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Figure 4.8g Connective tissues.

(g) Cartilage: hyaline

Description: Amorphous but firmmatrix; collagen fibers form animperceptible network; chondroblastsproduce the matrix and when mature(chondrocytes) lie in lacunae.

Function: Supports and reinforces;has resilient cushioning properties;resists compressive stress.

Location: Forms most of theembryonic skeleton; covers the endsof long bones in joint cavities; formscostal cartilages of the ribs; cartilagesof the nose, trachea, and larynx.

Photomicrograph: Hyaline cartilage from thetrachea (750x).

Costalcartilages

Chondrocytein lacuna

Matrix

Pg 135

Chondroblast -> Chondrocyte (Lacunae)Firm ground substance (chondroitin sulfate and water)Collagenous and elastic fibersNo BV or nervesPerichondrium (dense irregular)

Thickness?Metabolism?

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Figure 6.1 The bones and cartilages of the human skeleton.

Axial skeleton

Appendicular skeleton

Hyaline cartilages

Elastic cartilages

Fibrocartilages

Cartilages

Bones of skeleton

EpiglottisLarynx

TracheaCricoidcartilage Lung

Respiratory tube cartilagesin neck and thorax

ThyroidcartilageCartilage in

external earCartilages innose

ArticularCartilageof a joint

Costalcartilage

Cartilage inIntervertebraldisc

Pubicsymphysis

Articular cartilageof a joint

Meniscus (padlikecartilage inknee joint)

Pg 175

SupportSmooth surfaceCushions

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Figure 4.8g Connective tissues.

(g) Cartilage: hyaline

Description: Amorphous but firmmatrix; collagen fibers form animperceptible network; chondroblastsproduce the matrix and when mature(chondrocytes) lie in lacunae.

Function: Supports and reinforces;has resilient cushioning properties;resists compressive stress.

Location: Forms most of theembryonic skeleton; covers the endsof long bones in joint cavities; formscostal cartilages of the ribs; cartilagesof the nose, trachea, and larynx.

Photomicrograph: Hyaline cartilage from thetrachea (750x).

Costalcartilages

Chondrocytein lacuna

Matrix

glassy

Pg 135

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Figure 4.8h Connective tissues.

(h) Cartilage: elastic

Description: Similar to hyalinecartilage, but more elastic fibersin matrix.

Function: Maintains the shapeof a structure while allowinggreat flexibility.

Location: Supports the externalear (pinna); epiglottis.

Photomicrograph: Elastic cartilage fromthe human ear pinna; forms the flexibleskeleton of the ear (800x).

Chondrocytein lacuna

Matrix

Pg 135

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Figure 4.8i Connective tissues.

(i) Cartilage: fibrocartilage

Description: Matrix similar tobut less firm than that in hyalinecartilage; thick collagen fiberspredominate.

Function: Tensile strengthwith the ability to absorbcompressive shock.

Location: Intervertebral discs;pubic symphysis; discs of kneejoint.

Photomicrograph: Fibrocartilage of anintervertebral disc (125x). Special stainingproduced the blue color seen.

Intervertebraldiscs

Chondrocytesin lacunae

Collagenfiber

Pg 136

Tough!Forms discs and pads

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Figure 6.7 Microscopic anatomy of compact bone.

Endosteum lining bony canalsand covering trabeculae

Perforating (Volkmann’s) canal

Perforating (Sharpey’s) fibers

Periosteal blood vesselPeriosteum

Lacuna (withosteocyte)

(a)

(b) (c)

Lacunae

Lamellae

NerveVeinArtery

CanaliculiOsteocytein a lacuna

Circumferentiallamellae

Osteon(Haversian system)

Central(Haversian) canal

Centralcanal

Interstitial lamellae

Lamellae

Compactbone

Spongy bone

Pg 182

SupportProtectionBlood formationStorehouseMovement

Hydroxyapatite (calcium salts)Bone Cells -osteoblast -osteocyte -osteoclastPeriosteum (dense irr.)2 types of bone

osteoblast

Osteoblasts & clasts

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Proximalepiphysis

(b)

