lec 7: bone tissue

cartilage in external ear

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cartilages in nose

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cartilage in intervertebral disc

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articular cartilage of a joint

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costal cartilage

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pubic symphysis meniscus

padlike cartilage in knee joint

bones of a skeleton:

• axial skeleton

• appendicular skeleton

axial skeleton

80 bones

• protects the VITAL ORGANS

  • skull (cranial/facial bones)

  • vertebral column

  • thoracic cage (sternum, ribs)

appendicular skeleton

126 bones

• enable movement

  • petoral girdle/shoulders

  • arms

  • legs

  • pelvic girdle/hips

cartilages

• hyaline cartilages

• elastic cartilages

• fibrocartilages

hyaline cartilages

MOST COMMON type of cartilage

• contains type II collagen fibers

• reduces friction in joints, absorbs shock and flexible structural support

@: ends of long bones, ribcage, nose, nasal septum, trachea and larynx

elastic cartilage

• high concenrtation of elastic fibers alongside type II collagen

• maintains the shape of structures while allowing a high degree of flexibility and recoil

@: external ear, epiglottis and eustachian tube

fibrocartilage

• toughest and strongest type of cartilage

• packed with type I and type II collagen fibers

• SHOCK ABOSPORTION

@: intervertebral discs, pubic symphysis

roles of skeleton

• support

• protection

• movement

• electrolyte balance

• acid-base balance

• blood formation

• hormone secretion

electrolyte balance

calcium and phosphate levels

• HARD SALT — inorganic material

  • makes up the bone (reduced calcium is bad)

acid-base balance

buffers blood against large pH changes by altering phosphate and carbonate salt levels

blood formation

hematopoisesis tissue (red marrow) in the bone marrow cavities

• found skull, vertebrae, ribsm sternum, part of pevlic girdle and proximal heads of humerus and femur

hormone secretion

bone cells secrete hormones that affect action of insulin and moderate the stress response

long bones

longer than they are wide

@: arms, legs, fingers, humerus, radius, ulna

short bones

• cube shaped bones (wrist and ankle)

• sesamoid bones (tendons and patella)

flat bones

thin, flat, slightly curved

@: face, skull, cranium, stermum, shoulders

irregular bones

• complicated shapes (vertebrae, pelvis)

bone markings:

1. projections

2. articulations

3. depressions

4. passages

projections

• tubercle

• tuberosity

• trochanter

• crest

• process

• spine

tubercle

small, rounded projection

@: greater/lesser tubercles of the humerus, adductor tubercle of the femur

tuberosity

rough projection

@: ischial tuberosity (your booty when ure sitting)

trochanter

larger, rough projection in the femur

crest

prominent and rougher than a ‘line’, making it a major anchoring point

@: iliac crest (hip bone, ridge of the pelvis)

process

prominent outgrowth, bump, ridge or a projection/extension sticking out from the bone

spine

sharp, slender and often pointed projection

articulations (joints)

• head

• facet

• condyle

head

expanded articular end often separated from the shaft by the neck—-fitting into a shallow socket

facet

small, flat articular surface

condyle

smooth, rounded articular knob that fits into a matching depression on another bone

passages

holes → needs to get through

• canal (meatus)

• fissure

• foramen

canal

large passageway through the substance of a bone

@: internal auditory meatus/nasal cavity

fissure

elongated cleft of gap

@: superior orbital fissue

foramen

small, rounded passaageway through which blood vessels or nerves penetrate the bone

depressions:

• fossa

• sulcus (groove)

fossa

broad, shallow depression, pit or hollow surface

@: shoulder blades

sulcus

shallow groove, furrow or linear depression on the surface of an organ, tissue or bone

compact bone

10 years

dense outer layer

spongy (cancellous) bone

3-4 years

• honeycomb of trabeculae

• more porous like a sponge

membranes of a bone

• periosteum

• endosteum

periosteum

new bones are being formed — covered comapct bone on the outside

• outer fibrous layer

• inner osteogenic layer:

