Summary OCR A/AS-Level Biology 3.1.2-3 Mammalian Exchange Tissues

Mammalian Exchange
Tissues
Blood Vessels
 Arteries + arterioles – oxygenated blood away from the heart under high pressure
 Veins + venules – deoxygenated blood towards the heart under low pressure
 Capillaries – between blood vessels under decreasing pressure – allow gas exchange
 Heart > arteries > arterioles > capillaries > venules > veins > heart

Found In Function
Ciliated epithelium cells Walls of trachea, bronchi and Movement of trapped dust
bronchioles and bacteria
Goblet cells Walls of trachea, bronchi and Secretion of mucus
bronchioles
Cartilage C-shaped rings in trachea Strength and support –
Islands in bronchi prevent collapse
Smooth muscles Trachea, bronchi and large Contracts to constrict airway
bronchioles to prevent harmful
substances entering
Elastic muscles Trachea, bronchi and large Relax smooth muscles to
bronchioles dilate airways
Squamous epithelium cells Alveoli One cell thick to provide a
short diffusion




Alveoli
 Rich blood supply
 Moist surface to absorb and dissolve gases and speed up diffusion
 Surfactant decreases surface tension which helps prevent collapse
 Large SA:V ratio
 Thin permeable membrane
 Well-ventilated