mammalian gas exchange and ventilation Flashcards
why do single-celled organisms dont need specialised exchange surfaces?
-have large SA: VOL ratio
-metabolic activity is usually low
-small in size
why do multicellular organisms need specialised exchange surfaces
-diffusion across outer membrane is too slow
-some cells are deep within the body = big diffusion distance
-low surface area to volume ratio
-high metabolic rate
what features make a good exchange surface
give examples where these are seen
-large surface area - root hair cell
-thin walls/ barriers - alveoli
-good blood supply - gills/ alveolus
-ventilated
-partially permeable
what is the structure and function of the lungs
-2 pairs of lobed structures made up of highly branched tubules called bronchioles which end in tiny air sacs called alveoli.
what is the structure and function of the trachea
-a flexible airway supported by rings of cartilage that prevent it from collapsing as air pressure falls during inhalation
-walls made of smooth muscle and lined with ciliated epithelial and goblet cells to trap dirt particles and bacteria which is wafted up and swallowed
-elastic fibres
what is the structure and function of bronchi
-two divisions of the trachea which lead to the lungs
-produce mucus to trap dirt and cilia to move the dirt-laden mucus up towards the throat by columnar ciliated epithelium
-supported by cartilage
-smooth muscle and elastic fibres
what is the structure and function of bronchioles?
-a series of branching subdivisions of the bronchi made from smooth muscle that allows them to constrict to control air movement in and out.
-ciliated epithelium
-elastic fibres
what is the structure and function of alveoli
-small air sacs with a diameter of between 100-300um found at the end of bronchioles
-contain some collagen and elastin fibres
-lined with epithelium
-elastic fibres allow them to stretch as they fill up with air
-can spring back to place to expel the carbon dioxide
-alveolar membrane = gas exchange surface
how are alveoli adapted for a rapid rate of diffusion
-alveolus wall and capillary wall is one cell thick= both made of squamous epithelia = short diffusion distance
-capillaries in close contact with alveolus wall
-millions of alveoli - large surface area
-good blood supply
what is the location of squamous epithelium
what is the sructure and function
-alveoli, capillaries
-flattened cells- very short diffusion for gases
what is the location of ciliated epithelium
structure and function?
-trachea, bronchi, bronchioles
-hair like projections on surface of cell waft mucus up and out of airways so can be swallowed
-goblet cells = produce mucus that traps pathogens. glandular tissue in the loose tissue also produces mucus
what is the location of cartilage
structure and function?
-trachea, bronchi, larger bronchioles
-Support the airways and prevent them from collapsing during inspiration. C-shaped rings in the trachea for flexibility and to allow ad to pass down the oesopnagus
what is the location of smooth muscle
structure and function?
-bronchioles
-Contracts to constrict the airways making the lumen narrower (allergic reaction)
what is the location of elastic tissue
structure and function?
-alveoli
-fibres that stretch during inspiration and recoil during expiration
what happens during inspiration (uses energy)
-external intercostal muscle contract and internal intercostal muscle relax
-rib cage rises
-diaphragm contracts at the same time
-diaphragm flattens
-volume inside chest cavity (thorax) increases
-pressure inside the chest cavity decreases below atmospheric pressure
-air moves into the lungs
