1. 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.

2. Upper and Lower Respiratory Tracts
Upper Respiratory Tract
Lower Respiratory Tract

3. Organs of the Respiratory System
Nose
Pharynx
Larynx
______________
4. Trachea
5. Bronchi
6. Lungs—alveoli
Figure 13.1

4. Functions of the Respiratory System
1. 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.

5. 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

6. Upper Respiratory Tract
Figure 13.2

7. Anatomy of the Nasal Cavity
Olfactory receptors are located in the mucosa on the superior surface
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)

8. 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)

9. 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

10. Upper Respiratory Tract—Paranasal Sinuses
Figure 13.2

11. 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

12. Structures of the Pharynx
Tonsils of the pharynx
Pharyngeal tonsil (adenoids) are located in the nasopharynx
Palatine tonsils are located in the oropharynx
Lingual tonsils are found at the base of the tongue

13. 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.

14. 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)

15. Structures of the Larynx
Cricoid cartilage
the only complete ring of cartilage around the trachea
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,

16. Structures of the Larynx
Vocal folds (true vocal cords)
Vibrate with expelled air to create sound (speech)
Glottis—opening between vocal cords

17. 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.

18. Trachea (Windpipe)
Figure 13.3a

19. Trachea (Windpipe)
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.
Figure 13.3b

20. 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)

21. Main Bronchi
Figure 13.1

22. Main Bronchi
Figure 13.4b

23. 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

24. Lungs
Figure 13.4a

25. Lungs
Figure 13.4b

26. 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

27. Lungs
Figure 13.4a

28. 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

29. Bronchial (Respiratory) Tree Divisions
Figure 13.5a

30. Respiratory Zone Structures Site of gas exchange = alveoli only
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli (air sacs)
Site of gas exchange = alveoli only

31. Bronchial (Respiratory) Tree Divisions
Figure 13.5a

32. Bronchial (Respiratory) Tree Divisions
Figure 13.5b

33. 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.

34. Respiratory Membrane (Air-Blood Barrier)
Figure 13.6 (1 of 2)

35. Respiratory Membrane (Air-Blood Barrier)
On one side of the membrane is air and on the other side is blood flowing past
Figure 13.6 (2 of 2)

36. Gas Exchange Gas crosses the respiratory membrane by diffusion
Oxygen enters the blood
Carbon dioxide enters the alveoli

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

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