Chapter 7:Mammalian gas exchange Flashcards
Definition of tissue
-group of similar cells
-consisting of one or more than one type
-with any extracellular material they secrete
-which are specialised to carry out a specific function
e.g squamous epithelium, ciliated epithelium, xylem tissue, phloem tissue
Definition of organ
-group of tissues
-consisting of one or more than one type
-which are specialised to carry out specific functions
e.g lungs, leaves
Role and specialisation of trachea
-carries air from oral cavity to bronchi
-held open by C-shaped rings of cartilage
-smooth muscle, elastic fibres, glandular tissue, connective tissue and blood vessels found under cartilage layer
-lined with layers of ciliated epithelial cells and goblet cells (ciliated epithelial tissue)
Definition of system
-collection of organs
-with a specific function
-e.g circulatory system: heart, blood vessels, blood
gas exchange system: lungs, trachea, bronchi, bronchioles, larynx, mouth, diaphragm
Role and specialisation of rings of cartilage
-found in walls of trachea, bronchi and some larger bronchioles
-provides support: keeps airways open
-strong but flexible to prevent trachea and bronchi collapsing during inhalation and pressure drops
Role and specialisation of bronchi
-base of trachea divides into 1 bronchi
-each one carries air in/out of respective lung
Role and specialisation of bronchioles
-subdivisions of the bronchi
-walls of larger bronchioles contain smooth muscle, elastic fibres, goblet cells and ciliated epithelium
-walls of smallest bronchioles contain elastic fibres and epithelium (no cilia)
Alveoli
-blind ending sacs at end of each bronchioles
-site of gas exchange
-wall consists of a single layer of squamous epithelial cells and elastic fibres containing elastin which stretch during inhalation and recoil during exhalation
-walls also contain collagen and stretch receptors which act as a sensory input to enable control of ventilation mechanism
-liquid layer lining alveolus contains surfactant (specialised phospholipid produced by septal cells in alveolar wall)
-Surfactant reduces surface tension of water
-easier to inflate lungs
-prevents alveoli sticking together during exhalation
-contains antibacterial chemicals
-enables oxygen to diffuse into surfactant and diffuse across alveolar wall but does NOT increase rate of diffusion
Goblet cells (found in between ciliated epithelial cells)
-secrete mucus which is a specialised glycoprotein
-mucus creates a layer over the ciliated epithelium to trap pathogens and dust
-mucus is then wafted upwards preventing pathogens entering the alveoli
Cilia
-HAIR-LIKE extensions
-beat and waft mucus in rhythmic motion
-moves mucus upwards towards throat and away from alveoli
-moves mucus and trapped pathogens up to mouth to be swallowed where the HCL kills pathogens in stomach
or coughed up and removed from body as sputum
Elastic fibres
-found in walls of trachea, bronchi, bronchioles and alveoli
-during inhalation, elastic fibres in alveoli stretch to enable alveoli to inflate (prevent alveoli from bursting on over-inflation)
-during exhalation, elastic fibres recoil to help deflate alveoli
-elastic tissue allows the lung tissue to expand and recoil
Smooth muscle
-found in walls of trachea, bronchi and bronchioles
-enables diameter to be controlled-during exercise, smooth muscle relaxes so lumen widens which reduces resistance to airflow and so easier to inflate and exhale
smooth muscle contracts to narrow lumen which reduces toxins
Function of pulmonary ventilation
-maintains diffusion gradient
During inspiration:
external intercostal muscles contract
internal intercostal muscles relaxes
ribcage moves up and out
diaphragm contracts and flattens
volume of thorax increases
volume of lungs increases
pressure in lungs decreases
pressure in lungs is below pressure outside lungs so air rushes into lungs by the active process
During expiration:
external intercostal muscles relax
internal intercostal muscles contract
ribcage moves inwards and downwards
diaphragm relaxes
-diaphragm becomes dome shaped
-volume of thorax decreases
-volume of lungs decreases
-pressure in lungs increases
-pressure in lungs is above pressure outside lungs
-so air rushes out of lungs by the passive process usually but forced exhalation is active
What does lung capacity depend on?
body size
physical activity level
general health
in adult approx 6dm cubed
Tidal volume
volume of air that moves in (and hence out) in each normal breath at rest (approx 0.5dm cubed)
Vital capacity
maximum volume of air that can be inhaled or exhaled (deepest forced inhalation possible after deepest forced exhalation)
Residual volume
-volume of air that remains in the lungs after a forced exhalation (prevents lungs from collapsing and alveoli from sticking together)
Equation for total lung capacity
residual volume+vital capacity
Breathing
-number of breaths taken in a given time period
Pulmonary ventilation
-movement of fresh air into lungs and removal of stale air out of lung
-PV=tidal volume x breathing rate
Forced expiratory volume in one second
volume of air forcibly exhaled in first second of forced exhalation
Peak expiratory flow rate
maximum rate of forced exhalation through mouth
