Gastrointestinal Tract

Question 1

Describe the peritoneum.

Answer 1

A serosal layer lining abdominal and pelvic cavities.
- Flattened mesothelial cells supported by fibrous connective tissue.
- Has a parietal and visceral layer, lubricated by a serous fluid.
- Has a large surface area so any fluid that escapes can be quickly reabsorbed and allows for a method of distributing drugs in the body via intraperitoneal injection.

Question 2

What is a use of some of the mesenteries being very long?

Answer 2

Allowing organs to be moved around during surgery for access to different structures.

Question 3

What is the blood supply of the parietal and visceral peritoneums?

Answer 3

Parietal peritoneum lines the abdominal wall. Its blood supply, innervation and lymphatic drainage are the same as the overlying structures.

Visceral peritoneum envelops organs. Its blood supply, innervation and lymphatic drainage are the same as the organs is surrounds.

Question 4

What is the structure of the mesenteries?

Answer 4

Reflection of 2 layers of peritoneum to make a fold suspending an organ:
- Mesoduodenum,
- Mesojejunoileum/great mesentery
- Mesocolon

Blood supply, innervation and lymphatic drainage run between peritoneal layers. These branch out from the root of the mesenteries.

Question 5

What are the embryonic derivations of the mesenteries?

Answer 5

• Dorsal mesogastrium becomes the dorsal mesentery
• Ventral mesogastrium becomes the ventral mesentery

Separated by the GI tract

Question 6

What are the omentums?

Answer 6

Peritoneal attachments associated with the stomach from the mesogastrium.

• Greater omentum arises from greater curvature of the stomach and has 2 double layers
• Lesser omentum connects the liver and the lesser curvature of the stomach and has 1 double layer

Question 7

Name the peritoneal ligaments.

Answer 7

• Right and left triangular ligaments, coronary ligament, falciform ligament – all double layers of peritoneum travelling to and from the liver.
• Duodenocolic ligament – connects the duodenum and colon
• Iliocaecal fold – connects the ileum and caecum
• Hepatorenal ligament
• Gastrosplenic ligament
• Vesical ligament

Question 8

What are the 7 fixed points of the abdominal viscera?

Answer 8

• Cardia of stomach – attached to the diaphragm
• Hepatic ligaments – attached to the diaphragm
• Mesoduodenum – short, therefore duodenum lies in the dorsal abdomen
• Dorsal extremity of spleen – near origin of greater omentum
• Dudenocolic ligament – attached duodenum to colon
• Mesorectum – short, therefore rectum lies in the dorsal abdomen
• Bladder – vesical ligaments are short but cranial movement is possible

Question 9

Describe the structure of the stomach.

Answer 9

• Oesophagus enters the stomach at the cardiac sphincter, a ring of muscle that can contract to block the tube.
• Fundus is the region of the stomach that is between the cardiac region and the body of the stomach. This varies between species.
• Pyloric region has he pyloric sphincter, the circular ring of muscle that controls the movement of food out of the stomach and into the duodenum. Important that food stays in the stomach long enough to be churned and release nutrients to be absorbed by the small intestine.
• Has the lesser and greater curvatures of the stomach.
• Internal surface of the stomach has an arrangement of folds called Mugabe. These help direct food through the stomach.

Question 10

what are the 3 branches of the coeliac artery and what do they supply?

Answer 10

• Left gastric artery – stomach. Gastric arteries supply the lesser curvature of the stomach
• Splenic artery – spleen. Has a branch called the left gastroepiploic artery – supplies the greater curvature of the stomach. Spleen supplied by left gastroepiploic artery.
• Hepatic artery – liver. Supplied by right gastric artery and right gastroepiploic artery.

Question 11

What is the gross structure of the small to large bowel?

Answer 11

Stomach > duodenum > jejunum > ileum > caecum > colon > rectum

Question 12

What is the blood supply to the small and large bowel?

