Chapter 6 Flashcards
Bones and Skeletal Tissues
Made of highly resilient, molded cartilage tissue that consists primarily of water
Contains no blood vessels or nerves
Skeletal cartilage
Layer of dense connective tissue surrounding cartilage like a girdle
Helps cartilage resist outward expansion
Contains blood vessels for nutrient delivery to cartilage
Perichondrium
Chondrocytes, encased in lacunae, within extracellular matrix
Cartilage makeup:
Provides support, flexibility, and resilience
Ex. Most abundant cartilage
Joints, ribs, larynx, nasal cartilage
Hyaline cartilage
Similar to hyaline cartilage, but contains elastic fibers
Ex. External ear and epiglottis
Elastic cartilage
Type of cartilage
Thick collagen fibers, has great tensile strength
Ex. Menisci of knee, intervertebral discs, where bones of pelvis come together
Fibrocartilage
Support
Protection
Movement
Mineral growth factor storage
Blood cell formation
Triglyceride (fat) storage
Hormone production
Function of bone
Formation of blood cells in red marrow cavities
Hematopoiesis
Secreted by bones to help regulate insulin secretion, glucose levels, and metabolism
Osteocalcin
How many bones are in human body?
206
Long axis of body
Includes skull, vertebral column, rib cage
Axial skeleton
Sites of muscle, ligament, and tendon attachment on external surfaces
Areas involved in joint formation or conduits for blood vessels and nerves
Bone markings
Outward bulge of bone
Projection
Bowl-like or groove-like cut out that can serve as passageways for vessels and nerves, or plays roles in joints
Depression
Hole or canal bone that serves as passageways for blood vessels and nerves
Opening
Organs that contain different types of tissues
Bone
Dense outer layer on every bone that appears smooth and solid
A.k.a lamellar bone
Consists of:
1. Osteon
2. Canals and canaliculi
3. Interstitial and circumferential lamellae
Compact bone
Made up of honeycomb of small, needle-like or flat pieces of bone called trabeculae
No osteons present
Trabeculae confer strength
Organized along lines of stress to resist stress
Spongy bone
Open spaces between trabeculae of spongy bone; Has RBCs
Bone marrow
Cartilage that covers area of bone that is part of a moveable joint
Hyaline cartilage
Thin plates of spongy bone covered by compact bone in short, irregular, and flat bones
(Looks like oreo)
Diploe
Tubular shaft that forms long axis of bone
Consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults
Diaphysis
Ends of long bones that consist of compact bone externally and spongy bone internally
Articular cartilage covers joint surfaces
Epiphyses
Between diaphysis and epiphysis
Remnant of epiphyseal plate where bone growth occurs
Epiphyseal line
Longer than they are wide
Long bones
Type of bone that are cube-shaped
Short bones
Type of bone that is thin, flat, slightly curved
Flat bones
Type of bone; Complicated shapes
Irregular bones
Special type of short bone that forms within a tendon
Common around the knee
Sesamoid bones
White, double-layered membrane that covers external surface of bone except joints
2 layers - fibrous, osteogenic
Periosteum
Outer periosteum layer
Dense irregular tissue
Consists of sharpey’s fibers - collagen fibers that secure periosteum to bone matrix
Fibrous layer
Inner periosteum layer, against the bone
Contains stem cells that gives rise to most all bone cells
Osteogenic layer
Openings where nerve fibers and blood enter the periosteum
(nutrients)
Nutrient foramen
Delicate connective tissue membrane covering internal bone surface
Covers trabeculae of spongy bone
Lines canals that pass through compact bone
Contains stem cells
Deep to periosteum
Endosteum
Hematopoietic tissue, produces red blood cells, white blood cells, and platelets
Red bone marrow
Produces fat, cartilage, and bone
Yellow marrow
Formation and development of RBCs
Hematopoiesis
Five major bone cell types:
- Osteogenic cells
- Osteoblasts
- Osteoclasts
- Osteocytes
- Bone-lining cells
Mitotically active stem cells in periosteum and endosteum
When stimulated, they differentiate into osteoblasts or bone-lining cells
Some remain as stem cells
Osteogenic cells
Actively mitotic
Bone forming cells that secrete osteoid
“Blasting out” osteoid
Osteoblasts
Bone resorbing cell (breakdown); giant multinucleate cells
Have ruffled borders that increase surface area - release enzymes to degrade bone
Osteoclasts
Mature bone cells in lacunae that no longer divide
Maintain bone matrix and act as stress or strain sensors
Respond to chemical stimuli such as increased force on bone or weightlessness
Osteocytes
Flat cells lining bone surfaces believed to also help maintain matrix
Bone lining cells
Structural unit of compact bone
Consists of an elongated cylinder that runs parallel to long axis of bone
Several lamellae rings inside that composes it
Osteon
Rings of bone matrix in osteon cylinder
Contain collagen fibers that run in different directions in adjacent rings
Withstands stress and resists twisting
1. Interstitial - between osteons
2. Circumferential - outer bone
Lamellae
Runs through core of osteon
Lined with endosteum
Contains blood vessels and nerve fibers
Central canal
Small cavities that contain osteocytes
Occur at junctions of lamellae
Lacunae
Hairlike canals that connect lacunae to each other and to the central canal
Allow communication between all osteocytes and osteon and permit nutrients and wastes to be relayed from one cell to another
“Small and cute”
Canaliculi
Lie at right angles to long axis of bone
Connect blood and nerve supply of medullary cavity to central canals
Perforating canals (Volkmann’s canals)
Lamellae that are not part of osteon
Fills gaps between forming osteons
Interstitial lamellae
Type of lamellae; Extend around entire surface of diaphysis
Help long bone to resist twisting
Circumferential lamellae
Organic bone component
Unmineralized bone matrix; secreted by osteoblasts; made of up of collagen and calcium-binding proteins; contributes to to high tensile strength and flexibility of bone; 1/3 of bone matrix
Osteoids
Bonds between collagen molecules stretch and break to dissipate energy and prevent fractures
Resilience of bone is due to these
Sacrificial bonds
Inorganic bone component
65% of bone; consist mainly of tiny calcium phosphate crystals in and around collagen fibers, responsible for hardness and resistance to compression
(Bones will last long after death because of mineral composition)
Hydroxyapatites
Process of bone tissue formation
2 types:
1. Endochondral ossification
2. Intramembranous ossification
Ossification
Type of ossification
Bone forms by replacing hyaline cartilage
Bones = cartilage (endochondral) bones
Form most of skeleton
Begins at primary ossification center in shaft
Endochondral ossification
When does formation of bony skeleton begin?
