BMET2960 Notes PDF

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BMET2960 ANATOMY AND PHYSIOLOGY SKELETAL SYSTEM – BONES AND BONE TISSUE      

Understand the structure and functions of the skeleton Understand the composition of bone Understand the role of the cells osteoclasts, osteoblasts and osteocytes in maintaining the function of bone and how they interact to regulated bone modelling and remodelling Understand how bone acts as a store of calcium and how access to this store is regulated Be able to describe how bone forms and is repaired after fracture Understand how nutrition and ageing impact bone quality

SKELETAL DIAGRAM

FUNCTIONS OF A SKELTAL SYSTEM (*SAMPS*) Support: bones are hard and rigid; cartilage is flexible yet strong. Cartilage in nose, external ear, thoracic cage and trachea. Ligaments - bone to bone. Protection: Skull around brain; ribs, sternum, vertebrae protect organs of thoracic cavity Movement: Produced by muscles on bones, via tendons. Ligaments allow some movement between bones but prevent excessive movement Absorb shock: Impacts during motion need to be absorbed to reduce strain on bone and joints and damage to soft tissues. Storage: Calcium and Phosphorus. Stored then released as needed. Fat stored in marrow cavities. Blood cell production: provide niche for bone marrow to produce blood cells and platelets

STRUCTURE OF LONG BONE Diaphysis:

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Shaft(tube) or central part of long bone. Tube shape created by compact bone (denser material used to create much of the hard structure of the skeleton)

Epiphysis:

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End of the bone (round) Initially grows separately then fuses with the main bone through ossification Cancellous bone: spongy honeycomb structure

Epiphyseal plate:

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location of bone growth in the long bones of the body made of hyaline cartilage present until growth stops

Epiphyseal line:

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line at the end of long bones that is found in adults. The epiphyseal line replaces the epiphyseal plate

Medullary cavity:

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central cavity of bone shafts where red bone marrow and/or yellow bone marrow (older replaced by fat cells) (adipose tissue) is stored;

CANCELLOUS/ SPONGY/ TRABECULAR BONE

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Open cell porous network. Trabeculae: Interconnecting rods or plates of bone. Like scaffolding.  Spaces filled with marrow.  Covered with endosteum. (outer semi circles - soft, connective tissue, lining the cavity of long bones)  Oriented along stress lines

COMPACT/CORTICAL BONE

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Bone is a cellular and vascular structure continually being renewed and repaired. Dense outer surface of bone that forms a protective layer around the internal cavity Central canals – blood vessels profuse out of these canals to provide nutrients to the bone. (runs parallel to long axis) Lamellae: thin plate-like structure – concentric circles - provides protection and strength to bones.  Concentric: surround central canals  Circumferential lamellae on the periphery of a bone  Interstitial lamellae- between osteons (remnants of osteons that were partially resorbed) Osteon or Haversian system: consisting of concentric bone layers called lamellae, which surround a long hollow passageway, the Haversian canal. The Haversian canal contains small blood vessels responsible for the blood supply to osteocytes (individual bone cells) lacunae (gaps in the osteons) and canaliculi (microscopic canals) contain osteocytes and fluid Perforating / Volkmann’s canal: Perpendicular to long axis. Both perforating and central canals contain blood vessels. Direct flow of nutrients and signals from vessels through cell processes of osteocytes and from one cell to the next.

BONE COMPOSITION (COLLAGEN-MINERAL COMPOSITE)

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Composite material with two phases  Organic: collagen type I, proteoglycans and other proteins  Inorganic: hydroxyapatite like mineral phase. CaPO4 crystals with frequent substitutions of carbonate and other anions and cations; more accurately called carbonate apatite No minerals – bone is too bendable No collagen – too brittle Collagen protein Type 1: triple helix structure ( 2 alpha-1 and 1 alpha-2 strands). Interowven helix structure. Gaps between protein molecules have mineral plates between the collagen fibrils which give the pbine its strength. Alternating thick and thin collagen sheets with mineral plates are laid in a plywood like structure.

WOVEN AND LAMELLAR BONE Woven bone: characterized by haphazard organization of collagen fibers and is mechanically weak. Formed during fetal development and fractures repair Lamellar bone: secondary bone created by remodelling of woven bone. Contains sheets of lamellae. Fibers are oriented in one direction in each layer, but in different directions in different layers for strength. Woven bone has more osteocytes per unit of volume and higher rate of turnover.

