Histology and Anatomy of the Digestive System

Updated on September 13, 2018
Deniz Burunlu profile image

Deniz Burunlu currently lives in London. He has a BSc Hons in Biomedical Sciences and currently studying Medicine.

Lip (Labia)

The lip consists of a core of striated muscle called the orbicularis oris muscle, embedded in fibro-elastic connective tissue. The outer surface is covered with skin, stratified squamous keratinised epithelium, containing many hair follicles, sebaceous glands, and sweat glands. The red margin of the lip is a transitional zone between the outer skin and inner mucous membrane. The epithelium here is thinner than the rest of the lip and the redness of the lip margin is caused by blood in the large capillary loops in the underlying connective tissue.

Tongue

The right and left halves of the tongue are separated by the lingual septum. The mucous membrane of the upper surface of the tongue is divided into the oral (2/3) and the pharyngeal (1/3) parts by a V-shaped sulcus called the sulcus terminalis.

There are 4 types of papillae found on the dorsal surface of the tongue:

  • Filiform Papillae are the most numerous and the smallest. They are conical elongated projections of connective tissue covered with keratinised stratified epithelium without taste buds.
  • Fungiform Papillae are mushroom-shaped projections located on the dorsal surface of the tongue mostly on the apex. Each has a very vascular connective tissue core. The taste buds are present in the covering stratified squamous non-keratinised epithelium.
  • Vallate Papillae are located on the dorsal surface in a row immediately in front of the sulcus terminalis. It is surrounded by a moat-like invagination lined with non-keratinised squamous epithelium that contains taste bunds. Ducks of lingual salivary glands empty their serous secretion flushing material from the moat to enable the taste buds to respond rapidly to changing stimuli.
  • Foliate Papillae consists of parallel low ridges separated by deep mucosal clefts

The tongue has two types of muscles: Intrinsic and Extrinsic.

The Intrinsic muscles have no external attachments and they alter the shape of the tongue:

  • Superior longitudinal muscle
  • Inferior longitudinal muscle
  • Vertical muscle
  • Transverse muscle

The Extrinsic muscles extend from the tongue to the mandible, styloid process, and soft palate. These muscles alter the position of the tongue:

  • Genioglossus muscle
  • Hyoglossus muscle
  • Styloglossus muscle
  • Palatoglossal muscle

Blood supply is via the lingual artery and the lingual vein. Nerve supply to the intrinsic and extrinsic muscles is via efferent motor nerve fibres from the hypoglossal nerve, except for the palatoglossus muscle, which receives innervation from the vagus nerve.

Oesophagus

A muscular tube about 25 cm long that extends from the pharynx to the stomach. The oesophagus begins in the neck at the 6th cervical vertebra level and ends at the gastric cardiac orifice. It is situated in three topographic regions: cervical. thoracic, and abdominal.

The walls of the oesophagus consist of three layers:

  • Tunica Mucosa (mucous membrane)
    • Non-keratinised stratified squamous epithelium
    • Lamina propria
    • Muscularis mucosa (longitudinal smooth muscle)
    • Submucosa (tubulo-acinar mucous glands)
  • Tunica Muscularis (muscular coat)
    • Upper 1/3 is striated muscle (continuation of the muscle of the oropharynx)
    • Middle 1/3 is interwoven striated and smooth muscle
    • Distal 1/3 is smooth muscle (like the rest of the digestive system)
  • Tunica Adventitia
    • Outer layer by which the oesophagus is fixed to adjoining structures throughout its length in the thoracic cavity.

Stomach

The stomach is an intraperitoneal organ located in the epigastric region. The stomach is divided into three regions: cardia, pylorus, fundus.

The fundus is a dome-shaped area that projects upwards. Glands of the fundus and body are simple tubular glands that posses four type of cells: peptic cells, parietal cells, mucous neck cells, and enteroendocrine cells.

The pylorus connects the stomach to the duodenum. It is considered to have two parts: Pyloric antrum (opening to the body of the stomach) and the Pyloric canal (opening to the duodenum). The pyloric glands are located in the pyloric antrum and they are branched, coiled, and tubular glands with a relatively wide lumen.

The stomach wall has three layers:

  • Tunica Mucosa
    • Mucous secreting simple columnar epithelium
    • Lamina propria
    • Muscularis mucosae (inner circular and outer longitudinal muscle)
    • Submucosa
  • Tunica Muscularis (important for mixing chyme)
    • Outer longitudinal
    • Middle circular
    • Inner oblique
  • Tunica Serosa
    • Continues with the peritoneum of the abdominal cavity via the omentum.

The Fundus
The Fundus
The Pylorus
The Pylorus

Small Intestine

The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal fold. Functionally, the small intestines are the principal site for digestion and absorption of products of digestion. The small intestine can be divided into three parts: duodenum, jejunum, and ileum.

Vili are present with lamina propria core, and brush border on the outermost surface with goblet cells. The arterial supply to the ileum is from the superior mesenteric artery.

The duodenum is a c-shaped tube that curves are the head of the pancreas. It is divided into four parts: superior, descending, inferior, and ascending parts. The first 2.5cm of the duodenum resembles the stomach and it is covered on its posterior and anterior surface with peritoneum. In the duodenum, the submucosa contains compound acinotubular glands called Brunner’s glands. Blood supply is via the superior and inferior pancreaticoduodenal artery, while nerve supply is via the mesenteric plexuses.

Duodenum
Duodenum
Ileum
Ileum

Large Intestine

The large intestine has three main parts:

  • Cecum (with appendix)
  • Colon (ascending, descending, transverse, and sigmoid colon)
  • Rectum and anal canal

Large Intestine Wall:

  • Tunica Mucosa
    • Simple columnar epithelium (mucous cells, microfold cells, enteroendocrine cells, brush cells, goblet cells)
    • Lamina propria
    • Muscularis mucosa (longitudinal and circular layers)
    • Submucosa
  • Tunica Muscularis (smooth muscle layer)
    • Outer longitudinal
    • Inner circular
  • Tunica Serosa
    • Forms the outer most layer, consists of simple squamous epithelial tissue that secretes watery serous fluid to lubricate the surface of the large intestine, protecting it from friction between abdominal organs and the surrounding muscles and bones.

Appendix

The appendix is attached to the posteromedial wall of the cecum, just inferior to the end of the ileum. The appendix is narrow, hollow, blind-ended tube connected to the cecum. It has a large formation of lymphoid tissue.

The walls of the appendix are similar to the large intestine:

  • Tunica Mucosa
    • Simple columnar epithelium
    • Lamina propria
    • Muscularis mucosa
    • Submucosa
  • Tunica Muscularis (smooth muscle)
    • Outer longitudinal
    • Inner circular
  • Tunica Serosa

Questions & Answers

    © 2018 Deniz Burunlu

    Comments

      0 of 8192 characters used
      Post Comment

      No comments yet.

      working

      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, owlcation.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://owlcation.com/privacy-policy#gdpr

      Show Details
      Necessary
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Features
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Marketing
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Statistics
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
      ClickscoThis is a data management platform studying reader behavior (Privacy Policy)