Chapter 7 Bone Tissue

skeletal system

organ system consisting of bones, cartilage, and ligaments

osteology

study of bone

cartilage

tough, flexible connective tissue covering most bones and joints

ligaments

attach bone to bone

tendons

attach muscle to bone

support

bones support the body

protection

bones can enclose and protect structures

movement

produced by the action of muscles on the bones

electrolyte balance

skeleton stores calcium and phosphate ions, releasing them as needed

acid-base balance

bone tissue buffers the blood against excessive pH changes by absorbing or releasing alkaline phosphate and carbonate salts

blood formation

bone marrow produces red blood cells and immune system cells

hormone secretion

bone cells secrete hormones that influence the secretion and action of insulin and moderate the stress response

osseous tissue

connective tissue where matrix is hardened

mineralization/calcification

hardening process of the bone by the deposition of calcium phosphate and other minerals

bone

organ composed of osseous tissue, blood, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue

flat bones

bones with form of thin curved plates

long bones

bones longer than they are wide and serve as a lever producing major body movements

compact/dense/cortical bone

dense outer shell of osseous tissue

marrow/medullary cavity

space within bones containing bone marrow

spongy/cancellous bone

ends of bones where central space is more loosely organized

diaphysis

shaft of the bone providing leverage

epiphysis

head of the bone strengthening joints and surface area for tendons and ligaments

epiphyseal line

slightly denser spongy bone between epiphysis and diaphysis often seen in more mature bones

articular cartilage

hyaline cartilage at joint surfaces to enable joint movement

nutrient foramina

small holes in the in bone that blood vessels go through

periosteum

layer off fibrous collagen connective tissue covering surface of a bone and inner osteogenic layer providing strong attachment and continuity from muscle to tendon to bone, does not cover articular cartilage

perforating fibers

collagen fibers that penetrate into the bone matrix

endosteum

thin layer of reticular connective tissue that lines the internal marrow cavity, the surfaces of spongy bone, and canal system found throughout compact bone

diploe

spongy layer in the cranium that can absorb impact if compact bone fractures, both surfaces of flat bone covered in periosteum and marrow spaces in the spongey bone are lined with endosteum

osteogenic cells

stem cells found in endosteum and inner layer of periosteum from embryonic mesenchyme and multiply continuously creating osteoblasts

inner and outer tables

sandwich compact bone of flat bones

osteoblasts

bone forming cells in endosteum and inner layer of the periosteum, stress stimulates osteogenic cells to increase the number of osteoblasts which reinforce bone

osteogenesis/ossification

formation of bone, synthesize soft organic matter of matrix and promote its mineralization

osteocytes

former osteoblasts that have become trapped in the matrix the deposited, they reach into canaliculi and contact processes of neighboring cells gap junction allowing for passage of nutrients; some reabsorb bone matrix while other deposit it; act as strain sensors producing biochemical signals that regulate bone remodeling

lacunae

tiny cavities where osteocytes reside

canaliculi

little channels that connect lacunae

osteocalcin

hormone secreted by osteoblasts and osteocytes, part of stress response stimulating insulin, inc insulin sensitivity, and promote energy availability

osteoclasts

bone-dissolving cells found on bone surface that develop from bone marrow cells that make RBC, large cells that are formed from fusing several stem cells

osteolysis

breakdown of bone as part of bone remodeling done by osteoclasts

ruffled border

infoldings increasing the surface area of osteoclasts on bone facing side

resorption bays

pits osteoclasts etch into bone surface, often found reside there

composition of osseous tissue matrix

dry weight 1/3 organic, 2/3 inorganic matter

organic matter

synthesized by osteoblasts and consists of collagen and carbohydrate-protein complexes —> ex. glycosaminoglycans, proteoglycans, and glycoproteins

inorganic matter

mineral component of osseous tissue matrix; 85% hydroxyapatite, 10% calcium carbonate, inorganic ions creating composite material that provides flexibility and strength

hydroxyapatite

crystallized calcium phosphate salt

Rickets

disease caused by mineral deficiency and resulting in soft, deformed bones

sacrificial bonds

bonds that break under stress and dissipate shock under load in collagen molecules

osteogenesis imperfecta/brittle bone disease

results from a defect in collagen deposition

concentric lamellae

layers of matrix surrounding a central/haversian canal running longitudinally; collagen corkscrews in helical arrangement down each lamella in opposite directions enhancing strength

