chapter 6 osseous tissue and bone structure Flashcards
Skeletal system includes
Bones of the skeleton 206
Cartilages, ligaments, and connective tissues
Skeletal muscle
The framework for the body
Osseous tissue
Is the hardened matrix that gives strength to the bones
Osseous tissue does what
- hardened by the process of calcification ; calcium phosphate
- continually remodels itself (living)
Functions of the skeletal system
-support
-protection
Enclose vital organs
-leverage
Allows movement from muscle action
-mineral storage
Calcium
Phosphate
-blood formation
RBC and WBC
Bone
Consists of osseous tissue, marrow, cartilage, periosteum
Bones are classified according to?
-shape
Long, short, flat, and irregular
Sutural and sesamoid bones are less common shapes
Bone structure (internal tissues)
-compact bone is dense bone tissue
- spongy bone (cancellous) is loosely organized bone tissue
Always surrounded by compact tissue
Long bone
Are longhand slender;levers for muscles
-legs and arms
Include feet/toes, hands/fingers
Short bones
Are nearly equal in length and width; limited gliding in multiple directions
-carpals (writs) and tarsals (ankles)
Flat bones
Are thin with parallel surfaces
-protect organs and offer extensive surface area for muscle attachment
Flat bones are found
- skull, sternum, and ribs
- scaplua
- os oxae (hip bones)
Irregular bones
Have complex shapes with short, flat, or ridged surfaces
Irregular bones are found in
-vertebrae
-skull
Ethmoid and sphenoid
Long Bone Characteristics
- diaphysis has a heavy wall of compact bone
- epiphysis is a spongy bone covered with compact bone
- metaphysis is where diaphysis and epiphysis meet
Diaphysis
- transfers stress/weight between epiphysis
- contains marrow (medullary) cavity
Epiphysis
Enlarged to strengthen joint and attach ligaments
Metaphysis
- bone lengthening occurs here along epiphyseal plate
- in adults epiphyseal plate becomes epiphyseal line
Articular cartilage
Is a hyaline cartilage that covers the ends of long bones allows for ease of mobility at the joints
-component of synovial capsule
Nutrient foramina
Allow for blood vessels and nerves to enter bone
Bone linings
Periosteum
Endosteum
Periosteum
Lines the outer shaft
- outer fiberless layer(collagen) & inner cellular layer
- isolates bones from surrounding tissues
- provides a route for circulatory and nervous supply
- participates in bone growth and repair
Endosteum
- incomplete cellular layer, some matrix is exposed
- exposed matrix contains primary bone cells
- active in bone growth/repair by removing and re-depositing matrix
Osseous tissue is
A connective tissue that contains fibers, ground substance, and specialized cells
4 types of bone cells
- osteocytes
- osteoblasts
- osteoprogentior cells
- osteoclasts
Osteocytes
Are mature bone cells living in lacunae that maintain the bone matrix
- do not dived
- connected by gap junctions and cytoplasmic extensions through canaliculi in matrix
Osteocyte functions
- maintain protein and mineral content of matrix
- help repair damaged bone
Osteocytes account for most of
Bone cell population
Osteoblasts
Are immature bone cells that secrete organic compounds (osteoid) to produce bone matrix
- matrix hardens via mineral (calcium) deposition
- replacing non-osseous tissue with bone is osteogenesis
- calcium deposition in non osseous tissue is ossification
Osteogenic cells
Are mesenchymal stem cells that divide to produce most other bone cells
-located in (inner) cellular layer of periosteum and endosteum
*only source of new bone cells (done differentiate into osteoblasts)
Osteoclasts
Are giant, multinucleated cells that form from the fusion of 3-50 stem cells; related to macrophages of immune system
Secret acids and protein-digesting enzymes to
dissolve bone matrix and release stored minerals (osteolysis)
-important in the regulation of CA+ and PO4
Homeostasis and osseous tissue
-bone building (osteoblasts) and bone recycling (osteoclasts) must balance
More breakdown than building, bones become weaker
Couch potatoes
More building than breakdown, bones become stronger
Exercising individuals
Osteoblasts and osteoclasts actions must
Balance
Matrix of osseous tissues is a
Crystalline-protein complex of organic and inorganic matter
Provides for strength and resilience
Combination of materials is called a composite
Combination of materials is called a composite
Minerals resist compression while collagen resists tension
Organic matter includes
- collagen (primary)
- proteoglycans and glycoproteins
Inorganic matter includes
- 85% hydroxyapatite
- 10% calcium carbonate and other minerals
Compact bone
Osseous tissue is cylindrical with layers if concentric lamellae arranged around central canals
