Mammalian Gas exchange Flashcards
Tissue
-a 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
Organ
a group of tissues (consisting of 1 or more than 1 type), which are specialised to carry out specific functions
System
a collection of organs with a specific function
Gas exchange function
- Diffusion of respiratory cases: co2 out, o2 into bloodstream
- Rate would be too slow in multicellular organisms so need specialised exchange system
GES high SA
- SA of alveoli is huge- 300-500M alveoli per adult lung
- Alveoli expand during inhalation, inc SA, so more CO2 and O2 molecules can diffuse per unit time
GES thin
- Alveolus made from single layer of cells: alveolar epithelium
- 0.6um so reduces diffusion distance-> inc D rate
- Capillary walls also one cell thick: short D distance between RBC in plasma to air in alveoli
GES good blood supply
- Large capillary network surrounds each alveolus
- Maintains concentration gradient
- Enables O2 and CO2 to be exchanged in opposite directions
GES steep diffusion gradient
- pulmonary circulation rapidly delivers o2 and removes co2
- pulmonary ventilation replaces co2 rich air with o2 rich air
- maintains diffusion gradient
Trachea
- carries air from oral cavity to bronchi
- held open by C-shape rings of cartilage
- Smooth muscle, elastic fibres, glandular tissue, connective tissue, blood vessels found under cartilage layer
- lined with layer of ciliated epithelial cells & goblet cells (ciliated epithelial tissue)
Cartilage rings
- found in walls of trachea and bronchi
- provide support
- strong but flexible to prevent them collapsing during inhalation and pressure drops
Bronchi
- Base of trachea divides into 1 bronchi
- Each one carries air into/out respective lung
Bronchioles
- subdivisions of the bronchi
- walls of larger bronchioles contain smooth muscle, elastic fibres, goblet cells, ciliated epithelium
- walls. of smaller contain elastic fibres and smooth muscle- no cilia
Alveoli
- Blind ending sacs at the end of each bronchiole
- site of gas exchange (diameter 200-300um)
- Walls consists of single layer of squamous epithelial cells & elastic fibres containing elastic (S & R)
- Walls also have collagen and stretch receptors
- 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 inhalation, antibac chemicals, enables o2 to dissolve into surfactant to diffuse across alveolar wall
Goblet cells
- Secrete mucus (mucus is specialised glycoprotein: mucin+ glycocalyx)
- Mucus traps microorganisms, dust, polen etc
Cilia
- ‘Hair like’ extensions to the individual cells
- Beat and waft mucus in rhythmic motion
- Moves mucus upwards towards throat and away from lungs
- Swallowed- hcl in stomach kills pathogens
- Coughed up & removed from body as sputum
Elastic fibres (stretch and recoil only)
- trachea, bronchi, bronchioles, alveoli
- Inhalation- they allow alveoli to stretch to inflate & prevent bursting from over-inflation
- Exhalation- they recoil to help deflate
- They help lung tissue to stretch and recoil
Smooth muscle (only contract and relax)
- trachea, bronchi, bronchioles
- enables diameter to be controlled
- During exercise, smooth muscle relaxes- widens lumen
- So, reduces R to air flow & easier to inhale and exhale
Pulmonary ventilation
- consists of inspiration & expiration
- Function is to maintain diffusion gradient
Inspi ration
- External intercostal muscles contract and internal relax
- Diaphragm relaxes and flattens
- Volume of thorax inc and ribcage moves up and out
- Pressure inside thorax dec
- Pressure in lungs is below pressure outside the lungs
- Air rushes in
- Active process
E xpir ation
- E xternal intercostal muscles r elax and internal contract
- Diaphragm contracts and becomes dome shaped
- Volume of thorax dec and ribcage is pushed down and in
- Pressure inside thorax inc
- Pressure in lungs is above pressure outside
- Air rushes out
- Passive process usually but forced exhalation is active
Lung capacity
- depends on body size, physical activity level, general health
- in adult =6L but much of this is not used
Tidal volume
volume of air that moves in in each normal breath (0.5L)
Vital capacity
Maximum amount of air that can be inhaled or exhaled (3-5L)
Residual volume
volume of air that remains in lungs after a forced exhalation (prevents lungs from collapsing)
Pulmonary ventilation
Equation
PV= tidal volume x breathing rate
peak expiratory flow rate
- maximum rate of forced exhalation through mouth
- PEFL used to diagnose pulmonary disorders eg. asthma
Healthy: M 570-640 dm3min-1
F 420-460
Asthmatic: M 400
F 200
max value is at 35 years old, then falls
Respiratory arrest causes
asthma attack, overdose, heart attack, severe pneumonia etc
Treating respiratory arrest
- Call 999
- Open airway & remove any obstruction visible in mouth using sweeping motion
- Tilt head back and remove tongue from back of throat
- Look for breathing
- pinch nostrils, make seal over mouth with your mouth
- give 2 rescue breaths ad watch chest rise and fall(if pulse, continue rescue breaths)
- no pulse, begin cpr
- Place heel of hand with interlocked fingers on chest
- press down 5cm
- 30:2
- Continue until help arrives
forced expiratory volume in one minute (FEV1)
volume of air forcibly exhaled in first second of forced exhalation
