Digestive system Flashcards
Name the four layers of the GI tract wall
Mucosa
Submucosa
Muscularis
Serosa
Outline the mucosa layer
Mucous membrane (epithelial cell layer)
Lamina propria ( connective tissue & GALT)
Muscularis mucosa (smooth muscle)
Outline the submucosa layer
Connective tissue containing nerves (submucosal plexus), blood vessels and glands
Outline the Muscularis layer
Circular and longitudinal layers of smooth muscle, nerves
Outline the serosa layer
Lubricating outer layer of connective tissue
Secretes serous fluid
Connects GI tract to other structures
Oral cavities (salivary secretions)
Where digestion begins
Moistens and lubricates food
Dissolves food
Forms a bolus (compact ball of food)
Antibacterial actions
Where is salvia produced from
Parotid salivary glands (25%)
Sublingual salivary glands (5%)
Submandibular salivary glands (70%)
Outline the oesophagus swallowing reflex
Tongue pushes food bolus into back of the mouth against soft palate, triggers swallowing reflex
Movement of bolus down oesophagus through relaxed upper oesophageal sphincter by peristaltic contraction of circular and longitudinal muscle layers
Passes through diaphragm and then lower oesophageal sphincter into stomach
What is peristalsis
Movement of digestion of a bolus, consistent through GI tract oesophagus, stomach and intestines by smooth muscles
Outline the functions of the stomach
Store up to 1L of food and liquid
Secrete hydrochloric acid, enzymes and mucus
Mechanical breakdown of injected food + secretions= chyme
Outline rugae
Deep folds that gradually relax as material enters permits 20-fold expansion in volume without increase in i tragasteis pressure (receptive relaxation)
Accommodates extra material entering without increasing pressure
Outline the small intestine
Continued digestion and absorption of nutrients
Cell surface-bound enzymes on intestinal wall
90% of nutrient absorption occurs in the small intestine
Name the three sections of the small intestine
Duodenum
Jejnum
Ileum
How is the small intestines surface area increased
Circular folds, villi and micro villi within duodenum and jejnum
Where does the duodenum receive secretions from
Recieves secretions from the liver gall bladder and pancreas
Liver releases bile, hepatocytes- hepatoduct to bile duct and pancreatic duct.
Function of bile
Aids the digestion and absorption of lipids through two processes
-emulsification
-formation of micelles
Outline the large intestine
Consists of cecum, ascending, transverse, descending, sigmoid colon and rectum
Sphincter protects small intestines from bacterial contamination and retrograde flow
Functions of the large intestine
Re absorption of water and salt from chyme
Storage, drying and compaction of faecal material prior to defecation
Outline the gut micro biome
More bacteria in gut than there are cells in the body
Ferment dietary fibre- fatty acids for absorption
Synthesise vitamins
Name the accessory organs
Liver
Gall bladder
Pancreas
Where is the fungus and what gland is in it
Top area of stomach
Oxyntic gland- release acid
Parietal cells- chief cells
Where is the antrum and what gland is in it
Bottom area of stomach
Pyloric gland area- release hormones into blood/capillaries
G cells- D cells
What is gastrin
A hormone that stimulates gastric acid secretion and motility, and so is released into mucosal blood vessels
Gastric acid function
Kills infested bacteria
Denatures proteins- particle breakdown
Converts pepsinogen to pepsin- protein digestion
Outline enteric system
Self regulate GI system- allow to change to local pH change quickly
Recieves input from sympathetic and parasympathetic systems aswell
Name the phases of regulation of gastric secretions and stomach emptying
Cephalic
Gastric
Intestinal
Outline the cephalic stage
Initiated by smell/taste, chewing
Prepares stomach for the arrival of nosh
Involves higher brain centres- vagus nerve, parasympathetic centre
Outline the gastric stage
Initiated as food arrives in stomach
Response to changes in pH, osmolarity and distension within stomach
Changes chemical environment and allows for stretch of the stomach
Outline the intestinal stage
Initiated in duodenum
Slow things down to enhance efficiency of absorption of nutrients within the small intestine due to acidity and controlled measure
Outline ghrelin
‘Hunger hormone’
Released from enteroendocrine cells within gastric glands, acts on hypothalamic arcuate nucleus to stimulate appetite, gastric secretions and motility
