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JamiThompsonSkeletalSystem/Tissues,Joints,SkeletalMuscle (Skeletal…

- - - - sphincter muscles encircle many body openings and function as valves, relax to allow passage of substance, contract to close passageway
    - - when awake, skeletal muscles contract continuously to maintain posture, enabling the body to remain standing or sitting, muscle tone (constant low-level contraction), stabilize and strengthen many synovial joints
    - - skeletal muscle attaches to the skeleton and moves the body by moving the bones, muscle in walls of visceral organs produce movement by squeezing fluids and other substances through these hollow organs
    - - muscle contraction produces heat, plays vital role in maintaining normal body temperature
  - - - nerve signals or other stimuli excite muscle cells and cause electrical impulses to travel along the cells’ plasma membrane, these impulses initiate contraction
    - - muscle tissue can be stretched, contraction of one skeletal muscle will stretch an opposing muscle, muscular wall of a hollow organ is stretched by the substances contained within that organ
    - - contracts forcefully, cells contain myofilaments which are specific types of microfilaments that are responsible for the shortening of muscle cells
    - - after being stretched, muscle tissue recoils passively and resumes its resting length
  - - - outer layer of DICT surrounds whole skeletal muscle, sometimes blends with deep fascia that lies between neighboring muscles
    - - within each skeletal muscle the fibers are separated into groups called fascicles, layer of fibrous connective tissue surrounding each fascicle
    - - each muscle fiber surrounded by a fine sheath of loose connective tissue consisting mostly of reticular fibers
  - - - rodlike bundle of contractile myofilaments in the cytoplasm of a skeletal muscle cell, made of repeating segments called sarcomeres
    - - supplies energy for muscle contraction
    - - extension of the muscle cell sarcolemma that protrudes deeply into the muscle cell
    - - specialized smooth endoplasmic reticulum of muscle cells, stores calcium ions
    - - plasma membrane of a muscle cell
- - - - bones provide hard framework that supports body weight
    - - skeletal muscles attach to bones by tendons and use bones as levers to move the body and its parts
    - - bones of skull protect brain, vertebrae surround spinal cord, rib cage helps protect organs of thorax
    - - bones are reservoirs for minerals - most importantly calcium and phosphate, minerals are released into bloodstream as needed
    - - bones contain red and yellow marrow, red marrow makes the blood cells and yellow marrow stores fat
    - - osteoblasts secrete a hormone called osteocalcin that assists in reducing blood sugar levels and causes fat cells to store less fat and secretes hormone that increases insulin sensitivity of cells
  - - - DRCT that attaches muscles to bones
    - - "joints," point where two elements of skeleton meet
    - - DRCT that connects bones to other bones
    - - articular cartilage covers end of most bones at movable joints, costal cartilages connect ribs to sternum, see: perichondrium
    - - organic components: cells, fibers, ground substance, inorganic components: mineral salts (make bone tissue hard), small amount tissue fluid
  - - - strong to resist compression, bending and tension, occurs in the external portion of bone
    - - internally located to compact bone d/t less stress being placed on the bones, spongy bone lightens heavy skeleton, consists of trabeculae that provide open spaces for marrow
  - - - very center of diaphysis, marrow cavity filled with yellow bone marrow, no bone tissue
    - - bones well vascularized
    - - diaphysis is the shaft, epiphyses are the ends of bones, each epiphysis covered in hyaline cartilage, between two part of bone is the epiphyseal line in adults (epiphyseal plate while still actively producing hyaline cartilage cells
    - - Periosteum
        
        covers entire outer surface of bones except ends of epiphyses, 2 layers - superficial is DRCT, deep layer abuts compact bone which is osteogenic, secured to bone by Sharpey's fibers
      - Endosteum
        
        thin connective tissue membrane, lines central canals of osteons, osteogenic
  - - - storage of fat cells is responsible for yellow coloring, makes blood cells only in emergencies
    - - red bone marrow actively generates blood cells, red color is due to erythrocytes
  - - - bone-forming cell, produce/secret osteoid
    - - mature bone cell, keep bone matrix healthy, occupy lacunae in matrix
    - - stem cells, differentiate into osteoblasts
    - - large cell that resorbs/breaks down bone matrix, derived from WBC
- - - - bones connected by bundles of DRCT, carpals/tarsals, little movement
    - - between tooth and its alveolus, periodontal ligament, no movement
    - - bones connect by short interconnecting fibers, skull, no movement
  - - - consists of hyaline cartilage and fibrocartilage, pubic symphysis and intervertebral joints, slightly movable
    - - 2 bones joined by hyaline cartilage, epiphyseal plate, immovable
  - - - Synovial Fluid
        
        provides lubrication, shock absorption, nourishes articular cartilage
      - Bursa (e)
        
        sac filled with synovial fluid, exists between bone and tendon/skin/ligament/muscle
      - Presence of Joint Cavity
        
        surrounded by joint capsule, 2 layers: outer is DICT that is continuous with periosteum, inner is synovial membrane consisting of mostly areolar CT, secretes synovial fluid
      - Tendon Sheath
        
        specialized type of bursa, wraps itself around tendons
    - - Pivot
        
        sleeve (bone/ligament) and axle (rounded bone), rotation, uniaxial movement, proximal radioulnar joints
      - Condylar
        
        oval articular surfaces, flexion/extension and adduction/abduction, biaxial movement, knuckle and wrist joints
      - Hinge
        
        cylinder and trough, flexion and extension, uniaxial movement, elbow and interphalangeal joints
      - Saddle
        
        articular surfaces are concave and convex, adduction/abduction and flexion/extension, biaxial movement, thumbs
      - Plane
        
        flat articular surfaces. gliding, nonaxial movement, intercarpal/intertarsal joints
      - Ball-and-Socket
        
        spherical head (ball) and cup (socket), flexion/extension and adduction/abduction and rotation, multiaxial movement, shoulder and hip