Forms
Osteon
Basic structural unit of bone
Osteons are secured by two types of lamellae
-interstitial lamellae
-circumferential lamellae
Outer boundary of compact bone
Osteons receiver blood via perforating canals (volkmann canals)
-vascular canals that perpendicularly join central canals
Spongy bone
Has a sponge-like appearance due to struts of bone called trabeculae
-has open network with no central canals (does not have osteons)
Nutrients and waste diffuse through canaliculi
2 types of marrow in spongy bone
Red marrow
Yellow marrow
Red marrow(hemopoietic)
contains blood vessels and forms red blood cells
Axial skeleton and proximal heads of femur and humerus in adults
Yellow marrow
Present in some long bones for lipid storage
Spongy bone provides strength with
Little weight
Bone growth and elongation occurs at the ______ ______ that function as growth zones
Epiphyseal plates
Interstitial growth
Increases bone length
Multiplication of chondrocytes balances bone deposition at metaphysis
Epiphyseal line is left behind when cartilage is completely replaced
Appositional growth
Increases bone width
In appositional growth osteoblasts lay down matrix in layers on inner surface of
Periosteum
Produces circumferential lamellae
Epiphyseal plates and lines
Wen long bones stop growing after puberty epiphyseal cartilage disappears
Visible on x rays as an
Epiphyseal line
Bones are remodeled through life by
Absorption (old bone)
Deposition (new bone)
Wolfs law of bone
States that architecture of bone is determined by mechanical stress
Greater density and mass of bone is adaptation to increased stress
Remodeling may or may not
Change bone shape, internal architecture or mineral content
Factors affecting bone growth
- rapid growth At puberty
- premature closure of growth plate
Rapid growth at puberty
-hormones stimulate oseteogenic cells, chondrocytes and matrix deposition in growth plate
Girls grow faster than boys and reach full height earlier
-estrogen stronger effect
Males grow for longer time and are taller
Premature closure at growth plate
Short adult stature
Teenage use of antibolic steroids
Endochodral ossification
Forms bone from a pre-existing model of hyaline cartilage
Most bones originate as hyaline cartilages
6 steps of endochrondral ossification
- cartilage framework formation
- formation of primary ossification center
- vascularization
- formation of secondary ossification center
- epiphyses formation
- epiphyseal ossification
Endochrondral ossification
Cartilage formation and
Primary ossification center
Endochrondral ossification
Chondrocytes
In the center of hyaline cartilage enlarge and expand lacunae
-expanding forces matrix to form struts
Stem cells of perichondrium become ______ and matrix begins to calcify
Osteoblasts
Calcified cartilage does not allow
Nutrient diffusion
Chondrocytes die leaving
Cavities
Blood vessels enter the cartilage cavities and form
Primary ossification center
Remodeling creates primary
Marrow cavity
Stem cells become
Osteoblasts and osteoclasts
Ossification spreads towards cartilage ends
Bone replaces cartilage at the metaphysis
Massive cartilage death occurs increasing marrow cavity size
Capillaries and osteoblasts migrate to the epiphysis creating
Secondary ossification centers
Endochrondral ossification
Epiphyseal classification
-vascularization of secondary ossification centers results in a secondary marrow cavity of epiphyses
-epiphyses fill with spongy bone
Cartilages within the joint cavity becomes articulation cartilage
Cartilage at the metaphysis is epiphyseal plate
Plates provide for increase in length of bone during childhood and adolescence
-by early twenties epiphyseal plates fuse and primary and secondary marrow cavities unite
Intramembranous ossification
Produces bones that develop within flat fibrous sheet
Referred to as dermal bones
Dermal bones
Mandible, clavicle,and bones of skull
4 steps of intramembranous ossification
-mesenchyme condenses into soft trabeculae
Mesenchyme cells become osteoblasts
-osteoblasts deposit osteoid
CA10 PO4 is deposited in the matrix forming spongy bone
Some osteoblasts become osteocytes; vascularization occurs
-osteoclasts remodel bone to create marrow cavity
- surface mesenchyme becomes periosteum
Calcium
Is needed in neurons, muscle contraction, bones, blood clotting (co-enzymes) and exocytosis
Calcium homeostasis is ______ regulated; imbalances are Rare- changes in calcium can be ____
Highly;serious
Imbalances in calcium changes can cause
- heart arhythmias and arrest
- skeletal muscle tetanus
- hemorrhaging
A primary function of osseous tissue is _____ ______
Calcium homeostasis
Calcium homeostasis is affected by
