Histology of SI and LI Flashcards
What are plicae circulares?
transverse folds with submucosal core that cannot lay flat if distended, visible in jeju less so in ileum
Where are intestinal villi found? What are they covered with?
mucosal folds that project into lumen and cover surface of SI
Simple columnar epithelium of enterocytes and goblet cells, core of loose CT with microvasculature and a lacteal
Describe the mucosa, submucosa, muscularis, and serosa of the small intestine
Mucosa= simple columnar epi with tubular intestinal glands, lamina propria and muscularis mucosae
Submucosa= dense irregular CT, neurovasculature lymphatics and glands
Muscularis= inner circular and outer longitudinal layers
Serosa= loose CT covered by visceral peritoneum
What is the structure of intestinal glands?
simple tubular glands lined by simple columnar, continuous with simple column that covers intestinal villi, open onto luminal surface of intestine at base of the villi
Where are enteroendocrine cells found? What do they secrete and regulate?
throughout intestinal glands
secrete peptide hormones to control gut motility
regulate secretion of enzymes HCL and bile, gastrin, secretin, GIP, motilin, CCK
Where are paneth cells found? What do they secrete?
pyramidal shaped cells at base of intestinal glands,
eosinophilic secretory granules secrete antimicrobial substances, regulate bacterial flora and part of innate immunity
What are microfold cells? Where are they located?
epithelial cells specialized for transepithelial transport of particles and microorganism
located in ileal mucosa overlying Peyer patches, pocket formed by deeply invaginated membrane and contain lymphocytes and macrophages
Where are intestinal stem sounds found? What is their job?
in niche at crypt base near Paneth
repopulate epithelial lining: daughter cells move out of crypts and differentiate into goblet enterocyte and enteroendocrine cells
What is the role of microfold cells?
apical surface expresses receptor for macromolecules and gram-negative bacteria which are internalized and transferred to immune cells
highly specialized antigen-transporting cells
What glands are found in the duodenum submucosa?
Brunner’s glands which are tubuloacinar mucous glands, produce alkaline secretion, neutralize acidic chime
What is the role of the hepatopancreatic ampulla in the duo?
Collect bile and pancreatic secretions
Does the jejunum have submucosal glands?
No but have villi
Describe the villi of the jejunum
Long finger like villi, tubular intestinal glands, villus core with well-developed lacteal for fat absorption
What is found in the ileum?
finger like villi (shorter than jeju)
Peyer’s patches of mucosal lymphoid modules specific to ileum
Paneth cells at base of intestinal glands
What abrupt transition occurs at the ileocecal junction?
villi of SI –> glandular epithelium of LI
What is critical to the function of the ileocecal vlave?
thickened extension of muscular mucosae which to limit reflux of colon into ileum
Does the large intestine have intestinal villi?
NO
What makes up the mucosa of the large intestine?
glandular simple columnar epi: colonocytes goblet cells stem cells and enteroendocrine, lamina propria and muscularis mucosae present, GALT extens
What makes up the submucosa of the LI?
dense irregular vascularized CT
What makes up the muscularis of the LI?
inner layer typical, outer long organized into taeniae coli which form haustra of LI
What parts of the colon have serosa?
intraperitoneal
What causes Hischprung’s Disease? What are the symptoms?
Aganglionsois in distal colon from mutations of RET required for migration and differentiaon of NNC failure of NCC development in both plexuses of bowel segment
Constipation, poor feeding, and progressive abdominal distention
What makes up the proper part of the rectum?
Upper part with typical mucosa of tubular intestinal glands and transverse rectal folds
What defines the canal/lower part of the rectum?
Anal columns with mucosal folds, anal sinuses aka depressions between columns, and anal glands that extend into submucosa and muscularis
What kind of glands are circumanal glands?
large apocrine glands surrounding anal orifice
What cells make up the colorectal zone of the anal canal?
simple columnar epi identical to rectum
What cell type does the anal canal transition to at the anal transition zone?
simple columnar –> stratified squamous of perianal skin
How does the internal anal sphincter form?
level of anus inner circular layer thicken
