Special cells in Stomach,Small intestine

GASTRIC GLAND
It has 4 special types of cells

• Chief cells or zymogen cells

¤ secrete pepsinogen

¤ abundant in fundus of gastric gland

 •  Parietal or oxyntic cells

¤ secrete HCL and intrinsic factor of castle

¤ abundant in isthmus

 •  mucous cells

¤ secrete mucus

¤ abundant in neck

 • neuroendocrine cells

¤ G-cells : gastrin ;S-cells : somatostatin;enterochromaffin like cell : histamine

¤ present more deep in fundus

BRUNNER'S GLAND

 • characteristic of upper duodenum

 • secrete mucus

PANETH CELLS

 • Charecteristic of small intestine

 • granular,secretory,eosinophilic,exocrine cell

 • present deeply in crypts and unlike other cells dont migrate to surface of small intestine mucosa

 • life span is 28 days

 • contains zinc,lysosome,rough endoplasmic reticulum

 • secrete lysozyme,cryptidin,tnf a,phospholipase a2,antichymotrypsin

PAYERS PATCHES

 • characteristic of ileum

 • aggregates of lymphoid nodules

SPECIAL CELLS OF SMALL INTESTINE

 • mucosa of small intestine invaginates to form crypts of luberkuhn and evaginates yo form villi

• in villi :

1) goblet cells - secrete mucus and provides lubrication and barrier to infection

2) M cells (microfolds) - covers underlying lymphocytes,process antigens and present it to underlying lymphocytes

3) lymphocytes

• in crypts :

1) stem cells - replaces old dying cells in mucosa

2) paneth cells

3) neuroendocrine cells/APUD cells

NERVE INERVATION OF GIT

1) Auerbachs plexus/myentric

• between outer longitudinal muscle and inner circular muscle

• has motor control over git

2) Meissners plexus

• between circular muscle layer and mucosa

• has secretion control

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Development of Midgut

Progression of midgut occurs in following steps :

1. Primary intestinal loop formation
2. Physiological intestinal herniation
3. Rotation of midgut

Primary intestinal loop formation

• Midgut is suspended from dorsal abdominal wall.
• Apex of midgut is in contact with yolksac via VITELLO-INTESTINAL DUCT / YOLK STALK(remnant forms meckels diverticulum)
• Cephalic column of midgut - forms distal duodenum,jejunum,proximal illeum
• Caudal column of midgut - forms distal illeum,caecum,appendix,ascending colon,2/3rd transverse colon

Physiological intestinal hernia

• @ 4th week : rapid elongation of midgut occurs after suspension however abdominal cavity is not large enough to accumalate midgut so herniation of midgut occurs through umbilicus
• @ 6th week : retraction of herniated loops occurs because abdominal cavity has expanded along with regression of mesonephric kidneys and decrease liver growth all contributing to expansion og abdominap cavity
• Proximal Jejunum is first to enter back and lies on left side
• All other loops lie on right side
• Caecum temporarily lies in right hepatic region and gradually descends down to right iliac fossa.During its descend appendix is formed

Rotation of midgut

• Occurs around superior mesentric axis
• In anticlockwise direction
• ~270° = 90° during herniation + 180° during retraction of hernia

SIGNIFICANCE

1) Omphalocele

• Herniation of viscera through umbilical ring
• Due to failure of physiologically herniated intestinal retraction 
• Associated with chromosomal anomalies(50%),cardiac anomalies(50%),neural anomalies(40%)

2) Gastroschisis

• Herniation through abdominal wall and not through umbilicus
• Direct exposure to amniotic fluid causing damage to viscera

3) Vitellointestinal duct anomalies

• Meckels diverticulum-lies @ 40 to 60 cm proximal to ileocaecal junction,on antimesentric border
• Meckels cyst
• Meckels fistula

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