- calcium deposition and resorption
- hormonal influences
- nutrition
Calcium deposition and resorption
Mineralization
Mineral resorption
Mineralization
Is the crystallization process utilizing CA2+ (cation) , PO4^3-(anion)
Osteoblasts produce minerals to cover the collagen fibers and harden matrix
Ion concentration must reach the solubility product for crystal formation to occur (precipitate)
Mineral resorption
Is e process of dissolving bone and releasing minerals into blood
-hydrogen pumps in osteoclasts secrete HCL into extra cellular space
Dissolves bone minerals
Calcium regulation and hormones
CA2+ ions are vital to intercellular activities of neurons and muscle, especially heart cells
-most abundant mineral in the body;daily fluctuations of more than 10% is rare
99%is in skeleton
Calcium uptake/excretion is regulated via the
Endocrine system
3 hormones of calcium regulation
- parathyroid hormone (PTH)
- calcitonin
- calcitriol
Calcitriol has a weak influence while ____ and ____ are _______ with a strong influence
PTH
calcitonin
Antagonist
PTH
Produces by parathyroid glands increases CA2+ level
PTH does what
-stimulates osteoclasts releasing CA2+ from bone
- enhances CA2+ absorption by intestines
- decreases CA2+ excretion by kidneys
Stimulates Renal production of calcitriol
Calcitonin
secreted by C cells in thyroid decreases CA2+ level
Calcitonin does what
- inhibits osteoclast activity
- reduces Ca2+ absorption by the intestines
- increases Ca2+ excretion by kidneys
PTH released when Ca2+ is ____ normal; calcitonin is released when Ca2+ is _____ normal
Below
Above
Calcitriol
Raises blood Ca2+ concentration; synthesized in the kidneys
Derivative of vitamin D3
Produced by UV radiation and epidermal keratinocytes
Effects of calcitriol
-increases stem cell differentiation into osteoclasts
Raises Ca2+ resorption
-promotes urinary reabsorption of Ca2+
-promotes intestinal absorption of Ca2+
Lack of calcitriol or vitamin D causes in
Rickets (children) or osteomalacia (adults)
Ca2+ ion disorder
-hypocalcemia is deficiency of blood Ca2+ that causes excitability of nervous system and muscles
Na+ channels open more easily, Na+ enters cell exciting neuron (begins around 6mg/dl)
Muscle spams, tremors or tetany
Hypercalcemia
Is excess of blood Ca2+ that depresses nerve response and muscle contraction
Sodium channels are less likely to open (begins at 12mg/dl)
Muscle weakness, sluggish reflexes, and cardiac arrest
Fractures
Are cracks/breaks in bone caused by physical stress, extreme loads, or sudden impacts
Maybe a stress fracture (____) or pathological fracture (____)
Trauma
Disease
Classified by break characteristics
Oven vs closed
Simple vs complex
Open vs closed
Protruding from the skin or not
Simple vs complex
Two or more pieces
Most fractures heal in
8-12 weeks longer in elderly
Healing of fractures steps
- Formation of fracture hematoma
- Formation of soft callus
- Hard callus
- Bone remodeling
Formation of fracture hematoma
Extensive bleeding produces a clot that establishes a fibrous network from damage
Granulation tissue
Formation of soft callus
-cells of endosteum and periosteum divide and migrate into fracture zone
Produce fibers and ffibrocartlage
- callus forms to stabilize the break
External callus is Cartilage /bone and surrounds break
Internal callus of spongy bone develops in marrow cavity
Hard callus
-osteoblasts replace central cartilage of external callus with spongy bone
Spongy bone unites broken ends
-fracture is secured in place; can withstand normal stresses from muscle contractions
Bone remodeling
-osteoblasts and osteocytes remodel the fracture for up to a year
Reduces bone calluses
Treatment of fractures
Closed reduction
Open reduction
Closed reduction
Is when fragments are aligned with manipulation and casted
Open reduction
Is surgical exposure and repair with plates and screws
Age and bone
Bones become thinner and weaker within age
Women lose 8% of bone mass per decade men 3%
Osteopenia (inadequate ossification )
Begins at age 30 and 40
Results in fragile limbs, height reduction, tooth loss
Epiphyses, vertebrae, and jaw most affected
Estrogen and androgens
No longer help maintain bone mass
Bone loss in women accelerates after menopause
Osteoporosis
Is a severe bone loss that affects normal function
Osteoporosis
Increased risk of fracture of hip, wrist and vertebral column
Complications of pneumonia and blood clotting
Treatment for osteoporosis
-ERT slows down bone resorption
Increases risk of breast cancer, stroke,heart disease
Best treatment is prevention
Exercise and calcium intake 1000 mg/day between ages 25-40
Postmenopausal ____women at greatest risk; _____women rarely suffer symptoms
White
Black
