Digestion Flashcards by Zara Jalil

what is digestive system made up of (2)

GIT and accessory digestive organs

How well did you know this?

Not at all

Perfectly

gastrointestinal tract (GIT)

alimentary canal = continuous tube from mouth to anus

How well did you know this?

Not at all

Perfectly

4 accessory digestive organs

salivary glands, pancreas, liver, gall bladder

How well did you know this?

Not at all

Perfectly

GIT general function

conveys food allowing it to be broken down into small molecules that can be absorbed

How well did you know this?

Not at all

Perfectly

6 stages of movement in GIT

ingestion
secretion
motility
digestion
absorption
defecation

How well did you know this?

Not at all

Perfectly

secretion

chemical breakdown by exocrine and endocrine glandular activity

How well did you know this?

Not at all

Perfectly

motility

muscular activity - propulsion and breakdown

How well did you know this?

Not at all

Perfectly

absorption

transfer to circulation

How well did you know this?

Not at all

Perfectly

GIT is an important contributor to …

homeostasis

How well did you know this?

Not at all

Perfectly

how does GIT contribute to homeostasis

breaks food down into absorbable molecules to provide nutrients to the body

How well did you know this?

Not at all

Perfectly

how efficient is GIT for absorbing the 3 food groups

99% carbs
95% fat
92% protein

How well did you know this?

Not at all

Perfectly

how are the propulsive, secretory and absorptive activities coordinated and integrated for high functional efficiency

neural and hormonal mechanisms

How well did you know this?

Not at all

Perfectly

GIT structure (2)

tubular nature, communication w external environment at both ends

How well did you know this?

Not at all

Perfectly

what type of space is the GIT lumen cavity

extracellular

How well did you know this?

Not at all

Perfectly

how long is GIT in living vs dead

4.5m in living (muscular tone)
10m in dead

How well did you know this?

Not at all

Perfectly

how many times bigger is GIT than human

How well did you know this?

Not at all

Perfectly

what is total internal SA of GIT and how many times larger is it than external SA

200-250m2 (600x larger)

How well did you know this?

Not at all

Perfectly

4 layers of GIT from out to in

serosa, muscularis externa, submucosa, mucosa

How well did you know this?

Not at all

Perfectly

serosa

thin, tough layer of connective tissue (continuous w peritineum in some places)

How well did you know this?

Not at all

Perfectly

what is muscularis externa made up of (2)

longitudinal and circular fibers

How well did you know this?

Not at all

Perfectly

longitudinal fiber contraction =

shorten GIT

How well did you know this?

Not at all

Perfectly

circular fiber contraction =

shrink lumen

How well did you know this?

Not at all

Perfectly

what type of muscle is the mouth, upper esophagus and anus

striated muscle

How well did you know this?

Not at all

Perfectly

what type of muscle is the rest of the GIT

smooth muscle

How well did you know this?

Not at all

Perfectly

submucosa

loose connective tissue containing lymphatics, blood vessels and neuronal network

3 components of mucosa

epithelial layer, lamina propria, muscularis mucosae

epithelial layer of mucosa

epithelial and glandular cells

lamina propria

loose connective tissue

muscularis mucosae

smooth muscle

enteric nervous system (ENS)

branch of ANS, neurons reside within GIT walls

2 features of ENS

independent and integrative

ENS functions

initiates, programs, regulates and coordinates activities of muscular, secretory and absorptive elements of GIT

plexus

collection of nerve cell bodies

name of plexus between muscularis mucosae and circular muscle

submucosa plexus

name of plexus between circular muscle and longitudinal muscle (aka inside muscularis externa)

myenteric plexus

how do the 2 plexuses function

anatomically distinct but behave as 1 functional unit (ENS)

what do the plexuses contain all the necessary elements for

reflex arcs

what are the 3 sensory neuron receptors in mucosa/muscle

stretch receptors, chemoreceptors, osmoreceptors

motor/effector neuron function (in nerve plexus)

activate sensory and muscle cells

interneuron function (in nerve plexus)

expand responses in GIT; allows for integration over longer distances

what does ENS consist of

ganglion cells and their processes which synapse w smooth muscle cells, endocrine, exocrine cells and other ganglion cells

short enteric reflex path (5)

