1. GIT-3 RUMINANT
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2. Objectives
You should appreciate how the forestomach markedly differs in its histological structure from the abomasum - the glandular stomach.
You should appreciate the similarities and differences between the histological structures of rumen, reticulum and omasum.
You should appreciate the similarity of the ruminant glandular stomach with a non-ruminant animal like for example a dog.

3. 1- Abdomen - Sheep Cadaver in right lateral recumbency.
Left abdominal wall reflected cranially over ribcage.
Rumen & intestines in situ.
Note extent of rumen covered by ribcage.
Identify: dorsal & ventral sacs of rumen,
caudodorsal blind sac,
caudoventral blind sac,
caudal sulcus,
dorsal coronary sulcus,
ventral coronary sulcus,
ansa spiralis of ascending colon

4. 2- Abdomen - Sheep Identify: reticulum,
Sternum transected along midline,
ribs reflected craniolaterally.
Diaphragm partially reflected from
costochondral arch to expose left lung,
thymus, & heart within pericardium.
Identify: reticulum,
rumen,
abomasum,
spleen,
myotendinous junction of diaphragm,
left lung,
pericardium,
thymus.
Note proximity of reticulum to diaphragm and pericardium
- why is this of clinical significance?

5. 3 & 4 - Abdomen - Sheep
Diaphragm partially removed (cut edge apparent).
Pars caudalis of cranial lobe of left lung reflected dorsally. Pericardium partially removed to expose heart.
Identify: abomasum,
reticulum,
diaphragm,
spleen,
left ventricle,
right ventricle,
left interventicular paraconal sulcus,
apex of heart,
thymus.

6. Abdomen - Sheep
Cadaver in right lateral recumbency. Rumen reflected cranially to expose small & large intestine..
Identify: Jejenum, ansa spiralis of ascending colon (ansa proximalis, centripetal gyri, flexura centralis, centrifugal gyri).
Also visible: Greater omentum attached to rumen, left kidney.

7. Abdomen - Sheep
Cadaver in left lateral recumbency. Right abdominal wall reflected dorsally & ribcage removed. Left lobe of liver in situ, right liver lobe reflected cranially to expose visceral surface of left & right lobes, caudate process, gall bladder, bile duct, portal vein, & omasum.
Identify: Abomasum (greater & lesser curvatures), lesser omentum, sigmoid loop of duodenum, descending duodenum, ascending duodenum, pancreas, rumen & greater omentum, jejunum, caecum & ansa proximalis of ascending colon.
Also visible: right kidney (note relationship to liver), right lung. Yellow staining of greater omentum is post-mortem artefact resulting from leakage of bile through gall bladder wall.

8. SLIDE 35 Rumen
In the ruminant the forestomach consists of the rumen, the reticulum and the omasum.
Shown below: a low magnification view of the rumen.
1.0 mm

9. SLIDE 35 Rumen
In the ruminant the forestomach consists of the rumen, the reticulum and the omasum.
Shown below: a low magnification view of the rumen.
Area of rumen selected.
1.0 mm

10. SLIDE 35 Rumen Identify: papillae
mucosal layer (epithelium and lamina propria)
submucosa
tunica muscularis
serosa
1.0 mm

11. SLIDE 35 Rumen Identify: papillae
mucosal layer (epithelium and lamina propria)
submucosa
tunica muscularis
serosa
papilla
mucosa
submucosa
(extends into the large papillae)
tunica muscularis
serosa
1.0 mm

12. SLIDE 35 Rumen
The tunica muscularis comprises a thick layer in the rumen (smooth muscle).
An inner circular layer and an outer longitudinal layer are clearly defined.
250 µm

13. SLIDE 35 Rumen
The tunica muscularis comprises a thick layer in the rumen (smooth muscle).
An inner circular layer and an outer longitudinal layer are clearly defined.
submucosa
tunica
muscularis
inner layer
outer layer
serosa
250 µm

14. Can you see the boundary between mucosal and submucosal layers?
SLIDE 35 Rumen
Can you see the boundary between mucosal and submucosal layers?
100 µm
250 µm

15. SLIDE 35 Rumen
Can you see the boundary between mucosal and submucosal layers?
No, because of the absence of the lamina muscularis. E L S T
E : epithelium (mucosa)
L : lamina propria (mucosa)
S : submucosa (with blood vessels)
T : tunica muscularis
100 µm
250 µm

