Bones Flashcards
What is skeletal cartilage made of?
A variety of cartilage tissue
Characteristics of cartilage
1) Consists primarily of water
2) very resilient (springs back into shape)
3) no nerves or blood vessels
4) surrounded by a layer of dense irregular connective tissue (perichondrium)
5) thickness is limited by the distance that nutrients can diffuse through the matrix to reach cells
What does the Perichondrium do?
1) Helps resist outward expansion when cartilage is compressed
2) Contains blood vessels to nourish cartilage
What are the three types of cartilage?
1) Hyaline
2) Elastic
3) Fibrocartilage
Basic component of all cartilage tissue?
Chondrocytes, enclosed in small cavities (lacunae) within an extracellular matrix containing a jellylike ground substance and fibers
Hyaline Cartilage
-look like frosted glass
-support flexibility and resilience
-most abundant skeletal cartilage
-spherical chondrocytes
What are the different kinds of Hyaline cartilage?
1) Articular cartilage - ends of bones at movable joints
2) Costal - connect ribs to sternum
3) Respiratory - skeleton of larynx, reinforce other respiratory passageways
4) Nasal - support external nose
Elastic Cartilage
-resemble hyaline
-more stretchy elastic fibers aid in repeated bending
-found in external ear and epiglottis
Fibrocartilage
-highly compressible
-great tensile strength
-roughly parallel rows of alternating chondrocytes and thick collagen fibers
-occur in areas subjected to pressure and stretching (menisci, intervertebral discs)
What kind of Matrix does cartilage have?
Flexible, to accommodate mitosis
What are the two ways that cartilage grows?
Appositional and Interstitial growth.
Describe appositional growth
cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue
Describe Interstitial growth
the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within
Compare cartilage and bone
*Cartilage
Surrounded by perichondrium
No blood vessels or nerves
Chondrocytes in lacunae
Flexible extracellular matrix (made by chondroblasts)
Appositional growth and interstitial growth
*Bone
Surrounded by periosteum
Blood vessels and nerves throughout
Osteocytes in lacunae
Rigid extracellular matrix (made by osteoblasts)
Appositional growth only
What are the 7 important functions of bone?
1) Support
2) Protection
3) Anchorage
4) Mineral storage (calcium and phosphate)
5) Blood cell transformation (hematopoiesis in bone marrow)
6) Triglyceride (fat) storage (in yellow marrow)
7) Hormone production (osteocalcin)
What does osteocalcin do?
Helps regulate:
1) insulin secretion
2) glucose homeostasis
3) energy expenditure
How many bones in the body?
What are the two groups?
206 named bones
Axial and Appendicular
What bones does the axial skeleton consist of?
Skull, vertebral column, rib cage
These bones protect, support and carry other body parts
What bones does the appendicular skeleton consist of?
upper and lower limbs and girdles (shoulder and hip bones)
These bones help us move and manipulate our environment
What are the classification of bones according to shape?
Long
Short
Flat
Irregular
Describe long bones
-longer than they are wide
-has a shaft plus two ends
-all limb bones except patella, wrist, and ankles
Describe short bones
-roughly cube shaped
-bones of wrist and ankle
-include special type of bone called sesamoid bone (form in a tendon).
What do sesamoid bones do
Some alter the direction of pull of tendon, others reduce friction and modify pressure on tendons to reduce abrasion or tearing.
Flat bones
-thin, flattened, a bit curved
-sternum, scapulae, ribs, most cranial bones
Irregular bones
-complicated shape
-Vertebrae, hip bones
What are the three levels of bone structure?
Gross
Microscopic
Chemical
Dense outer layer of every bone
Compact bone (smooth and solid looking)
What lies internal to compact bone?
Spongy bone (Trabecular bone)
What are the open spaces between trabeculae filled with?
Red or Yellow bone marrow
Describe the gross structure of short, irregular, and flat Bones
-thin plates of spongy bone (diploë) covered by compact bone
-connective tissue on either side of compact bone (periosteum and endosteum)
-not cylindrical (no shaft/expanded ends)
-bone marrow but no well defined marrow cavity
-hyaline covers surfaces
-form movable joints with neighbors
Describe the gross structure of a typical long bone
Shaft, bone ends, and membranes
Diaphysis (shaft)
-long axis of bone
-made of a thick collar of compact bone that surrounds the medullary cavity (marrow cavity), which contains yellow marrow
-thin layer of spongy bone between compact bone and marrow cavity
Epiphyses (Bone ends)
-compact bone exterior
-spongy bone interior
-thin layer of hyaline cartilage on joint surface (stress absorption)
Epiphyseal line
Remnant of growth plate in between the epiphysis and diaphysis
Epiphyseal plate (growth plate)
Disc of hyaline cartilage that grows to lengthen bone
Metaphysis
Flared portion of bone where diaphysis and epiphysis meet
What is the periosteum?
glistening, white, double layered membrane that covers external surface of bone (except joint surfaces). It is richly supplied with nerve fibers and blood vessels
What does the outer fibrous layer of periosteum consist of?
