1. Histology of digestive system oesophagus, stomach-fundus & pylorus
Dr. Makarchuk Iryna

2. mucosa
EPITHELIUM:
It is columnar (Absorption/secretion) all over except in the 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).

3. 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)

4. MUSCULARIS MUCOSAE
- Thin layer of smooth muscle that seperates lamina propria with the submucosa.
- Inner layer: Circular
- Outer layer: Longitudinal
- 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

5. 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 fibres and Meissner’s plexus.

6. MUSCULARIS EXTERNA
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
Between the two layers “Auerbach’s plexus (Myenteric plexus)” is present.
- Inner circular layer acts as sphincter. Eg: Pyloric sphincter, Internal anal sphincter, Ileo - caecal valve

7. Serosa /adventitial layer
It is merely visceral peritoneum composed of connective tissue and simple squamous epithelium.
The oesophagus lies outside the abdominal cavity has a superficial layer called Adventitia which consists of areolar connective tissue

8. OESOPHAGUS
It is a straight muscular tube extending from pharynx to the stomach in abdomen.
MUCOSA:
Epithelium: Non- Keratinised sratified squamous epithelium
Lamina Propria: Thin layer of loose CT.
Muscularis Mucosae:
- It is thicker than other parts of GIT
- It is single layer of longitudinally running smooth muscle fibres.

9. SUBMUCOSA:
- It is a wide layer of irregular, moderately dense connective tissue composed of bundles of collagen and elastic fibres.
- Due to elastic fibres mucosa is thrown into folds, hence lumen of oesophagus appears star shaped
- Contains blood vessels and branched tubulo- alveolar mucous glands

10. MUSCULARIS EXTERNA Arranged in two layers: - Inner layer: Circular
- Outer layer: Longitudinal
* Between the two layers – Myenteric plexus of nerve fibre 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

11. SEROSA / ADVEVTITIA
It consists of loose areolar connective tissue, which merges with the connective tissue of surrounding structures.

12. STOMACH
Stomach is a dilated segment of the digestive tract, that digest food and secrets hormone
There are three histological regions:
Cardia
Fundus and body
Pylorus
The fundus and body are identical in microscopic structure
The mucosa and submucosa of the undistended stomach lie in longitudinally directed folds known as rugae
When the stomach is filled with food, folds flatten out

13. Cardiac region of the stomach
Mucosa:
Epithelial lining at the cardio-oesophageal junction changes from stratified sq. to simple columnar epithelium
Presence of Mucous surface cells and cardiac glands
Submucosa:
Consists of Meissner’s plexus and blood vessels

14. Muscularis externa:
Inner – Oblique
Middle – circular
Outer – longitudinal
Myenteric plexus between muscle layers
Serosa – Simple squamous epithelium resting on a thin layer of connective tissue

15. Stomach - fundus Mucosa:
- Lining Epithelium – Simple columnar epithelium that invaginates to various extents into the lamina propria, forming gastric pits.
- These cells are involved in mucus secretion. The mucus protects the epithelial lining from damage due to the presence of acid in the stomach.

16. Stomach – fundus Lamina propria:
- Small tubular fundic/gastric glands are present.
- Types of cells:
i) Mucous neck cells – Located just below gastric pit.
- Columnar in shape
- Contain mucinogen granules in apical cytoplasm, while nuclei are basally situated basally.
- Produces soluble mucus

17. Parietal or oxyntic cells:
- They are large, ovoid or polyhedral cells with a large central nucleus.
- More numerous in the upper half of the gland than in the lower half
- Secretes HCL and intrinsic factor. Intrinsic factor combines with vitamin B12 to form a complex necessary for erythrocytes formation.

18. Chief or zymogenic cells:
- Located in the lower 1/3rd of gastric glands.
- Contain rough endoplasmic reticulum near the base, secretory granules near their apex and a small golgi apparatus.
- Secrete pepsinogen which is converted into pepsin in an acid environment.

19. Enteroendocrine and APUD cells:
- Located in the basal portion of gastric glands
- Secretes serotonin, histamine and gastrin. These are endocrine cells which release their products into the blood vessels.
MUSCULARIS MUCOSAE:
- It consists of two thin layer of smooth muscles.
i.e., Outer longitudinal and inner circular

20. SUBMUCOSA:
- Consists of blood vessels, lymphatic vessels and Meissner’s plexus.
MUSCULARIS EXTERNA:
Inner: Oblique
Middle: circular
Outer: Longitudinal
SEROSA:
Outermost layers of the stomach which consists of loose connective tissue covered by mesothelium

21. Difference between cardia, fundus & body, and pylorus
Contain cardiac gland
Contain gastric gland
Contain pyloric gland
Gastric pit less deeper than pyloric gland
Gastric pit more deeper than gastric or cardiac gland
Parietal cells absent or very few
Parietal cells more
Parietal cells few 21