9 - skeletal muscle, cartilage and bone histology Flashcards
functions of skeletal muscle
- moves and stabilises the skeleton
- forms sphincters in digestive and urinary tracts
- involved in respiration
name 4 characteristics of skeletal muscle
- long, cylindrical cells
- striated
- multiple, peripherally located nuclei
- innervated by somatic nervous system
what is endomysium?
connective tissue layer surrounding a single muscle fibre
what is a fascicle?
bundle of muscle fibres
what is the name given to the connective tissue layer surrounding a fascicle?
perimysium
what is a group of fascicles called?
muscle
what is epimysium?
connective tissue layer surrounding a muscle
describe slow twitch muscle fibres
- type 1
- involved in aerobic respiration
- red — rich myoglobin and mitochondria
- rich blood supply (rich capillary beds)
- generate more ATP for continuous, extended contraction
- fire more slowly
- resist fatigue
describe fast twitch fibres
- type II
- use anaerobic respiration
- good for short bursts of strength or speed
- fatigue quickly
- few mitochondria and little myoglobin
- white — less extensive blood supply
type IIa vs IIb muscle fibres
IIa — intermediate fast twitch, use both aerobic and anaerobic respiration
IIb — use only anaerobic
who is most likely to have type I/II fibres?
I — marathon runners
II — sprinters, jumpers, weight lifters
all the fibres of a single ______ are of the same type
motor unit (an individual motor neuron and all the muscle fibres that it innervates)
what detect fibre length?
sensory stretch receptors = muscle spindle
how does muscle spindle lie in relation to muscle fibres?
in parallel
what does muscle spindle consist of?
- spindle cells — 2 types = nuclear bag fibres and nuclear chain fibres - surrounded by an internal capsule
- internal capsule within fluid filled space surrounded by an external capsule
- sensory nerve endings wrapped around spindle cells — detect stretch
what happens when a muscle fibre is stretched?
receptors stretched — reflex — muscle shortens
what kind of innervation do spindle cells also receive? function?
motor innervation from CNS by gamma neurons — regulates sensitivity of receptor
what are the functions of cartilage?
- framework in resp tract
- shock absorption and facilitation of joint movement
- covers articular surfaces
- development of long bones
cartilage consist of what cartilage cells suspended in an ECM?
- chondrogenic cells — stem cells : differentiate into chondroblasts
- chondroblasts — immature cells
- chondrocytes — mature cells : maintain matrix
most cartilage is surrounded by what?
perichondrium = connective tissue layer
cartilage is ___ so gains nutrients via diffusion
avascular
what are the 3 types of cartilage?
hyaline, elastic and fibrous
what are the 2 types of cartilage growth?
- appositional — occurs just deep to the perichondrium
- interstitial — occurs within actual tissue of cartilage - in areas with no perichondrium. occurs by mitosis of chondrocytes
where is hyaline cartilage found?
= most common form of cartilage in the body
- articulating surfaces, resp tract (nasal septum, larynx, trachea, bronchi), costal cartilages, epiphyseal plates of developing long bones
what are the functions of hyaline cartilage?
- provides structural support for the resp tract
- forms a smooth surface at joints to enable free movement
- involved in the development and growth of long bones
why does the ECM in hyaline cartilage appear smooth and glassy?
because the fibres and ground substance are of similar refractive properties
what type collagen fibres does hyaline cartilage contain?
type II collagen fibres
what are chondrocytes located in in hyaline and elastic cartilage?
lacunae
what does hyaline cartilage possess (except over articular surfaces)?
perichondrium
in hyaline cartilage in areas where interstitial growth is occurring, the chondrocytes appear in clusters termed what?
isogenous groups
territorial vs inter territorial matrix
territorial — surrounds chondrocytes
inter territorial — between chondrocytes
functions of elastic cartilage
provides elasticity and firm support
what does elastic cartilage contain?
type II collagen fibres plus numerous elastic fibres in the matrix
why can elastic cartilage have both appositional and interstitial growth?
possesses a perichondrium
gives examples of elastic cartilage in the body
auricle, epiglottis, corniculate and cuneiform cartilages
where is fibrocartilage located?
where support and tensile strength are required — it is very tough
iv discs, menisci, symphysis pubis
functions of fibrocartilage
- resistant to tearing and compression
- prodigies strength and resilience
located where support and tensile strength are required — it is very tough
what does the matrix of fibrocartilage contain?
type II collagen fires and large bundles of type I collagen fibres
fibrocartilage consists of alternating layers of what?
hyaline cartilage matrix and thick layers of dense collagen fibres
how are chondrocytes arranged in fibrocartilage?
chondrocytes are small and few and arranged in parallel rows along side the fibres
how does growth of fibrocartilage occur and why?
via interstitial growth as no perichondrium
what kind of cartilage is this?
elastic
what kind of cartilage is this?
fibrocartilage
what kind of cartilage is this?
hyaline
what is the organic component of bone? describe
osteoid = glycoproteins ground substance with type 1 collagen fibres
- strong, flexible, but easily compressed
what is the inorganic component of bone? descirbe
mineral salts mainly calcium hydroxyapatite
- hard, relatively inflexible and quite brittle
describe osteoblasts
- produce new bone
- secrete osteoid
- responsible for mineral deposition
- as osteoblasts surround themselves with ECM, they become trapped in their secretion and become osteocytes
describe osteocytes
- mature bone cells
- cannot divide
- located in lacunae within the bone
- maintain the matrix
as the ____ mineralises, the _____ become entombed between the lamellae in ______ where they mature into osteocytes
- osteoid
- osteoblasts
- lacunae
describe osteoclasts
- remove mineral from the matrix
- responsible for bone remodelling
- large and multi nucleated
describe osteogenic stem cells
aka osteoprogenitor cells
- found in periosteum and endosteum
- develop into osteoblasts
bone consists of what 2 types of tissue?
compact bone and cancellous (spongy) bone
why are osteons in compact bone aligned in the same direction?
to increase unidirectional strength
what is in haversian canals in compact bone?
blood vessels
what surrounds the haversian canal?
sheets of bone - concentric lamellae
where are osteocytes in compact bone?
in lacunae between concentric lamellae
osteocytes in compact bone communicate with each other via what?
canaliculi
- continuous resorption and re disposition of compact bone results in new haversian systems being found amongst partially resorped systems
- the remnants of the partially resorbed systems form ________ (between __________)
form interstitial lamellae (between concentric lamellae)
what is the lamellar bone that surrounds the outside of the bone called?
circumferential lamellae
blood vessels from the periosteum enter through ________ and communicate with the vessels in the ______
- enter through Volkmann canals (perpendicular channels)
- haversian canal
trabeculae of cancellous bone is arranged haphazardly to form a network of interconnecting struts designed to provide what?
maximum strength for minimum mass
what do spaces between trabeculae in spongy bone contain?
bone marrow
where do osteocytes in cancellous bone lie?
lie in lacunar near the surface of the trabeculae (instead of between lamellae like in compact bone)
how are trabeculae orientated in cancellous bone?
along the lines of stress
what do yellow and red bone marrow contain?
yellow — adipocytes
red — haematopoietic stem cells
spongy bone contains no ____ or _____ unlike compact bone
Volkmann’s or Haversian canals
a sheet of bone that encircles an osteon is termed a what?
concentric lamellae
fibrocartilage increases size by what?
interstitial growth