  • osteoblasts

  • osteoclasts

  • osteogenic cells

endosteum

covered spongy bone within

• delicate membrane on internal surfaces of bone

• contains osteoblasts and osteoclasts

osteoblasts

bone forming cells —- creates NEW bone

osteoclasts

bone destorying cells — greatest number of lysosomes

• recycle bones

osteogenic cells

stem cells in periosteum and endosteum— turned into osteoblasts/osteoclasts

osteocytes

mature bone cells

microscopic anatomy of compact bone

• haversian system or osteon

  • lamellae

  • central/haversian canal

• perforating/volkmanns canals

• lacunae

• canaliculi

lamellae

• concentric rings — made with a lot of collegen fibers

• gives the bone strength

central/haversian canal

• contains blood vessels and nerves

• blue = vein

• red = arteries

• yelow

volksmann’s canals

• at right angels to the central canal

• connects blood vessels and nervse of the periosteum and central canal

lacunae

small cavities that contain osteocytes

canaliculi

hair-like canals that connect lacunae to each other and the central canal

microscopic anatomy of spongy bone

trabeculae

trabeculae

• no osteons

• contain lamellae, osteocytes and canaliculi

osteogenesis (ossification)

bone tissue formation — usually during puberty, resistance training, breaking/repairing a bone and baby bones

stages:

1. initial formation (embryo and fetus)

2. growth (infancy—adolescence)

3. remodeling (bone throughout l

intramembranous ossification

• direct bone formation

  • membrane bone develops from fibrous membrane

  • forms flat bones and cranial bones

endochondral ossification

• replaces bone

  • cartilage bone forms by replacing hyaline cartilage

  • forms most of the skeleton

• cartilage is there FIRST—it is then broken down and bone forms

• forms ALL bones bnelow skull except for clavicles

• “build a temporary cartilage model, then replace it”

ossification centers appear in fibrous membrane…

produces connective tissue

osteoblasts secrete osteoid, which calcifies…

hardens—calcification of osteoid tissue and entrapment of osteocytes

interstital growth

length of long bones — epiphyseal plate

zones:

1. proliferation zone

2. hypertrophic zone

3. calcification zone

4. ossification zone

appositional growth

thickness and remodeling of all bones by osteoblasts and osteoblasts on bone surfaces

• bone matrix secreted under periosteum

proliferation zone

chondroblasts quickly divide and push the epiphysis away from the diaphysis—lengthening the bone

hypertrophic zone

older chondrocytes enlarge and signal the surrounding matrix to calcify

calcification zone

matrix becomes calcified; chondrocytes die

ossification zone

osteoclasts digest calcified cartilage

osteoblasts replace actual bone tissue—resullting in bone trabeculae (spongy bone)

bone growth

& bone remodelng

growth hormone

stimulates epiphyseal plate activity from the pituitary gland

thyroid hormone

modulates activity of growth hormone

testosterone and estrogens

@ puberty

• promotes adolscent growth spurts

• end growth by inducing epiphyseal plate closure (18 yr females; 21 yr males)

calcium and phosphate regulation

• intestines: calcium and phosphate ions are absorbed from the diet

• skeleton; osteoblasts are depositing new bone at the same time osteoclast release existing calcium and phosphate ions that enter the circulation—the balance between osteoblast and clasts is hormonally regulated

• kidneys: levels of calcium and phosphate lost in the urine is hormonally regulated

parathyroid hormone (PTH)

blood Ca2+ levels → parathyroid glands release PTH → PTH stimulates osteoclasts to degrade bone matrix and release Ca2+ → blood Ca2+ levels

wolffs law

living bone continuously adapts and remodels itsself in response to the mechanical loads and physical stress placed upon it

fracture classification

• displaced or non-displaced

• open or closed

• comminuted — bone fragments

• spiral — excessive twisting force

• compression — common in osteoporosis

• depressed

• greenstick

traverse

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linear

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oblique nondisplaced

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oblique displaced

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spiral

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greenstick

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comminuted

.

stages of healing a bone fracture

1. hematoma

2. fibrocartilaginous callus

3. bony callus formation

4. bone remodeling

hemtatoma forms

mass of clotted blood forms

• site becomes swollen, painful and inflamed

fibrocartilaginous callus (soft callus)

fibroblasts secrete collagen to connect bone ends

osteoblasts begin forming spongy bone in 1 week

bony callus formation (hard callus)

osteoblasts create a bony collarto unite broken ends firm union in 6-8 weeks to heal

bone remodeling

response to mechanical stresses, fragments removed by osteoclasts, osteoblasts lay down spongy bone and then converted to compact

osteoporosis/osteopenia

loss of bone mass—bone resoprtion outspaces

• treatments center around drugs that stimulate bone deposition or slow rate or resportion