BONE CELLS OSTEOCLASTS: -

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Make and secrete digestive enzymes that break up or dissolve the bone tissue. Dissolve and free the calcium and minerals. Used when a bone is old, needs to be remodelled. Sealing zone: donut shaped seal to create a pocket against the bone surface Ruffled border: cell membrane borders bone where resorption takes place H+ ions are pumped across membrane- acid formed demineralises bone. Release enzymes that digests bone protein matrix Arise from fusion of bone-eating cells (multinucleate)

OSTEOBLASTS: Work together in groups called osteons to make the osteoid matrix (composed of collagen protein and minerals made by Endoplasmic Reticulum and Golgi Apparatus) and release it at regulated times to form new bone tissue where it is needed most .

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Can release in a disorganised and rapid manner to make woven bone. Can form lamellar bone through ossification. Highly ordered secretion of protein Can imbed inside the bone and become surrounded by matrix; differentiating into osteocyte.

OSTEOCYTES:

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Mature bone cells sense bone strain and damage. Involved in bone remodelling by transmitting signals to other osteocytes in response to even slight deformations of bone caused by muscular activity. Lacuna: spaces occupied by cell body Canaliculi: microscopic canals that can attach to other osteocytes and bone surfaces Nutrients diffuse and are filled into the lacuna and canaliculi Detect sense of bone damage – by monitoring canicular fluid flow network – the fluid flows between osteocytes when there is bone stress. The osteocytes then signal to the bone surface to induce bone resorption or formation.

STEM CELLS -

Osteoblasts are derived from mesenchymal stem cells (source of bone cells)- can also turn into connective tissues cells (adipocytes, chondroblasts). Marrow stromal Osteoclasts are derived from haematopoietic stem cells – first become monocytes.

BONE REMODELLING – CANCELLOUS BONE -

Old bone removed by osteoclasts, move across bone surface forming a pit. The old bone is replaced with new bone by osteoblasts which fill the pit

BONE REMODELLING – CORTICAL BONE -

Osteoclasts form a cutting cone and tunnel through the bone forming a tunnel. Blood vessels advance with the osteoclasts. Osteoblasts then form and lay concentric layers of bone matrix until the tunnel is almost completely filled.This gives rise to Haversian systems seen in cross section as circular structures surrounding blood vessels with bone formed in concentric lamellae Osteoblasts balance many stimuli to regulate both bone resorption and formation (hormones signal osteoblasts to create more RANKlL which stimulate osteoclasts to eat bone and release nutrients (calcium).

CALCIUM HOMEOSTASIS Homeostasis: this dynamic state of equilibrium is the condition of optimal functioning for the organism The level of calcium in the blood depends on movement of calcium in and out of the bone

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Calcium enters bone when osteoblasts create new bone Calcium leaves when osteoclasts eat bone Two hormones control blood-calcium levels (parathyroid hormone and calcitonin) Osteoblasts activates RANK Ligand which signals osteoclasts to eat away bone (resorption) Osteoblasts produces OPG which binds to RANK and reduces signals to osteoclasts resorption is REDUCED. Bone strain produces bone resorption of bone under tension and bone formation where bone is under compression to change shape.

BONE DEVELOPMENT

Intramembranous ossification: -

takes place in tissue connective membrane forms skull bones, part of mandible, clavicle, diaphysis Centres of ossification: locations in membrane where ossification begins Fontanels: large membrane covered spaces between developing skull bones; unossified

Endochondral (long bones) ossification: takes place via a cartilage intermediate template -

Bones of the base of the skull, part of the mandible, epiphyses of the clavicles, and most of remaining bones of skeletal system. Cartilage formation begins at 4 weeks after development Ossification starts week 8 – ends in 18-20 years Both produce woven tissue then remodelled into lamellar bone Both processes lead to same result after remodelling.

