Respiratory System

21Jan08

GENERAL CHARACTERISTICS:

  • consist of paired lungs n air-conducting passages.
  • 3 main functions:
  • air-conditioning
  • air-conduction
  • gas exchange
  • air passages à conducting portion
    • respiratory portion
  • conducting portion:
    • nasal cavity
    • nasopharynx
    • larynx
    • trachea
    • bronchi <constitute the bronchial tree>
  • respiratory portion à <location for gas exchange. >
    • respiratory bronchioles
    • alveolar ducts
    • alveolar sacs
    • alveoli
  • blood vessels enter lung with bronchi.
  • arteries branch into smaller vessels as they follow the bronchiole tree into the substance of the lung.
  • capillaries à intimate contact with ALVEOLI <terminal respiratory unit>
  • intimate r/ship btw alveolar air spaces n the pulmonary capillaries is the structural basis for gas exchange within the lung parenchyma.
  • air passing thru the respiratory passages must be conditioned b4 reaching the terminal respiratory unit.
  • conditioning of the air include:
    • warming n cooling
    • moistening n drying
    • removal of particular material

NASAL CAVITY

  • each chamber is divided into 3 regions:
    • vestibule <nostril>
    • respiratory segment
    • olfactory segment


VESTIBULE

:

  • communicates with external environment.
  • lined with STRATIFIED, SQUAMOUS EPITHELIUM <outer – keratinized, inner – non-keratinized>
  • contain à hair <filter out the large particles>
    • sebaceous glands

RESPIRATORY SEGMENTS

  • Constitute most of the volume of NC
  • lined by CILIATED, PSEUDOSTRATIFIED COLUMNAR EPITHELIUM.
  • underlined lamina propria à attached to the periostium of adjacent wall à immobile!!
  • medial segment of RSà nasal septum <smooth!>
  • lateral wall à 3 shelf-like bone projection named CONCHAE à dual roles:
  • increase surface area
  • cause turbulence in air flow à allow more efficient condition of inspired air.
  • epithelium à 5 cell types:
  • ciliated cells
  • ¤ most numerous
  • ¤ luminal surface contains no. of cilia
  • ¤ cilia à provide coordinate sweeping motion of the mucous coat toward the environment.
  • ¤ F: removing of small perticles
  • Goblet/ mucous cells
  • ¤ = intestinal GC
  • ¤ F: produce mucous secretions
  • brush cells
  • ¤ specialized for transduction of general sensation.
  • ¤ sensory nerve endings terminate here.
  • small granule cells
  • ¤ endocrine cells
  • basal cells
  • ¤ stem cells from which other cell type Arise.
  • lamina propria à rich vascular network n mixed endocrine glands.

OLFACTORY SEGMENTS

  • upper part of each NC.
  • Lined with OLFACTORY MUCOSA à olfactory epith. N lamina propria with olfactory glands.
  • alofactory epit.
    • = epith. Of RS
    • PSEUDOSTRATIFIED but contains diff cell types.
    • Composed of:
  • OLFACTORY CELLS:
  • ¤ bipolar sensory neuron à act as chemoreceptors.
  • SUPPORTING CELLS
  • ¤ Columnar cells.
  • ¤ provide mechanical n metabolic support to the olfactory cells.
  • BRUSH CELLS
  • ¤ Same like in respiratory epithelium.
  • BASAL CELLS
  • ¤ stem cells from which new olfactory n supporting cells differentiate.

PHARYNX N LARYNX

  • PHARYNX à lined by mucosa with STRATIFIED SQUAMOUS EPITH.
  • its lamina propria contain diffused LYMPHATIC TISSUE N NODULES/FOLLICLES
  • LARYNX à Lined with mucosa
    • contain irregularly shaped plates of hyaline n elastic cartilages.
  • F of larynx à air-conducting
    • speech/ phonation
  • L contains à vocal cord n epiglottis à covered by STRATIFIED SQUAMOUS EPITHELIUM.
  • other parts of larynx à CILIATED, PSEUDOSTARTIFIED COLUMNAR EPITHELIUM!! à caharcterize the respiratory tract.
  • LAMINA PROPRIA of L à mixed MUCOUS-SEROUS GLANDS à SECRETE product onto the inner surface of L!

