WK 4 Musculoskeletal system

Bones function

Our skeleton is living, dynamic, complex organs that grow + renew + repair

Func: Support movement and scaffolding to hang muscles but also apart of maintaining homeostasis

Bone composition

Connective tissue with lots of background matric (osseous tissue) surrounding widely separated cells

• Crystalised minerals, salts, collagen, water

Properties of the bone

Crystallised salts + collagen fibres → rigidity of bone → resists compressions forces

• Collagen fibres: flexibility

• Tensile strength: bend out of way under compression forces

Bone classification

Shape: Flat, long, sesamoid, short, irregular

Structure: Compact vs. spongy bone, Organic vs. inorganic components

Organic bones

Give flex and tensile strength → ability to resist tearing, stretching and twisting

Inorganic bones

Gives hardness, rigidity and ability to resist compression forces and support body tissues

Long bone anatomy

• Diaphysis - bone shaft of compact bone

• Metaphysis - joins diaphysis and epiphysis

• Red marrow - in spongy bone

• Yellow marrow - lipid storage

• Articular cartilage - protects bone ends

Periosteum + Endosteum

• Peri - outside bone, nerve and blood vessels go through bone = lubricates cartilage, supplies oxygen, rich supply of blood vessels

• Endo - contain bone cells (Osteo)

Osteogenic

(Stem cells)

Produce osteoblasts, build bone both organic and inorganic = surrounded by matrix

Osteoclasts

Secrete acids and enzymes to break down/reabsorb bone = maintain homeostasis with in out blood

Osteocytes

Maintain matrix and mineral content

Spongy vs. Compact bone

Combo of spongy and compact =

• Support, strength, protection, light weight

• Ideal for weight bearing (spongy and compact)

• Ideal to resist compression (compact)

• Ideal to resist forces applied from different angels (spongy)

Joint structure

Any place where adjacent bone/s and cartilage come together (articulate with each other) = form connection

• It is presence or absence of a space/cavity between articulating bones and types of CT

Joint function

How much movement is permitted at the joint

• Depends on degree of movement

Cartilage joints

• No joint cavity

• Bones connected by hyaline or fibrocartilage

synchondrosis - epiphysed plate..

symphysis - has pad of fibrocartilage between bones

Synovial joints

• joint cavities

• held together by articular joint/ capsule and ligaments

• Joint cavity contains synovial fluid

Circumduction

Circular movement if distal end of body part e.g. moving hand in circle at wrist point

Rotation

When body revolves around own longitudinal axis e.g. shake head ‘no’

Muscles mean

Without smooth muscles we could not move fluids, solids along digestive tract

= without muscle tissue no movement would occur in the body

• produce movements

• Stabilise body positions

• Support soft tissue

• Storing substances within the body

Muscle tissue types

1. Smooth

2. Cardiac

3. Skeletal

   = ALL highly specialised to CONTRACT

Smooth muscle

Loc. Walls of hollow internal structure

• blood vessels change diameter

• Stomach, intestines, bladder, uterus, airway → lungs

• Involuntary control

  • spontaneous rhythmic cycles (pace setter cells)

  • Influenced by hormones, stretching, ANS

  • No tendons

Smooth Muscle histology

• Uni-uncleared

• Spindle shaped

• Non-striated

• Auto rhythmic

• Can divide and regenerate

Cardiac muscle

• only found in heart

• Involuntary control

• Pace maker cells

• Influenced by ANS

Cardiac histology

• uni-nucleated

• Striated

• Branched

• Intercalated discs

• Myoglobin stores

• Can’t divide or regenerate

Skeletal muscle

Most abundant muscle type

• voluntary control

• Controlled by nerves of the CNS

• Can be influenced by hormones

• Contraction = shortens muscle

• Relaxation = lengthens muscle

• Can only pull bone

Skeletal histology

• Very long

• Multi nucleated

• Cylindrical

• Striated

• Myoglobin stores O2

• Can’t divide CAN repair (stem cells)

Skeletal muscle organisation

Myofilaments→ myofibril → fibre → fascicle → muscle

Sarcolemma

Cell membrane surrounding muscle fibre

Sarcoplasm

Cytoplasm within muscle cells

Transverse tubules

Bit where cell membrane is pushed down into interior of cell

• filled with extra fluid

• Action potential runs outside cell and into myofibrils can contract

Sarcoplasmic reticulum

Highly specialised smooth

ER (endoplasmic reticulum) = strong, releasing, refrieving calcium ions

Myofibril structure

• Bundles of protein filaments (myofilamenrs)

  • actin

  • myosin

  • titin

• Responsible for muscle contraction

What triggers muscle contractions

Nervous signal

How to relax (after contraction)

How muscle contractions occur

Muscle tone

At an organ level never fully relaxed

• certain degree of contraction or undertone of contraction that occurs in muscles while at rest

• allows us to maintain posture

• Stabilises bones and joints

• Ready response state

Hypertrophy

Increased use

Increased use of tissue = increase size

Hyperplasia

Increase in tissue size - due to increase in number of cells e.g. smooth muscle

Atrophy

Decrease in use

decrease in tissue size

due to decrease in size of cells e.g. skeletal muscle