BONE GROWTH -

The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis. The chondrocytes, in the region next to the diaphysis, age and degenerate. Osteoblasts move in and ossify the matrix to form bone. This process continues throughout childhood and the adolescent years until the cartilage growth slows and finally stops

Factors affecting bone growth -

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Normally genetically but can be influenced by nutrition and hormones Lack of Ca – small bones Vitamin D – necessary for absoroption from intestines  Sunlight  Rickets: lack of Vit D from childhood  Osteomalacia: lack of vitamin D during adulthood  Both can cause soft bones due to lack of mineralisation Vitamin C  Necessary for collagen synthesis by osteoblasts  Scurvy: deficiency of vitamin C  Lack of vitamin C also causes wounds not to heal, teeth to fall out Hormones Growth hormone from anterior pituitary. Stimulates interstitial cartilage growth and appositional bone growth Thyroid hormone required for growth of all tissues Sex hormones such as estrogen and testosterone o Cause growth at puberty, but also cause closure of the epiphyseal plates and the cessation of growth

BONE REPAIR

BONE FRACTURES -

Open (compound): bone break with open wound. Bone may stick out Closed (simple): Skin not perforated Incomplete: does not extend across the bone Complete: it does extend Hairline: incomplete – two sections do not separate – skull fracturs Comminuted: complete break in two or more places Impact: one fragment is driven into the cancellous portion of the other fragment. Critical sized defect: Gap too large to be filled by natural repair leads to non union if untreated

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WEEK 2 – JOINTS OUTCOMES -

Contrast the major categories of joints and explain relo between structure and function Describe basic structure of synovial joint – common synovial joint accessory structures and their functions Describe how the anatomical and functional properties of synovial joints permit the movements of the skeleton. Describe the articulations between the vertebrae of the vertebral column.

Articulations: -

Joints or (articulations) – where two bones connect for the purpose of movement. Determines direction and distance of movement (ROM) Joint strength decreases – mobility increases (shoulder joint is the most flexible – easily injured joint)

CLASSIFICATION Structural: -

Bony (rigid, immovable) Fibrous (gum and teeth, between skull bones) Cartilaginous (resilient, flexible) Synovial (low friction) Need to know the classifications – do not go in depth on the examples

SYNOVIAL JOINT Cartilage: resilient and smooth elastic tissue (padding between bones) -

Synovial cartilage pad surfaces within articular capsules  Prevent bone on bone touching Smooth surfaces lubricated by synovial fluid  Reduce friction

STRUCTURE OF ARTICULAR/JOINT CARTILAGE -

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Red cartilage with proteoglycans – sugar rich hydrophilic gel like substance  Collagen molecules in multiple directions to give strength in all planes – helps bounce back from pressure and stress on bone Contain chondrocytes which maintain health of cartilage Smooth surface at the top›

SYNOVIAL FLUID -

Contains slippery proteoglycans secreted by fibroblasts

Functions -

Lubrication (Lack of friction free motion) Nutrient Shock absorption

Cartilage relies on synovial fluid for a major source of nutrients. No blood supply in cartilage therefore no stem cells for cartilage repair.

SYNOVIAL JOINT ACCESORY STRCUTURE Cartilage  

Cushions the joint against pressure from one bone to another Fibrocartilage pad called a meniscus (articular disc) – limits movement

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protect cartilage superficial to joint capsule

Fat pads

Ligaments : around edges of the joint – limit ROM to prevent dislocation

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Support and strengthen joints Sprain – ligaments with torn collagen fibres

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attach muscle around joint – contract to provide movement and support

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bag of fibrous layer filled with synovial fluid– cushion where tendons and ligaments might rub against one another

Tendons

Bursae

FACTORS THAT STABALISE SYNOVIAL JOINTS -

Prevent injury by limiting ROM  collagen fibres in joint capsule, ligaments  articulating surfaces and menisci  other bones, muscles and fat pads  tendons

PROPERTIES OF SYNOVIAL ARTICULAR CARTILAGE -

highly resilient, low friction, viscoelastic fully functions for 60-70 years (1 million cycles/year for knee) very low friction due to 2 possible theories:  fluid lubrication- pressurised liquid film separates moving parts • studies show under diff speeds this theory is not valid  hydrostatic lubrication – pressing two joint layers of highly hydrating cartilage pressurises cartilage pore fluid – supports applied load. This leaves a small fraction to be supported by the solid matrix.

