A&P 6: Bones & Skeletal Tissue

Question 1

Skeletal cartilage

Answer 1

made of some variety of cartilage tissue molded to fit its body location and function

Question 2

Hyaline cartilages

Answer 2

provide support with flexibility and resistance; most abundant skeletal cartilages; chondrocytes are spherical; only fiber type in matrix is fine collagen (undetectable microscopically); includes articular, costal, respiratory, and nasal cartilages

Question 3

Elastic cartilages

Answer 3

more stretch elastic than hyaline cartilages and so are better able to stand up to repeated bending; found in only 2 skeletal locations - the external ear and the epiglottis

Question 4

Fibrocartilages

Answer 4

highly compressible with great tensile strength; consist of roughly parallel rows of chondrocytes alternating with thick collagen fibers; occur in sites subjected to both pressure and stretch (padlike cartilages (menisci) of knee and the discs between vertebrae)

Question 5

Appositional growth

Answer 5

“growth from outside”; cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue

Question 6

Interstitial growth

Answer 6

“growth from inside”; the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within

Question 7

Axial skeleton

Answer 7

forms the long axis of the body; includes the bones of the skull, vertebral column, and rib cage; protect, support, or carry other body parts

Question 8

Appendicular skeleton

Answer 8

consists of the bones of the upper and lower limbs and the girdles (shoulder bones and hip bones) that attache the limbs to the axial skeleton

Question 9

Long bones

Answer 9

bones that are considerably longer than they are wide; has a shaft plus 2 ends which are often expanded; all limb bones except the patella, wrist, and ankle bones are this type

Question 10

Short bones

Answer 10

bones that are roughly cube shaped; example: bones of the wrist/ankles

Question 11

Sesamoid bones

Answer 11

“shaped like a sesame seed”; special type of bone that form in a tendon (ex. patella); vary in size and number in different individuals; some act to alter the direction of pull of a tendon

Question 12

Flat bones

Answer 12

bones that are thin, flattened, usually a bit curved; ex: sternum, scapulae, ribs, and most skull bones

Question 13

Irregular bones

Answer 13

bones with complicated shapes that fit no class; ex. vertebrae, hip bones

Question 14

Hematopoiesis

Answer 14

blood cell formation; mostly occurs in the red marrow cavities of certain bones

Question 15

Compact bone

Answer 15

external layer of bone; dense, looks smooth, solid

Question 16

Spongy bone

Answer 16

AKA trabecular bone; internal to compact bone, a honeycomb of small needle-like or flat pieces (trabeculae)

Question 17

Trabeculae

Answer 17

“little beams”; small needle-like or flat pieces in spongy bone

Question 18

Diploe

Answer 18

in flat bones, the spongy bone is called this, which means “folded”

Question 19

Diaphysis

Answer 19

tubular shaft that forms the long axis of a typical long bone

Question 20

Medullary cavity

Answer 20

diaphysis is constructed of a relatively thick collar of compact bone that surrounds a central _________ ______; in adults, it contains fat (yellow marrow)

Question 21

Yellow marrow cavity

Answer 21

in adults, the medullary cavity contains fat and is called this

Question 22

Epiphyses

Answer 22

ends of long bones; in many cases, are broader than the diaphysis

Question 23

Epiphyseal line

Answer 23

between the diaphysis and each epiphysis of an adult long bone is this, a remant of the epiphyseal plate

Question 24

Epiphyseal plate

Answer 24

disc of hyaline cartilage that grows during childhood to lengthen the bone

Question 25

Periosteum

Answer 25

glistening, white double-layered membrane that covers the external surface of the entire bone except the joint surfaces; outer fibrous layer, osteogenic layer

Question 26

Nutrient foramina

Answer 26

periosteum is richly supplied with nerve fibers and blood vessels which pass through the shaft to enter the marrow cavity via these “openings”; perforating (Sharpey’s) fibers secure the periosteum to the underlying bone

Question 27

Endosteum

Answer 27

“within the bone”; delicate, connective tissue membrane which covers internal bone surfaces

Question 28

Red marrow

Answer 28

hematopoietic tissue, typically found within the trabecular cavities of spongy bone of long bones and in the diploe of flat bones

Question 29

Red marrow cavities

Answer 29

trabecular & diploe cavities often called this

Question 30

Bone markings

Answer 30

serve as sites of muscle, ligament, and tendon attachment, as joint surfaces, or as conduits for blood vessels and nerves; those that are depressions and openings include fossae, sinuses, foramina (sing = foramen), and grooves - allow nerves/blood vessels to pass; projections (project outward) = heads, trochanters, spines, etc)

Question 31

Osteogenic (osteoprogenitor) cells

Answer 31

mitotically active stem cells found in the membranous periosteum and endosteum; in growing bones = flattened/squamous cells; when stimulated, differentiate into osteoblasts or bone lining cells, while others persist as is

Question 32

Osteoblasts

Answer 32

bone-forming cells that secrete the bone matrix; actively mitotic; unmineralized bone matrix they secrete includes collagen (90% of bone protein) and calcium-binding proteins that make up the initial unmineralized bone (osteoid); also play a role in matrix calcification

