Anatomy and function of the rumen and stomach Flashcards
How does the oesophagus reach the stomach?
- Runs dorsal to the trachea and slightly on the LHS
- Then travels through the mediastinum and through the oesophageal hiatus of the diaphragm
Where is the cardiac sphincter?
Between the oesophagus and stomach
Rugae
Folds on the surface of the stomach that allow for stomach expansion and increase the surface area
In which species is a significant proportion of the stomach non-glandular?
Horse
What is the name of the main artery supplying the stomach?
Coeliac artery
Venous drainage of the stomach
Via the hepatic portal vein
What type of epithelium covers non-glandular stomach regions?
Stratified squamous epithelium (like the oral vavity and oesophagus)
What type of epithelium is found in glandular stomach?
Simple columnar epithelium
What are the 4 regions of the stomach?
- Cardia
- Fundus
- Corpus
- Pylorus
What does the enteric nervous system control?
- Motility
- Exocrine and endocrine secretions
- Microcirculation of the GI tract
- Regulating immune and inflammatory processes
Describe the pathway taken by ingesta through the forestomachs of ruminants
- Rumen (fermentation vet)
- Reticulum (part of rumen)
- Omasum (for water absorption)
- Abomasum (“true” stomach, analogous to the stomach of monogastrics)
What are ruminal papillae?
- Leaf-like projections from the rumen wall
- They increase the surface area for flora and absorption, allow for attachment of bacteria
Describe how the size of ruminal papillae changes and what this could indicate
- Size of papillae indicates quality of diet
- High quality, high roughage, correct pH = large and well-developed papillae
- They are poorly developed in the roof of the dorsal sac because this is where gas sits; well developed elsewhere as they are responsive to fibre in the immediate local vicinity
Feeding a high concentrate diet will have what effect on ruminal papillae?
High concentrate diet = reduction in papillae size
What is shown here?
Ruminal papillae
Describe the surface of the reticulum
- Hexagonal/polygonal shapes with smaller ridges inside
- These help catch stones, gravel and baler twine
What is shown here?
The reticulated surface of the reticulum
Describe the surface of the omasum
- Covered in laminae-like leaves, hanging curtains called conical papillae
- They are in distinct size groups
- Regular biphasic contractions squeeze material into the recesses, then a general contraction progresses fluid forward
What is shown here?
The conical papillae of the omasum.
What type of epithelium covers the abomasum?
Columnar epithelium
What is the pH of the abomasum?
pH 3-4
(It is diluted by large volumes of fluid from the forestomachs)
Recognise how the development of ruminal papillae in the rumen is related to diet
- Ruminal papillae vary in size and shape depending on age, diet and location
- High concentrations of VFAs (esp. butyric acid) promote growth, as does fibre
- The papillae take time to adapt to dietary changes
Describe the reticular groove reflex
- When stimulated by the vagus nerve, the groove contracts to form a closed tube
- This reflex is stimulated by suckling/pharyngeal stimulation and noises associated with the feeding routine
- When this happens, the edges of the groove curl up and create a tunnel between the oesophagus and reticulo-omasal orifice
Where does fluid go when the reticular groove is relaxed vs contracted?
- When the reticular groove is relaxed, the oesophagus empties into the reticulum/rumen
- When the reticular groove is contracted, the edges of the groove curl up and create a tunne; between the oesophagus and reticulo-omasal orifice
