Ruminoreticular motilities
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Transcript Ruminoreticular motilities
Isfahan University of Technology
Advance
Digestive Physiology
(part 4)
By: A. Riasi
(PhD in Animal Nutrition and Physiology)
Http://riasi.iut.ac.ir
Rumen and reticulum properties
◦ Rumen is divided into dorsal and ventral parts
by pillars.
◦ The dorsal part is divided into:
Cranial sac
Dorsal sac
Caudodorsal blind sac
Rumen and reticulum properties
◦ The ventral part of the rumen consist of:
The ventral sac
The caudoventral blind sac
Rumen and reticulum properties
◦ There are two separate components to rumen
development:
The first is the physical size of the organ.
The second aspect of rumen development is the
elongation of rumen papillae and thickening of
rumen walls.
Rumen and reticulum properties
◦ There are two separate components to rumen
development:
The first is the physical size of the organ.
The second aspect of rumen development is the
elongation of rumen papillae and thickening of
rumen walls.
Ruminoreticular wall structure
◦ The mucosal layer of the finger-like papillae
containing highly vascularized connective
tissue core.
◦ Epithelium is involved in the absorption of
short-chain fatty acids.
Ruminoreticular wall structure
◦ In the reticulum the mucosa contains
laminae
◦ On the surface of the laminae conical
projections called papillae.
◦ The stratified squamous epithelium also
absorbs short-chain fatty acids.
Ruminoreticular wall structure
◦ Contractions of the honeycomb cells, with
the purse-string action of the smooth muscle
strands, help the mechanical digestion.
◦ Myenteric plexus can be found between the
muscularis externa layers.
Innervations and the receptors
◦ The innervations of fore stomachs:
Vagal nerves (10:1 afferent/efferent ratio)
Splanchnic nerves (3:1 afferent/efferent ratio)
Innervations and the receptors
◦ The vagal nerves transmit sensory information
from two known kinds of sensory receptor:
Tension receptors
Epithelial/mucosal receptors
Innervations and the receptors
◦ The splanchnic nerves transmit sensory
information from serosal receptors and
possibly from tension receptors.
Ruminoreticular motilities
◦ The movements serve to:
Mix the ingesta
Aid in eructation of gas
Propel fluid and fermented foodstuffs into the
omasum.
◦ A cycle of contractions occurs 1 to 3 times per
minute.
Ruminoreticular motilities
◦ Two types of contractions are identified:
Primary contractions
Secondary contractions
Ruminoreticular motilities
• A typical primary cycle consists:
• Biphasic (double) contraction of the reticulum
• Caudally moving monophasic contraction of
the dorsal ruminal sac
• A contraction of the ventral ruminal sac
Ruminoreticular motilities
◦ Secondary cycle may occur and consist of
sequential contractions of:
The caudoventral ruminal blind sac
A cranially moving contraction of the caudodorsal
ruminal blind sac followed by the middorsal
ruminal sac
A contraction of the ventral sac.
Ruminoreticular motilities
Ruminoreticular motilities
Ruminoreticular motilities
◦ Ingesta enter the foestomach through the cardia.
◦ Heavy objects fall into the reticulum, while lighter
material enters the rumen proper.
◦ Added to this mixture are voluminous quantities of
gas produced during fermentation.
Ruminoreticular motilities
Ruminoreticular motilities
◦ Saliva, ingested water, and swallowed cud
join the soupy material in the reticulum.
◦ This flows in turn into the cranial sac and
then either back into the reticulum or on into
the dorsal and ventral sacs.
Ruminoreticular motilities
◦ The contraction of the ventral sac forces its
soupy fluid contents along the ventral and
cranial surfaces of the fibrous raft.
Ruminoreticular motilities
◦ The forestomachs possess a rich enteric
nervous
system,
but
coordinated
contractions require central input.
◦ Motility centers in the brainstem control
both the rate and strength of contraction
via vagal efferents.
Ruminoreticular motilities
◦ There are also vagal afferents from the
rumen to the motility centers which allow
stretch receptors and chemoreceptors in the
rumen to modulate contractility.
Ruminoreticular motilities
◦ Feeble intrinsic contractions responsible for
the smooth muscle tone in the forestomach
wall arise from nervous activity in its
intrinsic nerve networks.
Ruminoreticular motilities
◦ The gastric centers do not have spontaneous
activity and need to be driven by
Excitatory inputs
Inhibitory inputs
Ruminoreticular motilities
◦ The principal inputs to the gastric centers are
from the:
Forestomachs,
Abomasum, and
Duodenum by way of vagus nerves
Ruminoreticular motilities
◦ The known sensory receptor mechanisms are
responsible for the vagal inputs.
The tension receptors are located in the muscle
layer of different parts.
The epithelial receptors are located closed to the
basement membrane of the luminal epithelium of
the forestomachs.
Ruminoreticular motilities
◦ The
epithelial
receptors
in
the
forestomachs and the mucosal receptors in
the abomasum lie about 150 µm below the
luminal surface.
Ruminoreticular motilities
◦ Sustained epithelial receptor discharges are
also encountered in experimentally induced
"ruminal acidosis".
Ruminoreticular motilities
◦ Conditions inside the rumen can significantly
affect motility.
Acidic ruminal contents
High roughage diet