SH Practical - Respiratory

From Embryology


Respiratory tract

Current page provides further background information for Medicine phase 1 Society and Health Respiratory Histology Practical Virtual Slides.

Virtual Slides: Respiratory Histology


  • page content is not part of the SH practical class virtual slides.
  • page content only supports the histology component of practical class (not the pathology).

SH Links: Lymphatic Lecture | Lymphatics Practical Support | Respiratory Lecture | Respiratory Practical Support | Medicine

Virtual Slides

Moodle icon2.jpg Moodle Lab Slides - Respiratory tract: normal and inflamed

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Respiratory Tract
  1. upper - consisting of the nose, nasal cavity and the pharynx.
  2. lower - consisting of the larynx, trachea, bronchi and the lungs.
Mouse trachea 01-icon.jpg
 ‎‎Trachea cilia
Page | Play

Movie showing respiratory epithelium cilia movement.

Upper Respiratory Tract - Nasal Cavity


Respiratory histology 12.jpg Respiratory histology 11.jpg
Nasal respiratory epithelium (inferior concha) Nasal respiratory epithelium (detail)
Nasal Respiratory Histology: overview image | detail image | Histology | Histology Stains


Nasal cavity olfactory epithelium cells

  1. Olfactory cells
  2. Sustentacular cells - located mainly in the superficial cell layer of the epithelium (difficult to distinguish from olfactory cells).
  3. Basal cells - identified by their location.
  • Cilia are not visible
  • goblet cells are absent from the olfactory epithelium.
Lamina Propria
  • olfactory axon bundles (lightly stained, rounded areas) connected to olfactory cells.
  • Bowman's glands - (small mucous glands, olfactory glands) function to moisturise the epithelium.

Respiratory histology 13.jpg Respiratory histology 14.jpg
Nasal cavity olfactory Nasal cavity olfactory (detail)
Nasal Olfactory Histology: overview image | detail image | Smell Development | Histology | Histology Stains

Lower Respiratory Tract - Trachea

Larynx and Upper Part of the Trachea
Respiratory Tract Cartilages
trachea histology

Mucosa - formed by epithelium and underlying lamina propria.

  • respiratory epithelium - (pseudostratified columnar and ciliated) ciliated cells, goblet cells, brush cells, endocrine cells, surfactant-producing cells (Clara cells), serous cells, basal cells, basement membrane.
  • lamina propria - loose connective tissue, many elastic fibres.
  • elastic lamina - forming the border between the mucosa and submucosa is not visible in H&E stained slides.

Submucosa - connective tissue and submucosal glands.

Submucosal Glands

(muco-serous) serous (dark) and mucous (light) parts have different staining appearance.

  • Mucous secretions - "slimy" (high viscosity) mucous acini cells appear "foamy" or "frothy" and poorly stained (light). nuclei dark and smaller than serous.
  • Serous secretions - "watery" (low viscosity) serous acini cell apical cytoplasm is usually well-stained (dark). nuclei round to ovoid located in cell basal cytoplasm.


  • perichondrium - surface of cartilage.
  • tracheal cartilage - hyaline cartilage, 16 to 20 C-shaped cartilages.
  • trachealis muscle - (smooth muscle) Not visible in this section, together with connective tissue fibres, join ends of the cartilages together.

Hyaline Cartilage Development

  • forms from mesenchymal cells.
  • precursor cells become rounded and form densely packed cellular masses, chondrification centres.
  • chondroblasts - (cartilage-forming cells) begin secreting the extracellular matrix components of cartilage.
    • extracellular matrix - ground substance (hyaluronan, chondroitin sulfates and keratan sulfate) and tropocollagen (polymerises into fine collagen fibres, not visible).
Trachea Histology Links: Overview HE | Overview VG | Detail 1 HE Detail 2 HE | Respiratory Histology | Histology Stains | Histology

Hyaline cartilage 03.jpg Hyaline cartilage 04.jpg

Respiratory histology 05.jpg Respiratory histology 06.jpg

Trachea Histology Links: Overview HE | Overview VG | Detail 1 HE Detail 2 HE | Respiratory Histology | Histology Stains | Histology


Respiratory conducting zone - trachea, the bronchi, and bronchioles.

Respiratory histology 01.jpg Respiratory histology 09.jpg

Alveolar Ducts and Alveoli

Respiratory zone - respiratory bronchioles, alveolar ducts and alveoli.

Lung secondary lobule 01.jpg Lung primary lobule 01.jpg Alveolar-sac-01.jpg
Lung structure Alveoli and blood vessels The alveoli cellular structure

Alveolar type I cells
  • small alveolar cells or type I pneumocytes
  • are extremely flattened (the cell may be as thin as 0.05 µm)
  • form the bulk (95%) of the surface of the alveolar walls.
  • The shape of the cells is very complex, and they may actually form part of the epithelium on both faces of the alveolar wall.
Alveolar type II cells
  • large alveolar cells or type II pneumocytes
  • about as many type II cells as type I cells (cell shape accounts for small contribution to alveolar area).
  • irregularly (sometimes cuboidal) shaped.
  • form small bulges on the alveolar walls.
  • contain are large number of granules called cytosomes (or multilamellar bodies)
    • consist of precursors to pulmonary surfactant (mixture of phospholipids that keep surface tension in the alveoli low).

