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