Answer 12

• Cranial mesenteric supplies the caudal duodenum, the jujunoilium, ascending and transverse colon

• Caudal mesenteric artery supplies the descending colon and rectum

Question 13

What are the divisions of the GI tract?

Answer 13

• Foregut – distal oesophagus to cranial duodenum, liver and pancreas. The spleen has the same blood and nerve supply but not derived from the foregut. Coeliac artery
• Midgut – caudal duodenum and pancreas to transverse colon. Cranial mesenteric artery
• Hindgut – descending colon and rectum. Caudal mesenteric artery

Question 14

Describe venous drainage of the GI tract.

Answer 14

Do not have paired veins of unpaired branches. This is because the GI tract is absorbing all the nutrients and, if fed directly back into the systemic circulation, there would be toxic levels of chemicals and substances. So blood must be filtered before it enters the systemic circulation again.

• Gastroduodenal, splenic, cranial mesenteric and ileocolic veins feed into the hepatic portal vein.
• Hepatic portal vein drains to the liver, where blood can be processed and filtered.
• Blood then drains into the caudal vena cava to enter the systemic circulation.

Question 15

Describe innervation of the abdominal viscera.

Answer 15

Motor (autonomic) – general visceral efferent:

Parasympathetic
- Vagus nerve innervates the foregut and midgut
- Pelvic nerves from S1, 2 and 3 supply the hindgut and pelvic organs

Sympathetic via sympathetic chain. T1 – L2.
- Smooth muscle of the GI tract
- Coeliac ganglia – foregut
- Cranial mesenteric ganglion – midgut
- Caudal mesenteric ganglia – hindgut and supplies hypogastric nerves that supply the pelvic viscera

Sensory – general visceral afferent

Question 16

State the 3 functions of the liver.

Answer 16

• Protein, carbohydrate and fat metabolism
• Bile production
• Processing of digestion products

Question 17

Name the lobes of the liver.

Answer 17

• Left medial lobe
• Right medial lobe
• Left lateral lobe
• Right lateral lobe
• Quadrate lobe

Question 18

What vasculature enters and exits the liver via the porta?

Answer 18

• Hepatic artery
• Hepatic portal vein
• Caudal vena cava

Question 19

What 4 ligaments attach the liver to the body wall?

Answer 19

Left and right triangular ligaments
Coronary ligament
Falciform ligament

Question 20

What impressions does a fixed liver have?

Answer 20

Stomach
Right kidney
Lesser omentum
Gall bladder

Question 21

Describe blood flow in the liver lobules.

Answer 21

• Blood flow entering the porter is going to detach a lot of extension and
  they will put blood vessels inwards which will continue to divide.
• The parenchyma of the liver also follows the same pattern
• Tunis phyprocessor encloses the parenchyma has teh same path and creates the pattern (lobules)

Blood vessels divided down and down into smaller blood vessels. The central veins collect the remaining blood once it has been processes by the hepatocytes which will then empty into larger and larger veins until they empty into the hepatic vein which will drain into the caudal vena cava.

Question 22

What is the pathway of bile secretion?

Answer 22

As food travels down the GI tract, the gall bladder is stimulated and releases the stored bile into the duodenum, which mixes with the ingesta as it travels down the tract.

1. Hepatic duct system begins with tiny ducts called canaliculi within liver lobules.
2. These open up into larger ducts called ductules.
3. These become hepatic ducts.
4. Bile duct exist the liver via the porta.
5. At the porta, hepatic ducts combine to form a common trunk that goes to the duodenum.
6. Side branch called the cystic duct goes to the gall bladder.
7. Common trunk distal to the cystic duct goes to the bile duct.

Question 23

What is the location of the pancreas and its lobes?

Answer 23

Nestled in the curve of the duodenum.
- At the duodenum papilla, there is a common opening for bile duct and pancreatic duct.
- The lobes of the pancreas are located behind the stomach.
- Has a distinct left and right lobe that from a v shape a the cranial flexure of the duodenum.
- Right lobe runs within the duodenum in the mesentery to the duodenum
- Left lobe is shorter and thicker and extends over the caudal surface of the stomach and towards the spleen.

