Small intestine - intestinal epithelium, inflammation of the intestine, celiac disease, malabsorption syndrome in chicken

small intestine

organ where digestion of proteins, fats, and carbohydrates is completed

the small intestine is mainly responsible for

• mixing food with digestive juices and bringing it into contact with intestine lining for absorption

• absorbs 90% of nutrients and water

• moves food further down gastrointestinal tract

structure of small intestine

• inside covered with intestinal epithelium 

  • increases surface area and increases absorption 

the small intestine is surrounded by 

two layers of smooth muscles 

contact in a wavelike pattern 

mixes content of small intestine and moves it towards large intestine

where are absorbed nutrients carried to

• the haptic portal vein

• leads to liver

intestinal epithelium

• single columnar epithelium

• tightly connected with cell junctions 

• folded into finger like projections call villi

villi in intestinal epithelium

contain blood and lymph vessels that distribute nutrients

key targets for pathogens 

inflammation of the small intestine

• epithelium of small intestine is constantly exposed to a range of microorganisms and foreign substances

The epithelium of the small intestine provides 

a physical and immunological barrier against exterior challenges 

the cells of the epithelium are 

constantly scanning the environment for antigens to be able to quickly react to pathogens 

lymphocytes in intestine 

• always present in intestine due to exposure 

• 6-40 lymphocytes per 100 epithelial cells 

what happens if an antigen is detected by a lymphocyte

• the immune cell sends out immunostimulators 

• a signaling cascade is initialized 

• more lymphocytes are recruited and they migrate into the inflamed tissue 

what do radical changes of the epithelial architecture lead to

• a decreased length of the villi 

• apoptosis of epithelial cells 

• enlarged crypts 

• decreased surface area of small intestine → decrease in absorption of nutrients 

what causes inflammation of small intestine 

food borne pathogens such as salmonella

autoimmune diseases such as coeliac disease 

Coeliac disease

• autoimmune disease triggered by gluten

• gluten is recognized as an antigen and triggers an immune response → inflammatory reaction 

if a person with coeliac disease continues to eat gluten, what will happen

the intestine remains chronically inflamed leading to shrinking of villi and a decrease in the surface area of the small intestine

symptoms of coeliac disease

• chronic constipation

• diarrhea 

• anemia 

• fatigue

• children fail to thrive 

malabsorption syndrom in chicken

• runting-stunting disease

• occurs in young chickens 

• leads to delay in growth and reduced productivity 

chickens infected with malabsorption syndrome can develop…

• enteric lesions

• intestinal inflammation

• dilation of crypts

  • these all lead to a reduction in absorptive surface area and leads to decreased nutrient uptake and reduced growth