Breathing and more…
Introduction Anatomy and air flow Respiration Mechanics of Breathing Gas Exchange Regulation of Breathing
The respiratory system is designed to perform 2 basic functions: Important homeostatic mechanism – ensures a supply of O 2 (fuel) to the tissues and removal of CO 2 (waste) from the tissues.
The respiratory system is often divided into upper and lower tracts or divisions. Upper tract - located outside the thoracic cavity includes the nose, pharynx and larynx. Lower tract - located within the thoracic cavity includes the trachea, bronchial tree and the lungs. URI or LRI?
Respiratory mucosa Lines most of the air distribution tubes in the system. Layered with protective mucus that serves as the most important air purification mechanism. More than 125 ml of respiratory mucus is produced daily.
Respiratory mucosa The layer of mucus traps dust, pathogens, etc and moves upward to the pharynx with the help of the cilia on the epithelial cells in the respiratory mucosa. Because the cilia beat or move in one direction, the mucus only moves upward. Cigarette smoking paralyzes these cilia and results in accumulations of mucus and “smoker’s cough”.
Air enters the respiratory tract through the The surface of the nasal cavities is moist from mucus and warm from blood flowing just under the surface. Nerve endings in the mucosa are responsible for the sense of smell ( olfactory receptors ).
Nasal cavities Paranasal sinuses : frontal, maxillary, sphenoidal, and ethmoidal drain into the nasal cavities. 3 shelf-like structures, conchae, protrude into each nasal cavity. The conchae are covered with mucosa and increase the surface area over which the air must flow as it passes through the nasal cavity.
Nasal cavities As air moves through the nasal cavities, it is warmed and humidified. ? Breathing through your mouth. When delivering O 2 to a patient it must be humidified or it will dry out the mucosa and cause discomfort and irritation. Drying of the mucosa can cause a nose bleed = epistaxis.
Pharynx – about 5 inches long; 3 sections: Nasopharynx – Oropharynx – Laryngopharynx – The pharynx provides a passageway for food on its way to the esophagus and air on its way to the lungs.
Pharynx The right and left auditory or eustachian tubes open into the nasopharynx. The lining is continuous with the lining of the nasopharynx and middle ear. Infection in one area can spread easily to another. Pharyngeal tonsils (adenoids) are in the nasopharynx; palatine tonsils are in the oropharynx.
Larynx = “voice box” Located just below the pharynx and is composed of several pieces of cartilage. Vocal cords – 2 short elastic tissue bands, covered with mucous membrane, that stretch across the interior of the larynx. Muscles that attach to the larynx cartilages can pull on these cords and increase the tension – higher pitched sound. When they relax – less tension and a lower pitched sound.
Larynx Glottis – space between the vocal cords. Epiglottis – cartilage flap (lid) that partially covers the opening of the larynx; closes off the respiratory tract when swallowing food.
Trachea – “windpipe” is about 4 ½ inches long, extends from the larynx to the bronchi in the chest cavity. Part of the open pathway for air from the outside to enter the lungs. Structure – non-collapsible; 15-20 C-shaped rings of cartilage separated by a small bit of soft tissue maintain opening. Lined with respiratory mucosa.
Trachea Choking on food and other substances (caught in the trachea) kills over 4000 people each year and is the 5 th major cause of accidental death in the US. *** Heimlich maneuver.
Bronchi, bronchioles and alveoli – looks like an upside down tree. Trachea is the main trunk that divides into Right bronchus and left bronchus. As the bronchi enter the lungs they divide into smaller and smaller branches. The smallest tubes whose walls are made only of smooth muscle are called bronchioles.
Bronchi, bronchioles and alveoli Bronchioles further divide into microscopic tubes called alveolar ducts which resemble the main stem of a bunch of grapes. Alveolar ducts end in several alveolar sacs arranged like a clusters of grapes. The walls of the alveolar sacs are made up of numerous alveoli each of which resembles a single grape.
Bronchi, bronchioles and alveoli Alveoli are very effective sites for gas exchange. Their walls consist of one layer of simple squamous epithelium (very thin). Each alveoli is in contact with blood capillaries whose walls are also one cell layer thick. The diffusion of gases across 2 thin walls is very efficient.
Bronchi, bronchioles and alveoli The surface of the alveoli is covered with surfactant. Surfactant reduces the surface tension in the alveoli and keeps them from collapsing into one big sac. IRDS – lack of surfactant; the ability to produce surfactant is not present until late in the pregnancy. Premature infants may not be able to inflate lungs and keep them inflated. Tx – apply prepared surfactant directly to the baby’s airways via a tube.