Question 24

What are the functions of the pancreas?

Answer 24

Has an exocrine function and produces digestive enzymes that empty into the proximal duodenum through the pancreatic duct.
Has endocrine function and islands of Langerhans that have alpha and beta cells producing insulin, glucagon and gastrin.

Question 25

What are the 2 openings when the pancreas empties into the duodenum?

Answer 25

• The major duodenal papilla is the opening for the major pancreatic duct (and bile duct). This drains the left lobe and some of the right lobe. • Also has a minor duodenal papilla, draining the right lobe of the pancreas

Question 26

How is colic in horses detected using imaging?

Answer 26

Horses often experience colic, abdominal pain, and is often associated with the GI tract in horses. In horses, there are few x-ray machines to penetrate the skin so relies on ultrasounds. Lots of black on an ultrasound connotes lots of fluid in the tract, which could mean there is a blockage or obstruction somewhere preventing the fluid from moving.

Question 27

How do horses' diets affect their GI tracts?

Answer 27

Do not adapt well to changes in diet and are out on high starch diets in order to give them energy for things like racing. They ferment this and it can become acidic, which can cause problems with the microbial flora in the gut. Horses are triple grazers and only take in a small amount of food over short periods of time, so have a smaller stomach. Wild horses with graze for 16 hours a day on poor quality grass. Domesticated horses are fed 2-3 times a day on concentrated food, and if given too much at these 3 meals, the stomach can be overloaded. Food will overflow into the small and large intestines before it has had time to be properly processed in the stomach.

Question 28

What are the 2 regions of the equine stomach surface? What are they separated by?

Answer 28

• Fundus/saccus caecus – dorsal non-glandular region, lined with stratified squamous epithelia. • Fundic region – ventral glandular region, lined with simple columnar epithelium. Separated by a ridge called the margo plicatus.

Question 29

What is the cardiac sphincter and its effect?

Answer 29

Horse stomachs have a very well developed oblique cardiac sphincter. Sits obliquely due to the oesophagus entering the stomach at an angle. This result in food only being able to travel one way in the stomach, and so horses cannot vomit. If a horse ingests something toxic, it is not until the horse becomes very sick that the cardiac sphincter relax sufficiently to allow food to travel back up the oesophagus. This means horses can become sick very quickly, as the toxin is trapped in the stomach and can be absorbed easily into the body.

Question 30

Describe the components of the non-glandular region of the stomach.

Answer 30

- Fundic and fundus regions are separated by a cardiac region, and is where the margo plicatus is found. - Margo plicatus is important, as the fundic regions produces stomach acid and the fundus region has no protection against this. - In a wild horse, gravity means that acid will stay in the fundic region. - Botflies attach to the non-glandular region.

Question 31

Describe gastric ulceration syndrome.

Answer 31

In domestic horses, if the stomach is overloaded, the acid component can be forced up past the cardiac region and margo plicatus and into the fundus region. This condition is gastric ulceration syndrome. Acid begins to digest the walls of the non-glandular region. Horses under stress may produce more acid or horses doing a lot of jumping and galloping may have acid splash and have more ulceration.

Question 32

Describe the equine caecum.

Answer 32

Is distinctive and sickle-shaped: - Largely attached at the base and is on the left. - Dorsal borders are the base of the spleen and this is where blood vessels enter - Apex points cranially - Hilus is where the blood vessels are running down and this is on the intestinal surface, against the abdominal viscera - Has a renosplenic ligament that goes from the spleen to the kidney

Question 33

Describe the position of the equine caecum.

Answer 33

- A very large structure in the horse and sits on the right hand side. Roughly sits at the level of the last/18th rib. - In horses, unlike dogs, the caecum is large and everything goes through the caecum. - The ileum opens into the caecum at the ileocecal junction. - The base of the caecum is retroperitoneal and so the caecum is fixed to the body wall dorsally - The apex of the caecum is entirely movable

Question 34

What is the function of the equine caecum? Describe its structure.

