Changes

==Introduction==

==Introduction==

The pancreas is a tubuloalveolar gland and has '''exocrine''' and '''[[Endocrine System Overview - Anatomy & Physiology|endocrine]]''' tissues. The '''exocrine''' part secretes pancreatic juice; a solution containing enzymes for carbohydrate, protein and triacylglycerol digestion. Pancreatic juice drains into the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] where it is functional. It is the larger of the two parts of the pancreas. The '''endocrine''' part secretes hormones for the regulation of blood glucose concentration, including insulin, glucagon and somatostatin. The functional units of the exocrine part are the ''islets of Langerhans''.

The pancreas is a tubuloalveolar gland and has '''exocrine''' and '''[[Endocrine System Overview - Anatomy & Physiology|endocrine]]''' tissues. The '''exocrine''' part secretes pancreatic juice; a solution containing enzymes for carbohydrate, protein and triacylglycerol digestion. Pancreatic juice drains into the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] where it is functional. It is the larger of the two parts of the pancreas. The '''endocrine''' part secretes hormones for the regulation of blood glucose concentration, including insulin, glucagon and somatostatin. The functional units of the exocrine part are the ''islets of Langerhans''.

==Structure==

==Structure==

[[Image:Sheep Pancreas.jpg|thumb|right|150px|Pancreas (Sheep) - © RVC 2008]]

[[Image:Sheep Pancreas.jpg|thumb|right|250px|Pancreas (Sheep) - © RVC 2008]]

*Located in the craniodorsal part of the abdomen in close association with the [[Duodenum - Anatomy & Physiology|duodenum]].

The pancreas is located in the craniodorsal part of the abdomen in close association with the [[Duodenum - Anatomy & Physiology|duodenum]]. It can be divided into three parts; a body and left and right lobes. The lobes are losely united by interlobular connective tissue. Connective tissue contains blood vessels, nerves and lymphatics. Generally, the portal vein runs between the left and right lobes. (see [[#Species Differences|species differences]]). The pancreas is rougly "V" shaped in all species. As mentioned in the [[#Development|development]] section, there are two ducts present in the pancreas. Their presence reflects the convergent development pattern of the pancreas, however in some [[#Species Differences|species]] one or other of the ducts may atrophy. The '''pancreatic duct''' is the biggest of the two and opens into the [[Duodenum - Anatomy & Physiology|duodenum]] with the bile duct at the major duodenal papilla. The '''accessory duct''' opens on the opposite aspect of the [[Duodenum - Anatomy & Physiology|duodenum]] at the minor duodenal papilla.

*Divided into three parts; a body and left and right lobes.

**The lobes are losely united by interlobular connective tissue.

***Connective tissue contains blood vessels, nerves and lymphatics.

**Generally, the portal vein runs between the left and right lobes. (see [[#Species Differences|species differences]]).

*Rougly "V" shaped in all species.

*As mentioned in the [[#Development|development]] section, there are two ducts present in the pancreas. Their presence reflects the convergent development pattern of the pancreas. However in some [[#Species Differences|species]] one or other of the ducts may atrophy.

**The '''pancreatic duct''' is the biggest of the two and opens into the [[Duodenum - Anatomy & Physiology|duodenum]] with the bile duct at the major duodenal papilla.

**The '''accessory duct''' opens on the opposite aspect of the [[Duodenum - Anatomy & Physiology|duodenum]] at the minor duodenal papilla.

==Exocrine Function==

==Exocrine Function==

'''Alkaline Secretion'''

'''Alkaline Secretion'''

*The pancreas produces an alakaline secretion.

 

*Pancreatic juice discharges into the [[Duodenum - Anatomy & Physiology|duodenum]] through ducts.

The pancreas produces an alakaline secretion. Pancreatic juice discharges into the [[Duodenum - Anatomy & Physiology|duodenum]] through ducts. Pancreatic juice is alkaline as it contains '''bicarbonate''' and '''chloride ions'''. Bicarbonate ions are actively transported into the duct lumen. Water follows passively by osmosis. The osmolarity of the pancreatic juice is equivalent to the osmolarity of the blood. Pancreatic juice is alkaline to neutralise the acidic gastric juice. This is advantageous because: It provides an optimal pH for the pancreatic enzymes and it prevents damage to the thin, absorptive mucosa of the [[Duodenum - Anatomy & Physiology|duodenum]]. Its alkalinity also helps to buffer the [[Large Intestine - Anatomy & Physiology|large intestine]] which is important in [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]].

*Pancreatic juice is alkaline as it contains '''bicarbonate''' and '''chloride ions'''.

**Bicarbonate ions are actively transported into the duct lumen.

**Water follows passively by osmosis.

*Osmolarity of the pancreatic juice is equivalent to the osmolarity of the blood.

