Fluid Balance, Micronutrients, and Innate Immune Effector Cells

Vocabulary practice flashcards covering fluid balance dynamics, micronutrient biochemistry and deficiency treatments, and innate immune effector cell functions.

Extracellular Fluid (ECF) Solute Composition

The fluid compartment outside cells where the primary cation is $Na^+$ and the primary anions are $Cl^-$ and $HCO_3^-$.

Intracellular Fluid (ICF) Solute Composition

The fluid compartment inside cells where the primary cation is $K^+$ and the primary anion is $HPO_4^{2-}$.

Hydrostatic Pressure Gradient

The force exerted by fluid on cells that tends to push water away from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure.

Osmotic Pressure Gradient

The force exerted by solutes in a solution that pulls water toward the solution with higher solute concentration (higher osmotic pressure) via osmosis.

Normal Body Fluid Osmolarity

The osmotic concentration maintained across all body fluids under normal conditions, which is approximately $300\,\text{mOsmoles/L}$.

Crenation

The shrinking of a cell that occurs when hypertonic plasma draws water out of the cytosol and interstitial fluid into the plasma by osmosis.

Vasopressin (ADH)

A hormone produced in the hypothalamus and released from the posterior pituitary that inserts aquaporins into distal tubule and collecting duct cells of the kidney to increase water reabsorption.

Aldosterone

A hormone that promotes $Na^+$ reabsorption and retention in the kidney, causing water to follow by osmosis, which increases blood volume and decreases urine output.

Fluid Balance in Diarrhoea

An initial state of isosmotic fluid loss where both water and solutes are lost from the ECF, decreasing ECF volume and arterial blood pressure without changing ECF osmolarity or ICF volume.

Oral Rehydration Therapy (ORT)

A solution consisting of water, sugar, salt ($Na^+$ and $K^+$), anions ($Cl^-$), a base (acetate or bicarbonate), and glucose designed to promote fluid uptake during diarrhoea.

Sodium-Driven Glucose Cotransporter (SGLT1)

An enterocyte membrane symporter protein that simultaneously binds $Na^+$ and glucose to transport them into the cell, creating an osmotic gradient that drives passive water reabsorption.

Micronutrient

An essential organic or inorganic chemical element or compound needed by the body in small amounts (typically milligrams or less than $100\,\mu\text{g/day}$) that cannot be synthesized by the body.

Water-Soluble Vitamins

Nine organic essential nutrients in humans (including B-type vitamins and Vitamin C) that are not stored in the body, are excreted in urine when in excess, and commonly act as coenzymes in metabolism.

Coenzyme

A loosely bound, detachable organic cofactor that functions as a carrier of chemical groups or electrons between molecules during enzymatic reactions.

Prosthetic Group

A non-detachable cofactor that is tightly bound to a protein and necessary for its biological activity, such as the iron-containing haem group permanently bound to hemoglobin.

Nicotinamide Adenine Dinucleotide ($NAD^+$)

A metabolic coenzyme synthesized from Vitamin B3 (Niacin) that consists of two nucleotides (adenine and nicotinamide) and serves as an electron carrier in redox reactions.

Retinoids

Dietary forms of Vitamin A (including $\beta$-carotene, retinal, retinol, and retinoic acid) that maintain intestinal barrier integrity and control enterocyte brush border enzymes like lactase and sucrase.

Zinc Supplementation in Diarrhoea Treatment

The administration of $20\,\text{mg/day}$ of zinc for 10–14 days alongside ORT to restore gut mucosal integrity, stimulate antibody production, and act directly on ion channels.

Respiratory Burst

A metabolic pathogen-killing process in phagocytes where oxygen is converted via NADPH oxidase, superoxide dismutase, and peroxidase into toxic free radicals like hydroxyl radicals, hypochlorite ions, and hypobromite ions.

Neutrophil Extracellular Traps (NETs)

Extruded DNA structures released by neutrophils to physically trap pathogens when the cell is unable to resolve an infection on its own.

Pyogenic Organisms

Microorganisms that induce pus formation, where pus consists of dead and dying neutrophils together with viable organisms.

Reticulo-Endothelial System Macrophages

Long-lived tissue-specific monocytes, including Kupffer cells in the liver, microglial cells in the brain, alveolar macrophages in the lung, and osteoclasts in bone.

Myeloid Dendritic Cells

Highly effective professional antigen-presenting cells that circulate in very low numbers ($< 0.01\%$) as immature cells lacking high $B7$ ($CD80/86$) expression before maturing in tissues.

Missing Self Hypothesis

The mechanism governing Natural Killer (NK) cell activation, where NK cells target and kill host cells that have downregulated surface MHC Class I molecules due to viral infection or tumor transformation.

B1 B Cells

Innate-like B lymphocytes residing in the pericardium, peritoneum, and pleural surfaces that produce thymic-independent natural antibodies (predominantly $IgM$) against antigens such as blood groups.

Natural Killer T (NKT) Cells

A specialized subset of T cells lacking a variable T-cell receptor that recognize non-peptide antigens (such as lipids bound to $CD1d$ and carbohydrates) to secrete pro-inflammatory cytokines.

Basophils and Mast Cells

Immune granulocytes that bind $IgE$ antibodies to defend against parasitic infections and trigger allergic reactions upon subsequent antigen exposure by releasing stored granules.

Eosinophils

Granulocytic immune cells that arrive later at sites of inflammation to mediate the late-phase effects of basophil and mast cell activation.