Anatomy & Physiology Chapter 6

Front 1

condition of porous bones due in large part to depletion of calcium

Back 1

osteoperosis

Front 2

disorder in which bones fail to calcify

Back 2

rickets and osteomalacia

Front 3

degeneration of articular cartilage such that the bony ends touch; the resulting friction of bone against bone worsens the condition.
Usually associated with the elderly

Back 3

osteoarthritis

Front 4

bone cancer that primarily affects osteoblasts and occurs most often in teenagers during their growth spurt; the most common sites are the metaphysis if the thigh bone (femur), the shin bone (tibia), and the arm bone (humerous).
Metastese occur most often in lungs; treatment consists of mutidrug chemotherapy and removel of the malignant growth or apmutation of the limb

Back 4

osteogenic sarcoma

Front 5

an infection of the bone characterized by high fever, sweating chills, pain and nausia, pus formation, edema, and warmth over the affected bone and rigid overlying muscles.

Back 5

osteomylitis

Front 6

reduced bone mass due to a decrease in the rate of bone synthesis to a level too low to compensate for normal bone resorption; any decrease in bone mass below normal.
Ex: osteoperosis

Back 6

osteopenia

Front 7

- shaft or long part.

Back 7

Diaphysis

Front 8

- ends of the bone.

Back 8

Epiphyses

Front 9

- where the shaft joins epiphyses. This is where new bone is laid down to lengthen bone at the epiphyseal plate which becomes the epiphyseal line when bone stops lengthening.

Back 9

Metaphyses

Front 10

- covers the bones at joints to reduce friction. Repair of damage is limited because it lacks a perichondrium.

Back 10

Articular cartilage

Front 11

- tough membrane around the outside of bone. It contains cells that make bone increase in diameter. - serves in repair and nutrition of bone.

Back 11

Periosteum

Front 12

- space inside of the diaphysis and contains fatty yellow marrow.

Back 12

Medullary (marrow) cavity

Front 13

- thin membrane lining the marrow cavity and contains cells that break down and build up bone.

Back 13

Endosteum

Front 14

-is composed primarily of calcium salts that provide the hardness to the bone. Is also composed of collagen fibers which make it less brittle. Like reinforcing rods in concrete, they provide tensile strength.

Back 14

Matrix

Front 15

- unspecialized stem cells that can divide to make bone forming cells (osteoblasts).

Back 15

Osteogenic cells

Front 16

-the bone-forming cells - secrete matrix.

Back 16

Osteoblasts

Front 17

-former bone-building cells that are trapped in the matrix. They are supplied with blood and continue to survive.

Back 17

Osteocytes

Front 18

-serve to break down bone (resorption). Are important in maintenance and repair of bone.

Back 18

Osteoclasts

Front 19

- forms the external layers of all bones. it is relatively strong. -release a lipid-rich, water-repellent secretion.

Back 19

Compact bone

Front 20

- the individual, somewhat circular, units that make up bone.

Back 20

Osteons

Front 21

- run longitudinally and contain blood & lymph vessels, as well as nerves.

Back 21

Central (Haversian) canals

Front 22

- rings of hard calcified matrix.

Back 22

Concentric lamellae

Front 23

- small spaces that contain osteocytes.

Back 23

Lacunae

Front 24

- small canals that carry nutrients and wastes between the osteocytes and central canal, and from one osteocyte to another osteocyte.

Back 24

Canaliculi

Front 25

- carries blood and lymph vessels, and nerves into bone transversely.

Back 25

Perforating (Volkman’s) canal

Front 26

- areas between osteons.

Back 26

Interstitial lamellae

Front 27

occurs in epiphyses of long bones, lines their medullary cavities, and makes up most of the other bones.
1. Consists of a latticework of more or less cylindrical trabeculae.
2. Spaces in between these can contain red bone marrow. 3. Trabeculae do not contain osteons but have lacunae and canaliculi that get blood from surrounding cavities.

Back 27

Spongy bone

Front 28

enter diaphysis through perforating (Volkmann’s) canals and service the periosteum and outer compact bone.

Back 28

Periosteal arteries and veins, as well as nerves,

Front 29

pass into the medullary cavity of the diaphysis through the nutrient foramen and service internal areas up to the epiphyseal plates.114

Back 29

Nutrient artery & vein

Front 30

service red bone marrow and bone tissue of their respective regions.

