dr. Susianti, M.Sc

GENERAL FEATURES OF THE RESPIRATORY SYSTEMThe respiratory system includes the lungs, airways (pharynx, larynx, trachea, bronchi) and associated structures.Specialized for gaseous exchange between blood and air, including the uptake of oxygen and release of carbon dioxide.

A. COMPONENTS OF RESPIRATORY SYSTEMFunctionally divisible into 3 major part: 1.Ventilating mechanismCreates pressure differences that move air into (inspiration) and out of (expiration) the lungs.Includes:diaphragm, rib cage, intercostal muscles, abdominal muscles lower the floor of the thorac cavity

2.Conducting PortionThe wall is specialized to carry air to and from the site of gas exchangeConditioning the air, warming, moistening, and cleaning it to enhance gas exchangeIncludes: nasal cavity, nasopharynx, larynx, trache, bronchi, bronchioles, terminal bronchioles

3.Respiratory portionDistinguished by alveoli:small, saccular structures, whose thin walls enable the gas exchange between air and blood.Bronchial tree: respiratory brochioles, alveolar ducts, and atrial and alveolar sacs

Structure of the Respiratory System

B. WALL STRUCTURE

Tube lining epithelium derives from endodermWall layers: epithelium, lamina propria, smooth muscles, adventitia Each layer undergoes gradual changes: nasal cavity alveoli

1.Respiratory epitheliumGeneral features: Most epithelium is ciliated pseudostratified collumnar with goblet cellsEpithelial cell types:Ciliated columnar cellMucous gobletBrush cellsSmall granule cells

2.Lamina PropriaLoose connective tissueSkeletal connective tissue, gradually decreases-disappears at the level of the bronchioles. 3.Smooth MuscleBegin in the trachea, joins the open ends of the tracheal cartilagesGradually decrease-disappears at the level of the alveolar ducts

NASAL CAVITYThe cavity is divided by the nasal septum into 2 bilaterally symmetric cavities, open through the nares (nostrils)Each cavity consists of:VestibuleNasal fossa

Nasal Mucosa

A. VESTIBULESmaller, wider, and more anterior chamber, lies behind naresMedial septum and lateral walls are supported by cartilage, and the epithelial lining is a continuation of the epidermis (sebaceous and sweat glands, thick short hairs called vibrissae) Deeper: nonkeratinized epithelium respiratory epithelium

B. NASAL FOSSALarger, narrower, and more posteriorSeptum and lateral walls are lined by respiratory epitheliumSupported by bone and contain mucous glands and venous sinuses in the lamina propriaThree curved bony shelves, termed conchae (turbinate bones)Venous plexuses (swell bodies)

Nasal Cavity

PARANASAL SINUSESThey are dilated cavities in the frontal, maxillary, ethmoid, and sphenoid bonesThin respiratory epithelial, has few goblet cellsLamina propria contains a few small mucous glands

NASOPHARYNXThe upper part of pharynxSingle cavity overlying the soft palateAnteriorly: nassal fossaeInferiorly: oral part of the pharynx (oropharynx)The wall lined by respiratory epithelium are supported by bone and skeletal muscle

LARYNXLies in the neckDuring swallowing, its opening is protected by epiglottisIts walls, supported by several laryngeal cartilages in the lamina propria, contain skeletal muscle and house the vocal apparatus

A. EPIGLOTTISThe flap of the tissue extends toward the oropharynx from the anterior border of the larynxSuperior surface: Nonkeratinized stratified squamous epitheliumInferior surface: Respiratory epitheliumLamina propria: A few mucous glands and small plate of elastic cartilage

B. LARYNGEAL CARTILAGESSeveral frame the laryngeal lumenThe larger: Thyroid, cricoid, and the most of the paired arytenoid cartilage are hyalineThe smaller: The paired of the cuneiform and corniculate, the epiglottic, and the tips of the arytenoids are elastic

C. VOCAL APPARATUSTwo bilaterally symmetric pairs of mucosal folds1.False vocal cords (Vestibular folds)The upper Covered by respiratory epithelium and contain serous glands2.True vocal cordsThe lowerCovered by stratified squamous epithelium 2 major structure: vocal ligament and vocalis muscle

TRACHEATube: 10 cm long, between larynx and primary bronchiLined by respiratory epitheliumLamina propria: mixed seromucous glandsCharacteristic: 16-20 C-shape cartilage rings Fibroelastic ligamentSmooth muscle bundle (trachealis muscle)

Trachea

BRONCHIAL TREETwo primary bronchi, entering each lungSimilar to the trachea, but cartilage rings and spiral bands of smooth muscle completely encircle their respective lumensRight primary bronchi: more vertical than that of the leftA. PRIMARY BRONCHI

