Flashcards in Digestive system Deck (68)
- crystalline rods or prisms of calcium, phosphate and carbonate
- NO CELLS
- HARDEST tissue of the body
- no sensation
similar to bone, except cells (ODONTOBLASTS) occur in the nearby pulp, rather than scattered throughout
pulp of the tooth
- soft tissue
- blood vessels
calcified connective tissue covering the root
- collagen fibres linking the alveolar bone of the socket to the cementum
- rapid turnover
rounded columnar shape with TASTEBUDS
jagged edges, keep the mouth clean, no tastebuds
circular, with crevices which have TASTEBUDS on the sides and food and saliva can get in
3 salivary glands and what they secrete
- submandibular (mixed)
- sublingual (mucous)
- parotid (serous)
when is saliva secreted?
following parasympathetic stimulation by seeing, smelling, tasting, or thinking about food
water + mucous + enzymes
enzymes present in saliva
AMYLASE which breaks down starch and LYSOZYME which is antibacterial
4 ways of increasing surface area in the GI tract
- folds (circular and longitudinal)
- finger-like projections
- simple tubular glands
how is a steady rate of digestion maintained?
by storing food in the stomach and releasing some of its contents at intervals
what are the 4 tunics of the gut tube?
2. submucosa - blood, lymph, nerve
3. muscularis externa (external smooth muscle) - peristalsis
4. serosa - visceral peritoneum
what are the three layers of the mucous membrane (mucosa)?
1. epithelium (high turnover - for protection and absorption/secretion)
2. lamina propria - soft fibrous bed of loose connective tissue carrying nerves and blood and populated with defense cells, upon which the epithelium rests
3. muscularis mucosae - two layers of inner circular and outer longitudinal smooth muscle
chemical breakdown of ingested food into absorbable molecules
movement of nutrients, water, and electrolytes through the epithelial lining of the gut into blood or lymph
outer most surface of a structure, which is not in direct contact with the body cavity
Oesophagus is __cm long and travels, _________ to the trachea, from the _______ to the _________.
Oesophagus is _25_cm long and travels, _posterior_ to the trachea, from the _pharynx_ to the _stomach_.
functions of the oesophagus
- transport: 5s for food, 1s for liquid
- no absorption, little secretion, no digestion
how do the four layers of the gut tube differ in the oesophagus?
- epithelium: stratified squamous, sacrificial cells for protection against abrasion. renewed every 7 days
- external muscle: contains some skeletal muscle in the upper third, for rapid contraction and voluntary control of swallowing
- NO SEROSA - fibrous adventia instead
four regions of the stomach (from the oesophagus to the duodenum)
cardia - mucous
fundus - acid, enzymes, mucous
body - acid, enzymes, mucous
pylorus - mucous
how do the four layers of the gut tube differ in the stomach?
- epithelium: mucous-secreting cells plus gastric glands
- external muscle: three layers (not two) with an extra innermost OBLIQUE layer
function of gastric folds (rugae)
- allow expansion of stomach for food
- increase surface area
what controls the outlet of the stomach into the duodenum?
functions of the stomach
- secretion: acid, enzymes, mucous (2-3L per day)
- digestion: 20% total PROTEINS - pepsin
- absorption: water, ions, some drugs
- transport: mixing waves every 20s which produce CHYME
- protection: against its own secretions and microbes
how is pepsin secreted?
secreted as pepsinogen (inactive), so that it doesnt break down the stomach itself, then converted to the active pepsin form by the acid in the stomach