GI exam #1 Flashcards
Purpose of the GI tract
to supply nutrients for use at the cellular level
- meet nutritional needs
- and eliminate waste
Process of the GI tract
1) ingestion
2) digestion
3) absorption
4) elimination
Ingestion
taking in food
-intake, chewing anddeglutition
digestion
molecules for absorption (into chyme)
absorption
transfer from GI tract to circulation
elimination
excretion of waste products of digestion
Components of GI tract
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus,
Accessory organs to GI tract
teeth, tongue, salivary glands, liver, gallbladder, pancreas
Mucosa
innermost layer of GI tract
- -Protects, secretes, absorbs
- —lumen/ small intestines: form folds “villi” and increase absortive capacity (surface area)
Submucosa
contains blood and lymph vessles
—transports nutrients
(connective tissue)
Muscularis (muscular) layer
Smooth muscle fibers arranged in circular and longitudinal groups.
—-motility
Serosa (serous) layer
outer covering
—protection
Peritoneum
lines walls of entire abdominal cavity. Forms the peritoneal cavity
Two folds of peritoneum
Mesentary and Omentum
Mesentary
blood and lymph
Omentum
fat covering for protection
Blood supply of GI tract
aorta–>celiac artery–> superior and inferior mesenteric arteries
–superior and inferior mesenteric arteries supply small and large intestine
—venous blood draiing GI tract empties into portal vein - carries nutrient rich blood to liver
(25-30% total caridac output is going directly to GI tract. increases after eating. more blood to transport nutrients)
Mucous
- from mouth to anus.
- protects and lubricates (only secretion in esophagus)
Digestive secretions
- enzymes, hormones, digestive juices, bile, pancreatic juices
- produced throughout GI w/ very specific functions
Peristalsis
wavelike movements
-stimulus is expansion of lumen of tract by food
Gastrocolic and duodenocolic reflex
leads to urge to poop after eating
particularly strong in the morning
Bacteria
normal component of GI tract. Essential for function. Major component of colon
-aids digestion (proteins) 10% of stool
Sympathetic
inhibits or decreases digestive actions. “slows down” S-S
Pararsympathetic impules
-increase GI activities “picks up”
P-P
Vagus nerve
cranial that innervates GI tract
Mouth
Oral or buccal cavity Functions: where digestion begins 1)mastication: mechanically reduces size of food particles and mixes with saliva. protects esphagus from trauma by decreasing size of particles 2) speech 3) expression 4) taste
Salivary Glands
parotid, submaxillary, sublingual
Salivary secretions
1000-1500 ml saliva produced daily
Amylase
begins digestion of starches
Pharynx
Nasopharynx, Oropharynx, laryngopharynx
- -pharyngeal muscles regulate swallowing
- -involuntary control
Act of swallowing (deglutition)
1) initiated voluntary (force food into pahrynx)
2) Involuntary (swallowing reflex)
3) transported by peristalsis to stomach
Esophagus
transports food to stomach
penetrates diaphragm thru esphageal hiatus
–no digestion, only mucous
Pharyngo-esophageal orn upper esophageal sphincter
allows food into esophagus
Gastro-esophageal or lower esophageal sphincter
allows food into the stomach
- -prevents acid reflux
- -between esophagus and stomach
How many seconds for food to pass into the stomach?
10 seconds
Stomach
- mixes food with gastric secretions
- -stores food until it can pass into small intestines
- empties content at rate which digestion can occur
Gastric secretions
chemical liquification of ingested food
Gastrin
stimulates secretions of parietal and chief cells
Parietal cells
secrete HCL and intrinsic factor
decrease HCL?
Chief cells
produce pepsinogen–>pepsin–>protein digestion
Mucous neck cells
secrete alkaline mucous to lubricate and protect stomach from self-digestion
pyloric glands
secretes mucous
pyloric sphincter
between stomach and duodenum
Gastric emptying
- controlled by nerve impulses, chyme, and hormonal effects
- fats and duodenal chyme (high acid)= activate the enterogastric reflex= inhibits gastric motility and secretion
- allows pancreatic juices time to neutralize in duodenum
Vagal stimulation….
increases emptying
Small intestine
- major site for digestion and absorption
- major nutrients absorbed
Villi
increase surface area and enhance absorption of nutrients
Duodenum and jejunum absorb….
carbohydrates, amino acids, lipids, iron, and calcium
Ileum absorbs…
water, electrolytes, bile salts, vitamins
How much water does the ileum absorb per day?
8 Liters
Large intestines
absorb water and electrolytes
and store feces until elimination
Mass movements
strong peristaltic actions occur when colon becomes filled
Haustra
when peristalsis breaks chyme into large pockets
–extracts water and chyme becomes solid feces
Rectum
storage and expulsion of food
–connects sigmoid colon and anus
Internal sphincter
- involuntary control.
- autonomic nerves makes area insensitive
External sphincter
- voluntary control
- somatic nerves make area very sensitive
Defecation reflex
feces move into rectum–>stretches and causes distention–> activates parasympathetic nervous system–> relaxes sphincters–> constricts muscles –> forces feces out
Chronic constipation
Occurs when defecation reflex is ignored or inhibited regularly
Major functions of the liver
- storage, protection, metabolism
- bile production and secretion
- carb metabolism
- protein metabolism
- formation of clotting factors
- fat metabolism
- vitamin and mineral storage
- filtration/detoxification
- blood storage
Kupffer cells
reticuloendothilial cells provide crucial filtering system
(part of the immune system)
—-phagocytically destroy old RBCs and remove bacteria from nlood
what supplies blood to the liver?
portal vein and hepatic artery
Portal vein supplies how much blood to the liver?
75%
Hepatic artery supplies…?
other 25% as oxygenated blood
Pancreas
- neutralizes acid chyme (lipase and amylase)
- –enters the duodenum via the pancreatic duct to the common bile duct
Acini cells
secrete pancreatic juices
Cholecystokinin-pancreozymin
food ingestion stimulates secretion stored bile in GB
Gallbladder
stores and concentrates bile made in the liver
Bile
emulsifies fats
Common bile duct
carries bile and empties into duodenum at ampulla of vater
Bilirubin
pigment derived from breakdown of hemoglobin
*main component of bile