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1

3 TYPES

  • SMOOTH - visceral, many body organs and blood vessels
  • SKELETAL - voluntary, mainly attached to bony skeleton - striated
  • CARDIAC - only at heart, branching/striated

OTHER CONTRACTILES

  1. PERICYTES (along some blood vessels)
  2. MYOFIBROBLASTS (scar formation
  3. MYOEPITHELIAL CELLS (milk @ lactate

2

SMOOTH MUSCLE

  • discrete cells with cell junctions - function as whole
  • LONGITDUINAL - FUSIFORM w/ cylindrical nuclei
  • TRANSVERSE - ROUND cell and nuclei
  • CENTRAL NUCLEUS / NO STRIATIONS

not organised into sarcomeres

  • anchored to cell membrane in clumps
  • reticulin (collagen T3) rich external lamina / BM that joins cells together
  • electrically coupled via gap junctions
  • surface receptors for hormonal stimuli

this slide- double layer of smooth muscle @ intestines

3

SMOOTH MUSCLE ARRANGEMENT AND GAP JUNCTIONS

  • each junction = 6 CONNEXON PROTEINS span cell membrane and link interior of adjacent cells
  • vital for co-ordinated contraction
  • guarded central pore - small molecules to pass from one cell to the next (signal molecules) electrical coupling - freely and quicker than transporting

4

SKELETAL MUSCLE TERMINOLOGY

  • sarcomere - regular repeat structure within myofibrils = interdigitated actin and myosin
  • myofibril - small intracellular fibril - sarcomeres joined end to end
  • muscle fibre - fusion of many myocytes with 100s of myofibrils. surrounded by common plasmalemma, behaves as single cell - many nuclei
  • fasciculus - bundle of muscle fibres surrounded by connective tissue
  • endomyosium - lace work of connective tissue between muscle fibres
  • perimysium - surrounds group of fibres to form fasciculus
  • epimysium - connective tissue around fasciuli to form muscles

5

MUSCLE FIBRE & LONGITUTIDNAL SKELETAL MUSCLE

  • long unbranched
  • many nuclei
  • LONGITUDINALLY - nuclei at fibre edges
  • TRANSVERSELY - aggregated to fasciuli, nuclei at edges

this slide - tongue (with longitudinal muscle fibres)

EXTRINSIC FIBRES - poke out motuh

INTRINSIC FIBRES - manipulate food

myofibrils in register = striations

6

SKELETAL MUSCLE (TRANSVERSE)

  • loosely aggregated to fasciuli by PERIMYSIUM
  • nuclei at periphery of fibre

SKELETAL MUSCLE INDIVIDUALLY INNERVATED IN MOTOR UNITS

MITOCHONDRIA BETWEEN MUSCLE FIBRILS WITH MUSCLE FIBRES

MAY SEE GLYCOGEN AND LIPID DROPLETS

7

SARCOMERE (IRON HAEMATOXYLIN)

  • unit structure of sacromere
  • Z line to Z line
  • thin actin to Z line
  • interdigitate thick myosin
  • in contraction shortens up to 1/3
  • I band - actin only
  • A band - actin and myosin
  • H band - myosin only (with M line)
  • myofibrils run in parallel with sarcomeres in register = STRIATIONS

SARCOMERES JOINED END TO END AND SIDE TO SIDE AT Z-LINE

8

CARDIAC MUSCLE

  • discrete rectangular cells - end to end
  • central nuclei
  • branch
  • connected by intercalated discs - hold cells physically and electrically coupled
    1. desomosomes
    2. adherent junctions
    3. gap junctions
  • sarcomes i.e. STRIATED with myofibrils but with different protein isoforms to skeletal
  • many mitochondria (ox phos dependent) therefore aerobic respiration only

don't necessarily have own nerve supply as have innate contractility (SA and AV node regulated)

9

SARCOMERES

  • when stimulated actin fibres slide within th A-band
  • brings Z-lines close together
  • shortens sarcomere up to 30% - extrinsic work
  • tension increases - intrinsic work
  • structural protein  - titin

between myofibrils:

T-tubules - conduct impulse

sarcoplasmic reticulum - sequester calcium

glycogen/lipid storage

mitochondria - ATP production

UPPER FIBIRL - contractile

LOWER FIBRIL - structural

 

10

SKELETAL MUSCLE LONGITUDINAL

  • each skeletal muscle fibre = hundreds of myoblasts fused to syncitium
  • each fibre = many nuclei under plasmalemma at side of fibre - DISTINGUISHING POINT

this slide -tongue

n.b. small fascicles usuall denote smaller motor units = fine control

11

SKELETAL MUSCLE TRANSVERSE

  • polygonal pink fibres
  • arranged in clumps = fascicles

not all skeletal muscle is attached to bone

when skeletal muscles are attached together by fibrous connective tissue = RAPHE

12

SKELETAL MUSCLE BANDING (IRON HAEMATOXYLIN)

  • I band - pale, predominantly actin
  • Z line -  @ centre of I band
  • A band - darker staining, MYOSIN RICH

A band is not actin

@ centre of each A band = paler H band with M line

I stands for ISOTROPIC

A stands for ANISOTROPIC

13

FIBRE ARRANGEMENT LONGITDUINAL

  • striations (myofibrils and repeat sarcolemmas)
  • Dark = A band
  • Light = I band
  • Z lines connected

IN REGISTER

between myofibrils = mitochondria and elements of sarcoplamic reticulum 

DYSTROPHIN - binds actin to plasmalemma of muscle cells - structural integrity

14

FIBRE ARRANGEMENT TRANSVERSE

  • actin and myosin appear as dots
  • @ I band = small dots only (light)
  • @ A band = small and large dots - actin and myosin (dark)

between myofibrils may see parts of T-tubules and sarcoplasmic reticulum. also glycogen and mitochondria.

Z DISC COMPOSITION

lipid = 60% - electrostatically binds proteins

major protein = ALPHA ACTININ

15

SKELETAL MUSCLE: TYPE 1 & 2(a/b)

most fibres contain all 3 but proportions vary

  1. TYPE 1 - SLOW TWITCH: oxidative / fatigue-resistant / postural muscles
  2. TYPE 2a - FAST TWITCH: oxidative / glycolytic - moderately fatigue resistant
  3. TYPE 2b - FAST TWITCH: depend on glycolytic processes and are therefore fatigue sensitive (SPRINT MUSCLES)

this slide - stained for fibrillar ATPase (DARK BROWN) and greatest in slow twitch with greater number of mitochondria

postural muscles at spine have largest proportion of slow twitch

fingers have highest proportion of fast twitch

16

SKELETAL MUSCLE: TYPE 1

  • type 1 - rows of mitochondria between myofibrils
  • fat globules alongside mitochondria used for ATP production

17

SKELETAL MUSCLE: TYPE 2

  • type 2 - fewer/smaller mitochondria
  • large reserves of carbohydrates/glycogen

running = anaerobic, therefore uses carbs as energy source

18

SHARPEY'S FIBRES - TYPE 1 COLLAGEN

  • muscles connected to bones via CONNECTIVE TISSUE (MYSIUM)
  • either as
    1. small collagen bundles (SHARPEY'S FIBRES)
    2. discrete tendons
  • Sharpey's merge with fibrous periosteum of bone and collagenous bone matrix
  • spreads muscle force over wide area e.g. rotator cuff at scapular

this slide - oblique = sharpey's / below = periosteum of bone / lower pale staining cellular layer / upper darker staining fibrous layer

19

TENDON -TYPE 1 COLLAGEN

  • tendons and aponeuroses = condensed parallel bundles of collagen fibres interspersed with fibroblasts
  • at end of muscle fasciculi split becoming smaller but more numerous
  • connective tissue between more numerous

TENDON = continuation of peri/epimycium

tearing a tendon causes inflammation

inflammation stimulates fibroblasts to synthesise actin (draws would together) and collagen

20

MUSCLE SPINDLE

  • sensory
  • embedded within muscle
  • small number intrafusal
  • surrounding msucle = extrafusal
  • separated by connective tissue sheath

intrafusal fibres:

  1. nerve fibres wound round
  2. parallel with extrafusal fibres
  3. relay information about contraction of surrounding muscle

fine movement= smaller motor units and more spindles

21

CARTILAGE

  • cartilage/bone = rigid conenctive tissue (CLOSELY RELATED)
  • undifferentiated mesenchymal cell
  • cells in dense GAG rich matrix
  • variable amounts of collagen and elastic tissue
  • FLEXIBLE/COMPRESSIBLE/HARD WEARING

22

CARTILAGE 2

  • surrounded by fibrous capsule - collagen perichondrium
  • perichondrium contains undifferentiated progenitor cells (to chondroblast if needed))

3 FORMS

  1. HYALINE (T2 collagen) - fine collagen and elastic fibres - glassy. POOR STAIN WITH H&E - eg. articular surfaces. all long bones originally H&E
  2. ELASTIC (T2 collagen and elastic) - irregular arranged elastic fibres VISIBLE
  3. FIBROUS (T1&2 collagen) - banded collagen eg. intervertebral discs

 

23

HYALINE CARTILAGE

  • GAG rich
  • invisible collagen/elastic - glassy
  • clumped chondrocytes in matrix (pale staining lacunae)
  • MATRIX BINDS WATER - when compressed exudes water (reabsorbed when pressure released

this slide - trachea

n.b. 

  1. ARTICULAR CARTILAGE has no perichondrium
  2. hyaline receives nutrients via diffusion from surrounding tissue

24

ELASTIC CARTILAGE

  • larger amounts of elastin
  • PINK STAINING STRANDS
  • may be fractured (though tougher than hyaline/fibrous

this slide - epiglottis

25

FIBROUS CARTILAGE

  • large amount of collagen arranged in sheets

this slide - IV disc

  1. thick fibrous outer shell
  2. more fluid centre
  3. condrocytes distributed throughout both
  4. chondrocytes between collagen laminae

OUTER CASING - annulus fibrosus

INNER CASING - annulu pulposus

26

BONE - T1 CARTILAGE

  • mainly collagen (95%) - becomes mineralised (5%)
  • synthesised by osteoblasts
  • osteoblasts secrete collagen rich matrix - osteoid
  • mineralised with hydoxyapetite
  • cells trapped in bone -> less active osteocytes
  • BONE REABSORBING CELLS - osteoclast (multinucleate/phagocytotic
  • bone dynamic - actively resorb bone - continous remodelling

PRIMARY BONE

  • randomly organised (woven)
  • collagen fibrils - multidirectional
  • poor weight/strength ratio
  • soon replaced by more organised secondary bone

27

BONE 2

SECONDARY BONE

  • organised 
  • layers - long axis of hydroxyapetite crystals in parallel with collagen
  • collagen fibres at right angles layer to layer - plywood 
  • INTERNALLY = OSTEONS
  • osteons = cylindrical units w/ concentric layers bone and HAVERSIAN CANAL
  • HC contains blood vessels and nerves to osteocytes in bone
  • osteons continually eroded and replaced
  • between osteons = interstitial bone (remnants of previous osteon)
  • surrounded by fibrous capsule (periosteum) w/ progenitor cells = healing
  • open framework/compact lamellae or osteons

28

MINERALISED BONE - GROUND SLIDE

  • too tough to cut thin
  • golden brown haversian canal
  • average diameter = 200 microns
  • cement line separates each osteon - seals from neighbours - so oxygen/nutrients from HC diffuse throughout osteon
  • stops osteocyte contact intra osteon

29

OSTEOCYTES IN IMPREGNATE BONE

  • impregnate with dye
  • reveals osteocytes and fine processes (filopodia)  through bone
  • filopodia make contact with adjactent cells
  • passage of nutriets/oxygen etc
  • respond to hormones and break down or deposit bone to regulate calcium levels

30

DECALCIFIED BONE

  • dissolve mineral with H2SO4 or EDTA
  • mostly condensed collagen left
  • HC size increases as bone reabsorbed from osteon
  • narrower as new bone deposited
  • before puberty