osteon/haversian system

central canal and its lamellae

perforating canals

connect central canals

cement line

separates osteons and prevents spread of microfractures

circumferential lamella

found encircling inner and outer region of dense bone

interstitial lamellae

fill irregular regions between osteons

spicules

lattice of bone slivers covered in endosteum in spongy bone

trabeculae

plates covered with endosteum in spongey bones, form along bone’s line of stress

spongy bone matrix

arranged in lamellae with few osteons and no central canals and all osteocytes are close to bone marrow

bone marrow

soft tissue occupying marrow cavities of long bones and small spaces of spongy bone

red bone marrow/myeloid tissue

contains multiple tissues, in every bone in a child and in adults in the skull, vertebrae, ribs, sternum, pelvic gridle, and proximal heads of humorous and femur

hematopoietic tissue

tissue that produces blood cells; found in red bone marrow

yellow bone marrow

found in adults, fatty marrow that does not produce blood, can transform back into red marrow in event of chronic anemia

intramembranous ossification

produces flat bones of the skull, clavicle, and mandible

1. Deposition of osteoid tissue into embryonic mesenchyme

2. Calcification of osteoid tissue and entrapment of osteocytes

3. Honeycomb of spongy bone with developing periosteum

4. Filling of space to form compact bone at surfaces, leaving spongy bone in middle

important in lifelong thickening and remodeling of long bones

mineralization/mineral deposition

calcium, phosphate, and other ions taken from the blood plasma and deposited in bone tissue as hydroxyapatite, osteoblasts lay down collagen which become encrusted with minerals creating seed crystals that attract more ions

ectopic ossification

abnormal calcification of tissues

calculus

calcified mass over a soft organ

mineral resorption

process of dissolving bone, release minerals into the blood, done by osteoclasts that respond to dec levels of calcium in tissue fluid

calcium

99% in bones, needed for neuron communication, muscle contraction, blood clotting, exocytosis

hypocalcemia

calcium deficiency cause excess excitability of nerves causing muscle spasms/inability of muscles to relax, can close off airway and cause suffocation

hypercalcemia

excess calcium decrease nerve sensitivity causing muscle weakness, sluggishness, potential cardiac arrest

osteomalacia

bone-softening, vitamin D deficiency disease of usually elderly adults

calcitriol

behaves as a hormone, form of vitamin D produced by the skin, liver, and kidneys that raises blood calcium concentration by increasing calcium absorption by small intestine, skeleton, and kidneys

calcitonin

produced by parafollicular (clear, C) cells of the thyroid gland, secreted when blood calcium concentration rises too high, lowers by osteoclast inhibition and osteoblast stimulation

osteoclast inhibition

mechanism where calcitonin reduces osteoclast activity so they liberate less calcium from the skeleton

osteoblast stimulation

mechanism where calcitonin increases the number and activity of osteoblasts and deposit calcium into the skeleton

parathyroid hormone

secreted by parathyroid glands and attached to the surface of the thyroid, raises calcium by stimulating osteoclast population, reabsorption by the kidneys, synthesize calcitriol, and prevents collagen synthesis by osteoblasts

endochondral ossification

bone develops from hyaline cartilage; method produces most bones of the body (limbs, vertebrae, ribs, sternum, scapula, pelvic girdle)

1) Mesenchyme form early hyaline cartilage model

2) formation of primary ossification center, bony collar, and periosteum

3) vascular invasion, formation of primary marrow cavity, and appearance of secondary ossification center

4) bone at birth contains enlarged marrow cavity and secondary marrow cavity in one epiphysis

5) bone of child contains epiphyseal plate

6) adult bone contains a single marrow cavity and close epiphyseal plate

metaphysis

transitional zone on each side of the epiphyseal plate where cartilage is replaced by bone

zone of reserve cartilage

typical histology of resting hyaline cartilage

zone of cell proliferation

chondrocytes multiply and line up in rows of small flattened lacunae

zone of cell hypertrophy

cessation of mitosis; enlargement of chondrocytes and thinning of lacuna walls

zone of calcification

temporary calcification of cartilage matrix between columns of lacunae

zone of bone deposition

breakdown of lacuna walls, leaving open channels; death of chondrocytes; bone deposition by osteoblasts, forming trabeculae of spongy bone

interstitial growth

cartilage growth from within

achondroplastic dwarfism

long bones stop growing in childhood; results in normal torso, short limbs; failure of cartilage growth in metaphysis, spontaneous mutation produces mutant dominant allele

pituitary dwarfism

lack of growth hormone, normal proportions with short stature

appositional growth

deposition of new tissue at the bone surface causing growth in diameter and thickness

Wolff’s law of bone

architecture of bone determined by mechanical stresses placed on it