Histology Flashcards
explain the histology of the component parts of the respiratory system - nasal cavity
roof of nasal cavity contains an area of specialised olfactory epithelium
the initial part of nasal cavity, the vestibule, is lined by keratinised stratified squamous epithelium
deeper into the nasal cavity, keratin is lost, and deeper still it changes to respiratory epithelium (pseudo-stratified, ciliated, columnar epithelium with goblet cells)
respiratory epithelium lines nearly all the rest of the conducting part of respiratory tract
underneath the respiratory epithelium is the lamina propia - a band of loose connective tissue containing seromucous glands and thin walled venous sinuses which can quickly engorge with blood and block the nose
explain the histology of the component parts of the respiratory system - pharynx
is lined by non-keratinzed stratified squamous epithelium
explain the histology of the component parts of the respiratory system - larynx
walls are made up of cartilage and muscles with respiratory epithelium lining its surfaces
exception is vocal folds and adjacent structures which are covered with stratified squamous epithelium
explain the histology of the component parts of the respiratory system - trachea
contains 15-20 C shaped cartilage rings
open side of C cartilage is spanned by fibroelastic tissue and smooth muscle (trachealis muscle)
walls lined with respiratory epithelium backed by a basal lamina, a lamina propria of connective tissue with abundant elastic fibres and a submucosa of connective tissue that includes numerous seromucous glands
explain the histology of the component parts of the respiratory system - bronchi
rings of hyaline cartilage are replaced by irregularly shaped cartilage plates
wall of bronchus is made up of bronchus is made up of respiratory epithelium, a lamina propria, a muscularis consisting a ring of smooth muscle and a submucosa with adipose tissue and some seromucous glands
explain the histology of the component parts of the respiratory system - bronchioles
lack cartilage and glands but may contain a few goblet cells in their initial portion
epithelium decreases in height from columnar to cuboidal as you progress down the respiratory tree to
the smallest bronchioles
lamina propria is composed of smooth muscle and elastic and collagenous fibres
smooth muscle of bronchioles respond to parasympathetic innervation, histamine and other factors by contracting and constricting the diameter of the bronchiole
this mechanism plays significant role in asthma attacks and allergic reactions
the smallest bronchioles that lack respiratory function are referred to as terminal bronchioles and these branch to give rise to the first part of the respiratory tree that has respiratory function - respiratory bronchioles
terminal bronchioles are lined with cuboidal ciliated epithelium and contain non-ciliated club cells (roles - stem cells, detoxification, immune modulation, surfactant production) that project above the level of adjacent ciliated cells
explain the histology of the component parts of the respiratory system - alveoli
alveoli interrupt continuity of respiratory bronchioles and are lined with discontinuous squamous type I and II alveolar cells (pneumocytes)
the terminal portions of bronchial tree and responsible for spongy nature of lungs
thin-walled pockets
explain the changes in structure of the walls of the conducting airways as you descend the respiratory tree
as bronchi branch become smaller the cartilage becomes more discontinuous and is finally lost when the airway is about 1mm in diameter
these smaller airways lacking cartilage are called bronchioles
explain the structure of alveoli and how the structure is suited to allowing gas exchange
gas exchange takes part within alveoli - the walls of alveoli contain capillaries
type 1 alveolar cells - simple squamous epithelium that lines the alveolar surfaces covering over 90% of the alveolar surface. Provide a barrier of minimal thickness that is permeable to gases
explain the role of surfactant in maintaining the patency of alveoli and the cell types responsible for surfactant production
type II alveolar cells - polygonal in shape, the free surface is covered by micorvili and the cytoplasm displays dense membrane bound lamellar bodies which contain surfactant
the surfactant released by exocytosis and spreads over the pulmonary surface to reduce the surface tension at the air-fluid interface. This reduces the tendency for the alveoli to collapse at the end of expiration
explain the role of alveolar macrophages
dust cells - free cells wither in septa or migrating over the luminal surfaces of alveoli, phagocytosing inhaled particles that may have escaped entrapment by mucous lining of the airway
typically will migrate up the bronchial tree, transported by ciliary action, to the pharynx where they are swallowed or will move into septal connective tissue where they will remain
describe the air blood barrier
septa between alveoli are permeated by capillary networks
the tissue is thin at these points between air and blood –> air-blood barrier
consists of type 1 cell and basal lamina of each
describe the visceral pleura
surrounds lung and is multi-layered
outer layer (faces parietal pleura) of simple squamous epithelium - mesothelium - backed by layers of fibrous and elastic connective tissue
between parietal and visceral pleura is a pleural cavity containing small amount of lubricating fluid
