Dr. Samar AskerDr. Samar Asker

It divided into Conducting portion & Respiratory portion

Conducting portion: no gaseous exchange but warm, humidify, clean entering air :1.Nasal cavities.2.Nasopharynx.3.Oroopharynx.4.Larynx.5.Trachea.6.Bronchi.7.Bronchioles.

Respiratory portion: gaseous exchange occurs.This portion includes:Respiratory bronchioles.& lung Alveoli. exchange of gases between the blood and the inspired air takes place.

TRACHEA11 length x 2 cm width.Starts at the end of the Larynx & end by dividing into 2 bronchiThe wall of the trachea consists of 4 layers: Mucosa, Submucosa , Fibro-Cartilagenous coatAdventitia.

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Mucosa

submucosa

Fibro-Cartilagenous coat

Adventitia

Mucosa:(A) Epithelium:Pseudo-stratified columnar ciliated with many goblet cells resting on clear but thin basement membrane

(B) The C.T. Corium: Thin infiltrated with lymphocytes & contain blood vessels & nerves .Rich in elastic fibres which condenses to form elastic membrane in the outer part.

L

Submucosa:-Loose areolar connective tissue contains muco serous tracheal glands which Open into the surface epithelium by short ducts.

Fibro-Cartilagenous coat:

16-20 C-shaped rings of hyaline cartilage embedded & connected CT that fuse with the perichondrium of the cartilage plates.The 2 ends of the cartilage plates are connected by transverse smooth muscle fibres & flattened posteriorly opposite the oesophagus(4) Adventitia: Formed of CT

THE LUNGThe main part of the respiratory portion of the respiratory tract & consist of air containing chamberscalled pulmonary or lung alveoli

PULMONARY ALVEOLIStructural & functional units of the lung. Minute air spaces that unit with each other & form air sacs.There are pores in () lung alveoli to allow communication.Separated from each other by thin inter alveolar septum.lined by two types of cells called pneumocytes type-1 & type-2..

Type-1- pneumocytes:The most numerous as they represent about 97% of the lining epithelium.L/M: - Flat squamous cells with flat deeply stained nucleus.

E/M:- little cytoplasm contains few organellsCells attached to each other by tight junctions to avoid escape of tissue fluids to alveoli .They can not divide.

Function: -Provide a very thin membrane through which gaseous exchange takes place.

Type-2- Pneumocytes:

Less numerous 3% of the alveolar lining cells.L/M: Cuboidal cells with vesicular rounded large nuclei

EM:Their apical surface have microvilli. Vacuolated cytoplasm rich in rER. Mitochondria, Golgi Complex.Can divide and give the 2 types of pneumocytes.

They have multilamellar bodies (cytosomes) contain phospholipids.

Function: Secrete pulmonary surfactant that forms a thin film over the epithelial lining which reduce the surface tension of lung alveoli & help their expantion.

N.B.: surfactant is only secreted late in pregnancy so premature babies usually have respiratory distress due to deficiency of surfactant.

Interalveolar septum

Part in() lung AlveoliHighly vascular C.T. rich inReticular fibres & elastic fibres which are important for elasticity & support of lung tissue.

Blood air barrier:Wall through which gas exchange occur. It is present in() blood in the capillaries & air within lung alveoli.

structure:1)Thin film of pulmonary surfactant2)cytoplasm of pneumocyte type I.3)The fused basement membrane of type I pneumocyte and capillary endothelium.4)capillary endothelium.

Alveolar phagocytes

phagocytic cells present in the cavities of lungs alveoli or the interalveolar septum.

Origin: blood monocytes

Staining : vital stain as trypan blue

Function : phagocytose bacteria & dust particles & rich in lysosomes.

Fate: coughed in the sputum or they may die & remain in the interalveolar septum or the near by lymph node.

Types: Dust cells:

phagocytosed dust or Carbon particles that are inspired with air & appear as black particles .them

Heart failure cells: Not in normal persons but in patient with heart failure. Congestion of blood capillaries will lead to their rupture & escape of RBCs to alveolar cavities. Macrophage phagocytose HB& destroy it to red colored hemosidrin granules that appear within them.

1)The conducting portion of the respiratory system includes :a)Trachea.b)Bronchi.c)Terminal bronchioles .d)Larynx. e)All of the above

 

In the trachea, the corium is separated from the submucosa by :a)A complete layer of smooth muscle fibers.b)A band of condensed fibro – elastic

membrane.c)A band of elastic fibro cartilage.d)A C- shaped ring of hyaline cartilage.e)Irregular plates of hyaline cartilage.

 

1)Concerning the alveolar epithelium, all are correct except:a)The epithelium rest on a very thick

basement membrane.b)Type-I- pneumocyte constitute the majority

(97%).c)Type II pneumocytes constitutes the

minority (3%).d)For gas exchange and secretion of

pulmonary surfactant.e)Type I pneumocytes are joined to

neighboring type II by tight junctions.

Regarding type –I pneumocyte, all are correct except :a)Constitute the majority of the alveolar

lining cells.b)Flat squamous cells.c)Can divide and give type II pneumocytes.d)For gaseous exchange.e)Joined to neighboring pneumocytes by

tight junction.

Each of the following is part of the blood air barrier except:a)Fused basement membrane of type I

pneumocyte and capillary endothelium.b)cytoplasm of pneumocyte type I.c)Thin film of pulmonary surfactantd)capillary endothelium.e)A network of reticular fibers and

elastic fibers.

Alveolar phagocytes

Type-1- pneumocytes:

Type-2- pneumocytes: