Page 267 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

Respiratory system (apparatus respiratorius) 249

VetBooks.ir bronchiole v. pulmonalis
Terminal

a. bronchialis

a. pulmonalis
Respiratory
bronchiole
with alveoli

Alveolus Alveolar capillaries

Alveolar duct
Inter-alveolar septum

Alveolus

11.15 Peripheral bronchial tree with alveoli and vascular supply (schematic).

11.16 Wall of bronchus (schematic).

Mixed bronchial glands (glandulae bronchiales) The lamina propria contains abundant connective
are present in the lamina propria and in the submucosa. tissue composed mainly of collagen, but also elastic
These produce a watery, serous secretion rich in protein- fibres. Blood vessels, lymph vessels, nerves and solitary
and glycoprotein-containing mucus. Within the lumen of lymphoid follicles are also present. Externally adjacent to
the bronchi, proteinaceous serum components, immu- the lamina propria is a layer of smooth muscle (Figure
noglobulin A, lactoferrin and glycoproteins are added. 11.16). Proximally, the orientation of the muscle is cir-
These substances aid in protecting the epithelial cells by cular, transitioning into a spiral lattice in the smaller
preventing attachment of viruses and bacteria to the epi- bronchi. The muscle fibres conform to the alignment of
thelium or by a direct bacteriostatic effect. the elastic fibres. The mucosa often appears folded due to

Vet Histology.indb 249 16/07/2019 15:03