The Digestive System Flashcards
What is digestion?
breakdown of food to a useful form that can be absorbed and used by cells
Whta can the products of digestion be used for?
creation of energy-cellular respiration, catabolism-production of ATP
repair/building-production of building blocks-anabolism
What are two main parts in the digestive system?
-alimentary canal
-accessory organs
List the key steps in the digestive system
1-ingestiong
2-propulsion
3-digestion (Mechanical,chemical)
4-absorption
5-defecation
Name the main components of saliva
-water -99%
-amylase
-lingual lipase
-antibodies
-lysozyme
-defensins
-friendly bacteria
What are the 4 layers of the GI tract wall?
-serosa
-muscularis
-submucosa
-mucosa
Describe the mucosa layer of the GI tract
-mucous membrane-protects,secretes,absorbs
-lamina propria-blood vessels,lymphoid tissue
-Muscularis mucosa-provides infoldings
Describe the muscular layer of the GI tract
-2 layers of smooth muscle-circular and longitudinal
-provides peristalsis and mixing
-onward movement regulated by sphincters
What empties secretions into the GI tract?
-salivary glands
-pancreas
-liver and biliary tract
Describe the submucosa layer of the GI tract
-loose connective tissue
-blood vessels
-nerves
-lymph vessels
-lymphoid tissue
Describe the adventitia/serosa layer of the GI tract
-outermost layer
-in abdomen= peritoneum barrier to spread of infection
-anchors GI tract
What is peristalsis?
the automatic wave-like movement of the muscles that line your GI tract
What is the myenteric (Auerbach’s) plexus?
-motor
-sympathetic and parasympathetic
What is the submucosal (meissner’s) plexus?
-secretmotor
-parasympathetic only
What is the function of the oesophagus?
-conveys food oropharynx-> stomach
-mucosa subject to friction
-thick projective stratified squamous epithelium
Describe the structure of the oesophagus and how it links to its function
passage of food facilitated by:
-flattening of mucosal folds
-loose and elastic submucosa
-mucous glands
muscularis externa
-upper 1/3 skeletal system-initiation of voluntary swallowing
-lower 2/3 smooth muscle only-peristalsis
Describe the structure and function of the stomach
-stores food
-mechanical, chemical brakdown
-extra layer in muscularis/oblique muscle
-highly secretory mucosa-HCl,pepsin,mucus
What kind of cells are in the stomach lining?
-simple columnar epithelial cells-all mucous gland cells
Describe the glands and cells of the stomach in the gastric pit
1-surface mucous cell
2-mucous neck cells-simple columnar, secrete acidic mucus
Describe the glands and cells of the stomach in the gastric gland
3-parietal cells-secrete HCl and intristic factor
4-chief cells-secrete pepsinogen,lipases
G cells-secrete gastrin
Whata re the 3 main components of the SI?
-duodenum
-jejunum
-ileum
Whats the overal function of the SI ?
-glands secrete intestinal juice
-completes chemical digestion
-absorption of nutrients
Name the cells in the SI and their function
-absorptive cells
-goblet cells-mucus
-intestinal crypt-crypt of lieberkuhn
-paneth cells-defensins lysozyme
-secretory cells-intestinal juice
-entero-endocrine cells-secrete cholecytokinin
Give some specialisations of the duodenum
-brunners gland
-secrete alkaline mucus
-neutralize chyme
-protect mucosa
-cholecystokinin production
Name some specialisations of the jejunum
-2nd section of SI
-main absorptive region
-glucose,vitamins,AA,fats
-very few brunners glands
-PH neutral to alkaline
-mucosal folds
-longest villi
Name some specialisations of the ileum
-distal part of SI
-peyers patches in lamina propria
-huge domes of lymphoid tissues
How is intestinal secretion controlled?
-stimulus for production-prescence of chyme in intestine
-secretin-stimulates liver cells to release bile and pancreatic secretion
-CCK-stimulates gallbladder contraction and pancreatic contraction
-1-2L intestinal juice
describe segmentation in the digestive system
non- adjacent segments of alimentary tract organs alternately contract and relax, moving food forward then backward. food mixing and slow propulsion occur
Name some main structures of the colon
-epiplotic appendage (fat filled pouch)
-teniae coli-bands of longitudinal smooth muscle
-haustra-pocket like sacs
Describe the internal structures of the colon
-thick mucosa-simple columnar epithelium
-many crypts-absorptive and goblet cells
-no circular folds
-no villi
-polypeptide YY-inhibits motility
Describe the bacteria flora in the colon
-10mil types
-synthesize vtamins B and K
-metabolize molecules-heparin and mucin
-ferment indigestible carbs-produce 500ml flatus daily
Name some main structures of the retum and anal canal
-anal canal-stratified squamous epithelium
-anal column
-external anal sphincter-voluntary
-rectal valve
-anal sinus-release mucus when compressed
-internal anal sphincter-involuntary
describe the defecation reflex
1-impulses from cerebral cortex-conscious control
2-voluntary motor nerve to external anal sphincter
3-external anal sphincter-skeletal muscles
stretch receptors in walls, sensory nerve fibres, internal anal sphincter-smooth muscle
Name the alimentary canal organs
-mouth
-pharynx (throat),
-esophagus,
- stomach,
- small intestine,
- large intestine,
- rectum, and anus.
Name the accessory organs
-teeth,
-tongue,
-glandular organs such as:
-salivary glands,
-liver,
-gallbladder,
-pancreas
What does gastrin do?
stimulates chief cells
What does CCK stimulate?
gallbladder contraction and pancreatic secretion
give two functions of the salivary glands
lysozyme kills bacteria
lubrication of food
what is chyme?
liquid food formed in the stomach by gastric juice
