Lecture 10 Flashcards
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
fibrous connective tissue
1. osteoid; mesenchyme
2. osteoid; osteocytes
3. spongy; periosteum
4. compact; spongy
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 _____________
hyaline cartilage model
1. cartilage
2. primary; bony collar, periosteum
3. primary; secondary
4. primary; secondary; epiphysis
5. epiphyseal plate
6. marrow; epiphyseal plate
Bone Growth and Remodeling:
-Ossification continues throughout life with the growth and remodeling of bones
-Bones grow in two directions: ______ and ________
length; width
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 __________
- reserve
- proliferation
- hypertrophy
- calcification
- deposition
Zone of reserve cartilage
typical histology of resting hyaline cartilage
Zone of cell proliferation
chondrocytes multiplying and lining up in rows of small flattened lacunae
Zone of cell hypertrophy
cessation of mitosis; enlargement of chondrocytes and thinning of lacuna walls
Zone of calcification
temporary calcification of cartilage matrix between columns of lacunae
zone of bone deposition
breakdown of lacuna walls, leaving opens channels; death of chondrocytes; bone deposition by osteoblasts forming trabecular of spongy bone
Bone remodeling:
-bone remodeling (absorption and deposition occurs throughout life)– ____% of skeleton per year
-Wolff’s law of bone:
-10%
-architecture of bone determined by mechanical stresses placed on it; bony processes grow larger in response to mechanical stress
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
10
-calcitonin; inhibited; stimulated
-PTH; stimulates; inhibits; kidneys; phosphate
Mineral deposition
process in which calcium, phosphate, and other ions are taken from blood and deposited in bone
Mineral Resorption
process of dissolving bone and releasing minerals into blood; performed by osteoclasts at ruffled border
Calcium Homeostasis is regulated by three hormones:
calcitriol (vitamin D)
calcitonin
parathyroid hormone
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
vitamin D
-raises
-deposition
-available
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
-C; thyroid gland
-lowers
1. inhibits osteoclast activity
2. Stimulates osteoblast activity
-children; adults
-pregnant
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.
-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
Phosphate homeostasis
Calcitriol _______ phosphate levels by promoting its absorption by small intestine
-PTH (parathyroid) _______ blood phosphate levels by promoting its urinary excretion
raises; lowers
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 _______
20
puberty; adolescence
stop
Fractures and their repair
stress fracture:
types of fractures:
break caused by abnormal trauma to a bone
types:
transverse
oblique
spiral
comminuated
avulsion
impacted
fissure
greenstick
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
- Hematoma; hematome; granulation
- Soft callus; collagen; fibrocartilage; soft callus
- Hard callus; bony collar
- osteoclasts; spongy; compact
Overview of the Skeleton
1. _________ skeleton:
-forms central supporting axis of body
-includes:
- _________ skeleton:
-includes:
- axial; skull, vertebrae, sternum, ribs, sacrum, and hyoid
- appendicular; pectoral girdle, upper limb, pelvic girdle, lower limb
_______ 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)
-270; fusion
-206; sesamoid (ankles, wrist, knees); sutural
