C1 - Structure of the respiratory system

• Provides oxygen to all living cells/ tissues in the body • Removes waste products such as carbon dioxide, heat and water vapor

• Lungs • Removal of waste products also takes place

• Air is drawn into the body via the mouth and nose, passes through a series of airways is referred to as the ‘respiratory tract’

Upper respiratory tract - nose, nasal cavity, mouth, pharynx and larynx Lower respiratory tract - trachea, bronchi and lungs

• breath in, air enters the nasal cavity by passing through the nostrils • hairs within the cavity filter out dust, pollen and other foreign objects • sticky mucous layer traps the small particles and tiny hairs (cilia) transport them to the pharynx to be swallowed • air is warmed/ moistened in the internal nasal cavity before it enters the pharynx

• throat • small tube (10-13 cmfrom base of skull to C6 vertebrae) • pharynx wall is made of strong skeletal muscle • shaped like a funnel it connects the nasal cavity and the larynx • passageway for food as well as air, special adaptations are required to prevent food entering the bronchus

• small flap of cartilage at the back of the tongue which closes the top of the trachea when surrounding food • ensures that food and drink does not enter the trachea and down into the bronchus • this is essential as the pharynx allows both food/ drink and air to travel in this direction

• voice box • has rigid walls of strong muscles and cartilage • contains the vocal cords and connects the pharynx to the trachea • inline with C6 vertebrae

• windpipe • denotes the start of the lower respiratory tract • 12 cm long and 2cm diameter • contains strong/rigid rings of cartilage to prevent it from collapsing but it is flexible • it travels down and branches into the left and right bronchi

• key organs and allows oxygen to be drawn into the body • right lung is larger than the left and has 3 sections • left only has 2 sections (heart takes up room) -both suspended in the right and left pleural cavities

• branch off the trachea and carry air into the lungs • when air enters the bronchi’s, it has been filtered, moistened, warmed and saturated with water vapor • when inside the lungs, each bronchus divides further into lobar bronchi • lobar bronchi branch into segmental bronchi, which divide again into smaller bronchi (bronchioles) • 23 different sized bronchi in the lungs • branching pattern means that the bronchial network is often referred to as the ‘bronchial tree’

• small airways that extend from the bronchi and connect the bronchi to small clusters of thin walled sacs (alveoli) • 1mm in diameter and are the first airway branches of the respiratory system that DO NOT contain cartilage

• end of each bronchioles is a mass of air sacs called alveoli • there is 300 million alveoli • responsible for the transfer of oxygen into the circulatory system and remove waste products like carbon dioxide out of the blood (process called gaseous exchange) • have a huge surface are of maximal gaseous exchange to take place • surrounding each alveoli is a dense network o capillaries (this aids gaseous exchange)

• flat muscle that is located beneath the lungs within the thoracic cavity, it separates the chest and the abdomen • essential during the breathing process as its contraction downwards draws air into the lungs • this contraction increases the volume of the chest cavity (drawing air in) and the relaxation of the diaphragm reduces the volume (pushing air out)

Internal - lie inside the ribcage - draw ribs downwards and inwards, decreasing the volume of the chest cavity (forcing air out of the lungs when breathing air) External - lie outside the ribcage - pull the ribs upwards outwards, increasing the volume of the chest cavity (drawing air into the lungs)