Histology of musculoskeletal system Flashcards
The extracellular matrix of connective tissue
- contains glycoproteins and glycosaminoglycans
- hydrated gel-filling spaces
- reservoir; interstitial fluid
Types of connective tissue fibres
- Collagenous fibres; strong and flexible
- Reticular fibres; type III collagen, delicate and branching
- elastic fibres; elastin
Skeletal muscle
- voluntary contraction
- attached to bones and sphincters
- entire muscle covered by epimysium
- subdivided into fascicles and myofibres
- fascicles covered by perimysium
- myofibres surrounded by endomysium
Myofibre
- a single cellular unit of skeletal muscle
- multiple cells form one long tube
- multinucleated
- sarcolemma= cell membrane
- peripheral nuclei
- strongly eosinophilic sarcoplasm
Types of skeletal muscle fibres
Type I; slow twitch. Lots of capillaries and mitochondria; redder in colour less forceful contractions for longer
Type II; fast twitch. Fewer mitochondria; paler colour
Z-line
site of attachment of actin fibres
M-line
site of attachment of myosin
H- band
section where only myosin present
- pale with dark M-line
I- band
only actin is present
-pale with dark z-line
A-band
overlapping actin and myosin
- dark region
Smooth muscle
- involuntary contraction
- myocytes NOT fibres are spindle-shaped
- no striation
- centrally located nuclei & cigar shaped
Function of bone
- shape and support
- protection
- mineral storage
- development & storage of blood cells
Bone structure
- hardness; matrix of hydroxyapatites
- strength; collagen
- dynamic
- bone structure is unrelated to mode of development
Periosteum
- lines outer surface of all bones
- outer fibrous layer
- inner osteogenic layer
- important role in bone remodelling and fracture repair
Osteoid
- extracellular matrix
- 25% water, 25% protein, 50% mineral salts
- organic components; glycosaminoglycans
- inorganic components; hydroxyapatite
Name different types of bone cells
- Osteogenic cell
- Osteoblast
- Osteocyte
- Osteoclast
Osteogenic cells
- stem cells that form osteoblasts
- osteogenic layer in the periosteum
Osteoblasts
- produces osteoid (bone matrix)
- flat; inactive
- teardrop shape; active
- cannot divide
Osteocyte
- maintains osteoid matrix
- most abundant
- communicate via stellate process
- cannot divide
Osteoclasts
- from hematopoietic cells
- monocyte lineage
- recycles osteoid
- multinucleated
- cannot divide
Types of bone
1) Woven (immature); more osteocytes, rapid growth and repair
2) Lamellar (mature); less osteocytes, more organised collagen fibres
2a) Compact bone; dense deposits of matrix
2b) Spongy bone; delicate 3D latticeworks
deposits of matrix
Compact bone
- found along outer surface especially diaphysis
- structural unit is an osteon; converts mechanical force into biochemical stimuli
- Haversian canal; central canal for nerves & blood vessels
- lamellae; concentric layers around central canal
- lacunae; spaces between lamellae, osteocytes
- canaliculi; small channels, osteocytes stellate processes
- cement layer; outer limit of osteon
- Volkman canal; transverse connection between adjacent canals
Trabecular Bone
metaphysis & epiphysis
- transmits forces from joints to compact bone
- reservoir for calcium & other minerals
- lined by endosteum
- similar structure to compact bone but without central canals
- surrounded by marrow
Cartilage cells
- perichondrium lines cartilage except at articular surfaces; outer fibrous, inner chondrogenic layers
- chondroblasts; extracellular matrix become chondrocytes in lacunae
- matrix has more sulfated glycosaminoglycans and proteoglycans are bound to collagen fibrils
- chondrocytes can divide in growing cartilage
- 2-3 daughter chondrocytes= isogenic group
Hyaline cartilage
- the most common type of cartilage
- glassy appearance of matrix
- matrix is semi-solid
- contains type II collagen fibrils
- Hyaluronic acid, chondroitin sulphate, water
Where can you find Hyaline cartilage?
developing vertebrate skeleton, epiphyseal discs, articular cartilages, joints, ribs, nose, larynx, trachea, growth plates
Elastic cartilage
- matrix contains meshwork of elastic fibres
- found in external ear, epiglottis and larynx
Fibrocartilage
- layers of hyaline matrix and dense collagen fibres
- type I collagen for strength
- groupings of chondrocytes
- found in intervertebral discs, joint capsules, ligaments, cardiac skeleton, aponeuroses
Functions of the growth plate
- bone is vascular but osteoblasts and osteocytes cannot divide
- cartilage has no blood vessels but chondrocytes can divide by mitosis
- growth of bones via orderly progression from precursor cartilage at physes.
Zones and structure of growth plates
- Zone of reserve cartilage; supplies cells to proliferating layer. Small chondrocytes, lots of matrix
- Zone of proliferation; flattened dividing chondrocytes forms columns
- Zone of hypertrophy; no cell division, cells swell, less matrix. Hypertrophic chondrocytes die due to lack of blood supply
- Zone of calcification; matrix mineralises, blood vessels enter it. Osteoblasts use template to produce osteoid