Back 30

Metaphyseal and epiphyseal arteries and veins

Front 31

- is the process by which bone forms.

Back 31

Ossification (osteogenesis)

Front 32

- mesenchymal cells--> osteogenic cells--> osteoblasts--> osteocytes. **Occurs in the mandible and flat bones of the skull. Mesenchymal cells in fibrous C.T membranes differentiate into osteogenic cells, which become osteoblasts. This happens first at the center of ossification. Osteoblasts secrete matrix and become surrounded by matrix so that they are now called osteocytes. Calcium salts are deposited in the matrix so that it hardens. Bone matrix is formed into spongy bone. The mesenchymal cells surrounding bone become periosteum and superficial layers of bone are replaced by compact bone.

Back 32

Intramembranous ossification (bone forms on or in loose fibrous C.T. membranes)

Front 33

- (bone forms inside of hyaline cartilage) mesenchymal cells -->chondroblasts--> chondrocytes, which die and are replaced by osteoblasts--> osteocytes. ***At the site where the bone forms, mesenchymal cells differentiate into chondroblasts which produce cartilage. A perichrondrium (membrane) forms around the developing cartilage. Chondroblasts become chondrocytes. As the cartilage model grows chondrocytes die which alters the pH and triggers calcification. Small cavities begin to form the marrow cavity. A primary ossification center begins to form from the outside inward at the mid-region (diaphysis)) of the bone when a nutrient artery penetrates and stimulates osteogenic cells to become osteoblasts. Osteoblasts produce compact bone on the outside and spongy bone on the inside. Osteoclasts break down spongy bone to form the marrow cavity. Blood vessels penetrate epiphyses to form secondary ossification centers. Bone formation here is similar to primary but no cavity is formed and ossification proceeds from the inside outward. Cartilage remains on the outside to form the articular cartilage and remains between diaphysis and epiphysis to form the epiphyseal plate

Back 33

Endochondral ossification

Front 34

Explain the role of Vitamin C in regulating bone growth

Back 34

- needed for synthesis of collagen and for differentiation of osteoblasts into osteocytes.

Front 35

Explain the role of Vitamin A in regulating bone growth

Back 35

-stimulates activity of osteoblasts.

Front 36

are produced at puberty and initially produce “growth spurts” of the teenage years Eventually these in both sexes, stop growth at the epiphyseal plate.

Back 36

Sex steroids (e.g. estrogen and testosterone)

Front 37

- is an ongoing replacement of old bone by new bone and begins in utero.

Back 37

Remodeling

Front 38

- broken ends protrude through the skin. This can lead to infection of bone.

Back 38

Open (compound) fracture

Front 39

- bone breaks cleanly but does not protrude through skin.

Back 39

Closed (simple)

Front 40

- bone fragments into many pieces.

Back 40

Comminuted

Front 41

- one side of the bone is broken and the other side bends.

Back 41

Greenstick

Front 42

- broken ends of bone are forced into each other.

Back 42

Impacted fracture

Front 43

- a series of microscopic fissures in bone without damage to other tissues.

Back 43

Stress fracture

Front 44

Describe how bones Grow in length:

Back 44

1. The epiphyseal plate is a layer of hyaline cartilage where bone grows in length (interstitial growth)
2. Here the cartilage cells divide near the epiphyseal side of this plate to lay down new cartilage for growth.
3. On the diaphyseal side of the plate cartilage is replaced by bone so that the thickness of the plate stays relatively constant.
4. Between 18-25 years old, the epiphyseal plate closes and totally turns into bone. This leaves the epiphyseal line. A bone fracture at this plate, during youth, can cause it to close prematurely.

Front 45

Describe how bones Grow in diameter:

Back 45

1. Bone thickens by appositional growth at the periosteum.
2. Osteoblasts form new osteons by laying down new concentric lamellae around the periosteal blood vessels which become the central canals.
3. Osteoclasts in the endosteum destroy old bone to enlarge the medullary cavity.

Front 46

Explain the role of calcium and phosphorus in regulating bone growth.

Back 46

Large amounts of calcium and phosphorus are needed especially when bones are growing.

Front 47

Explain the role of human growth hormone (hGH) in regulating bone growth.