*Pancreatic juice is alkaline to neutralise the acidic gastric juice. This is advantageous because:

**It provides an optimal pH for the pancreatic enzymes.

**It prevents damage to the thin, absorptive mucosa of the [[Duodenum - Anatomy & Physiology|duodenum]].

*Its alkalinity also helps to buffer the [[Large Intestine - Anatomy & Physiology|large intestine]] which is important in [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]]

'''Enzymatic Digestion'''

'''Enzymatic Digestion'''

*The alkaline secretion contains digestive enyzmes that can digest protein, carbohydrates and lipids. Digestion is discussed in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]].

 

*The following table lists the enzymes secreted by the pancreas and their effects:

The alkaline secretion contains digestive enyzmes that can digest protein, carbohydrates and lipids. Digestion is discussed in the [[Small Intestine Overview - Anatomy & Physiology|small intestine overview]].  

 

The following table lists the enzymes secreted by the pancreas and their effects:

==Endocrine Function==

==Endocrine Function==

===[[Glucagon]]===

Functional units are the '''islets of Langerhans''', which are embedded throughout the exocrine tissue. Cells of the islets produce hormones that maintain normoglycaemia. Glucagon raises the blood glucose level and insulin decreses the blood glucose level. Somatostatin acts in a paracrine fashion to inhibit both glucagon and insulin secretion. Pancreatic polypeptide is thought to be a cholecystokinin antagonist, and thus inhibits secretion of pancreatic juice.

===[[Insulin]]===

See here for more information on [[Glucagon]] and [[Insulin]].

===[[DM|Diabetes Mellitus]]===

===[[DM|Diabetes Mellitus]]===

[[Image:NIDDM cat.jpg|thumb|right|150px|An obese cat with NIDDM - © RVC 2008]]

[[Image:NIDDM cat.jpg|thumb|right|250px|An obese cat with NIDDM - © RVC 2008]]

A condition characterised by an inability to maintain normoglycaemia, with persistent hyperglycaemia observed.  

*β cell deficiency - The majority of cases of [[DM|diabetes mellitus]] seen in dogs are of this kind. It causes an inability to produce insulin.

Clinical signs include: glucosuria, polyuria and polydipsia - blood glucose concentration exceeds the renal threshold (~10mmol/l) and is excreted into the urine. The increased osmotic potential of the filtrate draws water into the filtrate which is lost in the urine. The animal drinks more to compensate for water loss. Polyphagia and weight loss are also seen where the animal compensates for persistent loss of glucose. Ketosis and ketonuria are also seen, where ketones are released for energy.

**Can be caused by congenital defects, pancreatitis and autoimmunity.

*Insulin antagonism - Seen in females in dioestrus, or in animals with [[Neoplasia - Pathology|Cushing's]] (hyperadrenocorticism).  

**[[Ovaries Endocrine Function - Anatomy & Physiology|Progesterone]], [[Pituitary Growth Hormone - Anatomy & Physiology|growth hormone]] and cortisol are insulin antagonists.

'''Types of diabetes in cats'''

*Insulin Dependant Diabetes Mellitus (IDDM); insulin deficiency - similar to human diabetes type 1. There is a failure to produce insulin.

 

**Can be caused by islet-specific amyloidosis or chronic pancreatitis leading to β cell destruction.

'''β cell deficiency''' - The majority of cases of [[DM|diabetes mellitus]] seen in dogs are of this kind. It causes an inability to produce insulin. It can be caused by congenital defects, pancreatitis and autoimmunity.

*Non Insulin Dependant Diabetes Mellitus (NIDDM); insulin antagonism - similar to human diabetes type 2.  

 

**Caused by obesity which leads to carbohydrate intolerance.

 

===Types of diabetes in cats===

 

'''Insulin Dependant Diabetes Mellitus (IDDM)'''; insulin deficiency - similar to human diabetes type 1. There is a failure to produce insulin. This can be caused by islet-specific amyloidosis or chronic pancreatitis leading to β cell destruction.

 

'''Non Insulin Dependant Diabetes Mellitus (NIDDM)'''; insulin antagonism - similar to human diabetes type 2. Caused by obesity which leads to carbohydrate intolerance.

==Vasculature==

==Vasculature==

*Recieves blood supply from the '''coeliac''' and '''cranial mesenteric''' as branches from the splenic, hepatic and superior mesenteric arteries.