(c)(a)

Yellowbone marrow

Endosteum

Epiphysealline

Articularcartilage

Periosteum

Spongy bone

Compact boneMedullarycavity (linedby endosteum)

Compact bone

Compact bone

Periosteum

Perforating(Sharpey’s)fibers

Nutrientarteries

Diaphysis

Distalepiphysis

Figure 6.3 The structure of a long bone (humerus of arm).

Pg 178

Spongy = Cancellous

Spaces contain marrowTrabeculae

-Ends of long bones-Shaft of young bones-In flat, short and irregular bones

8 days/20%

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Figure 6.7 Microscopic anatomy of compact bone.

Endosteum lining bony canalsand covering trabeculae

Perforating (Volkmann’s) canal

Perforating (Sharpey’s) fibers

Periosteal blood vesselPeriosteum

Lacuna (withosteocyte)

(a)

(b) (c)

Lacunae

Lamellae

NerveVeinArtery

CanaliculiOsteocytein a lacuna

Circumferentiallamellae

Osteon(Haversian system)

Central(Haversian) canal

Centralcanal

Interstitial lamellae

Lamellae

Compactbone

Spongy bone

Pg 182

Compact forms shaft of long bones and a shell over spongy bone

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Figure 4.8j Connective tissues.

(j) Others: bone (osseous tissue)

Description: Hard, calcifiedmatrix containing many collagenfibers; osteocytes lie in lacunae.Very well vascularized.

Function: Bone supports andprotects (by enclosing);provides levers for the musclesto act on; stores calcium andother minerals and fat; marrowinside bones is the site for bloodcell formation (hematopoiesis).

Location: Bones

Photomicrograph: Cross-sectional viewof bone (125x).

Lacunae

Lamella

Centralcanal

Pg 137

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Figure 6.2 Classification of bones on the basis of shape.

(a) Long bone(humerus)

(b) Irregular bone(vertebra), rightlateral view

(d) Short bone(talus)

(c) Flat bone(sternum)

Pg 176

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Figure 6.3a The structure of a long bone (humerus of arm).

Proximal epiphysis

(a)

Epiphyseal line (plate)

Articularcartilage

Periosteum

Spongy bone

Compact boneMedullarycavity (linedby endosteum with clasts & blasts)Diaphysis

Distal epiphysis

Pg 178

Red-> Yellow

Formation of bony skeleton

Intramembranous: cranial bones, mandible, part of clavicle

Endochondral: Most bones of the body

Bone is only deposited in an area with less highly specialized connective tissue.

Intramembranousmesenchyme -> Dense Irr. -> Spongy -> Compact

C.T. Bone Bone (inside)

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Figure 6.9 Intramembranous ossification.

1 Ossification centers appear in the fibrous connective tissue membrane.• Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae ofspongy bone.

Mesenchymal cell

Collagen fibril

Ossification center

Osteoid

Osteoblast

Osteoblast

Osteoid

Osteocyte

Newly calcifiedbone matrix

Mesenchymecondensingto form the periosteum

Trabeculae ofwoven bone

Blood vessel

2 Osteoid is secreted within the fibrous membrane and calcifies.• Osteoblasts begin to secrete osteoid, which calcifies in a few days.• Trapped osteoblasts become osteocytes.

3 Woven bone and periosteum form.• Accumulating osteoid is laid down between embryonic blood vessels in a manner that results in a network (instead of concentric lamellae) of trabeculae Called woven bone.• Vascularized mesenchyme condenses on the external face of the woven bone and becomes the periosteum.

Fibrous periosteum

Osteoblast

Plate ofcompact bone

Diploë (spongy bone)cavities contain red marrow

4 Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears. • Trabeculae just deep to the periosteum thicken. Mature lamellar bone replaces them, forming compact bone plates.• Spongy bone (diploë), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow.