16. SLIDE 35 Rumen What type of epithelium covers the surface?
Rumen - Sheep
Rumen wall incised and reflected cranially to show papillated, non-glandular mucosa & rumenal pillar. Serosal surface of rumen and spleen also apparent.
Compare mucosa with that of reticulum, omasum & abomasum elsewhere in series.
Note consistency of rumenal ingesta and compare with that of reticulum, omasum
& abomasum elsehere in series.
250 µm

17. SLIDE 35 Rumen What type of epithelium covers the surface?
Keratinised stratified squamous epithelium.
keratinised surface
epithelium
keratinised stratified
squamous
lamina propria
submucosa
tunica muscularis
250 µm

18. Why is it the most appropriate covering here?
SLIDE 35 Rumen
Why is it the most appropriate covering here?
50 µm

19. SLIDE 35 Rumen Why is it the most appropriate covering here?
1. Because it breaks down the roughage in the food.
2. Protects the lining from damage.
keratinised surface layer
stratified squamous
epithelium
lamina propria
50 µm

20. Would you expect to see any glands here?
SLIDE 35 Rumen
Would you expect to see any glands here?
100 µm

21. Would you expect to see any glands here? No.
SLIDE 35 Rumen
Would you expect to see any glands here?
No.
epithelium
lamina propria
lumen
blood vessel
submucosa
100 µm

22. SLIDE 36 Reticulum
Identify: papillae mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
serosa
2.0 mm

23. SLIDE 36 Reticulum
Identify: papillae mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
serosa
papillae (primary reticular folds)
mucosa
submucosa
tunica muscularis
serosa
(indistinct)
2.0 mm

24. SLIDE 36 Reticulum
Identify: papillae mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
Reticulum - Sheep
▪ Reticulum in situ. Reticulum wall incised and reflected
cranially to expose mucosa.
▪ Note consistency of reticulum ingesta
▪ Also visible: diaphragm (cut edge), left lung, heart,
thymus, liver.
1.0 mm

25. SLIDE 36 Reticulum
Identify: papillae mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
epithelium
papilla
lamina muscularis
lamina propria
connective tissue band between
lamina propria and submucosa
conical papillae
submucosa with blood vessels
extending into papilla
lamina propria
inner layer of tunica muscularis
1.0 mm

26. SLIDE 36 Reticulum In this area of primary papilla secondary papillae.
identify: epithelium, lamina propria and lamina muscularis,
part of submucosa extending into papilla.
0.5 mm

27. SLIDE 36 Reticulum In this area of primary papilla secondary papillae.
identify: epithelium, lamina propria and lamina muscularis,
part of submucosa extending into papilla.
LM : lamina muscularis
S : submucosa LM
epithelium
lamina propria
secondary papilla S
band of connective tissue
0.5 mm

28. How would you describe the lamina muscularis here?
SLIDE 36 Reticulum
How would you describe the lamina muscularis here?
0.5 mm
100 µm

29. SLIDE 36 Reticulum How would you describe the lamina muscularis here?
Seen as blocks of (smooth) muscle; isolated in both short and tall folds.
LM : lamina muscularis
lamina propria LM
epithelium LM
0.5 mm
100 µm

30. SLIDE 36 Reticulum
The tunica muscularis consists of two thick layers of smooth muscle.
With inner circular and outer longitudinal layers.
The appearance of muscle tissue on slides depends on how the sample has been cut for histology (longitudinal, transverse or oblique sections).
1.0 mm

31. SLIDE 36 Reticulum
The tunica muscularis consists of two thick layers of smooth muscle.
With inner circular and outer longitudinal layers.
The appearance of muscle tissue on slides depends on how the sample has been cut for histology (longitudinal, transverse or oblique sections).
S : submucosa with blood vessels S
mucosa
inner layer of tunica muscularis
outer layer of tunica muscularis
thin layer of serosa
1.0 mm

32. What are secondary papillae?
SLIDE 36 Reticulum
What are secondary papillae?
1.0 mm
250 µm

33. SLIDE 36 Reticulum What are secondary papillae?
They are conical papillae projecting from the mucosa on the crests of folds and from the compartments between primary papillae.
secondary papillae
primary papilla or lamina
1.0 mm
250 µm

