l8 ii connective tissue part 2

8/2/2019 L8 II Connective Tissue Part 2

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Connective Tissues Part 2


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ObjectivesDiscuss the structural and functional

characteristics of bone

Discuss the process of bone formationDiscuss structural and functional

characteristics of cartilage and adipose

tissue


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Bones

Cells + type I collagen (osteoid)mineralzies by

deposition of calcium hydroxyapatite rigid bones Cells

Osteoblasts

Produce osteoid and mediate its mineralisation

Lined up along bone surfaces Osteocytes

Assist in bone nutrition

Inactive osteoblasts trapped within formed bone

Oscteoclasts

Involved in constant turn over and refashioning ofbone

Erodes bone


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Bone cells

Osteoblasts & Osteocytes Osteoclasts


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Structure of bone


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Structure of bone


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Structure of bone

Haversian system

AKA osteon

basic unit, hollow

laminated rod ofcollagen and calciumphosphate

Haversian canal

hollow core of haversiansystem; nutrientchannel


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Structure of bone

Volkmanns canal

Perforating holeswithin the compact

bone Run within osteon

perperdicular toHaversian canal

Connects Haversiancanal to each otherand to the periostem


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Bone structure

Lacunae

deposition of successivelamellaediameter of

Haversian canaldecreases and osteblastsare trapped asosteocytes spaceenclosing it is known aslacunae


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Structure of bone

Compact / corticalbone

Many haversiansystems are

bundled togetherin parallel

Cancellous /spongy/ trabecular

bone Haversian system

branch out


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Structure of bone

Compact bone/cortical bone

Hard outer layer of

bones Porosity 5-30%

Account s80% oftotal bone mass in

adults Gives bone smooth,

white solidappearance


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Structure of bone

Cancellous /trabecular bone

Interior of the bone

Porous 20% of bone mass

Allow room forblood vessels and

marrow


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Compact and trabecular bone


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Functions of the bone

Mechanical function

Protection : protect internal organs (brain, heart, lungs) Structure: frame that supports body

Movement: function with skeletal muscles, tendons,ligaments, joints to execute movement

Sound transduction: overshadowed hearing

Synthetic function

hematopoiesis

Metabolic function Mineral storage (calcium and phosphorus)

Growth factor storage (insulin-like growth factor,transforming growth factor, bone morphogenetic

proteins


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Functions of the bone

Metabolic function Fat storage : yellow bone marrow (store fatty

acids)

Acid

base balance: absorb / release alkalinesalts (pH buffer)

Detoxification: remove heavy metals and foreignobjects from the blood; gradually secretes these

objects Endocrine organ: release osteocalcin (regulates

blood sugar and fat deposition)


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Bone formation

Endochondralossification

Formation of acontinuously growingcartilage model which isprogressively replacedby bone

Bones formed are calledcartilage bones

Long bones, pelvis,bones of the base of theskull


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Bone formation (Endochondral)

Permits functionalstresses during skeletalgrowth

Model of the long bone

first formed in a solidhyaline cartilageelongates into a dumb-bell shaped mass

(consisting of diaphysisand epiphysis)


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Cartilage matrix in thediaphysis becomescalcified periosteumdevelopsprimitive

mesenchymal cells andblood vessels invade thespacesprimitivemesenchymal cells

differentiate intoosteoblasts andhematopoeitic cells ofbone marrow


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Cartilage at the end ofthe diaphysis regress andossify semilunarcartilage (epiphysis)

Epiphysial plate:interface between shaftand epiphysis

Cartilage proliferatescontinouslyelongation of bone


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Bone formation (Intramembranous)

Occurs within membranes of primitive mesenchymaltissue

Mesenchymal cells differentiate into osteoblasts(synthesis and secrete osteoid)mineralizationfollowsosteoblasts are trapped into lacunae tobecome osteocytes

Collagen fibers are arranged in random interlacing

bundles

woven bone Bones of the vault of the skull, maxilla and mandible


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Bone formation (Intramembranous)


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Cartilage

Predominance ofproteoglycans in theetxracellular matrix

Hyaline cartilage

Contains few fibers

Fibrocartilage

contains abundantcollagen fibers

Elastic cartilage

Contains elastic fibers


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Cartilage Most cartilage are devoid of blood vessels

Hyaline cartilage

Nasal septum, larynx, tracheal rings Elastic cartilage

External ear and external auditory canal

epiglottis

Fibrocartilage Articular cartilage

Intervertebral discs


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Adipose tissue Storage of fat

Develop from liboblasts


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Have a nice day...!

l8 ii connective tissue part 2

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