Ruminant & Hind-gut Fermentors

Question 1

what are the 4 tunics of the GI tract?

Answer 1

• Mucosa
• Submucosa
• Muscularis
• Serosa or adventitia

Question 2

what are the three parts of the mucosa?

Answer 2

• Epithelium
• Lamina propria
• Muscularis mucosa

Question 3

what muscle type is found in the GI tract?

Answer 3

smooth

Question 4

what are the two layers of the tunica muscularis (in the typical gut section)?

Answer 4

• The inner circular muscle layer forms sphincters
• The outer longitudinal muscle layer may form
  longitudinal bands (tenia)

Question 5

what is the difference between an adventitia and serosa

Answer 5

• Tunica adventitia:
  o ill-defined layer of connective tissue blending with surrounding connective tissue
• Tunica serosa:
  o thin connective tissue layer covered by mesothelium
  o (a simple squamous epithelium) aka the visceral peritoneum

Question 6

what type of epithelium found in the mouth, esophagus, tongue, stomach (different sections), small intestine, large intestine, and rectum.

Answer 6

Mouth: stratified squamous epithelium
Esophagus: thick stratified squamous epithelium
Tongue: stratified squamous epithelium
Stomach: simple columnar epithelium
Small intestine: simple columnar epithelium
Large intestine: simple columnar epithelium
Rectum: stratified squamous non-keratinized epithelium

Question 7

what are the four stomachs in the ruminant?

Answer 7

1. Rumen
2. Reticulum
3. Abomasum
4. omasum

Question 8

Which are the forestomachs? Which is the true stomach?

Answer 8

• The rumen, reticulum, and omasum are the forestomachs
• The abomasum is the true stomach

Question 9

Is the rumen on the right or left side?

Answer 9

left

Question 10

is the abomasum on the left or the right side?

Answer 10

right

Question 11

what are the physical features of the rumen, reticulum, and omasum

Answer 11

Rumen:
- Luminal surface is covered with small, paddle-shaped papillae
- Does NOT have a muscularis mucosa

Reticulum:
- Tripe
- Important for mechanical digestion
- Most cranial compartment of the 4 stomachs
- Located on the median plane against the diaphragm
- Surface folds form honeycomb-like network of ridges with muscularis mucosa in the free edge only
- Small secondary papillae extend from the folds

Omasum:
- Heavy & hard
- Absorption of water (60%)
- Called the “butcher’s bible” or “book) because the muscular laminae look like the pages of the book

Question 12

which has numerous paddle-shaped papillae?

Answer 12

rumen

Question 13

which does not have a muscularis mucosa?

Answer 13

rumen

Question 14

which is found along the median plane against the diaphragm?

Answer 14

rumen

Question 15

which has honey-combed folds?

Answer 15

reticulum

Question 16

Which is known as the butcher’s bible?

Answer 16

omasum

Question 17

Rumination

Answer 17

• Ruminants chew cud
• Rumination involves:
  o Bolus of previously eaten food carried back into
  the mouth by reverse peristalsis
  o Fluid in bolus is squeezed out with the tongue and
  swallowed
  o Bolus is rechewed and reswallowed
• Rumination may occupy ~1/3 of the ruminant’s day

Question 18

Eructation

Answer 18

• Fermentation of food in the rumen generates large quantities of gas
• Belching is how ruminants get rid of fermentation gases

Question 19

Sigmoid flexure

Answer 19

• Region of the descending colon with a long mesocolon hanging down into the abdomen
• Allows great movement during rectal palpation

Question 20

what is the purpose of the reticular groove?

Answer 20

a channel from the esophagus to the omasum (bypasses the rumen)

Question 21

Know the structure of the spiral colon of the ruminant

Question 22

what branch of the abdominal aorta supplies the ruminant forestomach?

Answer 22

celiac artery

Question 23

do horses have gall bladders?

Answer 23

NO

Question 24

what are the three parts of the equine cecum? Is it on the left or right side of the body?

Answer 24

1. cecal base
2. cecal body
3. cecal apex

RIGHT SIDE

Question 25

what are the four parts of the equine ascending colon?

Answer 25

• Ascending colon (~12 feet long)
  o Right ventral colon (sternal flexure)
  o Left ventral colon (pelvic flexure)
  o Left dorsal colon (diaphragmatic flexure)
  o Right dorsal colon
   Ampulla coli is the expanded terminal portion
  of the right dorsal colon

Question 26

what is the direction does the transverse colon travel? Left to right or right to left?

Answer 26

travel from right to left

Question 27

what is the order of structures that digesta travels from the cecum to the rectum in the horse (including the names of the different flexures).

Answer 27

• Small intestines are ~70’ long
• Small intestine empties into the cecum via the ileocecal
  orifice (1)
• Ingesta passes from the cecum to the colon via the
  cecocolic orifice (2)
• Cecum is large, and it takes feed ~3-4 days to pass into
  the colon
• Allows for slow fermentation of fiber

Question 28

what is number of tenia located on the right dorsal colon, the left dorsal colon, the right ventral colon, and the left ventral colon

Answer 28

• Tenia (bands)
• Right dorsal colon: one band in mesocolon and 2 free
• Left dorsal colon: one band in the mesocolon
• Right & left ventral colon: 2 bands in the mesocolon and 2 free