Respiratory System

Objectives:

Functional Anatomy of the Respiratory System• Name the organs forming the respiratory passageway from the nasal cavity to the alveoli of the lungs (or identify them on a diagram or model) and describe the function of each.•Describe several protective mechanisms of the respiratory system.•Describe the structure and function of the lungs and the pleural coverings.

Upper and Lower Respiratory Tracts

Upper Respiratory Tract

Lower Respiratory Tract

Organs of the Respiratory System

Figure 13.1

1. Nose

2. Pharynx

3. Larynx

______________

4. Trachea

5. Bronchi

6. Lungs—alveoli

Functions of the Respiratory System1. Passageways to the lungs (nose, pharynx, larynx, trachea, bronchi) purify, humidify, and warm the incoming air.

•The conducting zone of the respiratory system is made up of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles

2. Gas exchanges between the blood and external environment only occurs in the alveoli of the lungs

•The respiratory zone of the respiratory system is made up of the respiratory bronchioles, alveolar ducts, and the alveoli.

1. The Nose• Only externally visible part of the respiratory system• Air enters the nose through the external nostrils (nares)• Interior of the nose consists of a nasal cavity divided by a

nasal septum

nasal septum

Upper Respiratory Tract

Figure 13.2

Anatomy of the Nasal Cavity

• The rest of the cavity is lined with respiratory mucosa resting on thin-walled veins that• Warm the incoming air• Mucus produced by mucous glands moisten air & traps incoming

foreign particles• Ciliated cells of the mucosa move the sheet of contaminated

mucus away from the lungs and toward the throat for swallowing(The oral mucosa does not of these functions)

Olfactory receptors are located in the mucosa on the superior surface

Anatomy of the Nasal Cavity• Lateral walls have projections

called conchae• Increase surface area• Increase air turbulence within the

nasal cavity

• The nasal cavity is separated from the oral cavity by the palate• Anterior hard palate (bone)• Posterior soft palate (muscle)

Paranasal Sinuses• Cavities within bones surrounding the nasal cavity are

called sinuses• Sinuses are located in the following bones

• Frontal bone• Sphenoid bone• Ethmoid bone• Maxillary bone

Function of the sinuses•Lighten the skull•Act as resonance chambers for speech•Produce mucus that drains into the nasal cavity

Upper Respiratory Tract—Paranasal Sinuses

Figure 13.2

2. Pharynx (Throat)• Muscular passage from

nasal cavity to larynx• 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

Structures of the Pharynx• Tonsils of the pharynx

1. Pharyngeal tonsil (adenoids) are located in the nasopharynx

2. Palatine tonsils are located in the oropharynx

3. Lingual tonsils are found at the base of the tongue

Structures of the Pharynx• Pharyngotympanic tubes open into the nasopharynx

If either the middle ear or the sinuses are infected, the exudate will drain into the nasal passages and possibly lead to congestion, or “postnasal drip.” Conversely, a nasopharyngeal infection can easily spread to the middle ear cavity or the sinuses because of the continuity of their mucosae, thus causing otitis media or sinusitis, respectively.

3. Larynx (Voice Box)• Routes air and food into proper channels• Plays a role in speech• Made of eight rigid hyaline cartilages and a spoon-shaped

flap of elastic cartilage (epiglottis)

Structures of the Larynx• Thyroid cartilage

• Largest of the hyaline cartilages• Protrudes anteriorly (Adam’s apple)

• Epiglottis• Protects the 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

Normal larynx as seen during larynx examination or laryngoscopy:

1=vocal cords, 2=vestibular fold(false vocal cords), 3=epiglottis,

http://www.getbodysmart.com/ap/respiratorysystem/larynx/thyroid_cricoid/tutorial.html

• Cricoid cartilage• the only complete ring of cartilage

around the trachea

http://www.youtube.com/watch?v=QvGYvK6qScE&feature=related

Structures of the Larynx• Vocal folds (true vocal cords)

• Vibrate with expelled air to create sound (speech)

• Glottis—opening between vocal cords

http://www.youtube.com/watch?v=qpt0kigakWY&feature=related

4. Trachea (Windpipe)

• Four-inch-long tube that connects larynx with bronchi• Lined with ciliated mucosa

• Beat continuously in the opposite direction of incoming air• Expel mucus loaded with dust and other debris away from

lungs

Mucus serves to trap dust, bacteria, and other foreign debris that manage to enter the respiratory passageways.

