Digestive system Flashcards
function of the digestive system
digest food
absorb nutrients and h2o
immunological
4 main division and their responsibilities
esophogus : Conducts food from oral cavity to stomach
stomach: Fragmentation of food and Initiates digestion
small intestine : Digestion is completed and Main absorption occurs
LI:Water absorption to reduce liquid content of solids. A holding chamber for feces prior to defecation via the anal canal
4 Layers of the GI
Mucosa, submucosa, muscularis externa, adventitia
main components of the Mucosa
Lining Epithelium:Invaginates to form mucosal glands.
Submucosal glands.
Lamina Propria:Blood and lymph vessels and Loose connective tissue – lamina propria. Lymphoid cells and nodular tissue
Muscularis Mucosa:
Several layers of smooth muscle cells
Submucosa
Layer of dense irregular connective tissue supporting the mucosa.
muscularis extera : inner outer layer function
Inner circular layer contracts to reduce the size of the lumen.
The outer longitudinal layer contracts to shorten the tube.
Action of the two layers at right angles is the basis of peristaltic contraction.
ganglion of the muscularis externa
Parasympathetic ganglion cells in the muscularis externa, form Meisner’s and Auerbach’s plexus
where can skeletal muscle be found in GI tract
upper esophagus and anal sphincter
when is the adventia referred to as serosa ?
Outermost layer of connective tissue
When lined by mesothelium is referred to as serosa
muscularis externa of the esophagus types of tissue?
Skeletal muscle in upper third
Mixed in middle third
Smooth muscle in lower third
pyloric glands of the stomach
deeper pits than the cardia and fundus
glands are lined with mucous cells
parietal cells ?
secrete HCL and intrinsic factor
how do parietal cells increase in the secretion of HCl acid
Parasympathetic stimulation and the hormone gastrin leads to fusion of the tubulo-vesicles with the canaliculi, and an increase in the secretion of HCl acid
___ is a compound that increases the effects of the fusion of tubulo vesicles and canaliculi
histamine
Bicarbonate Secretion by Mucosal Epithelium
Bicarbonate is released by parietal
they enter fenestrated capillaries
diffuse across surface increasing pH
they buffer HCL and protect mucous cells
cheif cell function
sectete pepsinogen
mucous cells ?
secrete mucinogen to protect the epithelial lining of the stomach
enteroendocrine cells
secrete gastrin, gastric inhibitory peptide (GIP)
gastrin hormone?
produced by stomach
gastric acid secretion and stimulate HCL and insulin secretion , stimulate gastric motility and growth of mucosal cells
chloecystokin
produced by duodenum and jejunum
stimulate bile release from gallbladder, pancreatic enzyme secretion and pancreatic bicarbonate secretion
inhibits gastric emptying
secretin
produced by duodenum
insulin and pancreatic bicarbonate secretion
inhibit gastric acid secretion
Gastric inhibitory peptide
produced by Duodenum Jejunum
insulin release
inhibit Gastric acid secretion
4 degrees of folding that amplify total surface area of the SI
Plicae:evagination of the mucosa and submucosa
villi: evagination of the mucosa
glands or crypts of lieburkuhn
microvilli
how is gastric emptying controlled ?
by chloecystokin that acts on pyloric sphincter
• Paneth cells –
• Paneth cells – found in small intestine only; secrete defensins, lysozyme and TNF-alpha
• Peyer’s patches –
found in the ileum; lymphoid follicles with germinal centers lined by specialized antigen presenting M cells
Digestion & Absorption of Carbohydrates
in the Small Intestine ?
oligosaccharidases are present in brush bored and convert oligo and disacchardies to mono for absorption
SGLT-1
Used in carb digestion of SI
It is a Na+ dependent carrier that allow glucose and galactose to enter the enterocyte
Lacteals
are Involved in the Uptake & Transport of Lipoproteins and Chylomicrons
apoptosis of epithelial cells of SI occurs on
villi
crypts of lieburkuhn are responsible for ?
being one of 4 folding degrees and AND where mitosis od stem cells happen
Outer longitudinal layer of the muscularis externa of LIconverts to become ??
Outer longitudinal layer of the muscularis externa converts to become three (3) taeniae coli: longitudinal bands of smooth muscle
Main function of mucosa of LI is
Main function of mucosa is absorption of water, sodium,
vitamins and minerals
LI has no villi but has
crypts of Liebrukugn
most abundant lining cell in LI
goblet cells
crohn’s disease
Chronic inflammatory disease Affects entire gut wall; ulcerations and lymphoid infiltrates. Diarrhea, wasting, pain Granulomas can obstruct bowel Bowel can form fistulas or perforate
Ulcerative colitis
Ulcerative colitis is similar to crohn’s, only ulcers affect entire colon instead of just patches.
