Respiratory system. Anatomical & Functional subdivisions. By Dr. Suhail Ahmad.

The Respiratory System

Organization and Functions of the Respiratory System Structural classifications: – upper respiratory tract – lower respiratory tract.

Upper Respiratory Tract Composed of – the nose – the nasal cavity – the paranasal sinuses – the pharynx (throat) – and associated structures. All part of the conducting portion of the respiratory system.

Lower Respiratory Tract Conducting portion – Larynx – Trachea – Bronchi – bronchioles and their associated structures Respiratory portion of the respiratory system – respiratory bronchioles – alveolar ducts – alveoli

Organization of the Respiratory System Functional classifications: – Conducting portion: transports air. Nose nasal cavity Pharynx Larynx Trachea progressively smaller airways, from the primary bronchi to the bronchioles

Organization of the Respiratory System Functional classifications: continued – Conducting portion: transports air. – Respiratory portion: carries out gas exchange. respiratory bronchioles alveolar ducts air sacs called alveoli Upper respiratory tract is all conducting Lower respiratory tract has both conducting and respiratory portions

The Respiratory Organs Conducting zone – Respiratory passages that carry air to the site of gas exchange – Filters, humidifies and warms air Respiratory zone – Site of gas exchange – Composed of Respiratory bronchioles Alveolar ducts Alveolar sacs Conducting zone labeled

Respiratory System Functions Breathing (pulmonary ventilation): – consists of two cyclic phases: inhalation, also called inspiration exhalation, also called expiration – Inhalation draws gases into the lungs. – Exhalation forces gases out of the lungs. Gas exchange: O 2 and CO 2 – External respiration External environment and blood – Internal respiration Blood and cells

Respiratory System Functions Gas conditioning: – Warmed – Humidified – Cleaned of particulates Sound production: – Movement of air over true vocal cords – Also involves nose, paranasal sinuses, teeth, lips and tongue Olfaction: – Olfactory epithelium over superior nasal conchae Defense: – Course hairs, mucus, lymphoid tissue

Nose Provides airway Moistens and warms air Filters air Resonating chamber for speech Olfactory receptors External nose

Skeletal framework Bones that contribute to the skeletal framework of the nasal cavities include: The unpaired – Ethmoid – Sphenoid, – Frontal bone – Vomer The paired – Nasal – Maxillary – Palatine – Lacrimal Bones – Inferior Conchae

Regions Each nasal cavity consists of three general regions. The nasal vestibule is a small dilated space just internal to the naris that is lined by skin and contains hair follicles; The respiratory region is the largest part of the nasal cavity, has a rich neurovascular supply, and is lined by respiratory epithelium composed mainly of ciliated and mucous cells; The olfactory region is small, is at the apex of each nasal cavity, is lined by olfactory epithelium, and contains the olfactory receptors

Lateral wall The lateral wall is characterized by three curved shelves of bone (conchae) – which are one above the other and – project medially and inferiorly across the nasal cavity. The medial, anterior and posterior margins of the conchae are free.

The conchae divide each nasal cavity into four air channels: an inferior nasal meatus between the inferior concha and the nasal floor; a middle nasal meatus between the inferior and middle concha; a superior nasal meatus between the middle and superior concha; and a spheno-ethmoidal recess between the superior concha and the nasal roof.

These conchae increase the surface area of the lateral wall. The openings of the paranasal sinuses are on the lateral wall and roof of the nasal cavities. The lateral wall also contains the opening of the nasolacrimal duct, which drains tears from the eye into the nasal cavity.

Medial wall The medial wall of each nasal cavity is the mucosa-covered surface of the thin nasal septum Oriented vertically in the median sagittal plane Separates the right and left nasal cavities from each other.

Medial wall The nasal septum consists of: – the septal nasal cartilage anteriorly – posteriorly, mainly the vomer and the perpendicular plate of the ethmoid bone

Nasal septum(medial wall).

Blood supply The nasal cavities have a rich vascular supply for altering the humidity and temperature of respired air. vessels that originate from branches of the external carotid artery include: – sphenopalatine – greater palatine – superior labial – lateral nasal arteries vessels that originate from branches of the internal carotid artery are: – anterior ethmoidal – posterior ethmoidal

Blood supply

Innervation Innervation of the nasal cavities is by three cranial nerves. olfaction is carried by the olfactory nerve [I]; General sensation is carried by the trigeminal nerve [V], the anterior region by the ophthalmic nerve [V 1 ], and the posterior region by the maxillary nerve [V 2 ]; All glands are innervated by parasympathetic fibers in the facial nerve [VII] (greater petrosal nerve), which joins branches of the maxillary nerve [V 2 ] in the pterygopalatine ganglion.

Innervation

Lymphatic drainage.

Paranasal Sinuses Paranasal sinuses: – In four skull bones – paired air spaces – decrease skull bone weight Named for the bones in which they are housed. – frontal – ethmoidal – sphenoidal – maxillary Communicate with the nasal cavity by ducts. Covered with the same pseudostratified ciliated columnar epithelium as the nasal cavity.