34. How is the mucosal layer divided into compartments here?
SLIDE 36 Reticulum
How is the mucosal layer divided into compartments here?
1.0 mm
250 µm

35. SLIDE 36 Reticulum
How is the mucosal layer divided into compartments here?
It forms a honeycomb of intersecting short and tall folds.
LP : lamina propria
S : submucosa
T : tunica muscularis
B : blood vessel
fold (primary papilla) LP S B B T S T
1.0 mm
250 µm

36. What type of epithelial lining is present?
SLIDE 36 Reticulum
What type of epithelial lining is present?
50 µm

37. SLIDE 36 Reticulum What type of epithelial lining is present?
Keratinised stratified squamous epithelium.
lamina muscularis
lamina propria
stratified squamous epithelium
keratinised layer
50 µm

38. SLIDE 37 Omasum Identify: laminae
mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
serosa
2.0 mm

39. SLIDE 37 Omasum Identify: laminae
mucosal layer (epithelium, lamina propria, lamina muscularis)
submucosa
tunica muscularis
serosa
laminae (extend like pages of a book)
submucosa arrowed
mucosal layer
(see higher
magnifications)
2.0 mm
serosa
tunica muscularis

40. SLIDE 37 Omasum Identify : laminae. mucosal layers 1. epithelium
2. lamina propria
3. lamina muscularis
extension of tunica muscularis
Omasum - Sheep
▪ Cadaver in right lateral recumbency.
Omasum in situ.
Wall incised to expose mucosa &
omasal laminae.
▪ Note consistency of omasal ingesta.
▪ Also partially visible: Liver (reflected caudally),
abomasum & greater omemtum.
0.5 mm

41. SLIDE 37 Omasum Identify : laminae. mucosal layers 1. epithelium
2. lamina propria
3. lamina muscularis
extension of tunica muscularis
LM : lamina muscularis
LP : lamina propria
laminae LP
epithelium LM LM
part of tunica muscularis LP
0.5 mm

42. How many layers of smooth muscle do you see within each lamina?
SLIDE 37 Omasum
How many layers of smooth muscle do you see within each lamina?
250 µm

43. How many layers of smooth muscle do you see within each lamina? Three.
SLIDE 37 Omasum
How many layers of smooth muscle do you see within each lamina?
Three.
smooth muscle layers
LP : lamina propria 1 2 3 LP
epithelium LP
250 µm

44. To which muscle layers do they belong?
SLIDE 37 Omasum
To which muscle layers do they belong?
100 µm

45. SLIDE 37 Omasum To which muscle layers do they belong?
Outer layers are the lamina muscularis.
The inner layer is the tunica muscularis.
LM : lamina muscularis
TM : tunica muscularis
LP : lamina propria LM TM LM LP
epithelium LP
100 µm

46. SLIDE 37 Omasum Outer layers are the lamina muscularis.
The inner layer extends from the tunica muscularis.
1.0 mm
250 µm

47. SLIDE 37 Omasum Outer layers are the lamina muscularis.
The inner layer extends from the tunica muscularis. TM LM LP LM LP
epithelium
LM : lamina muscularis
TM : tunica muscularis
LP : lamina propria
1.0 mm TM
250 µm

48. What is the epithelium type?
SLIDE 37 Omasum
What is the epithelium type?
100 µm

49. SLIDE 37 Omasum What is the epithelium type?
Keratinised stratified squamous epithelium.
E : epithelium
LM : lamina muscularis
LP : lamina propria
TM : tunica muscularis LM TM LP E
lumen
100 µm

50. Keratinised stratified squamous epithelium of omasum.
SLIDE 37 Omasum
Keratinised stratified squamous epithelium of omasum.
50 µm

51. Keratinised stratified squamous epithelium of omasum.
SLIDE 37 Omasum
Keratinised stratified squamous epithelium of omasum.
lamina muscularis
lamina propria
keratinised stratified
squamous epithelium
keratinised surface
50 µm

52. Abdomen - Sheep Cadaver in left lateral recumbency.
Right abdominal wall reflected dorsally & ribcage removed.
Duodenum pulled dorsally with forceps to highlight pylorus.
Identify: Abomasum & greater omentum, rumen, left & right lobes of liver, gall bladder, duodenum, pancreas, jejunum.
Also visible: right kidney (note relationship to left lobe & caudate process of liver), right lung, apex of heart, remains of diaphragm