Answer 34

The contents is mixed and the caecum contracts. After mixing. It empties out into the right ventral colon through the caecocolic junction. Made up of 4 tenial bands, made up of longitudinal muscle that contract to help propel contents from the apex to the base of the caecum against gravity to allow it to empty into the colon. Outpouchings called haustra. They work as little fermentation chambers, as they allow mixing of contents with microbes and fluid.

Question 35

What is the large equine colon and the small equine colon?

Answer 35

• Lage colon = ascending colon. This is very large in the horse and so folds up and around the abdominal cavity. The order of folding is very important, as the ascending colon is not attached to the body wall. This means that a build up of gas can cause the ascending colon to twist and turn on itself and move in different positions. • Small colon = transverse and descending

Question 36

Outline a flowchart of the equine ascending colon.

Answer 36

Right ventral colon > sternal flexure > left ventral colon > pelvic flexure > left dorsal colon > diaphragmatic flexure > right dorsal colon > transverse colon

Question 37

Describe the structure of the equine ascending colon.

Answer 37

- First part is on the right hand side, where the caecum empties into the colon. - Travels ventrally along eth body wall so this section is the right ventral colon. - This travels cranially until it reaches the front of the abdominal cavity. - It flexes at the sternal flexure at the diaphragm and begins travelling along left and ventrally, so is the left ventral colon. - Colon goes from the ventral to dorsal at the pelvic flexure. - The colon then travels as the left dorsal colon cranially again until it reaches the diaphragm, where it flexes at the diaphragmatic flexure. - It then travels as the right dorsal colon and then becomes the transverse colon, the descending colon. - After the pelvic flexure, diameter decreases. This can cause blockages and pelvic flexure impactions.

Question 38

Describe the taeniae pattern in the ascending equine colon.

Answer 38

Taeniae/tenial bands - longitudinal bands of smooth muscle with intervening haustra/sacculations. Caecum = 4 taeniae Right ventral colon = 4 taeniae Left ventral colon = 4 taeniae Left dorsal colon = 1 narrow band caudally and 3 widening cranial bands Right dorsal colon = 3 taeniae

Question 39

What stomach does the pig have?

Answer 39

Monogastric, a single simple stomach

Question 40

How is the porcine digestive tract different to the canine's?

Answer 40

• Has a spiral formation in its ascending colon • Different topography • Viscera smells like pigs • ‘Moroccan’ leather liver has a stippled appearance

Question 41

How is the porcine GI tract different to the equine GI tract?

Answer 41

- Unlike the horse, the pig has a gallbladder. - Has an outpouching called the diverticulum in the cardiac region of the porcine stomach - Cardiac region is enlarged in the pig - Fundic region is relatively smaller in the pig - Has a torus pyloricus, a projection found in the pyloric region of the stomach - Spleen is quite long and strap like and is attached to the stomach

Question 42

What is unique about the porcine caecum?

Answer 42

The pig caecum is found on the left hand side, unlike most other species. - Base is near the left kidney - Related to the left flank - Sweeps caudally and ventrally

Question 43

Describe the structure of the porcine colon.

Answer 43

Ascending colon is spiral shaped. There are 2 limbs to this conical spiral: • Proximal limb forms the centripetal/outer turns • Distal limb forms the centrifugal (inner) turns The apex of the spiral colon lies agaisnt the left flank. Jejunoileum travels around the edge of the spiral column of ascending colon like a frill before emptying into the ascending colon.

Question 44

Name the 4 chambers of the ruminant stomach and their relative sizes.

Answer 44

• Rumen (80% adult ox) – occupies most of the left side • Reticulum (5%) – most cranial and sits behind the diaphragm • Omasum (8%) – ball like structure in the midline • Abomasum (7% adult ox, 60% calf) – true stomach

Question 45

Describe the relative sizes of the chambers in a calf.