Pg 185

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Figure 6.5 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.

Compactbone

Trabeculae

Spongy bone(diploë)

Layers?

Pg 177

Bone is only deposited in an area with less highly specialized connective tissue.

Intramembranousmesenchyme -> Dense Irr. -> Spongy -> Compact

C.T. Bone Bone (inside)

Endochondralmesenchyme -> Hyaline -> Spongy -> Compact

Cartilage Bone Bone

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Figure 6.9 Endochondral ossification in a long bone.

1 2 3 4 5 Bone collarforms aroundhyaline cartilagemodel.

Cartilage in thecenter of thediaphysis calcifiesand then developscavities.

The periostealbud invades theinternal cavitiesand spongy bonebegins to form.

The diaphysis elongatesand a medullary cavityforms as ossificationcontinues. Secondaryossification centers appearin the epiphyses inpreparation for stage 5.

The epiphysesossify. Whencompleted, hyalinecartilage remains onlyin the epiphysealplates and articularcartilages.

Hyalinecartilage

Area ofdeterioratingcartilage matrix

Epiphysealblood vessel

Spongyboneformation

Epiphysealplatecartilage

Secondaryossificationcenter

Bloodvessel ofperiostealbud

Medullarycavity

Articularcartilage

Childhood toadolescence

BirthWeek 9 Month 3

Spongybone

Bonecollar Primaryossificationcenter

Pg 184

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Figure 6.11 Long bone growth and remodeling during youth.

Bone growth Bone remodeling

Articular cartilage

Epiphyseal plate

Cartilagegrows here.

Cartilageis replacedby bone here.

Cartilagegrows here.

Bone isresorbed here.

Bone isresorbed here.

Bone is addedby appositionalgrowth here. Cartilage

is replacedby bone here.

Pg 186

In Length: Until end of puberty

Endochondral

In Width (appositional): occurs throughout life

Achondroplasia

Hormonal Control of Skeletal SystemGrowth Hormone

-Anterior Pituitary Gland-Stimulates mitosis of cartilage at epiphyseal plates and growth of bones in length-Giantism, Acromegaly, Pituitary Dwarfism

Thyroxine-Thyroid Gland-Works with Growth Hormone to regulate bone

growth and regulates osteoblast activity.Sex Hormones (Estrogen and Testosterone)

-Ovary and Testes-Stimulates bone growth in adolescence (surge closes plates)-Stimulates bone maintenance in adulthood.

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Figure 6.12 Parathyroid hormone (PTH) control of blood calcium levels.

Calcium homeostasis of blood: 9–11 mg/100 mlBALANCE BALANCE

StimulusFalling bloodCa2+ levels

Thyroidgland

Parathyroidglands

Parathyroidglands releaseparathyroidhormone (PTH).

Osteoclastsdegrade bonematrix and releaseCa2+ into blood.

PTH

IMBALANCE

IMBALANCE

Pg 188

Calcitonin ?

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Clicker Question: In a patient whose parathyroid glands have been removed, you would expect that person's blood calcium levels to _______.

A. decreaseB. increaseC. stay the sameD. increase twofold

Osteoporosis

Estrogen-Reduced with menopause-Loss of bone massCalciumVitamin DExercise

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Figure 6.16 The contrasting architecture of normal versus osteporotic bone.

Pg 192

fibrous

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Figure 6.15 Stages in the healing of a bone fracture.

Hematoma Externalcallus

Bonycallus ofspongybone

Healedfracture

Newbloodvessels

Spongybonetrabecula

Internalcallus(fibroustissue andcartilage)

1 A hematoma forms. 2 Fibrocartilaginouscallus forms.

3 Bony callus forms. 4 Boneremodelingoccurs.

Pg 191

Intramembranous & EndochondralOsteoclasts & Osteoblasts