digestive tract 1 Flashcards
layers of the digestive system (interior to exterior)
- mucosa
- submucosa
- muscularis externa
- adventitia
- mesentary
the mucosa of digestive system is
adjacent to the lumen
the submucosa of the digestive tract is
- made highly of distensible connective tissue
- contain Meissner plexuses
Meissner plexuses
- plexus of autonomic nerves innervating organs
- help with blood flow
muscularis externa
- consists of smooth muscle oriented in different directions
- inner-circular and outer longitudinal layers facilitates the movement of food involuntarily
adventitia (serosa) of digestive system
- secures organs to surrounding tissues
- fibrous connective tissue (serosa) in the peritoneal gap (gap between parietal and visceral layers) covers organs individually
- both covered by mesothelium for frictionless movement
mesentery of digestive system
- not really a layer
- attaches stomach, small intestine, pancreas, spleen, and most other abdominal digestive organs to the posterior wall of abdomen
- organs with this layer are intraperitoneal and those without are retroperitoneal
the digestive system includes the following structures/organs:
- oral cavity/teeth/tongue
- salivary glands
- pharynx
- esophagus
- stomach
- liver
- gall bladder
- pancreas
- large intestine
- small intestine
the digestive system helps with:
- propulsion
- secretion
- absorption
- excretion
- immunologic protection
- hormone production
the digestive system has 2 main parts:
- upper tract - initial phase (oral cavity, pharynx esophagus)
- lower tract (stomach, intestines, and anal canal)
the structures of the digestive tract allow the following:
- ingestion
- mastication
- motility
- secretion
- hormone release
- chemical digestion
- absorption
- elimination
the oral cavity
- has only mucosa and submucosa
- non-keratinized simple squamous epithelium on most of mucosa
- papillae on the tongue
- saliva enters invaginations of papilla and needs to be flushed
type of papillae on the tongue
- filaform
- fungiform
- foliate
- circumvallate (vallate)
filaform
- most abundant papillae
- no taste buds
- highly keratinized
fungiform
- mushroom shaped
- some taste buds
foliate
- rudimentary in humans
- on sides of tongue
circumvallate (vallate)
- have most taste buds
- innervated by the most sensory nerves
why is it important to have active salivary glands and brush your teeth?
- because saliva enters papillae and cleans out proliferation of bacteria in mouth
- if not cleaned it would carry lots of bacteria
Ebner’s gland
- minor salivary glands
- only produce serous fluids
- help flush oral cavity
- all other glands are mixed or mucosal glands
function of oral cavity
- food is chewed and broken down into bolus
- salivary amylase breaks down starch into glucose
tongue
- non keratinized
- papillae
- skeletal muscle
teeth
- enamel
- dentin
- pulp
- cementum
- gingiva
- periodontal ligament
esophagus
- has 3 layers
- non-keratinized stratified squamous epithelium in upper and middle thirds and becomes columnar toward lower third
- submucosal glands are larger than mucosal glands
layers of esophagus
- upper 1/3 = skeletal muscle
- middle 1/3 = skeletal and smooth muscle
- lower 1/3 = smooth muscle
innervation of the digestive tract
- enteric system
- has 2 subsections
- parasympathetic nerve fibers activate physiologic digestive process
- sympathetic nerve fibers are mainly inhibitory of digestive process
subsections of digestive tract
- myenteric plexus
- meissner plexus
myenteric plexus
- between inner and outer layers of smooth muscle
- regulates smooth muscle contraction
meissner plexus
- in submucosa
- regulates glandular secretion and blood flow
the stomach
- primary site of digestion of nutrients
- has 4 regions
- rugae
- glands secrete mucous, acid, digestive enzymes
4 regions of the stomach
- cardia
- fundus
- body
- pylorus
rugae
- the irregular folds of the inner lining of the stomach
- flatten out when stoamch expands
- simple columnar epithelium
glands of stomach
- pass through lamina propria
- cardiac glands are at esophageal orifice (mostly mucous secretion)
- gastric glands are in body and fundus (most developed and numerous, secrete mucous, acid and enzymes)
- pyloric glands (close to duodenum, mostly secrete mucous)
gastric pits
- shallow invaginations of the surface epithelium
- contain surface mucous cells
- highly alkaline (secrete carbonate)
- protect epithelial lining form low pH of stomach in lumen
gastric glands have 5 cell types:
- surface mucosa
- mucous neck cells
- parietal cells
- chief cells
- G cells
surface mucosa of gastric glands secrete
alkaline fluid (carbonate) to protect epithelium
mucous neck cells of gastric glands
- secretes acid (HCl) to reduce pH of stomach
- live and die quickly, replaced by stem cells that migrate to the neck of the gland from the base of the pit
parietal cells of gastric glands
- secretes intrinsic factor and HCl
- have receptors for gastrin
- controlled by ANS
- if damaged, no secretion of intrinsic factor = no vitamin B12 = subacute combined degeneration
chief cells of gastric glands
- secrete pepsinogen and gastric lipase
G cells of gastric glands
- secretes gastrin
- stimulates production of HCl by parietal cells
gastrin is secreted by
enteroendocrine cells
gastric glands are innervated by:
acetylcholine receptor (parasympathetic)
