Chapter 13 – Part 1 The Respiratory System

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

Function of the Respiratory System Oversees gas exchanges between the blood and external environment Exchange of gasses takes place within the lungs in the alveoli Passageways to the lungs purify, warm, and humidify the incoming air

The Nose The only externally visible part of the respiratory system Air enters the nose through the external nares (nostrils) The interior of the nose consists of a nasal cavity divided by a nasal septum

Figure 13.2

Anatomy of the Nasal Cavity Olfactory receptors for the sense of smell are located in the mucosa on the slitlike superior part of the nasal cavity The rest of the cavity is lined with respiratory mucosa Warm the air Moistens the air Traps incoming foreign particles (cleanse)

Anatomy of the Nasal Cavity The ciliated cells of the nasal mucosa create a gentle current that moves contaminated mucous posteriorly towards the throat (pharynx) It is then swallowed and digested by stomach juices. When it is extremely cold, these cilia become sluggish, allowing mucus to accumulate in the nasal cavity and to dribble outward through the nostrils. This is why you have a “runny” nose on a cold day.

Nosebleeds The respiratory mucosa rests on a rich network of thin-walled veins (warms the air as it flows by). Because of the superficial location of these blood vessels, nosebleeds are common and often profuse.

Anatomy of the Nasal Cavity The lateral walls of the nasal cavity have three projections or lobes called conchae Increases surface area Increases air turbulence within the nasal cavity Helps to deflect inhaled particles onto the mucus-coated surfaces, where they are trapped and prevented from entering the lungs.

Anatomy of the Nasal Cavity The nasal cavity is separated from the oral cavity by the palate Anterior hard palate (bone) Posterior soft palate (muscle)

Cleft Palate Cleft palate – The bones forming the palate fail to fuse medially Genetic defect Results in breathing difficulties and problems with oral cavity functions (chewing and speaking)

Paranasal Sinuses The nasal cavity is surrounded by a ring of paranasal sinuses. Are located in the: Frontal bone Sphenoid bone Ethmoid bone Maxillary bone

Paranasal Sinuses Function of the sinuses Lighten the skull Act as resonance chambers for speech Produce mucus that drains into the nasal cavity The suctioning effect created by nose blowing helps to drain the sinuses. The nasolacrimal ducts, which drain tears from the eyes, also empty into the nasal cavities

Sinusitis Sinusitis – sinus inflammation Difficult to treat Can cause marked changes in voice quality When the passageways connecting the sinuses to the nasal cavity are blocked with mucus or infectious matter, the air in the sinus cavities is absorbed The result is a partial vacuum and a sinus headache

Pharynx (Throat) Pharynx - Muscular passage from nasal cavity to larynx About 5 inches long Commonly called the throat Serves as a common passageway for food and air Is continuous with the nasal cavity anteriorly via the internal nares

Pharynx (Throat) Three regions of the pharynx: Nasopharynx – superior region behind nasal cavity Oropharynx – middle region behind mouth Laryngopharynx – inferior region attached to larynx The oropharynx and laryngopharynx are common passageways for air and food Air then passes through the larynx, while food is directed into the esophagus posteriorly

Structures of the Pharynx The auditory tubes, which drain the middle ear, open into the nasopharynx Since the mucosae of these two regions are continous, ear infections may follow a sore throat or other types of pharyngeal infections

Structures of the Pharynx Tonsils (clusters of lymphatic tissue) are also found in the pharynx Their job is to trap and remove any bacteria or other foreign pathogens entering the throat Pharyngeal tonsil – located high in the nasopharynx Palatine tonsils – located in the oropharynx at the end of the soft palate Lingual tonsils – located at the base of the tongue

Tonsillitis Tonsillitis – Inflammation and swelling of the pharyngeal tonsil Can occur during a bacterial infection It obstructs the nasopharnyx and forces the person to breathe through the mouth In mouth breathing, air is not properly moistened, warmed, or filtered before entering the lungs Years ago, the belief was that the tonsils were more trouble than they were worth and they were routinely removed. Now, this is no longer necessary because of the large use of antibiotics

Larynx (Voice Box) Functions of the Larynx: Routes air and food into proper channels Plays a role in speech (voice production) Acts as an airway Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the Larynx Thyroid cartilage Largest hyaline cartilage Shield-shaped Protrudes anteriorly Commonly called the Adam’s apple

Structures of the Larynx Epiglottis Protects the superior opening of the larynx Routes food to the esophagus and air toward the trachea The epiglottis moves positions when swallowing When we are not swallowing: the epiglottis does not restrict the passage of air into the lower respiratory passages When we are swallowing: the larynx is pulled upward and the epiglottis tips, forming a lid over the opening of the larynx; this routes food into the esophagus

Structures of the Larynx Palpate your larynx by placing your hand midway on the anterior surface of your neck. Swallow. Can you feel the larynx rising as you swallow?

