1. The respiratory system I
Nasal cavity , sinuses, naso-pharynx
larynx

2. The respiratory system responsible for exchange of O 2 and CO 2 to and from the blood.
Respiratory organs include the lungs and a branching system of bronchial tubes that link the sites of gas exchange with the external environment.
Air is moved through the lungs by the help of: thoracic cage, intercostal muscles, diaphragm, and elastic components of the lung tissue.

3. The Respiratory system is divided:
Anatomically into structures of the upper and lower respiratory tracts.
Functionally, the system has two components:
■ The conducting portion.
■ The respiratory portion , where the system’s main function of gas exchange occurs.

5. The conducting portion consists of : 1. The nasal cavities, 2
The conducting portion consists of : 1. The nasal cavities, 2. Nasopharynx, 3. larynx, 4. Trachea, 5. Bronchi 6. Bronchioles, and terminal bronchioles

6. The conducting portion cleans and humidifies the inspired air and provides a conduit through which air moves to and from the lungs.
To ensure an uninterrupted supply of air, a combination of cartilage, elastic and collagen fibers, and smooth muscle provides the conducting portion with rigid structural support and the necessary flexibility and extensibility.

7. The respiratory portion : the main function is gas exchange and it is consist of :
Respiratory bronchioles.
Alveolar ducts.
Alveoli ( the cellular sites of the exchange of
O 2 and CO 2 between inspired air and blood) are saclike structures that make up most of the lungs.

8. The nasal cavity
The nasal cavity is divided into left and right side by the nasal septum.
The nasal cavity have two parts:
the external, dilated vestibule and
the internal nasal cavity

9. The vestibule
Skin of the nose enters the nares (nostrils) partway into the vestibule and has sweat glands, sebaceous glands, and coarse, moist vibrissae (hairs) that filter out particulate material from the inspired air.
Within the vestibule, the epithelium loses its keratinized nature and undergoes a transition to typical pseudostratified columnar epithelium before entering the nasal cavities.

10. The nasal cavity
The nasal cavities lie within the skull as two chambers separated by the osseous nasal septum .
Extending from each lateral wall are three bony shelf-like projections called conchae , or turbinates.
The mucosa covering these and other parts of the nasal cavity walls has a lamina propria with important roles in conditioning inhaled air.

12. The lamina propria
Contain a complex vasculature with loops of capillaries near the epithelial surface to warm inspired air.
Have small sero-mucous glands that humidify air by its watery secretions .
The thin layer of mucus produced by these glands and the goblet cells also serves to trap particulate and gaseous air impurities that are then removed.

13. Immunoglobulin A (IgA) from plasma cells in the lamina propria is also present in nasal secretions.

14. The epithelium
The middle and inferior conchae are covered with respiratory epithelium .
The roof of the nasal cavities and the superior conchae are covered with specialized olfactory epithelium .

16. Respiratory epithelium
Most of the nasal cavities and the respiratory system’s conducting portion is lined with ciliated pseudostratified columnar epithelium with goblet cells.
This epithelium has five major cell types, and contact a thick basement membrane:
1. Ciliated columnar cells are the most abundant.
2. Goblet cells are also numerous and predominate in some areas with basal nuclei and apical domains filled with granules of mucin and glycoproteins.
3. Brush cells are a much less numerous, is a columnar cell type with sparse, blunt microvilli on the apical surface. Brush cells act as chemosensory receptors.

17. 4. Small granule cells (or Kulchitsky cells) are difficult to distinguish in routine preparations, but possess numerous dense core granules. and are part of the diffuse neuroendocrine system.
5. Basal cells are mitotically active stem and progenitor cells that give rise to the other epithelial cell types.

18. Olfactory epithelium
The olfactory chemoreceptors for the sense of smell are located in the olfactory epithelium.
It is a specialized region of the mucous membrane covering the superior conchae at the roof of the nasal cavity.

22. The olfactory epithelium is a thick, pseudostratified columnar epithelium with three types of cells:
Olfactory neurons are :
Bipolar neurons present throughout this epithelium.
Their nuclei form an irregular row near the middle of this thick epithelium.

23. The apical (luminal) pole of each olfactory cell ( dendrite end ) has a knob-like swelling with about a dozen basal bodies.
From the basal bodies emerge long cilia with non-motile axon.
These receptors respond to odoriferous substances by generating an action potential along the axons extending from the basal ends of these neurons.
The axons leave the epithelium and unite in the lamina propria as very small nerves that then pass to the brain through foramina in the cribriform plate of the ethmoid bone .
There they form the olfactory nerve, cranial nerve I, and eventually synapse with other neurons in the olfactory bulb.

