Histology Flashcards
how far along muscle do muscle fibres run
origin to insertion
desribe the nuclei of skeletal muscle fibres
multinucleated
nuclei at periphery of fibre, just under cell membrane (sacrolemma)
at periphery as they have been pushed there by all the actin and myosin
what are the bundles that muscle fibres are grouped into called
fascicles
define epimysium, perimysium and endomysium
epimysium - connective tissue that surrounds the muscle as a whole
perimysium - surrounds single fascicle
endomysium - surrounds single muscle fibre
what are the units of contraction
sarcomeres
how are cartilage cells nourished
avacular but permeable - diffusion through the Extracellular matrix
how are bone cells nourished
by blood vessels that pervade the tissue
what are the resident cells in cartilage
and what were they called when they were immature
chondrocytes
chondroblasts
where do chondrocytes live
in a space in the extracellualr matrix called a lacuna
what do chondrocytes do
produce and maintain ECM
what is the most common form of cartilage
ECM (hyaline)
what is ECM formed from
75% water
25% type II collagen and proteoglycan aggregates made up of GAGs
how does type II collagen differ from type I
type II is finer and forms a mesh instead of linear bundles
what is the most common form of cartilage in connective tissue
type I
hyaline cartilage example
tracheal ring
elastic cartilage and example
elastic fibres make it flexible
eg penna of ear
fibrocartilage and example
eg minisci of knee
hybrid between tendon and hyaline cartilage
bands of densely packed type I collagen interleaved with rows of chondrocytes surrouned by small amounts of cartilagenous ECM
functions of the bone
support, lever, protection
calcium store
haemopoiesis
haemopoiesis in the bone
production of RBC and platelets in bone marrow
by early 20s only the axial and limb girdle skeleton is involved in blood production
where is blood produced in utero
liver and spleen
composition of bone
what are the 2 types of bone
outer shell of dense hard cortical bone that makes up shaft (diaphysis)
cancellous/trabecular/spongy bone occupies the ends of the bone (epiphyses)
where are the marrow cavities found
- adipose tissue is found in the medullary cavity of the diaphysis
- red marrow is found in the proximal cancellous material of bones and the flat bones
compare the bone cells and matrix of compact and trabecular bone
- similar, but the trabecular bone has marrow cavities in it
- both types are lamellar - made up of layers
cortical bone
what are the haversion canals in cortical bone surrounded by and what do they contain
layers of lamellar bone
contain blood vessels
what are canaliculi
Bone canaliculi are microscopic canals between the lacunae of ossified bone. The radiating processes of the osteocytes project into these canals
what are cement lines in cortical bone
lines that are visible surrounding the osteon
are only found in osteons that have formed during remodelling (not original development)
describe osteocytes and haversion canals in trabecular bone
has osteocytes and is lamellar in nature
lacks Haversian canals
osteoprogenitor cells
located on bone surfaces, pool of reserve osteoblasts
osteoblasts
bone forming cells on surface of developing bone
plentiful RER and prominent mitochondria
osteocytes
bone cell trapped within bone matrix
osteoclast
large multinucleated cells
responsible for bone resorption (destroyer)
describe bone remodelling
osteocalsts congregate and drill into bone forming a tunnel
blood vessel grows in the tunnel and brings with it osteoblasts which line the tunnel and begin laying down new lamellar bone
process continues until only space of Haversian canal remains
what is the collection of osteoblasts and osteoclasts that participate in bone remodelling called
basic multicellular unit
what do osteoblasts secrete
components of the matrix (collagen, GAGs, proteoglycans etc) that is collectively called an osteoid
what is the mineral of bone made up of
principally Ca phosphate
what lineage of cells are osteoclasts believed to be from
macrophage
they fuse and form a single giant cell
what do young remodelling osteons often do to older osteons
obliterate them
howis bone laid down during development/following break
differently from normal lamellar bone
angle of deposition changes - woven bone
not as strong so subsequently remodelled to lamellar bone
