Chapter 7

Question 1

What is osteology?

Answer 1

The study of bone.

Osteology is the study of bone.

Question 2

What is the skeletal system composed of?

Answer 2

Bones, cartilages, and ligaments.

The skeletal system is composed of bones, cartilages, and ligaments.

Question 3

What is the function of cartilage in the skeletal system?

Answer 3

Cartilage is the forerunner of most bones and covers many joint surfaces of mature bone.

Question 4

What do ligaments do in the skeletal system?

Answer 4

Ligaments hold bones together at the joints.

Question 5

What is the function of tendons in the skeletal system?

Answer 5

Tendons attach muscle to bone.

Question 6

What is aponeurosis?

Answer 6

Aponeurosis is a thin flatten sheet of dense regular CT.

Aponeurosis is a thin flatten sheet of dense regular CT.

Question 7

What are the functions of the skeleton?

Answer 7

Support, protection, movement, electrolyte balance, acid-base balance, and blood formation.

The functions of the skeleton include support, protection, movement, electrolyte balance, acid-base balance, and blood formation.

Question 8

What is bone (osseous tissue)?

Answer 8

Bone is connective tissue with the matrix hardened by calcium phosphate and other minerals.

Bone is connective tissue with the matrix hardened by calcium phosphate and other minerals.

Question 9

What is mineralization or calcification?

Answer 9

The hardening process of bone.

Mineralization or calcification is the hardening process of bone.

Question 10

What are the general features of flat bones?

Answer 10

Flat bones protect soft organs and are curved but wide and thin.

Flat bones protect soft organs and are curved but wide and thin.

Question 11

What are the general features of long bones?

Answer 11

Long bones are longer than wide and act as rigid levers for muscle action.

Long bones are longer than wide and act as rigid levers for muscle action.

Question 12

What are the general features of short bones?

Answer 12

Short bones are equal in length and width, allowing them to glide across one another in multiple directions.

Short bones are equal in length and width, allowing them to glide across one another in multiple directions.

Question 13

What are the general features of irregular bones?

Answer 13

Irregular bones have elaborate shapes that do not fit into other categories.

Irregular bones have elaborate shapes that do not fit into other categories.

Question 14

What is compact (dense) bone?

Answer 14

Compact bone is the outer shell of a long bone.

Compact bone is the outer shell of a long bone.

Question 15

What is the diaphysis?

Answer 15

The diaphysis is the cylinder of compact bone that provides leverage in a long bone.

The diaphysis is the cylinder of compact bone that provides leverage in a long bone.

Question 16

What is the medullary cavity?

Answer 16

The medullary cavity is the space in the diaphysis of a long bone that contains bone marrow.

The medullary cavity is the space in the diaphysis of a long bone that contains bone marrow.

Question 17

What are epiphyses?

Answer 17

Epiphyses are the enlarged ends of a long bone, which strengthen joints and attach ligaments and tendons.

Epiphyses are the enlarged ends of a long bone, which strengthen joints and attach ligaments and tendons.

Question 18

What is metaphysis?

Answer 18

Metaphysis is the area between the diaphysis and epiphysis of a long bone.

Metaphysis is the area between the diaphysis and epiphysis of a long bone.

Question 19

What is spongy (cancellous) bone?

Answer 19

Spongy bone is covered by more durable compact bone and makes up one-fourth of the skeleton by weight.

Spongy bone is covered by more durable compact bone and makes up one-fourth of the skeleton by weight.

Question 20

What is articular cartilage?

Answer 20

Articular cartilage is a layer of hyaline cartilage that covers the joint surface where one bone meets another, allowing for friction-free movement.

Articular cartilage is a layer of hyaline cartilage that covers the joint surface where one bone meets another, allowing for friction-free movement.

Question 21

What are nutrient foramina?

Answer 21

Nutrient foramina are minute holes in the bone surface that allow blood vessels to penetrate.

Nutrient foramina are minute holes in the bone surface that allow blood vessels to penetrate.

Question 22

What is periosteum?

Answer 22

Periosteum is the external sheath that covers bone except where there is articular cartilage.

Periosteum is the external sheath that covers bone except where there is articular cartilage.

Question 23

What is endosteum?

Answer 23

Endosteum is the thin layer of reticular connective tissue lining the marrow cavity.

Endosteum is the thin layer of reticular connective tissue lining the marrow cavity.

Question 24

What is an epiphyseal plate?

Answer 24

The epiphyseal plate is an area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis, enabling growth in length.

The epiphyseal plate is an area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis, enabling growth in length.

Question 25

What is diploe?

Answer 25

Diploe is the spongy layer in the cranium that absorbs shock, with marrow spaces lined by endosteum. ## Footnote Diploe is the spongy layer in the cranium that absorbs shock, with marrow spaces lined by endosteum.

