Tissues, Organs and Systems Flashcards
From inside to out, what are the layers of the trachea?
- Lumen
- Mucous membrane made of pseudostratified ciliated columnar epithelium
- Submucosa, containing seromucous glands
- Hyaline cartilage ring (horse shoe shape)
- Adventitia
What is the structure of the mucosa in trachea?
- Epithelial layer is several layers deep
- Surface covered in cilia (moves debris, dust, bacteria etc. towards mouth)
- Lamina propria is very thin
- No muscularis mucosa layer
What is the structure of the submucosa of the trachea?
- The connective tissue layer contains mainly collagen and elastin fibres and many fibroblasts
- Contains seromucous glands that produce watery mucus that thickens during infections
What are the features of the cartilage in the trachea?
- C-shaped hyaline cartilage ring
- Made of two distinct layer:
- perichondrium layer (contains fibroblasts that lay down collagen fibres)
- chondrogenic (contains chondroblasts which form cartilage)
The cells present can interconvert from chondroblasts to chondrocytes and so can make both hyaline and elastic cartilage
What do secretions are produced from the epithelium and and submucosal glands of the trachea and bronchi?
- Mucins and water (makes sticky mucus)
- Serum proteins (lubricate the surface)
- Lysozymes (destroy bacteria)
- Anti-proteases (inactivate bacterial enzymes)
What makes up the mucociliary escalator?
The ‘cilia wave’ and mucous moves materials to oral cavity where it can be swallowed- making the mucociliary escalator
What does cilia contribute to the mucociliary escalator?
- Tracheal mucosa contains approximately 250 cilia/cell
- Cilia beat at 12Hz beneath a moveable, viscoelastic mucus blanket
What does trachea look like in histology?
- Unusually thick basement membrane
- Lamina propria rich in immune cells and contains layers of elastic
What differences in structure are there between primary and secondary/tertiary bronchi?
- ## Histology similar to primary bronchi but cartilage is only present as cresents and not full C-shapes
What features are present in secondary and tertiary bronchi?
- Epithelium made of pseudostratified ciliated columnar cells
- Bound by smooth muscle
- Supported by seromucous glands in the submucosa
- Airway kept open by crescent shaped hyaline cartilage.
- No layer of outer smooth muscle
How are alveolus connected to capillaries?
- Capillaries are lined with flattened specialised epithelial cells (called endothelium)
- These cells are attached to fused basal lamina with even thinner specialised cells of the air sac
How are alveoli adapted for their function?
- Folds in basal lamina allow for expansion of the air sacs when air is drawn into the lungs
- At junctions, small amounts of collagen are present and surrounded by layers of elastin fibres in the mucosa to allow recoil
- The connective tissue ‘muscle’ layers in the mucosa are created by the collagen and elastin fibres