Form and Function II Exam 1

Liver function

bile production, metabolism of fat (bile emulsifies fat), metabolizes vitamins, stores glycogen

Pancreas function

produces hormones and digestive enzymes

Duodenum function

main site of nutrient absorption

Hepatic vein path

hepatic vein runs through liver substance and drains into caudal vena cava

Gallbladder anatomy and function

function: store bile; bile is released from gallbladder only during a meal (in spp that don’t graze), and is convoluted to absorb H2O to concentrate bile

Blood supply to liver

Portal vein “supplies” nutrients to liver (most of blood volume), hepatic artery supplies oxygen to liver

Portal triad

portal vein, bile duct, hepatic artery (may have copies in each traid)

Where does blood exit liver lobule?

central vein (which is sublobar)

The liver acinus has…

oxygenation zones (due to hepatic artery dumping into portal vein —> “dilutes” oxygen and creates gradient) a brown pigment (lipofusin) accumulates in older cells nearer central v.

Gallbladder histology

simple columnar epithelium, no goblet cells; no muscularis mucosa, no submucosa; muscularis externa has 3 layers and is irregularly arranged (epithelial islands common!!)

Liver macrophages are called…

kupffer cells

Pancreatic islets are…

endocrine w/ rich capillary supply

Pancreatic exocrine tissue histology

acini (clusters of acinar cells) that produce digestive enzymes in that are inactivated and packaged in zymogen granules; acinar cells have pal, unwound nucleus

Sensory afferent input nerve types

somatosensory, special sensory

Motor efferent (e=exit), or output nerve types

somatic efferent (voluntary mm), visceral efferent =ANS (smooth muscles of glands, blood vessels, and organs)

ANS contains:

Sympathetic NS and Parasympathetic NS

Intermediolateral grey column contains

autonomic motor neurons that exit through ventral root and are distributed along vertebral column as the sympathetic trunk

Location of ANS structures in neck

Vagosympathetic formation (distal vagal ganglion, cr cervical sympathetic ganglion)

Location of ANS structures in thorax

Thorax: middle cervical ganglion, cervicothroacic ganglion, sympathetic trunk (ganglion chain)

Location of ANS structures in abdominopelvic cavity

celiacomesenteric ganglion/plexus (celiac and cranial mesenteric ganglion) caudal mesenteric ganglion, pelvic plexus

White rami

myelinated preganglionic axons from spinal cord to sympathetic trunk

Gray rami

unmyelinated post-ganglionic axons re-entering spinal nerves to reach sweat glands and blood vessels

Splanchnic nerve functions

innervates liver, spleen, stomach, and pancreas

controls GI motility, adrenal glands, metabolic regulation, and reproductive/urinary control

Parasympathetic nervous system function

energy conservation (anabolism), craniosacral outflow

Nerves in PSNS

cranial nerves (e.g. vagus nerve, CN X), sacral nerves (e.g. pelvic nerve)

Sympathetic nervous system function

energy consumption (catabolism), thoracolumbar outflow

Nerves in SNS

Thoracic sympathetic ganglion and greater splanchnic nerve, lumbar sympathetic nerves (splanchnic nerves); reach organs through periarterial nerve plexus (accompany blood vessels)

Ganglion definition

aggregation of cell bodies outside of CNS, act as relay station

Parasympathic ganglion are

formed in wall of organs (in body), or found on organs (in head/neck)

Sympathetic ganglion are found

close to vertebral column (and are visible)

SNS preganglionic release

ACh

SNS postganglionic axons release

catecholamines: epinephrine, norepinephrine

PSNS pre and post ganglionic axons release

ACh

SNS preganglionic fibers are

short

SNS post ganglionic fibers are

long

PSNS preganglionic fibers are

long

PSNS post ganglionic fibers are

short

Noradrenaline is a

neurotransmitter hormone

Noradrenaline is released into

blood stream and synapses (diffuse and rapid)

Noradrenaline is degraded in presynaps by

monoamine oxidase (MAO)

Noradrenaline is degraded in synaptic cleft by

catechol-O-methyl transferase (COMT)

ACh is a

neurotransmitter

ACh is released

at synapses (focused and slow acting)

ACh is cleared in synaptic cleft by

acetylcholinesterase (AChE)

