Bones And Skeletal Tissue - Chapter 6 Flashcards
What type of connective tissue is perichondrium composed of?
Dense irregular connective tissue
What type of cartilage growth involves cartilage-forming cells in the surrounding perichondrium secreting new matrix against the external face of the existing cartilage tissue?
Appositional growth
What type of cartilage growth involves lacunae-bound chondrocytes dividing and secreting new matrix, expanding the cartilage from within? When does this type of growth typically end?
Interstitial growth; typically ends during adolescence when the skeleton stops growing
What are the seven major functions of bones?
- Protection for organs, 2. Support for the body, 3. Anchorage for skeletal muscles for movement, 4. Hematopoiesis, 5. Mineral storage, 6. Triglyceride storage, and 7. Osteocalcin production
What does osteocalcin, the hormone produced by bone cells, help regulate? What does it bind?
Insulin secretion (glucose metabolism in the pancreas), calcification, testosterone synthesis, energy expenditure; it binds calcium
Where is hyaline cartilage found on the skeleton?
Articulate surfaces of long bones, costal cartilage of the ribs, and nasal cartilages
Where is elastic cartilage found on the skeleton?
Nose, external ear, epiglottis
Where is fibrocartilage found on the skeleton?
Intervertebral discs and symphyses
What is the connective tissue that envelopes cartilage where it is not at a joint?
Perichondrium
How does cartilage proliferate at epiphyseal growth plates for longitudinal bone growth?
Interstitial growth
Spongy bone is a honeycomb of small, needle-like or flat pieces called ___________.
Trabeculae
Compact bone is covered outside and inside by connective tissue membranes: __________ and __________, respectively.
Periosteum; endosteum
What are the three components that all long bones have?
Epiphyses, diaphyses, and membranes
What lies between the epiphysis and diaphysis?
Epiphyseal plate (or line, if no longer growing)
What does the endosteum line in a long bone?
The inside of the medullary cavity
What kind of marrow is found in the medullary cavity of an adult long bone?
Yellow marrow
What is the flared portion of a long bone, where the diaphysis and epiphysis meet? (Not the epiphyseal line)
Metaphysis
What secures the periosteum to the external surface of the bone?
Bundles of collagen fibers called “perforating fibers”
The periosteum has two layers, the outer _______ _______, made of _______ _______ connective tissue, and the inner _______ _______, which contains ______________ cells, ________, and _________.
Fibrous layer; dense irregular; osteogenic layer; osteoprogenitor; osteoclasts, and osteoblasts
What membrane covers the trabeculae of spongy bone and lines the canals that pass through compact bone?
Endosteum
Where is red marrow found in infants? Adults?
In infants, it is found in the medullary cavities of long bones and in spongy bone. In adults, it is found only in the spongy bone of the femur and humerus, flat bones and irregular bones.
What bone component can revert back to a prior form if a person becomes anemic?
Yellow marrow in adult long bones can revert back to red marrow if increased hematopoiesis is needed.
Where are marrow transplants and extractions typically done? Why?
In flat and irregular bones, especially the pelvis, because red marrow is much more active there
Red marrow is found in the _____ of flat bones, such as the sternum.
Diploe
What is a diploe?
A layer of spongy bone within a flat bone, like the sternum or cranium
The structural units of compact bone are ______.
Osteons
Osteons consist of tree-like rings called _______, which contain ________, and a central ___________ ______.
Lamellae; lacunae; Haversian canal
What tiny canals allow osteocytes to communicate with each other and transmit nutrients and wastes?
Canaliculi
What are osteoprogenitor cells and where are they found?
Stem cells that are also called osteogenic cells, they are mitotically active and found in the periosteum and endosteum. They appear flattened in growing bones.
Which bone cells are cuboidal in shape when actively mitotic and secrete osteoid?
Osteoblasts
Where are osteoblasts found?
In the periosteum
Where are osteoclasts found?
In the endosteum
Which bone cells are giant, multinucleated, macrophage-type cells that reside in resorption bays and directly contact bone via their ruffled border?
Osteoclasts
Initial bone is _____________ and contains 90% ________ and 10% _____-_______ _____.
Unmineralized; collagen; calcium-binding proteins.
Which bone cells respond to increased mechanical stress? What cells do they communicate this to? What do these cells do when they receive the message?
Osteocytes; osteoblasts and osteoclasts; remodel bone as needed
Why is bone resorption important?
For regulation of blood Ca levels and for releasing Ca stores necessary for bone remodeling
What do Haversian canals contain?
