Ed's Histology Notes: Throat

Be sure you know these words:

Mucosa / mucous membrane: The epithelium of a hollow organ, plus its underlying connective tissue, down to the first layer of muscle. The term is unfortunate, since the epithelium of a mucosa does not necessarily produce mucus.

Goblet cell: Single, barrel-shaped mucin-producing cell within a columnar or pseudostratified epithelium. It's the barrel-shape that makes it a goblet cell. Respiratory ("pseudostratified ciliated") and small-intestinal epithelium have scattered goblet cells (usually; terminal bronchioles lack goblet cells). Colonic epithelium has huge numbers of goblet cells. Endocervix, gastric cardia and antrum, and mucous glands (sublingual, Brunner's, others) produce mucin from columnar cells, not goblet cells.

Brush cell: A cell in a respiratory epithelium, with microvilli on its surface, nad afferent nerve endings attached to their basal portions. Supposedly for sensation, you'll never pick them out by light microscopy.

Kulchitsky cells / K-cells: APUD cells in respiratory epithelium. They make serotonin and much else. Nobody knows why.

Lamina propria: The connective tissue of the mucosa. (The name means the "layer" the is the "property" of the epithelium.) It's generally loose, rich in vessels and lymphatics, and contains plenty of lymphocytes.

Muscularis mucosae: A thin layer of muscle responsible for wrinkling the mucosa

Submucosa: The layer of connective tissue lying between a muscularis mucosae and the major muscular layer.

Meissner's submucosal plexus: The nerve plexus in the submucosa of the gut.

Muscularis propria / muscularis externa / muscularis (unmodified): The major muscle layer of a hollow organ, giving its strength. In the gut, the rule is "inner layer circular, outer layer longitudinal". (This make sense. Think about it.)

Auerbach's myenteric plexus: The nerve plexus in the muscularis propria of the gut.

Adventitia: The loose connective tissue of a hollow organ outside of the muscularis propria, if there is no serous membrane (i.e., no peritoneum) investing it. The adventitia blends into the surrounding connective tissue.

Serosa: The serous membrane (i.e., peritoneum) around a hollow organ.

Mesothelium: The simple-squamous layer of epithelium that lines the insides of the peritoneal, pericardial, and peritoneal membranes. The rest of the membrane is fibrous tissue which encases some hollow organs (as "serosa") and elsewhere blends with the rest of the connective tissue of the body.

Immunoglobulin A (IgA): An immunoglobulin which mostly made in the lymphoid nodules of the lamina propria, and is then transported through the epithelial cells into the lumen.

Sinus: A blind cavity off a hollow organ. You'll learn about the paranasal sinuses later.


Your throat.

You'll learn the histology of the nasopharynx later. One marvel is that the stratified squamous epithelium extends up your nostril just the distance that you could get your finger. Another is the eustachian (auditory) tubes of elastic cartilage. A third marvel is the paranasal sinuses, which are there so that your skull will weight less, and supposedly also to make you speech resonate (try talking while you hold your nose, "you sound like you have sinus trouble"). Your "upper respiratory tract" (as in "upper respiratory infection") ends at the epiglottis.


The epithelium is non-keratinizing stratified squamous epithelium. The submucosa contains mucin-secreting glands. In spite of what anyone else may tell you, only the proximal 5% or so of the esophagus has predominantly skeletal muscle in its muscularis propria. There are only a few wisps of skeletal muscle more distally, and even these soon disappear. The portion of the esophagus that reaches the abdomen has a serosa; the thoracic portion has an adventitia.


This isn't the place to review the anatomy.

The epiglottis is a big piece of elastic cartilage, covered by stratified squamous epithelium where it should contact food (i.e., the whole lingual side and the superior aspect of its laryngeal side), and by respiratory epithelium below. A mix of serous, mucinous, and mixed glands are found over the epiglottis.

The false vocal cords ("vestibular folds") are covered with respiratory epithelium and contain lots of glands, mostly serous.

The true vocal cords (for talking and protection, i.e., choking) are covered with stratified epithelium, the vocal ligaments are genuine elastic tissue, and of course the vocal muscle is skeletal muscle.

The tips of the arytenoids, and the entire cuneiform and corniculate cartilages, are (like the epiglottis) composed of elastic cartilage. The thyroid and cricoid cartilages, and the rest of the arytenoids, are hyaline cartilage; this tends to undergo transformation into bone as we get older.


The pliable windpipe. The epithelium is a typical pseudostratified ciliated columnar epithelium, with abundant goblet cells. It's as tall here as anywhere (and it will get progressively stubbier further down.) The mucosa is rich in blood vessels, for temperature regulation. The lamina propria is remarkable for "C-shaped" cartilages arranged circumferentially. These keep the trachea open. (These cartilages will become a meshwork around the smaller bronchi; this is why you can stretch the trachea like an accordion, but cannot do this with a medium-sized bronchus.) The ends of the "C"'s are connected by an sheet of smooth muscle mixed with elastic fibers, which abuts the esophagus, making swallowing nicer. The lamina propria also contains lots of serous, mucous, and mixed glands.

Visitors to www.pathguy.com
reset Jan. 30, 2005:

Meet Ed