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gaseous exchange, breathing - mechanical process whereby air moves in and…

- - - - diaphragm contracts and becomes flatter
      - thoracic cavity enlarges from top to bottom
      - external intercostal muscles contract
      - causing ribs to move upwards and outwards
      - thoracic cavity enlarges from side to side and front to back
      - abdominal muscles relax so the abdominal cavity can accommodate viscera(all internal organs) being pushed down by diaphragm
      - total volume of thoracic cavity increased
      - pressure in thoracic cavity and lungs decrease
      - elastic lungs expand
      - since atmospheric pressure higher than pressure in thoracic cavity and lungs, O2-rich air flow into lungs
    - - diaphragm relaxes and returns to original
      - thoracic cavity becomes smaller from top to bottom
      - external intercoastal muscles relax
      - causing ribs to move downward and inward
      - the thoracic cavity reduces in size from side to side and front to back
      - total volume of thoracic cavity reduced
      - pressure in thoracic cavity and lungs increase
      - since pressure in chest cavity and lungs higher than atmospheric pressure, CO2- rich air flows out lungs
- - - - most of O2 that diffuses from air in alveoli to blood in capillaries combine with haemoglobin in red blood cells to form oxyhaemoglobin
      - very small portion of O2 dissolves in blood plasma
      - O2 transported via heart to all tissues in two ways
  - - - most of CO2 diffuses from cells into blood in capillaries, combine with water to form carbonic acid, after dissociates and is transported as bicarbonate ions
      - portion combines with haemoglobin to form carbamminohaemoglobin
      - smallest portion of CO2 dissolves in blood plasma
      - CO2 transported in these three ways via heart and lungs
- - - - by bacterium mycobacterium tuberculosis
    - - persistent cough
      - tiredness and fatigue
      - weight loss
      - night sweats
      - chest pain
      - blood in mucus coughed up
    - - bacteria released into air when infected person coughs, sneezes, shouts or spits
      - bacteria in infected droplets spread through air and can be inhaled by healthy person
    - - TB can be treated and successful cured with early and correct diagnosis
      - TB treated with aggressive course of antibiotics, full course must be completed
      - treatment lasts about 6 months
- - - - transport air to and from lungs and include nasal passages, pharynx(throat), trachea(windpipe), bronchi and bronchioli
      - nasal cavity
        
        two external nostrils lead to two nasal cavities that are separated by septum
        
        small hairs in nasal cavities filter larger particles from air inhaled
        
        each cavity divided into 3 passages by three curved turbinate bones
        
        nasal cavities lined with mucous membrane, consists of ciliated columnar epithelial cells
        
        columnar epithelial cells richly supplied with superficial blood capillaries that warm incoming air
        
        Goblet cells in columnar epithelium secrete mucus that
        
        traps dust and germs
        
        antiseptic and prevents inhaled germs from multiplying
        
        moistens incoming air and prevent gaseous exchange from drying out
        
        cilia on columnar epithelial cells continuously perform sweeping movements in direction away from lung, dust carrying mucus expelled to outside
      - pharynx (throat)
        
        nasal cavities open into pharynx
        
        pharynx leads to two openings
        
        opening known as glottis, leads to trachea
        
        opening leading to oesophagus(gullet)
      - trachea(windpipe)
        
        long, tubular structure(12cm long) located at front of oesophagus
        
        larynx(voice box), houses vocal chords, located at top of trachea
        
        larynx is a triangular box made of cartilage
        
        at top of larynx is the epiglottis, thin, leaf-shaped structure made of cartilage
        
        epiglottis closes the glottis(opening to trachea) during swallowing process. prevents food from entering trachea and choking person
        
        walls of trachea reinforced and kept open by C-shaped cartilage rings
        
        openings of C-shaped cartilage rings, covered by involuntary muscle tissue, face toward the back and press against oesophagus, allows oesophagus to expand and food moves down through it
        
        just like rest of air passages, trachea lined with mucous membrane of ciliated columnar epithelial cells that secrete nucus
        
        dust particles and germs that enter the trachea are trapped in mucus and moved to pharynx by sweeping action of cilia, which it is coughed up or swolled
        
        like the rest of the air passages, trachea lined with mucous membrane of ciliated columnar epithelial cells that secrete mucus
        
        dust particles and germs that enter trachea are trapped in mucus and moved to pharynx by sweeping action of cilia, after it's coughed up or swallowed
      - bronchi and bronchioli
        
        trachea divides into a right and left bronchus that enters the right and left lung respectively
        
        bronchi lined with mucous membrane and are held open by O-shaped cartilage rings
        
        inside lungs, bronchi divide into smaller branches, lose their cartilage and form bronchioles
        
        each bronchioli ends in infundibulum consist of groups of alveoli
    - - external structure
        
        two openings located in chest
        
        lungs surrounded and protected by 12 pairs of ribs
        
        intercostal muscles found between ribs
        
        right lung consists of three lobes, left lung has two
        
        lungs are spongy and elastic
        
        each lung surrounded by double membrane, pleura
        
        there's intrapleural fluid between two pleural membranes that prevents friction that occurs when lungs shrink or expand
        
        lungs are conical and rest at bottom on a dome-shaped muscle plate, diaphragm
      - internal structure
        
        inside the lung the bronchi out, becoming smaller and forming bronchioli
        
        as bronchioli branch out into smaller bronchioli, lose cartilage support and end in infundibula (lung sacs), consist of group of alveoli
        
        walls of alveoli very thin and consist of single layer of squamous epithelium
        
        alveoli surrounded by network of capillaries
        
        walls of capillaries consists of single layer of squamous epithelium (endothelium)
    - - different muscles play role during breathing
        
        Diaphragm
        
        in relaxed state, a dome-shaped muscle plate
        
        muscle plate separates chest and abdomen to form airtight thoracic cavity
        
        intercoastal muscles
        
        located between consecutive ribs and consist of two sets i.e.
        
        external intercoastal muscles
        
        internal intercostal muscles