Anatomy Notes Week 5 PDF

Skeletal system tissues 1. Cartilage – non-vascular connective tissue (CT) i) hyaline cartilage – smooth cartilage at movable joints  covers the end of most long bones; also forms the costal cartilage ii) fibrocartilages – pad-like cartilage  intervertebral disks and pubic symphysis Skeletal...

Skeletal system tissues 1. Cartilage – non-vascular connective tissue (CT) i) hyaline cartilage – smooth cartilage at movable joints  covers the end of most long bones; also forms the costal cartilage ii) fibrocartilages – pad-like cartilage  intervertebral disks and pubic symphysis Skeletal system tissues 2. Bone – vascular CT a b c Cells: osteoprogenitor stem cells (a) that give rise to: i) osteoblasts (b) – build the matrix ii) osteocytes (c) – maintain the matrix iii) osteoclasts (d) – reabsorb the matrix Matrix: collagen and hydroxyapatite (Ca2+ salt) rich ground substance, small amount of H2O a) compact bone  forms the external surface of all bones  possesses osteons (Haversian system) d a a) compact bone Osteon – elongated concentric pillars running lengthwise down the bone, each with a central (Haversian) canal Structure: i) lamellae – concentric rings of bone matrix ii) lacunae with osteocytes – found between rings of lamellae iii) canaliculi – canals connecting lacunae in adjacent rings iv) central canals – for nerves and blood vessels v) perforating canals – connect blood and nerve supply of periosteum with the central canals and medullary cavity  iii) & v) run perpendicular to long axis of bone 2. Bone b) spongy bone – no osteons  found primarily in epiphyses of long bones, and within bones of the skull, ribs, and vertebrae  possess trabeculae – irregularly arranged lamellae and osteocytes interconnected by canaliculi  open cavities of spongy bone (especially flat bones) contain red bone marrow a hematopoietic tissue – produces red blood cells Components of long bones 3 E.g. femur, tibia, humerus 1. diaphysis – long tubular shaft of bone by spongy bone; exterior composed of compact bone 2  internal medullary cavity surrounded 1 2. epiphyses – proximal and distal extremities  interior is primarily spongy bone 3. epiphyseal plate – disks of hyaline cartilage at diaphysis/epiphysis boundaries  sites of bone growth (increase length); cartilage is replaced with bone – endochondral ossification 2 3 Components of long bones 4. epiphyseal line – remnant of the epiphyseal plate once bone growth stops (i.e. onset of adulthood) 5. medullary (marrow) cavity – central core of long bone  contains red (children) or yellow (fat; adults) marrow 6. periosteum – double CT membrane layer casing outer bone surface; outer layer = dense irregular, inner = osteoblasts/clasts  site of bone growth (increase diameter) – intramembranous ossification 7. endosteum – CT membrane covering internal surfaces of the bone (e.g. trabeculae, medullary cavity, central canals) 8. articular cartilage – thin smooth layer covering the joint surfaces of long bones (reduces friction) Skeletal Muscle System  muscle type composed of many individual cells called fibres  each fibre surrounded by endomysium (CT)  groups of cells are bundled together by perimysium (CT) to form fascicles  fascicle groups bundled together by epimysium (CT) to form a whole muscle epimysium fascicle perimysium fibre blood vessels endomysium fascia Connective Tissue Components of Muscle Deep fascia – dense irregular CT separating muscle groups; often blended together with the epimysium Tendon – rope-like CT extension of epimysium, perimysium, and endomysium Aponeurosis – a very broad, sheet-like tendon palmar aponeurosis  tendons and aponeuroses are dense regular CT (primarily collagen) that anchor muscle to CT of the skeleton (cartilage or bone periosteum) or to deep/superficial fascia Structure of a skeletal muscle fibre  long, multinucleated, cylindrical cells Sarcolemma – modified plasma membrane with invaginations (T-tubules) that extend deep into the cell Sarcoplasm (=‘cytoplasm’) possesses organelles, myoglobin, myofibrils, and sarcoplasmic reticulum (SR)  SR (‘smooth ER’) has a pair of expanded regions (terminal cisternae) surrounding each T-tubule T-tubule terminal cisternae sarcoplasmic reticulum sarcolemma myofibril Structure of a skeletal muscle fibre myofibrils – bundles of thick and thin protein myofilaments  thick myofilaments: composed primarily of myosin, which has 2 globular heads projecting towards the thin myofilaments  thin myofilaments composed of actin and proteins (troponin and tropomyosin) muscle two regulatory troponin tropomyosin fascicle muscle fibre myofibril actin myosin globular heads The arrangement of thick and thin myofilaments give muscle cells their characteristic striation or banding pattern  each repeating unit of this pattern is a sarcomere Structure of a skeletal muscle fibre thin myofilament Z disk thick myofilament M line titin sarcomere H zone Z disk