Question 33

Osteocytes

Answer 33

spidery, mature bone cells that occupy spaces (lacunae) that conform to their shape; monitor and maintain the bone matrix; act as stress/strain sensors and respond to mechanical stimuli (bone loading, bone deformation, weightlessness)

Question 34

Bone lining cells

Answer 34

flat cells found on bone surfaces where bone remodeling is not going on; thought to help maintain the matrix; on the external bone surface, AKA periosteal cells; those lining internal surfaces AKA endosteal cells

Question 35

Osteoclasts

Answer 35

derived from the same hematopoietic stem cells that differentiate into macrophages; giant multi-nucleate cells located at sites of bone resorption; rest in a shallow depressions called a resorption bay when actively breaking down (resorbing) bone; exhibit a distinctly ruffled border which directly contacts the bone (increase surface area for enzymatically degrading the bones and seal off that area from the surrounding matrix)

Question 36

Osteon (Haversian system)

Answer 36

structural unit of compact bone; each = elongated cylinder oriented parallel to the long axis of the bone; tiny, weight-bearing pillars

Question 37

Lamella

Answer 37

“little plate”; a layer, such as of bone matrix in an osteon of compact bone

Question 38

Lamellar bone

Answer 38

AKA compact bone

Question 39

Central (Haversian) Canal

Answer 39

running through the core of each osteon is this canal, containing small blood vessels and nerve fibers that serve the osteon’s cells

Question 40

Perforatin (Volkmann’s) Canals

Answer 40

canals that lie at right angles to the long axis of the bone and connect the blood and nerve supply of the periosteum to those in the central canals and the medullary cavity

Question 41

Lacunae

Answer 41

spider-shaped osteocytes occupy these at the junctions of the lamellae

Question 42

Interstitial lamellae

Answer 42

lying between intact osteons are incomplete lamellae; either fill the gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling

Question 43

Circumferential lamellae

Answer 43

located just deep to the periosteum, just superficial to the endosteum; extend around the entire circumference of the diaphysis, effectively resist twisting of the long bone

Question 44

Osteoid

Answer 44

organic part of bone matrix; makes up 1/3 of the matrix, includes ground substance (composed of proteoglycans and glycoproteins) and collagen fibers, both of which are made and secreted by osteoblasts; contribute to a bone’s structure and to the flexibility and tensile strength that allow it to resist stretch and twisting

Question 45

Ossification

Answer 45

AKA osteogenesis; process of bone formation

Question 46

Cartilage (endochondral) bone

Answer 46

bone developed by replacing hyaline cartilage (via endochondral ossification)

Question 47

Membrane bone

Answer 47

in intramembranous ossification, a bone develops from a fibrous membrane

Question 48

Endochondral ossification

Answer 48

essentially all bones below the base of the skull (except the clavicle) form by this process

Question 49

Primary Ossification Center

Answer 49

formation of a long bone typically begins in the center of the hyaline cartilage shaft at a region called this

Question 50

Periosteal bud

Answer 50

collection of elements which contain a nutrient artery and vein, nerve fibers, red marrow elements, osteogenic cells, and osteoclasts; invades the forming cavities to form spongy bone

Question 51

Secondary ossification centers

Answer 51

shortly before or after birth, these appear in one or both epiphyses, and the epiphyses gain bony tissue

Question 52

Intramembranous ossification

Answer 52

forms the cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles; most bones formed by this process are flat bones

Question 53

Bone remodeling

Answer 53

bone deposit & bone resorption

Question 54

Parathyroid hormone (PTH)

Answer 54

hormonal control of remodeling; produced by the parathyroid glands

Question 55

Calcitonin

Answer 55

produced by parafollicular cells (C cells) of the thyroid gland, may be involved in hormonal control of remodeling, though to a lesser extend than PTH

Question 56

Fractures

Answer 56

breaks in bones

Question 57

Hematoma

Answer 57

mass of clotted blood; forms at the fracture site in bones

Question 58

Fibrocartilaginous callus

Answer 58

entire mass of repair tissue that splints the broken bone

Question 59

Bony (hard) callus

Answer 59

new bone trabeculae appear in the fibrocartilaginous callus and gradually convert it to this; formation continues until a firm union forms about 2 months later

Question 60

Osteomalacia

Answer 60

“soft bones”; includes a number of disorders in which the bones are poorly mineralized; osteoid is produced, but calcium salts are not adequately deposited, so bones are soft and weak; main symptom is pain

Question 61

Rickets

Answer 61

like osteomalacia, but in children and much more severe; bowed legs, deformities of the pelvis, skull, and rib cage are common; epiphyseal plates cannot calcify (so continue to widen) and the ends of long bones become visibly enlarged and abnormally long

Question 62

Osteoporosis

Answer 62

refers to a group of diseases in which bone resorption outpaces bone deposit; bones become fragile, have tendency to break much more easily than normal; composition of the matrix remains normal, but bone mass declines, and the bones become porous and light

Question 63

Paget’s disease

Answer 63

characterized by excessive and haphazard bone deposit and resorption; has an abnormally high ratio of spongy bone to compact bone