the respiratory system iii dr. mah jabeen muneera assistant professor department of anatomy kemu
TRANSCRIPT
THE RESPIRATORY SYSTEM III
Dr. Mah Jabeen MuneeraAssistant professor
Department of Anatomy
KEMU
RESPIRATORY BRONCHIOLE
Arise from terminal bronchiole
Diameter < 0.5mm
Transition between conducting &
respiratory subdivisions
Structurally similar to terminal
bronchioles EXCEPT
Walls interrupted by out
pocketings (alveoli)– gas exchange
Epithelium
Ciliated cuboidal in larger
Simple cuboidal in smaller
Lamina propria
Smooth muscles
Fibroelastic tissue
ALVEOLAR DUCT
Arise from respiratory
bronchioles
Completely lined by alveoli
Epithelium
Simple squamous
Smooth Muscles
Smooth muscles DISAPPEAR at
end of alveolar duct
Only elastic & collagen fibers
support the wall
ALVEOLAR SACS
Arise from alveolar duct
Epithelium
Simple squamous
Wall has:
Elastic fibers-for
expansion
Reticular fibers- to
prevent over distension
Capillaries embedded in
this CT
ALVEOLI
Sac like evaginations open on one
side
Size 200 µm
Between adjacent alveoli is
interalveolar septum
Elastic & reticular fibers Macrophages, fibroblast, mast cells
Continuous capillary bed (from pulmonary artery vein)
Air in alveoli separated from capillary
blood by respiratory membrane
made of
Alveolar cells
Fused basal lamina of alveolar cell &
capillary endothelium
Cytoplasm of endothelial cell
Jeanne Adiwinata Pawitan
Alveoli surrounded by fine elastic fibers Alveoli interconnect via alveolar pores of Kohn– equalize air
pressure, collateral ventilation Alveolar macrophages – free floating “dust cells”—Heart Failure
Cells Alveolar cells
Type I pneumocytes/alveolar cells - squamous alveolar cells) – tight junction – basal lamina – very thin region permeable to gasses
Type II pneumocytes/alveolar cells - great alveolar cell – septal cells – surfactant – surface tension decreased prevents collapse
Alveolar lining regeneration
This “Air-blood barrier” (the respiratory membrane) is where gas exchange occurs Oxygen diffuses from air in alveolus (singular of alveoli) to
blood in capillary
Carbon dioxide diffuses from the blood in the capillary into the air in the alveolus
Alveolar cells
Surfactant
Type II alveolar cells scattered in alveolar walls
Microvilli over free surface
Lamellar bodies
Phospholipids, surfactant proteins (A, B, C & D)
Surfactant is a detergent-like substance which is secreted in fluid coating alveolar surfaces – it decreases surface tension
Without it the walls would stick together during expiration
Respiratory Distress Syndrome
Premature babies – problem breathing is largely because they lack surfactant
Role of Steroids
Pleura
Pleural cavity – slit-like potential space filled with pleural fluid
Around each lung is a flattened sac of serous membrane called pleura
Parietal pleura Visceral pleura
Pleura
Mesothelial cells
Connective tissue
Pleural effusion - fluid
Haemothorax - blood
Pneumothorax - air
Pleuritis - infection
Clinical correlation
Asthma prolonged contraction – expiration
Lumen << – wheezing, dyspnea
Hypersecretion goblet cell, mucus/serous gl
Steroids, Β2-agonist -relax
Emphysema Longterm exposure- cigarette smoke ≈ inh
– antitrypsin >< elastase – dust cells – elastic fiber destructed
Fibrosis
Increased activity of fibroblasts in response to diseases causing distress
normal emphysema
Metaplasia
Tumors – squamous cell carcinoma
Clinical correlations
16
you might want to think twice about smoking….