Respiratory System

1. Human respiratory system brings in oxygen and releases carbon dioxide
• oxygen drawn in through respiratory tract, then delivered to the blood
• above process called external respiration
• exchange of gases between blood and cells of body is called internal respiration
2. Cellular respiration vs. Respiration
• respiration is transport of oxygen from outside air to cells of body, and carbon dioxide in the opposite direction
• cellular respiration is the biochemical definition of respiration
• both very different from one another
• cellular respiration takes place in individual cells, while respiration involves transport of metabolites between organism and the external environment 
3. Structures of respiratory system
• nose and nasal cavity: filter, warm, and moisten the inhaled air
• nose hairs and mucus in the nose catch airborne particles and prvent them from reaching the lungs
• air passes through pharynx, a long tube shared by digestive system
• food and air pass through pharynx
• epiglottis closes over trachea when food is swallowed to prevent choking or inhaling food
• pharynx is important for vocalization in humans
• larynx (voicebox) is found just below the area where the pharynx splits into trachea and esophagus
• voice is generated in larynx
• air in lungs is needed for speech
• trachea (windpipe) divides into right and left bronchi in lungs
• bronchi branches out into smaller bronchioles (do not contain cartilage) 
• bronchioles lead to alveoli, where most gas exchange occurs
4. Respiration of oxygen (four stages) 
• ventilation from atmosphere into alveoli of lungs
• pulmonary gas exchange from alveoli into pulmonary capillaries
• gas transport from pulmonary capillaries through circulation to peripheral capillaries in organs
• peripheral gas exchange from tissue capillaries into cells and mitochondria
5. Ventilation (in detail) 
• air enters body through nose
• it is warmed, filtered, and passed through nasal cavity 
• passes larynx and move into trachea
• bronchi are lined with ciliated epithelium and mucus-producing cells
• breathing in is an active movement
• contraction of diaphragm uses ATP
• diaphragm: muscle found below the lungs
• contraction of diaphragm causes volume of chest cavity to increase, and air pressure inside lungs decrease
• pressure different causes air to rush into lungs
• relaxation of diaphragm causes lungs to recoil, and air is pushed out of the lungs
• exhaling is passive process powered by elastic recoil of the chest
6. Pulmonary gas exchange
• gas exchange occurs in alveoli by diffusion of gases between alveoli and blood passing in lung capillaries
• diffusion: high concentration to low concentration
• breathing results in loss of water from body
• oxygen transported across membrane of alveoli, and attracted to the hemoglobin within red blood cell
• oxygenated blood travels through aorta, to smaller arteries, arterioles, and into peripheral capillaries where gas exchange occurs
7. Peripheral gas exchange
• oxygen concentration in body cells is low, so oxygen diffuses from blood into body cells when it reaches peripheral capillaries
• carbon dioxide diffuses form cells to capillaries
• usually in the form of biocarbonate (HCO3) 
• biocarbonate is picked up by red blood cell, and turned into carbonic acid
• gas exchange between body and environment occurs in alveoli
8. Gas exchange and homeostasis
• equilibrium between carbon dioxide and carbonic acid is important for controlling acidity of body fluids
• if proper respiration is interrupted: 
• respiratory acidosis: arterial blood contains too much carbon dioxide, which drops the blood's pH
• respiratory acidosis results form increased respiration, causing blood pH to rise
9. Control of breathing by respiratory system
• can be controlled consciously and unconsciously
• conscioulsy: yoga, swimming, karate
• unconsciously: speech or vocal training
• muscular contraction and relaxation controls rate of expansion and constriction of lungs
• when carbon dioxide levels increase, causing blood pH to drop, the medulla (brain part that controls breathing) sends impulses to diaphragm and muscle between ribs
• causes them to contract and increase rate of breathing
• without breathing, oxygen levels fall, and can lead to permanent brain damage, followed by death
• healthy person cannot stop breathing voluntarily
• not inhaling leads to great air hunger
• not breathing leads to loss of consciousness, and autonomic nervous system takes over and resumes breathing
10. Inhalation
• started by diaphragm and supported by external intercostal muscles
• active process that needs ATP 
• normal respiration is 10-18 breaths per minute
• average adult will exchange 500 mL to 700 mL of air
• breath capacity is called lung volume, or tidal volume
11. Exhalation
• generally a passive process
• forced exhalation is carried out by abdominal and internal intercostal muscles
• lungs have natural elasticity, so they recoil from stretch of inhalation, and air flows out until pressures in chest and atmosphere reach equilibrium
12. Respiratory diseases and disorders
• term for diseases of the lung, bronchial tubes, trachea, and throat
• emphysema
• chronic lung disease
• loss of elasticity of lung tissue
• destruction of elastic structures that support alveoli and capillaries that feed alveoli, causing them to becoming hard and stiff 
• walls of alveoli break down and alveoli become larger
• amount of oxygen that can enter the blood per breath is reduced because large alveoli are not efficient
• symptoms: shortness of breath on exertion and and expanded chest
• damage to alveoli is irreversible
• caused mainly by smoking
1. leading cause of emphysema
• bronchitis
• inflammation of bronchi
• acute bronchitis caused by virus or bacteria, and may last several days or weeks
• characterized by cough and mucus production
• symptoms related to inflammation of airways and phlegm production
• chronic bronchitis usually part of syndrome called chronic obstructive pulmonary disease
• defined clinically as a persistent cough that produces mucus
1. at least three months in two consecutive years
• asthma
• chronic illness where airways narrow and becomes inflamed
• excessive amounts of mucus are made by the lungs
• happens in response to one or more triggers
1. exposure to allergen (mold, dust, or pet hair) 
• most common triggers in children are viral illnesses
1. causes symptoms such as wheezing, shortness of breath, chest tightness, and more breathing distress
• most patients feel well between asthma attacks
• may remain short of breath after exercise for longer periods of time than others
• symptoms of asthma can be controlled with combination of medicines and environmental changes
• pneumonia
• alveoli become inflamed and fill with fluid
• gas exchange cannot happen across alveoli membrane
• can result from variety of causes
1. infection with bacteria, viruses, fungi, or parasites
2. chemical and physical injury to the lungs
• symptoms include cough, chest pain, fever, and difficulty in breathing
• treatment depends on cause
• bacterial pneumonia is treated with antibiotics
• tuberculosis (TB) 
• common and deadly infectious disease
• caused by bacteria Mycobacterium tuberculosis
• most commonly attacks lungs
1. can also affect central nervous system, lymphatic system, circulatory system, genitourinary system, bones, joints, and skin
• 1/3 of world has been exposed to TB bacterium
• lung cancer
• epithelial (inner lining) tissue in lungs grow out of control
• leads to invasion of nearby tissue and growth of tumor beyond lungs
• most common cause of cancer-related death
• common symptoms: shortness of breath, coughing, and weight loss
• most common cause: exposure to tobacco smoke
1. radon gas, asbestos, and air pollution