Musculoskeletal

• Haematoxylin


  Stains nucleus
• Eosin


  Stains cytoplasm
• White


  Stains mucous/fat
• Tolvidine bone


  Stains contractile apparatus of skeletal muscle and cardiac muscle
• Diaphysis of long bone

  • Periosteum lines bones
  • Medullary cavity - bone marrow - haematopoiesis
• Metaphysis of long bone

  • Trabecullar bone - less osteoid - lighter - structural ridges that run across central region - pale pink
  • Red bone marrow - hematopoietic - produces red blood cells
  • Yellow bone marrow - white
  • Bone marrow between trabeculae
• Growth rate of long bone

  1. Proliferating chondrocytes - increase in number

  2. Hypertrophic chondrocytes - increase in size

  3. Calcifying chondrocytes - calcified and replaced by bone - increase bone length
• Growth rate of long bone occurs in the epiphysis of bone in juveniles
• Cancellous/spongy/trabecular bone


  • Responsible for remodelling bone
  • Osteoblast - bone producing - secretes bone matrix (osteoid) on cell surface - increases density - mineralises due to deposition of calcium and phosphate
  • Osteoclast - bone destroying -secretes acid on bone surface to break bone matrix produced by osteoblast - decreases density
  • Osteoblast and osteocyte activity needs to be balanced
  • Osteocyte - surrounded by lacunae to determine bone strain and adjust bone formation vs bone reabsorption
• Bone remodelling


  1. Osteocyte in bone matrix connects to bone surface

  2. Detects strain on bone

  3. Signals to osteoblast and osteoclast

  4. Regulates bone production, absorption and remodelling process
• Bone reduction


  Calcium is released - muscle contraction - need more osteoclasts to break bone - negative effect on strength of skeleton
• Bone production


  • Strength increase
  • More osteoblasts to form bones
• Cartilage


  • Epiphysis of long bone
  • Articular - smooth to create gliding surface - hyaline cartilage - chondrocytes are sat in lacunae - become flattened as they reach articular surface
• Striated skeletal muscle


  • Elongated and branched cylindrical cells - below sarcolemma - double layered membrane - sarcoplasm - sarcoplasmic reticulum - stores/releases calcium ions
  • Multinucleated - produces lots of proteins and enzymes for contraction
  • Attaches to skeleton to support locomotion
  • Epimysium - connective tissue surrounding whole muscle - contraction
  • Perimysium - connective tissue surrounding bundle of muscle cells
  • Endomysium - connective tissue surrounding individual muscle cells - collagen and reticular fibres, containing extracellular fluid
  • Collagen in mysia intertwines with collagen of tendon
  • Tension created by muscle contraction transferred to mysia to tendon then to periosteum to pull bone
  • T tubules conduct charge
  • Peripheral nuclei
  • Blood supply - capillaries
  • A band - thick filament - actin
  • I band - thin filament - myosin
  • Z line - boundary of each sarcomere
  • Long cylindrical fibre
  • Voluntary movement
  • Produces heat
  • Protects organs
  • Forelimb - thorax and neck
  • Hindlimb - abdomen
• Muscle arrangement


  • Parallel
  • Convergent
  • Pennate
  • Circular
• Muscle contraction


  1. Signal form cerebellum sends action potential to muscle fibre at nueromsuclar junction - becomes chemical (acetylcholine) and diffuses across synaptic cleft and binds to acetylcholine receptors on muscle fibre - influx of ions - then electrical via sarcoplasmic reticulum - opens junction

  2. Sodium enters myofibrils to depolarise cell - voltage gated calcium channels open - calcium contracts sarcomere - calcium absorbed into sarcoplasmic reticulum and stored until activation

