WEEK 1: UPPER GIT HISTOLOGY Flashcards
State the 4 main layers of the GIT
*Mucosa
*Submucosa
*Muscularis externa
*Adventitia layer
State the 3 layers of mucosa.
*Epithelium
*Lamina propria
*Muscularis mucosae
Describe the basic structures found in the Epithelium.
EPITHELIUM:
It is simple columnar (Absorption/secretion) all over except in the oral cavity, pharynx, Oesophagus and the lower part of Anal canal where it is stratified squamous (protection).
- Numerous folds
- Crypts – At numerous places epithelium dips into the Lamina propria and form crypts (Simple tubular glands).
Villi:
In Small intestine, Mucosa bears numerous finger-like processes that project in the lumen.
Glands:
1. Unicellular secretory cells are scattered among the cells of the lining epithelium.
2. In some parts of GIT, compound tubulo-alveolar glands are present in the submucosa.
Describe the basic structure of lamina propria.
LAMINA PROPRIA:
- Made up of collagen and reticular fibres.
- contain blood capillaries, lymph vessels and nerves
- In SI, the core of villus is attached to the lamina propria.
- Prominent aggregation of lymphatic tissue is seen in Lamina propria (MALT-mucous associated lymphatic tissue)
Describe the basic structure of the muscularis mucosae. What is its function?
MUSCULARIS MUCOSAE
Thin layer of smooth muscle that separates lamina propria from the submucosa.
Usually, outer longitudinal and inner circular or at right angles to the lumen
- - Contraction of Muscularis Mucosa is important for the local mixing of intestinal contents
- It changes the shape of mucosa, that helps in absorption and secretion
Describe the submucosa.
This layer consists of loose areolar tissue that connects mucosa to the muscularis externa.
*Its looseness permits some mobility of mucosa over the muscularis externa.
*Contain numerous blood vessels, lymphatics and nerve fibers and Meissner’s plexus.
Describe the muscularis externa.
Name its 2 layers.
It consists of smooth muscles all over GIT except upper part of oesophagus which contain skeletal muscles.
Arranged in two layers
- Inner layer: Circular
- Outer layer: Longitudinal
(+ Oblique layer – in stomach only)
Between the two layers “Auerbach’s plexus (Myenteric plexus)” is present.
- Inner circular layer acts as sphincter at some parts. Eg: Pyloric sphincter, Internal anal sphincter, Ileo - caecal valve
Describe the serous layer/ adventitia layer.
*It is merely visceral peritoneum composed of connective tissue and simple squamous epithelium.
*The esophagus lies outside the abdominal cavity has a superficial layer called Adventitia which consists of areolar connective tissue
Describe the histology of the oral cavity.
*Epithelium?
*Specialized for what?
*Lamina propria?
*Muscularis mucosae?
*The oral cavity is specialized for taste, chewing, salivary secretion, and immune surveillance (tonsils).
*Oral mucosa varies from site to site
*Epithelium is non-keratinized stratified squamous (lining mucosa)
*Partially keratinized on gums and hard palate and on filiform papillae of tongue (masticatory mucosa)
*Special mucosa on tongue
*Lamina propria is unspecialized.
*A muscularis mucosae is not present.
Deep to the epithelial surface, minor salivary glands are common.
Describe the epithelium present in the following parts of the oral cavity.
*Hard palate
*Soft palate
*Tongue
*Upper epithelium is respiratory
Lower is stratified squamous keratinized (masticatory epithelium)
*The soft palate has a non-keratinized epithelium (lining epithelium), with underlying minor salivary glands and striated muscle. The largest tonsils (the palatine tonsils) are embedded in the sides of the soft palate.
This is the mucosa of the oropharyngeal aspect of the soft palate. It resembles the buccal and labial mucosa; the connective tissue papillae (A) are of moderate height and the stratified squamous epithelium is not keratinized.
*The mucosal surface of the tongue, specialized epithelial variations, including papillae of various shapes.
bulk of tongue has striated muscle fibers arranged in bundles along three mutually perpendicular axes,
Bundles of myelinated nerve fibers also present
Describe the 4 types of lingual papillae.
Which one does not have taste buds?
Which one has more taste buds?
1.*Filiform – most common – on dorsum of tongue – all over the tongue, elongated; keratinized no taste buds
*Fungiform – fewer, larger, rounded mushroom like, red dots – on dorsum of the tongue, have taste buds
*Foliate papillae – vertical ridges on the posterior lateral side of the tongue, have taste buds
*Circumvallate papillae – located just in front of sulcus terminalis; have taste buds (Von Edner’s glands, producing serous saliva situated at base of CV clefts)
2.Filiform papillae
3.Cicumvallate papillae
What are taste buds?
Describe the 3 cell layers found in the
What are taste cells called?
*A pore
Each gourd-shaped taste bud consists of three major cell types:
*Supporting cells – insulate the receptor
*Basal cells – dynamic stem cells
*Gustatory cells – taste cells
Describe the epithelium of the esophagus.
*Epithelium?
*muscularis mucosae?
*Submucosa
*Muscularis externa
*Esophagus has few functional specializations:
-Lined by non-keratinized stratified squamous epithelium.
muscularis mucosae is thicker than that in the stomach and intestine, and includes only longitudinal muscle fibers.
Distinct basic layers
lamina propria is less cellular (fewer lymphocytes) than that in the stomach and intestine.
Describe the muscularis externa of esophagus.
Describe the types of muscles on the upper, middle and lower 1/3 of the esophagus.
Arranged in two layers:
- Inner layer: Circular
- Outer layer: Longitudinal
* Between the two layers – Myenteric plexus of nerve fiber and ganglion cells are present. It controls peristaltic movement.
TYPES OF MUSCLES:
Upper 1/3rd – Skeletal muscle
Middle 1/3rd – Both skeletal and smooth muscle
Lower 1/3rd – purely smooth muscle
Describe the serous layer of the esophagus.
It consists of loose areolar connective tissue, which merges with the connective tissue of surrounding structures.