24. 2. Supporting cells are columnar, with broad, cylindrical apexes containing the nuclei and narrower bases. On their free surface are microvilli submerged in a fluid layer. Well-developed junctional complexes bind the supporting cells to the olfactory cells. They express abundant ion channels that help to maintain the microenvironment for olfactory function .

25. 3. Basal cells are small, spherical or cone-shaped cells near the basal lamina. These are the stem cells for the other two types, replacing the olfactory neurons every 2 to 3 months and support cells less frequently

26. The lamina propria of the olfactory epithelium possesses large serous glands, the olfactory glands (of Bowman), which produce a constant flow of fluid surrounding the olfactory cilia and facilitating the access of new odoriferous substances.

27. The loss or reduction of the ability to smell, anosmia or hyposmia, respectively, can be caused by traumatic damage to the ethmoid bone that severs olfactory nerve axons or by damage to the olfactory epithelium caused by intranasal drug use. The olfactory neurons are the best-known neurons to be replaced regularly because of regenerative activity of the epithelial stem cells from which they arise. For this reason, loss of the sense of smell due to toxic fumes or physical injury to the olfactory mucosa itself is usually temporary.

28. The paranasal sinuses
The paranasal sinuses are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull.
They are lined with a thinner respiratory epithelium with fewer goblet cells.
The lamina propria contains only a few small glands and is continuous with the underlying periosteum.

30. The paranasal sinuses communicate with the nasal cavities through small openings; mucus produced there is moved into the nasal passages by the activity of the ciliated epithelial cells.
Sinusitis is an inflammatory process of the sinuses that may persist for long periods of time, mainly because of obstruction of drainage orifices.

31. The Nasopharynx
The nasal cavities open posteriorly into the nasopharynx.
It is the first part of the pharynx and continuous caudally with the oropharynx ( the posterior part of the oral cavity) leading to the larynx.
The nasopharynx is lined with respiratory epithelium, and its mucosa contains the medial pharyngeal tonsil and the bilateral openings of the auditory tubes connected to each middle ear cavity.

32. The larynx
The larynx is a short (4 cm × 4 cm) passage for air between the pharynx and the trachea.
Its rigid wall is reinforced by hyaline cartilage
( in the thyroid, cricoid, and the inferior arytenoid cartilages) and smaller elastic cartilages (in the epiglottis, cuneiform, corniculate, and the superior arytenoid cartilages).

34. all are connected by ligaments.
Function:
Maintaining an open airway.
Movements of these cartilages by skeletal muscles participate in sound production during phonation.

35. The epiglottis
Is a flattened structure projecting from the upper rim of the larynx, serves to prevent swallowed food or fluid from entering that passage.
Its upper, or lingual, surface has stratified squamous epithelium.
at variable points on its laryngeal surface this epithelium undergoes a transition to ciliated pseudostratified columnar (respiratory) epithelium.
Mixed mucous and serous glands are found in the lamina propria beneath the epithelium.

37. Below the epiglottis the mucosa project into the lumen bilaterally with two pairs of folds separated by narrow space ( ventricle).
The upper pair is the unmovable vestibular folds; is covered with respiratory type of epithelium, and the lamina properia has numerous sero-mucous glands and occasional lymphoid nodules.

38. The vocal cords
The lower pair of folds has important features for phonation and sound production.
They are covered with stratified squamous epithelium that protects the mucosa from abrasion and desiccation from rapid air movement.
A dense regular bundle of elastic connective tissue, the vocal ligament, supports the free edge of each vocal fold.
Deep to the mucosa of each vocal fold are large bundles of striated fibers that comprise the vocalis muscle

39. Sound production
During phonation the vocalis muscles draw the paired vocal folds together (adduction), narrowing the intervening luminal space, the rima glottidis, and air expelled from the lungs causes the adducted vocal folds to vibrate and produce sound.
The pitch and other qualities of the sound are altered by changing the tension on the vocal folds, the width of the rima glottidis, the volume of air expelled.
The vestibular folds and ventricles, along with other structures and spaces higher in the respiratory tract, contribute to the resonance of sound produced in the larynx. Speech is produced when sounds made in the larynx are modified by movements of the pharynx, tongue, and lips. The larynx is larger in males than in females after puberty, causing men’s voices to be typically deeper than women’s voices.