Dense irregular connective tissue
What does the inner osteogenic layer of periosteum consist of?
osteoprogeniter cells
What are osteoprogeniter cells?
Primitive stem cells that give rise to most bone cells
What does the periosteum do?
-provides anchoring points for tendons and ligaments
What are perforating fibers and what do they do?
Bundles of collagen fibers extending into bone matrix
They secure the periosteum to the underlying bone
They are thicker at points of tendons and ligaments
What is endosteum and where is it located?
it is a delicate connective tissue membrane that covers internal bone surfaces (trabeculae of spongy bone and lining of canals passing through compact bone)
contains the same cell types as periosteum
What are the main blood vessels in diaphysis
Nutrient artery and nutrient vein, togetherrunning through a hole in the wall of the nutrient foramen
Where is the nutrient artery found?
runs inward to supply the bone marrow and spongy bone
branches extending outward to supply compact bone
Hemopoetic tissue
blood forming, aka red bone marrow
where is red marrow found in infants?
medullary cavity of the diaphysis
all areas of spongy bone
where is red marrow found in adults?
much of red marrow, esp in long bones is replaced by yellow marrow
the fat-containing yellow marrow extends well into the epiphysis
remaining red marrow found in cavities between trabeculae in:
1) flat bones of skull, sternum, rubs, clavicle, scapulae, hip bones, vertebrae
2) heads of femur and humerus
Where is hemopoiesis more active?
flat and irregular bones
What are the three categories of bone markings
1) projections- sites of muscle and ligament attachment
2) surfaces- form joints
3) depressions and openings- for blood vessels and nerves
What are the 5 major cell types in bone tissue?
Osteoblasts
Osteocytes
Osteoprogenitor cells
Bone lining cells
osteoclasts
Which type of bone cell does not originate from embryonic connective tissue cells?
Osteoclasts
Osteoprogenitor cells
aka osteogenic cells
mitotically active stem cells
found in membranous periosteum and endosteum
flattened or squamous in growing bones
differentiate into osteoblasts when active
Osteoblasts
Bone forming cells that secrete bone matrix
actively mitotic
play a role in matrix calcification
Cube shaped when actively depositing matrix
flattened when inactive
become osteocytes when they are complete surrounded by the matrix
Osteocytes
Spidery
mature bone cells
lacunae conform to their shape
monitor and maintain the bone matrix
stress sensors that respond to mechanical stimuli
communicate stress info to cells responsible for bone remodeling so matrix can be built or degraded based on stress amounts
can trigger bone remodeling to maintain calcium homeostasis
What bones are responsible for bone remodeling?
Osteoblasts and osteoclasts
Bone lining cells
Flat cells on bone surfaces (no bone remodeling)
help maintain the matrix
Osteoclasts
Giant multinucleate cells
found at sites of bone resorption (breakdown)
derived from WBC lineage that gives rise to macrophages
osteoclasts lie in shallow carved out depressions when breaking down bone
they have a ruffled border that directly contacts the bone
What does the plasma membrane of the distinct ruffled border of osteoclasts do?
Increase surface area for enzymatically degrading bone
seal off area from surrounding matrix
Osteon
structural unit of compact bone
tiny weight bearing pillars
What makes an osteon a twister resister?
collagen fibers of adjacent lamellae running in opposite directions
Central Canal
contains small blood vessels and nerve fibers to supply osteon cells
Perforating Canal
connect the blood and nerve supply of the medullary cavity to the central canals
How is Caniculi formed
osteoblasts secrete bone matrix, get trapped in it as it hardens and become osteocytes
system of tiny canals filled with tissue fluid and osteocyte extensions
What do caniculi do?
tie osteocytes together in mature osteon allowing them to communicate and relay nurtients and wastes
How do nutrients reach osteocytes of spongy bone?
diffusing through the canaliculi from capillaries in the endosteum surrounding the trabeculae
Organic components of bone
help resist tension (stretch)
osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts and osteoid
contribute to bone structure, flexibility and tensile strength
what are sacrificial bonds?
found between collagen molecules
stretch and break easily on impact
Inorganic components of bone tissue
hydroxyapatites (mineral salts)
calcium phosphates packed in crystals in and around collagen fibers in extracellular matrix
contribute to hardness of bone
