Histology Flashcards
Why are the nuclei SK cells found at the periphery of the fibre?
cell becomes packed with filaments which push nuclei to the edge
What is the connective tissue around a single muscle fibre called?
endomysium
What is the connective tissue around a single fascicle called?
perimysium
What is the connective tissue around a whole muscle caleld?
epimysium
How are sarcomeres arranged into myofibrils?
arranged end-to-end
How are myofibrils arranged in the fibre?
like cigarettes in a pack (not end-to-end)
Why do SK muscle fibres appear striated?
sarcomeres in the myofibrils with their alternating dark and light bands are held in registry (Z-lines line up)
How are the fibres in a motor unit arranged in the muscle?
scattered across the muscle and are not bunched together
What type of fibre are the red fibres in SK muscle?
type 1- they have lots of myoglobin to store oxygen
How are cartilage cells nourished?
diffusion through extracellular matrix as cartilage is avascular
Why must bone be nourished by blood vessels that pervade the tissue?
bone is not permeable
What is the space in the extracellular matrix that condrocytes live in called?
lacuna
What is connective tissue?
has lots of volume occupied by ECM rather than by cells
What is the ECM in hyaline (most common) cartilage?
3/4- water
1/4 organice material- type 2 collagen and proteoglycan aggregates
What is the diffference between type 1 and type 2 collagen?
type 2 is finer than type 1 and instead of aggregating into linear bundles, it forms a 3D meshwork
What are proteogylcans made up of?
GAGs (polysaccharides) bound to a core protein (testtube brush- GAG is brush and protein is metal handle throughit)
What does hyaline cartilage look like?
blue-white in colour and translucent
What does elastic cartilage appear as?
light yellow
What is fibrocartilage made up of?
bands of densely packed type 1 collagen interleaved with rows of chondrocytes surroudned by small amounts of ECM
What are the 2 types of bone?
outer shell of dense cortical bone and cancellous/trabecular bone
What area of the long bone does cortical bone make up?
shaft-diaphysis
What area of long bone does cancellous bone occupy?
ends of bone- epiphyses
What is the main difference between compact and trabecular bone?
presence of spaces (marrow cavities) in trabecular bone
What is an osteon?
the functional unit of compact bone
What is the difference between Haversion canals and Volkmann’s canals?
Haversion bloos vessels go up and down the bone where as Volkmann’s go across the bone
what are the canaliculi in bone?
holes that extend in all directions from osteocytes containing osteocyte cell processes
What is the purpose of canaliculi?
processes of cells join and cells closest to the bloos canal pass nutrients to further away cells
What are only found in osteons that have formed during remodeling (not in original development)?
lines that surround the osteon- cement lines
What does trabecular bone lack in comparison to compact bone?
lacks Haversion canals (up and down)
Why doesnt trabecular bone need Haversion canals?
because the struts are thin, the osteocytes can survive from contact with the marrow spaces
Where are osteoprogenitor cells found?
bone surfaces, eg under the periosteum
What is the function of osteoprogenitor cells?
cells serve as a pool of reserve osteoblast
What are osteoblasts for?
bone forming cells found on the surface of developing bone -secrete collagen, GAGs and other organic material (collectively called osteoid)-which forms bone
What osteocytes?
a bone cell trapped within the bone matrix
What are osteoclasts
large multinucleated cell (derived from macrophages which fused and formed a multinucleated cell) which are found on the surface of bone and do bone resorption
What happens during bone remodelling?
osteoclasts drill into bone forming a tunnel, a blood vessel grows into the tunnel bringing osteoblasts wwhich line the tunnel and lay down ner laemllar bone-keeps going until only the space of a Haversian canal reamins
What is the collection of osteoclasts and osteoblasts that participate in remodelling called?
basic multicellular unit
What is the difference between lamellar and woven bone?
collagen fibres are not all orientated in one direction but in a haphazard fashion-not as strong