Month 2 of development
Contains nutrient artery and vein, nerve fibers, red marrow, osteogenic cells, and osteoclasts
Delivers nutrients to growing bone
Forms during endochondral ossification
Periosteal bud
Type of ossification
Begins with fibrous connective tissue membranes formed by mesenchymal cells
Forms frontal, parietal, occipital, temporal, and clavicle bones
Bones = membrane bones
Intramembranous ossification
Continued production of cartilage and growth of epiphyseal plate
Bone growth (length)
Five regions of Epiphyseal plate:
- Resting zone
- Proliferation zone
- Hypertrophic zone
- Calcification zone
- Ossification zone
Chondroblasts divide less often
Epiphyseal plate thins, then is replaced by bone
Epiphyseal plate closes when diaphysis and epiphysis fuse
Females - 18
Males - 21
End of bone growth (length)
Occurs throughout life
Bone thicken in response to increased stress from muscle activity or added weight
More building than breaking down
Growth of bone (width)
Most important hormone in stimulating epiphyseal plate activity in infancy and childhood
Growth hormone
Modulates activity of growth hormone, ensuring proper proportions
Thyroid hormones
Promote adolescent growth spurts; specific to male and female
End growth by inducing epiphyseal plate closure
Testosterone (male)
Estrogens (female)
Consists of bone deposit and bone resorption when bones are being reformed
Bone remodeling
Controls remodeling in response to changing blood calcium levels
Calcium involved
Hormonal controls (Bone remodeling)
Bone shapes to reflect stresses they encounter
Bones are stressed when weight bears on them or muscle pulls on them
Response to mechanical stress (Bone remodeling)
States that bones grow or remodel in response to demands placed on them
Wolf’s Law
Breaks in a bone
Classified by:
1. Position bone ends in (Non-displaced/displaced)
2. Completeness of break (Complete/incomplete)
3. Whether skin is penetrated (Open/closed)
Fracture
Bone fragments into three or more “minute” pieces
Comminuted fracture
Bone is crushed from pressure
Compression fracture
Ragged break occurs when excessive twisting forces are applied to a bone
Common sports fracture
Spiral fracture
Bone breaks and epiphysis separates from the diaphysis along epiphyseal plate
Epiphyseal fracture
Bone breaks incompletely, much in a way a green stick breaks; one side of shaft breaks
Common in children
Greenstick fracture
Broken bone portion is pressed inward
Common skull fracture
Depressed fracture
Physician’s hands manipulates bones ends to correct position
Closed (external) reduction
Surgical pins or wires secure bones ends together
Open (internal) reduction
Mass of clotted blood
Forms when broken parts of bone are healing back together
Hematoma
Imbalances between bone deposit and bone resorption
Ex. Osteomalacia/Rickets, osteoporosis, Paget’s Disease
Bone disorders
Bones are poorly mineralized
Results in softer, weaker bones (malacia=soft)
Pain upon weight bearing
In children:
- Bowed legs and other bone deformities because bones ends are enlarged and abnormally long
- Caused by vitamin D deficiency
Osteomalacia (Ricket’s)
Excessive and haphazard bone deposit and resorption cause bone to be made fast and poorly; High ratio of spongy to compact bone and reduced mineralization
Occurs in spine, pelvis, femur, and skull
Paget’s Disease
Group of diseases in which bone resorption exceeds deposit
Matrix remains normal, but bone mass declines
Spongy bone of spine and neck of femur most susceptible
Vertebral and hip fractures common
Osteoporosis
Most often in aged women, postmenopausal women
Insufficient exercise
Diet poor in calcium and protein
Smoking
Risk factors for Osteoporosis
