Bone structure

calcium homeostasis, microscopic & macroscopic structures

Calcium homeostasis

• osseous tissue maintains calcium balance

Blood calcium concentration

• maintained at 2.5 mM

Hypocalcemia

• blood concentration is too low

• parathyroid glands secrete parathyroid hormones in order to raise Ca2+ levels

BONE EFFECT

• stimulates osteoclast activity

• bone tissue is dissolved

• Ca 2+ released to blood

KIDNEY EFFECT

• renal tubules reabsorb more Ca2+ for blood so less is excreted for urine

• kidney produces more vitamin D, vit D goes into blood circulation, and goes to small intestine so it can absorb more calcium from food

Hypercalcemia

• blood calcium is too high and calcium-phosphate crystals can damage kidney, heart, and blood vessels

• thyroid senses rising levels, and releases calcitonin

BONE EFFECT

• inhibits osteoclast activity, so less ca2+ is released

KIDNEY EFFECT

• renal tubules reabsorb less Ca 2+, so more calcium goes into urine

Osteon

structural unit of osseous tissue

Haversian (central) canal

center osteon that contains blood and lymphatic vessels

perforating canal/Volkmann’s canal

runs horizontally through osteon, connecting central canal to other central canals

contains blood, lymphatic vessels, and nerves

Osteocytes

cells in bone tissue

makes more bone tissue

Osteoclasts

cells in bone tissue

dissolves osseous tissue’s ECM

Osteoblasts

cells in bone tissue

makes bone tissue grow, and can become an osteocyte

spongy texture (microscopic)

trabecula(e) is a small sheet of osseous tissue that makes the spongy texture

compact texture

the part surrounding inside of osseous tissue in macrostructure

List macroscopic structures

proximal/distal epiphysis, proximal/distal metaphysis, diaphysis, epiphyseal plate, periosteum, red bone marrow, yellow bone marrow

yellow bone marrow

fat tissue

found in middle of macroscopic structure

red bone marrow

found at bottom and top of internal macroscopic structure