Cough Reflex If anything other than air enters the larynx, a cough reflex is triggered to expel the substance and to prevent it from continuing into the lungs. Because this protective reflex does not work when we are unconscious, it is never a good idea to try to give fluids to an unconscious person when attempting to revive him or her.

Structures of the Larynx Vocal cords (vocal folds) Pair of folds Vibrate with expelled air to create sound Allows us to speak Glottis – the slitlike passageway between the vocal cords

Trachea (Windpipe) Connects larynx with bronchi About 4 inches long Lined with ciliated mucosa Beat continuously in the opposite direction of incoming air Propels mucus loaded with dust and other debris away from lungs to the throat, where it can be swallowed or spat out

The Trachea and Smoking Smoking inhibits ciliary activity and ultimately destroys the cilia Without these cilia, coughing is the only means of preventing mucus from accumulating in the lungs

Trachea (Windpipe) The trachea is fairly rigid because its walls are reinforced with C-shaped hyaline cartilage These rings form two purposes: Support the trachea and keep it open in spite of the pressure changes that occur during breathing Allows it to expand anteriorly when we swallow a large piece of food

Heimlich Maneuver Heimlich maneuver – a procedure in which the air in a person’s own lungs is used to “pop out,” or expel, an obstructing piece of food Because the trachea is the only way air can get into the lungs, tracheal obstruction is life- threatening Many people have suffocated after choking on a piece of food that suddenly closed off the trachea Has saved many people from choking to death

Primary Bronchi The right and left primary bronchi is formed by the division of the trachea Enters the lung at the hilus (medial depression) Right bronchus is wider, shorter, and straighter than left Consequently it is the more common site for an inhaled foreign object to become lodged Bronchi subdivide into smaller and smaller branches By the time air enters the bronchi, it is warmed, cleansed of most impurities, and well humidified

Lungs The paired lungs are fairly large organs Occupy most of the thoracic cavity Apex is near the clavicle (narrow, superior portion) The broad base rests on the diaphragm (inferior portion) The bronchi enters the lung at the hilus (medial depression)

Lungs Each lung is divided into lobes by fissures Left Lung - Has two lobes Right Lung - Has three lobes

Coverings of the Lungs Pulmonary (visceral) pleura covers the lung surface Parietal pleura lines the walls of the thoracic cavity Pleural fluid fills the area between layers of pleura to allow gliding during breathing movements Can slide easily from side to side across one another, but resists being pulled apart.

Lungs

Coverings of the Lungs Pleurisy – Inflammation of the pleura Can be caused by the decreased secretion of pleural fluid The pleural surfaces become dry and rough Results in friction and stabbing pain with each breath

Respiratory Tree Divisions This branching and rebranching within the lungs is often referred to as the bronchial or respiratory tree: Primary bronchi Secondary bronchi Tertiary bronchi Bronchioles Terminal bronchioles

Bronchioles Bronchioles - Smallest branches of the bronchi All but the smallest branches have reinforcing cartilage

Bronchioles Terminal bronchioles end in alveoli, or air sacs.

Respiratory Zone The respiratory zone is the only site of gas exchange Includes the following structures: Respiratory bronchioles Alveolar ducts Alveolar sacs Alveoli All other respiratory passages are conducting zone structures Serve as conduits to and from the respiratory zone.

Alveoli There are millions of the clustered alveoli, which resemble bunches of grapes. They make up the bulk of the lungs Consequently, the lungs are mostly air space In spite of their relatively large size, the lungs weigh only about 2 ½ pounds, and they are soft and spongy

Alveoli Structure of alveoli Alveolar duct Alveolar sac Alveoli Gas exchange takes place within the alveoli in the respiratory membrane

Alveoli Structure of alveoli Alveolar duct Alveolar sac Alveoli Gas exchange takes place within the alveoli in the respiratory membrane

Respiratory Membrane Respiratory Membrane (Air-Blood Barrier) – Has gas (air) flowing past on one side and blood flowing past on the other Made up of the alveolar and capillary walls and their fused basement membranes.

Respiratory Membrane The walls of the alveoli are composed largely of a single, thin layer of squamous epithelial cells The thinness of their walls is hard to imagine, but a sheet of tissue paper is much thicker The external surfaces of the alveoli are covered with a “cobweb” of pulmonary capillaries

Respiratory Membrane Alveolar pores connect neighboring air sacs and provide alternate routes for air to reach alveoli In case feeder bronchioles have been clogged by mucus or otherwise blocked

Gas Exchange Gas exchanges occur by simple diffusion through the respiratory membrane Oxygen enters the blood Carbon dioxide enters the alveoli The total gas exchange surface provided by the alveolar walls is 40 times greater than the surface of your skin

Gas Exchange The final line of defense for the respiratory system is in the alveoli Macrophages wander in and out of the alveoli picking up bacteria, carbon particles, and other debris Surfactant coats the gas-exposed alveolar surfaces Lowers the surface tension of the film of water lining each alveolar sac so that the alveoli do not collapse between each breathe

Respiratory Membrane (Air-Blood Barrier)