Histology and Pathology Flashcards
Name the functions of the respiratory system
- supplies oxygen to the blood for delivery to cells throughout the body
- removes carbon dioxide that has been accumulated in the blood from the tissues of the body
- phonation
- olfaction
- lungs function in blood pressure control via renin-angiotensin system
Describe the lining of the nasal cavity
- the initial part of the nasal cavity, the vestibule, is lined by keratinised stratified squamous epithelium
- deeper into the nasal cavity, the keratin is lost and deeper still it changes again to respiratory epithelium
What is respiratory epithelium?
Pseudostratified ciliated columnar epithelium with goblet cells
What is underneath the respiratory epithelium?
The lamina propria
What is the lamina propria?
A band of loose connective tissue containing seromucous glands and thin-walled venous sinuses which can quickly engorge with blood and block the nose
What is the oropharynx lined with?
Non-keratinised stratified squamous epithelium
Describe the lining of the epiglottis
- anterior surface is lined with squamous epithelium
- posterior surface transitions to respiratory epithelium
Describe the lining of the larynx
The walls are made up of cartilage and muscles with respiratory epithelium lining its surfaces with the exception of the vocal cords and adjacent structures
How many c shaped cartilages does the trachea have?
15 to 20
What is the open side of the ‘c’ shaped cartilage composed of?
Fibroelastic tissue and smooth muscle (trachealis muscle)
The rings of hyaline cartilage are replaced by what in the bronchi?
Irregularly shaped cartilage plates
The smallest bronchioles that lack respiratory function as referred to as what?
Terminal bronchioles
The smooth muscle of the bronchioles respond to what?
Parasympathetic innervation, histamine and other factors by contracting and constricting the diameter of the bronchiole
What are terminal bronchioles lined with?
Cuboidal ciliated epithelium and contain non-ciliated club cells that project above the level of adjacent ciliated cells
Name the functions of club cells
- stem cells
- detoxification
- immune modulation
- surfactant production
What is responsible for the spongy nature of the lungs?
The alveoli
Alveoli are lined with an epithelium which contain what?
Type 1 and type 2 alveolar cells (pneumocytes)
Describe type 1 alveolar cells
- simple squamous epithelium that lines the alveolar surfaces covering 90% of the alveolar surface
- these cells provide a barrier of minimal thickness that is permeable to gases
Describe type 2 alveolar cells
- polygonal in shape the free surface is covered by microvilli and the cytoplasm displays dense membrane bound lamellar bodies which contain surfactant
How is surfactant released?
Through exocytosis.
Define pneumonia
Infection involving the distal airspaces usually with inflammatory exudation, localised oedema. Fluid filled spaced lead to consolidation
How can pneumonia be classified?
- by location eg. hospital acquired or community acquired
- by organism eg. mycoplasma, pneumococcal etc
- by morphology eg. lobar pneumonia, bronchopneumonia
Describe lobar pneumonia
- confluent consolidation involving a complete lung lobe
- most often due to streptococcus pneumoniae
- can be seen with other organisms (klebsiella, legionella)
Describe the pathology of pneumonia
- a classical acute inflammatory response; exudation of fibrin-rich fluid, neutrophil infiltration, macrophage infiltration leading to resolution
- immune system play a part, antibodies lead to opsonisation, phagocytosis of bacteria
Name the complications of scarring
- organisation (fibrous scarring)
- abscess
- bronchiectasis
- empyema
Define bronchopneumonia
- infection starting in the airways and spreading to adjacent alveolar lung
- most often seen in the context of pre-existing disease, doesn’t develop as an epidemic
Name the organisms associated with bronchopneumonia
- strep. peumoniae
- haemophilus influenza
- staphylococcus
- anaerobes
- coliforms
Describe lung abscesses
- localised collection of pus, mass lesion
- tumour like
- chronic malaise and fever
- context- aspiration
Define bronchiectasis
- abnormal fixed dilation of the bronchi
- usually due to fibrosis scarring following infection (pneumonia, TB, cystic fibrosis)
- also seen with chronic obstruction
- cystic fibrosis in children- repeated bronchopneumonia’s leading to bronchiectasis
Describe immunity and hypersensitivity in relation to TB
- T cell response to organism enhances macrophage ability to kill mycobacteria, this ability constitutes immunity
- T cell response causes granulomatous inflammation., tissue necrosis and scarring, this is hypersensitivity (type 4)
- commonly both processes occur together
Why is the TB pathogen able to avoid phagocytosis?
Due to its waxy coat
Describe the tissues changes that occur in TB
- primary; small focus (ghon focus) in periphery of mid zon of lung
- large hilar nodes (granulomatous)
- secondary; fibrosing and cavitating apical lesion
Why does the TB pathogen reactivate?
- decreased T cell function; age, coincident disease (HIV), immuno-suppressive therapy (steroids, cancer chemotherapy)
- reinfection at high dose or with more virulent organism
Names some causes of interstitial lung disease
- environmental; minerals, drugs, radiations, post-ARDS, hypersensitivity
- unknown (idiopathic); connective tissue diseases, idiopathic pulmonary fibrosis
- diagnosis based on clinical features often with biopsy
What is the late stage of interstitial lung disease characterised by?
Fibrosis
Name some chronic interstitial disease
- idiopathic pulmonary fibrosis
- sarcoidosis
- hypersensitivity pneumonitis
- pneumoconiosis
- connective tissue diseases
Describe idiopathic pulmonary fibrosis
- aka cryptogenic fibrosing alveolitis, usual interstitial pneumonia
- progressive interstitial fibrosis of unknown cause
- variable associated inflammation
- finger clubbing `
Describe the pathology of idiopathic pulmonary fibrosis
- subpleural and basal fibrosis, affects peripheral areas of the lung
- inflammatory component variable
- terminal lung structure replaced by dilated spaces surrounded by fibrous walls
Describe hypersensitivity pneumonitis
- chronic inflammatory disease
- allergic origin
Describe the causes of hypersensitivity pneumonitis
- thermophilic bacteria; farmers lung
- avian proteins; bird fanciers lung
- fungi; malt workers lung
- precipitins (antibodies) often detectable in serum. Unusual cases come to biopsy
Describe sarcoidosis
- multisystem granulomatous disorder of unknown cause (defined by histological means)
- pulmonary involvement is common
- most cases mild and self-limiting
Name the other manifestations of sarcoidosis
- uveitis
- erythema nodosum
- lymphadenopathy
- hypercalcaemia
