The respiratory system I

Functional Anatomy

Respiratory Stems• The organs of the

respiratory system include the nose, pharynx, trachea, bronchi and their smaller branches, and the lungs, which contain the alveoli or terminal air sacs

• Consists of an upper respiratory tract (nose to larynx) and a lower respiratory tract ( trachea onwards) .

Conducting ZoneConducting zone– Respiratory passages that

carry air to the site of gas exchange

– Filters, humidifies and warms air

– includes the nose, nasal cavity, pharynx, larynx, trachea, and progressively smaller airways, from the primary bronchi to the terminal bronchioles

Respiratory Zone

Respiratory zone–Site of gas exchange–Composed of•Respiratory

bronchioles•Alveolar ducts•Alveolar sacs

The Nose• It is the only externally visible part of the

respiratory system• During breathing, air enters the nose by

passing through the external nares, or nostrils• The interior of the nose consists of the nasal

cavity, divided by a midline nasal septum

The Nose• The olfactory receptors for

the sense of smell are located in the mucosa in the slit like superior part of the nasal cavity, just beneath the ethmoid bone

• The rest of the mucosa lining the nasal cavity called respiratory mucosa, rests on a rich network of thin-walled veins which warms the air as it flows past

Mucosa lining function

• Moistens the air and traps incoming bacteria and other foreign debris

• The ciliated cells of the nasal mucosa (Cillia) create a gentle current that moves contaminated mucus posteriorly towards the throat, where it is swallowed and digested by stomach juices

Conchae• The lateral walls of the nasal

cavity are uneven owing to the 3 mucosa covered projections or lobes called conchae

• This greatly increases the surface area of the mucosa exposed to air

• It also increases the air turbulence in the nasal cavity, prevent particles from reaching the lungs

Palate

• The nasal cavity is separated from the oral cavity below by a partition, the palate

• Anteriorly, where the palate is supported by bone, is the hard palate

• The unsupported posterior part is the soft palate

Paranasal sinuses

• It is located in the frontal, sphenoid, ethmoid and maxillary bones

• They produce mucus, which drains into the nasal cavities

Pharynx

• It is a muscular passageway about 13 cm long

• Commonly called the throat, the pharynx serves as a common passageway for food and air

Pharynx

• Air enters the superior portion, the nasopharynx, from the nasal cavity anteriorly and then descends through the oropharynx and laryngopharynx to enter the larynx below

Tonsils• Clusters of lymphatic tissue

called tonsils are also found in the pharynx:

- The pharyngeal tonsils, often called adenoids, are located high in the nasopharynx

- The palatine tonsils are in the oropharynx at the end of the soft palate

- The lingual tonsils are at the base of the tongue

Larynx

• The larynx, or voice box, routes air and food into the proper channels and plays a role in speech

• Located inferior to the pharynx, it is formed by 8 rigid hyaline cartilages and a spoon shaped flap of elastic cartilage, the epiglottis

Epiglottis• The epiglottis protects the

superior opening of the larynx- When we are not swallowing,

the epiglottis does not restrict the passage of air into the lower respiratory passaged

- When we swallow food or fluids, the larynx is pulled upward and the epiglottis tips, forming a lid over the opening of the larynx

Vocal Cords

• Part of the mucous membrane of the larynx forms a pair of folds, called the vocal folds, or true vocal cords, which vibrate with expelled air

Trachea

• Air entering the trachea, or windpipe from the larynx travels down its length to the level of the fifth thoracic vertebra, which is approximately mid-chest

• The trachea is lined with ciliated mucosa: they propel mucus away from the lungs to the throat where it can be swallowed or spat out

Primary Bronchi

• The right and left primary bronchi are formed by the division of the trachea

• The right primary bronchus, which is wider, shorter, and straighter than the left, is the more common site for an inhaled foreign object to become lodged

Lungs

• The paired lungs are fairly large organs

• The narrow superior portion of each lung, the apex, is located just deep to the clavicle

• The broad lung area resting on the diaphragm is the base

• Each lung is divided into lobes, the left lung has two lobes and the right lung has three

Lungs• The surface of each lung is covered with a

visceral membrane called the pulmonary pleura, and the wall of the thoracic cavity are lined by the parietal pleura

• The parietal pleura produces a slippery secretion, plural fluid, which allows the lungs to glide easily over the thorax wall during breathing

Bronchioles

• After the primary bronchi enter the lungs, they subdivide into smaller and smaller branches, finally ending in the smallest of the conducting passageways, the bronchioles

Alveoli

• It is the only site of gas exchange

• There are millions of the clustered alveoli, which resemble bunches of grapes, and they make you the bulk of the lungs

The respiratory Membrane• The walls of the alveoli are composed largely of a single, thin layer of

squamous epithelial cells• The external surfaces of the alveoli are covered with a web of pulmonary

capillaries• The gas exchanges occur by simple diffusion through the respiratory

membrane