Bio 168 Chapter 6 The Skeletal System

Hyaline Cartilage

Provides support flexibility and resilience. contains collagen fibers only. covers areas of bone that is part of a movable joint; costal, articular, respiratory & nasal

Elastic Cartilage

Similar to hyaline cartilage, but contains elastic fibers; ear epiglottis

Fibrocartilage

Thick collagen fibers: has great tensile strength; Menisci of knee; vertebral discs

Compact bone

Dense outer layer on every bone that appears smooth and solid

Diaphysis

Tubular shaft that forms long axis of bone. consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults

epiphysis

ends of long bones that consists of compact bone externally and spongy bone internally

spongy bone

Made up of a honey comb of small needle-like or flat pieces of bone called trabeula. Open spaces between trabecula are filled with red or yellow marrow

Articular Cartilage

Covers articular (joint) surface

Periosteum

White, double layered membrane that covers external surface except joints

Endosteum

Covers inside portion of compact bone. covers trabeculae of spongy bone.. lines canals that pass through compact bone

Osteogenic layer

Inner layer abutting bone and contains primitive osteogenic sterm cells that gives rise to most all bone cells

Red Marrow

Found within trabecular cavities of spongy bone and diploe of flat bones, such as sternum.

Yellow marrow

can convert to red marrow if a person become anemic

Osteogenic cells

Mitotically active stem cells in periosteum and endosteum. when stimulated they differentiate into osteoblasts or bone-lining cells.

osteoblasts

Bone-forming cells that secrete unmineralized bone matrix called osteoid.. Osteoblasts are activiely mitotic

Osteocytes

Mature bone cells in lacunae that no longer divide. Maintain bone matrix and acts as stress or strain sensor

Bone-lining cells

Flat cells on bone surface believed to also help maintain matrix

Osteoclasts

Deprived from same hematopoietic stem cells that become macrophages. Giant, multinucleate cells functions in bone resorption(break down of bone)

Osteon (Haversian system)

Consists of an elongated cylinder that runs parallel to long axis bone. Consists of several rings of bone matrix called lamellae

Interstital Lamellae

some fill gaps between forming osteons others are remnants of osteons cut by bone remodeling

Circumferential lamellae

these layers of lamellae extend around entire surface of diaphysis. help long bones to resists twisting

Organic components

include all five bone cells. consists of ground substance and collagen fibers. which contribute to high tensile strength and flexibility of bone

Inorganic components

make up 65% of bone mass. responsible for hardness and resistance to compression

endochondral ossification

Bone forms by replacing hyaline cartilage, Bones are called (endochondral) bones, forms most of skeleton

Intramembranous ossification

Bone develops from fibrous membrane, Bones called membrane bones,Forms flat bones, e.g. clavicles and cranial bones

resting zone

area of cartilage on epiphyseal side of epiphyseal plate that is relatively inactive

Proliferation zone

are of cartilage on diaphysis side of epiphyseal plate that is rapidly dividing new cells are formed move upward causing lengthening

Hypertrophic zone

Cartilage lacunae enlarge and erode, forming interconnecting spaces

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 are then eroded by osteoclasts and are covered with new bone by osteoblasts

Wolff's Law of bone

states that bones grow on remodel in response to demands place on them

Hematoma formation

torn blood vessels hemorrhage forming mass of clotted blood

Fibrocartilagenous Callus formation

capillaries grow into hematoma. Phagocytic cells clear debris. fibroblasts secrete collgen fibers to span break and connect broken ends

Bony callus formation

new trabeculae appear in fibrocartilaginous callus. callus is converted to bony (hard) callus of spongy bone

Bone remodeling

Excess material on diaphysis exterior and within medullary cavity is removed compact bone is laid down to reconstruct shaft walls

osteomalacia

Bones are poorly maineralized. osteoid is produced, but calcium salts not adequately deposited. results soft weak bones, only in adults

Rickets

Results in bowed legs and other bone deformities because bones ends are enlarged abnormally long.

cause: vitamin D deficiency

only in children

osteoporosis

A group of disorders in which bone resorption exceeds deposit

Wolff's Law of bone

states that the architecture of a bone is determined by the mechanical stresses placed upon it, and the bone thereby adapts to withstand those stresses

Hematopoiesis

formation of blood cells

Canaiculi

Hairlike canals that connect lacunae to each other and the central canal

Projections

sites of muscle and ligament attachment

surfaces

Help form joints

depressions or openings

serves as a passageway for vessels and nerves

Haversian (central) canal

central channel containing blood vessels and nerves

Volkman's (perforating) canal

connects canals of osteons with blood vessels; occur at right angles to central canal

lacunae

small cavities in bone that contain osteocytes

What are the inorganic components of bone

hyrdoxyapatites (mineral salts), largely calcium phosphates

sacrifical bonds

• in or between collagen molecules

-stretch and break easily on impact to dissipate energy and prevent fracture

-bond reform- if no trauma

appositional growth

increase in bone thickness; width

interstitial Growth

Chondrocytes divide and secrete new matrix, expanding cartilage from within

testosterone and estrogen (sex hormones) promote what

a growth spurt

Paget's disease

a bone disease of unknown cause characterized by the excessive breakdown of bone tissue, followed by abnormal bone formation

perforating fibers

secure periosteum to underlying bone

seven functions of bone

support, protection, anchorage, mineral storage, blood cell formation, triglyceride storage, hormone production

axial skeleton

skull, vertebral column, rib cage

appendicular skeleton

Bones of the limbs and limb girdles that are attached to the axial skeleton

bones are classsifed by what

location and shape

Calcification

process that hardens bones by adding calcium phosphate and collagen

diploe

spongy bone in flat bones