MOVEMENTS 3 types: -

linear movement (gliding): linear movement (pencil vertically moving on a paper) angular: pencil tip remains stationary both body moves around rotation: pencil tip stationary – body is at an angle moving conically to complete a circle

*movement in 1, 2 or 3 axes*

CLASSIFICATIONS OF SYNOVIAL JOINTS Gliding

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flattened or slightly curved non- axial motion – limited Eg: clavicle and intercarpal/tarsal joints

Hinge -

angular motion on single plane (monaxial) Elbow joint

Pivot -

Rotation only (monaxial) Wrist joint

Condylar -

Oval joint face with a depression Bi-axial Wrist

Saddle -

Two concave, straddled Biaxial Thumb

Ball and socket -

Round face in a depression – triaxial Shoulder joint

Mobile joints are supported by muscle and ligaments not bone to bone

INTERVERTEBRAL ARTICULATIONS -

C2 to L5 spinal vertebrae articulate:  At inferior and superior articular processes (gliding joint)  Between adjacent vertebral bodies (symphysial joints)

INTERVERTEBRAL DISCS -

Pads of fibrocartilage Separate vertebral bodies

Anulus fibrosus

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Tough outer layer- little expansion and contraction to push the nucleus gel back to central position Attaches disc to veterbrae

Nucleus pulposus -

Elastic gelatinous core Absorbs shocks by getting pushed out under pressure

Vertebral Joint -

Also called symphysial joints As it moves  Nucleus shifts  Disc conforms to motion

Intervertebral Ligaments -

Bind vertebrae together Stabilise column

Damage to Discs -

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Slipped Disc  Bulge in annulus fibrosus  Invades vertebral canal Herniated Disc  Nucleus breaks through annulus  Presses on cord and nerves

SHOULDER JOINT -

Glenohumeral joint Most ROM therefore least stable Supported by skeletal muscles, tendons, ligaments Ball and socket Between head of humerus and glenoid cavity of scapula

No need to memorise the parts

ELBOW JOINT -

Hinge joint Joints involving humerus, radius and ulna

SUPPORT -

Biceps brachii muscle and elbow ligaments

HIP JOINT -

Coaxial joint Ball and socket Wide ROM

Structure -

Head fits to fumr Socket of acetabulum Sheets of ligament to protect and stabilise

KNEE JOINT -

Hinge joint – femur to tibia

Medial and lateral menisci Fibrocartilage pads Femur-tibia joints Cushioning Lateral support Major Ligaments -

Anterior and posterior cruciate ligament (inside joint capsule

AGING Degenerative Changes -

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Rheumatism  Pain and stiffness in skeletal and muscular systems Arthritis  All forms of rheumatism that damage articular cartilage and synovial joints Osteoarthritis  Wear and tear of joint surfaces, or genetic affecting collagen formation  Over 60 years Rheumatoid Arthritis  Inflammatory condition – synovial inflamed leasing to joint destruction  Caused by body recognises joint as foreign material caused by infection, allergy or autoimmune diseases Gouty Arthritis  Occurs when crystals (uric acid or calcium salts) – form within synovial fluid due to metabolic disorders

Avascular necrosis – in the hip leads to collapses of subchondral bone – destroying joint (diver can get nitrogen bubbles forming in blood vessels blocking supply to hip joint)

CARTILAGE REPAIR -

Avascular – does not repair well Can induce a path to vascular subchondral (layer just sitting on cartilage) bone to allow stem cells for repair but will produce poor fibrocartilage which degrades overtime. (short term) Joint replacements – titanium joints  Increasing de1mands (65,000 replacements again after 1st time)  Inflammatory response due to particle wear (metal release) and stress shielding – bone loss therefore needs another replacement 

NERVOUS SYSTEM PART 2 Sensory Receptors Mechanoreceptors- bladder full of urine- sense stretching – signal is transalted into actions Chemo receptors: chemical conc – taste receptors Somatic Motor Pathways Motor neuron – one in the brain and axon going down into the

3 Identify the gross anatomical features of the human body 4 Describe the normal function of the major body systems (nervous, circulatory, respiratory, musculoskeletal, and renal) 5 Determine how these functions relate to cellular function

BMET2901 – MUSCLES -

Skeletal – biceps Cardiac Smooth

SKELETAL MUSCLE TISSUE Functions -

Produce skeletal movement Maintain posture and body position Support soft tissues Guard entrances and exits (mouths, anus)

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Maintain body temp (by shivering) Store nutrient reserves (glycogen – energy source)

Organisation of muscle -

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Muscle tissue (cells or fibres) Connective Tissues o Provides muscle attachments (muscle to bone matrix) o Tendon (bundle of connective) , aponeurosis (sheet) Blood vessels and nerves o Muscles have vascular systems to supply oxygen, nutri...