The pancreas recieves its blood supply from the '''coeliac''' and '''cranial mesenteric''' as branches from the splenic, hepatic and superior mesenteric arteries. The right lobe recieves blood from the '''cranial pancreatoduodenal artery'''; a branch of the hepatic artery. The left lobe recieves blood from the splenic artery and '''caudal pancreatoduodenal artery'''; a branch of the cranial mesenteric artery. Vessels aborize within the connective tissure septa and give off rich capillary networks that surround each acini and invade each islet. The endothelium in the exocrine pancreas is continuous, whereas the endothelium of capillaries surrounding the islets in the endocrine pancreas are fenestrated. It is drained by veins that open into the portal vein. The islets recieve ample blood supply to enable an appropriate response to blood glucose level.

**The right lobe recieves blood from the '''cranial pancreatoduodenal artery'''; a branch of the hepatic artery.

**The left lobe recieves blood from the splenic artery and '''caudal pancreatoduodenal artery'''; a branch of the cranial mesenteric artery.

*Vessels aborize within the connective tissure septa.

**Give off rich capillary networks that surround each acini and invade each islet.

**The endothelium in the exocrine pancreas is continuous, whereas the endothelium of capillaries surrounding the islets in the endocrine pancreas are fenestrated.

*Drained by veins that open into the portal vein.

*The islets recieve ample blood supply to enable an appropriate response to blood glucose level.

==Innervation==

==Innervation==

*Receives sypathetic and parasympathetic supply.

 

**Parasympathetic is supplied by the dorsal vagal trunk.

The pancreas receives sypathetic and parasympathetic supply. The parasympathetic is supplied by the dorsal vagal trunk and the sympathetic is supplied by the solar plexus (splanchnic nerves). Parasympathetic and sympathetic stimulation results in exocytosis and accumulation of secretory vesicles in the lumen and ducts of the acini. Nervous regulation is thought to be of less importance than hormonal control. Hormones that increase pancreatic secretion include: Cholecystokinin (CCK), secretin and gastrin. There is some negative feedback from somatostatin and enkephalins.

**Sympathetic is supplied by the solar plexus (splanchnic nerves).

*Parasympathetic and sympathetic stimulation results in exocytosis and accumulation of secretory vesicles in the lumen and ducts of the acini.

*Nervous regulation is thought to be of less importance than hormonal control.

*Hormones that increase pancreatic secretion:

**Cholecystokinin (CCK)

*There is some negative feedback from somatostatin and enkephalins.

==Lymphatics==

==Lymphatics==

*Blind ending lymphatic vessels drain into larger lymphatic vessels that follow the course of the blood vessels in the connective tissue.  

Blind ending lymphatic vessels drain into larger lymphatic vessels that follow the course of the blood vessels in the connective tissue. Lymph drains into the '''pancreaticoduodenal''' lymph nodes. It then drains into the coeliac centre, which surrounds the coeliac artery.

*Lymph drains into the '''pancreaticoduodenal''' lymph nodes.

*It then drains into the coeliac centre, which surrounds the coeliac artery.

 

==Species Differences==

==Species Differences==

===Carnivore===

===Carnivore===

*Clearly distinguishable as a body and left and right lobes.

 

*Portal vein runs dorsally between the left and right lobes.

Carnivores have a pancreas that is clearly distinguishable as a body and left and right lobes. The portal vein runs dorsally between the left and right lobes. The '''left lobe''' is smaller than the right. The tip of the left lobe contacts the left kidney and lies in the greater omentum. The '''right lobe''' follows the descending duodenum and lies in the mesoduodenum. Dorsally, it is related to the visceral surface of the [[Liver - Anatomy & Physiology|liver]], the ventral surface of the right kidney. Ventrally, it is related to the descending [[Duodenum - Anatomy & Physiology|duodenum]]. Laterally it is related to the ascending [[Colon - Anatomy & Physiology|colon]]. In dogs, both pancreatic and accessory ducts persist throughout development. However, the pancreatic duct is smaller. It joins the bile duct just before opening into the major duodenal papilla which lies 3-6cm distal to the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. The accessory duct is the bigger duct and opens 3-5cm further distal to the pancreatic duct. The two ducts communicate inside the pancreas.

*'''Left lobe''' is smaller than the right.

 

*Tip of the left lobe contacts the left kidney and lies in the greater omentum.

In cats, the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists. Cats normally have pacinian corpuscles in the interlobular tissue and are visible grossly as 1-3cm in diameter. Dogs and cats produce little pancreatic juice between meals, but lots during a meal.

*'''Right lobe''' follows the descending duodenum and lies in the mesoduodenum.

**Dorsally, it is related to the visceral surface of the [[Liver - Anatomy & Physiology|liver]], the ventral surface of the right kidney.

**Ventrally, it is related to the descending [[Duodenum - Anatomy & Physiology|duodenum]].

**Laterally it is related to the ascending [[Colon - Anatomy & Physiology|colon]].

*In dogs, both pancreatic and accessory ducts persist throughout development.