53. SLIDE 38 Abomasum (glandular stomach)
Abomasum - Sheep
▪ Abomasal wall incised and reflected to expose mucosa
▪ Rumen & omasum also opened
▪ Compare mucosae to that of abomasum
▪ Compare texture of ingesta in each compartment
2.0 mm

54. SLIDE 38 Abomasum (glandular stomach)
Select an area of the abomasum.
2.0 mm

55. SLIDE 38 Abomasum (glandular stomach)
Identify the main regions in the wall of the abomasum.
1.0 mm

56. SLIDE 38 Abomasum (glandular stomach)
Identify the main regions in the wall of the abomasum.
mucosa : epithelium,lamina propria with glands
and lamina muscularis
submucosa : extends into ‘folds’
tunica muscularis
serosa
1.0 mm

57. SLIDE 38 Abomasum (glandular stomach)
Submucosa:
The submucosa consists of loose connective tissue with unilocular adipocytes and many blood vessels.
250 µm
100 µm

58. SLIDE 38 Abomasum (glandular stomach)
Submucosa:
The submucosa consists of loose connective tissue with unilocular adipocytes and many blood vessels. LM V
submucosa
adipocytes A TM
LM : lamina muscularis
TM : tunica muscularis
A : arteriole
V : venule
250 µm
100 µm

59. SLIDE 38 Abomasum (glandular stomach)
What is the epithelium type here?
50 µm

60. SLIDE 38 Abomasum (glandular stomach)
What is the epithelium type here?
Simple columnar, secretory epithelium.
columnar epithelium
G : gastric pits
LP : lamina propria G
lumen G LP
mucosal glands LP
50 µm

61. SLIDE 38 Abomasum (glandular stomach)
Why is this sudden change?
columnar epithelium
G : gastric pits
LP : lamina propria G
lumen G LP
mucosal glands LP
50 µm

62. SLIDE 38 Abomasum (glandular stomach)
Why is this sudden change?
Requirement for digestion in this region.
columnar epithelium
G : gastric pits
LP : lamina propria G
lumen G LP
mucosal glands LP
50 µm

63. SLIDE 38 Abomasum (glandular stomach)
Which tissue layers here differ from the forestomach the most and why?
250 µm

64. SLIDE 38 Abomasum (glandular stomach)
Which tissue layers here differ from the forestomach the most and why?
The mucosal layer is most altered because of the requirement for digestion whereas it was mainly mechanical breakdown in the forestomach.
E : epithelium
LP : lamina propria
with tubular
mucosal glands
LM : lamina muscularis
S : submucosa
TM : tunica muscularis E LP S LM TM
250 µm

65. SLIDE 38 Abomasum (glandular stomach)
Glandular area of mucosa (lamina propria) with underlying smooth muscle of the lamina muscularis.
Deeper to this is the submucosa in which some blood vessels are visible.
50 µm

66. SLIDE 38 Abomasum (glandular stomach)
Glandular area of mucosa (lamina propria) with underlying smooth muscle of the lamina muscularis.
Deeper to this is the submucosa in which some blood vessels are visible.
glands in lamina propria
lamina muscularis
blood vessel in submucosa
50 µm

67. SLIDE 38 Abomasum (glandular stomach)
Compare this section with that of the pyloric region of the canine stomach.
2.0 mm

68. SLIDE 33 Pyloric region of glandular stomach (dog)
Identify the main layers of the stomach.
1.0 mm

69. SLIDE 33 Pyloric region of glandular stomach (dog)
Identify the main layers of the stomach.
Identify the main layers of the stomach.
Mucosa, submucosa, tunica muscularis (very thick layer) and serosa.
Due to the large size of this specimen the 4th layer of serosa is not shown.
tunica muscularis
submucosa
mucosa
split in tissue
(artefact)
lumen
1.0 mm

70. SLIDE 33 Pyloric region of glandular stomach (dog)
Identify : deep gastric pits
coiled glands in lamina propria opening into gastric pits
lamina muscularis
LM : lamina muscularis
C : coiled glands C LM
gastric pits
250 µm

71. Lectures. Dr Tej Dhoot.
Second Year Histology GIT-3, RUMINANT STOMACH. J.Bredl
Gross Anatomy Correlates. Dr S.Frean.
Slides and Stains. Tanya Hopcroft.
Compressed and updated version /7.