Chapter 13 – Part 1The Respiratory System

Organs of the Respiratory systemOrgans of the Respiratory system

Nose

Pharynx

Larynx

Trachea

Bronchi

Lungs – alveoli

Function of the Respiratory SystemFunction 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 NoseThe 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 CavityAnatomy 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 CavityAnatomy 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.

NosebleedsNosebleeds

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 CavityAnatomy 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 CavityAnatomy 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 PalateCleft 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 SinusesParanasal 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 SinusesParanasal Sinuses

Function of the sinuses

1. Lighten the skull

2. Act as resonance chambers for speech

3. 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

SinusitisSinusitis

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 (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)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 PharynxStructures 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 PharynxStructures 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

TonsillitisTonsillitis 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)Larynx (Voice Box)

Functions of the Larynx:

1. Routes air and food into proper channels

2. Plays a role in speech (voice production)

3. Acts as an airway

Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the LarynxStructures of the Larynx

Thyroid cartilage

Largest hyaline cartilage

Shield-shaped

Protrudes anteriorly

Commonly called the Adam’s apple

Structures of the LarynxStructures 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 LarynxStructures 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 ReflexCough 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 LarynxStructures 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)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 SmokingThe 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)Trachea (Windpipe) The trachea is fairly rigid

because its walls are reinforced with C-shaped hyaline cartilage

These rings form two purposes:

1. Support the trachea and keep it open in spite of the pressure changes that occur during breathing

2. Allows it to expand anteriorly when we swallow a large piece of food

Heimlich ManeuverHeimlich 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 BronchiPrimary 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

LungsLungs 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)

LungsLungs

Each lung is divided into lobes by fissures

Left Lung - Has two lobes

Right Lung - Has three lobes

Coverings of the LungsCoverings 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.

LungsLungs

Coverings of the LungsCoverings 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 DivisionsRespiratory Tree Divisions

This branching and rebranching within the lungs is often referred to as the bronchial or respiratory tree:1. Primary bronchi

2. Secondary bronchi

3. Tertiary bronchi

4. Bronchioles

5. Terminal bronchioles

BronchiolesBronchioles

Bronchioles - Smallest branches of the bronchi

All but the smallest branches have reinforcing cartilage

BronchiolesBronchioles

Terminal bronchioles end in alveoli, or air sacs.

Respiratory ZoneRespiratory 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.

AlveoliAlveoli

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

AlveoliAlveoli

Structure of alveoli

Alveolar duct

Alveolar sac

Alveoli

Gas exchange takes place within the alveoli in the respiratory membrane

AlveoliAlveoli

Structure of alveoli

Alveolar duct

Alveolar sac

Alveoli

Gas exchange takes place within the alveoli in the respiratory membrane

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 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 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 ExchangeGas 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 ExchangeGas 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 Respiratory Membrane (Air-Blood Barrier)(Air-Blood Barrier)