Chapter 6-7 Bones and Bone Structure

Supporting Connective Tissue: Cartilage

Composed of chondrocytes located in matrix-surrounded spaces called lacunae.
Type of cartilage determined by components of solid, rubbery matrix.
-hyaline cartilage
-elastic cartilage
-fibrous cartilage
Tissue can spring back after being compressed.
Avascular and no nerve supply. Heals slowly.

Mesenchymal cell

adult stem cell from which most connective tissue cells are derived

Osteoblast

a cell that secretes the matrix for bone formation.

Osteoclast

cell that functions in the breakdown and resorption of bone tissue

Osteoprogenitor cell

stem cell whose divisions produce osteoblasts

Osteocyte

a mature bone cell, formed when an osteoblast becomes embedded in the matrix it has secreted.

Collagen

structural protein found in the skin and connective tissue

Sharpey's fibers

secure periosteum to underlying bone

Ossify

to change into bone

Calcify

to harden by forming calcium deposits

Perichondrium

Dense irregular connective tissue membrane covering cartilage; consisting of a cellular layer and a fibrous layer

Appositional growth

growth in width

Interstitial growth

growth in length

Hematopoiesis

production of blood cells

Axial skeleton

the part of the skeleton that includes the skull (cranium, facial bones and ossicles) and vertebral column (including sacrum and coccyx) and sternum and ribs

Appendicular skeleton

Bones of the limbs and limb girdles (pectoral and pelvic girdles) that are attached to the axial skeleton

Long bones

bones that are longer than they are wide; contain a medullary cavity

Diaphysis

shaft of a long bone

Medullary cavity

cavity within the shaft of the long bones filled with bone marrow

Epiphysis

End of a long bone

Epiphyseal line

remnant of the epiphyseal plate, seen in adult bones

Epiphyseal plate

cartilaginous area at the ends of long bones where lengthwise growth takes place in the immature skeleton

Periosteum

a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.

Endosteum

membrane lining the medullary cavity of a bone

Nutrient foramen

Narrow tunnel through the diaphysis that allows blood vessels into the medullary cavity

Red Bone marrow

found in cancellous bone; site of hematopoiesis; where hematocytobasts produces red and white blood cells and platelets

Short bones

carpals and tarsals

Flat bones

These bones are thin, flat, and curved. They form the ribs, breastbone, scapulae, and skull.

Irregular bones

bones of the vertebrae and face, including ossicles and pelvic girdle bones

Compact bone

Hard and dense, but not solid, bone tissue that is beneath the outer periosteum membrane of a bone.

Spongy bone/trabecular bone

Forms most of the interior structure of short, flat, and irregular bones, and the epiphyses of long bones.

Trabeculae

supporting bundles of bony fibers in cancellous (spongy) bone

Bone markings

bones display projections, depressions, and openings that serve as sites of muscle, ligament, and tendon attachment, as joint surfaces, or as conduits for blood vessels

Osteoprogenitor cells

bone stem cells derived from mesenchyme

Osteon

structural & functional unit of compact bone

lamella (bone tissue)

layer of bone tissue

Central canal of osteon

middle of osteon, allows for passage of blood vessels. Every osteon has one central canal

Volkman Canal (Perforating)

canals that carry blood vessels through bone

lacunae

small cavities in bone that contain osteocytes

Canaliculi

a small channel or duct.

Interstitial lamellae

remains of old osteons that broke down as bone grew and remodeled itself

Circumferential lamellae

located deep to periosteum and superficial to endosteum and extend around entire circumference of the diaphysis and resist twisting of long bone

Hydroxyapatites

mineral salts, 65% of bone by mass, Mainly calcium phosphate crystals, Responsible for hardness and resistance to compression

Endochondral bone

bone that begins as hyaline cartilage that is subsequently replaced by bone tissue

Membranous bone

A type of bone that develops by forming on a scaffold of connective tissue.

Endochondral ossification

process in which bone forms by replacing hyaline cartilage

Primary ossification site

forms when a blood vessel enters the rapidly changing cartilage model at the midpoint of the diaphysis

Periosteal bud

A vascular connective tissue bud from the perichondrium that enters the cartilage of a developing long bone and contributes to the formation of a center for ossification.

Secondary ossification centers

this develops in the epiphyses of bone during endochondral ossification; in longer bones is occurs at both ends

Intramembranous ossification

process by which bone forms directly from mesenchymal tissue to produce flat bones of the skull and clavlicle

Proliferation zone

Area of cartilage in the epiphyseal plate that is closest to the end of the bone and is rapidly dividing
More mature cells are closest to the diaphysis. As chondrocytes divide there is an elongation of the epiphysis away from the metaphysis and diaphysis, causing lengthening

Hypertrophic zone

Area with older chondrocytes closer to diaphysis
Cartilage lacunae enlarge and erode, forming interconnecting spaces which will eventually be filled with osteoblasts and osteoid.

Calcification zone

Surrounding cartilage matrix calcifies, chondrocytes die and deteriorate

Ossification zone

Chondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-diaphysis junction
Spicules eroded by osteoclasts
Covered with new bone by osteoblasts
Ultimately replaced with spongy and compact bone

Bone resorption

the breakdown of bone extracellular matrix (minerals and collagen) by osteoclasts that is part of the normal development, maintenance, remodeling, and repair of bone tissue

Parathyroid hormone (PTH)

raises blood calcium level

Calcitonin

Lowers blood calcium levels

Wolff's law

Wolff's law, developed by the German anatomist and surgeon Julius Wolff states that bone in a healthy person or animal will adapt to the loads under which it is placed. Regular loading of bones (e.g. through exercise, running, weight-lifting etc.) will cause trabeculae to remodel and for bone to become more dense. The reverse is also true. Sedentary lifestyles can lead bone to remodeling to become less dense and more brittle. "Use it or lose it" - the body is being efficient with bone-building which requires energy.

Fractures

a crack or break in a bone

Hematoma

a solid swelling of clotted blood within the tissues.

Fibrocartilaginous callus

a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of a bone within 3 weeks after the injury

Bony callus

this forms during fracture repair when the fibrocartilage is converted to woven and then spongy bone; lasts 3-4 months

Bone remodelling

The continuous turnover of bone matrix and mineral that involves first, an increase in resorption and osteoclast activity, and later, active bone formation by osteoblast activity.

Osteomalacia

abnormal softening of bones in adults; disease marked by softening of the bone caused by calcium and vitamin D deficiency

Rickets

osteomalacia in children; causes bone deformity

Osteoporosis

loss of bone density due to the slowing down of osteoblasts; usually as a result of less stimulation (e.g. sedentary behaviour, reduced estrogen/testosterone hormone levels; reduced flow of oxygenated blood - due to age and/or smoking; poor nutritional intake)

Osteosarcoma

malignant tumor of the bone

Osteoid

unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

Hematocytoblast

blood developing stem cell (forming each type of blood cells)