Answer 45

First 3 chambers are much less developed in new-born calves, as they are not eating fibrous material, they are suckling milk, which is chemically digested in the abomasum. Milk will bypass the rumen and reticulum and travel into the omasum to the abomasum. As the calf matures, fibre in the diet increases and there is expansion of the first 3 chambers, particularly the rumen.

Question 46

How are the first 3 chambers developed?

Answer 46

Formed by outpouchings of the cranial part of the stomach. In development and twisting, the cranial part of the stomach expands even further and develops these 3 subparts. These 3 are developed to aid the breakdown of fibrous material.

Question 47

Describe how and why regurgitation occurs in the ruminant.

Answer 47

- In the cranial aspect of the stomach, there is a lot of fluid. - Food entering from the oesophagus is churned with the fluid to extract nutrients. - Smaller particles are the fibres are broken down will sink – gravity takes them to the ventral aspect. - Larger particles float on top of the fluid and can be regurgitated and re-chewed and re-mixed with salivary enzymes. - This is in contrast to the equine cardiac sphincter that doesn’t allow them to vomit – ruminants can voluntarily vomit. - Regurgitation only occurs in the rumen and reticulum, the first 2 chambers. - There is no stomach acid in the rumen and reticulum, as chemical digestion occurs in the abomasum.

Question 48

Describe the topography of the ruminant GI tract.

Answer 48

- There is no gap in between the reticulum and the diaphragm for the liver in ruminants is displaced completely to the right hand side of the body. - May see a small part of the abomasum cranioventrally, but the majority of the left hand side is the rumen. - On the right, the oesophagus can be seen entering at a junction between the reticulum and the rumen. - From the abomasum, exits into the pyloric region and into the duodenum. - Omasum pushes into the liver, creating an impression on fixed ruminant livers. - Spleen in still situated on the left hand side.

Question 49

Describe the function and position of the rumen.

Answer 49

Principle site of bacterial fermentation as a foregut digester Occupies most of the left side of the abdominal cavity in the adult. All other organs displaced to the right except for the spleen and small parts of cranial reticulum and abomasum.

Question 50

Describe the structure of the rumen.

Answer 50

Rumen has ruminal grooves – they divide the rumen into smaller pockets and carry all the blood vessels that supply the ruminal walls. • External grooves are mirrored by corresponding internal folds and pillars dividing the rumen into intercommunicating sacs • Left and right longitudinal grooves run along the length of the rumen and the rumenoreticular groove separates the rumen and reticulum.

Question 51

What is the function of the ruminal papillae?

Answer 51

Papillae vastly increase the surface area for absorption of nutrients. They are found in the areas of the rumen where there is most nutrients to be absorbed, the ventral sacs, where smaller particles sink to. Dorsal aspect of the sacs is gas, so less need for absorption and so fewer papillae.

Question 52

What is traumatic reticulitis?

Answer 52

Ingested foreign bodies can penetrate the walls as the reticulum churns contents around. If sharp, the foreign body can cause penetration of the wall and cause swelling of the reticular wall.

Question 53

What is traumatic peritonitis?

Answer 53

Ingested foreign bodies can penetrate right through the wall and cause bacteria to seep out into the abdomen.

Question 54

What is the structure of the internal surface of the reticulum?

Answer 54

Villi are raised in these hexagonal forms in a net-like appearance.

Question 55

What is the position, structure and function of the omasum?

Answer 55

- Lies on the right hand side between the left rumen and reticulum and right liver, body wall and diaphragm. - Interior has crescentic laminae, sometimes called leaves - Fluid travels proximal to distal down the folds - Primary role is water absorption before it enters the abomasum for digestion

Question 56

What is the structure and position of the abomasum?

Answer 56

Has ruggae Lies on right hand side mainly, apart from the fundus that lies cranial and ventral on the right. Not fixed in place by mesentery, so gas distention can cause the abomasum to move around within the abdomen. If gas distention causes the abomasum to travel left and under the rumen, it can get stuck between the rumen and body wall on the left hand side, in left displacement of the abomasum. Can also get displaced to the right by gas distention.

