Musculoskeletal Histology Flashcards
How are skeletal muscle cells structured?
Striated
Unbranched
Multinucleate (forms a syncytium)
Where are the nuclei in skeletal muscle cells?
At the periphery of the fibre, just under the sarcolemma (cell membrane)
What is a fasicle?
A group of muscle fibres
What is the name of the connective tissue that surrounds the whole muscle?
Epimysium
What is the name of the connective tissue that surrounds a single fasicle?
Perimysium
What is the name of the connective tissue that surrounds a single muscle fibre?
Endomysium
What is a motor unit?
One motor neurone and all the muscle fibres that it innervates
The fewer the number of muscle fibres in a motor unit, the finer the control (eye muscles)
What is type 1 skeletal muscle?
Slowly contracting Depends on oxidative metabolism Abundant mitochondria and myoglobin Resistant to fatigue and produce relatively less force RED fibres
What is type 2a skeletal muscle?
Relatively fast contracting
Reasonably resistant to fatigue
What is type 2b skeletal muscle?
Fast contracting fibres
Depend on anaerobic metabolism
Few mitochondria and less myoglobin than type 1
Fatigue easily and produce a greater force
WHITE fibres
How can cartilage be described?
Semi-rigid and deformable
Permeable
Avascular
Cells nourished by diffusion thorugh ECM
How can bone be described?
Rigid
Not permeable
Cells within bone must be nourished by blood vessels that pervade tissue
What is a chondrocyte?
Active cells that secrete and maintain the extracellular matrix
Where can chondrocytes be formed?
They live in the lacuna
What is the composition of extracellular matrix in cartilage?
75% water
25% organic material: 60% type 2 collagen, 40% GAGs
What are the different types of cartilage?
Hyaline cartilage (most common) Elastic cartilage (flexible) Fibrocartilage (type 1 collagen with rows of chondrocytes surrounded by cartilaginous ECM
Where can hyaline cartilage be found?
Articular surfaces Tracheal rings Costal cartilages Epiphyseal growth plates Precursor in fetus to bone
What type of bone makes up the diaphysis?
Cortical bone
What type of bone makes up[ the epiphyses?
Cancellous/ trabecular bone
What is bone made from?
Type 1 collagen
Bioapatite (calcium, phosphorus, hydroxyapatite)
Water
What bone will never remodel?
Otic capsule
What is contained within the haverisan canal?
Blood vessels
What is the volkmann’s canal?
Connects haversian canals to the periosteum
What is an osteocyte?
When osteoblasts become trapped in the matrix that they secrete, they become osteocytes. Osteocytes are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste through gap junctions.
What envelops osteons?
Cement lines
What is the main difference between trabecullar and cortical bone?
Trabecullar bone tends to NOT have haversian canals
What is an osteoprogenitor cell?
Located on bone surface, serve as a pool of reserve osteoblasts
What is an osteoblast?
Bone forming cells found on the surface of developing bone
Plentiful RER and prominent mitochondria
What is an osteocyte?
A bone cell trapped within the bone matrix
What is an osteoclast?
Large multinucleated cells
Found on the surface of bones and are responsible for bone resorption
Which cell drills into bones forming a tunnel?
Osteoclasts
How do osteoblasts enter the new bone?
A blood vessel grows, bringing with it osteoblasts which will line the tunnel and begin to lay down new lamellar bone
When will osteoblasts stop producing lamellar bone?
When the only space left is that of a haversian canal
What is osteoid?
Collagen, GAGs, proteoglycans and other organic compounds secreted by osteoblasts
What are osteoclasts derived from?
Macrophages
What is woven bone?
During foetal development or after a break, the collagen fibres layed down are not lamellar but haphazard creating weaker woven bone
How does woven bone become lamellar bone?
It is remodelled into lamellar bone by being broken down by osteoclasts and reformed by osteoblasts
