Histology and Embryology Flashcards
What are 5 functions of the respiratory system?
Supplies oxygen to the blood Removes CO2 from the blood Speech Smell Lung function in BP control
The nasal cavity provides an extensive area for what?
Warming, moistening and filtering air
What is the roof of the nasal cavity composed of?
Specialised olfactory epithelium
What is the initial part of the nasal cavity known as?
The vestibule
What is the nasal vestibule lined with?
Keratinised stratified squamous epithelium
What happens to the epithelium as you travel further into the nasal cavity?
First, keratin is lost and then further on it turns into respiratory epithelium
What is respiratory epithelium?
Pseudostatified ciliated columnar epithelium with goblet cells
What are basal cells?
Stem cells
Why are basal cells present in respiratory epithelium?
Because this epithelium gets regenerated quickly, about once a week
What is underneath the respiratory epithelium?
Lamina propria
What is the lamina propria?
Band of connective tissue containing seromucus glands and a rich venous plexus
What is the oropharynx and anterior part of the epiglottis lined with?
Non-keratinised stratified squamous epithelium
What are the walls of the larynx made up of?
Muscle, cartilage and respiratory epithelium
What is the exception in the larynx which is not covered by respiratory epithelium?
Vocal cords and adjacent structures
What are the vocal cords covered with instead of respiratory epithelium?
Stratified squamous epithelium
What is continuous with the larynx?
Trachea
How does the trachea terminate?
By branching into the main bronchi
How many cartilages does the trachea have?
15-20
The open side of a C shaped tracheal cartilage is spanned by what?
Fibro-elastic tissue and smooth muscle
What lines the surface of the trachea?
Mucus
What are the effects of smoking on removal of foreign substances from the airway?
First, cilia is lost. Second, respiratory epithelium will be turned into stratified squamous so no mucus can be moved
What type of cartilage is found in the trachea?
Hyaline
What happens to hyaline cartilage in the bronchi?
Rings are replaced by irregularly shaped plates
What allows oxygen supply to the lungs and large airways?
Bronchial blood supply
What is the rough diameter of a bronchi?
< 1mm
What do bronchioles lack?
Cartilage and glands
What happens to the epithelium as you progress down the respiratory tree?
It gets shorter and changes from columnar to cuboidal
What are the smallest bronchiole which lack gas exchange function known as?
Terminal bronchioles
Terminal bronchioles branch to give what?
Respiratory bronchioles- first part which can perform gas exchange
Smooth muscles of the bronchioles respond to what to cause contract and constrict?
Parasympathetic innervation and histamine
What are club/clara cells?
Bronchiolar exocrine cells
What are the two types of club cells?
Ciliated and non-ciliated
What are different roles of club/Clara cells?
Stem cells, detoxification, immune modulation, surfactant production
What is another name for alveolar cells?
Pneumocytes
What are type 1 alveolar cells?
Simple squamous epithelium that lines 90% of alveolar surface
What do type 2 alveolar cells do?
Produce surfactant
How is surfactant released and what does it do?
Exocytosis- reduces surface tension to prevent alveoli collapsing
Why do premature infants struggle to keep their airways open?
Alveoli haven’t developed properly and so surfactant isn’t produced
What other cell is present in alveoli?
Macrophages
What do macrophages in the alveoli do?
Phagocytose inhaled particles which have escaped mucus entrapment and travel up to the pharynx to be swallowed
Embryologically, where does the lining of the trachea and bronchial tree come from?
Endoderm
Embryologically, where does all other lung tissue come from?
Visceral mesoderm
What are two congenital respiratory conditions?
Oesophageal atresia and trachea-oesophageal fistula
What is oesophageal atresia?
Oesophagus has a blind ending instead of connecting normally to the stomach
What part of lung development occurs in the embryological phase? When is this?
26 days-6 weeks: respiratory diverticulum forms and there is initial branching to give lungs, lobes and segments
What stage does the branching of the terminal bronchioles occur? When is this?
Pseudoglandular: 6-16 weeks
What happens in the canalicular stage of development? When is this?
16-28 weeks: terminal bronchioles divide to respiratory bronchioles and alveolar ducts
In what developmental stage do terminal sacs form and capillaries establish contact? When is this?
28-36 weeks: saccular
What stage of development do the alveoli mature? When is this?
Alveolar- 36 weeks-early childhood
What does not enough surfactant cause in babies?
Respiratory distress syndrome
