Musculoskeletal System Flashcards
What are the muscle cells? What do they originate from?
- myocytes (muscle cells) + myofibers (muscle fibers)
- mesoderm (from myoblasts)
What is sarcoplasm? Sarcolemma? Sarcoplasmic reticulum?
- sarcoplasm: cytoplasm of muscle cells that contains glycogen + myoglobin
- sarcolemma: plasma membrane of muscle cell
- sarcoplasmic reticulum: highly specialized smooth endoplasmic reticulum of a muscle cell (regulates calcium flow)
What are the classifications of muscle tissue?
- cross-striated (skeletal + cardiac)
- smooth
- myoepithelial cells (basket cells)
Label each muscle type
- skeletal
- cardiac
- smooth
What are features of skeletal muscle?
- make up 50% of body weight
- skeletal myocytes contain multiple, peripherally located nuclei
- striations are seen in myocytes when cut longitudinally
- voluntary + fast contraction
- most insert on bones of the skeleton
- voluntary sphincters in the GI tract and urinary system, muscles of esophagus +tongue
Describe skeletal muscle development
- mesenchymal cells (myoblasts) align and fuse together forming multinucleated tubes aka MYOTUBES
- myotubes differentiate forming functional MYOFILAMENTS and the nuclei are displaced against the plasma membrane
- some do not differentiate and remain as mesenchymal stem cells called SATELLITE CELLS that function in muscle repair
How is skeletal muscle organized?
- epimysium (fascia): dense irregular CT
- fascicles, surrounded by permysium
- myofibers/myocyte, surrounded by endomysium
- myofibrils
- myofilaments
Label the indicated features of the muscle
Myofibrils are the ___________ elements of skeletal muscle, composed of repeating sections of myofilaments known as thick _______ and thin ________, that create light and dark banding
- contractile
- myosin
- actin
Tropomyosin are ______________ , actin + myosin are ______________
- regulatory protein of myofilaments
- contractile proteins
Skeletal muscle striation is due to the presence of 2 kinds of myofilaments: _____________ + _____________
The _____________ is a protein disc that bisects each ________
- A band: dark
- I band: pale
- Z-line, I-band
A ____________ is the contractile or functional unit of myocytes, which includes all elements from Z-line to Z-line.
At full contraction, z-lines (discs) will be:
- sarcomere
- drawn closer to each other
The _____________ is dark and corresponds to the area where thick and thin filaments overlap. It is mostly composed of ________.
The _____________ is pale and is composed of only _________.
- A-band, myosin filaments
- I-band, actin filaments
What is motion mediated by? How does muscle contraction occur?
- motion is mediated by muscle cells and based on conversion of chemical energy (ATP) into mechanical energy
- during muscle contraction actin filaments slide over myosin filaments, shortening the I-band
- actin + myosin are held in position in the myofibrils by other proteins (desmin, tropomyosin, and troponin)
What is the sliding filament mechanism?
- sarcomere shortens > myofilament length is constant > I-band shortens > thin (actin) filaments slide past thick (myosin) filaments
- results in contraction of muscle cell
What are the steps of muscle contraction?
- binding of calcium to troponin C (TnC)
- conformational change in tropomyosin,exposing the myosin-binding site on actin
- myosin head binds to actin; ATP > ADP moving myosin head
- bound thin filaments slide over thick filaments
- shortening of muscle fiber
Label the structures
- 1: myofibrils
- 2: sarcoplasmic reticulum (stores + releases Ca)
- 3: terminal cisterna (expanded ends of SR)
- A: transverse T-tubule
___________________ are deep invaginations of sarcolemma (plasma membrane) of skeletal and cardiac muscle cells. What do they allow to occur?
- T-tubules (transverse tubule)
- allow depolarization of the membrane to quickly spread to terror of the cell allowing release of calcium sarcoplasmic reticulum
What is the sarcoplasmic reticulum?
- equivalent to endoplasmic reticulaum but seen in smooth and striated muscle
- stores and releases calcium ions to initiate contractions
What are the types of skeletal muscle fibers?
