GI System Flashcards
What is the difference between serosa and adventitia?
Serosa-mesothelium, associated with movement
Adventitia-relatively rigid and fixed
What are the three layers of mucosa in the digestive tract?
1-epithelium
2-lamina propria
3-muscularis mucosa (smooth muscle layer under lamina propria
What 3 things distinguish the submucosa?
1-dense irregular ct
2-large blood vessels
3-meissner sub mucosal enteric nerve plexus
What 3 things distinguish the muscular layer?
1-inner circular smooth muscle layer
2-outer longitudinal smooth muscle
3-auerbachs enteric plexus between the muscle layers
What are the three regions of the pharynx?
1-nasopharynx
2-oropharynx
3-laryngopharynx
What three layers make up the pharynx?
1-Mucosa
2-Muscularis externa (skeletal longitudinal and circular)
3-Adventitia
What is characteristic of the mucosa in the pharynx?
- SSQE
- lamina propria contains elastic fibers
- lack both muscularis mucosa and submucosa
What is the ratio of voluntary vs involuntary muscle in the esophagus?
Upper 1/3 voluntary
Lower 2/3 involuntary (middle third is somewhat mixed though)
What is the movement caused my alternating contraction called?
Peristalsis
How can you tell if a tissue is esophagus and not vagina?
Glands are found in the submucosa
The stratified squamous non keratinized epithelium of the esophagus transitions to what kind of epithelium in the stomach?
Simple columnar
What happens if the esophageal sphincter doesn’t close properly?
Heartburn. Repeated occurrence leads to esophagitis
Chronic esophagitis is called?
Gastro esophageal reflux disease (GERD) (10% of GERD results in Barrett esophagus)
What happens in Barrett esophagus?
Epithelium transitions to intestinal epithelium which is more unstable but more resistant to acid
What two main enzymes are secreted in the stomach?
Lipase
Pepsin
What three major mechanisms regulate digestive activities?
- Local factors
- Neural control mechanisms
- Hormonal control mechanisms
What 2 landmarks are found in the stomach mucosa?
Gastric pits
Gastric glands
What is characteristic of Cardia mucosal region?
- Pits are shorter than glands
- Glands are almost all mucous
What is characteristic of body and Fundus mucosal region?
Long glands with parietal and chief cells
What is characteristic of Pylorus mucosa
Region?
- mostly mucous glands
- pits are relatively longer
What are the 5 important cells of stomach epithelium?
1-surface mucous cell 2-mucous neck cell 3-parietal cell 4-chief cell 5-g cell (enteroendocrine)
What do enteroendocrine (DNES) cells secrete? 6 things
Gastrin Glucagon Gherlin Histamine Somatostatin Serotonin
What do parietal cells do?
Secrete 0.1 N HCl
Secrete gastric intrinsic factor
How does parietal cell acid secretion work?
HCO3 is transported out of cell in blood.
H+ and Cl- pumped out apically. These combine in lumen
What are the three phases of gastric secretory control?
Cephalic
Gastric
Intestinal
What do chief cells secrete?
Pepsinogen
Gastric lipase
They are found at the bottom of glands
How can you tell between parietal and chief cells?
Parietal are eosinophilic and fried eggish
What can form when the gastric mucosa
Is attacked and eroded?
Ulceration
What are the four general layers of the gut?
1-mucosa
2-submucosa
3-muscularis externa
4-serosa/adventitia
What does gastric intrinsic factor (GIF) help absorb?
B12
Loss of parietal cells leads to what?
Pernicious anemia (because of lack of B12)
What are he three gastric movements?
Propulsion
Grinding
Retropulsion
What are the two main functions of small
Intestine?
- complete the digestion process
- adsorption (90% of nutrients)
What are he three structural modifications of intestinal tissue that increase adsorptive area?
- plica circularis (3-fold)
- villi (10-fold)
- microvilli (20-fold)
What are plica circulares?
Permanent circular or semilunar folds of mucosa and submucosa
What are villi?
Dense covering of fingerlike projections
What do villi contain internally?
Lamina propria with microvasculature and lymphatics
What do villi contain externally?
Simple columnar epithelium with microvilli at the apical ends
What happens to villi in a person with celiac disease when they have gluten proteins present?
-they shrink or disappear resulting in malabsorption
What are enterocytes?
Absorptive columnar cells (microvilli at apical end)
What are the four important cells in the intestinal epithelium?
- enterocytes
- goblet cells
- paneth cells
- enteroendocrine cells
How are lipids absorbed into the blood from the digestive system through enterocytes?
- bile emulsifies into micelles
- gastric lipase breaks into glycerol,FA, monoglyceride
- diffuses across membrane
- resynthesize triglyceride in SER
- Golgi packs chylomicrons that end up in the lymphatic capillaries
How are disaccharides and dipeptides absorbed into the blood from the digestive system through enterocytes?
- disaccharidases and amino peptidases secreted by enterocytes break things down
- absorbed through active transport
- released to capillaries
What do goblet cells do?
Produce mucins to form mucous which protect and lubricate lining
What do paneth cells do?
- first line of defense
- release lysozyme, phospholipase A, defensins
What are intestinal crypts?
Paneth cell containing, short tubular glands with stem cells at the base
What four endocrine hormones do enteroendocrine cells secrete?
1-secretin (stimulates bicarbonate and water secretion in pancreas and bile duct)
2-CCK (signals satiety to brain)
3-GIP (stimulates insulin)
4-peptide YY (long term satiety)
What penetrates the core of each villus?
Loose CT
What are the three components of the lamina propria in a villus?
- arteries/veins
- lymphatic capillary
- smooth muscle
In the duodenum, what role do brunners glands play?
They are large bundles of mucous secreting glands
Where are plica circulares (valve of kerkring) best identified?
Jejunum
Where are peyers patches (lymphatic patches) found?
Ileum (increasing as you approach the rectum)
What do M cells do?
Endocytose antigens and present them to lymphocytes and dendritic cells to activate immune response
What controls the muscularis externa?
Myenteric plexus (auerbachs)
What controls the muscularis mucosa and DNES cells?
Submucosal plexus (meissners)
What are the three functions of the large intestine?
- absorb water and electrolytes
- storage of feces
- secrete bicarbonate and mucous
Characteristics of colon mucosa?
- lack villi
- penetrated by tubular intestinal glands
- goblet and absorptive cells (colonocytes)
How can you distinguish the anal canal junction in a slide?
Epithelium transitions from glands to SSQE non keratinized. Also the location of some anal cancers
What three disease arise from defects in intestinal tissue components?
- inflammatory bowel disease
- chrohns diseas
- ulcerative colitis
