Bone Osseus Tissue

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Bone (Osseus Tissue) Rigid tissue ? most of
skeleton Contents cells, fibers, ground
substance Distinguishing feature inorganic salts
in ground substance
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GENERAL FEATURES Macroscopic Appearance Compact
hard matter Spongy hard matter Color
(living) pinkish blue Covering
Periosteum Interior Marrow Tissue Interior
lining Endosteum (poorly defined)
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Chemical Composition of Bone Mixture
Organic (living) components tenacity,
elasticity, resilience Inorganic
(non-living) components hardness and
rigidity
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Pure organic bone Decalcification removal
of lime salts using dilute acid Decalcified
bone bone collagen (ossein)
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Spongy Bone vs. Compact Bone Compact bone ?
external (solid) Spongy (cancellous) bone ?
internal (lattice work) Difference degree of
porosity
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CLASSIFICATION OF BONES Every bone contains
compact and spongy bone tissue Amount and
localization varies with the bone Bones
categorized by shape
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Types of Bones based on Shape SHORT
BONES Cubical shape Bones of wrist and
ankle Spongy bone enclosed by compact bone
shell FLAT BONES Thin rather than flat ribs,
scapula, cranial vault Two plates (compact)
enclose middle layer (spongy) Flat plates
tables Spongy layer diploe
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LONG BONES Cylindrical shape Bones of
limbs Main shaft diaphysis Ends
epiphysis IRREGULAR BONES Irregular/varied
shapes cannot be classified Vertebrae, some
bones of skull Spongy interior, compact exterior
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STRUCTURAL ELEMENTS OF BONE TISSUE Cells
Osteocytes basophilic specialized C.T.
cells Bone developments these cells were
formative cells (Osteoblasts) Imprisoned in
matrix become osteocytes 10 x 35 µ (flat
side) Irregular shape, oval Biconvex (edge
view) Occupy spaces (lacunae/lacuna) in
matrix Minute cell process in canaliculi
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BONE MATRIX Double structure fibrillar base
organic fibers masking substances lime salts
and organic cement Organic component ?
typical collagenous fibers fibrils very fine (3
to 5 µ thick) osteocollagenous fibers (Type I
collagen) Fibers united with cementing
substance
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Cementing Substance PAS stain sulfated
glycosaminoglycans (chondroitin sulfate and
keratin sulfate) Form small proteoglycan
molecules (short protein cores) Glycosaminglyc
ans covalently bonded to cores Proteoglycans
bonded to hyaluronic acid (use link proteins) ?
VERY LARGE aggrecan composites
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Other proteoglycans present in
matrix osteocalcin and osteopontin bind
hydroxyapatite Osteopontin also binds
other components and integrins on osteoblasts
and osteoclasts Sialoprotein also with
binding sites for integrins Importance
cell adherence to matrix
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INORGANIC SALTS Mineral salts 65 of bone
weight Calcium phosphate 85 of inorganic
deposit as hydroxyapatite crystals Hydroxyapatit
e Ca10(PO4)6(OH)2 Crystals ordered arrangement
along Type I collagen fibers
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LACUNAR CAPSULES Lacunae and canaliculi bordered
by special organic cement thin lacunar
capsule Cement differs from other organic
cement more homogeneous higher refractive
index Capsule backened with silver
treatment Capsule resistant to strong acids Not
affected by hot alkali (unlike ordinary matrix
cement)
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LAMELLAE Matrix in layers (lamellae) 3 to 7 µ
thick Lamellae in parallel series (flat or
curved) Result from rhythmic deposition of
matrix Fibers of adjacent lamellae interweave
general course is parallel Fiber direction
alternates (adjacent lamellae) maximizes
rigidity and strength Arranged in sets (Haversian
Systems Periosteal Lamellae) Adjacent sets
delimited by refractile cement membrane
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LACUNAE Shape melon seed 35 x 10 x 6 µ Orderly
arrangement (includes associated
canaliculi) Flat surface parallel to
lamellae Lacunae between lamellae or within
lamella Canaliculi branch and anastomose freely
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BONE ARCHITECTURE PERIOSTEUM Fibrous
sheath Covers bone except articular
surface United to underlying bone Firm on short
bones, epiphyses where tendons and ligaments
insert Bolting down (Sharpeys fibers)
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Two indistinct layers inner layer looser,more
elastic, more cellular outer layer dense,
fibrous, vascular Blood vessels and nerves from
external layer pass through to bone
tissue Sharpeys fibers leave inner layer and
embed in bone matrix
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SHARPEYS FIBERS
Coarse collagenous fibers or bundles of
fibers Pass from inner periosteum into
matrix Pass through periosteal lamellae
(spikes) perforating fibers
