Pathophysiology Exam 3 - GI (1)

GI functions (3)

1. movement of food through GI system

2. breakdown of food

3. absorption of nutrients from food

General function of GI layers

keep dangerous contents out of the blood (toxins/pathogens) AND keep blood contents from being lost into the gut

GI tract (pathway of food from mouth to anus)

mouth - esophagus - stomach - duodenum - jejunum - ileum - cecum/ascending colon - transverse colon - descending colon - sigmoid colon - rectum - anus

what is the first stop of major digestion?

stomach

rugae

provide the stomach with lots of surface area, allowing for lots of space for lots of food to be digested/absorbed

4 layers of the gut (inner to outer)

1. epithelial lining (mucosa)

2. submucosa

3. muscle layer (muscularis externa AND submucosal plexus)

4. peritoneum (visceral AND parietal)

which layer of the gut is the site of food breakdown and absorption?

epithelial lining

how is the epithelial lining layer of the gut protective?

it contains mucous, immune system elements, lymph nodes, and fat, protecting us from absorbing things we don't want to absorb

which layer of the gut contains blood vessels, nerves, and adipose tissue?

submucosa

which layer of the gut is site of the creation/releasing of enzymes to digest food?

submucosa

2 parts of the muscle layer of the gut

1. muscularis externa

2. submucosal plexus

muscular externa provides which type of MOVEMENT?

longitudinal

submucosal plexus provides which type of MOVEMENT?

circular

peritoneum is best described as what type of layer?

SEROSAL layer

2 types of peritoneum

1. visceral peritoneum

2. parietal peritoneum

visceral peritoneum

covers the ORGANS in the abdomen

parietal peritoneum

lines the ABDOMINAL WALL

peritoneal cavity

the space between the layers of the visceral and parietal membranes

what is the largest serous membrane in the body?

peritoneum!!

mesentery

an extension of the peritoneum that covers the SMALL INTESTINE

mesentery - holds what 3 things in place?

organs, nerves, and vessels (OVERALL, holds the small intestine in place)

omentum

an extension of the peritoneum that covers the STOMACH and COLON

how does absorption occur in the small intestine?

vessels of the mesentery are laying directly over the small intestine itself, allowing for absorption of materials into the gut

how does the omentum help contain infection?

contains enzymes and bacteria to control infection

which peritoneal extension protects the stomach/colon from the cold?

omentum

enteric nervous system (controls what?)

GI motility

cells of cajal

GI pacemaker cells (produce rhythmic/spontaneous membrane potentials, providing "slow waves" regular/normal activity)

myenteric plexus

provides longitudinal movement

submucosal plexus (3 functions)

1. secretion

2. absorption

3. segmental (circular) contractions

parasympathetic control of GI tract

INCREASES gut motility and secretions

sympathetic control of the GI tract

INHIBITS gut motility and secretions (REMEMBER: SNS response reduces amount of blood flow to the gut)

amount of secretions secreted into GI tract each day

7000cc

amount of secretions LOST in stool? why is this number low?

100-200cc (why? fluid is being reabsorbed into the colon)

salivary glands (3 characteristics/functions)

1. lubricate food in mouth

2. have antimicrobial properties

3. contain enzymes that begin the digestion of starch (such as pytalin and amylase)

what do MUCOUS secretions do in GI tract?

form an acid barrier

parietal cells (2 secretions)

1. HCL (digestion)

2. Intrinsic factor (helps absorb Vitamin B12)

chief cells (what it secretes? into where? for what purpose?)

pepsinogen into the stomach to breakdown proteins

what is pepsinogen converted into in order to digest proteins? how?

pepsin, due to interaction with gastric acids

oxyntic glands of the stomach (3 cells)

1. mucus cells

2. parietal/oxyntic cells

3. peptic/chief cells

brush border enzymes (secreted WHERE in the GI tract?)

DUODENUM

brush border enzymes (function)

breakdown carbohydrates

crypt of Lieberkühn

the lower part of the microvillus of the duodenum that is the site of cell reproduction

crypt of lieberkuhn - what happens to cells after they reproduce?

slowly make their way towards the top of the villus, where it must be recycled due to old age, and it will be extruded from their and get put into the lumen of the gut

how often are cells replaced in the microvilli (crypt of lieberkuhn)?

every 3-5 days

2 reasons why the duodenum is known for reabsorption?

1. LOTS of surface area

2. veins, arteries, and lacteals (lymph vessels) are located INSIDE the villus

why do the STOMACH and SMALL INTESTINE house very little species of microorganisms?

they contain such a harsh environment

when does colonization of microorganisms begin in the colon?

AT BIRTH!!

most organisms in the colon live on what? what does this mean?

live on fermentation of indigestible residue, meaning they really like fiber

Colon is a site for which 2 things?

1. vitamin synthesis

2. Ca+, Mg+, and Fe+ absorption

Colon - main function

reabsorb water/fluids that have been added to fecal matter so that it may be digested