Lungs Right lung has 3 lobes, left lungs has 2 lobes. Apex = Base =
Pleura Serous membranes that cover the outer surface of the lungs and line the inner surface of the thoracic cavity. ?Names Normally the intrapleural space contains just enough fluid to make both layers of the pleura glide easily against each other as the lungs expand and deflate.
Pleura Pleurisy – inflammation of the pleura that causes pain when the pleural membranes rub together. Pneumothorax – presence of air in the intrapleural space on 1 or both sides. The additional air causes pressures on the lungs and causes them to collapse. Spontaneous or traumatic. ? Hemothorax, pyothorax.
Pulmonary ventilation (or ventilation): breathing, the process that moves air into and out of the lungs/alveoli. Also called external respiration. Respiration : exchange of gases (oxygen and carbon dioxide) between a living organism and its environment. In animals (people) this takes place in the lungs (alveoli) where the air and blood come in close contact.
Internal respiration – process by which an exchange of gases occurs between the blood and the cells of the body. Cellular respiration – actual use of O 2 by cells in the process of metabolism.
Muscles – control the size of the chest cavity. External intercostals – between the ribs move the chest up and out when they contract. Diaphragm – dome shaped muscle between the thoracic and abdominal cavities, moves down when it contracts increasing the volume in the thorax. Hiccups ( singultus ) – involuntary, spasmodic contraction of the diaphragm. Caused by irritation to the phrenic nerve or some types of brain injury.
Pulmonary ventilation has 2 phases: Inspiration or inhalation – moving air into lungs. Expiration or exhalation – moving air out of the lungs. Inspiration occurs as the thorax enlarges (contraction of the external intercostals and diaphragm). Because of the positioning of the pleura, the lungs expand as the thorax expands and air rushes in and down to the alveoli.
Expiration Passive process that begins when the muscles relax decreasing the size of the thorax and lungs – air moves out of the lungs. Forceful expiration – internal intercostals and abdominal muscles contract and depress the rib cage decreasing the depth (front to back) of the thorax. Pressure increases and air flows out of the lungs.
Blood is pumped out of the ? ventricle into the pulmonary ? to the capillaries that surround the alveoli. Gases move by diffusion. What is diffusion?
Blood flowing toward the lungs is low in O 2 and rich in CO 2 the air in the alveoli is rich in O 2 and low in CO 2. Which way does O 2 move? CO 2 ? O 2 combines with the hemoglobin in the RBCs to form oxyhemoglobin and is transported to the tissues where the cells use it in cellular respiration.
CO 2 moves into the lungs and leaves the body during expiration. At the tissues O 2 is low and CO 2 high whereas the blood reaching them is just the opposite. O 2 moves out of and CO 2 moves into the blood. Most of the CO 2 is carried in the blood as a bicarbonate ion, some is dissolved in the plasma and some combines with hemoglobin to form carbaminohemoglobin.
Spirometer – Tidal volume – Vital capacity –
Expiratory reserve – amount of air that can be forcibly exhaled after exhaling the tidal volume. Inspiratory reserve – amount of air that can be forcibly inhaled over and above normal inhalation. Residual volume – air that remains in the lungs after the most forceful expiration. Residual volume + Vital Capacity =
Normal respiration depends on proper functioning of the muscles of respiration. Normal respiratory rate – 12-20 (or 10-14, or 16-18) breaths/min. The muscles are stimulated by nervous impulses that originate in the respiratory control centers located in the medulla and pons of the brain.
Receptors in the brain and blood vessels sense the level of CO 2 (or pH). When it is high receptors send impulses to the respiratory control center to increase respiratory rate and depth. Receptors in the blood vessels also respond to decreased O 2 levels when blood PO 2 falls below 60 mmHg. Example COPD.
The 2 most important control centers are in the medulla and are called the inspiratory and expiratory centers. Breathing can be voluntary – to a point, however CO 2 levels are much more powerful in controlling respiration than conscious control. Ex. breath holding and hyperventilation.
Respiratory – change in gas exchange; lungs Acidosis – blood pH is acid due to increased levels of CO 2 in the blood. Alkalosis – blood pH is alkaline or basic due to decreased levels of CO 2 in the blood. In any fluid that contains water: CO 2 + H 2 O → H 2 CO 3 → H + + HCO 3 - The brain senses the H + concentration that develops in the CSF because CO 2 diffuses into the CSF from the blood.
Metabolic – change in pH that is not due to changes in gas exchange in the lungs. Acidosis – diabetes mellitus, kidney disease or severe diarrhea increase H + in the blood. *Respiratory compensation – increased rate and depth. Alkalosis – vomiting, medications – decrease H + in the blood. *Respiratory compensation – decreased rate and depth.