  3. Excitation-contraction coupling needs more action potential

  4. I band shrinks

  5. Myosinfilaments with actin binding head binds to actin molecule

  6. Pulls itself forward - head binds again

  7. Binding of actin to troponin (actin-myosin complex)

  8. Bound together

  9. Contraction moves head forward

  10. Reduction in I band

  11. Contraction
• Excitation-coupling


  1. Acetylcholine released from axon terminal binds to receptors on sarcolemma

  2. Action potential is generated and travels down T tubule

  3. Calcium is released from sarcoplasmic reticulum in response to change in voltage

  4. Calcium binds troponin - crossbridges form between actin and myosin

  5. Acetylcholinesterase removes acetylcholine from synaptic cleft

  6. Calcium transported back into sarcoplasmic reticulum

  7. Tropomyosin binds active sites on actin causing cross bridge to detach
• Excitation-couping - cross bridge cycling


  1. Active site on actin exposed as calcium binds to troponoin

  2. Myosin head forms cross bridge with actin

  3. Power stroke - myosin head bends and ADP and phosphate is released

  4. ATP attaches to myosin head - cross bridge detaches

  5. ATP hydrolyses to ADP and phosphate - returns myosin to potion
• Creatine phosphate metabolism


  1. ATP + creatine = creatine phosphate and ADP = creatine kinase = creatine and ATP

  2. Active muscle - need ATP - creatine kinase breaks down

  3. Resting muscle - don't need ATP - creatine kinase is all that's needed
• Anaerobic glycolysis


  1. Blood glucose (from food) + muscle glycogen = glucose = glycolysis (ATP X 2 and Pyruvate x2)

  2. No oxygen - lactic acid

  3. Oxygen - aerobic
• Aerobic respiration


  Blood glycose + pyruvic acid + fatty acids = cellular respiration = ATP + heat + CO2 + O2
• Muscle contraction - length tension relationship

  If sarcomere is stretched too far - cannot form crossbridges - filaments are too far away
• Frequency of stimulation


  1. Stimulus period - latent period - stimulus to muscle time

  2. Contractile period - maximum contraction

  3. Relaxation period - muscle relaxes

  4. Wave summation - keeps contracting

  5. Tetanus - permanent contraction

  6. Treppe - first contraction after resting

  7. Spasicity - uncontrolled contraction

  8. Rigidity - contract and don't relax

  9. Rigidity cogwheel - resistant to movement - moves like a clock
• Tendon


  • Dense regular connective tissue
  • Crimps elongate under extension
  • Connects muscle to bone - force by muscle conveyed to bone
  • Storage of elastic energy - reduces muscular effort for locomotion
  • Elastic energy is increased to increase effect
  • Tenocytes - synthesise extracellular matrix of tendons
  • Blood supply
  • Collagen
• Concentric contraction


  Tendon doesn't move - muscle reduces length, increases diameter - causes joint movement
• Eccentric contraction


  Tendon doesn't move - muscle stretches - increases length, reduces diameter - controls joint movement
• Isometric contraction


  Tendon stretches - muscle reduces in length, increases diameter - no joint movement
• Ligament


  • Rod like nuclei
  • Even spread of nuclei and fibre width and direction
  • Attach bone to bone
  • Dense regular connective tissue
• Connective tissue


  • Synovial membrane - excrete fluid into synovial joint
  • Renal capsule - fibrotic membrane surrounding kidney
  • Haptic/Glissons capsule - collagen membrane surrounding liver
  • Meninges - brain, spinal cord
  • Secretes by fibroblasts
• Loose connective tissue (proper)

  • Areolar - gaps between fibres - basal membrane - water storage - dense collagen fibres - between epidermis and dermis - prevents friction - flexibility and elasticity
• Adipose


  • Loose connective - energy preserve - lipid rich - adipocytes
• Reticular


  • Branched - reticulin fibres - create and maintain fine networks of fibres for lymphoid organs - create stroma
• Dense connective tissue (proper)

  • Regular elastic - elastin and collagen fibres - fibroblasts - parallel to tendons and ligaments - tensile strength and resistant to stretch
  • Irregular elastic - dermis, joint capsules and muscle fasciae - multidirectional - prevent tearing
  • Tendon
  • Ligament
• Supportive connective tissue


  • Mineralised
• Cartilage


  • Chondrocytes are in lacunae
  • Hyaline - chondrocytes and extracellular matrix - movement of joints, flexible, transmission of loads without friction
  • Fibrocartilage - hyaline and cartilage - insertions of tendons and ligaments - chondrocytes and fibroblasts - cushion joints, shock absorption
  • Elastic - elastic fibres and collagen - surrounded by mantle of fibrillin - supports soft tissues with low stiffness - energy storage and resistance
• Bones


  • Compact bone - osteons formed by lamellae around central canal containing blood vessels and nerve fibres - protection and strength of bones
  • Cancellous bone - surrounded by compact - large pores - in medullar cavity - strength and rigidity
• Fluid connective tissue


  • Blood - plasma, erythrocytes, leukocytes, platelets - blood clotting, transport and regulation
  • Lymph - interposed lymph nodes, reticular fibres and fixed cells - macrophages and reticular cells, lymphocytes, plasma cells, granulocytes - immunity, waste and excess fluid removal
• Tissue origin


  1. Zygote - divides into 8 cells

  2. Morula

  3. 4th day - blastula

  4. Gastrula with blastopore

  5. Late gastrula - endoderm forms and mouth and digestive tract forms
• Germ layers


  • Ectoderm - epidermis, glands on skin, pituitary and adrenal medulla, neurons, pigment cell, mouth, anus
  • Mesoderm - connective tissue proper, bone, cartilage, blood, endothelium of blood vessels, muscle, kidneys
  • Endoderm - lines airways and digestive tract and glands
• Epithelial membranes


  • Mucous membrane - digestive, respiratory, excretory and reproductive
  • Serous membrane - pleura, peritoneum