lungs, gas exchange and respiratory diseases Flashcards
what are the lungs made of, whats their structure and where are they in the body?
theres 2 lungs, the left lung has 2 lobes and the right lung has 3
they occupy most of the volume of the thoratic cavity
the diaphragm separates the thoratic and abdominal cavities
they are made up of columnar epitheliated cells, cilliated cells are found running down the trachea down to the large brinchioles
there are also goblet cells which secrete mucous
what are alveloli?
there are about 300 million alveoli which make up ~70-90m2 surface area
each alveolus has about 0.2mm diameter
capillaries surround each alveolus
what are the 2 types of alveolar cells?
type I- small epithelial cells with no cilia, they exchange gas
type II- secrete surfactant, a substance that facilitates lung explasion
what removes foreign material from alveoli in order to prevent infection?
macrophages
what are the respiritory mechanincs?
air tends to flow from an area of high pressure to a region of low pressure
air flows in and out of the lungs by reversing pressure gradients
boyles law - at any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
how to calculate boyles law?
PxV= constant
P1x V1 = P2x V2
what do changes in alveloar pressure mean?
they produce air flow into and out of the lungs
if it is less that atmospheric pressure, air flows into the lungs
if it is more than atmospheric pressure then air flows out of the lungs
how are the lungs inflated/ ventilated?
the external intercostal muscles contract during inhalation to increase the chest volume
- the diaphragm then lowers during inhalation
- air flows in during inhalation because the air pressure in the lungs is lower than that outside
- airflows out when the muscles relax
what is asthma?
- its a respirotory disease caused by a contraction of the airways and excess mucous production
- its a chronic inflammatory disease of the airways of the lungs
- smooth muscle around the bronchioles is hyperextendable and contracts more than normal
- increased resistance to airflow into and out of the lung, creates a characteristic wheezing sound
- increased mucous secretion further inhibits the flow of air into and out of the lungs
- it affects 5.4million people
3 people die a day and it tends to run in families
the triggers could be exercise, cold, allergens and chemical irritants - its an imbalance in immune response which controls inflammation
- the treatments for it are B-asrenoreceptot which relaxes the bronchiole smooth muscle or a corticosteroid which reduces inflammation
what is emphysema?
its a long term progressive disease of the lungs with continuous shortness of breath, coughing and wheezing
the alveoli are destroyed and the bronchioles are also damaged or destroyed which leads to airway collapse and difficulty emptying gases from the alveoli
a significant cause is smoking, it affects 1.2 million people in the UK and the treatment is to stop smoking, use bronchodilators, take corticosteroids and have oxygen therapy
what is cystic fibrosis?
its an inherited respirotory disease for 1 in 2500 babies a year
it affects the lungs, digestive system and other organ systems
it is excess production of thick, sticky mucous
the treatment is airway clearance through physiotherapy, antibiotics, corticosteroids, pancreatic enzyme replacement therapy and having a high calorie diet
what happens in gas exchange in the alveoli?
the pressure exerted by the atmospheric air above the earths surface.
daltons law is that each of the gases contribues to their total air pressure
partial pressure os th pressure contributed by a single gas in a mixture of gases
the exchange of O2 and CO2 across the alveoli is achieved by diffusion and depends on the differences in partial pressure across the respiratory membrane
the distances involved in in gas exchange are small
a gas always diffuses down a partial pressure gradient and O2 moves from the lungs into the blood stream from high > low as CO2 moves out of the bloodstream
how soluble are CO2 and O2 in blood plasma?
they have very linited solubilities in blood plasma
at Po2=100mmHg, only 3ml of O2 would dissolve in 1L of blood, this means only 15ml of O2/min can dissolve in the pulmonary blood flow of 5L/min but the body needs 250ml O2/min
heam groups in red blood cells allow the blood to carry more oxygen
