Bio Rev

•Breathing = VENTILATION •When A.Pressure of ATMOSPHERE is GREATER than the A.Pressure INSIDE the lungs, air is forced into the alveoli. This is INSPIRATION •When the A.Pressure in the LUNGS is GREATER than the in the ATMOSPHERE, air is forced OUT of the lungs. This is EXPIRATON •Pressure changes brought about by two sets of muscles: THE DIAPRHAGM = SHEET of MUSCLE seperating THORAX from ABDOMEN •The Intercostal muscles: 1) INTERNAL INTERCOSTAL MUSCLES - contract -> inspiration, 2) EXTERNAL INTERCOSTAL MUSCLES - contract -> expiration Inspiration = EXTERNAL contract, INTERNAL relax. Ribs pulled UP and OUT, increasing volume of THORAX. Diaphragm muscles CONTRACT, it flattens, which further increases volume of THORAX. Increased volume in thorax = LUNG PRESSURE DROPS => Atmospheric pressure is GREATER than LUNG pressure so AIR is FORCED in! Expiration = INTERNAL contract, EXTERNAL relax. Ribs pulled DOWN and INWARDS, reducing volume of THORAX. Diaphragm muscles RELAX, it goes back to dome position, which reduces volume of THORAX. Reduced volume in thorax = LUNG PRESSURE INCREASES => Atmospheric pressure is LESS than LUNG pressure so AIR is FORCED out! NOTE: The SPRING BACK OF LUNGS causes air out in normal situations. ONLY IN EXERCISE MUSCLES AID! Tidal Volume = Volume NORMALLY taken in at EACH BREATH when the body is at REST. Usually ~0.5dm^3 Ventilation Rate = the number of breaths taken in ONE minute. This is ~12-20 breaths in a HEALTHY adult. Pulmonary Ventilation [dm^3min^-1] = Tidal Volume [dm^3] x Ventilation Rate [min-1] Essential Features of exchange surfaces: •Large SA:Vol ratio - area of exchange increased -> rate increased •VERY THIN - short diffusion pathway => rapid crossing -> rate increased •PARTIALLY PERMEABLE - to allow selected materials [O2 here] to diffuse easily •Movement of environmental medium [air] to maintain a DIFFUSION GRADIENT •Movement of internal medium [blood] to maintain DIFFUSION GRADIENT Fick's Law: Diffusion is PROPORTIONAL [not EQUAL?] to: Surface Area x Difference in Concentration Length of Diffusion path ---Alveoli Bonuses: •300 million alveoli in each human lung. •Total S:A = 70m^2 - 1/2 tennis court - HUUGE •Alveolus lined with EPITHELIAL cells 0.05 microM to 0.3 microM thick. •Around each alveolus = network of PULMENARY CAPILLARIES = thin [1 cell thick 0.04-0.2 microM] walls for short diffusion pathway! •Red blood cells slowed allowing more time for DIFFUZION •Distance between air + blood cells reduced as red blood cells are flattened against capillary walls •Walls of Alveoli + Capillaries = very thing = short dif. pathway

•Alveoli + Capillaries = HIGH S:A = More ground for dif. •Constant gradient due to blood flow + air flow. ---Tubercu:

•Caused by MYCOBACTERIUM TUBERCULOSIS or MYCOBACTERIUM BOVIS.

•30% of world have one or other form of TB bacteria in their bodies •Symptoms of PULMONARY TUBERCULOSIS [lungs] = cough, tiredness, loss of appetite + weight loss. Fever + blood coughing CAN occur if untreated •Transmitted by airborne particles - sneezing shouting etc. •Transmitted in unpasteurized milk - MYCOBACTERIUM BOVIS •Crowding = increased risk of transmission! Once bacteria is inhaled to unimmune person: •1) Bacteria grow + divide in upper lung regions with big O2 supply [ respi ] •2) The body's immune system responds and W.B.Cells accumulate at bacteria to INGEST! •3) This leads to inflammation + enlargement of lymph nodes that drain that area of the lungs. This is called PRIMARY INFECTION and usually occurs in children. •4)In a healthy person there are FEW symptoms, if ANY, and the infection is under controll in a few weeks. Good Job White Blood Cells! Wait a minute, some bacteria Dr. Evils remain! •5)Many years later these can come back to cause a second infection. This is called postprimary tuberculosis and occurs in adults •6)This is also in upper lungs but not so easily controlled. Bacteria destroy lung tissue => cavities => scars where lungs repair! •7) Sufferer coughs up damaged lung tissue [EWW] containing bacteria along with blood. Without treatment TB spreads to rest of body and can be fatal!! Prevention + Control of TB: 1) Vaccines, 2) Hygiene, 3) No overcrowding, 4) Good supplies for immune system - nutrients ETC! 5) Quick treatment when noticed. --Pulm Fibro: Microscopic injuries cause lung tissue to turn fibrous + thick. This reduces lung elasticity. Symptoms + causes below: •Shortness of breath = considerable air space occupied by fibrous tissue. Less air, less oxygen! + Thickened alveoli Epithelium = diffusion pathway increased = slower rate! •Chronic Dry Cough = Air meats fibrous tissue as obstacle. Body's like ''WTF'' and tries to cough it out! But it's unmovable and coughing = futile! •Pain + Chest discomfort due to pressure damage from the mass of the fibrous tissue and scarring due to coughing. •Weakness + Fatigue due to reduced O2 Exact cause is unclear, but microscopic lung injuries are bad! AVoid harmful particulates! -Asthma:

This is an ALLERGY. Caused by ALLERGENS. Common ones: •pollen, animal fur, faeces of house dust mite, air pollutants [sulfur diox, nitrogen ox, ozone] cold air, infection, anxiety, and stress! •These cause W.B.Cells on linings of the Bronchi and Bronchioles to release HISTAMINE: 1) Lining of airways becomes inflamed, 2) Cells of ephitleial lining secrete big mucus quantities, 3) Fluid leaves capillaries and enters airways [flooding], 4) Muscles surrounding bronchioles contract + constricts airways Overall, big resistance to flow of air into alveoli => Hard to ventilate lungs => diffusion gradient low. Symptoms : expla below: •Breathing difficulty, wheezing sound [air passing through constricted bronchi+oles],a tight chest feeling [constricted and pressured lungs], coughing [reflex to obstructed bronchi] Genetics play a role in which allergens youre more allergic too! Cleaner lifestyles = less exposure = more susceptability. -Emphy: Elastin permanently stretched = lungs no longer able to contract and force air out of alveoli. Surface Area of alveoli reduced, and they sometimes burst, arrgh! Little or any exchange of O2 can take place across these f'd up lungs. Symptoms + expla below: •Shortness of Breath [Hard to exhale therefore old air remains + general amount of gas exchange = low] •Chronic cough [ Body wants to remove bad things but theyre stuck inside cause theyre tissue] •Blue skin tint [ Lack of O2 in blood] Smoking increases the chance of this bro! Lung Disease risk factors: •Smoking - 90% of people suffering smoke or have smoked •Air pollution = allergens + harmful substances •Genetic make up = susceptability and immune system response •Infections = scarred tissue etc •Occupation = hazard areas