digestive I

purpose of digestive system

provide nutrients, water, electrolytes, for energy production and cellular growth

function of digestive system

created optimal conditions for molecules to breakdown and absorb and transfers molecules from the external to the internal environment

key digestive structures

mouth and salivary glands, pharyx and esophagus, stomach, pancreas and liver, small and large intestine

mechanical breakdown of food

mastication

movement of food through muscular contractions

motility

types of motility

propulsive and mixing

pushing of contents along the digestive tract - speed is anatomy dependent

propulsive motility

movement that mixes food with digestive enzymes and brings monomers to absorbing surfaces

mixing motility

where does propulsive motility occur?

esophagus and small intestine

where does mixing motility occur?

stomach and large intestine

movement of digestive enzymes into the digestive tract

secretion

what glands are used for secretion?

exocrine glands

what do exocrine glands do?

secrete water, electrolytes, enzymes, bile, mucus, etc.

biochemical breakdown of food into monomer molecules

digestion

what does digestion do to carbohydrates?

poly/disaccharides become monosaccharides

what does digestion do to proteins?

breakdown into amino acids

what does digestion do to fats?

triglycerides become monoglycerides or fatty acids

movement of absorbable units/monomers from digestive tract into the blood

absorption

where does the majority of absorption occur?

small intestine

digestive tract

one continuous tract with each structure considered a separate organ with a specialized function/purpose

what is odd about the digestive tract?

is comes in contact with the external environment

accessory digestive organs

salivary glands, liver, gallbladder, pancreas, exocrine glands

necessary conditions for the digestive tract

high acidity and low pH, microbiome, enzymes for protein breakdown

protective surface that is a combination of secretion and reabsorption containing exocrine and endocrine glands and epithelium

mucosa

connective tissue that has a level of compliance and elasticity and helps regulate gut acidity

submucosa

smooth muscle that can change length and diameter and is key for propulsive and mixing movements

muscularis externa

regulates gut activity and works with submucosal plexus

myenteric plexus

outer connective tissue that releases fluid to prevent friction with surrounding organs

serosa

continuously generates borderline action potentials

slow wave potential

what does autonomous smooth muscle cause

peristalsis in the stomach, segmentation in the small intestine, and haustral contraction in the large contraction

what happens in the autonomous smooth muscle with food present?

fluctuations towards AP threshold with higher concentration chance

what happens in the autonomous smooth muscle with no food present?

fluctuates away from threshold with less contraction chance

network of nerve fibers in the digestive tract with localized self regulation

intrinsic nerve plexus

what is included in localized self regulation of the intrinsic nerve plexus?

digestive stretch receptors in the blood, sensory neurons, smooth muscle innervation, and exo/endocrine innervation

types of digestive stimuli

sensory neurons (self reg)

regulate digestive motility

smooth muscle innervation (self reg)

secretion of digestive chemicals and hormones

exo/endocrine innervation (self reg)

influences motility and secretion and can trigger intrinsic nerve plexus, GI hormones, smooth muscles, and glands through autonomic

extrinsic nerves

oversees and coordinates activity of several different digestive organs

vagus nerves

endocrine glands throughout digestive tract that release different hormones and can trigger inhibitory or excitatory action

gastrointestinal (GI) hormones

chemicals

chemoreceptors

stretching and tension

mechanoreceptors

fluid concentration

osmoreceptors