Micro-Anatomy of Stomach, Small Intestine & Large Intestine

1. Micro-Anatomy of Stomach, Small Intestine & Large Intestine

2. The Stomach • Mucosa & Sub-mucosa – Simple Columnar Glandular epithelium • Mucosa contains gastric pits (known as cardiac & pyloric glands in the cardiac & pyloric areas respectfully) • Gastric pits are lined with the same columnar epithelium that divide and migrate upwards to replace the cells damaged by acid

3. Gastric Glands Contain: • Mucous Cells – Which produce a protective alkaline mucus • Regenerative stem cells – found in the base of the pit, replace gastric surface cells • Parietal Cells – Upper half of the gland, secrete HCL and intrinsic factor • Chief Cells – secrete pepsinogen • Enteroendocrine cells – secrete hormones that regulate digestion

4. Small Intestine • Contains Circular Folds in the Muscle Layers • Villi (Largest in duodenum, become smaller also intestinal tract) • Each villus is covered with mucus – secreting goblet cells and absorptive cells • Each villus contains an arteriole, a capillary network, a venule, a lymphatic capillary – lacteal

5. Small Intestine • Each villus has a fuzzy brush border of microvilli to increase absorption • Brush border enzymes are located here

6. Small Intestine • Intestinal crypts – floor of small intestine • Contain absorptive & goblet cells and dividing stem cells • Paneth cells also located in the crypt secrete lysozyme, phospholipase & defensins

7. Large Intestine • Consists of simple columnar epithelium • Except lower half of anal canal which his stratified squamous epithelium • There are no circular folds • There are no villi or microvilli • There are intestinal crypts – the only significant secretion is mucus