ruminant anatomy and physiology

anatomy of the rumen

-where relative to the cecum

-how does it connect to the oesophaus

how is it divided

• left hand side- putting a stethoscope by the paralumbar fossa, you can hear the rumen

• cecum is to the right

• 1st chamber after leaving the oesophagus

• connects to the oesophagus by the cardiac sphincter

• fissures (macroscopic invaginations into the lumen of the rumen) called pillars divide the rumen

• biggest fermentation chamber

rumen

function

layers

type of epithelium

• no gastric secretions

• fermentation and mechanical secretions

• papillae to increase surface area

• host bacteria for digestion of cellulose (no cellulase)

• non glandular stratified squamous epithelium, lamina propria, submucosa, muscularis interna

• layer of keratin for physical protection and thick tunica muscularis

regurgitation

• what contracts

• how is food drawn into the oesophagus

• where is the food moved into and how

• reticulum and dorsal sac of the rumen contract

• simultaenously the animal breathes in with a closed glottis reducing pressure in the thoracic cavity and the oesophagus

• increased rumen pressure and decreased oesophageal pressure draws food into the oesophagus

• it is moved into the oral cavity through antiperistaltic contraction

motility of the rumen

• what are ruminoreticular movements regulated by which nerve

• where do these fibers of the nerve originate

• what monitors what

• how is it stimulated

• reticuloruminal movements are centrally regulated by CNX (vagus nerve)

• dorsal vagal nucleus of the brainstem

• afferents from the lumen of the ruminoreticulum monitor distension, ingesta consistency, pH, VFA conc

• simulation through distention (stretch receptors), ingesta consistency, pH, VFA conc

primary and secondary movements of the rumen

• where does primary start

• what type of contraction and what order

• what does primary do

• primary frequency

• what type of ontraction is secondary and what does this do

• where does it start and where to

• secondary frequency

• where can secondary be assesed

primary

• contraction across the ruminal wall which starts at the reticulum- wave of contraction

• biphasic reticular contraction (2nd most powerful) followed by contraction of the dorsal then ventral sac

• mixes ingested food with microbes facilitating the production of VFAs which cross the rumen wall into the bloodstream

• some gases produce cannot cross the wall and must be expelled

• 1-3 x a min

• reticular contraction every 1 min

secondary

• caudal cranial wave of contraction pushes gas back to the oesophagus to be removed via the mouth

• starts in the caudalventral blind sac to dorsal

• approx once every 1-2 min

• can be assessed on paralumbar fossa

implication of CNX damage

• motility of the rumen is compromised

• gas accumulation as fermentation is still occuring

• bloating which expands the rumen wall limiting abdominal and diaphragmic contraction- affects breathing

which gases are absorbed by the ruminal wall after anaerobic digestion

VFAs

• propionate

• butyrate

• acetate

these produce energy when metabolised in the liver

anatomy of the reticulum

• which chamber

• which side and is it dorsal or ventral

• glandular or non glandular

• function

• 2nd chamber

• ventral left hand side

• close to rumen and oesophagus

• non glandular

• mechanical digestion and secretion

histology of the reticulum

• stratified squamous epithelium, lamina propria, lamina muscularis mucosae

• papillae arranged in a honeycomb structure

anatomy of the omasum including how it is connected to the reticulum

• 3rd chamber

• ventral right hand side

• connected to the reticulum through reticulo omasal orifice

• circular

• no gastric secretion

• have folds called omasal laminae for absorption of water and nutrients

anatomy of the abomasum

• last chamber

• chemical digestion

• glandular secretions

• similar to carnivores

• covered by gastric pits and ruggae

• has a lesser and greater curvature

• simple columnar epithelium

• have gastric pits which secrete hcl, mucus

• middle right hand side, close to omsum

• important in young for milk difestion

• greater and lesser omentum

blood supply to the stomach

• celiac artery to all of foregut (splenic, hepatic, gastric)

• splenic artery- spleen

• anastomosis

gastric groove

• gastric/reticular/oesophageal groove is present in newborn ruminants

• muscular channel taking milk from the oesophagus into the abomasum bypassing the rumen, reticulum and omasum

• composed of 2 layers of muscle

• when the animal is extending its neck to reach the mothers teat this triggers the groove to contract allowing milk to pass from the oesophagus into the abomasum where it is digesting by chemically

• can be used to administer oral antibiotics

pancreas

• next to duodenum

• exocrine and endocrine funcions

• enlarged in ruminants

• major and minor papilla

liver

• position

• always on ventral RHS

• 4 lobes

• big gall bladder

spleen

• LHS

• recieves blood from the splenic artery

• elongated

• falls on top of the rumen

abdominal musculature

• cutaneous trunk line

• external oblique

• internal oblique

• transverse abdominus and rectus abdominus

• abdominal muscles have a aperneurosis that forms the linea alba along the ventral midline

• thin muscular layer called the cutaneous trunk line which contracts to repel flies from the body

hardware disease- traumatic reticuloperitonitis

• animal ingests nails, wire

• reticulum is punctured

• ingesta and bacteria can leak into the peritoneal cavity

• peritonitis and adhesions in the abdomen

• can even lead to reticulopercarditis

issues arising after pregnancy

• enlarged uterus

• abdominal organs are compressed

• after giving birth uterus no longer enlarged creating empty space for organs to move around

• abomasum can move from to left or right- displaced abomasum

• gas gets entrapped inside abomasum and ifi it moves it cannot pass into intestine

• should adjust diet to prevent

longitudinal pillars

separate the dorsal sac from the ventral sac

cranial pillar

• separates the cranial sac (or ruminoreticular atrium) from the ventral sac

caudal pillar

divides the rear of the rumen into the caudoventral blind sac and caudodorsal blind sac

coronary pillars

• where is the origin

• what does it separate

originate from the caudal pillar and further separate the caudal blind sacs from the main dorsal and ventral sacs

where does water absorption occur in the omasum

base of the omasal laminae which do not contain a keratinised epithelium