TRACHEA <T>

  • a tube, 2- 2 ½ cm in d.
  • ≈ 10cm long.
  • wall of trachea à 4 main layers:
  • mucous layer:
  • ¤ CILIATED, PSEUDOSTRATIFIED COLUMNAR EPITH.
  • ¤ elastic, fiber-riched lamina propria.
  • ¤ the T epith = R nasal epith.
  • submucosa layer
    • ¤ slightly denser CT than lamina propria.
    • ¤ contains mucous secreting glands called submucosal glands.
  • cartilaginous layer
    • ¤ C-shaped hyaline cartilages
    • ¤ ≈ 16-20 semi-rings.
  • adventitia
    • ¤ fibrous CT à binds the trachea to adjacent anatomical structures <eg: aorta, pericardium, etc.>

PULMONARY TISSUE

  • include à bronchiole tree
    • alveoli

BRONCHI

:

  • trachea divide into 2 branches à
    • primary or extra pulmonary
    • bronchi.
  • wall = trachea, BUT have RING-SHAPED CARTILAGE <in trachea C-shaped!!>
  • intrapulmonary bronchi à CARTILAGE PLATES n groups of submucosal glands from smaller bronchus. It also has muscular layer.
  • wall of bronchus à 5 layers:
  • mucosa layer
  • ¤ ciliated, pseudostratified columnar epithelium = trachea.
  • ¤ lamina propria = trachea BUT reduce in amount gradually.
  • muscular layer
    • ¤ smooth muscle cells
    • ¤ F: change the D of the airway.
  • submucosal layer
    • ¤ loose CT + mucous secreting glands.
  • cartilage layer
    • ¤ composed of discontinuous cartilage plates à reduced in sizes as the bronchiole D diminish.
  • adventitia layer
    • ¤ thin CT <irregular>
    • ¤ have blood vessels, nerve elements n adipose cells.

BRONCHIOLES

:

  • Divided into à terminal
    • alveolar /respiratory
  • wall: SIMPLE CUBOIDAL <sometimes columnar!> epithelium + loose CT with bundles of smooth muscle cells.
  • cartilage n glands à totally absent!! à differ from bronchus
  • epithelium à CILIATED CELLS + CLARA CELLS
  • CLARA CELLS à secrete surface-active agents <lipoproteins> à prevent luminal adhesion!
  • respiratory bronchioles differ from terminal bronchiole à presence of alveoli in their wall à take part in gas exchange!!
  • smallest functional unit of respiratory portion à respiratory bronchiolar unit; consist of a single R bronchiole , bifurcated alveolar ducts + sacs, n no. of alveoli.

ALVEOLI

  • terminal air spaces of the RS.
  • site of gas exchange.
  • alveolar epithelium <alveolocytes> à 3 cell types:
  • thin, squamous cells <PNEUMOCYTE TYPE I>
  • ¤ only nuclei-containing part is quite
  • thick.
  • ¤ F: gas exchange

PNEUMOCYTE TYPE II

  • ¤ SECRETORY CELLS.
  • ¤ secrete surface active agents à
    • SURFACTANT à prevent
    • luminal adhesion.

BRUSH CELLS

  • ¤ also present in the alveolar wall but
  • few in no.
  • within the alveolar septum à fibroblast, macrophages n leucocytes à disposed within the alveolar sacs.
  • intracellular matrix of the septum à no. of elastic fibers.
  • alveolar septum à air-blood barrier à 4 elements:
  • alveolar epithelial cells
  • basal lamina of alveolar epithelium
  • basal lamina of capillary endothelium.
  • capillary endothelium.




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