Question 57

What is the reticular/gastric groove?

Answer 57

- 2 spirally twisted lips of tissue on the wall of the reticulum and the lesser curvature of the omasum - Important for calves on milk-based diets, as the gastric groove acts as a bypass mechanism for milk to bypass the rumen and reticulum and pass straight to the omasum and abomasum for chemical digestion. - To stop ingest coming out into the reticulum as its travels along, a vagal reflex is initiated when a calf suckles. The vagal nerve is stimulated and causes the lips of the gastric groove to roll round and from a complete tube. - Gastric groove is still present in adults but lack of suckling means no vagal reflex and food is not diverted along the gastric groove. The use of certain chemicals can stimulate the vagal reflex if there is a need to administer medicines straight into the abomasum and omasum and not have it fermented.

Question 58

Describe the blood supply of the ruminant chambers.

Answer 58

All of these chambers are foregut structures. - Supplied by the coeliac artery. - Blood supply to the abomasum supplied by the left and right gastric arteries at the lesser curvature and left and right gastroepiploic arteries to the greater curvature of the abomasum. - Left and right ruminal arteries are branches of the coeliac artery and run in the longitudinal grooves to the rumen. - Venous drainage involves draining all 4 chambers via the splenic vein into the hepatic portal vein to the liver.

Question 59

Describe the innervation of the ruminant chambers.

Answer 59

Parasympathetic via the vagal nerve: - Vagus nerve runs through the thorax and the dorsal and ventral branches travel together through the diaphragm. - They split up the ruminant, with dorsal branch innervating the rumen and the ventral branch innervating the reticulum, the omasum and the abomasum. Sympathetic via the coeliacomesenteric plexus with very similar route to the arteries.

Question 60

What is the attachment of the rumen, reticulum and abomasum?

Answer 60

Are caudal outpouchings of the gut tube, so they are associated with the greater omentum, which is attached to: • The greater curvature of the abomasum • Right longitudinal groove of the rumen • Left longitudinal groove of the rumen • Reticulum • Duodenum

Question 61

What is the attachment of the omasum?

Answer 61

Forms as an outpouching of the cranial aspect so is associated with the lesser omentum, which is attached to: • Lesser curvature of the abomasum • Porta of the liver • Greater curvature of the omasum

Question 62

Describe the body wall and mesenteries of the ruminant foregut.

Answer 62

- Peritoneal layer running along the body wall - It reflects off and onto the dorsal sac of the rumen, which can no layer of peritoneum - So dorsal part of the rumen is indirect contact with the body wall, making it a fixed point for the rumen and so cannot move around in the abdomen. - Peritoneum reflect off the body wall and reflects on to the dorsal sac and travels down the longitudinal groove - It then reflects off the ruminal wall and travels along the ventral body wall - Travels all around the right hand side of the abdomen - Then merges with the duodenal mesentery - Second layer than travels back with the same route, joining on to the right longitudinal groove of the rumen - Greater omentum travels around the dorsal and ventral wall and up around the duodenum. - Pocket made in the loop of greater omentum contains all the intestines in it, the supraomental recess - Greater omentum is not attached caudally

Question 63

Describe the structure of the ruminant caecum.

Answer 63

Caecum points caudally and in the right pelvic inlet. Sigmoid flexure after the caecum.

Question 64

Describe the structure of the ruminant colon.

Answer 64

Ascending spiral colon can be divided into 3: • Proximal loop is the sigmoid flexure • Spiral loops is a flat spiral loop not conical • Distal loop before the transverse colon Transverse colon Descending colon

Question 65

What is the structure of the ruminant jejunum?

Answer 65

The jejunum hangs of the ascending colon like a frill, located ventrally and packed around the spiral shape.

Question 66

What is the cardia, fundus and pylorus?