Question 26

What are the four principal types of bone cells?

Answer 26

Osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts. ## Footnote The four principal types of bone cells are osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts.

Question 27

What are osteoprogenitor cells?

Answer 27

Osteoprogenitor cells are stem cells found in endosteum, periosteum, and central canals that give rise to new osteoblasts. ## Footnote Osteoprogenitor cells are stem cells found in endosteum, periosteum, and central canals that give rise to new osteoblasts.

Question 28

What are osteoblasts?

Answer 28

Osteoblasts are bone-forming cells that line up under the endosteum and periosteum to form osteoid. ## Footnote Osteoblasts are bone-forming cells that line up under the endosteum and periosteum to form osteoid.

Question 29

Osteoprogenitor cells

Answer 29

Stem cells found in endosteum, periosteum, and in central canals ## Footnote Arise from embryonic mesenchymal cells; multiply continuously to produce new osteoblasts

Question 30

Osteoblasts

Answer 30

Bone-forming cells ## Footnote Line up as single layer of cells under endosteum and periosteum; Forms osteoid-semisolid bone matrix; Nonmitotic; Synthesize soft organic matter of matrix which then hardens by mineral deposition; Become entrapped within the matrix

Question 31

Osteocytes

Answer 31

Former osteoblasts that have become trapped in the matrix they have deposited ## Footnote Lacunae—tiny cavities where osteocytes reside; Canaliculi—little channels that connect lacunae; Cytoplasmic processes reach into canaliculi; Maintain the bone matrix by signaling osteoblast; When stressed, produce biochemical signals that regulate bone remodeling; Contribute to homeostatic mechanism of bone density and calcium and phosphate ions

Question 32

Osteoclasts

Answer 32

Bone-dissolving cells found on the bone surface ## Footnote Osteoclasts develop from same bone marrow stem cells that give rise to blood cells; Different origin from rest of bone cells; Unusually large cells formed from the fusion of several stem cells; Typically have 3 to 4 nuclei, may have up to 50

Question 33

Matrix of osseous tissue

Answer 33

By dry weight, about one-third organic and two-thirds inorganic matter ## Footnote Organic matter—synthesized by osteoblasts; Inorganic matter: 85% hydroxyapatite (crystallized calcium phosphate salt), 10% calcium carbonate, Other minerals (fluoride, sodium, potassium, magnesium); Harden matrix

Question 34

Spongy Bone

Answer 34

Spongelike appearance ## Footnote Spongy bone consists of: Slivers of bone called spicules, Thin plates of bone called trabeculae, Spaces filled with red bone marrow; No osteons; Provides strength with minimal weight; Trabeculae develop along bone’s lines of stress

Question 35

Bone Marrow

Answer 35

General term for soft tissue that occupies the marrow cavity of a long bone and small spaces amid the trabeculae of spongy bone ## Footnote Red marrow (myeloid tissue): In nearly every bone in a child; Hemopoietic tissue—produces blood cells; Yellow marrow found in adults: Most red marrow turns into fatty yellow marrow; No longer produces blood

Question 36

What is bone composed of?

Answer 36

Multiple tissues in a delicate, but intricate arrangement that is an organ to itself ## Footnote –In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

Question 37

What is yellow marrow found in adults?

Answer 37

Most red marrow turns into fatty yellow marrow ## Footnote –No longer produces blood

Question 38

What is ossification or osteogenesis?

Answer 38

The formation of bone ## Footnote Example: Bone develops through ossification or osteogenesis.

Question 39

How does bone develop in the human fetus and infant?

Answer 39

Bone develops by two methods: Intramembranous ossification and Endochondral ossification ## Footnote Example: In the human fetus and infant, bone develops through Intramembranous and Endochondral ossification.

Question 40

What bones are produced through intramembranous ossification?

Answer 40

Flat bones of the skull, clavicle, and mandible ## Footnote Example: Intramembranous ossification produces flat bones like the skull and clavicle.

Question 41

What happens during endochondral ossification in infancy and childhood?

Answer 41

The epiphyses fill with spongy bone, and cartilage is limited to the articular cartilage and the epiphyseal plate ## Footnote Example: Endochondral ossification in infancy and childhood involves the filling of epiphyses with spongy bone.

Question 42

What is the epiphyseal plate?

Answer 42

A region of transition from cartilage to bone where bones elongate ## Footnote Example: The epiphyseal plate functions as a growth zone for bone elongation.

Question 43

What is appositional growth?

Answer 43

The process where bones increase in width throughout life by deposition of new bone at the surface ## Footnote Example: Appositional growth involves the deposition of new bone at the surface to increase bone width.