A band Sarcomere – the smallest unit of muscle contraction Thin myofilaments anchored on one end to a Z disk Thick myofilament anchored to Z disk (via titin) and to the M line A band – dark band; equals the length of thick myofilaments H zone – lighter band at center of A band (myosin only) Structure of a skeletal muscle fibre Z disk M line I band H zone A band Z disk I band – light band between adjacent A bands (actin, titin, Z disk) Z disks – connection points between sarcomeres M line – supporting proteins holding thick myofilaments together T-tubules – encircle myofilaments at junctions of A and I bands Note: actin myofilaments outnumber myosin myofilaments by a 2:1 ratio myofibril cross section Articulations and joints  the points of contact between bones 1. Functional classification  based upon the degree of joint movement i) synarthrotic – immovable (e.g. sutures in skull) ii) amphiarthrotic – slightly movable (e.g. pubic symphysis) iii) diarthrotic – freely movable synovial joints (e.g. hip, knee, elbow) Articulations and joints 2. Structural classification – based upon: a) presence or absence of a joint cavity b) type of connecting tissue i) fibrous joint – no joint cavity  fibrous CT binds bones together (e.g. sutures in skull) ii) cartilaginous joint – no joint cavity  cartilage connects adjacent bones (e.g. intervertebral disks, costal cartilage) iii) synovial joint – has a joint cavity  bones held together by an articular capsule and fibrous CT (ligaments) – e.g. hip, knee, elbow, shoulder Structure of synovial joint synovial membrane 1. Articular (hyaline) cartilage on joint interfaces fibrous capsule 2. Joint cavity containing synovial fluid synovial fluid ligaments 3. Articular capsule – encloses cavity and unites bones: i) internal synovial membrane layer – secretes synovial fluid ii) external layer – fibrous capsule (dense irregular CT) continuous with the periosteum of adjacent bones iii) reinforcing ligaments – band-like capsular or extracapsular CT for additional joint strength Types of synovial joints  based on the shape of their articular surfaces 1. gliding (plane) joint – e.g. sacroiliac joint, carpals  flat articular surfaces – allow only short gliding movements 2. hinge joint – e.g. knee, elbow  convex projection of one bone fits into concave depression of another; permits flexion/extension 3. pivot joint – e.g. superior ulna/radius, atlas/axis  rounded end of one bone projects into ring or groove of another; permits uniaxial rotation 4. ball and socket joint - e.g. femur and acetabulum  spherical head of one bone articulates with socket of another; permits movement in all planes Skeletal movement origin Most muscles span a joint, connecting two adjacent bones insertion Origin – attachment point of muscle to the stationary bone Insertion – muscle attachment point on the moveable bone A lever system is thus formed, with the joint acting as a fulcrum and the moveable bone as a lever  muscle contraction (shortening) pulls the insertion (lever) towards the origin, causing bending at the fulcrum (joint) Skeletal movement Most movements incorporate two or more muscles (group action) i) agonist – the major muscle producing movement ii) antagonist – contraction produces the opposite movement  is inhibited when the agonist contracts iii) synergists – help agonist produce the desired movement Skeletal movement origin 1. agonist – biceps brachii flexion origin = scapula insertion = radius triceps extension lever = ulna/radius fulcrum = elbow joint insertion movement = flexion 2. antagonist – triceps brachii (extensor) 3. synergists – brachialis and brachioradialis muscles brachialis Naming of skeletal muscles 1. Action they perform (in anatomical position) flexors – decrease the angle between two bones extensors – return bone to the anatomical position following flexion abductors – move limb away from the midline adductors – move limb toward the midline 2. Shape of muscle e.g. deltoid – ‘delta’ (∆) shaped e.g. trapezius – trapezoid ( ) shaped Naming of skeletal muscles 3. Site of origin/insertion origin e.g. brachialradialis o – humerus (‘brachi’ = arm) i – radius 4. Location e.g. tibialis anterior – anterior tibia 5. Relative size e.g. gluteus maximus, g. medius, g. minimus insertion Naming of skeletal muscles 6. Direction of muscle fibres e.g. rectus abdominus (‘rectus’ = straight) e.g. external obliques (\\\ ///) 7. Number of origins e.g. biceps brachii – 2 origins e.g. triceps brachii – 3 origins e.g. quadriceps femoris – 4 origins Labs: For each Joint need to know: i) the actions that occur ii) which muscles cause these actions iii) origin/insertion site of these muscles Joint Action Muscle Origin Insertion Knee flexion hamstrings os coxa tibia extension quadriceps os coxa tibia deltoid scapula humerus pectoralis major sternum humerus Shoulder* abduction adduction *other actions at this joint (e.g. flexion, extension, rotation)