Nutrition Chapter 9

RDA for Calcium

1,000 mg / day

Cortical Bone

- Compact Bone. - Dense bone tissue that makes up outer surface of all bones as well as entirety of most small bones of body.

Trabecular Bone

- Spongy Bone. - Porous bone tissue that makes up only 20% of skeleton & is found within ends of long bones, inside spinal vertebrae, inside flat bones, & inside bones of pelvis.

Hypocalcemia

1. Condition characterized by abnormally low concentration of calcium in blood.

Hypercalcemia

1. Condition marked by an abnormally high concentration of calcium in blood. 2. Can be caused by cancer & overproduction of PTH.

Vitamin D

1. Does not always need to come from diet. 2. Considered a hormone because it is made in one part of body yet regulates various activities in other parts.

Symptoms of Hypercalcemia

1. Fatigue. 2. Loss of appetite. 3. Constipation. 4. Mental Confusion.

Parathyroid Hormone (PTH)

1. Hormone secreted by parathyroid gland when blood calcium levels fall. 2. Increases blood calcium levels by stimulating activation of vitamin D, increasing reabsorption of calcium from kidneys, & stimulating osteoclasts to break down bone, which releases more calcium into bloodstream.

Calcitonin

1. Hormone secreted by thyroid glad when blood calcium levels are too high. 2. Inhibits actions of vitamin D, preventing reabsorption of calcium in kidneys, limiting calcium absorption in small intestine, & inhibiting osteoclasts from breaking down bone.

Calcium

1. Major mineral that is required in diet in amounts greater than 100mg/day. 2. Most abundant major mineral in bodies, comprising about 2% of entire body weight.

Symptoms of Hypocalcemia

1. Muscle Spasms. 2. Convulsions.

Functions of Calcium

1. Provide structure to bones & teeth. 2. Maintenance of healthy blood pressure. 3. Initiation of blood clotting. 4. Regulation of various hormones & enzymes. 5. Assist in muscle contraction. 6. Critical in normal transmission of nerve impulses.

Remodeling

1. Two-step process by which bone tissue is recycled. 2. Includes breakdown of existing bone & formation of new bone.

Osteoclasts

Cells that erode surface of bones by secreting enzymes & acids that dig grooves into bone matrix.

Osteoblasts

Cells that prompt the formation of new bone matrix by laying down the collagen-containing component of bone, which is then mineralized.

T-Score

Comparison of individual's bone density to the average peak bone density of 30-year-old healthy adult.

Calcium Tetany

Condition in which muscles experience twitching & spasms as result of inadequate blood calcium levels.

Foods Rich in Calcium

Dairy, Greens, & Vegetables

Bone Density

Degree of compactness of bone tissue, reflecting strength of bones.

Bioavailability

Degree to which our body can absorb & utilize any given nutrient.

Bone Modeling

Determination of bone shape.

Bone Growth

Determination of bone size.

Calcium Rigor

Failure of muscles to relax, which leads to hardening or stiffening of muscles caused by high levels of blood calcium.

T-Score Between -1 & -2.5

Low bone mass & increased risk for fractures.

Dual Energy X-Ray Absorptiometry (DXA or DEXA)

Most accurate tool for measuring bone density.

T-Score Between +1 & -1

Normal bone density.

T-Score More Negative than -2.5

Osteoporosis

Peak Bone Density

Point at which bone is strongest, because they are at highest density.

Resorption

Process by which the surface of bone is broken down by osteoclasts.

Collagen

Protein that forms strong fibers in bone & connective tissue.