The Respiratory System CHAPTER 13 Organs of the

The Respiratory System CHAPTER 13

Organs of the Respiratory system l Nose l Pharynx l Larynx l Trachea l Bronchi l Lungs – alveoli

Functions of the Respiratory System l Gas exchanges between the blood and external environment u Occurs in the alveoli of the lungs l Passageways to the lungs purify, humidify, and warm the incoming air

The Nose l Only externally visible part of the respiratory system l Consists of nasal bones, extensions of frontal and maxillary bones l Air enters the nose through the external nares (nostrils) l The interior of the nose consists of a nasal cavity u divided by a nasal septum

Anatomy of the Nasal Cavity l Olfactory receptors are located in the mucosa on the superior surface of nasal cavity l The rest of the cavity is lined with respiratory mucosa l Functions: Moistens air u Traps incoming foreign particles u

Anatomy of the Nasal Cavity l Lateral walls have projections called conchae u Increases surface area u Increases air turbulence within the nasal cavity l The nasal cavity is separated from the oral cavity by the palate u Anterior hard palate (bone) u Posterior soft palate (muscle)

Paranasal Sinuses l Cavities within bones surrounding the nasal cavity are called sinuses l Sinuses are located in the following bones u u Frontal bone Sphenoid bone Ethmoid bone Maxillary bone l Function of the sinuses u u u Lighten the skull Act as resonance chambers for speech Produce mucus that drains into the nasal cavity

Pharynx (Throat) l Muscular passage from nasal cavity to larynx l Three regions of the pharynx u Nasopharynx – superior region behind nasal cavity u Oropharynx – middle region behind mouth u Laryngopharynx – inferior region attached to larynx l The oropharynx and laryngopharynx are common passageways u for air and food

Structures of the Pharynx l Tonsils of the pharynx u Pharyngeal tonsil (adenoids) are located in the nasopharynx u Palatine tonsils are located in the oropharynx u Lingual tonsils are found at the base of the tongue

Larynx (Voice Box) l Routes air and food into proper channels l Plays a role in speech l Made of eight rigid hyaline cartilages u and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the Larynx l Thyroid cartilage u u Largest hyaline cartilage Protrudes anteriorly (Adam’s apple) l Epiglottis u u u Superior opening of the larynx Routes food to the esophagus and air toward the trachea When swallowing, the epiglottis rises and forms a lid over the opening of the larynx

Structures of the Larynx l Vocal cords (vocal folds) u Vibrate with expelled air to create sound (speech) l Glottis – opening between vocal cords

l Connects larynx with bronchi, approx. 4 inch long tube l Lined with ciliated mucosa u Beat continuously in the opposite direction of incoming air u Expel mucus loaded with dust and other debris away from lungs to the throat l Walls are reinforced with C -shaped hyaline cartilage Trachea (Windpipe)

l Formed by division of the trachea l Enters the lung at the hilus (medial depression) l Right bronchus is wider, shorter, and straighter than left l Bronchi subdivide into smaller and smaller branches Primary Bronchi

Respiratory Tree Divisions l Primary bronchi l Secondary bronchi l Tertiary bronchi l Bronchioles l Terminal bronchioles l These passages are conducting zone

Respiratory Zone Terminal bronchioles branch into u Respiratory bronchioles u Alveolar ducts u Alveolar sacs u Alveoli (air sacs) u l Site of gas exchange = alveoli only

Lungs l Occupy most of the thoracic cavity Superior portion (apex) is near the clavicle u Base rests on the diaphragm (inferior portion) u u Each lung is divided into lobes by fissures • Left lung – two lobes • Right lung – three lobes

Lungs l Pulmonary (visceral) pleura covers the lung surface l Parietal pleura lines the walls of the thoracic cavity l Pleural cavity is filled with pleural fluid l Pleural fluid: acts as a lubricant and helps hold the two membranes close together

Respiratory Membrane (Air-Blood Barrier) l Alveolar walls are composed of thin layer of squamous epithelial cells l External surfaces of alveoli are covered by Pulmonary capillaries l On one side of the respiratory membrane is air and on the other side is blood flowing past

Gas Exchange l Gas exchange through respiratory membrane occurs by diffusion u u Oxygen enters the blood Carbon dioxide enters the alveoli l Alveolar macrophages provide protection by picking up bacteria, carbon particles, and other debris l Surfactant (a lipid molecule) coats alveolar surfaces l Surfactant lowers the surface tension of water film lining the alveolar sac, so alveoli do not collapse

Events of Respiration l Respiratory system supply the body oxygen and dispose of carbon dioxide l Respiration includes four process: l Pulmonary ventilation – movement of air into & out of the lungs (breathing) l External respiration – gas exchange between pulmonary blood and alveoli u Oxygen is loaded into the blood u CO 2 is unloaded from the blood l Respiratory gas transport – transport of O 2 from lungs to tissues via blood, CO 2 from tissue to lungs via blood l Internal respiration – gas exchange between blood and tissue cells in systemic capillaries

Mechanics of Breathing (Pulmonary Ventilation) l Two phases u Inspiration – flow of air into lung u Expiration – air leaving lung

Inspiratio n l Diaphragm and external intercostal muscles contract l The size of the thoracic cavity increases l External air is pulled into the lungs due to Increase in intrapulmonary volume u Decrease in gas pressure u