Small blood vessels and nerve fibers that serve the osteon’s cells.
What canals lie at right angles to the long axis of the bone and connect the blood and nerve supply of the medullary cavity to the central canals?
Volkmann’s (perforating) canals
________ lamellae lie between intact osteons. They are incomplete and either fill the gaps between forming osteons or are remnants of osteons that have been cut by bone remodeling.
Interstitial
________ lamellae are located just deep to the periosteum and just superficial to the endosteum. They extend around the entire circumference of the diaphysis and resist twisting.
Circumferential
What is the composition of bone extracellular matrix?
25% water, 25% collagen fibers, 50% crystallized mineral salts (calcium phosphate)
What is calcification?
The process of accumulating calcium ions
What is ossification?
Calcification that is initiated by osteoblasts; mineral salts are deposited and crystallize in the framework formed by the collagen fibers of the ECM
Bone’s flexibility depends on __________ _______.
Collagen fibers
What are sacrificial bonds?
Bonds between collagen fibers that stretch and easily break during stress, dissipating energy enough to prevent fractures in the bone
What is the inorganic component of bone?
Hydroxyapatite (mineral salts) - calcium phosphates
What leads to the formation of the bony skeleton during embryonic development?
Osteogenesis
What must happen before endochondral ossification can proceed?
Cartilage has to be broken down
Describe the first step of endochondral ossification.
Small blood vessels infiltrate the perichondrium and turn it into vascularized periosteum
What is the second step of endochondral ossification?
Underlying mesenchymal cells differentiate into osteoblasts
What is the third step of endochondral ossification?
Ossification begins at the primary ossification center in the center of the hyaline cartilage shaft
What is the first step AFTER ossification has begun at the primary ossification center in endochondral ossification?
A collar of bone forms around the diaphysis as osteoid is secreted by osteoblasts
Endochondral ossification uses _______ _______ as a model for bone construction.
Hyaline cartilage
Bone tissue begins to develop following week ____ of embryonic development.
8
Which type of bone (cortical or trabecular) forms first during endochondral ossification?
Spongy (trabecular)
What happens after the bone collar forms around the diaphysis?
Chondrocytes begin to die due to lack of nutrients and the cartilaginous matrix deteriorates. Cavities begin to form; the deteriorating matrix is supported by the bone collar
The __________ ____, containing arteries and veins, nerve fibers, red marrow elements, and osteogenic cells, infiltrates the internal cavities during endochondral ossification.
Periosteal bud
What happens immediately after the periosteal bud invades the internal cavities during endochondral ossification?
Osteoclasts erode the cartilage matrix and osteoblasts secrete osteoid, forming the earliest version of spongy bone
What happens after spongy bone begins to form during endochondral ossification?
The primary ossification center continues to enlarge and osteoclasts break down the spongy bone to form the medullary cavity
At birth, most long bones have a ______ ________ surrounding remnants of ________ _____, a widening ________ _____, and two cartilaginous __________.
Bony diaphysis; spongy bone; medullary cavity; epiphyses
What forms in one or both epiphyses shortly before or after birth?
Secondary ossification centers
When secondary ossification is complete, hyaline cartilage remains only at the _______ _______ and at the junction of the _______ and _______.
Epiphyseal surfaces; diaphysis and epiphysis
What bones form by intramembranous ossification?
Cranial bones, flat bones of the face and jaw, and the clavicle
In intramembranous ossification, ossification centers form when:
Stem cells in the mesenchyme develop into osteoblasts
Post-natal epiphyseal bone growth involves four zones:
Proliferation, hypertrophic, calcification, and ossification zones
In which zone do cartilage cells undergo mitosis?
The proliferation zone
In which zone do older chondrocytes begin to enlarge, leaving interconnecting spaces?
Hypertrophic zone
In which zone does the surrounding cartilaginous matrix begin to deteriorate, allowing blood vessels to invade and leaving long, slender spicules at the epiphysis-diaphysis junction?
Calcification zone
In which zone of epiphyseal bone growth does new bone form?
Ossification zone
What is Wolff’s law?
A bone grows or remodels in response to the demands placed on it
Bone remodeling is a hormonal ________ ________ ____.
Negative feedback loop
What molecule aids in absorbing calcium from the intestines?
Calcitriol
What gland releases growth hormone? What genes does growth hormone activate?
The anterior pituitary gland; IGF-1 and IGF-2
Which growth hormone gene product is most important for growth after embryonic development and throughout life? What organs produce it?