Paranasal Sinuses

Paranasal sinuses – Can get infected: sinusitis

Paranasal Sinuses

PHARYNX The pharynx is a musculo-fascial tube behind the nasal and oral cavities. Funnel-shaped – slightly wider superiorly and narrower inferiorly. Its anterior wall is largely deficient and through this defect it communicates with the: – Nasal cavities – Oral cavity – Larynx The pharyngeal cavity is a common pathway for air and 'food'.

PHARYNX The pharynx is attached above to the base of the skull. It is continuous below with esophagus in the neck.

PHARYNX Based on the anterior relationships the pharynx is subdivided into three regions: – nasopharynx – oropharynx – laryngopharynx The posterior apertures (choanae) of the nasal cavities open into the nasopharynx; The posterior opening of the oral cavity (oropharyngeal isthmus) opens into the oropharynx; The superior aperture of the larynx (laryngeal inlet) opens into the laryngopharynx.

Pharynx Walls: – lined by a mucosa – contain skeletal muscles primarily used for swallowing. Flexible lateral walls – distensible – to force swallowed food into the esophagus.

Larynx Short, somewhat cylindrical airway Location: – bounded posteriorly by the laryngopharynx, – inferiorly by the trachea. Prevents swallowed materials from entering the lower respiratory tract. Conducts air into the lower respiratory tract. Produces sounds.

Larynx Nine pieces of cartilage – three individual pieces Thyroid cartilage Cricoid cartilage Epiglottis – three cartilage pairs Arytenoids: on cricoid Corniculates: attach to arytenoids Cuniforms:in aryepiglottic fold

Nine pieces of cartilage – held in place by ligaments and muscles. Intrinsic muscles: regulate tension on true vocal cords Extrinsic muscles: stabilize the larynx

Framework of the larynx – 9 cartilages connected by membranes and ligaments – Thyroid cartilage with laryngeal prominence (Adam’s apple) anteriorly – Cricoid cartilage inferior to thyroid cartilage: the only complete ring of cartilage: signet shaped and wide posteriorly

– Behind thyroid cartilage and above cricoid: 3 pairs of small cartilages 1.Arytenoid: anchor the vocal cords 2.Corniculate 3.Cuneiform – 9 th cartilage: epiglottis

Trachea A flexible, slightly rigid tubular organ – often referred to as the “windpipe.” Extends through the mediastinum – immediately anterior to the esophagus – inferior to the larynx – superior to the primary bronchi of the lungs.

Trachea Anterior and lateral walls of the trachea are supported by 15 to 20 C-shaped tracheal cartilages. – cartilage rings reinforce and provide some rigidity to the tracheal wall to ensure that the trachea remains open (patent) at all times – cartilage rings are connected by elastic sheets called anular ligaments

Trachea At the level of the sternal angle(T-4), the trachea bifurcates into two smaller tubes, called the right and left primary bronchi. Each primary bronchus projects laterally toward each lung. The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina.

53 Carina* Ridge on internal aspect of last tracheal cartilage Point where trachea branches (when alive and standing is at T7) Mucosa highly sensitive to irritants: cough reflex *

Bronchial Tree A highly branched system – air-conducting passages – originate from the left and right primary bronchi. Progressively branch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles.

Primary bronchi – Incomplete rings of hyaline cartilage ensure that they remain open. – Right primary bronchus shorter, wider, and more vertically oriented than the left primary bronchus. – Foreign particles are more likely to lodge in the right primary bronchus.

Bronchial Tree Primary bronchi – enter the hilum of each lung Secondary bronchi (or lobar bronchi) – Branch of primary bronchus – left lung: two lobes two secondary bronchi – right lung three lobes three secondary bronchi.

Tertiary bronchi (or segmental bronchi) – Branch of secondary bronchi – left lung is supplied by 8 to 10 tertiary bronchi. – right lung is supplied by 10 tertiary bronchi – supply a part of the lung called a bronchopulmonary segment.

Respiratory Bronchioles, Alveolar Ducts, and Alveoli Contain small saccular outpocketings called alveoli. An alveolus is about 0.25 to 0.5 millimeter in diameter. Its thin wall is specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries. The spongy nature of the lung is due to the packing of millions of alveoli together.

Respiratory Bronchioles, Alveolar Ducts, and Alveoli Gas exchange can take place in the respiratory bronchioles and alveolar ducts as well as in the lungs, which contain approximately 300– 400 million alveoli.

Pleura and Pleural Cavities The outer surface of each lung is tightly covered by the visceral pleura Internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura. The parietal and visceral pleural layers are continuous at the hilum of each lung.

Pleura and Pleural Cavities The potential space between these serous membrane layers is a pleural cavity. The pleural membranes produce a thin, serous fluid that circulates in the pleural cavity and acts as a lubricant, ensuring minimal friction during breathing.

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68 CXR (chest x-ray)

Chest x rays Normal female Lateral (male)

Pneumothorax

There are many diseases of the respiratory system, including asthma, cystic fibrosis, COPD (chronic obstructive pulmonary disease – with chronic bronchitis and/or emphysema) and epiglottitis example: normalemphysema

72 you might want to think twice about smoking….