Chapter 6 Flashcards
Functions of Bones
Support Protection Movement Blood Cell Formation Mineral Storage
In relation to support, bones form
The framework that support the body and cradles soft organs
In relation to protection, bones provide
A protective case for the brain, spinal cord, and vital organs
In relation to movement, bones provide
Levers for muscles
In relation to mineral storage, bones are a
Reservoir for minerals, especially calcium and phosphorus
What are the two categories of the skeleton?
Axial skeleton and Appendicular skeleton
What bones are in the axial skeleton?
Bones of the skull, vertebral column, and rib cage
What bones are in the appendicular skeleton?
Bones of the upper and lower limbs, shoulder, and hip
What are the shapes of bones?
Long
Flat
Short
Irregular
Long bones
(1) Are ___ than they are ___
(2) Have ____ at two ends that may contain:
(3) Are primarly:
(1) Longer; wide
(2) Shafts; a substantial amount of spongy bone
(3) Compact bone
All bones of the limbs except what are made up of compact bone?
Patella, wrist, ankle
Flat bones
(1) Physical description
(2) Are two ____ with ___ between
(3) Examples
(1) Thin, flat, and a bit curved
(2) Parallel compact bone surfaces; spongy bone
(3) Sternum, ribs, and most skull bones
Short bones
(1) Physical description
(2) Are mostly
(3) Are found
(1) Cube-like
(2) Spongy bone - thin surface layer of compact
(3) In the wrist and ankle, and in tendons (like the patella)
Irregular bones
(1) Are bones with
(2) Are mostly
(3) Examples
(1) Complicated shapes
(2) Spongy - thin layers of compact
(3) Some skull, vertebrae, and hip bones
Compact bone is
Dense, looks smooth
Spongy bone is made up of
Trabeculae
Trabeculae are ____ that
“little beams” that create open space filled with marrow
Spongy bone has
No osteons
Irregular lamellae
Long bones structure consists of
Diaphysis and Epiphysis
Diaphysis is a
Tubular shaft that forms the long axis of bone
Diaphysis is composed of
Compact bone that surround the medullary cavity
Epiphyses are the
Expanded ends of long bone
The exterior of epiphysis is
Compact
The interior of epiphysis is
Spongy bone
The joint surface of epiphysis is
Covered with articular (hyaline) cartilage
The epiphysis line separates
The diaphysis from the epiphysis
Bone membranes consist of
The periosteum
Sharpey’s fibers
The endosteum
The periosteum is a
White double-layered protective membrane around the diaphysis
The periosteum’s outer layer is
Fibrous and made of dense irregular tissue
The periosteum’s inner layer is
Osteogenic, and on the bone surface
The inner layer of the periosteum is primarily composed of
Osteoblasts and osteoclasts
The periosteum is richly supplied with (1) which enter through (2)
(1) Nerve fibers, blood vessels, and lymphatic vessels
(2) Nutrient foramina
Sharpeys fibers are
Collagen fibers
Sharpey’s fibers do what?
Securethe periosteum to bone
Osteoporosis is caused by
Atrophy of Sharpey’s fibers
Endosteum is the
Delicate membrane covering internal surface of the bone
Haversian system is the
Structural unit of compact bone
Osteon is the
Haversian system
Lamella are (2)
(1) Weight bearing
(2) Column-like matrix tubes composed mainly of collagen
Haversian canal is the
Central canal
Haversian canal contains
Blood vessels and nerves
Volkmann’s canals are
Channels lying at right angels to the Haversian canal
Volkmann’s canals connect
Blood and nerve supply of the periosteum to that of the Haversian canal
Osteocytes are
Mature bone cells
Osteocytes lie in
Lacunae at junctions lamellaee
Osteocytes function is to
Maintain the matrix
Lacunae are
Small cavities in bone that contains osteocytes
Canaliculi are
Hair-like canals that connect lacunae to each other and the Haversian canal
Canaliculi allow
Nutrients and wastes to pass between them
Chemical composition of bone is either
Organic or Inorganic
Organic chemical composition consists of
Osteoblasts
Osteocytes
Osteoclasts
Osteoids
Osteoblasts are
Bone-forming cells
Obsteoblasts are responsible for
The bone matrix
Osteocytes are
Mature bone cells
Osteocytes maintain
The matrix of bone
Osteoclasts are
Large cells that reabsorb or breakdown bone matrix
Osteoclasts cling to
The bone
Osteoid is
Unmineralized bone matrix
Inorganic chemical composition makes up
65% of bone by mass
Inorganic chemical composition is responsible for
Bone hardness and it’s resistance to compress
Osteogenesis and ossification is
The process of bone tissue formation
Osteogenesis/Ossification leads to (3)
(1) The formation of the bony skeleton in embryos
(2) Bone growth until early adulthood
(3) Bone thickness, remodeling and repair
In the formation of the bony skeleton in embryos, (1) replaces (2)
(1) Bone tissue (2) fibrous membranes and hyaline cartilage
The formation of the bony skeleton begins
At week 8 of embryo development
Intramembranous ossification is where
Bone develops from a fibrous membrane
Most of the ____ are formed during intramembranous ossification
Flat bones of the skull and clavicles
Fibrous connective tissue membranes are formed by ____ during intramembranous ossification
Mesenchymal cells
Mesenchymal cells form what?