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COMPACT BONE Lamellae in orderly arrangements
minute canals Periosteal and Endosteal
lamellae Parallel lamellae next to these
lamellae Volkmanns canals traverse lamellae
(vertically or at angle) Canals contain blood
vessels, lymphatics, nerves Communicate with
periosteum or marrow cavity
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HAVERSIAN CANALS Canals conduct blood vessels,
lymphatics, nerves Abundant Act as axes of
Haversian systems Largest canals are 0.1 mm
dia. Course long axis of bone Branch and
anastomose and are continuous with Volkmanns
canals Connections between Haversian canals may
be Volkmanns canals
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HAVERSIAN SYSTEMS Only in compact bone Arranged
around a Haversian canal Thick wall, narrow
canal Concentric tubular layers Haversian
lamella Layers are 3 to 7 µ thick Lamellae vary
from 4 to 20 in a system Osteocytes arranged also
in concentric layers Canaliculi communicate with
Haversian canal, peripheral canaliculi curve back
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INTERSTITIAL LAMELLAE Fill spaces between
Haversian systems Irregular in size and
shape Highly variable orientation Remnants of
periosteal lamellae parallel surface little
curved Distinctly curved interstitial lamellae
remnants of Haversian systems (bone remodeling)
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SPONGY BONE Simple structure and not as organized
as compact bone Spongy mass composed of
trabeculae, plates, tubules, golbular
shells Interspaces filled with vascular
marrow Fundamental composition is lamellar Less
regular than compact bone Spongy and compact bone
are continuous
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ENDOSTEUM Delicate layer Lines marrow
spaces Covers irregular surfaces of spongy
bone Continues into canal systems of compact
bone Adult bone endosteum is condensed reticular
tissue BONE MARROW Fills interior of many bones
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BLOOD VESSELS AND NERVES Arterioles enter from
periosteum entry points numerous course in
Volkmann and Haversian canals Venules retrace
pate Arterioles and Venules are
capillary-like Long bones one or more nutrient
arteries enter (midpoint of shaft) Branch
(proximal and distal branches) Nutrient veins
retrace artery path
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Lymphatic vessels exist in various canals Sensory
nerves in periosteum Vasomotor accompany
arterial vessels
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METABOLIC PATHWAYS Bone rich in small vessels
(compact bone) no capillary network in bone
matrix vessels restricted to external and
internal surfaces and canals Spongy bone
vessels largely in marrow spaces Dense matrix
precludes diffusion Canaliculi communicate
between lacunae and canals and to adjacent
periosteum and marrow
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FUNCTIONAL CORRELATIONS Skeletal support for
body Protection of vital organs head, neck,
pelvis Leverage action (muscles/joints) --
locomotion Residence for marrow Low metabolic
rate but not inert Stores calcium a labile
deposit Periosteum helps anchor tendons and
ligaments
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BONE MARROW Fills cavity of compact bone and
intervening spaces of spongy bone Until puberty
all marrow is hemopoietic (red bone marrow) At
puberty much is replaced by fat cells Inactive
fatty marrow Yellow bone marrow Under stress
can reactive ? hemopoietic Aged and emaciated
persons yellow marrow changes Lose oil
content, becomes reddish gelatinous bone marrow
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Marrow framework meshwork of reticular
fibers Between fibers are primitive and
phagocytic reticular cells Sparse fat
cells Vascular relations large tortuous
sinusoids abundant lined by flattened,
phagocytic reticular cells Nutrient marrow
arterioles reduce to capillaries ? empty into
sinsuoids Cells free in meshes of reticulum
blood cells at all stages of development red
and white elements
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FUNCTIONAL CORRELATIONS Yellow marrow adult
dormant hemopoietic tissue Red marrow primary
hemopoietic center of adult
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JOINTS Bone connections articulations Region
of union joint SYNARTHROSES ? immovable
joints Syndesmosis union by dense fibrous
tissue sutures of skull Synchondrosis union
by cartilage (hyaline or fibrocartilage) union
of growing epiphysis/diaphysis, pubic
symphasis, intervertebral disk
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Synostosis union of originally separate bones
by osseous tissue mature epiphysis/diaphysis
and aging sutures of skull DIARTHROSES ?
freely moving joints (cavity between bones) Ends
of bones covered by articular cartilage No
perichondrium Joint capsule envelops
articulation Dense fibrous tissue outer
layer Synovial membrane inner layer
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Synovial membrane Looser vascular
layer Surfaced with fibroblasts
(discontinuous) A false epithelium Surface
may be folded (synovial villi) Secretes glairy,
lubricating synovial fluid dialysate of blood
plasma and lymph Articular disk/meniscus may
project into cavity Disks usually become
fibrocartilage