- type 1: “red muscle” - SLOW TWITCH
- type 2: “white muscle” - FAST TWITCH, 2A + 2B
What are features of type 1 skeletal muscle?
- “red muscle”; rich in myoglobin
- SLOW twitch
- AEROBIC metabolism: fatigue resistant
- high fat, low glycogen
- many mitochondria
- myoglobin: help transfer oxygen - ex: postural muscles of mammals, pectoral muscles of migratory birds
What are features of type 2 skeletal muscle?
- “white muscle”
- FAST twitch
- ANAEROBIC metabolism: more prone to fatigue
- lowfat, high glycogen content
- few mitochondria
- less myoglobin - type 2A (aka intermediate): mixed oxidative-glycolysis; slow fatigue
- type 2B: fast-contracting, fast fatigue, glycolytic
What are features of cardiac muscle?
- cardiomyocyte: myocardiocyte: cardiac myocyte
- single cell with one central nucleus
- cross striated
- intercalated discs: gap junctions + desmosomes
- sarcoplasmic reticulum
- many mitochondria; up to 20% cell volume: requires lots of O2
What kind of muscle fiber? Label some features
- cardiac muscle
- intercalated discs: attach cardiac muscle fiber cell to each other providing strength and ability to behave as a functional syncytium
What are intercalated discs composed of?
- 1: transverse element
- anchor
- desmosome: fascia adherens or macula adherens
- serve for strong attachment
- longitudinal element
- communication
- gap junction (nexus) with ion channels
- propagate electric impulse
Label the two types of cardiomyocytes
- A: contractile cardiac muscle cells: red
- B: conductile cardiac muscle cells (purkinje fibers): pale pink
What feature is shown here? What are some characteristics?
- purkinje fibers (in heart)
- modified cardiac muscle cells wit 1 or 2 nuclei,myofibrils are sparse and restricted to periphery of cell
- arranged in groups, cells are bigger and paler than contractile cardiac muscle cells
What are features of smooth muscle cells?
- spindle shaped (fusiform) cells surrounded by a basal lamina and reticular fibers
- single centrally located nucleus
- no striations (no myofibrils, unordered actin + myosin)
- cytoplasmic dense bodes represent anchos or myofilaments (like Z bodies)
- desmosomes and gap junctions
- no T-tubules and sarcoplasmic reticulum poorly developed
- parasympathetic + sympathetic innervation
- INVOLUNTARY contraction
What are the 2 kinds of smooth muscle?
- single unit smooth muscle
- found in visceral organs
- cells behave like syncytium contracting in network
- sparse nerve innervation, but cells communicate via multiple gap junctions - multi-unit smooth muscle
- found in iris (ciliary muscles)
- precise contraction
- individual innervation of each myocyte
- lack of gap junctions, function individually
What are functions of smooth muscle cells?
- peristalsis: wave-like contractions (ex: gi tract)
- vascular dynamics: contraction alters blood flow, important in blood pressure
- propulsion: urinary badder, uterus
- secretion: minor role
How are the layers of the tunica muscularis arranged in the walls of luminal organs? What kind of contraction?
- inner circular
- outer longitudinal
- non-voluntary
What are the black arrows indicating? What will happen to this cell during contraction?
- dense bodies: equivalent of Z discs of skeletal and cardiac muscle
What are features of myoepithelial cells?
- contractile non-muscle cells
- ectodermal origin
- contain actin/myosin
- similar to smooth muscle
- can be stimulated by hormone (mammary gland)
- basket-like shape > BASKET CELLS
- located: salivary, mammary, lacrimal glands
What are these 2 contractile non-muscle cells and what are they derived from?
- myoepithelial cells/basket cells; ectoderm
- close clusters of glandular cells
- myofibroblasts: mesoderm
- wound contraction
_________ are postitioned between basal lamina and sarcolemma of the muscle cell. They retain _________ and so can accomplish some repair.