IGF-1; Produced by the liver, skeletal muscles, and bone
What growth hormone is more prevalent during embryonic development?
IGF-2
What are some examples of growth hormone hypersecretion?
Gigantism and acromegaly
What are some examples of growth hormone hyposecretion?
Dwarfism; in adults, reduced energy levels, osteoporosis, reduced muscle strength, increased fat deposition, insulin resistance, and impaired cardiac function
What hormones regulate growth hormones and ensure proper skeleton proportions?
Thyroid hormones
What two hormones eventually induce epiphyseal closure?
Testosterone and estrogen
How do osteoclasts break down bone? What does bone resorption result in?
By using hydrogen ions and lysosomal enzymes; Increases blood calcium-phosphate circulation
What hormone stimulates osteoclasts to resorb bone and release calcium ions into the blood?
Parathyroid hormone (PTH)
What hormone is believed to lower blood calcium levels?
Calcitonin
What triggers osteoblasts to begin bone deposition?
- Local concentrations of calcium and phosphorus ions reach a threshold and spontaneously crystallize
- Calcium binding proteins increase
- Alkaline phosphatase induces mineralization
Bone deposition via osteoblastic activity reduces circulating blood levels of _____________.
Calcium phosphate
When blood calcium levels are low, ________ is released, targeting _______.
PTH; osteoclasts
What kind of fracture results in a bone fragmenting into three or more pieces? What age is this common in?
Comminuted; common in the elderly
What kind of fracture results in a bone being crushed? What kind of bone is this common in?
Compression; porous bones
When calcium circulation is low: ___________ releases _____, stimulating ________ and calcium reabsorption in the _______.
Parathyroid; PTH; osteoclasts; kidneys
When calcium circulation is high: the _________ releases _________, stimulating __________ and increasing excretion in the _________.
Thyroid; calcitonin; osteoblasts; kidneys
What minerals are required for bone remodeling?
Calcium, phosphorus, magnesium, fluoride, and manganese
Vitamin ____ stimulates the activity of osteoblasts.
A
Vitamin ____ is needed for synthesis of collagen.
C
Vitamin ____ helps build bone by increasing the absorption of calcium from foods.
D
Vitamins ____ and _____ are needed for synthesis of bone proteins.
K and B12
What fracture results in a ragged break that occurs when excessive twisting forces are applied to bone? Who is this injury common in?
Spiral; common in athletes
What fracture tends to occur where cartilage cells are dying and calcification of the matrix is occurring?
Epiphyseal
What type of fracture results from a broken bone being pressed inward? What body part is this common in?
Depression; typical of a skull fracture
What kind of fracture results in a bone breaking incompletely and is common in children?
Greenstick fracture
What kind of fracture involves one end of a fractured bone being forcefully driven into another?
Impacted fracture
What is a Pott’s fracture?
A fracture of the fibula with injury to the tibial articulation
What is a Colles’ fracture?
A fracture of the radius in which the distal fragment is displaced
What is a stress fracture?
A series of microscopic fissures in bone
What are the four stages of fracture repair?
- Hematoma forms
- Fibrocartilaginous callus formation
- Bony callus formation
- Bone remodeling
What happens within a few days of a fracture?
Blood vessels invade from the nearby periosteum and endosteum
What role do fibroblasts play in repairing a fracture?
They build collagen fibers that span the break and connect the broken bone ends
What role do chondroblasts play in fracture repair?
They secrete a cartilaginous matrix that bulges externally and eventually calcifies (the fibrocartilaginous callus)
What role do osteoblasts play in fracture repair?
They form spongy bone within the fibrocartilaginous callus
What is osteomalacia? What does this result in?
Osteoid is produced but mineral salts are not adequately deposited. Results in unusually soft, weak, painful bones.
What is Rickets? What causes it?
Osteomalacia in children; caused by a vitamin D deficiency or insufficient dietary calcium
Osteomalacia is due to a deficiency in _________, while osteoporosis is due to a deficiency in ________ and ________, or due to other factors such as drug use and genetics.
Vitamin D; calcium and phosphorus
Osteoporosis is a group of diseases in which bone ___________ outpaces bone __________.
Resorption; deposition
The overall composition of bone matrix remains normal in osteoporosis, but the ______ _____ decreases as bones become _____ and ______.
Bone mass; porous and light
What bones are most susceptible to breaking in someone with osteoporosis?
Vertebrae and the necks of femurs
What is osteopenia?
Subclinical bone loss due to inactivity
