3.6.2. Histology of Respiratory Flashcards
What are the 3 main components of the respiratory system?
- Respiratory controller: neural control
- Ventilatory pump: muscles, bones, CT
- Gas Exchanger: lungs i.e. airways and alveoli
Describe the different types of control that we have over our breathing:
- Behavioral control (voluntary muscles–like holding your breath, blowing out candles, etc.)
- Automatic control (medulla and pons)
We also have feedback from lungs and chemoreceptors and monitor and respond to levels of oxygen and acidemia
How is the nervous system involved in the respiratory system?
- CNS
- Phrenic nerve innervates the diaphragm
- Sensory receptors sense flow, pressure changes
- Info back to the brain via the vagus nerve
- Sympathetic nerves terminate near the airways (bronchoDILATION)
- Parasympathetic nerves cause bronchoCONSTRICTION
Which anatomic features are involved in the ventalitory pump?
- Chest wall muscles
- Chest wall skeleton
- Chest wall connective tissue (especially elastic tissue)
- Pleura
- Airways
- Spinal cord and peripheral nerves
What are the functions of the ventilatory pump?
- Create the negative pressure that will bring in gases
- Distribute gases through the system
- Minimize energy expenditure (why elastic components are so important)
What happens during QUIET inspiration?
The diaphragm moves 1 cm and the ribs are lifted by muscles. The intrathoracic pressure falls and air is inhaled.
What happens during QUIET expiration?
This is a passive process with no muscle action. The elastic recoil and surface tension in alveoli pulls inward, and the alveolar pressure increases and air is pushed out.
What muscles are involved during FORCED inspiration?
sternocleidomastoid, scalenes and pectoralis minor lift chest upwards as you gasp for air (traps and rhomboids are also involved)
What muscles are involved during FORCED expiration?
Abdominal muscles force the diaphragm up, and the internal intercostals depress the ribs.
What do we mean by “air conditioning”?
We moisturize and warm the air as we breathe it in.
How do we define olfaction?
- Sense of small
- Information processing (we are sensing the environment as air comes in)
Name some histologic features of olfactory epithelium:
- Pseudostratified columnar epithelium
- Olfactory cells are bipolar neurons
- Non-motile cilia on olfactory vesicle
- No goblet cells
- Supporting cells (like sustenaculum)
- Stem cells
- Basement membrane is not thick
- Bowman’s glands release SEROUS secretion to moisten apical surface of epithelium
What are the differences between the FALSE and TRUE vocal folds?
False: proximal, surface is PCC, core has serous glands
True: distal, surface is stratified squamous epithelium, core=skeletal muscle (vocalis), vocal ligament
Describe the path of air between the trachea and the bronchioles:
Trachea–> primary bronchi–> lobar bronchi=lobes –> segmental bronchi–> smaller bronchi–> bronchioles
What is one histological difference between bronchi and bronchioles?
Bronchi have cartilage and bronchioles do not!
What are the requirements for the gas exchanger system?
- Large area for gas diffusion
- Minimize distance for diffusion
- Maintain structural integrity of gas exchanger to minimize probability of lung collapse
- Match ventilation and blood flow
What is the difference between the pulmonary artery and the bronchial artery?
Pulmonary artery: brings in blood that needs to be oxygenated
Bronchial artery: brings in oxygenated blood to support the lung bronchioles
What are some facts about the pulmonary vasculature?
- Resistance is low in the pulmonary system
- Pressures are lower than in the systemic arteries
- Vessel walls are thinner than in systemic vessels
As PO2 drops in an alveolus, the resistance in the arterioles feeding the capillary beds increases so…
…blood flow to non-ventilated sections of the lung decreases.
(This helps match perfusion, or blood flow, to ventilation)
When air pressure in the alveoli is higher than blood pressure in the capillaries, then…
…the air pressure can collapse the capillaries.
What are the histologic features of alveoli?
- Lumen of alveolus contains air, some debris, alveolar macrophages move along surface lining
- Surface of alveolar lining epithelium are squamous cells (type I) and larger cells (type II–produce surfactant) (Also known as pneumocytes)
- Surface of epithelium covered by surfactant
- Some connective tissue (including elastic fibers) between alveolar basal lamina and endothelial basal lamina
- Endothelium of alveolar capillaries
- Lumen of capillary contains all components of circulating blood
What have we learned about Type II pneumocytes (or Greater Alveolor, or Septal Cell)?
- Secretes the majority of pulmonary surfactant, which decreases alveolar surface tension and prevents alveolar collapse (“atelectasis”)
- Matures late in pregnancy
- Premature babies often have a deficiency in surfactant and are more likely to develop Respiratory Distress Syndrome
- It’s role in Hyaline Membrane Disease
- SP-A (1 of 3 surfactant molecules) may play a role in inducing parturition
- In the alveoli, they tend to be cuboidal in shape and clustered in groups of 2 or 3
- They also serve as precursors to Type I cells and other Type II cells. These cells have the capacity to proliferate during lung damage
What do we know about Type I pneumocytes?
- Comprise of 95% of alveolar surfaces and line the alveoli
- Their squamous shape is optimal for gas exchange
- Organelles are clumped around the nucleus, allowing for such a thin cell body
What do we know about alveolar macrophages?
Aka “Dust cells” are involved in phagocytosis (have inclusion bodies of the stuff they have digested), and host defense modulation
