pleural fluid to allow breathing to occur.

function of epiglottis

Flap of tissue that, during swallowing, closes off the trachea so food and liquid cannot enter the lungs.

Function of Uvula

Secrete saliva to moisten the mouth and throat.

Name the blood vessels associated with the lungs

Pulmonary artery, pulmonary vein and capillaries.

Describe the role of the pulmonary artery

Deoxygenated blood, takes blood from the right ventricle and sends it to the lungs.

Describe the role of the pulmonary vein

Oxygenated blood, takes blood from the lungs (capillaries and venules and veins) and carries it to the left atrium.

Describe the role of the capillaries

Microscopic blood vessels that link arterioles and venules.

Distinguish between breathing and respiration

Breathing is the physical movement of air into and out of the lungs (Inhalation + Exhalation). Where as respiration is the chemical process in which the glucose we get from digestion reacts with the oxygen we get from breathing to produce energy (ATP) for the cells.

Outline and explain the mechanics of breathing - Inspiration

Inspiration: Intercostal muscles contract, Diaphragm contracts and flattens, ribcage moves upwards and outwards, chest cavity - Thoracic volume increases, pressure inside the lungs decreases, Air flows from an area of high pressure in the atmosphere to an area of low pressure inside the lungs.

Outline and explain the mechanics of breathing - Expiration

Expiration: Intercostal muscles relax, Diaphragm relaxes and domes up into the thoracic cavity, Ribcage moves inwards and downwards, chest cavity - Thoracic volume decreases, Pressure inside the lungs increases, Air flows from an area of high pressure inside the lungs to an area of low pressure in the atmosphere.

Compare the composition of inhaled and exhaled air

Inhaled air: 20.95 oxygen, 0.04 carbon dioxide. Expired air: 15.80 oxygen, 4.30 carbon dioxide. The other 79% of the inspired air is made up of mainly nitrogen, with varied amounts of water vapor.

Describe where gas exchange occurs and how it occurs

Blood in the capillaries around the alveoli is brought to the lungs by the pulmonary artery - it has been around the body where much of the oxygen has been taken up by body cells. Therefore, it has a low O2 concentration compared with the air in the alveoli. Oxygen dissolves in the moisture on the inside of the alveolus and diffuses through the membrane, the walls of the capillaries (one cell thick) and into the blood. Blood arriving at the capillaries of the alveoli has come from the body's circulation where it has picked up carbon dioxide. Concentration of CO2 in capillaries is higher than in the air in the alveolus. CO2 diffuses out of the blood and into the air in the alveolus.

List the characteristics of the respiratory surfaces that enable efficient gas exchange

Alveoli surface area, Large blood supply, Thin membrane, Lung positioning, Alveolus membrane, Change of lung volume.

Describe how alveoli surface area enables efficient gas exchange

Large amounts of gases can be exchanged in a short amount of time, surface area approx. 50-80 m.

Describe how large blood supply enables efficient gas exchange

Each alveolus is well supplied with blood capillaries, meaning as much blood as possible is close to the air in the alveolus. Continual flow maintains the concentration gradient, the difference in oxygen and carbon dioxide concentration.

Describe how a thin membrane enables efficient gas exchange

Membrane wall of alveolus is 1 cell thick so only a short distance for gases to travel, easy for gases to exchange.

Describe how lung positioning enables efficient gas exchange

Lungs are deep inside the body, preventing excessive evaporation of fluid that covers respiratory surfaces. Moisture is important because gases can only diffuse into and out of the blood when they are dissolved in fluid.

Describe how the alveolus membrane enables efficient gas exchange

Membranes of the alveolus are covered by a layer of moisture. The gases can diffuse into and out of the blood only when they are dissolved in fluid.

Describe how change of lung volume enables efficient gas exchange

Constant changing of the air in the alveoli helps ensure there is always a difference in the concentrations of oxygen and carbon dioxide. Lung volume can be changed by movements of the diaphragm and intercostal muscles.

Describe the factors that maintain a diffusion gradient between the gases in the air, in the alveoli and in the blood.

Constant flow of blood through the capillaries: As the blood flowing through the capillaries around each alveolus picks up oxygen and loses carbon dioxide, it is replaced by more blood pumped into the capillaries. This 'new' blood is low in oxygen and high in carbon dioxide, so the concentration gradient is maintained. Movement of air into and out of the lungs: The air that has picked up carbon dioxide from, and lost oxygen to, the blood is replaced by 'new' air with each breath. The 'new' air is low in carbon dioxide and high in oxygen.

Describe how emphysema affects the exchange of gases in the lungs

Emphysema is a disease usually caused by long-term exposure to irritating particles in the air taken into the lungs, such as tobacco smoke. People who work in high-dust conditions or live in cities with high air pollution are also at greater risk.
The irritating particles cause damage to the alveoli. They lose their elasticity, are often replaced with fibrous tissue, and may break down, reducing the internal surface area of the lung. Because of the loss of elasticity of the lung tissue, the lungs are constantly inflated, and breathing out no longer occurs passively but requires voluntary effort.

Describe how lung cancer affects the exchange of gases in the lungs

Lung cancer involves the development of a mass of cells that divides in an uncontrolled way - a tumour.
There are clear links between lung cancer and exposure to asbestos fibres and other pollutants. However, tobacco smoking poses by far the greatest risk for lung cancer.
The most common form of lung cancer begins in the walls of the air passages, usually the bronchi. Inhaled smoke particles constantly irritate the mucous membrane that lines the air passages, resulting in excessive production of mucus.

Describe how pneumonia affects the exchange of gases in the lungs

Pneumonia is an infection of the lungs caused by bacteria, viruses, fungi or other organisms. The inflammation resulting from the infection causes secretion of fluid and mucus into the alveoli, reducing the amount of air that they can contain. The surface area available for exchange of gases is also reduced, and breathing difficulty is a symptom of many types of pneumonia.

Describe how tuberculosis affects the exchange of gases in the lungs

Tuberculosis is an infection, usually of the lung, by the bacterium Mycobacterium tuberculosis. Damages the alveoli causing them to become hard and fibrous, useless for gas exchange, persistent cough is a common symptom.

Describe how asthma affects the exchange of gases in the lungs

Asthma is a medical condition that causes difficulty breathing due to a narrowing of the airways. This occurs due to:
•the smooth muscles contracting, narrowing the airway
•inflammation causing the lining of the airways to thicken, narrowing its diameter
•mucus filling the airway, narrowing the tube.
The reduced volume of air going into and out of the lungs means that the exchange of gases is impaired, and the blood does not carry the usual amount of oxygen.