Physiology- Lungs/gas exchange Flashcards
What is Fick’s law? And the equation
Fick’s law is the rate at which substances can diffuse
Rate of Diffusion is directly proportional to (surface area x concentration gradient)/ distance
What can we deduce form Ficks law?
In order to support a fast diffusion rate surfaces must have:
- a large surface area
- a short diffusion pathway
- a high concentration difference
What is epithelial tissue?
The layer of cells covering all the external and internal surfaces of the body
Name the 5 types of epithelial tissues:
- Squamous epithelium
- Endothelium
- Columnar epithelium
- Ciliated epithelium
- Epidermis
Describe the lungs: use all necessary vocabulary
Trachea branches to 2 bronchi-> bronchioles->alveoli
Pleural membrane surrounds lungs
How have the lungs adapted for gas exchange?
- large surface area-> 600 million alveoli provide a huge surface area
- short diffusion pathway-> walls of alveoli are flattened epithelial cells like the capillary walls
- mechanism Maintain high conc. gradient-> constant blood flow in capillaries and ventilation in it sacs
Why is exhaled air more humid than inhaled air?
Water inevitably diffuses down its conc. gradient from the tissue fluid and alveoli cells into the air in the alveoli
- due to the lungs being so deep inside the body, the water vapour remains in the lungs and lowers the diffusion gradient causing less water to be lost
Why do the epithelial cells secrete a soapy surfactant in the lungs?
To reduce water surface tension (breaks hydrogen bonds) making it less sticky, without this the alveoli would collapse (common problem in premature babies)
How does the body reduce infection and pathogen invasion in the lungs??
- Epithelial cells of bronchioles secrete mucus
- Mucus traps bacteria and particles
- mucus is swept up by cilia of the ciliated epithelial cells to throat
- mucus is then swallowed and pathogens are killed in stomach acid
- also phagocytes migrate to alveolar air spaces to kill non trapped bacteria
Explain the purpose of the pleural membrane/fluid and thorax
The outer pleural membrane is attached to the thorax while the inner membrane I attached to the lungs, between the membranes is the pleural fluid which is incompressible, so when the thorax expands or contracts so does the lungs
- the alveoli collapse if not held open by the thorax
What direction does air always flow? And how is it tidal?
Air always flows from a high pressure to a low pressure
- tidal meaning the air goes in and out via the same route
What is the process of inspiration?
- diaphragm contracts and external intercostal muscles contract pulling ribs out
- volume of thorax and lungs increases stretching the elastic walled alveoli
- decreases pressure of air in alveoli below atmospheric pressure
- air flows from high pressure outside to low pressure inside alveoli
What is the process of expiration?
- diaphragm and external intercostal muscle relax allowing ribs to fall in
- volume of thorax and lungs decrease causing the alveoli and bronchioles to shrink (elastic recoil)
- pressure inside increases above atmospheric pressure so air flows out
Forced expiration occurs after normal expiration, but how does this occur? And why?
- abdominal muscles contract, pushing diaphragm up
- internal intercostal muscles contact pulling ribs down
- larger and faster respiration (used in exercise)
What is pulmonary ventilation? And how is it calculated?
The volume of air ventilating the lungs per minute
-> PV= ventilation rate x tidal volume
What is ventilation rate and how is it calculated?
The time taken for one whole ventilation cycle (breaths per minute)
-> VR= 60/cycle time (s)
What is tidal volume?
The normal volume of air breathed in each breath (breathing depth)
What is the difference between gas exchange and ventilation?
Gas exchange: certain gases are moved between environment and blood
Ventilation: the muscular movement that speeds up gas exchange
- increases rate of gas exchange by increasing the concentration difference
Gas exchange summary:
- passive
- uses diffusion
- slow
- gases move down their own conc. gradients (may be in different directions)
Ventilation summary:
- uses mass flow
- active process (contracting muscles use ATP)
- all gases in air move together in same direction
- fast process
What is asthma and the symptoms?
Asthma is an allergic response to allergens
-wheezing, difficulty breathing, tight chest and coughing
Describe what happens in an asthma attack:
- allergens (fur, dust, pollen or faeces) trigger an inflammatory response
- white blood cells (mast cells) release histamines causing the smooth circular muscles of bronchioles to contract (bronchoconstriction)
- epithelial cells secrete more mucus which blocks airways
- tidal volume is reduced and air is replaced more slowly, concentration gradient across alveolar epithelium is reduced so less oxygen diffuses into blood for respiration
How to reduce asthma?
Anti-inflammatory drugs
What is process of pulmonary tuberculosis?
- bacterial cells are breathed in, invading the epithelial cells of alveoli and bronchioles, where they multiply into tubercles (dormant lumps)
- the tubercles stimulate an inflammatory response by white blood cells, forming fibrous scar tissue
- scar tissue reduces elasticity of alveoli and thickens walls reducing rate of diffusion
- after months bacteria emerges from tubercles and start reproducing inside lung epithelial cells killing them (reducing their surface area)
- TB also spreads via blood stream to other organs destroying them too
