Pancreas: structure, hormones and functions

The pancreas is a vital organ situated in the abdominal region. It performs a crucial function in converting the food we consume into energy that the body's cells can utilize.

The pancreas accomplishes this through its dual role as both an exocrine and endocrine gland. As an exocrine gland, the pancreas produces digestive enzymes and releases them into the small intestine. These enzymes aid in the breakdown of carbohydrates, proteins, and fats present in our food, facilitating their absorption and utilization by the body.The pancreas serves two primary roles within the human body: an exocrine function involved in digestion and an endocrine function responsible for blood sugar regulation.

Location of the Pancreas

The pancreas, an elongated organ, is situated behind the stomach in the upper left abdomen. It is surrounded by neighboring organs such as the small intestine, liver, and spleen. The pancreas has a spongy texture and typically measures around six to ten inches in length. Its shape resembles that of a flat pear or a horizontally extended fish.

The wider portion of the pancreas is referred to as the head, which is positioned closer to the center of the abdomen. Specifically, the head of the pancreas is located at the juncture where the stomach meets the first part of the small intestine. At this juncture, the stomach empties partially digested food into the intestine, while simultaneously, the pancreas releases digestive enzymes into this mixture.

The middle segment of the pancreas is known as the neck or body. It connects the head to the thin end of the pancreas.

Lastly, the slender portion of the pancreas is called the tail, which extends towards the left side of the abdomen.

Pancreas Anatomy

Diagram of the pancreas, and surrounding organs

Anatomically, the pancreas is a vital organ measuring approximately 7 inches in length. The pancreas stretches horizontally across the abdomen and is positioned posteriorly, behind the stomach. The "head" of the pancreas is connected to the duodenum, which is the first part of the small intestine, through a small tube called the pancreatic duct. This duct traverses the entire length of the pancreas, running from the head to the tail.The "tail" of the pancreas is considered the end portion of the organ. It narrows down and extends upward, maintaining a more slender shape compared to the rest of the pancreas.

Structure:

The pancreas is an elongated organ measuring approximately 12-15 cm in length, consisting of three main parts: the head, body, and tail. It is positioned behind the stomach, with the head of the pancreas nestled in the curve of the duodenum. The body and tail of the pancreas extend laterally, and the tail comes into contact with the spleen.

The pancreas is considered a mixed gland because it serves as both an exocrine and endocrine gland. In its exocrine function, the pancreas secretes digestive enzymes into the pancreatic duct. These enzymes are released into the small intestine to aid in the digestion of carbohydrates, fats, and proteins.

As an endocrine gland, the pancreas secretes hormones directly into the bloodstream. However, only about 1% of the total weight of the pancreas is dedicated to its endocrine function. This portion of the pancreas is known as the Islets of Langerhans.

Within the Islets of Langerhans, the adult pancreas contains a variable number of these specialized clusters of cells. The estimated range of Islets of Langerhans in an adult pancreas is between 200,000 to 2,000,000. These islets contain different types of hormone-producing cells, including alpha cells that produce glucagon and beta cells that produce insulin. These hormones play crucial roles in regulating blood sugar levels and maintaining overall metabolic balance.

The endocrine portion of the pancreas consists of specialized clusters of cells called the Islets of Langerhans. These islets are groups of cells within the pancreas that are responsible for the production and release of hormones directly into the bloodstream.

Alpha cell= produce glucagon. The release of glucagon is stimulated by low blood glucose levels, and it plays a crucial role in the regulation of blood sugar.

Beta cell= produce Insulin. The release of insulin is stimulated by elevated blood glucose levels, and it plays a crucial role in the regulation of blood sugar.

Delta cell= produce peptide hormone Somatostatin. Pancreatic somatostatin inhibits the release of both glucagon and insulin.

Somatostatin, also known as GHIH (Growth Hormone-Inhibiting Hormone), is released not only by the hypothalamus but also by the stomach and intestines.

F cell (PP cell)= produce pancreatic polypeptide hormone.

Functions of the Pancreas

A properly functioning pancreas synthesizes and releases the appropriate digestive chemicals in precise amounts and at specific timings to facilitate the digestion of the foods we consume.

Exocrine Function:

The pancreas is equipped with exocrine glands responsible for producing enzymes that play crucial roles in digestion. These enzymes are essential for breaking down various components of food. For protein digestion, the pancreas produces trypsin and chymotrypsin. Amylase, another enzyme secreted by the pancreas, aids in the digestion of carbohydrates. Lipase, on the other hand, is produced by the pancreas to break down fats.

When food enters the stomach, the pancreas releases its pancreatic juices into a network of ducts. These ducts converge into the main pancreatic duct. Additionally, the common bile duct, originating from the liver and gallbladder, combines with the pancreatic duct to form a structure called the ampulla of Vater. This ampulla is located at the initial part of the small intestine, known as the duodenum.

Notably, the common bile duct contributes an important digestive juice called bile. When released into the duodenum, the combination of pancreatic juices and bile assists the body in digesting fats, carbohydrates, and proteins, ensuring effective absorption of nutrients from the food we consume.

Endocrine Function:

The endocrine component of the pancreas comprises clusters of specialized cells known as islet cells or islets of Langerhans. These islet cells play a vital role in hormone production and release, directly into the bloodstream. Among the various hormones produced by the pancreas, two of the primary ones are insulin and glucagon.

