Respiratory SystemRespiratory System

Department of Histology Department of Histology

and Embryologyand Embryology

Respiratory SystemRespiratory System

Nasal cavityNasal cavity The pharynxThe pharynx The larynxThe larynx The trachea , bronchiThe trachea , bronchi The lungThe lung

Respiratory SystemRespiratory System

Conducting Conducting portionportion Respiratory portionRespiratory portion

Conducting portion

Nasal cavity, nasopharynx, larynx, trachea , bronchi, bronchioles and terminal bronchioles

Function:

Condition the inspired air(cleaned,moistened,

warmed)

Respiratory portionRespiratory portion

Respiratory bronchioles,alveolar duct, alveolar Respiratory bronchioles,alveolar duct, alveolar sac,and alveoli.sac,and alveoli.

Function:Gas exchangeFunction:Gas exchange

Key pointsKey points The structure of the tracheaThe structure of the trachea The composition and structure of The composition and structure of

respiratory portionrespiratory portion The function and structure of The function and structure of

alveolusalveolus

vestibular region

respiratory region

olfactory region

Nasal cavity

Ep:stratified squamous ep.(Vibrissae)

LP:sebaceous and sweat glandEp: pseudostratified ciliated columnar ep.

LP:vascular network

Ep:olfactory ep.

LP:serous gland(Bowman gland)

Olfactory cells

Supporting cells

Basal cells

TracheaTrachea

Structure:Structure:

MucosaMucosa: : SubmucosaSubmucosa AdventitiaAdventitia

EpitheliumEpithelium

Pseudostratified ciliated columnar epitheliumPseudostratified ciliated columnar epithelium with with much much thickerthicker basement membrane. basement membrane.

Ciliated cellCiliated cell Goblet cellGoblet cell Brush cellBrush cell Basal cellBasal cell ssmall granule cellmall granule cell

Ciliated cellCiliated cell

The most numerous of the tracheal cell types.They are The most numerous of the tracheal cell types.They are tall columner cells with cilia which project from the tall columner cells with cilia which project from the apical surface.apical surface.

The cilia provide a coordinate sweeping motion from thThe cilia provide a coordinate sweeping motion from the farthest reaches towards larynx. e farthest reaches towards larynx.

Goblet cellGoblet cell They are interspersed among the ciliated cells.They They are interspersed among the ciliated cells.They

can synthesize and secrete mucus.can synthesize and secrete mucus. The secretion covers the epithelium surface.The secretion covers the epithelium surface. Brush cellBrush cell: they are columnar cells that bear blu: they are columnar cells that bear blu

nt microvilli.nt microvilli.

Basal cellBasal cell: They serve as a reserve population that : They serve as a reserve population that maintains cell replacement in the epithelium.It is stem maintains cell replacement in the epithelium.It is stem cell. cell.

SSmall granule cellmall granule cell : They are difficult to distinguish : They are difficult to distinguish from basal cells in the light microscope.With the from basal cells in the light microscope.With the TEM,the cytoplasm cTEM,the cytoplasm contains many granules. ontains many granules.

SubmucosaSubmucosa

LCT containing LCT containing mixed glandsmixed glands.. Serous glands that keep the Serous glands that keep the epithelium moist;and epithelium moist;and

mucous glands that provide a covering in which dust mucous glands that provide a covering in which dust particles get caught.particles get caught.

The mucous is continuously moved towards the larynx The mucous is continuously moved towards the larynx by cilia action.by cilia action.

AdventitiaAdventitia

LCT containing "C" shaped LCT containing "C" shaped hyaline cartilagehyaline cartilage and and smooth musclessmooth muscles. .

Hyaline cartilageHyaline cartilage provides a supporting provides a supporting structure that prevent collapse of the tracheal structure that prevent collapse of the tracheal lumen during expiration.lumen during expiration.

The gaps between the cartilages ends are filled The gaps between the cartilages ends are filled in by smooth muscles.in by smooth muscles.

AsthmaAsthma

Asthma is a serious disease that Asthma is a serious disease that affects the lungs and the airways affects the lungs and the airways that deliver air to the lungs. that deliver air to the lungs.

Allergy is the leading cause of asthma. It Allergy is the leading cause of asthma. It causes periodic attacks of wheezing and causes periodic attacks of wheezing and difficult breathing. An asthma attack difficult breathing. An asthma attack occurs such as dust, pollen, pets, or cold occurs such as dust, pollen, pets, or cold weather.. The airways may become weather.. The airways may become blocked when the muscles surrounding the blocked when the muscles surrounding the lungs tighten. Or, mucus may narrow the lungs tighten. Or, mucus may narrow the airways in the lungs, making breathing airways in the lungs, making breathing even more difficult.even more difficult.

LungLung

•Parenchyma

Bronchial tree

Alveolus•Mesenchyme:CT

Changes of conduction portionChanges of conduction portion

The cartilages become irregular,and are The cartilages become irregular,and are progessively smaller. Cartilages is absenprogessively smaller. Cartilages is absent in the bronchioles.t in the bronchioles.

