APPP 24: Anatomy and Physiology of the Musculoskeletal System Flashcards
What are the 2 main functions of the MSK system?
- stability: shape, support, and protect
- motility: movements
What are the 2 additional functions of the MSK system?
- bone: blood production
- storage of nutrients: minerals (calcium, phosphorous), glycogen (carbohydrates), and fat
What are the different types of bones? (5)
- long
- short
- flat
- irregular
- sesamoid
What are the 5 functions of bones?
- provide shape/structure to support soft tissues
- protection (skull protects brain, ribs protect heart and lungs)
- levers for muscle to exert force against
- storage for calcium (99%), phosphorous (75%), and fat (yellow marrow)
- sites of blood cell production (hematopoiesis in red marrow)
What is bone made of?
specialized connective tissue (mostly calcified, but living and growing)
- extracellular bone matrix
- three major cell types
- also contains fibroblasts, nerves, blood and lymphatic vessels in mesenchymal regions
What are the 2 components of the extracellular bone matrix?
- organic collagen (90%) and non-collagenous proteins (ie. proteoglycans 10%)
- non-organic calcified extracellular material hydroxyapatite (calcium phosphate and a little calcium carbonate) – makes bone hard
What are the 3 major cell types of the bone?
- osteocytes
- osteoblasts
- osteoclasts
What are osteocytes?
mature bone cells
- contribute and maintain bone mass
- cannot form new bone
What are osteoblasts?
growing cells
- synthesize and secrete osteoid organic components of the matrix and differentiate to osteocytes
- generate new bone
What are osteoclasts?
monocyte-derived multinucleated cells responsible for bone resorption and remodeling
What is the epiphysis?
end part of a long bone, initially growing separately from the central bone
- bone grows from here
What is the diaphysis?
shaft or central part
- not growing
What is the periosteum?
- fibrous covering that contains blood and lymphatic vessels, nerves
- inner layer contains osteoblasts that form bone
What is hyaline cartilage (or articular cartilage)?
where joint forms
What is compact bone?
calcified bone layer
What is spongy (or cancellous) bone?
contains red marrow (blood cells)
What is the marrow cavity?
contains yellow marrow
What is the endosteum?
osteoclast layer in marrow cavity
What are osteons?
functional units of bone
- cylindrical
- concentric layers of bone called lamellae
- central has blood vessels, lymph vessels, and nerves pass
- osteocytes sit between small spaces around a central canal (lacunae)
- canaliculi are microscopic canals connecting osteocytes?
What does bone growth and remodeling involve?
both continuous generation of new bone and continuous resorption of bone tissue
What is bone remodeling needed for?
- maintain bone shape, while increasing its mass
- deal with changes, stresses, and repairs
- release of calcium in systemic circulation, as bone serves as a calcium storage
Describe the steps of bone remodeling.
- resting bone
- bone resorption by osteoclasts
- bone resorption by mononuclear phagocytes
- recruitment of osteoblast precursors
- secretion of new matrix (brownish shading) by osteoblasts
- continued secretion of matrix, with initiation of calcification
- completion of mineralization of new matrix
What is osteoporosis?
loss of old bone, creation of new bone does not keep
- excessive loss of bone structure
- natural loss of calcium from bones over time result in more fragile bones
What are the risk factors for osteoporosis?
- sex: women > men
- age: older > younger (over 40)
- race: greater risk in white or Asian descent
- family history
- body frame size: greater risk in small body frames
- hormone levels: lowered sex hormone, high thyroid
- dietary factors: low calcium intake
- medical conditions
What is cartilage?
tough, durable connective tissue
- acts as cushion with mechanical and protective roles within the adult skeleton (joints) and other soft tissues such as lung, nose, ear, etc.
What are the 3 major forms of cartilage?
- hyaline (glassy) cartilage – most common
- elastic cartilage
- fibrocartilage
Describe the structure and components of cartilage.
- chondrocytes: produce collagen and proteoglycans (small % of mass)
- extracellular matrix: collagen and abundant proteoglycans, which can bind a large amount of water
- lack blood vessels, lymphatics, and nerves
- surrounded by perichondrium, which is provided with vessels
Describe the repair or replacement of injured cartilage.
very slow and ineffective, due in part to the tissue’s avascularity and low metabolic rate
What are joints?
where bones meet/articulate
- allows some bending/movements for bones
What are the 2 functional types of joints?
- synarthroses
- diarthroses or synovial joints
What are synarthroses joints?
no/very limited movement joints
- no joint cavity
- found in skull, invertebral discs
- collagen loss or other degenerative changes can lead to a slipped disc
What are diarthroses or synovial joints?
- have joint cavity
- found between most bone-to-bone contacts (ie. knee, elbow, knucles, etc.)
What are synovial joints and their structure?
surrounded by the articular capsule (encloses the joint)
- outer layer: fibrous layer of ligaments
- inner layer: connective tissue called synovial membrane that secretes synovial fluid (clear, viscous liquid, lubricant)
What is a joint cavity?
area surrounding bone ends that contain synovial fluid
What is the synovial membrane?
special connective tissue
What are the 2 main cell types in the synovial membrane?
- macrophage-like type A cell
- fibroblast-like type B cell
What are macrophage-like type A cells?