Expirati on l Largely a passive process which depends on natural lung elasticity l As muscles relax, air is pushed out of the lungs due to u u Decrease in thoracic and intrapulmonary volume Increase in gas pressure l Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage

Respiratory Volumes and Capacities l Normal breathing moves about 500 ml of air with each breath u Referred to as tidal volume [TV] l Many factors that affect respiratory capacity A person’s size u Sex u Age u Physical condition u

Respiratory Volumes and Capacities l Inspiratory reserve volume (IRV) u u Amount of air that can be taken in forcibly over the tidal volume Usually between 2100 and 3200 ml l Expiratory reserve volume (ERV) u u Amount of air that can be forcibly exhaled after tidal expiration Approximately 1200 ml l Residual volume u u Air remaining in lung after forceful expiration About 1200 ml

Respiratory Volumes and Capacities l Vital capacity u The total amount of exchangeable air, 4800 ml u Vital capacity = TV + IRV + ERV u Dead space volume • Air that remains in conducting zone and never reaches alveoli • About 150 ml

Respiratory Volumes and Capacities l Functional volume u Air that actually reaches the respiratory zone, contributes to gas exchange is usually about 350 ml l Respiratory capacities are measured with a spirometer

Respiratory Sounds l Sounds are monitored with a stethoscope l Bronchial sounds – u produced by air rushing through trachea and bronchi l Vesicular breathing sounds – u soft sounds of air filling alveoli

External Respiration l Oxygen loaded into the blood l The alveoli always has more oxygen than the blood u Oxygen moves by diffusion towards the area of higher conc. to lower conc. to capillary u Pulmonary capillary blood gains oxygen

External Respiration l Carbon dioxide unloaded out of the blood u Blood returning from tissues has higher concentrations of carbon dioxide than alveoli u CO 2 moves from capillaries to alveoli and flushed out of lungs during expiration l Blood leaving the lungs is oxygen- rich and carbon dioxide-poor

Gas Transport in the Blood l Oxygen is transported in the blood in two ways: u Most oxygen attached to hemoglobin in RBCs to form oxyhemoglobin (Hb. O 2) u A small dissolved amount of O 2 is carried in the plasma

Gas Transport in the Blood l Carbon dioxide transport in the blood u Most is transported in the plasma as bicarbonate ion (HCO 3–) u Conversion of CO 2 to bicarbonate ion takes place in RBCs then diffuse into plasma u A small amount of CO 2 is carried inside red blood cells on hemoglobin, but at different binding sites than those of oxygen

Internal Respiration l Exchange of gases between blood and tissue cells l An opposite reaction to what occurs in the lungs Carbon dioxide diffuses out of tissue to blood u Oxygen diffuses from blood into tissue u

Neural Regulation of Respiration l Activity of respiratory muscles, diaphragm and external intercoastals is transmitted to and from the brain by u the phrenic and intercostal nerves l medulla u regulates basic rhythm of respiration

Neural Regulation of Respiration l Pons l Fine tuning of respiratory rate l Normal respiratory rate (eupnea) is u 12– 15 respirations per minute l Hypernia is u u increased respiratory rate often due to extra oxygen needs Exercise

Respiratory Rate Changes Throughout Life l Newborns – 40 to 80 respirations per minute l Infants – 30 respirations per minute l Age 5 – 25 respirations per minute l Adults – 12 to 18 respirations per minute l Rate often increases somewhat with old age

Factors Influencing Respiratory Rate and Depth : physical and chemical factors Physical factors Increased body temperature u Exercise u Talking u Coughing u l Volition (conscious control): singing , swimming l Emotional factors: anxiety attack

Factors Influencing Respiratory Rate and Depth : physical and chemical factors Chemical factors u Carbon dioxide levels • Increased carbon dioxide increases respiration • Changes in carbon dioxide act directly on the medulla oblongata u Oxygen levels • Changes in oxygen concentration in the blood are detected by chemoreceptors in the aorta and carotid artery • Information is sent to the medulla oblongata

Respiratory disorders l COPD l Lung cancer l SIDS l Asthma l Cystic fibrosis

Chronic Obstructive Pulmonary Disease (COPD) chronic emphysema and bronchitis l Most victims retain carbon dioxide, are hypoxic and have respiratory acidosis u Those infected will ultimately develop respiratory failure u Labored breathing (dyspnea) becomes progressively more severe u Coughing and frequent pulmonary infections are common u Patients almost always have a history of smoking

Emphysema l Alveoli enlarge as adjacent chambers break through l Airways collapse during expiration

Chronic Bronchitis l Mucosa of the lower respiratory passages becomes severely inflamed l Pooled mucus impairs ventilation and gas exchange l Risk of lung infection increases

Lung Cancer l Accounts for 1/3 of all cancer deaths in the United States l Increased incidence associated with smoking l Tumors in the lungs

Sudden Infant Death syndrome (SIDS) l healthy infant stops breathing and dies during sleep l Some cases are thought to be a problem of the u neural respiratory control center l One third of cases appear to be due to u heart rhythm abnormalities

Asthma l Chronic inflamed hypersensitive bronchiole passages l Response to irritants with Dyspnea ( labored breathing), u coughing, and wheezing u

l Cystic fibrosis u over secretion of thick mucus u clogs the respiratory system

Aging Effects l Elasticity of lungs decreases l Vital capacity decreases l Blood oxygen levels decrease l Stimulating effects of carbon dioxide decreases l More risks of respiratory tract infection