Respiratory System

Nose 2 chambers lined with mucosa Divided by a septum Separated from the oral cavity by the palate Function: Contains smell receptors, warms, filters and moistens the incoming air. It receives drainage from the paranasal sinuses and nasolacrimal ducts

Pharynx (throat) Mucosa lined muscular tube, containing tonsils for defense 3 sections: Nasopharynx- respiration only Oropharynx- respiration and digestion Laryngopharynx- respiration and digestion

Larynx (voicebox) A cartilage structure that connects the pharynx with the trachea The opening is called the glottis and it is covered by a hood called the epiglottis which prevents aspiration of food or drink into the respiratory passages when swallowing It contains the vocal cords and the prominent thyroid cartilage – the Adam’s Apple

Trachea (windpipe) A smooth tube lined with ciliated mucosa and reinforced with C shaped cartilage rings Extends from the larynx to the primary bronchi

Primary Bronchi (right & left) Subdivision of the trachea, plunges into the hilum of the lung

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Visceral Pleura- covers the surface of the lungs Parietal Pleura- lines the thoracic wall Pleural secretions are between them and decreases friction during breathing

Physiology Gas travels from an area of high pressure to an area of low pressure (diffusion) Atmosphere pressure is always higher than intrapleural pressure

Ventilation is the movement of air into and out of the lungs

Inspiration The diaphragm and external intercostals contract  The superior- inferior volume of the intercostals increases The lungs increase in volume as they cling to the thorax wall Results in a partial vacuum Sucks in air

Expiration The diaphragm relaxes and returns to it’s dome shape  The elastic lungs recoil and their volume decreases Air flows out (passively)

Boyle’s Law Pressure varies inversely with volume P1V1 = P2V2 (when temperature is constant)

Non respiratory air movements Voluntary or reflex activities that move air into or out of the lungs: – Coughing, Sneezing- involuntary clearing Talking, Singing - voluntary Laughing, Crying Hiccupping- irritation of the diaphragm or the phrenic nerve Yawning

Breathing Normal quiet breathing = about 500 ml of air/ breath This is referred to as Tidal Volume (TV)

The amount of air that can be taken in forcibly over the tidal inspiration is the Inspiratory Reserve Volume (IRV)

The amount of air that can be forcibly exhaled after a tidal expiration is the Expiratory Reserve Volume (ERV)

The air that remains in the lungs and cannot be expelled even during strenuous expiration is the Residual Volume (RV) It keeps the lungs inflated

The air that remains in the passages (trachea, bronchi) never reaches the alveoli so there is no exchange. It is called dead space volume and is not part of the total lung capacity

Vital Capacity The total amount of exchangeable air is the vital capacity= VC=TV + IRV + ERV

External Respiration According to the laws of diffusion Gas transport Exchange= air to blood or blood to air Oxygen moves from the alveolar air to the pulmonary blood Carbon dioxide moves from the pulmonary blood to the alveolar air

Internal Respiration Gas exchange at the systemic capillaries Oxygen unloads from the blood Carbon dioxide unloads from the tissue

Cellular Respiration Oxygen is used at the cellular level to breakdown sugars to produce energy Carbon dioxide is produced (waste) from the cellular reaction that breaks down sugar to release energy

Control Nervous system- stretch reflexes in the lungs send a message to the centers in the medulla and pons Physical factors- body temperature, exercise, speech, yawning, singing Voluntary control- as long as it does NOT interfere with homeostasis Emotional- fear, anger, excitement

Chemical Factors Carbon Dioxide levels are the most important stimuli affecting respiration in healthy people Increase or decrease in the levels of CO2 will affect respiratory timing and depth It is controlled in the medulla

pH Hyperventilation causes alkalosis (raises blood pH), apnea, and dizziness Breathing into a paper bag will make you breathe CO2 which adds carbonic acid to the plasma which will bring the blood pH down towards neutral

Pathology COPD- Chronic Obstructive Pulmonary Disease Includes : Emphysema & Chronic Bronchitis 80% associated with smoking or pollution Symptoms: – Dyspnea- labored or difficult breathing – Hypoventilation- CO2 retention, hypoxia, acidosis – Ultimately respiratory failure

Emphysema Permanent enlargement of the alveoli, with destruction of the alveoli walls. Alveoli lose elasticity. Hyperinflation of alveoli makes expiration difficult & requires energy for expiration

Chronic Bronchitis Inhaled irritants leads to chronic mucus production  inflammatory response and fibrosis of tissue  impaired ventilation and gas exchange, and increased bacterial infections

Asthma Characterized by coughing, wheezing, and chest tightness Is a reversible obstructive condition- as long as patients use medication and avoid things that bring on an attack Caused by an immune response (IgE) inflammatory response in the passageways that makes the tissues hypersensitive to any irritants

Tuberculosis Infectious, caused by a bacteria spread by coughing Usually causes fibrous nodules in the lungs Until the 1930s TB caused 1/3 of all deaths of year olds 1940s antibiotics caused a major decline 1990s antibiotic resistance causes a sharp increase