Back 47

In childhood, human growth hormone (hGH) stimulates production of insulin-like growth factors (IGF’s) which stimulate cell division in the epiphyseal plate and periosteum.

Front 48

Describe the processes involved in bone remodeling

Back 48

A. It is done to strengthen bone, esp. in areas where there is mechanical stress. Also it renews bone before deterioration sets in and helps repair fractures.
B. Osteoclasts release enzymes and acids, which break down bone matrix proteins and dissolve mineral salts.
C. Osteoblasts then move in and lay down new bone matrix where it is needed.
D. Braces used in orthodontics place stress on bone that forms teeth sockets so that it remodels the socket to better align the teeth.

Front 49

Events in fracture repair:

Back 49

1. Blood released by injured vessels forms a fracture hematoma (clot). Then blood capillaries grow into clot. Phagocytes and osteoclasts remove damaged tissue to form a procallus.
2. Fibroblasts and chondroblasts produce fibrocartilage to form the fibrocartilaginous callus.
3. Osteoblasts form spongy bone to make a bony (hard) callus.
4. Callus is remodeled by osteoclasts which resorb dead fragments. Spongy bone at the periphery is replaced by compact bone.

Front 50

Describe the role of bone in calcium homeostasis.

Back 50

A. Calcium (Ca2+) is needed for various body functions. Bone serves as the major reservoir for Ca2+ so that
exchanges of Ca2+ occurs between bone and the blood.
B. If blood Ca2+ drops too low, this stimulates release of parathyroid hormone (PTH)
C. If blood Ca2+ is too high, this stimulates release of the hormone calcitonin (from the thyroid)

Front 51

parathyroid hormone (PTH)

Back 51

1. ↑ the number and activity of osteoclasts which ↑ the rate of bone resorption (break down)which ↑ Ca2+ concentration in the blood.
2. stimulates kidneys to conserve Ca2+ so that it is not lost in the urine.
3. stimulates formation of calcitriol (active form of Vit D) in the kidneys, which causes more Ca2+ to be absorbed from the food in the intestines
4. produced when blood calcium is too low

Front 52

calcitonin

Back 52

1. inhibits osteoclast activity (so that less Ca2+ is released into the blood).
2. ↑ Ca2+ uptake by and deposition into the bone.
3. produced when blood calcium is too high

Front 53

Describe how exercise and mechanical stress affect bone tissue

Back 53

A. Exercise is good because it places mechanical stress on bone. Bone reacts to this by depositing more Ca2+ and collagen fibers to strengthen stress points.
B. Also this stress ↑ calcitonin production that inhibits bone resorption, thus strengthening bone.

Front 54

Describe the effects of aging on bone tissue

Back 54

A. Because of ↓ production of hormones, esp. sex hormones, osteoblast activity ↓, Ca2+ and other minerals concentrations ↓ in bone.
B. Protein synthesis ↓ so that less collagen is deposited in bone so that it looses its tensile strength and becomes more brittle.

Front 55

Discuss the following function of the skeletal system.

Support

Back 55

- bone forms a basic framework of the body.

Front 56

Discuss the following function of the skeletal system

Protection

Back 56

- protects organs from injury (e.g. skull).

Front 57

Discuss the following function of the skeletal system

Helps in movement

Back 57

- muscles contract to pull bone and move the body.

Front 58

Discuss the following function of the skeletal system

Mineral homeostasis

Back 58

- stores some minerals and releases them into the blood when needed.

Front 59

Discuss the following function of the skeletal system

Site for energy storage

Back 59

- yellow bone marrow contains triglyceride energy reserves.

Front 60

Discuss the following function of the skeletal system

Site for blood cell production (hemopoiesis)

Back 60

- red bone marrow produces RBC’s, WBC’s, and platelets.

Front 61

Osteoporosis
Causes:

Back 61

bone resorption (break down) outpaces deposition so that bone mass ↓ and bones become more porous and lighter.

Front 62

Osteoporosis
Symptoms:

Back 62

a. Shrinkage of backbone and height loss
b. Hunched back
c. Bone fractures easily
d. Considerable pain

Front 63

Rickets and osteomalacia
Causes:

Back 63

Bones fail to calcify so that they become soft and easily deformed

Front 64

Rickets and osteomalacia
Symptoms:

Back 64

- bowed legs and bone deformity.
- pain and tenderness in bone and bone fractures from minor traumas.