- stimulus - sensory receptor (chemo, osmo, mechano) - nerve plexus (effector + interneuron) - smooth muscle / gland cell - response

excitatory ENS neurons

release ACh on muscarinic receptors

inhibitory ENS neurons

release NANC (nonadrenergic, noncholinergic) transmitters like NO

what are excitatory ENS neurons blocked by

atropine

where are ENS sensory fibers' cell bodies

in plexuses

where do ENS sensory gibers get info from (2)

gut chemoreceptors and mechanoreceptors

how does ANS synapse onto muscle

through ENS, never direct

parasympathetic (preganglionic) receptors and effect

nicotinic ACh receptors excitatory

sympathetic (postganglionic) receptors and effect

noradrenaline receptors inhibitory

autonomic innervation of parasympathetic nerves (2)

vagus X and pelvic nerves

autonomic innervation of sympathetic nerves (3)

celiac ganglion superior mesenteric ganglion inferior mesenteric ganglion

what do long reflexes modulate

short reflex activity (can excite/inhibit for excitatory and inhibtory enteric neurons) - e.g. excite inhibitory vs excite excitatory

what does parasympathetic input lead to

vasodilation

what does sympathetic input lead to

vasoconstriction

what is the majority of long reflexes

parasympathetic excitation of excitatory ENS neurons

what allows for long reflexes

sensory neurons

3 things to affect CNS

emotional state sight/smell/taste of food afferent neurons

GIT hormones function

regulate activities inside GIT (can also influence activities outside GIT)

diffuse endocrine system (DES) location & description

scattered among other cells in the mucosa; largest most diverse endocrine system in body

5 most important GIT hormones

gastrin, CCK, secretin, GIP, VIP

3 modes of hormonal regulation

autocrine, paracrine, endocrine

most common mode of hormonal regulation

endocrine

what type of hormones are most GIT regulatory hormones

peptides

pathway of GIT regulatory hormones (6)

mucosa hepatic portal vein liver heart systemic circulation target cells

liver function in GIT regulatory hormone pathway

filters toxins from gut before sending blood back to heart

targets of GIT regulatory hormones

multiple (inhibitory + excitatory)

how do GIT regulatory hormones interact w each other and with NTs (2)

synergistically and antagonistically

2 things that drive propulsion in GIT

pressure gradients and variations in resistance

what causes pressure gradients in GIT

coordinated contractions of muscular elements in GIT wall

how much resistance is there typically in GIT

little to none

circular muscles functions (2)

segmentation (mixing) and peristalsis (propulsion)

sphincters

closed at rest (increased resistance point) to prevent movement but open at right time for flow of food

3 GIT flow characteristics

slow aboral meets little/no resistance

deglutition

swallowing; tightly regulated so food does not move into nose/lungs

how many muscles involved in deglutition

~20

4 phases of deglutition

oral pharyngeal esophageal gastric

which of the 4 deglutition phases is voluntary

oral

pharynx function

conveys food from mouth to esophagus

esophagus function

transports food into stomach

what does esophagus functioning require

relaxation of upper and lower esophageal sphincters

oral deglutition phase

transport from mouth to pharynx

why is oral phase voluntary

you can choose to swallow, but once initiated, everything else is reflex

cortical center function

voluntary movements / ability to initiate

medullary center (other name + 2 functions)

deglutition center; involuntary reflexes and movement coordination (medulla oblongata)

bolus

masticated, insalivated mass of food

pharyngeal deglutition phase

transport from pharynx to esophagus

what 2 tracts cross in pharynx

respiratory and digestive

pharyngeal phase steps (6)

- bolux in pharynx - activates stretch receptors - reflexes move it downwards - presses on epiglottis to cover glottis (airways) - reflexive contraction of vocal cords - UES relaxes and pharyngeal muscle contracts = push bolus into esophagus

soft palate

closes off nose cavity