___________ also form connective tissue (scars) as part of the repair process
- satellite cells
- mitotic potential
- fibroblasts
________ muscle cells lack the ability to regenerate
________ muscle regeneration is limited. In addition to some mitotic activity, new smooth muscle cells may be derived from ______________________ cells
In all muscle types, repair is completed by scar tissue formation and requires _______________
- cardiac
- smooth, pericapillary mesenchymal
- intact basal lamina
What are features of bone?
- alive and constantly remodeling
- osteoid: 90% collagen and inorganic (mineral) components
- hydroxyapatite (Ca10(PO4)6(OH)2) - bones are organs; in that they are a major part of the skeletal system
- lightweight but strong, with internal flexibility because of spongy bone (spicules w/ space between)
What are functions of bone?
- protect other organs
- produce hematopoietic cells
- store minerals
- provide structure + support
What are the two main layers of bone?
- trabeculae (T)
- cancellous or spongy bone
- large surface area; bone marrow
- cortical (C)
- aka compact bone, more dense
Label the features of this bone
- T: trabecular bone
- C: cortical bone
- E: epiphysis
- D: diaphysis
- M: metaphysics
- P: physis = growth plate
- AC: articulate cartilage
What kind of bone is this? What are some features?
- lamellar bone
- strong mature bone, forms slowly
- collagen fibers in matrix arranged in parallel layers (lamellae)
- results in strong mature bone (osteoid)
- organized into osteons (haversian systems) in mature cortical and trabecular bone
What kind of bone is this? What are some features?
- woven bone
- weak, immature, produced quickly
- disorganized arrangement of collagen fibers
- present at sites of rapid bone formation (ex: fracture repair, inflammation, neoplasia)
- ex: periosteal new bone or reactive bone
- ** can be re-modeled into lamellar bone
__________, the functional unit of lamellar bone is located in circles around the central canal (haversian) and in the interstitial bone between circles of bone.
What are some features?
- osteon
- in mature bone (lamellar), not woven bone
- located in cortex, trabeculae of bones
- volkman’s canals run in bone and connect haversian (central) canals
Label the structures of bone
- osteon: circles of lamellar bone around central canal. Small holes with lacunae are osteocytes
- blood vessels
- central canal
- osteocyte within a lacuna
- canaliculi: thin channels between lacunae
What is this?
- osteon
Label the features
What are cellular elements of bone tissue?
What are features of osteoblasts?
- along bone spicules
- produce osteoid (organic component of bone material) and initiate mineralization
- some osteoblasts become surrounded by osteoid and embedded in the bone (become osteocytes)
What is this? What are some features/functions?
- osteocytes
- most abundant cells
- reside in lacunae surrounded by mineralized matrix (long filipods to increase their cell area)
- regulate exchange of Ca2+ (and other ions) between bone
- fluid and ECF under influence of parathyroid hormone
What is this? What are some features/functions?
- osteoclasts
- parathyroid hormone (PTH) stimulates activity
- bone resorption
- reside in shallow pits (Howship’s lacunae)
- acid demineralizes bone and enhances activity of acid hydrolases released from osteoclasts (extracellular digestion)
Label the figure
- A: osteoblast
- B: osteoclast
- C: osteocyte
- D: mesenchyme
- E: bone matrix
- F: osteoid
- osteoblasts are rounded, form a single row of cells along trabeculae
- osteocytes are thinner and located within lacunae embedded in bone
- osteoclasts are multinucleated cells located along trabeculae and will absorb bone under stimulation of cytokines secreted by osteoblasts or inflammatory cells
What are the cellular elements of bone?
What systemic hormones affect bone?
- parathyroid hormone (PTH): promoted bone resorption
- 1,25-dihydroxyvitamin D3: required for normal bone growth and mineralization; also stimulates bone resorption
- glucocorticoids: inhibit formation and stimulate resorption
- calcitonin: inhibits bone resorption
- estrogen: inhibits bone resorption
- insulin, growth hormone, androgens, and thyroid hormones are also included in bone metabolism
What are the elements of bone matrix?
