Changes

Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticuluar groove (see [[Oesophageal Groove|oesophageal groove]]).

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assilimated directly, others continue down the digestive tract for further digestion. It mixes food and moves food forwards through the stomach chambers. Sensors in the rumen can determine the courseness of the food. Course, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.  

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.  

See [[Rumination - Anatomy & Physiology|rumination]] and [[Eructation - Anatomy & Physiology|eructation]].

See [[Rumination - Anatomy & Physiology|rumination]] and [[Eructation - Anatomy & Physiology|eructation]].

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions primarily mix food. There is a mixing cycle of the ruminoreticulum. There are 2 contractions of the [[Reticulum - Anatomy & Physiology|reticulum]] (2nd most powerful) which continues over the rumen. The ingesta flows from the [[Reticulum - Anatomy & Physiology|reticulum]] to the cranial ruminal sac to the [[Reticulum - Anatomy & Physiology|reticulum]] (or ventral sac). It occurs every 60 seconds. The secondary contraction lets gas out. (See [[Eructation - Anatomy & Physiology|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac to the dorsal sac ([[Eructation - Anatomy & Physiology|eructation]]) to the ventral sac.

The contractions have to main functions:

:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.  

 

:The secondary contraction lets gas out (see [[Eructation - Anatomy & Physiology|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

==Vasculature==

The rumen recieves blood from the '''cranial mesenteric artery''', '''celiac artery''' and '''right''' and '''left ruminal arteries'''.

The rumen receives blood from the '''cranial mesenteric artery''', '''celiac artery''' and '''right''' and '''left ruminal arteries'''.

==Innervation==

==Innervation==

==Lymphatics==

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

==Rumen Microbes==

The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are 2 thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliate or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

==Species Differences==

===Small Ruminats===

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

[[Category:Stomach - Anatomy & Physiology]]

[[Category:Stomach - Anatomy & Physiology]]

[[Category:To Do - Review]]

[[Category:A&P Done]]