Histology and hormones of GI tract| Digestive system|Class-11 |Ashish sir
Channel: Todayxp Education
Date: 2020-05-22

Pancreatic juice contains two nucleases- ribonucleases and deoxyribonucleases. The nucleotides that result from the action of two nucleases are further digested by brush-border enzymes called nucleotidases and nucleosidases into pentose, phosphates and nitrogenous bases.
Gastro-intestinal (GI tract ) has following layers- Mucosa(innermost), sub-mucosa, muscle layer (circular and longitudinal muscles) and serosa.
Mucosa forms irregular folds (rugae) in the stomach and small finger like foldings called villi in the small intestine. The cells lining the villi produce numerous microscopic projections called microvilli giving a brush bordered appearance. Villi are supplied with a network of capillaries and a large lymph vessel called lacteal.
In duodenum, Brunner's glands are present. 
Meissner's plexus or sub-mucosal plexus are present in sub-mucosa as well as between sub-mucosa and circular muscles. It regulates secretion of digestive juices by intestinal glands.
Auerbach's plexus or Myenteric plexus are present between circular and longitudinal muscles. They regulate peristalsis.
Hormones of GI tract are gastrin, secretin, CCK-PZ, enterogastrone or GIP, motilin, enterocrinin, villikinin.

Peristalsis is involuntary wave of contraction which passes from oral to anal region and propels the food forward. Wave of peristalsis passes through stomach after every 20 seconds.
Segmental movements occur in intestine and propel the food in forward and backward direction.
Most of the absorption occurs in small intestine. Absorption of nutrients may be through passive, active or facilitated transport mechanisms.
The inflammation of intestinal tract is the most common ailment due to bacterial or viral infections.
1. Jaundice- The liver is affected in this disease. The skin, eyes turn yellowish.
2. Vomiting (Emesis) is the ejection of stomach contents through the mouth.
3. Diarrhoea-The abnormal frequency of bowel movement and increased liquidity of faecal discharge is known as diarrhoea.
4. Constipation- The faeces are retained within the rectum as the bowel movements occur irregularly.
5. Indigestion- In this condition, the food is not properly digested leading to a feeling of fullness.

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