Trachea (Windpipe)

Figure 13.3a

Trachea (Windpipe)

Figure 13.3b

Walls are reinforced with C-shaped hyaline cartilage

The cartilaginous reinforcements keep the trachea open during the pressure changes that occur during breathing. The incomplete rings of the posterior tracheal surface make it flexible, allowing a food bolus traveling through the posterior esophagus to bulge anteriorly.

5. Main (Primary) Bronchi• Formed by division of the trachea• Enters the lung at the hilum (medial depression)• Right bronchus is wider, shorter, and straighter than left

(most likely site for an inhaled object to become lodged)• Bronchi subdivide into smaller and smaller branches (23

times)

Main Bronchi

Figure 13.1

Main Bronchi

Figure 13.4b

6. Lungs• Occupy most of the thoracic cavity

• Heart occupies central portion called mediastinum

• Apex is near the clavicle (superior portion)• Base rests on the diaphragm (inferior portion)• Each lung is divided into lobes by fissures

• Left lung—two lobes• Right lung—three lobes

The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape

Lungs

Figure 13.4a

Lungs

Figure 13.4b

Coverings of the Lungs• Serosa covers the outer surface 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

• These two pleural layers resist being pulled apart

Lungs

Figure 13.4a

Bronchial (Respiratory) Tree Divisions

• All but the smallest of these passageways have reinforcing cartilage in their walls• Primary bronchi• Secondary bronchi• Tertiary bronchi• Bronchioles• Terminal bronchioles

Bronchial (Respiratory) Tree Divisions

Figure 13.5a

Respiratory Zone

• Structures1. Respiratory bronchioles

2. Alveolar ducts

3. Alveolar sacs

4. Alveoli (air sacs)

• Site of gas exchange = alveoli only

Bronchial (Respiratory) Tree Divisions

Figure 13.5a

Bronchial (Respiratory) Tree Divisions

Figure 13.5b

Respiratory Membrane (Air-Blood Barrier)• Thin squamous epithelial layer lines alveolar walls• Alveolar pores connect neighboring air sacs• Pulmonary capillaries cover external surfaces of alveoli

ALVEOLI walls are extremely thin (one layer of squamous epithelium plus a basement membrane) for easy gas exchange, and combined, they present an extremely large surface area.

Respiratory Membrane (Air-Blood Barrier)

Figure 13.6 (1 of 2)

Respiratory Membrane (Air-Blood Barrier)

Figure 13.6 (2 of 2)

On one side of the membrane is air and on the other side is blood flowing past

Gas Exchange• Gas crosses the respiratory

membrane by diffusion• Oxygen enters the blood• Carbon dioxide enters the alveoli

Alveolar Macrophages

Alveolar macrophages (“dust cells”) add protection by picking up bacteria, carbon particles, and other debris

Surfacant• In order to function properly, the alveoli must always

stay moist. Special cells in the alveoli secrete a substance called a surfactant which reduces the surface tension of water, thereby enabling it to better coat the cells of the alveoli to keep them moist and keep them from sticking to each other when the person exhales.

• The ability to secrete this chemical doesn’t develop until around the eighth or ninth month of pregnancy, so there frequently is a problem in premature babies with the lack of surfactant causing the alveoli to stick together when the baby exhales. Then, when the baby inhales again, the stuck alveolar cells tear away from their neighbors. Scar tissue forms at these sites, thus the damage is permanent, and the person’s lungs lose some of their elasticity and ability to expand fully.

• A current “hot” area of research is searching for a suitable replacement surfactant that could be placed into the lungs of premature babies to prevent this damage.

Surfactant (a lipid molecule) coats gas-exposed alveolar surfaces