LO2 Pancreas

Pancreas Overview

  • Unique Structure: The pancreas has both endocrine and exocrine tissues.

    • Majority as Exocrine Gland: Functions primarily in digestion (for more information see Chapter 21, Digestive System).

    • Minority as Endocrine Gland: Small percentage serves crucial endocrine l / functions.

Anatomical Location

  • The pancreas is located behind the stomach.

    • Head: Tucked into the curve of the duodenum (beginning of the small intestine).

    • Tail: Extends to the spleen.

Pancreatic Islets (Islets of Langerhans)

  • Contains 1 to 2 million pancreatic islets, constituting only approximately 2% of all pancreatic tissue.

  • Types of Cells in Islets:

    • Alpha Cells: Secrete glucagon.

    • Beta Cells: Secrete insulin.

    • Delta Cells: Secrete somatostatin.

Role of the Pancreas in Blood Glucose Regulation

  • The body maintains steady blood glucose levels.

    • Too low: Insufficient fuel for cells.

    • Too high: Triggers disorders such as autoimmune disease and pancreatitis.

Alpha Cells

  • Function: Secrete glucagon.

    • Condition: Released when blood glucose levels fall between meals.

    • Action: Stimulates liver to convert glycogen into glucose and converts fatty acids and amino acids into glucose (gluconeogenesis).

    • Outcome: Increases blood glucose levels.

Beta Cells

  • Function: Secrete insulin.

    • Condition: Elevated glucose and amino acid levels post-meal.

    • Action: Stimulates absorption of both nutrients by cells.

    • Outcome: Decreases blood glucose levels.

Delta Cells

  • Function: Secrete somatostatin.

    • Role: Inhibits the release of glucagon and insulin; regulates other pancreatic endocrine cells.

    • Additional Effect: Inhibits the release of growth hormone.

Regulation of Blood Glucose

  • Hormonal Interaction: Insulin and glucagon have opposite effects to maintain normal blood glucose ranges.

    • Post-Meal Scenario:

    • Blood glucose rises.

    • Beta cells release insulin, stimulating:

      • Cells to uptake glucose.

      • Liver to store glucose as glycogen.

    • Result: Blood glucose returns to normal levels.

    • Starvation Scenario:

    • Blood glucose drops below a certain threshold.

    • Alpha cells release glucagon:

      • Stimulates liver to break down glycogen into glucose, raising blood glucose levels.

Clinical Insight: Diabetes Mellitus

  • Prevalence: Over 37 million Americans (11% of the population) have diabetes; an additional 96 million have prediabetes.

  • Health Consequence: In 2021, diabetes was the seventh leading cause of death, with over 100,000 related deaths.

Mechanisms of Diabetes Mellitus

  • Insufficient insulin or reduced insulin receptors prevent glucose from entering cells, leading to hyperglycemia.

  • Classic Signs of Diabetes:

    • Glycosuria: Excess glucose spills into urine due to overwhelmed kidneys.

    • Polyuria: Increased urine production as kidneys expel excess glucose.

    • Polydipsia: Excessive thirst due to dehydration from polyuria.

    • Polyphagia: Increased hunger due to cells being deprived of glucose despite high blood levels.

Effects of Untreated Diabetes

  • Metabolism Shift: Body burns proteins and fats for energy leading to:

    • Fatigue

    • Weight loss

    • Production of ketone bodies causing acidosis.

  • Complications: Damage to blood vessels and nerves leading to:

    • Heart attacks, strokes, vision impairment, and reduced limb circulation.

    • Common complications include kidney disease.

Types of Diabetes Mellitus

Type 1 Diabetes: No insulin

  • Age of Onset: Before age 30.

  • Rate of Onset: Rapid.

  • Demographics: Around 10% of diabetics.

  • Cause: Autoimmune attack on beta cells; insulin deficiency.

  • Treatment: Daily insulin (injections or pumps).

Type 2 Diabetes: Insulin resistance

  • Age of Onset: Usually after age 40.

  • Rate of Onset: Gradual.

  • Demographics: About 90% of diabetics.

  • Cause: Insulin resistance; inadequate insulin production exacerbated by factors such as obesity and inactivity.

  • Treatment: Lifestyle modifications; if uncontrolled, may require oral medicines or insulin.

Routine Screening and Signs of Diabetes

  • Checking Methods:

    • Urinalysis for glucose.

    • Inquiry about “three polys”: polyuria, polydipsia, and polyphagia.

Understanding the “Three Polys”

  • Polyuria: Excessive urination ("much urine").

  • Polydipsia: Excessive thirst ("drinking much").

  • Polyphagia: Excessive eating ("much, or excessive eating").

Gestational Diabetes

  • Affecting about 10% of pregnant women.

  • Often resolves post-birth but can lead to type 2 diabetes in 50% of cases.

Cardiovascular and Nerve Damage from Diabetes

  • Statistics: 60-70% of diabetic individuals experience some degree of nerve damage.

  • Common Effect Areas: Legs and feet - loss of sensation leading to untreated injuries potentially causing serious complications.

Effects of Chronic Hyperglycemia

  • Vascular damage to small to medium-sized blood vessels.

  • Thickening of vascular walls, diminished blood flow leading to nerve ischemia and dysfunction.

Aging Effects on the Endocrine System

  • Sensitivity of target tissues to hormones may decline with age.

  • Some key observations include:

    • Thyroid: Decreases in hormone secretion and metabolism.

    • Parathyroid: Alters levels contributing to osteoporosis.

    • Insulin: Diminished sensitivity after age 50 leads to increased fasting blood glucose levels.

    • Growth Hormone: Decreased secretion leading to reduced muscle mass and increased fat storage.