- osteoid (organic component) contains:
- type i collagen: (~90%)
- osteonectin: mineralization
- osteocalcin: vitamin k dependent, mineralization
- proteoglycans: less abundant than in cartilage
- growth factors: ex: BMPs, IGFs, TGFs, FGFs
- hydroxyapatite (inorganic component): needle-like crystals, mineral
Describe matrix mineralization
- in bone, osteonectin and osteocalcin absorb to type i collagen and bind Ca2+
- osteoid is not mineralized immediately (5-10 day delay)
- failure to mineralized = rickets = osteomalacia = soft bones/fractures
What are the two types of bone development?
- intermembranous ossification: increases WIDTH; IN ADULTS
- bone formed from mesenchymal tissue in periosteum
- occurs in flat bones of skull and pelvis and on periosteal surfaces throughout life
- NO CARTILAGE NEEDED
- endochondral ossification: increases LENGTH; IN YOUNG
- bone formed from hyaline cartilage precursors in physes
- most bones develop by this method (appendicular, axial, base of skull)
- HYALINE CARTILAGE PRECEDES and is scaffold
What are the stages of endochondral ossification?
Label the image
- M: metaphysis
- arrow: physis
- E: epiphysis
What is this image a example of?
- physis = growth plate
What are functions of cartilage?
- semi-rigid support to specific sites (ex: between bones, joints, ligaments, respiratory tree,intervertebral discs)
- shock absorber in menisci + intervertebral discs
- protects ends of bones
What are the 3 kinds of cartilage?
- hyaline
- elastic
- fibrocartilage
What is the function of ligaments?
- provide stability of joints, connect BONES to BONES
What is the function of tendons?
- strong flexible connections between BONE and MUSCLE
What is the function of joints?
- varying degrees of movement and flexibility; lubricated spaces with fluid between bones
What does cartilage originate from?
- mesenchymal cells
- differentiation and maturation is most advanced at the center of growing cartilage, and immature at the periphery aka PERICHONDRIUM
- at completion, cartilage consists of chondrocytes embedded in extracellular matrix
- perichondrium contains elongated fusiform cells that resembles fibroblasts, which give rise to chondroblasts
What are features of cartilage?
- AVASCULAR
- semi-rigid form of connnective tissue characterized by absence of blood vessels,lymphatic vessels and nerves(in adults)
- young animals have blood vessels in growing cartilage
- supports soft tissues (ear, eyelid, trachea, bronchi)
- important for longitudinal growth (endochondral ossification)
- composed of cells (chondrocytes) embedded in amorphous gel-like substance and connective tissue fibers, making it resilient
What is this image showing? label the arrows
- cartilage
- A: chondrocyte
- B: lacunar space
- C: matrix in intercellular region
What are the steps of chondrogenesis?
T/F: mature cartilage has a fast cell turnover and replacement of cells
- false; slow
What is a cluster of chondrocytes formed through the division of a progenitor cell; found in hyaline, elastic, and fibrocartilage?
- isogenous group
Where does primary ossification centers form first?
- epiphyses
What is this image of? Label the features
- metaphysis
- 1: zone of reserve/resting cells
- 2: zone of proliferation
- 3: zone of hypertrophic cells
- B: primary spongiosa: bone that forms on dead mineralized cartilage “scaffold”
Label each cartilage type and where it can be found
- A: hyaline
- joints: articulate cartilage
- ribs
- physes
- nose
- B: elastic
- ear
- epiglottis
- flexibility needed
- C: fibrocartilage
- menisci discs
- insertions of tendons & ligaments
What is cartilage type based on?
- the amount of collagen or elastic fibers present in the extracellular matrix
- amount of GAGs
What is the most abundant cartilage type?
- hyaline
What kind of cartilage is shown? Where is it found?
- hyaline cartilage
- growth plates (physes)
- articular cartilage covers joint surfaces at costochondral junctions of the ribs, nasal septum, larynx, tracheal rings, and bronchi
- fetal axial + appendicular skeleton
What kind of cartilage is shown? What are some features?
