Ruminant anatomy and physiology Flashcards

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1
Q

What are the four chambers of the ruminant stomach and which are non-glandular and which are glandular?

A
  • reticulum
  • rumen
  • omasum
    = non-glandular
  • abomasum
    = glandular
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2
Q

What are foregut fermenters?

A
  • digestive process in which plant material is fermented in a specialized combination of stomach compartments
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3
Q

What is rumination?

A
  • animal regurgitates previously consumed food and chews it further and re-swallows
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4
Q

What is eructation?

A
  • release of gas produced by fermentation from the stomach or oesophagus through the mouth
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5
Q

What are pseudo-ruminants?

A
  • like ruminants use foregut fermentation but have 3 compartments instead of 4
  • camels and hippos
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6
Q

What do the three compartments of the pseudo-ruminant stomach do?

A
  • C1 - essentially a fermentation vat
  • C2 - some nutrient absorption occurs
  • rhythmic contractions then eructation and regurgitation
  • C3 - true stomach - distal part secretes HCL
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7
Q

Where does the reticulum lie?

A
  • lies cranial to the rumen under the 6th-8th ribs
  • lies up against the diaphragm
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7
Q

What distinct feature does the reticulum have?

A
  • distinct honey comb structure covered in short papillae
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7
Q

The rumen and reticulum are often together - what is their joint term?

A
  • reticulorumen
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8
Q

What lines the reticulum?

A
  • non-glandular mucosa lined by stratified squamous epithelium
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9
Q

What lines the rumen?

A
  • non-glandular mucosa
  • keratinised stratified squamous epithelium
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10
Q

What in the rumen increases the surface area 7-fold?

A
  • papilla present formations of the lamina propria and submucosa
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11
Q

What layer is not present in the rumen?

A
  • muscularis mucosa is absent
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12
Q

Where are papillae not present in the rumen?

A
  • not present over the centre of the roof or the free margins of the pillars
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13
Q

Where does the omasum lie?

A
  • lies within the intrathoracic part of the abdomen to the right of the reticulorumen
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14
Q

How are short papillae formed in the omasum?

A
  • internal parallel laminae - thick muscular sheets covered with non- glandular mucosa forms papillae
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15
Q

Where does the muscularis mucosa extend into in the omasum?

A
  • extends into the laminae
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16
Q

What is the abomasum?

A
  • the true stomach with glandular mucosa containing gastric glands and pyloric glands
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17
Q

What covers the abomasum?

A
  • simple columnar epithelium
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18
Q

What increases the mucosal surface area if the abomasum?

A
  • mucosal surface area increased by large folds which do not disappear when the stomach distends
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19
Q

The muscularis externa (found in the abomasum) is comprised of what?

A
  • inner circular layers
  • outer longitudinal layers of smooth muscle
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20
Q

In calves what prevents milk from entering the rumen (which isn’t fully developed)?

A
  • oesophageal groove = muscular folds of the reticulorumen
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21
Q

What are new-born calves described as?

A
  • pre-ruminants
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22
Q

What is the transition phase in calves?

