Lecture 10

Question 1

Intramembraneous ossification: develops from ___________

Steps:
1. Deposition of ______ tissue into embryonic ________
2. Calcification of ______ tissue and entrapment of ___________
3. Honeycomb of _______ bone with developing ________
4. Filling of space to form ________ bone at surfaces, leaving ________ bone in middle

Answer 1

fibrous connective tissue
1. osteoid; mesenchyme
2. osteoid; osteocytes
3. spongy; periosteum
4. compact; spongy

Question 2

Endochondral ossification: starts with preexisting ____________

Steps:
1. Early ______ model
2. Formation of ________ ossification center, __________, and __________
3. Vascular invasion, formation of _________ marrow cavity, and appearance of _________ ossification center
4. Bone at birth, with enlarged ________ marrow cavity and appearance of _______ marrow cavity in one __________
5. Bone of child, with ____________ at distal end
6. Adult bone with a single ________ cavity and closed _____________

Answer 2

hyaline cartilage model
1. cartilage
2. primary; bony collar, periosteum
3. primary; secondary
4. primary; secondary; epiphysis
5. epiphyseal plate
6. marrow; epiphyseal plate

Question 3

Bone Growth and Remodeling:
-Ossification continues throughout life with the growth and remodeling of bones
-Bones grow in two directions: ______ and ________

Answer 3

length; width

Question 4

Zone elongation: zones of the metaphysis
1. Zone of _______ cartilage
2. Zone of cell ____________
3. Zone of cell _____________
4. Zone of __________
5. Zone of bone __________

Answer 4

1. reserve
2. proliferation
3. hypertrophy
4. calcification
5. deposition

Question 5

Zone of reserve cartilage

Answer 5

typical histology of resting hyaline cartilage

Question 6

Zone of cell proliferation

Answer 6

chondrocytes multiplying and lining up in rows of small flattened lacunae

Question 7

Zone of cell hypertrophy

Answer 7

cessation of mitosis; enlargement of chondrocytes and thinning of lacuna walls

Question 8

Zone of calcification

Answer 8

temporary calcification of cartilage matrix between columns of lacunae

Question 9

zone of bone deposition

Answer 9

breakdown of lacuna walls, leaving opens channels; death of chondrocytes; bone deposition by osteoblasts forming trabecular of spongy bone

Question 10

Bone remodeling:
-bone remodeling (absorption and deposition occurs throughout life)– ____% of skeleton per year
-Wolff’s law of bone:

Answer 10

-10%
-architecture of bone determined by mechanical stresses placed on it; bony processes grow larger in response to mechanical stress

Question 11

Physiology of Osseous Tissue
Homeostasis of calcium= ______ mg/dL

-Increased Ca2+ level:
thyroid gland releases __________ to lower Ca2+ level
osteoclast activity is __________
osteoblast activity is _________

-Decreased Ca2+ level
Parathyroid glands release _______ to raise Ca2+ levels
-_______ osteoclasts (resporption)
-_______ osteoblasts (deposition)
-promotes Ca2+ reabsorption by ________
-more urinary ______ excretion

Answer 11

10
-calcitonin; inhibited; stimulated
-PTH; stimulates; inhibits; kidneys; phosphate

Question 12

Mineral deposition

Answer 12

process in which calcium, phosphate, and other ions are taken from blood and deposited in bone

Question 13

Mineral Resorption

Answer 13

process of dissolving bone and releasing minerals into blood; performed by osteoclasts at ruffled border

Question 14

Calcium Homeostasis is regulated by three hormones:

Answer 14

calcitriol (vitamin D)
calcitonin
parathyroid hormone

Question 15

Calcitriol- most active form of ____________
-produced by actions of skin, liver, and kidneys
-hormone that _______ blood calcium level–> resulting in bone ___________
-overall function is to make make calcium as __________ as possible

Answer 15

vitamin D
-raises
-deposition
-available

Question 16

Calcitonin
-secreted by ___ cells of ___________ when blood calcium levels rise too high
-________ blood calcium concentration in two ways:
1.
2.
-important in _______, weak effect in _______
-may inhibit bone loss in _________ women

Answer 16

-C; thyroid gland
-lowers
1. inhibits osteoclast activity
2. Stimulates osteoblast activity
-children; adults
-pregnant

Question 17

Parathyroid hormone
-secreted by ___________ on posterior surface of thyroid
-PTH released when calcium levels are _____ in blood
-PTH _______ calcium blood level by four mechanisms
1.
2.
3.
4.

Answer 17

-parathyroid glands
-low
-raises
1. increased osteoclast activity (bone resorption)
2. reduced osteoblast activity (less bone deposition)
3. more urinary phosphate excretion
4. less urinary calcium excretion

Question 18

Phosphate homeostasis
Calcitriol _______ phosphate levels by promoting its absorption by small intestine
-PTH (parathyroid) _______ blood phosphate levels by promoting its urinary excretion

Answer 18

raises; lowers

Question 19

Other factors affecting bone
-at least ____ or more hormones, vitamins, and growth factors affect osseous tissue
-bone growth especially rapid in ________ and _________
-anabolic steroids cause growth to _______

Answer 19

20
puberty; adolescence
stop

Question 20

Fractures and their repair
stress fracture:

types of fractures:

Answer 20

break caused by abnormal trauma to a bone

types:
transverse
oblique
spiral
comminuated
avulsion
impacted
fissure
greenstick

Question 21

Healing of Fractures steps:
1. _________ formation: the ________ is converted to __________ tissue by invasion of cells and blood capillaries
2. ___________ formation:
deposition of _________ and _________ converts granulation tissue to a ________
3. ____________ formation:
osteoblasts deposit temporary ________ around the fracture to unite the broken pieces while ossification occurs
4. Bone remodeling:
small bone fragments are removed by ________, while osteoblasts deposit _______ bone and then convert it to _________ bone

Answer 21

1. Hematoma; hematome; granulation
2. Soft callus; collagen; fibrocartilage; soft callus
3. Hard callus; bony collar
4. osteoclasts; spongy; compact

Question 22

Overview of the Skeleton
1. _________ skeleton:
-forms central supporting axis of body
-includes:

2. _________ skeleton:
   -includes:

Answer 22

1. axial; skull, vertebrae, sternum, ribs, sacrum, and hyoid
2. appendicular; pectoral girdle, upper limb, pelvic girdle, lower limb

Question 23

_______ bones at BIRTH, but number decreases with ______

Bones of the Skeletal System
#_______ bones in typical ADULT skeleton
-varies with development of _______ bones
-varies with presence of ________ bones in skull (extra bones that delves in skull suture lines)

Answer 23

-270; fusion

-206; sesamoid (ankles, wrist, knees); sutural