Gastrointestinal Physiology and Nutrition

These flashcards define key terms in gastrointestinal endocrinology, nutritional metabolic rates, nitrogen balance, protein deficiency states, and the physiological value of local foodstuffs.

Enteroendocrine Cells (EECs)

Specialized cells lining the gut mucosa that sense the luminal environment and secrete diverse hormones with local (paracrine) and systemic (endocrine) actions.

Gastrin

A hormone sourced from G cells in the stomach antrum that stimulates gastric acid ($HCl$) secretion by parietal cells and promotes the growth of gastric mucosa.

Cholecystokinin (CCK)

A hormone from I cells in the duodenum/jejunum that stimulates gallbladder contraction and pancreatic enzyme secretion while inducing satiety.

Secretin

A hormone sourced from S cells in the duodenum that stimulates pancreatic bicarbonate ($HCO_3^-$) secretion to neutralize acidic chyme and protect duodenal mucosa.

Glucose-Dependent Insulinotropic Polypeptide (GIP)

An incretin hormone from K cells that stimulates insulin release from pancreatic beta cells in a glucose-dependent manner and inhibits gastric acid secretion.

Glucagon-Like Peptide-1 (GLP-1)

A hormone from L cells in the ileum/colon that has a strong incretin effect, inhibits glucagon secretion, and promotes satiety.

Peptide YY (PYY)

A hormone from L cells that helps regulate food intake by inhibiting gastric motility and acid secretion, a process known as the 'ileal brake'.

Somatostatin

A regulatory peptide from D cells that inhibits the release of many other GI hormones including gastrin, CCK, and secretin.

Kilocalorie (kcal)

The standard unit of energy in nutrition where $1\,kcal=1000\,cal=4184\,J$. Fats yield $9\,kcal/g$ while proteins and carbohydrates yield $4\,kcal/g$.

Basal Metabolic Rate (BMR)

The minimum energy expended per unit time at rest in a post-absorptive state under thermoneutral conditions to maintain essential functions like circulation and respiration.

Thermic Effect of Food (TEF)

The energy expended to digest, absorb, and metabolize nutrients, accounting for approximately $10\%$ of daily energy expenditure.

Direct Calorimetry

A method of measuring metabolic rate by determining the amount of heat produced by the body within a specially designed chamber.

Indirect Calorimetry

A method of estimating energy expenditure by measuring oxygen consumption ($\dot{V}O_2$) and carbon dioxide production ($\dot{V}CO_2$).

Respiratory Quotient (RQ)

The ratio of $\dot{V}CO_2/\dot{V}O_2$; values are approximately $0.7$ for lipids, $0.8$ for proteins, and $1.0$ for carbohydrates.

Weir Equation

The formula used to estimate metabolic rate: $\text{Energy Expenditure (kcal/min)} = (3.94 \times \dot{V}O_2) + (1.11 \times \dot{V}CO_2)$.

Nitrogen Balance

The difference between total nitrogen intake (primarily from dietary protein) and total nitrogen excretion in urine, faeces, and sweat.

Positive Nitrogen Balance

A state of net anabolism where nitrogen intake exceeds excretion, occurring during growth, pregnancy, or recovery from injury.

Negative Nitrogen Balance

A state of net catabolism where nitrogen excretion exceeds intake, seen in starvation, severe illness, or trauma.

Essential Amino Acids (EAAs)

The nine amino acids that the human body cannot synthesize and must obtain from the diet: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine.

Kwashiorkor

A form of malnutrition caused by primary protein deficiency with adequate calorie intake, characterized by edema, skin lesions, and a distended abdomen.

Marasmus

A severe deficiency of both calories and protein resulting in total body wasting, muscle atrophy, and emaciation.

Ghrelin

An orexigenic hormone secreted by the stomach when empty that stimulates appetite via hypothalamic neurons.

Leptin

A hormone produced by adipocytes that inhibits hunger by acting on the arcuate nucleus of the hypothalamus.

Hepcidin

A liver-derived hormone that regulates iron homeostasis by inhibiting ferroportin to reduce iron export from cells.

Bioavailability

A measure of how much of a specific nutrient from a food source the body can actually absorb and utilize.

Phytochemicals

Non-nutrient bioactive compounds found in plants, such as saponins and flavonoids, which provide health benefits like antioxidant or anti-inflammatory properties.

Ugu (Telfairia occidentalis)

A local Nigerian green leafy vegetable containing saponins and flavonoids, traditionally used for its blood-boosting and antioxidant properties.