❤️🔥2- gas exchange (human) Flashcards
the lungs are
the gas exchange surface in humans
all gas exchange surfaces have features which allow maximum amount of gas in the smallest space, these are-
large surface area to allow faster diffusion of gases across the surface, thin walls to ensure diffusion distances remain short, good ventilation with air so that diffusion gradients can be maintained, good blood supply to maintain a high concentration gradient so diffusion occurs faster
ribs
bone structure that protects internal organs such as the lungs
intercostal muscle
muscles between the ribs which control their movement causing inhalation and exhalation
diaphragm
sheets of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation
trachea
windpipe that connects the mouth and nose to the lungs
larynx
also known as the voice box, when air passes across this we are able to make sounds
bronchi
large tubes branching off the trachea with one bronchus for each lung
bronchioles
bronchi split to form smaller tubes called bronchioles in the lungs connected to the alveoli
alveoli
tiny air sacs where gas exchange takes place
pleural cavity
the fluid filled space between the pleural membranes which reduces friction and allows the lungs to move more freely
the passages down to the lungs are lined with
ciliated epithelial cells
cilia cells have
tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed
the mucus is made by
special mucus producing cells called goblet cells because they are shaped like a goblet (cup)
mucus traps
particles, pathogens like bacteria or viruses and dust and prevents them for getting into the lungs and damaging the cells there
the alveoli are
highly specialised for gas exchange
why are alveoli specialised for gas exchange
- there are many rounded alveolar sacs which give a very large surface area to volume ration
- alveioli and the capillaries around them have thin, single layers of cells to minimise diffusion distance
- ventilation maintains high levels of oxygen and low levels of carbon dioxide in the alveolar air space
- a good blood supply ensures constant supply of blood high in carbon dioxide and low in oxygen
- a layer of moisture on the surface of the alveoli helps diffusion as gases dissolve
muscles are only able too
pull on bones not push on them. this means there must be two sets of intercostal muscles to work antagonistically to facilitate breathing
external intercostal muscles
pull the rib cage up
internal intercostal muscles
pull the rib cage down
the diagphram is
a thin sheet of muscle that separates the chest cavity from the abdomen
during inhalation
the diaphragm contracts and flattens, the external set of intercostal muscles contract to pull the ribs up and out, this increases the volume of the chest cavity (thorax), leading to a decrease in air pressure inside the lungs relative to the outside and so air is drawn in
during exhalation
the diaphragm relaxes it moves upwards back into its domed shape, the external set of intercostal muscles relax so the ribs drop down and in, this decreases the volume of the chest cavity (thorax) leading to an increase in air pressure inside the lungs relative to outside the body and so air is forced out
the external and internal muscles work as
antagonistic pairs (different directions)
when we need to increase the rate of gas exchange in humans
the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly. this is called forced exhalation, it allows a greater volume of gases to be exchanged
smoking causes
chronic obstructive lung disease, coronary heart disease, and increased risks of several different types of cancer, including lung cancer
chemicals in cigarettes include
tar, nicotine, carbon monoxide
nicotine affect on the body
nicotine narrows blood vessels leading to an increased blood pressure, it also increases heart rate. both of these effects can cause blood clots to form in the arteries leading to a heart attack or stroke
carbon monoxide affect on the body
carbon monoxide binds irreversibly to haemoglobin reducing the capacity of blood to carry oxygen. this puts strain on the breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood. it also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes
tar affect on the body
tar is carcinogen and is linked to increased chances of cancerous cells developing in the lungs. it also contributes to COPD which occurs when chronic bronchitis and emphysema occur together
chronic bronchitis is caused by
tar which simulates goblet cells and mucus glands to enlarge, producing more mucus
chronic bronchitis affect on body
it destroys cilia and dirty, bacteria and virus containing mucus builds up, blocking the smallest bronchioles and leading to infections. a smokers cough is an attempt to remove said mucus
emphysema develops as a result of
a frequent infection, phagocytes that enter the lungs release elastase, an enzyme that breaks down elastic fibres in the alveoli. this means that alveoli becomes less elastic and cannot stretch so many of them burst. the breakdown of alveoli reduces the surface area for gas exchange and as it progresses patients become breathless and wheezy-they may need a constant supply of oxygen to stay alive.
apparatus needed to investigate breathing in humans
stop watch, two students
method to investigate breathing in humans
1) work out student As breathing rate at rest
2) student A should then exercise for a set time (at least 4 mins)
3) immediately after exercising count the breaths taken in 15 seconds and multiply by 4 to find breathing per min
4) work out the change in breathing rate
5) do the last step every minute after exercise for 5 mins
6) repeat process for student B
7) finally repeat the whole investigation for each student after a period of rest
results and analysis of investigating breathing in humans
frequency of breathing increases when exercising because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with energy demand. if they can’t keep up this energy demand that will also respire anaerobically producing lactic acid. after exercise has finished the breathing rate remained elevated for a period of time this is because the lactic acid has built up in muscles needs to be released as it lowers the ph of cells and can denature enzymes catalysing cell reactions.
limitations of investigating breathing in humans
it is difficult to control all variables in relation to students being treated etc fitness/food before exercise- solution is to find students of a similar size, general fitness, age, gender and provide each with the same meal before exercise
activity is hard to replicate exactly for each reading- solution is to give students exercise where intensity is easier to control etc runing on a treadmill at a specific speed
breathing rate can vary substantially and changes quickly after exercise finishes- solution is to begin counting the breathing rate as soon as the time interval begins and only measure for 15s or less and then multiple by 4 to get breathing rate per minute
