Nutrition: Nutrients Essential to Healthy Tissues and Osteoporosis

Vocabulary practice flashcards covering Chapter 9: Nutrients Essential to Healthy Tissues (blood, bone, and connective tissue) and In Depth 9.5: Osteoporosis.

Erythrocytes

Red blood cells that constitute approximately $45\%$ of whole blood volume and are responsible for transporting oxygen throughout the body.

Leukocytes

White blood cells that constitute less than $1\%$ of blood volume (along with platelets) and play a key role in immune defense.

Platelets

Cell fragments found in the blood that assist in blood clotting and wound closure.

Plasma

The watery extracellular fluid matrix of blood, constituting about $55\%$ of total blood volume, in which cellular elements and platelets are suspended.

Hemoglobin

The oxygen-carrying protein found in red blood cells that binds about two-thirds of the body's total iron.

Myoglobin

An iron-containing protein similar to hemoglobin found in muscle cells that binds and stores oxygen.

Microcytic red blood cells

Abnormally small red blood cells resulting from insufficient hemoglobin synthesis, commonly caused by low levels of iron, copper, vitamin A, or vitamin $B_6$.

Macrocytic red blood cells

Abnormally large red blood cells that develop when precursor stem cells fail to divide properly due to low folate or vitamin $B_{12}$.

Ceruloplasmin

A copper-containing transport protein in the blood that is critical for the proper metabolism and systemic transport of iron.

Phylloquinone

The dietary plant form of fat-soluble vitamin K, found predominantly in green leafy vegetables and vegetable oils.

Menaquinone

The animal and bacterial form of fat-soluble vitamin K produced by normal microflora in the human large intestine.

Collagen

A fibrous structural protein found extensively in bone, teeth, tendons, blood vessels, and gum tissue; requires vitamin C for synthesis and maintenance.

Scurvy

The classic deficiency disease of vitamin C, characterized by bleeding gums, loose teeth, failure of wounds to heal, swollen joints, bone pain, fractures, and depression.

Cortical bone (compact bone)

A very dense bone tissue that forms the tough outer layer of all bones and many small bones, making up $80\%$ of the human skeleton.

Trabecular bone (spongy bone)

A porous, lattice-like internal bone tissue that provides scaffolding to support cortical bone, accounts for $20\%$ of the skeleton, and has a faster turnover rate.

Bone modeling

The developmental process by which bones are shaped and sculpted to determine size and geometry, largely completed by early adulthood following puberty.

Bone remodeling

The continuous, lifelong two-step physiological cycle in which mature bone tissue is removed by resorption and replaced by new bone formation.

Osteoclasts

Specialized bone cells that break down and erode bone surfaces during the resorption phase of bone remodeling.

Osteoblasts

Bone-forming cells that secrete and lay down the new collagen-containing organic matrix of bone.

Dual-energy x-ray absorptiometry (DXA)

A low-level, noninvasive x-ray scanning procedure used to measure bone mineral density across the whole body or at peripheral sites such as the hip or spine.

T-score

A statistical score generated by DXA testing that compares an individual's bone mineral density to the average peak bone density of a healthy 30-year-old adult.

Parathyroid hormone (PTH)

A hormone released by the parathyroid glands in response to low blood calcium that activates vitamin D, stimulates renal calcium retention, and triggers osteoclastic bone resorption.

Calcitonin

A hormone secreted by the thyroid gland when blood calcium levels are elevated; it suppresses osteoclasts and limits calcium reabsorption in the kidneys and intestines.

Bioavailability

The extent to which an ingested nutrient is digested, absorbed across the intestinal tract, and made available for physiological use by the body.

Fluorosis

A condition caused by excessive fluoride intake during development that produces porous, stained, and pitted dental enamel.

Calcitriol

The fully active hormonal form of vitamin D ($1, 25\text{-dihydroxyvitamin } D_3$), produced by enzymatic conversion in the kidneys after initial processing in the liver.

Rickets

A deficiency disease in children resulting from inadequate vitamin D, causing soft, poorly mineralized bones that bend under body weight to cause bowed legs.

Osteomalacia

Adult vitamin D deficiency characterized by defective bone mineralization, significant loss of bone mass, and increased bone fragility.

Osteoporosis

A skeletal disorder characterized by low bone mass, architectural deterioration of bone matrix, and increased susceptibility to fractures.

Kyphosis

An abnormal outward curvature of the thoracic spine resulting in hunching (dowager's hump), commonly caused by compression fractures of osteoporotic vertebrae.

Peak bone density

The point of maximal bone mass and structural strength achieved during the human lifespan, typically reached around age 30 before age-related loss begins.

Hypercalcemia

An abnormally elevated concentration of calcium in the blood, which may result from malignancies, hyperparathyroidism, or excessive vitamin D supplementation.

Hypomagnesemia

A condition characterized by abnormally low blood magnesium concentrations, presenting with muscle spasms, cramps, nausea, weakness, and secondary hypocalcemia.