Insulin is a pivotal hormone involved in the regulation of blood sugar levels. It acts to lower blood sugar levels by facilitating the uptake of glucose from the bloodstream into cells, particularly in muscles, liver, and adipose (fat) tissue. This uptake of glucose enables cells to utilize it for energy or store it for future use. In addition, insulin facilitates the storage of surplus glucose as glycogen in the liver.

Glucagon, on the other hand, functions to raise blood sugar levels when they become too low. It stimulates the liver to break down glycogen into glucose and release it into the bloodstream, a process known as glycogenolysis. Additionally, glucagon can stimulate gluconeogenesis, the production of new glucose molecules from non-carbohydrate sources like amino acids or glycerol

In summary, the islet cells of the pancreas produce and release hormones, such as insulin and glucagon, which are essential for maintaining proper blood sugar levels. These hormones play a vital role in ensuring the normal functioning of key organs, including the brain, liver, and kidneys.

Hormones of pancreas

1. Glucagon

1. Alpha cells produce, stores and secretes glucagon.
2. Glucagon stimulates glycogenolysis and gluconeogenesis, leading to an increase in blood glucose levels.

2. Insulin

• Beta cell produce, store and secretes insulin.
• Insulin promotes glycogenesis, resulting in a decrease in blood glucose levels. It facilitates the storage of glucose as glycogen in the liver and muscles.
• Insulin function opposite to glucagon and work to maintain normal glucose level in blood.

i. Diabetes mellitus: condition caused by destruction or dysfunction of the beta cells of the pancreas or cellular resistance to insulin that results in abnormally high blood glucose levels.

ii. Hyperglycemia: abnormally high blood glucose levels

iii. Hypoglycemia; abnormally low blood glucose levels.

3. Somatostatin

• inhibit release of both glucagon and insulin
• Somatostatin is a vital hormone with significant inhibitory effects on hormone release. It plays a crucial role in regulating the activity of the gastrointestinal tract and suppressing the rapid proliferation of cells.

Diseases of the Pancreas

The pancreas can be affected by various disorders, including pancreatitis, precancerous conditions like PanIN (Pancreatic Intraepithelial Neoplasia) and IPMN (Intraductal Papillary Mucinous Neoplasm), as well as pancreatic cancer. Each of these disorders presents distinct symptoms and necessitates specific treatments.

Pancreatitis refers to inflammation of the pancreas and can be acute or chronic. Symptoms of pancreatitis typically include severe abdominal pain, nausea, vomiting, and sometimes fever. Treatment may involve pain management, intravenous fluids, and in severe cases, hospitalization.

Precancerous conditions of the pancreas, such as PanIN and IPMN, are characterized by abnormal cellular changes that have the potential to progress to pancreatic cancer. These conditions are often asymptomatic, and they are usually detected incidentally during imaging tests performed for other reasons. Close monitoring and regular surveillance are often recommended to watch for any progression or changes in these conditions.

Pancreatic cancer is an aggressive cancerous tumor that originates in the pancreas. It is often diagnosed at advanced stages due to the lack of early symptoms. However, as the disease progresses, symptoms may include abdominal pain, unexplained weight loss, jaundice (yellowing of the skin and eyes), and digestive issues. Treatment options for pancreatic cancer depend on the stage and may include surgery, chemotherapy, radiation therapy, and targeted therapies.

It's important to note that each disorder affecting the pancreas requires proper diagnosis by a healthcare professional, as symptoms can vary, and treatment plans should be tailored to individual cases. Early detection and prompt medical intervention can significantly impact the prognosis and outcomes for individuals with pancreatic disorders.

Pancreatitis

Pancreatitis is characterized by the inflammation of the pancreas, which arises when the digestive enzymes produced by the pancreas start to damage the organ's own tissues. It can manifest in two forms: acute pancreatitis, which involves sudden and intense pain lasting for a few days, and chronic pancreatitis, a condition that develops gradually and progresses over several years.

In acute pancreatitis, individuals experience severe abdominal pain, often radiating to the back, accompanied by nausea, vomiting, and fever. This condition may be triggered by gallstones, alcohol abuse, certain medications, infections, or other factors. Acute pancreatitis usually requires immediate medical attention, as it can lead to complications such as infection, pancreatic fluid collections, or even pancreatic necrosis. Treatment typically involves supportive measures such as pain management, intravenous fluids, and temporary abstinence from oral intake to allow the pancreas to rest and heal.

Chronic pancreatitis, on the other hand, is a long-term inflammation of the pancreas that progressively damages the organ and impairs its function. Symptoms may include persistent abdominal pain, weight loss, diarrhea, and fatty stool (steatorrhea) due to inadequate digestion and absorption of nutrients. Chronic pancreatitis is often associated with prolonged alcohol abuse, although other causes such as hereditary factors, gallstones, or autoimmune conditions can also contribute. Treatment for chronic pancreatitis focuses on pain management, nutritional support, enzyme replacement therapy to aid digestion, and addressing any underlying causes or complications.

Both acute and chronic pancreatitis require appropriate diagnosis and management by healthcare professionals. Treatment plans are tailored to the individual's specific condition and aim to alleviate symptoms, prevent further damage, and improve overall quality of life.