SNS ________ energy

consumes, catabolism

PSNS __________ energy

conserves, anabolism

Vagus nerve (cranial outflow) contributes to

the pulmonary and enteric nervous system; is PrG PSNS

Pelvic nerve (sacral outflow) contribute to

pelvic plexus (preganglionic) and smooth muscular contraction; is PrG PSNS

Preganglionic SNS contains:

white rami communicants, splanchnic nerves

Post-ganglionic SNS contains

grey rami communicants, hypogastric nerve, vertebral nerve

Myenteric plexus (muscularis layer) contains

Vagus nerve and sympathetic fibers (SNS periarterial),

Myenteric plexus controls

GI secretion, blood flow, and visceromotor

Enteric nervous system neurotransmitters

Serotonin, dopamine, neuropeptide Y, and substance P

Submucosal plexus (Meissner’s plexus) contains

only PSNS

Submucosal (meissner’s) plexus controls

secretomotor structures around lumen

SNS actions in eyes

dilate pupils

PSNS action in eyes

constrict pupils

PSNS on glucose/glycogen production

decrease glucose, increase glycogen

SNS on glucose/glycogen production

increase glucose, decrease glycogen

PSNS on heart rate and blood vessels

Slow down heart rate, vasodilation, vagus n.

SNS on heart rate and blood vessels

increase heart rate, vasoconstriction, sympathetic trunk

SNS control of breathing

increase breathing rate, upper thoracic and cervical ganglia

PSNS on breathing

decrease breathing rate, relax bronchioles, vagus n,

PSNS on micturition

causes contraction of bladder and facilitates emptying, pelvic n.

SNS on micturition

increases capacity of bladder while sphincter is active, splanchnic nerves and hypogastric n.

PSNS on gastrointestinal secretion

facilitates GI secretior digestion and absorption, increases motility, vagus n.

SNS on gastrointestinal secretion

inhibits GI secretion and motility, splanchnic nn. through celiacomesenteric plexus

ligands and neurotransmitters

glutamate, GABA, dopamine, serotonin, ACh, glycine, epinephrine/norepinephrine, corticotropin-releasing hormone

neurotransmitter receptors

glutamate receptors, GABA receptors, dopamine receptors, serotonin receptors, CRF receptors, ACh receptors, glycine receptors

Regulation of neurotransmitters

Releasing enzymes that degrade the ligand, changing receptor conformation, internalizing receptors and recycling, releasing competing molecules with less signaling effect

ACh receptors (cholinergic receptors)

nicotinic (rapid) and muscarinic (long term, slower)

Location of ACh (cholinergic receptors)

pre and post ganglionic in PSNS and SNS

Nicotinic receptor

ACh binding opens ion channels (ionotropic), 5 sub-units for a pore, is mainly found in muscles and ganglia

Muscarinic receptor

ligand binding activates GPCR (M1: salivary glands/sweat glands decrease K+ conductance/excitatory effect; M2: Heart, increase K+ conductance and decrease Ca++, slows down heart; M3: in salivary glands, eye, internal urinary, sphincters, + GI tract)

AChE Inhibitor will

increase the synaptic persistence of ACh, leading to enhanced activity

Botulinum toxin

blocks vesicular release of ACh, blocks motor activity

Tubocurarine

blocks nicotinic receptors at neuromuscular junctions

Atropine

muscarinic receptor antagonist that causes oral thrush and urinary retention; treats glaucoma by opening venous drainage routes

Noradrenergic receptors

GPCRs post ganglionic in SNS, alpha 1, alpha 2, beta, have secondary messenger actions

Accessory GI organs

teeth, tongue, salivary glands, liver, gallbladder, pancreas

Alimentary canal/GI tract

oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine

wihtin the lumen of the GI tract, food is _____ into ________

digested (hydrolyzed) into monomers

First layers of GI tract (lumen to outer)

mucosa

Second layer of GI tract (lumen to outer)

Submucosa

Third layer of GI tract (lumen to outer)

Muscularis

Fourth layer of GI tract (lumen to outer)

serosa

GI motility

ingestion, mastication, deglutition (swallowing), peristalsis → movement of food through GI tract

GI secretion

endocrine (hormones) and exocrine (water, HCl, bicarb, and digestive enzymes)

GI digestion

breakdown of food into smaller subunits so it can be absorbed

Absorption

passage of digestive end products into blood or lymph

Storage and elimination

temporary storage and subsequent elimination of indigestible food

Regulators of GI system

nervous system, endocrine system, immune system, and smooth muscle motility

Submucosal (Meissner’s plexus) regulates…

secretion of Gi enzymes and blood flow

Myenteric (Auerbach’s) plexus

regulate GI movement

Mucosa layers

epithelium, lamina propria, muscularis mucosa

Muscularis propria layers

circular muscle, Auerbach’s (myenteric) plexus, longitudinal layer

First hormone discovered

Named secretin in 1905 (William Bayliss and Ernest Starling), stimulated pancreatic “juice” into duodenum

Second, third, fourth hormones discovered

Gastrin, cholecystokinin (CCK), gastric inhibitory peptide (GIP)

Largest lymphoid organ in body

GI tract

Ectoderm forms the…

extremes (mouth and anus)