breathing system 1.docx

The Breathing System in the Human (2) The human breathing system starts with the mouth and nostrils (buccal cavity and nasal passages). This is an area where pathogens can easily enter, so defence mechanisms are in place. The lining membranes are covered in cilia and mucus. Mucus traps dust, pollen,...

The Breathing System in the Human (2) The human breathing system starts with the mouth and nostrils (buccal cavity and nasal passages). This is an area where pathogens can easily enter, so defence mechanisms are in place. The lining membranes are covered in cilia and mucus. Mucus traps dust, pollen, and pathogens, while cilia beat in unison to move the mucus up to the pharynx where it is swallowed. The acid in the stomach kills any pathogens swallowed in the mucus. Nose and Mouth - Air enters the nose where it is filtered - The air is warmed and moistened as it passes through the nasal cavities. - Chemoreceptors detect chemicals in the air to collect information e.g., to check if food is still edible or to check if there is a predator nearby. This is the sense of smell. Epiglottis - A small flap of cartilage - Stops food entering the trachea by automatically covering the opening of the trachea when trying to swallow Trachea - The main tube that carries air to the lungs - Has a ring of cartilage down its length to ensure it is never obstructed Bronchus The first division of the trachea which forms a short tube leading to each lung Bronchioles - Further subdivisions of the bronchus which allow air to freely reach all areas of the lungs Alveoli - Sacs in which gaseous exchange occurs - Resemble a hollowed-out bunch of grapes, this shape gives them a large surface area - Walls of the alveoli are thin and covered with a dense network of capillaries to make diffusion of gases efficient Pleural Membranes - A pair of moist, lubricated membrane that surround the lungs - Prevent abrasion of lung tissue against the ribcage as we breathe - Inflammation and infection of the pleural membranes causes a disease called pleurisy Diaphragm - A dome shaped sheet of muscle which separates the thoracic cavity from the abdominal cavity - When the muscle contracts, it becomes flat to increase the volume of the thoracic cavity, which plays a major role in breathing Ribs - A series of 12 paired bones that surround the thoracic cavity and protect the lungs and heart Intercostal Muscles - Located between the ribs - When they contract, they lift the ribcage up and out, which increases the volume of the thoracic cavity Adaptations of The Breathing System - Capillaries lie very close to the surface of the alveoli for an efficient diffusion of CO2 out of the blood and O2 into the blood - Surfaces are kept moist. The exchange of oxygen and carbon dioxide occurs across plasma membranes, which must be in contact with an aqueous solution - Large surface area - Lung tissue is elastic, which helps breathing out, as it recoils to its original shape and size Breathing Mechanism The breathing rate (number of breaths per minute) is under subconscious control by an area of the brain called the Medulla Oblongata. It measures the concentration of O2 in the blood by measuring its pH. The higher the CO2 concentration, the lower the pH. If the CO2 concentration is going up, the breathing rate is increased and deepened. The opposite happens is CO2 levels are dropping Inhalation - The first stage in breathing and is an active process - The diaphragm contracts and flattens while the intercostal muscles contract and lift the ribcage up and out - This increases the volume of the thoracic cavity which causes a decrease in pressure - The greater pressure of air outside forces air into the lungs - This is referred to as a negative pressure system Exhalation - A passive process - The diaphragm relaxes and returns to its dome shape while the intercostal muscles relax, and the ribcage moves down and in - This causes a decrease in the volume of the thoracic cavity which causes an increase in pressure - Air is pushed out of the lungs Breathing disorders – Asthma - The most common breathing disorder in Ireland - Caused by pet dander or dust mites. Vacuuming regularly to clear the dander and dust can improve symptoms - An inhaler called a bronchodilator is an appropriate treatment for asthma