Question 44

What is bone remodeling?

Answer 44

The process of repairing microfractures, releasing minerals into the blood, and reshaping bones in response to use and disuse ## Footnote Example: Bone remodeling occurs throughout life to repair microfractures and reshape bones.

Question 45

How is calcium homeostasis regulated?

Answer 45

Calcium homeostasis depends on a balance between dietary intake, urinary and fecal losses, and exchanges between osseous tissue ## Footnote Example: Calcium homeostasis is regulated by dietary intake, losses, and exchanges between tissues.

Question 46

What are the three hormones that regulate calcium homeostasis?

Answer 46

Calcitriol, calcitonin, and parathyroid hormone ## Footnote Example: Three hormones involved in regulating calcium homeostasis are Calcitriol, calcitonin, and parathyroid hormone.

Question 47

What is Calcitriol?

Answer 47

Calcitriol is a form of vitamin D produced by the skin, liver, and kidneys. ## Footnote Calcitriol behaves as a hormone that raises blood calcium concentration.

Question 48

What is the function of Calcitriol?

Answer 48

Calcitriol increases calcium absorption by the small intestine, increases calcium resorption from the skeleton, and promotes kidney reabsorption of calcium ions. ## Footnote Calcitriol is necessary for bone deposition.

Question 49

What is Calcitonin?

Answer 49

Calcitonin is secreted by C cells of the thyroid gland when calcium concentration rises too high. ## Footnote Calcitonin lowers blood calcium concentration by inhibiting osteoclast activity and stimulating osteoblasts to deposit calcium into the skeleton.

Question 50

What is the function of Parathyroid Hormone (PTH)?

Answer 50

Parathyroid hormone (PTH) is secreted by the parathyroid glands and raises calcium blood levels by stimulating osteoclast activity, promoting calcium reabsorption by the kidneys, enhancing the calcium-raising effect of calcitriol, and inhibiting bone deposition. ## Footnote PTH is released with low calcium blood levels.

Question 51

What factors affect bone growth?

Answer 51

At least 20 or more hormones, vitamins, and growth factors affect osseous tissue. Bone growth is rapid in puberty and adolescence due to surges of growth hormone, estrogen, and testosterone. ## Footnote Girls grow faster than boys and reach full height earlier.

Question 52

What are the types of bone fractures?

Answer 52

There are stress fractures caused by abnormal trauma to a bone and pathological fractures in bones weakened by disease. Fractures can be classified by structural characteristics like the direction of the fracture line, presence of skin break, and number of pieces. ## Footnote Fractures can result from falls, athletics, and military combat.

Question 53

What is the process of healing fractures?

Answer 53

The process of healing fractures involves hematoma formation, soft callus formation, hard callus formation, and bone remodeling. ## Footnote Osteoblasts deposit a temporary bony collar around the fracture to unite the broken pieces while ossification occurs.

Question 54

Hard callus formation

Answer 54

Osteoblasts deposit a temporary bony collar around the fracture to unite the broken pieces while ossification occurs. ## Footnote Example sentence: The hard callus formation is essential for stabilizing the fracture.

Question 55

Bone remodeling

Answer 55

Small bone fragments are removed by osteoclasts, while osteoblasts deposit spongy bone and then convert it to compact bone. ## Footnote Bone remodeling is a crucial process in the healing of fractures.

Question 56

Soft callus formation

Answer 56

Deposition of collagen and fibrocartilage converts granulation tissue to a soft callus. ## Footnote Soft callus formation precedes hard callus formation in the bone healing process.

Question 57

Osteoporosis

Answer 57

Severe loss of bone density. Bones lose mass and become brittle due to loss of organic matrix and minerals. Subject to pathological fractures of hip, wrist, and vertebral column. Kyphosis (widow’s hump) is a deformity of the spine due to vertebral bone loss. ## Footnote Osteoporosis is more common in postmenopausal women.

Question 58

Estrogen maintains density in both sexes; inhibits resorption by osteoclasts

Answer 58

Testes and adrenals produce estrogen in men. In women, rapid bone loss occurs after menopause. Osteoporosis is common in young female athletes with low body fat causing them to stop ovulating and ovarian estrogen secretion is low. ## Footnote Estrogen plays a crucial role in maintaining bone density.

Question 59

Treatments for osteoporosis

Answer 59

Estrogen replacement therapy (ERT) slows bone resorption, but increases the risk of breast cancer, stroke, and heart disease. Drugs Fosamax and Actonel destroy osteoclasts. PTH slows bone loss if given as a daily injection. Forteo (PTH derivative) increases density by 10% in 1 year and promotes bone growth. The best treatment is prevention through exercise and a good diet. ## Footnote Prevention is key in managing osteoporosis.