Histology Flashcards
Function of the upper respiratory tract
From nasal cavity to pharynx sometimes includes larynx
Warm air
Humidifies the air
Clear particulates
Function of lower respiratory tract
Trachea to alveoli and lungs sometimes includes larynx
Clear mucous
Allow elastic recoil
Allow gaseous exchange
Remain patent/open
The respiratory tract conducting and respiratory portion
Conducting portion: conduit, air conditioning system, nasal cavity> terminal bronchioles
Respiratory portion: involved in respiration, respiratory bronchioles> alveoli
Every tissue in conducting part of respiratory tract consists of the following tissue layers
Respiratory mucosa: epithelium and lamina propria (loose connective tissue)
Submucosa : vessels, serous and mucous glands, moisten the air
Cartilage and or muscle layer
Adventitia- fibrous connective tissue
Some cells/components change to allow specialisation
What type is the respiratory epithelium
Ciliated pseudostratified columnar epithelium
With goblet cells which stain clear, mucous production
Ciliated columnar cells
Basal cells- repair epithelium, type of stem cell
Mucociliary clearance
Goblet cells, ciliated columnar cells and serous and mucous glands= mucociliary escalator
Mucous traps particulates and cilia beat to move it to the pharynx for swallowing
Smokers produce more goblet cells so increased production mucous , increased goblet: ciliated cells ratio, decreased movement of mucous
Chronic coughing, infections, bronchitis
Nasal cavity
Has a large surface area produced by turbinate/ concha bones
Lots of serous glands in submucosa (stain dark purple) important in humidifying air
Highly vascularised- warm the air
Olfactory epithelium
Pseudostratified columnar no cilia no goblet cells
Sense of smell
Found over the superior concha
Made up of:
-bipolar olfactory neurones: olfactory hairs which are non mobile trap odors convert chemical stimuli into electrical stimuli synapses on olfactory tract
- basal cells which in this region responsible for regenerating bipolar olfactory neurones
-olfactory serous glands (glands of bowen)
Larynx histology
Mostly lined with the respiratory epithelium
Apart for over the true vocal folds and upper epiglottis there is STRATIFIED SQUAMOUS EPITHELIUM
These extra layers provide protection as air is turbulent can cause abrasion to these areas
Respiratory bronchiole epithelium
Simple cuboidal
Some ciliated cells
Basal cells
No goblet cells no mucous as it would block alveoli etc
They have bronchiolar exocrine club cells:
- non ciliated
-produce a component of surfactant
-are stem cells
-contain enzymes that detoxify noxious signals
- secrete antimicrobial factors and cytokines
- on apical surface
Alveoli walls
Formed from 3 components:
- surface epithelia, capillaries, supportive tissue
Thin specialised fixed basement membrane between alveoli and capillary endothelium
Thin walls= ideal for gaseous exchange at blood air interface
Alveoli epithelium= type 1 pneumocytes, linked by tight junction squamous cells
Alveolar septum= interstitial cells contain fibroblasts producing ECM fibres- reticular fibres, collagen, elastic fibres (allow expansion and recoil of alveoli), macrophages
Alveoli surface epithelium
Two types of pneumocytes:
- type 1 squamous cells with large cytoplasms cover most lining 97% however nuclei rarely seen
- type 2 more numerous but cuboidal so cover less area
Type 2 pneumocytes:
- produce surfactant, can differentiate into type 1 if there’s injury to alveoli, have lamellar bodies which produce lipid- component of surfactant
Air blood interface= 0.1-0.5 micrometers thickness interface
Alveoli macrophages
Macrophages/dust cells and other leukocytes migrate from capillaries within the alveoli to ingest any dust or pathogens to protect the airways
Increase in dust- industrial lung disease
What supporting tissues help to keep the conducting portion patent
Cartilage and smooth muscle (can also control diameter)
What supporting tissues help to keep the respiratory portion patent
Elastin- elastic recoil of lungs
Surfactant
Trachea
Submucosa contains 16-20 C shaped ring hyaline cartilage
Helps keep airways patent
Posteriorly connected by trachealis muscle- allows you to cough and expel the mucous
Lots mucous glands (clear stained) in submucosa
Respiratory epithelium
Bronchus
Cartilaginous plates
Smooth muscle immediate to the mucosa
Some glands in submucosa
Surrounded by alveolus/lung tissue
Moving from trachea to bronchus
Cartilage plates rather than c shaped rings
Fewer glands in submucosa
The lamina propria and submucosa are separated by layer of smooth muscle in bronchus
Fewer goblet cells, less mucous, blocks airways
Moving from bronchus to bronchioles
No cartilage
No glands
More elastin
Respiratory epithelium changes to simple cuboidal with club cells
No goblet cells
How might the histology of a bronchus change if repeatedly exposed to irritants
Damage to epithelium
Short term: more goblet cells so more mucous production reduced ability to clear, decreased clearance of pathogens> infections inflammation
Damage to cilia, cough
Long term changes- chronic bronchitis
Chronic bronchitis histology
Thickening bronchial wall
Chronic inflammation/ expose irritants
Immune infiltrate, hypertrophy of mucosal glands. Smooth muscles and respiratory epithelial cells
Emphysema histology
Destruction of walls of alveoli
Reduction in surface area for gas exchange
Loss of recoil in bronchioles> risk collapsing
Large white areas
Pneumonia histology
Bacteria proliferate within alveoli
Immune response fills alveoli with fluid MORE PINK
Prevents air in the alveoli, reducing gaseous exchange
Potentially fatal in MRSA
Pulmonary fibrosis histology
Fibroblasts proliferate within the alveolar walls
Deposit more ECM fibres
Thicken septum and barrier for gaseous exchange
Shortness of breath dyspnoea
More pink between alveoli
What are the main histological ways in which the airways are protected from pathogens
Mucocilary clearance
Intraepithelial immune cells in respiratory epithelium
Lymphoid tissue- diffuse and tonsils MALT- mucosal associated lymphoid tissue
Club cells secrete antimicrobial factors
Macrophages in alveoli and connective tissue
