Histology of the Respiratory System Flashcards
What are the two main processes in respiration?
physical process- ventilation which involves inspiratory and expiratory movement of chest wall
chemical process- exchange of gases between air and blood takes place at the cellular level
What are the two portions that the respiratory system can be divided into?
conducting portion- no gaseous exchange takes place here with the bloodstream
(includes nose, pharynx, larynx, trachea, bronchi and bronchioles)
Respiratory portion- gaseous exchange takes place here with the blood stream (Respiratory bronchioles, alveolar ducts, alveolar sacs. alveoli)
Where does the exchange of gases occur?
at the alveolar capillary barrier
What is the total thickness in order for gas to be exchanged?
0.2 micron
What are the 4 layers of the tracheobronchial tree?
mucosa (epithelium and supporting lamina propria)
sub-mucosa (seromucous glands)
cartilage and/ or muscle layer
adventitia- connective tissue which covers the tree
Describe the trachea shape and length and diameter ?
wide flexible tube
15-20cm long and 2-3 cm in diameter
Describe where the trachea is?
situated between the larynx and a cartilage called carina
How many C-shaped tracheal cartilages are there?
has 16-20 C-shaped cartilage on the anterolateral aspect
What are the gaps between rings of cartilage?
at the back- the gaps between rings of cartillage filled up with the muscle called trachealis and fibroelastic tissue
What is function of respiratory mucosa and submucosa?
respiratory mucosa and submucosa are adapted to warm and moisten the air
and to trap the foreign particles in the mucous.
What is found in sub mucosa?
mixed sero-mucous glands:
the watery secretions from the serous glands humidify the inspired air.
The mucus, together with mucus from the goblet cells traps particles from the air which are transported upwards towards the pharynx by the cilia on the epithelium. This helps to keep the lungs free of particles and bacteria.
What is the innermost layer of trachea and what does it consist of?
mucosa
epithelium: ciliated pseudostratified columnar epithelium with goblet cells
lamina propria: underneath the epithelium contains elastin blood vessels
What is adventitia?
connects and supports trachea to surrounding tissue e.g. thyroid and oesophagus
contains nerves, vessels and adipose tissue
What are basal cells?
stem cells which can regenerate the columnar cells if these are damaged or renewal is needed
Where are the basal and columnar cells attached?
at one single basement membrane
What does the lamina propria contain?
areolar connective tissue where you have elastin and also blood vessels.
Possibly also some macrophages or immune cells.
Where does respiratory epithelium begin and end?
starts from nose and goes up to the level of the terminal bronchiole where it starts to become non-ciliated columnar single layer.
What’s the difference between extrapulmonary bronchi and intrapulmonary bronchi?
Extrapulmonary- primary bronchi which does not enter the lung tissue.
And closely resemble the trachea histologically.
Intrapulmonary- less cartilage and does not completely encircle the lumen.
Includes secondary, tertiary and their consecutive divisions.
Gaps in the cartillage
Contains layers of smooth muscle between mucosa and submucosa.
What is the difference between bronchi and bronchioles?
bronchioles- 1mm diameter or less
it is covered with ciliated columnar epithelium
(however non-ciliated in smaller bronchioles, e.g. terminal bronchioles)
smooth muscle thicker than bronchi
non ciliated clara cells are present :secretes surfactant
no goblet cells
non-ciliated cells
no submucosal glands
no cartilage
no glands in lamina propria
What do respiratory tubes contain?
respiratory bronchioles- ciliated cuboidal epithelium
alveolar ducts - surrounded by smooth muscle, elastin and collagen
alveolar sacs- surrounded by blood vessels/ pulmonary capillaries
alveoli- surrounded by blood vessels/ pulmonary capillaries (0.2 micro m blood-alveoli barrier). Gaseous exchange between blood and air occurs.
What are the main types of cells found in epithelium of the alveoli?
type 1 pneumocytes -large flattened cells- (95% of the total alveolar area) which present a very thin diffusion barrier for gases
type 2 pneumocytes- (making up 5 % of the total alveolar area, but 60% of total cells). These cells secrete ‘surfactant’ which decreases alveolar surface tension and stops alveoli collapsing when we breathe out
macrophages(dust cell)- are also present in the walls. These , when found in the lumen of the alveolus , are also known as “dust cells” due to their brownish appearance. Keeps respiratory system clean as we inhale dust and any foreign particles
Where does gaseous exchange take place?
through the endothelial cell of the capillary, basement membrane and type I pneumocyte
the wall of the capillary endothelial cell is fused to that of the alveolar cell, and there is only a very thin basement membrane between these two cells.
When do goblet cells dissapear?
At bronchus level, no goblet cells in bronchioles
When do clara cells appear?
from lobar bronchus to terminal bronchioles
Where are ciliated cells reduced?
where respiratory bronchiole starts
as the mucosa has simple cuboidal epithelium.
Onwards becomes squamous.
Where does seromucous gland in submucosa disappear?
at bronchus level
Where does hyaline cartilage disapear?
at bronchus level
Where does smooth muscle dissappear?
stays up to resp bronchiole then the thickness gets reduced for gas exchange
Where do elastic fibres disapear?
stay throughout the tracheobronchial tree as important for recoil of lung
What is function of club cell?
same as clara cell
protects airways
regenerates bronchiolar epithelium
produces surfactant
How is conducting portion characterized?
pseudostratified columnar epithelium with cilia
goblet cells
gland tissue
hyaline cartilage
How is respiratory portion characterized?
respiratory portion begins with the first branches of the respiratory bronchioles
epithelium gradual transition from cuboidal to simple squamous
cartilage ends
abundant smooth muscle, elastic fibres, reticular fibres
What are the three parts of the nasal cavity?
vestibule, respiratory part and olfactory
What is the vestibule outer layer and inner layer lined by?
outer:
stratified squamous - keratinised
inner:
stratified squamous- non keratinised
What is the respiratory part covered by?
respiratory epithelium
What is the olfactory part covered by?
olfactory epithelium .
What are the parts of the pharynx?
nasal part - respiratory epithelium
oral part - stratified squamous which is non keratinised
What is the surface of the epiglottis?
top surface covered with stratified squamous up to the vocal fold of the larynx.
Below vocal fold of the larynx we have respiratory epithelia
