Histology of the Lungs Flashcards
What are the 2 parts of the respiratory system?
upper & lower respirtory tract
Describe the relationship between the lungs & ribs
- lungs reside within thoracic cavity
- pleural membranes facilitate decrease of friction
- visceral pleura lines external face of lungs
- parietal pleura lines inter thoracic side of ribcage
- space between membranes is called pleural cavity & is filled with pleural fluid
Describe Goblet cells
- secrete mucin (glycoprotiens & proteoglycans)
- well developed basal rough endoplasmic reticulum
- large secretory vesicles full of mucin at the cell
Describe epithelial specialisation in glands
- mucin secreting epithelial cells may aggregate together to form a gland
Describe the nasal cavity
- nasal turbinates project into airways
- complexity depends upon importance of olfaction
Describe the specialisation of olfactory epithelium
- contains a specialised type of neuronal cell called an olfactory receptor neuron
Describe the Olfactory Cells
- olfactory neurons possess elongated cilia, which protrude into nasal cavity
- cilia possess receptors which receive& respond to molecules inhaled by the nose
- receptors are from G protein coupled receptor
- mucus layer within nasal cavity provides a solute for inhaled substances to be solubilised
What will you see when looking at the olfactory epithelium ?
- olfactory cilia
- cilia
- olfactoruy fibres (axons)
- olfactory cell
- bowmans glands
What will you see when looking at the olfactory epithelium ?
- cilia
- goblet cells
- mucous glands
- serous cresents
How can tissues of the Respirtory tract be termed ?
either conducting or respiratory
^this greatly influences their histology
What are the principle roles of a conducting airway?
- transports & warms air from outside
- removes foreign particles by mucous entrapments & cilia action
Describe the Trachea
- approx 10cm long
- 2/3cm diameter
-20-30 incomplete circles of cartilage - gap is bridged by Trachealis muscle
- mucosa lined by Pseudostratified ciliated columnar epithelium
- epithelium contains scattered goblet cells
- sub epithelium contains seromucous glands
Describe the Structure of the Bronchi
- variable quantities of seromucous glands
- variable amounts of smooth muscle
- collaginous rings gradually fragment & diminish
- epithelium becomes less complex in smaller branches & columnar cells become shorter
- goblet cells gradually diminish
What cells make up the Bronchiolar Epithelium?
- ciliated cells
- basal cells
- intermediate cells
- goblet cells
- neuroendocrine cells
Define ciliated cells
- columnar at beginning then become cuboidal
- basal nucleus with numerous mito.
- 200 cilia each about 200 microns long
Define basal cells
- lie on basement membrane & are stem cells
Define intermediate cells
- intermediate in differentiation between 2 cell types
Define goblet cells
- found between ciliated cells & produce mucus
Define neuroendocrine cells
- small round cells
- dark staining nuclei on basement membrane
- secrete hormones & active peptides
Describe Bronchioles
- distal airways which lie between bronchi & where the ciliated epithelium ceases
- branch repeated & gradually reduce in size
- doesnt contain cartilage
- wall = rich in smooth muscle
- epithelium no longer pseudostratified
Describe Clara cells
- doesn’t have cilia & not mucous producing
- many large mito, abundant smooth ER & secretory granules
What are some functions of clara cells?
- metabolically active (P450 activity) = role in detoxification of inhaled substances
- surfactant production = helps to protect the bronchial epithelium
- stem cell properties = regenerates the ciliated bronchial epithelial cells if they become damaged
Describe Respiratory Airways
- commences after terminal bronchiole
- concerned with gaseous exchange
- composed of; respiratory bronchioles, alveolar ducts & sacs
Why are the alveolar ducts ill defined?
- have flattened epithelium surrounded by a spiral of smooth muscle
- largely composed of the openings to the alveoli
Describe the Alveoli
- main site of gaseous exchange
- 200-600 miliion in each normal lung
- provides surface area of 70-80m^2
- composed of an airsac with a thin wall which contains pulmonary capillaries
- adjacent alevoli are connected by pores of Kohn
Describe Alevolar type I cells (AT-I)
- 40% of alveolar cell population but cover 90% of alveoli surface
- very, very flat cells
- contains very few organelles
- have a very strong connection between their tight junctions
Describe Alevolar type II cells (AT-II)
- 60% of alveolar cell population but only covers 10% of the alveoli population
- cuboidal in shape
- thought to be the stem cell giving rise to AT-I cells
- rich in mito & have electron dense vesicles
- produces surfactant
Describe Alveolar Macrophages (dust cells)
- lie on top of the lining & are mobile
- can contain phagocytosed material
- they carry engulfed debris to the terminal bronchioles where they can be transported by the cilia to the trachea so they can be coughed out