- elastic
- has a perichondrium, chondroblasts, and chondrocytes in large lacunae
- contains abundant elastic fibers (stain dark)
- flexible tissue due to presence of numerous bundles of branching elastic fibers in the matrix
- found in epiglottis and corniculate/cuneiform processes of the arytenoid cartilage, external auditory canal and ear pinna
What type of cartilage is this? What are some features?
- lacks a perichondrium (no regenerative capacity)
- fibrocartilage contains chondrocytes and lacunae
- features are intermediate between cartilage and dense fibrous CT
- contains type i collagen fibers
- located where support and tensile strength are required:
- intervertebral discs (annulus fibrosus)
- menisci
- insertions of tendons + ligaments
- mandibular symphysis
- pubic symphysis
What is this image of? What are some features?
- perichondrium
- outer layer: dense fibrous CT, resembles mature fibroblasts
- inner layer: cellular, chondrogenic,contains cells with capacity o become chondroblasts
- present in all hyaline cartilage
- but not articular surfaces/cartilage
What is this image showing?
- cartilage matrix
- components: collage, elastic fibers, proteoglycans (GAGs)
- basophilia of cartilage matrix due to high concentration of GAGs
- matrix near chondrocyte clusters (territorial) is more basophilic than matrix further away (interterritorial)
What are GAGs?
- sulfated polysaccharide units (GAGS = glycosaminoglycans)
- ex: chondroitin sulfate, keratin sulfate, dermatan sulfate, heparan sulfate,and hyaluronan
- GAGs bound to protein core forming macromolecules called proteoglycans that are responsible for the strong and flexible property of cartilage (shock absorption)
- within the matrix, GAGs are imbedded at varying proportions of collagen and elastic fibers giving rise to the different types of cartilage
What is shown? What are some features?
- tendon
- ~85% collagen (98% type i)
- 2% elastin
- 1-5% proteoglycans
- parallel bundles of fibers
- function: attachments, flexibility
- limited regenerative capacity
- following injury, lays down type iii collagen (scar tissue) making it less flexible and prone to re-injury
What are the kinds of joints?
- fibrous (synarthroses)
- cartilaginous (amphiarthrosis)
- synovial (diarthrosis) aka “true joints”
What are features of fibrous joints ?
- synarthroses
- bones or cartilage united by fibrous tissue
- 3 types:
- sutures (ex: cranial suture)
- syndesmosis (ex: tibia-fibula)
- gomphosis (ex: tooth socket)
What are features of cartilaginous joints?
- amphiarthrosis
- bones or cartilage united by hyaline cartilage (costochondral joints) or fibrocartilage (ex: pelvic and mandibular symphysis)
What are features of synovial joints?
- diarthrosis aka true joints
- unite two bone ends and are covered by articular (hyaline) cartilage and are surrounded by a thick articular capsule
- joint cavity consists of:
- capsule composed of fibrous portion
- well-vascularized synovial membrane lined by 2 cell types
- type A cell: phagocytic function (remove debris)
- type B cell: secrete hyaluronic acid and protein complex (mucin) into synovial fluid to help lubricate, protect and give nutrition to joints
What are features of articular cartilage? Articular capsule?
- articular cartilage:
- smooth surface
- type ii collagen + proteoglycans
- lacks blood vessels and nerves (poor regenerative capacity)
- firmly reached to subchondral bone
- articular capsule:
- thick sac of connective tissue that covers entire joint and provides additional joint stability
What are features of the synovial membrane? Synovial fluid?
- synovial membrane
- thin membrane with lots of villi
- superficially lined by a continuous layer of specialized cells (synoviocytes)
- synovial fluid
- clear, viscous, colorless or slightly yellow fluid produced by type B synoviocytes (low cellular Ty and protein content)
- function to reduce friction
- increases in joint diseases (effusion)
What is this? What is labeled A?
- joint synovium
- synovial epithelium