Bronchus

Primary Bronchus

B. SECONDARY BRONCHILobar bronchiPrimary bronchus give rise:Right primary bronchus: 3 secondary bronchi Left primary bronchus: 2 secondary bronchiHistologic structure= primary bronchi, except that their supporting cartilages are arranged as irregular plates or islands

C. TERTIARY BRONCHISegmental bronchiSupplies one bronchopulmonary segment (pulmonary lobule)Histologic appearance is identical to that of secondary bronchiBranch several times to form smaller branches

Tertiary (Segmental) Bronchus

D. BRONCHIOLESBranches of the smallest bronchiLargest bronchioles differ from the smallest bronchi: absence of the cartilage and glands in their wallsLarge bronchioles:typical respiratory epitheliumFurther: epithelial height and complexity decrease to simple ciliated columnar or cuboidalEach bronchiole gives rise to 5-7 terminal bronchiole

Bronchiolus

E. TERMINAL BRONCHIOLESThe smallest components of the conducting portion Lined by ciliated cuboidal or columnar epithelium, have few or no goblet cellsLining also: dome-shaped cilia-free Clara cellsEach terminal bronchiole branches to form 2 or more respiratory bronchioles

F. RESPIRATORY BRONCHIOLESThe first part of respiratory portionLined by cuboidal epithelialInterrupted by thin-walled saccular evaginations called alveoliAs the alveoli increase in number, the cilia decrease untill they disappear. Goblet cells are absent

G. ALVEOLAR DUCTSThe distal extensions of the respiratory bronchiole where the alveoli are so denseThe alveolar duct can thus be likened to a long hallway with so many doorways leading to small rooms (alveoli) that the hallway (alveolar duct) appears almost to lack walls.

H. ATRIA AND ALVEOLAR SACSAtria: the distal termination of alveolarductsLong hallway (alveolar duct) leading to a rounded foyer (atrium). The foyer has small doorways leading to some small Rooms (alveoli), but has 2 or more larger doorways leading into short, dead-end hallways (alveolar sacs)

Terminal Portion of the Respiratory Tree

ALVEOLISpecialized for gas exchange, are critical to respiratory function.Consist of 2 simple squamous epithelial layers with the interstitium sandwiche between them, that consist of continous capillaries embedded in n elastic connective tissue

A. INTERALVEOLAR SEPTA

Gas exchange: Between the air in the alveolar lumen and the blood in the interstitial capillaries 1.Blood- air barrierStructure that oxygen and CO2 must exchanged0.1-0.5 m in thicknessIncludes: - Pulmonary surfactant - type I alveolar cells - Basal laminae??2.Alveolar PoresEach septum may be interrupted by one or more pores from 10-15 m in diameter

B. ALVEOLAR CELL TYPES1.Type I cellsCalled type I alveolar cells, type I pneumocytes,squamous alveolar cellsSquamous epithelial cells: 97% alveolar surfaceVery thin (25 nm) gas permeable components 2.Type II cellsCalled type II alveolar cells, type II pneumocytes, great alveolar cells, alveolar septal cellsAre roughly cuboidal with round nucleiLarge (0.2 m) membrane-limited lamellar bodiesSecretes pilmonary surfactant

3.Alveolar macrophagesCalled dust cellsMononuclear phagocyte system on the surface of the alveolar septa and in the intersitium

Alveoli

Three-dimensional schematic diagram of pulmonary alveoli showing the interalveolar septum and its structure. Observe the capillaries, connective tissue, and macrophages. These can also be seen in or passing into the alveolar lumens. Alveolar pores are numerous. Type II cells are identified by their abundant apical microvilli. The alveoli are lined by a continuous epithelial layer of Type I cells.

C. PULMONARY SURFACTANTContinously synthesized and secreted by type II alveolar cells onto the alveolar surface2 Function:Reduce surface tension in the alveoliHave some bactericidal effects 2 layer:Aqueous basal layer (hypophase)Monomolecular fill of phospholipid (dipalmitoyl lecithin)

PULMONARY CIRCULATIONA. BLOOD SUPPLY1.Functional circulationPulmonary arteriesPulmonary veins2.Systemic circulation Bronchial arteriesBronchial veins

B. LYMPHATIC DRAINAGEDivided into superficial and deep networksVessels of the superficial network which have many valves, are found in the visceral pleuraLymphatic vessels are notably absent from interalveolar septa

INNERVATIONAutonomic motor and general sensory nerves penetrate the pulmonary rootSensory nerves: localized pain sensations, monitor irritants in the airway and are involved in the cough reflexParasymphatic motor fibers (branches of vagus nerve ) stimulate bronchial constriction, symphatic: bronchial dilation

PLEURASerous membrane2 layers:Covering the lungs (visceral pleura)Covering the internal wall of the thoracic cavity (parietal pleura)Consist of thin squamous mesothelium, thin layer of connective tissuePleural cavity: between visceral and parietal pleura, contain lubricating fluid

Visceral Pleura