Musculoskeletal System 2 PDF

[email protected] @AnatomyCraig Musculoskeletal System 2 Musculoskeletal System Foundations in Bioscience II Dr Craig Johnson Intended Learning Outcomes Components and organisation of the skeletal system Classification of joint types Growth in the musculoskeletal system tissues Components...

[email protected] @AnatomyCraig Musculoskeletal System 2 Musculoskeletal System Foundations in Bioscience II Dr Craig Johnson Intended Learning Outcomes Components and organisation of the skeletal system Classification of joint types Growth in the musculoskeletal system tissues Components and organisation of the muscular system The effect of exercise on the musculoskeletal system How muscles contract and move the skeleton The effect of aging on the musculoskeletal system Hormones influencing the musculoskeletal system Growth in the musculoskeletal system Growth at the cellular level Hypertrophy ↑ Cell size No change in cell number Hyperplasia No change in cell size ↑ Cell number Longitudinal bone growth Bone growth starts as the formation of a bony collar around a cartilage template (2) Blood vessels invade the tissue (4) Osteoblasts enter the cartilage shaft lay down bone matrix (5) Osteoblasts enter the epiphysis and lay down bone matrix (7) Cartilage is retained between the epiphysis and the shaft (8 + 9) Types of Bone Growth INTERSTITIAL GROWTH Division of chondroblasts From within the cartilage APPOSITIONAL GROWTH Differentiation of cells from surface or perichondrium Bone Growth LONGITUDINAL Indirect growth via interstitial cartilage growth at the growth plate and ossification Ends at skeletal maturity CIRCUMFERENTIAL Occurs directly via appositional growth at the bone surface Continues throughout life http://www.imageinterpretation.co.uk/shoulder.php Epiphyseal Growth Plate Site of indirect bone growth via interstitial cartilage growth Increase in bone length complete at skeletal maturity when the growth plate “closes” and interstitial cartilage growth stops Trueman et al., 1996 Bone Formation Endochondral vs Intramembranous Within cartilage vs Inside a membrane “Plastic” bones and The Theseus Paradox Reorganisation of bone by resorption & deposition Modification of internal structure Very active in the young Less active (negligible) in adults unless due to trauma Increase in muscle mass In humans, result of hypertrophy rather than hyperplasia Achieved through upregulation of protein synthesis within muscle cells Skeletal Muscle Growth Hormonal control of the MSK system Growth Hormone (GH) GH Anterior Lobe of pituitary gland Liver Insulin like growth factor 1 (IGF-1) Bone & Cartilage Muscle Increased longitudinal growth Increased muscle mass Facilitated through 1) increased carbohydrate to amino acid conversion 2) Increased amino acid uptake, and 3) Increased protein synthesis Deficiency http://www.hormone.org/questions-and-answers/2011/growth-hormone-deficiency-in-children Excess Acromegaly http://medicalassessmentonline.com/terms.php?R=608 Gigantism vs Acromegaly Onset of excess GH Before closure of epiphysis After closure of epiphysis Tall stature Long extremities Delayed puberty Height unaffected Gonads unaffected Altered facial characteristics Gigantism Acromegaly Parathyroid Hormone (PTH) Regulates the distribution of calcium and phosphorus in the body PTH BONE BLOOD PLASMA Increased osteoclast activity Decreased osteoblast activity Ca Ca P P PARATHYROID GLAND Too much PTH? Too little PTH? Too little PTH = Decreased Ca in plasma Muscular rigidity Too much PTH = Increased Ca in plasma and loss of Ca from bone Increased chance of kidney stones and osteoporosis/osteopenia Muscular spasm Vitamin D Works with PTH to release calcium from the bone Stimulates absorption of Ca and P in the GI tract Vitamin D BONE Increased osteoclast activity Decreased osteoblast activity Ca P BLOOD PLASMA , rID: 20086 Adult deficiency Juvenile deficiency RICKETS OSTEOMALACIA Vitamin D Deficiency rID: 28734 Soft and weak bones often with curvatures and deformities Calcitonin Opposes PTH; Reduces the plasma calcium Calcitonin BONE BLOOD PLASMA Inhibited osteoclast activity Ca Ca Thyroid gland Vitamin C Essential for many enzymatic reactions Sourced from diet (e.g. bell peppers, kiwi fruit, broccoli, citrus fruit, etc) Involved in COLLAGEN SYNTHESIS Collagen is a vital component of muscle, bone, and cartilage DEFICIENCY = SCURVY (Adult) or BARLOW’S DISEASE (Juvenile) MSK symptoms: Bone and muscle pain Collagen is a major component of connective tissue and basement membranes Defective basement membranes can lead to bleeding Defective connective tissue can lead to ligament degradation Loss of teeth Joint aches Defective connective tissue can lead to bone damage Previously healed factures can recur New bone poorly formed Oestrogen Sex hormones produced by the gonads Responsible for sexual dimorphism Reduces bone resorption Stimulates bone development Reduces bone resorption Stimulates bone development Stimulates muscle mass increase Testosterone Osteoporosis http://www.moondragon.org http://drwolgin.com Osteoporosis and Oestrogen Oestrogen Osteoclast Osteoblast ↑ Apoptosis ↓ Bone resorption ↓ Apoptosis ↓ Oxidative Stress ↑ Maintain bone formation Bone maintenance Osteoporosis and Oestrogen Oestrogen Osteoclast Osteoblast ↑ Apoptosis ↓ Bone resorption ↓ Apoptosis ↓ Oxidative Stress ↑ Maintain bone formation Bone Loss Oophorectomy? Calcif Tissue Int (1988) 42:71-76 Calcitonin Parathyroid Hormone Reduces plasma calcium; Increases calcium in bone; opposes PTH Increases plasma calcium; Increases osteoclasts in bone; works with Vit D Growth Hormone Acts to increase bone and muscle growth Hormones & Vitamins influencing the MSK system Vitamin D Increases calcium resorption in GI tract; Increases osteoclasts in bone; Increases plasma calcium; works with PTH Oestrogen Testosterone Male sex hormone. Acts to increase bone and muscle mass Female sex hormone. Acts to reduce bone resorption and stimulate bone development Deficiency associated with osteoporosis Vitamin C Important in the production and function of collagen essential in muscle and bone function Deficiency associated with scurvy Performance enhancing drugs Some drugs are manufactured to mimic the effects of these hormones These increase muscle mass but also have a range of very dangerous side effects Performance enhancing drugs Erythropoietins (EPO) and agents affecting erythropoiesis Anabolic androgenic steroids (AAS) – Testosterone Peptide hormones and their releasing factors – (GH) Growth factors and growth factor modulators – (IGF-1, VEGF) Hormone and metabolic modulator – anti-oestrogens https://www.wada-ama.org/sites/default/files/resources/files/2021list_en.pdf The dynamic MSK system Skulls – What factors affect size and shape? Age Sex Genetics Diet Trauma Pathology Culture? Hydrocephalic skull Skull excavated in Samarkand, a city in southeastern Uzbekistan, estimate 600-800AD Exercise & Bone Exercise changes the mechanical environment of the skeleton Triggers cellular response and changes in bone architecture Bones adjust size and shape in response Wolff’s Law (1869) Optimisation of bone strength with respect to bone mass Alignment of trabeculae with principle stress direction Self regulation of bone cells responding to mechanical stimulus Principle Increased mechanical loading → Increased bone strength Mineralisation? Porosity? Bone mass? Principle Increased mechanical loading → Increased bone strength Increased mineralisation Decreased porosity Increased bone mass Decreased mechanical loading → Decreased bone strength Mineralisation? Porosity? Bone mass? Decreased mechanical loading → Decreased bone strength Decreased mineralisation Increased porosity Decreased bone mass Anatomical evidence Decreased bone mineral content Increased calcium secretion Acta Astronautica Vol. 43, Nos. 3-6, pp. 65-75, 1998 Experimental evidence 50 week post osteotomy Lanyon, Goodship and Pye (1982) Experimental evidence Avian model – skeletally mature turkeys Group 1: Static load Group 2: Dynamic load (100 cycle/day for 6-8 weeks) Group 3: No load Lanyon and Rubin, 1984 Control Control 100 cycles per day of intermittent loading Continuous loading Lanyon and Rubin, 1984 Anatomical evidence The aging MSK system The synovial joint (diarthrosis) All Articular cartilage Fluid filled synovial cavity Joint capsule outer fibrous membrane inner synovial membrane Some Articular discs or menisci Articular fat pads Tendons Accessory ligaments (extracapsular and intracapsular) Bursae Articular cartilage Smooth, slippery surface Transmission of loads with little friction Up to 20x more slippery than ice Devoid of blood vessels, lymphatics, and nerves Osteoarthritis Joint degeneration of articular cartilage and bone Progressive Joint pain only present when bone is damaged NOT normal aging but very common in older individuals Comparative osteoarthritis 20% of dogs over 1 year affected by osteoarthritic changes (Sanderson et al., 2009) In racehorses, the greatest number of days lost to training was caused by lameness (67.6%) (Rossdale et al., 1985) of which OA is a leading cause Sarcopenia Age related loss of skeletal muscle mass and decline in strength Decrease in size and quality of muscle Presence >50 % in >80 yr olds More than twice as fast in the lower limb than the upper limb Age 25 Age 63 http://sage.buckinstitute.org/staying-strong-countering-the-effects-of-sarcopenia/ Posture The vertebral column adjusts throughout development and its shape is influenced by supporting the weight of the head (c. 4 months) and bipedal walking (c. 1 yr) During old age KYPHOSIS typically occurs Degeneration of IVDs Osteoporosis in vertebrae Lengthening of Extensor muscles goo.gl/xpfHBW goo.gl/MQFJSc Gait Decrease in natural walking speed over time Men -2.5 % per decade Women -4.5 % per decade Shorter strides with age and smaller limb swings Aging process or disuse atrophy? Attempts to stabilise? Questions? Intended Learning Outcomes Components and organisation of the skeletal system Classification of joint types Growth in the musculoskeletal system tissues Components and organisation of the muscular system The effect of exercise on the musculoskeletal system How muscles contract and move the skeleton The effect of aging on the musculoskeletal system Hormones influencing the musculoskeletal system