HUMAN MEDICAL BIOLOGY, ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 7. THE NUTRITIONAL PROCESS AND ITS PATHOLOGY

ANATOMY AND PHYSIOLOGY OF THE DIGESTIVE ORGANS

CARBOHYDRATE METABOLISM

CARBOHYDRATES are classified into complex and simple. Complex carbohydrates include Polysaccharides (starch and Glycogen) and Disaccharides (lactose, beet sugar, cane sugar), whereas simple carbohydrates include Monosaccharides (glucose, fructose, galactose). Carbohydrates enter the body with food in the form of polysaccharides and disaccharides. In the gastrointestinal tract, they are broken down into monosaccharides, which are absorbed into the bloodstream. Glucose is oxidized into carbon dioxide and Water with the release of energy. The combustion of 1 g of carbohydrates yields 3.75 kcal of energy. Humans derive the largest amount of energy from carbohydrates because we consume them in greater quantities (300-400 g per day) than Proteins and fats. Furthermore, Brain Neurons rely exclusively on glucose for energy.

The normal Blood sugar level ranges from 4.44-6.66 mmol/L. A condition where this level drops below 4.44 mmol/L is called hypoglycemia, while an increase above 6.66 mmol/L is termed hyperglycemia. In hypoglycemia (when the glucose level drops to 2.8 mmol/L), the Functions of Nerve Cells are impaired first, potentially leading to loss of consciousness and convulsions.

When an excessive amount of sugar (150-200 g) enters the body, its blood level rises sharply, leading to alimentary or dietary hyperglycemia. However, the Kidneys quickly begin to excrete the excess sugar, glucose appears in the urine (glucosuria), and the Blood Glucose Level rapidly normalizes.

Monosaccharides absorbed in the intestine are carried by the bloodstream to The Liver and Muscles, where some of them are converted into glycogen. Glycogen serves as the body's carbohydrate reserve. On average, up to 350 g of it is stored. When blood sugar levels drop (due to physical or excessive emotional stress), glycogen is broken down into glucose and released into the bloodstream. Glycogen synthesis is stimulated by Insulin, a hormone produced by the Pancreas. In Diabetes Mellitus, glycogen formation decreases, blood sugar levels rise, and a significant amount of it is excreted in the urine. Diabetes mellitus is treated by administering insulin.

The hormone insulin lowers blood glucose levels. All Other Hormones that regulate Carbohydrate METABOLISM are insulin antagonists, meaning they increase blood glucose levels. These include Glucagon (a pancreatic hormone), glucocorticoids (Adrenal Cortex Hormones), thyroxine (a thyroid hormone), somatotropin (an anterior pituitary hormone), and adrenaline (a hormone of The adrenal medulla).