**However, the pancreatic duct is smaller. It joins the bile duct just before opening into the major duodenal papilla which lies 3-6cm distal to the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]].

**The accessory duct is the bigger duct and opens 3-5cm further distal to the pancreatic duct.

***The two ducts communicate inside the pancreas.

*In cats, the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists.

*Cats normally have pacinian corpuscles in the interlobular tissue and are visible grossly as 1-3cm in diameter.

*Dogs and cats produce little pancreatic juice between meals, but lots during a meal.

===Ruminant===

===Ruminant===

*Consists of a distinguishable short body and left and right lobes.

 

*The '''left lobe''' lies in the retroperitoneal space and is in contact with the [[Liver - Anatomy & Physiology|liver]], diaphragm and major vessels dorsally.

The pancreas of a ruminant consists of a distinguishable short body and left and right lobes. The '''left lobe''' lies in the retroperitoneal space and is in contact with the [[Liver - Anatomy & Physiology|liver]], diaphragm and major vessels dorsally. Ventrally, it is in contact with intestines and dorsal sac of the [[Rumen - Anatomy & Physiology|rumen]]. The '''right lobe''' is larger and lies in the mesoduodenum against the flank of the animal and runs part of the length of the descending [[Duodenum - Anatomy & Physiology|duodenum]]. The portal vein passes dorsally at the pancreatic notch between the left and right lobes. In the ox, the distal part of the pancreatic duct atrophies during development, so only the accessory duct persists. The accessory duct enters the duodenum 20 to 25cm distal to the entry of the bile duct. In sheep and goats the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists. It unifies with the bile duct so that both enter via a common duct. There is a constant secretion of pancreatic juice.

**Ventrally, it is in contact with intestines and dorsal sac of the [[Rumen - Anatomy & Physiology|rumen]].

*The '''right lobe''' is larger and lies in the mesoduodenum against the flank of the animal and runs part of the length of the descending [[Duodenum - Anatomy & Physiology|duodenum]].  

*Portal vein passes dorsally at the pancreatic notch between the left and right lobes.

*In the ox, the distal part of the pancreatic duct atrophies during development, so only the accessory duct persists.

**The accessory duct enters the duodenum 20 to 25cm distal to the entry of the bile duct.

*In sheep and goats the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists.

**It unifies with the bile duct so that both enter via a common duct.

*Constant secretion of pancreatic juice.

===Equine===

===Equine===

*Lies mainly on the right, in the very dorsal part of the abdomen.

 

*It is triangular in shape and lies within the sigmoid flexure of the [[Duodenum - Anatomy & Physiology|duodenum]].

The pancreas lies mainly on the right, in the very dorsal part of the abdomen. It is triangular in shape and lies within the sigmoid flexure of the [[Duodenum - Anatomy & Physiology|duodenum]]. The lobes are less distinguishable compared to the dog. The ventral surface is directly attached to the right dorsal [[Colon - Anatomy & Physiology|colon]] and base of the [[Caecum - Anatomy & Physiology|caecum]]. The dorsal surface is directly attached to the right kidney and [[Liver - Anatomy & Physiology|liver]]. The portal vein perforates the pancreas at the '''pancreatic ring'''. Both the pancreatic and accessory ducts persist throughout development. There is a constant secretion of pancreatic juice, which increases after feeding. This provides the caecum and [[Colon - Anatomy & Physiology|colon]] with a constant supply of buffered solution, which maintains a stable environment important for microbe survival.

*Lobes are less distinguishable compared to the dog.

*Ventral surface is directly attached to the right dorsal [[Colon - Anatomy & Physiology|colon]] and base of the [[Caecum - Anatomy & Physiology|caecum]].

*Dorsal surface is directly attached to the right kidney and [[Liver - Anatomy & Physiology|liver]].

*Portal vein perforates the pancreas at the '''pancreatic ring'''.

*Both pancreatic and accessory ducts persist throughout development.

*Constant secretion of pancreatic juice, which increases after feeding. This provides the caecum and [[Colon - Anatomy & Physiology|colon]] with a constant supply of buffered solution, which maintains a stable environment important for microbe survival.

===Porcine===

===Porcine===

==Test yourself with the Pancreas flashcards==

 

==Links==

 

'''Test yourself with the [[Pancreas - Anatomy & Physiology - Flashcards|pancreas Flashcards]]'''

*[[Pancreas - Anatomy & Physiology - Flashcards|Pancreas Flashcards]]

'''Click here for information on [[Pancreas - Histology|histology]]'''

 

 

[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0061.mp4 Pot 61 The Bovine Liver]

*[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0061.mp4 Pot 61 The Bovine Liver]

[[Category:Alimentary System - Anatomy & Physiology]]

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[[Category:Endocrine System - Anatomy & Physiology]]

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