Changing Function Through The GI Tract Flashcards
Phases of the GI tract
Ingestion Fragmentation Digestion Absorption Elimination
Basic layout and organisation of the GI tract
Hollow tube with regional, histological, functional differences
Mucosa
Submucosa
Muscularis propria (externa)
Adventitious/Serosa
Describe the mucosal layers
Specialised surface epithelium
On basal lamina
Lamina propria
-Loose connective tissue w blood and lymph vessels, nerve fibres and smooth muscle
Muscularis mucosae
- Thin double layer of smooth muscle
- Separates mucosa from submucosa
Describe the epithelium of the mucosa throughout the GI tract
Protective, squamous stratified
Secretory, columnar simple
Absorptive, brush border, columnar simple
Protective at the end
Describe the submucosa
Consists of loose connective tissue w
- Blood vessels
- Submucosal/Meissners plexus
- Leukocytes
- Varying amounts of adipocytes
Smooth muscle function
Muscularis mucosa
Local control of mucosa, to accommodate changes in the lumen contents
Gentle movements of mucosa to help expel contents of glands and agitation of luminal content
Smooth muscle function
Muscularis externa
Peristalsis along and out of GI tract
Inner circular layer, outer longitudinal layer
Smooth muscle function
Adventitia/serosa
Thin connective tissue layer continuous w surrounding organs
Serosa if more mobile
Bound by mesothelium (simple squamous)
Describe the epithelium found at the oesophagus
Stratified squamous
Physical protection, subject to mechanical abrasion
Kept moist by glandular secretions
Describe the function and the structure of the stomach
Mechanical, biological, chemical breakdown
3 muscularis externa layers, inner oblique, circular, longitudinal
Pepsin, HCl initiates biological/chemical breakdown
Simple columnar epithelial layer of mucous secreting cells
Invagination form gastric pits
Describe the structure of the gastric pits
Simple tubular glands
Insthmus, parietal cells
Neck, mucous cells, stem cells, parietal cells
Base, peptic, parietal, mucous, neuroendocrine cells found here
Secretions from the gastric pits and glands
Mucous Pepsin HCl IF Gastric
Function of stomach cells
Surface mucous cells
Mucous and HCO3-
-Protection from acidic, enzymatic properties of gastric juices and ingested foods
Function of stomach cells
Mucous neck cells
Line upper parts of gastric pits and secrete mucous
Function of the stomach cells
Stem cell
Divide every 3 days to regenerate cells
Function of the stomach cells
Chief cells/peptic/zymogenic cells
Lower regions of gastric glands
Release zymogen granules
Acidic environment activates pepsin
Function of the stomach cells
Parietal
Secrete HCl, IF
Has a central nucleus
Composition of the stomach mucosa in the pylorus
Deep pits, branching, filed
Mucous secreting
Gastrin secreting
Composition of the mucosa in the cardiac region of the stomach
Mainly mucous producing
Sparse
Composition of the mucosa in the body of the stomach
Gastric juices (acid+enzymes) Densely packed
Small intestine mucosa adaptations to increase SA for absorption
Site of terminal food digestion
Plicae cirularis, covered in villi
Epithelium, simple columnar w brush border
Lacteals take away chylomicrons
T and B cells in connective tissue, IgA secretion
Describe the structure of microvilli
Shape maintained by actin filaments, anchored to cell membrane via IF
Glycocalyx, glycoprotein, glycolipid projects from plasma membrane, protects from auto digestion
Types of epithelial cells found in the small intestine
Enter oysters Goblet, mucous secreting Paneth, release digestive enzymes, immunoglobulins, lysozomes Endocrine, hormone secretion Stem cells
Characteristic features of the duodenum
Characterised by submucosal mucus secreting Bruner glands
Characteristic features of the jejunum
Tallest villi, no Brunner glands, few lymphoid follicles
Characteristic features of the ileum
Aggregation of Peyer’s patches
Describe the mucosa found at the appendix
Mucosa heavily infiltrated with lymphocytes
Large colony of gut bacteria, restore gut flora
Describe the mucosa found at the colon
No villi
Columnar with microvilli and goblet cells
Goblet cells in mucosa
Outer longitudinal layer in 3 teniae coli
Describe the epithelium and the mucosa found at the anorectal junction
Sudden transition from simple columnar to stratified squamous
Branched, tubular anal glands, mucus secreting onto anal surface
Internal anal sphincter, smooth muscle
External anal sphincter, skeletal muscle
Describe the structure of the anal canal
Inner circular muscle thickens into the internal anal sphincter
Apocrine circumanal glands open onto skin around orifice