Answer 66

Cardia – opening into stomach. Lies on the left. It is wide in the canine – possibly relates why dogs can easily vomit. Fundus – blind ending dome above the cardia. Pylorus – terminal part of the stomach which enters the duodenum. It has a muscular sphincter and lies on the right hand side of the abdominal cavity.

Question 67

What controls peristalsis in the GI tract?

Answer 67

Smooth muscle controlled by the ANS. - Parasympathetic by vagus nerve - Sympathetic: coeliac for foregut, cranial mesenteric to midgut and caudal mesenteric to hindgut

Question 68

Name 3 congenital abnormalities of the GI tract.

Answer 68

Anal atresia Umbilical hernias Pyloric stenosis

Question 69

State the blood vessels that supply oxygenated blood for each structure of the GI tract.

Answer 69

Stomach = coeliac artery Duodenum = coeliac artery and cranial mesenteric artery Pancreas = coeliac artery and cranial mesenteric artery Caecum = cranial mesenteric artery Ascending colon = cranial mesenteric artery Liver = coeliac artery and hepatic portal vein Spleen = coeliac artery Rectum = caudal mesenteric artery

Question 70

State the bony landmarks of the equine GI tract.

Answer 70

Dome of the diaphragm Tuber coxae Xiphoid process Costal arch Paralumbar fossa

Question 71

How is the external abdominal oblique affected in horses with COPD?

Answer 71

Increased respiratory effort due to airway obstruction resulting from asthma like allergic responses. Division between aponeuroses and EAO is obvious and is known as 'heave' line due to muscle hypertrophy of the EAO.

Question 72

What is significant about the cardiac regions of equine stomachs?

Answer 72

Walls are well developed, and is why horses are unable to vomit, meaning horses cannot be rid of gas and fluid from colic without stomach tubing, or the GI tract will rupture, causing peritonitis and death.

Question 73

What are the functions of the diverticulum and pyloricus in porcine stomachs?

Answer 73

Diverticulum - an outpouching where microbial fermentation takes place Pyloricus - a fleshy protuberant consisting of muscle and adipose tissue, it only allows small foods to leave the stomach

Question 74

Name the 6 lobes of the porcine liver.

Answer 74

• Left lateral lobe • Left medial lobe • Right medial lobe – heavily associated with the gallbladder • Left lateral lobe • Quadrate lobe • Caudate lobe

Question 75

What are the functions of the rumen?

Answer 75

- Because of its size, the rumen acts as a storage for feed - Regular contraction to move food around for digestion - Eliminate gases through eructation and regurgitate food back to the mouth for re-mastication. - Breaks down food particles through mechanical digestion and fermentation. - Growth of commensal microbes that digest or ferment feed to make volatile fatty caids. - Absorbs most of the VFAs from fermentation

Question 76

What is the function of the omasum in the ruminant GI tract?

Answer 76

- Transport of appropriately sized feed particles from the reticuloreumen to the abomasum - Oesophageal groove closure - Fermentation of ingesta - Absorption of water, volatile fatty acids and minerals

Question 77

What is the function of the abomasum in the ruminant GI tract?

Answer 77

Only chamber with glands, which release HCL and digestive enzymes for breakdown of feeds.

Question 78

Define rumination.

Answer 78

The process of repeated regurgitation and re-mastication of ingesta to further process it and increase the efficiency of the entire system in extracting nutrients from plant material.

Question 79

Describe the process of rumination.

Answer 79

1. Ruminants ingest food of relatively large size. 2. Large food particle size remains for longer in the rumen and this has longer time to be fermented by the symbiotic/commensal microbes. 3. Once the large food particles have been fermented for long enough, the food is regurgitated and re-masticated to decrease the food particle size. 4. Smaller particles are then swallowed and fermented further. 5. Particles are then regurgitated and re-masticated again and the process is repeated until most of the material has been mechanically broken down, most of the nutrients have been extracted and is of a size to move into the omasum.