- derived from blood monocytes
- remove wear and tear debris from synovial fluid
- regulate inflammatory events within diarthrotic joints
What are fibroblast-like type B cells?
produce synovial fluid containing hyaluronan and proteoglycans
What is arthritis?
inflammation → thinning of synovial cartilage → swelling of one or more joints leading to joint pain, stiffness, and immobilization
What is osteoarthritis (OA)?
most common form of arthritis
- degenerative, progressive, and age-related joint disease
- mainly joints in hands, hips, and knees
What is rheumatoid arthritis (RA)?
an autoimmune and inflammatory disease
- early onset possible
- involves tissue damage
- mainly joints in hands, wrists, and knees
What are ligaments?
fibrous tissue connecting bone to bone
- stabilize joints
- provide rotational stability to the knee
- difficult healing, common site of injuries
What are tendons?
strong and flexible collagen fibrous tissue connecting muscles to bones
- transmit the mechanical force of muscle contraction to the bones to moving limbs
- resist tensile forces
What are the 3 major types of muscle?
- skeletal (striated) muscle
- cardiac muscle
- smooth (visceral) muscle
What are the 4 functions of muscles?
- movements/postures
- blood circulation
- body heat
- storage of carbohydrates (glycogen)
What are skeletal (striated) muscle?
- present in locomotor system
- cells are cylindrical, striated, multi-nucleated
- voluntary movements
- connected to CNS
What are cardiac muscles?
- present in heart
- cells are cylindrical, striated, multi-nucleated but thinner
- involuntary, vigorous, and rhythmic movements
- innervated by PNS
What are smooth (visceral) muscles?
- present in organs
- cells are spindle-like shape, striated (least striated of all muscle types), single nucleus
- involuntary but slow movements
- innervated by PNS
Describe muscle anatomy from outer to inner layers.
- epimysium: dense connective tissue
- several fascicles – bundles of muscle fibres wrapped around by perimysium
- each muscle fibre surrounded by endomysium
- also have blood vessels and nerves
(note: each muscle fibre is a functional unit)
Skeletal Muscle Fibre
What are t-tubules?
invaginations of sarcolemma
Skeletal Muscle Fibre
What are the components of muscle cells/myofibres? (6)
- sarcolemma (plasma membrane)
- sarcoplasm
- many nuclei
- mitochondria
- sarcoplasmic reticulum: storage of Ca2+
- microfibrils: rod-like organelle containing thick and think myofilaments
Skeletal Muscle Fibre
What are sarcomeres?
smallest and repeating functional unit of striated muscle tissue
Skeletal Muscle Fibre
What are thick filaments?
myosin
- moving using motor head along actin to contract sarcomere
Skeletal Muscle Fibre
What are thin filaments?
actin
- immobile
- tropomyosin blocks myosin
- tropomyosin shift with Ca2+
Skeletal Muscle Fibre
What is the sliding theory of muscle contraction?
- depolarization of muscle membrane
- release of Ca2+ from internal stores (SR)
- binding of Ca2+ to actin
- sliding of myosin along actin
- muscle contracts to generate tension
- muscle only pulls and does not push
- pull and relax
Which nervous system does the musculoskeletal system work with?
central nervous system (CNS)
What are the steps of AP generation in muscle fibres at the neuromuscular junction?
- transmission of motor neuron signal
- increased permeability of Ca2+ at neural ends of a synapse
- release of ACh from synaptic vesicles
- binding of ACh to nicotinic receptors (on muscle ends of a synapse)
- Na+ influx
- change endplate potential and depolarization
- muscle fibre action
- propagation of signal, OR turn off signal (degradation of ACh by acetylcholinesterase)
Describe the structure and functionse of nicotinic receptors as ion-channel linked receptors.
consists of a pentamer of protein subunits with two binding sites for ACh
- when bound, receptor’s configuration is altered, resulting in the opening of the internal pore
- pore allows Na+ ions to flow down their electrochemical gradients
What is proprioception?
the sense through which we perceive out body’s position, movement, equilibrium/balance, and notion of force
What are proprioceptors and their functions?
nerve fibres that coordinate position of joints, tension in tendons and ligaments, and the state of muscular contraction
What are the 2 types of proprioceptors?
- muscle spindle afferents
- mechanoreceptors from skin and joints
What contributes to coordination?
motor command and signals from CNS
What is a reflex?
stereotypic reaction to a certain trigger
ie. patellar/knee jerk reflex
What is the reflex arch?
functionally harmonize muscle movements (muscle agonist vs. antagonist)
What are sensory neurons?
stretch receptors of the muscle that conveys changes in muscle length to CNS
What do motor neurons do?
send signal from CNS to muscles
What are neuromuscular diseases?
disorders affecting the function of muscles due to problems with nerves and muscles
- most common sign is muscle weakness
What is myasthenia gravis?
autoimmune disorder of neuromuscular transmission
- produce antibodies against nicotinic ACh receptor (AChR)
- abnormal immune response results in decreased activity and number of ACh receptors, causing failed nerve transmission at certain neuromuscular junctions
What are the symptoms of myasthenia gravis?
- dropping of one or both eyelids (ptosis)
- blurred or double vision (diplopia) due to weakness of the muscles that control eye movements
- change in facial expression
- difficulty swallowing
- shortness of breath
- impaired speech (dysarthria)
- weakness in arms, hands, fingers, legs, and neck