Fibrous connective tissue membranes
Menechymal cells are
Stem cells that can differentiate into a variety of cells
Stage 1 of formation of bony skeleton (2)
(1) Ossification center appears in the fibrous connective tissue membrane
(2) Mesenchymal cells will differentiate into osteoblasts
Ossification center is the
Site where bone begins to form
Stage 2 of formation of bony skeleton (3)
(1) Bone matrix is secreted within the fibrous membrane
(2) osteoblasts secrete osteoid, which mineralizes within a few days
(3) Osteoblasts that get trapped in osteoid become osteocytes
Stage 3 of formation of bony skeleton (1 a,b)
(1) Woven bone and periosteum form
(a) Deposits of osteoid accumulate and fuse together, forms network of trabeculae when encloses blood vessels
(b) Mesenchyme condense to form periosteum
Stage 4 of formation of bony skeleton (1 a,b)
Bone collar of compact bone forms , and red marrow appears
(a) after periosteum forms, inner osteogenic layer secretes osteoid
(b) red marrow forms in spongy bone
Endochondral ossification is when
Bone forms by replacing hyaline cartilage
When does endochondral ossification begin?
In the second/third month of development
Endochondral ossification uses
Hyaline cartilage “bones” as models for bone construction
Endochondral ossification requires
Breakdown of hyaline cartilage prior to ossification
Stage 1 of endochondral ossification in a long bone (2)
(1) Bone collar forms around the diaphysis of the hyaline cartilage model
(2) Osteoblasts or periosteum secrete osteoid against cartilage
Stage 2 of endochondral ossification in a long bone (3)
(1) Cartilage in the center of the diaphysis calcifies and then develops cavities
(2) Chondrocytes within shaft enlarge and cartilage matrix calcifies
(3) Becomes impermeable to nutrients and chondrocytes die
Stage 3 of endochondral ossification in a long bone (3)
(1) The periosteal bud invades the internal cavities and spongy bone forms
(2) Invasion of artery, veins, and nerves
(3) Osteoblasts secrete osteoid around cartilage cells, forming trabeculae
Stage 4 of endochondral ossification in a long bone (2)
(1) Formation of medullary cavity; appearance of secondary ossification centers in the epiphyses
(2) Osteoclasts breakdown the spongy bone
Stage 5 of endochondral ossification in a long bone (2)
(1) Ossification of the epiphyses (after birth), with hyaline cartilage remaining only in the epiphyseal plates
(2) Spongy bone is retained
By what age have all bones ossified completely?
25
Functional zones of long bone growth
Growth zone
Transformation zone
Osteogenic zone
Growth zone is at the
Epiphysis plate
What happens in the osteogenic zone?
(1) New bone formation occurs
(2) Osteoclasts degrade the spongy bone
(3) That results in the medullary cavity growing longer as bone grows
During long bone growth in length, cartilage
Continually grows and is replaced by bone
At what age does the epiphyseal plate closure occur?
18-21
During the epiphyseal plate closure, the
Epiphyseal plate is replaced by bone tissue and the epiphysis and diaphysis fuse
During remodeling, bone is
Resorbed and added by appositional growth
Osteoid seam is an
Unmineralized band of bone matrix
Bone resorption is accomplished by
Osteoclasts
Resorption bays are
Grooves formed by osteoclasts as they break down bone matrix
What hormones help modulate for correct bone growth proportions?
PTH and calcitonin
What two control loops regulate bone remodeling?
(1) Hormonal mechanism maintains calcium homeostasis in the blood
(2) Mechanical and gravitational forces acting on the skeleton
What is the process for the hormonal mechanism? (4)
(1) Rising blood Ca2+ levels trigger the thyroid to release calcitonin
(2) Calcitonin stimulates calcium salt deposit in bone
(3) Falling blood Ca2+ levels signal the parathyroid glands to release PTH
(4) PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood
Wolff’s law states that
A bone grows or remodels in response to the forces or demands placed upon it
Observations supporting Wolff’s law include (2)
(1) Long bones are thickest midway along the shaft (where bending stress is the greatest)
(2) curved bones are thickest where they are most likely to buckle
How are bone fractures classified? (4)
(1) The position of the bone ends after fracture
(2) The completeness of the break
(3) The orientation of the bone to the long axis
(4) Whether or not the bones ends penetrate the skin
Types of bone fractures (8)
Nondisplaced Displaced Complete Incomplete Linear Transverse Compound Simple
A nondisplaced fracture is where
Bone ends retain their normal position
A displaced fracture is where
The bone ends are out of normal alignment
A complete fracture is where
The bone is broken all the way through
An incomplete fracture is where
The bone is not broken all the way through
A linear fracture is where
The fracture is parallel to the long axis of the bone
A transverse fracture is where
The fracture is perpendicular to the long axis of the bone
A compound (open) fracture is where
The bone ends penetrate the skin
A simple (closed) fracture is where
The bone ends do not penetrate the skin
Common types of fractures (6)
Comminuted Compression Spiral Epipyseal Depressed Greenstick
A comminuted fracture is where
The bone fragments into three or more pieces
Common in the elderly
A compression fracture is where
The bone is crushed
Common in porous bones
A spiral fracture is a
Ragged break when bone is excessively twisted
Common sports injury
A epiphyseal fracture is where
The epiphysis separated from the diaphysis along the epiphyseal line
Occurs where cartilage cells are dying
A depressed fracture is where
The broken bone portion is pressed inward
Typical in skull fractures
A greenstick fracture is an
Incomplete fracture where one side of the bone breaks and the other side bends
Common in children
Stage 1 of healing a bone fracture
Hematoma formation
Stage 2 of healing a bone fracture
Fibrocartilaginous callus formation
Stage 3 of healing a bone fracture
Bony Callus formation
Stage 4 of healing a bone fracture
Bone remodeling
Osteoporosis is a
Group of diseases in which bone reabsorption outpaces bone deposit
In osteoporosis, what is most vulnerable?
Spongy bone of the spine
Osteoporosis occurs most often in
Postmenopausal women
With osteoporosis bones
Become so fragile that sneezing can cause fractures
Paget’s disease is characterized by
Excessive bone formation and breakdown