A
  • from pre-ruminant to ruminant
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23
During the ruminant phase was is the sole source of feed?
- dry feed
24
The rumen accounts for how much of all stomach compartments?
- 70%
25
What muscles make up the abdominal wall?
- cutaneous trunci - external abdominal oblique - internal abdominal oblique - transversus abdominus & rectus abdominus
26
What is the origin of the external abdominal oblique?
* costal part - outer surface of the last eight ribs * lumbar part - last rib and thoracolumbar fascia
27
Where does the external abdominal oblique insert?
- via aponeurosis onto the Linea alba and pre-pubic tendon
28
How do the fibres run in the external abdominal oblique?
- caudoventrally
29
What is the origin of the internal abdominal oblique?
- tuber coxae and the pelvic tendon of the EAO and transverse processes of the lumbar vertebrae
30
Where does the IAO insert?
- via the aponeurosis onto the Linea alba and last rib forming the external lamina of rectus sheath
31
How do IAO fibres run?
- cranioventrally
32
How is the caudal border of the paralumbar fossa formed?
- attachments from the tuber coxae from a distinct ridge
33
What is the origin of the transverse abdominus?
- tips of the transverse process of the lumbar vertebrae and last rib
34
Where does the TA insert?
- via aponeurosis dorsal to the rectus abdominis onto linea alba, forming the internal lamina of the rectus sheath
35
How do TA fibres run?
- dorsoventrally
36
What is the origin of the rectus abdominus?
- xiphoid process and ventral aspect of the last 10 ribs
37
Where does the RA insert?
- cranioventral pubic brim
38
How do RA fibres run?
- caudoventrally
39
What gives the RA an interrupted appearance?
- transverse tendinous intersections
40
What nerves innervate the abdominal wall from T12?
- costoabdominal nerve - iliohypergastric nerve - ilioinginal nerve - gentiofemoral nerve
41
What nerve innervates the abdominal wall from the L5 vertebrae?
- ventral perineal nerve
42
What does the top of the complex stomach touch?
- the diaphragm
43
What does the base of the complex stomach touch?
- the abdominal wall
44
What is the left side and the right side of the complex stomach called?
* left = parietal surface * right = visceral surface
45
During ruminant development what nutrient is required?
- volatile fatty acids
46
When do rumen contractions begin?
- 3 weeks of age
47
Why is it important to know where nerves are?
- to block nerves - for muscle suturing
48
Where can you find the lumbar fosser?
- at the end of the transverse processes of the lumber vertebra
49
Where is the liver located in the thoracic abdomen?
- immediately behind the diaphragm
50
What does development of the rumen do to the liver?
- pushes the liver entirely to the right half of the abdomen
51
What does the ruminant liver not have?
- no fissures
52
What does the ruminant liver consist of?
- left and right hepatic lobes - quadrate lobe and caudate lobe
53
What does the ruminant pancreas have?
- 2 limbs
54
What is the pancreas closely associated with?
- with the liver and descending duodenum
55
What duct is present in small ruminants?
- pancreatic duct
56
What duct in present in the ox?
- accessory duct
57
The large rumen occupies the left side of the abdomen - therefore what happens to the intestines?
- they are pushed to the right side of the abdomen
58
What is the position of the jejunal coil dependant on?
- of the fullness of the rumen and size of the uterus
59
What side of the abdomen is the cecum located on?
- the right side
60
What is not present in the large intestine?
- no taenia nor haustra = big thick bands of longitudinal muscle that pulls intestine together
61
Which direction does the blind end of the large intestine point?
- points caudally
62
What is the longest part of the intestines and what characteristic does it have?
- ascending colon = longest - has a characteristic spiral arrangement
63
What is the ox's intestinal arrangement?
- 2 centripetal turns reversed in central flexure and succeeded by 2 centrifugal turns
64
What is a sheep intestinal arrangement?
- 3 centripetal turns and 3 centrifugal turns
65
What is a goats intestinal arrangement?
- 4 centripetal turns and 4 centrifugal turns
66
How does the short transverse colon continue as the descending colon?
- it crosses the midline cranial to the root of the mesentery to continue as the descending colon
67
How is the rectum formed?
- descending colon upon entering the pelvis becomes the rectum
68
In a rectal examination where would you find the rumen and left kidney?
- left abdomen = rumen - right abdomen = left kidney - just right of midline
69
During a rectal exam what would you find in the caudal abdomen?
- ovaries and uterus - bladder - aorta - pelvis
70
What layers would you find in the complex stomach?
- gas - fibre mat = moderate fermentation - intermediate zone = intense fermentation - liquid zone = moderate fermentation
71
What are the 3 types of rumen contractions?
- primary contractions (mixing contractions) - contractions related to rumination - secondary contractions (contractions related to eructation)
72
How do mixing contractions move?
- start in the reticulum and move caudally along the rumen as a peristaltic wave
73
How do reticular muscles contract?
- contract twice in 5-10 secs with brief pause
74
what do mixing contractions do?
- forces coarse fibrous material from top of reticulum to central and dorsal rumen - completely empties the reticulum of finely-dispersed well-fermented content from lower portion
75
How do rumen contractions move?
- starts in cranial sac and passes dorsally and caudally in dorsal rumen sac moving ingest into the caudodorsal blind sac
76
What does contraction of the caudodorsal sac do?
- forces content cranially - similar occurs in the ventral rumen sac
77
What is rumination?
- transportation of swallowed ingesta back into oral cavity for additional chewing
78
How does rumination occur?
1. Extra reticular contraction preceding the biphasic contraction 2. Hydrostatic pressure difference between oesophagus and reticulum draws reticular content into oesophagus 3. Anti-peristaltic contractions in the oesophagus propels bolus into oral cavity 4. Fluid fraction re-swallowed whilst rest of bolus masticated before being re-swallowed 5.Increased saliva secretion increases fluid and ions delivered to reticulorumen
79
In the course of 24 hours how much gas can a high yielding cow produce from fermentation?
- 250-500L gas
80
What are secondary contractions?
- rumen contractions associated with eructation
81
How many primary contractions are between each secondary contraction?
* 2-3
82
How does eructation happen?
1. Contraction start in the caudal blind sacs and move cranially along the dorsal sac 2. Gas cap pushed towards oesophageal opening 3. Negative intra-thoracic pressure draws gas into oesophagus when sphincter opens 4. Gas passes to mouth via anti-peristaltic waves
83
How do we assess forestomach activity?
- number and strength of contractions of the dorsal sac of the rumen over 5 minutes
84
During assessment of forestomach activity you can auscultate/fell over the paralumbar fossa. How many contractions should you expect to feel at rest and during feeding?
* at rest = 1 contraction/min * during feeding = 2-3/min
85
How are contractions regulated/
- Long reflexes mediated via the vagus nerve - Short reflexes mediated via ENS
86
Why is is good to assess ruminal contractions?
- Strength and frequency of ruminal contractions good indicator of a ruminants well- being
87
What can go wrong in ruminants?
- LDA - RDA - Abdominal volvulus - twist of abomasum - Ruminal tympani – bloat - Hardware disease – traumatic reticulopericarditis