Histology - Resp. Flashcards
What is the physical process of respiration?
Ventilation which involves inspiratory and expiratory movement of the chest wall
What is the chemical process of respiration?
Exchange of gases between air and blood takes place at cellular level
What is the autonomic innervation of the respiratory system?
Parasympathetic - bronchoconstriction, mucous secretion and vasodilation
Sympathetic - bronchodilation
What are the 4 main layers of the respiratory system?
Mucosa
Submucosa
Cartilage and/or muscle layer
Adventitia
Describe the histology of the trachea
Wide flexible tube with 20 C-shapes tracheal cartilages
Gaps between rings are filled by trachealis muscle and fibroelastic tissue
Mucosa and submucosa are adapted to warm and moisten the air
What is the nature of the C-shaped cartilage rings of the trachea?
Hyaline
Explain the mucosa of the trachea
Epithelium - ciliated pseudostratified columnar epithelium with goblet cells
Lamina propria - is underneath the epithelium and contains elastin and blood vessels
Explain the submucosa of the trachea
Mixed sero-mucous glands - watery secretion from serous glands humidify the air
Mucus from goblet cells traps particles from the air - keeps free from bacteria
Explain the adventitia of the trachea
Connects and supports trachea to surrounding tissue - thyroid and oesophagus
Contains nerves, vessels and adipose tissue
Describe the histology of the extrapulmonary bronchi
Closely resemble the trachea histologically
Describe the histology of the intrapulmonary bronchi
There is less cartilage then trachea and it does not completely circle the lumen
Contains layers of smooth muscle between the mucosa and submucosa
Describe the histology of bronchioles
Pseudostratified ciliated columnar epithelium decreases in height in the bronchioles to become simple columnar to cuboidal epithelium
Smooth muscle increases and Clara cells are present
No goblet cells, non-ciliated cells, no submucosal glands and no cartilage
What do Clara cells do?
Secretes surfactant
Describe the histology of the terminal and respiratory bronchioles?
Terminal bronchiole is lined by simple cuboidal epithelium with Clara cells and give rise to respiratory bronchiole
Respiratory bronchiole is lines with low cuboidal epithelium
Describe the histology of alveolar ducts?
Surrounded by smooth muscle, elastin and collagen
What are the major characteristics of bronchioles?
Lack cartilage and smooth muscle layer is relatively thicker
Many non-ciliated Clara cells in epithelium
No glands in the lamina propria
What are type I pneumocytes?
Large flattened cells which present a very thin diffusion barrier for gases
What are type II pneumocytes?
These cells secrete surfactant which decreases alveolar surface tension and stops alveolar collapse
What are dust cells - macrophages in the alveoli?
Found in the lumen of the alveolus
Have brownish appearance
Describe the alveolar-Capillary/ Blood-Air interface
Gaseous exchange takes place through the endothelial cell of the capillary, basement membrane and type I pneumocyte
Wall of capillary endothelial cell is fused to alveolar cell, and only thin basement membrane between
What is the conducting portion characterised by?
Pseudostratified columnar epithelium with cilia
Goblet cells
Gland tissue
Hyaline cartilage
What is the respiratory portion (begins at respiratory bronchioles) characterised by?
Epithelium gradual transition from cuboidal to simple squamous
Cartilage ends
Abundant smooth muscle, elastic fibres and reticular fibres
