Histology · MU Sofia

salivary glands

Covers the three paired major salivary glands and the minor glands, their serous, mucous and seromucous classification, and the enzymes and mucin they secrete along with parasympathetic control of salivation. Also outlines embryonic development from an epithelial placode, with timing for each gland, and then compares the histology of the submandibular, parotid and sublingual glands, including acini, serous demilunes and intralobular ducts.

Inside: 1 section · 7 labelled pictures · 34 flashcards · 5 min

Topic 14 of 17 in the MU Sofia syllabus for Histology (Medicine, Year 2). The free AceMed note covers it in 1 section, about 776 words (5 min of reading), with 34 flashcards.

In this note

  1. Introduction

Introduction

  • The salivary glands are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed).
  • In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant. In humans, between 0.5 and 1.5 l of saliva are produced every day.
  • The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increased salivation.
  • Embryonic Origin and Formation (Informations for final exam):
  • Salivary glands originate from an epithelial placode during embryonic development.
  • In mice, this process occurs between embryonic days 11 (E11) and 16 (E16), while in humans, it spans from the 4th to the 12th embryonic weeks.
  • Initially, the placode grows and extends into the underlying mesenchyme, acquiring a bud shape.
  • The epithelium invaginates into the connective tissue, bringing the basal lamina with it.
  • The invagination develops a lumen that communicates with the original surface.
  • Eventually, the invagination differentiates into a secretory unit (acini) and a duct connecting it to the epithelium.
  • Different salivary glands appear at distinct time points:
  • Parotid and submandibular glands: 5-6 weeks of intrauterine life (I.U.L.)
  • Sublingual glands: 7-8 weeks of I.U.L.
  • Minor salivary glands: Develop around the third month of I.U.L.12

Histology of Salivary glands

  • Both major and minor S.G. composed of parenchyma elements are derived from oral epithelium. and consists of secretary end piece or acini either serous or mucous or a combination of the two called serous demilunes and these secretary units leading into ducts that open into oral cavity. The connective tissue (C.T.) forms a capsule around the gland and extends into it, dividing groups of secretary units and ducts into lobes and lobules, the blood and lymph vessels and nerves that supply the gland are contained within Capsule.
  • key components of the submandibular gland histology :
  • Stroma: Connective tissue that supports the gland.
  • Capsule: Encloses the gland.
  • Lobule: Divides the gland into lobules.
  • Parenchyma: The functional part of the gland, consisting of secretory cells and ducts.

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