Respiratory histology 08.jpg Respiratory histology 07.jpg

Respiratory histology 02.jpg Respiratory histology 03.jpg Respiratory histology 04.jpg Respiratory histology 10.jpg
Alveolar Duct Alveoli Alveoli Elastin Lung Reticular Fibres


Respiratory Histology: Bronchiole | Alveolar Duct | Alveoli | EM Alveoli septum | Alveoli Elastin | Trachea 1 | Trachea 2 | labeled lung | unlabeled lung | Respiratory Bronchiole | Lung Reticular Fibres | Nasal Inferior Concha | Nasal Respiratory Epithelium | Olfactory Region overview | Olfactory Region Epithelium | Histology Stains


  • alveolar type I cell - (small alveolar cell, type I pneumocyte), extremely flattened and branched cell forming the bulk (95%) of the surface of the alveolar walls. Contain multiple cytoplasmic plates and relatively devoid of organelles, plates are the gas exchange surface in the alveolus. (More? Image - Respiratory Alveoli)
  • alveolar type II cell - (large alveolar cell, type II pneumocyte) cuboidal to irregular shaped cells forming small bulges on the alveolar walls. Contain large number of granules (cytosomes or multilamellar bodies) precursors to pulmonary surfactant. (More? Image - Respiratory Alveoli)
  • alveolar macrophage - (dust cell), irregular shaped cells lying with the fluid wall of the alveolar space. Monocyte-derived immune system cell that removes debris and microorganisms from the alveoli and may have immune roles. (More? Image - Respiratory Alveoli)
  • Bowman's gland - (small mucous gland, olfactory gland) the main function of these glands is to moisturise the epithelium.
  • cavernous body - (cavernous sinusoid) Thin-walled spaces located in the nasal cavity respiratory region lamina propria. The space is formed by veins in the lamina propria and may have a role in altering local nasal air flow in response to temperature, humidity and CO2-content of the inspired air.
  • cilium - (plural cilia) An epithelial cell microtubule-based surface specialization. Cilia are thin, tail-like projections extending approximately 5–10 micrometers outwards from the cell body. There are two types of cilia, motile cilia and non-motile cilia. Motile cilia (respiratory epithelia, trachea, uterine tube, ependymal cells) move and constantly beat in a single direction, resulting in movement of the overlying fluid. Non-motile cilia lack dynein arms and are associated with sensory system epithelium (olfactory epithelium). (More? Movie - Respiratory Cilia Movement)
  • dust cell - see alveolar macrophage.
  • goblet cell - Named by the cell shape following histological preparation, cell produces membrane-bound secretory granules filled with mucus in the respiratory and intestinal epithelium. Mucus consists of mucins (highly glycosylated proteins) suspended in a solution of electrolytes.
  • hyaline cartilage - Development from mesenchymal cells forming a chondrification centre. Mature cartilage contains chondrocytes lying in lacunae within isogenic groups surrounded (territorial matrix) and separated from other groups (interterritorial matrix) by the matrix. Cartilage surface is covered with perichondrium that merges with a layer of dense connective tissue. (More? Image - Hyaline Cartilage | Cartilage Histology)
  • perichondrium - a layer of dense connective tissue surrounding the cartilage and blending with it's surface. Mesenchymal cells in the deep part of the perichondrium (chondrogenic layer) differentiate into chondroblasts. (More? Image - Hyaline Cartilage | Cartilage Histology)
  • sustentacular cell - (supporting cell) provide mechanical and metabolic support for olfactory cells.
  • type I pneumocyte - see alveolar type I cell.
  • type II pneumocyte - see alveolar type II cell.

Respiratory Links: respiratory | Science Lecture | Lecture Movie | Med Lecture | Stage 13 | Stage 22 | upper respiratory tract | diaphragm | Histology | Postnatal | respiratory abnormalities | Respiratory Quiz | Respiratory terms | Category:Respiratory
Historic Embryology - Respiratory 
1902 The Nasal Cavities and Olfactory Structures | 1906 Lung | 1912 Upper Respiratory Tract | 1912 Respiratory | 1913 Prenatal and Neonatal Lung | 1914 Phrenic Nerve | 1918 Respiratory images | 1921 Respiratory | 1922 Chick Pulmonary Vessels | 1934 Right Fetal Lung | 1936 Early Human Lung | 1937 Terminal Air Passages | 1938 Human Histology

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, May 18) Embryology SH Practical - Respiratory. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G