The amount of muscle in the bronchial The amount of muscle in the bronchial wall increase.wall increase.

Glands become fewer,and are absent in Glands become fewer,and are absent in the bronchioles.the bronchioles.

The epithelium become thiner.The epithelium become thiner.

Clara cellsClara cells

Terminal bronchiole lined by simple ciliated columTerminal bronchiole lined by simple ciliated columnar cells. Cells that are found among ciliated colnar cells. Cells that are found among ciliated columnar cells, are umnar cells, are non-ciliated non-ciliated and contain rich and contain rich sesecretory granules.cretory granules.

Function:Protection against harmful substance;Function:Protection against harmful substance;

Stem cell function. Stem cell function.

Respiratory portionRespiratory portion

Function: Capable of air exchange.Function: Capable of air exchange. Respiratory bronchioleRespiratory bronchiole: the wall is : the wall is

populated with more and more populated with more and more alveoli. alveoli.

Alveolar ductAlveolar duct:They have almost no :They have almost no walls,only alveoli,as their boundary.walls,only alveoli,as their boundary.

Alveolar sacAlveolar sac: They : They shared openingshared opening of several of several surrounding alveoli.surrounding alveoli.

AlveoliAlveoli: : Terminal blind ends Terminal blind ends of the track. The of the track. The main place where the air exchanges occur.main place where the air exchanges occur.

Respiratory bronchiole

Alveolar duct

Alveolar sac

Alveoli

AlveoliAlveoli

EpitheliumEpithelium type I cellstype I cells: : squamoussquamous, cover 95% of the alveolar su, cover 95% of the alveolar su

rface.rface. type II cells type II cells : Secrotory cells. contain : Secrotory cells. contain multilamellar bmultilamellar b

odiesodies, which are capable to release the , which are capable to release the surfactantsurfactant to to lower the lower the surface tensionsurface tension. . A surfactant is brieflA surfactant is briefly defined as a material that can greatly redy defined as a material that can greatly reduce the surface tension .uce the surface tension .

Can differentiate into Type I cells. Can differentiate into Type I cells.

Epithelium of AlveoliEpithelium of Alveoli

Type Ⅰalveolar cell

Type Ⅱalveolar cell

2. Alveolar septum2. Alveolar septum: Thin layer of LCT between adjacent : Thin layer of LCT between adjacent alveoli. alveoli.

Continuous Caps: The richest Cap network in the body. Continuous Caps: The richest Cap network in the body. Abundant elastic and reticular fibers: Function when Abundant elastic and reticular fibers: Function when

alveoli are enlarged. alveoli are enlarged. 3. Alveolar pores3. Alveolar pores: Windows between the adjacent : Windows between the adjacent

alveoli that can equalize the air pressure.alveoli that can equalize the air pressure. 4.Blood-air barrier4.Blood-air barrier

Elastic fiberElastic fiber

EmphysemaEmphysema

causes a loss of elasticity in the walls of causes a loss of elasticity in the walls of the small air sacs in your lungs. When the small air sacs in your lungs. When emphysema is advanced, you must work emphysema is advanced, you must work so hard to expel air from your lungs. so hard to expel air from your lungs. Unfortunately, because emphysema Unfortunately, because emphysema develops gradually over many years, you develops gradually over many years, you may not experience symptoms such as may not experience symptoms such as shortness of breath until irreversible shortness of breath until irreversible damage has already occurred. Treatments damage has already occurred. Treatments focus on relieving symptoms.focus on relieving symptoms.

4.Blood-air barrier4.Blood-air barrier

surfactant ,type I surfactant ,type I cells and basal cells and basal lamina, LCT, lamina, LCT, capillary capillary endothelium and endothelium and basal laminabasal lamina

Alveolar macrophagesAlveolar macrophages::

Review TestReview Test 1. Which of the following statements concerning ter1. Which of the following statements concerning ter

minal bronchioles is TRUE?minal bronchioles is TRUE? (A)(A) They are part of the conducting portion of the respiratory They are part of the conducting portion of the respiratory

systemsystem (B) They function in gas exchange(B) They function in gas exchange (C) They do not contain ciliated cells(C) They do not contain ciliated cells (D) They have cartilage plates present in their walls(D) They have cartilage plates present in their walls 2. Alveoli in alveolar sacs possess all of the followin2. Alveoli in alveolar sacs possess all of the followin

g components EXCEPT?g components EXCEPT? (A) elastic fibers in their walls(A) elastic fibers in their walls (B) a simple squamous lining epithelium(B) a simple squamous lining epithelium (C) reticular fibers in their walls(C) reticular fibers in their walls (D)(D) smooth muscle in their walls smooth muscle in their walls

HomeworkHomework

Describe the structure of the tracheaDescribe the structure of the trachea Compare the structure and Compare the structure and function of function of

olfactory epithelium with that of respiratory olfactory epithelium with that of respiratory epithelium.epithelium.

The composition of respiratory portion The composition of respiratory portion The The structure of the alveolistructure of the alveoli..